Method and system for disrupting PFAS with 222 nm UV irradiation

Abstract

Methods, systems, and apparatus for disrupting PFAS comprising adding sulfite to an aqueous solution containing PFAS and then irradiating the aqueous solution with light of 222 nm. The method may comprise adding a sufficient amount of a base to the aqueous solution to raise the pH of the aqueous solution comprising PFAS to about 10 or more. It may also comprise the addition of a halide salt (e.g., a bromide salt or iodised salt), and further the addition of a carbonate. By irradiating the aqueous solution in this manner, 90% or more, or 99% or more, of PFAS in the solution can be destroyed.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to the following: U.S. Provisional Application No. 63 / 513,782, filed July 14, 2023, entitled “Procedures for efficient photochemical destruction of PFAS from waste streams”; U.S. Provisional Application No. 63 / 591,040, filed October 17, 2023, entitled “Systems and methods of PFAS destruction”; and U.S. Provisional Application No. 63 / 635,938, filed April 18, 2024, entitled “Pretreatment of PFAS-contaminated water prior to photodeduction”, all disclosures of which are incorporated herein by reference. Background Technology

[0003] Per- and polyfluoroalkyl substances (PFASs) are a class of synthetically prepared compounds that have been used for decades in numerous consumer and industrial applications. PFASs possess unique surface properties and can be both hydrophobic and oleophobic. Therefore, PFASs are used as coating aids, lubricants, foaming agents, and in various surface treatments. They have proven particularly useful as flame retardants in the form of aqueous film-forming foams (AFFFs). Furthermore, some PFASs are known to bioaccumulate in plants and animals. Growing evidence suggests that exposure to PFASs can also lead to various health problems. Given these concerns, regulatory agencies worldwide have begun to establish strict limits on the presence of PFASs in food and water.

[0004] PFASs are a class of chemicals containing perfluoroalkyl or polyfluoroalkyl groups. The definition and classification of PFASs have changed over time. PFASs are fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (without any H / Cl / Br / I atoms attached); that is, with a few known exceptions, any chemical containing at least one perfluorinated methyl group (–CF3) or perfluorinated methylene group (–CF2–) is a PFAS. Some of the most important examples of PFASs include perfluorosulfonic acids (PFSAs), such as perfluorooctane sulfonic acid (PFOS), and perfluorocarboxylic acids (PFCAs), such as perfluorooctane carboxylic acid (PFOA). Fluoropolymers are fluorocarbon-based oligomers or telomers synthesized through telomerization reactions. Certain fluoropolymers and fluoropolymer-based compounds are sources of persistent perfluorocarboxylic acids (such as PFOA) in the environment.

[0005] The persistence, health concerns, and regulatory landscape of PFASs have spurred extensive research efforts to reduce their presence in the environment. Much of the early work focused on capture, for example, from drinking water. However, more recently, efforts have been directed towards the degradation of these materials. One of the properties of PFASs is their resistance to degradation in the environment. PFASs are not readily metabolized by organisms and do not decompose upon exposure to visible light or longer-wavelength UV radiation common in terrestrial environments.

[0006] Some proven methods for decomposing PFASs include supercritical water oxidation (SCWO) and treatment of PFASs in aprotic polar solvents. SCWO achieves treatment by heating water to 374°C under high pressure (over 3000 psi). Therefore, SCWO is extremely energy-intensive and can be plagued by clogging problems. SCWO often requires waste with a high solids content, as it relies on the heat capacity (btu) generated by the waste to make the process economically viable. The advantage of SCWO is its short residence time, ranging from 30 seconds to several minutes, for effective treatment. Using alkaline aprotic media to destroy PFASs presents practical problems: most waste streams are water-based and therefore difficult to transfer to aprotic media requiring minimal water content. In other cases, subcritical water conditions for destroying PFAS compounds in alkaline environments have also been demonstrated. This process (known as hydrothermal alkaline treatment (HALT)) operates at approximately 350°C and approximately 2400 psi.

[0007] Other methods for destroying PFASs involve the use of electrochemical techniques. Electrochemical destruction can destroy long-chain PFASs (such as PFOS and PFOA); however, shorter-chain PFASs are more difficult to destroy. It is speculated that longer-chain PFASs tend to accumulate on the electrode and are therefore more easily oxidized or reduced. Other work has shown that ultrasonic treatment can cause PFAS destruction.

[0008] Processes need to be improved to efficiently and effectively destroy PFAS, especially PFAS in water. Summary of the Invention

[0009] The various embodiments disclosed herein include methods, systems, and apparatus for destroying PFAS by irradiation with 222 nm UV light. For example, some embodiments include a method for destroying PFAS comprising adding sulfite to an aqueous solution containing PFAS and then irradiating the aqueous solution with 222 nm light. The method may also comprise adding a sufficient amount of alkali to the aqueous solution containing PFAS to raise the pH of the aqueous solution containing PFAS to about 10 or higher. The method may also comprise adding a halide salt, such as a bromide or iodide salt, to the aqueous solution containing PFAS. Some embodiments also comprise adding a carbonate to the aqueous solution containing PFAS. The step of irradiating the aqueous solution can destroy more than 90% of the PFAS in the solution, or more than 99% of the PFAS in the solution. In some embodiments, the method further comprises adding persulfate and an acid or alkali to the aqueous solution containing PFAS to raise or lower the pH before irradiating the aqueous solution containing PFAS, and then subjecting the aqueous solution containing PFAS to elevated temperature and pressure for a sufficient duration for thermal oxidation. For example, the temperature increase can be from about 100 to about 140 degrees Celsius, and the pressure increase can be from about 1 to about 5 bar.

[0010] Various embodiments include a photoreactor for PFAS destruction, comprising a reactor vessel and a first light source configured to receive an aqueous solution containing PFAS, the first light source comprising an ultraviolet light source configured to deliver light of approximately 222 nm to the PFAS-containing aqueous solution in the reactor vessel. In some embodiments, the light source may be a krypton / chlorine excimer lamp. The photoreactor may also include a second light source or multiple sources, also positioned to direct light onto the aqueous solution in the reactor vessel, the second light source being the same as the first light source. In some embodiments, the reactor vessel may be a continuous reactor, such as a stirred tank reactor vessel. Some embodiments may also include a source or multiple sources of sulfites and / or halide salts configured to deliver sulfites and / or halide salts upstream of or before entering the reactor vessel or within the reactor vessel. Some embodiments may also include a source of alkali configured to deliver alkali to the aqueous solution upstream of or within the reactor vessel, such that the pH of the aqueous solution within the reactor vessel is approximately 10 or higher.

[0011] Other embodiments include a system for destroying PFAS, comprising a pretreatment reactor including a pretreatment vessel configured to contain an aqueous solution containing PFAS under pressure and including a heating element to heat the aqueous solution contained therein, a source of persulfate and acid or base configured to supply persulfate and acid or base to the aqueous solution before or within the pretreatment vessel, and a photoreactor downstream of the pretreatment reactor. The photoreactor may include: a reactor vessel configured to receive the aqueous solution, multiple ultraviolet light sources configured to supply 222 nm light to the PFAS-containing aqueous solution in the reactor vessel, and a sulfite source configured to supply sulfite to the aqueous solution before or within the reactor vessel.

[0012] Some embodiments include methods, systems, and apparatus for oxidative pretreatment of PFAS-containing aqueous solutions. For example, in some embodiments, the method of destroying PFAS includes oxidatively pretreating an aqueous foam fractionation solution containing PFAS to form a pretreated solution. The step of oxidatively pretreating the aqueous foam fractionation solution includes: mixing the aqueous foam fractionation solution with persulfate and an acid or base to raise or lower the pH, then oxidizing the aqueous foam fractionation solution, and then subjecting the pretreated solution to UV photolysis. UV photolysis may include directing UV light of 222 nm and / or 254 nm and / or 185 nm onto the pretreated aqueous foam fractionation solution. In some embodiments, oxidizing the aqueous foam fractionation solution may include subjecting the aqueous foam fractionation solution to elevated temperature and pressure for a sufficient period of time for thermal oxidation. For example, the elevated temperature may be from about 100 degrees to about 140 degrees Celsius, and / or the elevated pressure may be from about 1 to about 5 bar. In some embodiments, oxidizing the aqueous foam fractionation solution may include ozone oxidation of the aqueous foam fractionation solution. In some embodiments, the method further includes separating solid particles from the aqueous foam fractionation solution before and / or after oxidative pretreatment of the aqueous foam fractionation solution.

[0013] In various other embodiments, the method for destroying PFAS involves mixing an aqueous foam fractionation solution with persulfate and an acid or base to raise or lower the pH, subjecting the aqueous foam fractionation solution to thermal oxidation at a temperature of about 100 to about 140 degrees Celsius and a pressure of about 1 to about 5 bar for a sufficient duration, and subjecting the pretreated solution to UV photolysis at about 222 nm. For example, the persulfate may be potassium persulfate, sodium persulfate, and / or aluminum persulfate. Persulfate may be added to the aqueous foam fractionation solution to achieve a concentration of about 100 to about 200 mM in the aqueous foam fractionation solution. In some embodiments, an acid is mixed into the aqueous fractionation solution to lower the pH of the aqueous foam fractionation solution, for example, to between about 2 and about 4. In other embodiments, a base is mixed into the aqueous foam fractionation solution to raise the pH of the aqueous foam fractionation solution, for example, to between about 10 and about 14.

[0014] Various other embodiments include systems for pretreating PFAS-containing water, comprising a pretreatment reactor including a pretreatment vessel configured to contain PFAS-containing water under pressure, the pretreatment vessel including a heating element to heat the aqueous solution contained therein, and a source of persulfate and an acid or base configured to deliver persulfate and an acid or base to the PFAS-containing water upstream of or within the pretreatment vessel. The system may also include settling tanks upstream or before and / or downstream or after the pretreatment reactor. In some embodiments, the pretreatment reactor may also be a photoreactor and further include a UV light source configured to direct UV light onto the PFAS-containing water after pretreatment. For example, the UV light source may emit UV light with a peak at approximately 222 nm.

[0015] Other embodiments include methods, systems, and apparatus for photoelectrochemical destruction of PFAS. Various embodiments include photoelectrolysis apparatus for destroying PFAS, the apparatus comprising: a photoreactor container configured to receive an aqueous solution containing PFAS; a UV light source configured to direct UV light onto the PFAS-containing aqueous solution within the photoreactor container; a cathode within the photoreactor container and configured to contact the PFAS-containing aqueous solution within the photoreactor container; an anode in an electrolyte solution; a power source configured to provide a voltage difference between the anode and cathode; and a membrane or ion bridge between the anode and cathode. For example, the UV light source may be a mercury lamp with an emission peak of approximately 185 nm and / or 254 nm or a krypton / chlorine excimer lamp with an emission peak of approximately 222 nm. In some embodiments, the UV light source may comprise a UV lamp within a quartz tube immersed in the photoreactor container. For example, the quartz tube may be located at a distance of approximately 2 cm or less from the cathode. In some embodiments, the cathode may be a diamond-doped cathode. In other embodiments, the cathode may be a platinum, titanium, and / or stainless steel electrode. In various embodiments, the cathode may comprise a mesh material. In some embodiments, the cathode may comprise a high surface area structure having an electrochemically active surface and a geometrical surface area, wherein the electrochemically active surface area is greater than the geometrical surface area. In some embodiments, the device may also comprise a source of an inert gas connected to the photoreactor container and configured to bubble an aqueous solution containing PFAS within the reactor container and / or to an anode electrolyte solution. In some embodiments, the photoreactor container may be a continuous reactor, such as a stirred tank reactor.

[0016] Other embodiments include a photoelectrolysis device for destroying PFAS, comprising: a photoreactor container configured to receive an aqueous solution containing PFAS; a UV light source within a tube in the photoreactor container and configured to direct UV light onto the PFAS-containing aqueous solution in the photoreactor container; a cathode within the photoreactor container and configured to contact the PFAS-containing aqueous solution in the photoreactor container, the cathode being located at a distance of approximately 2 cm or less from the UV light source and having a high surface area structure whose electrochemically active surface area is greater than its geometric surface area; an anode in an electrolyte solution; a power source configured to provide a voltage difference between the anode and cathode; and a membrane or ion bridge between the anode and cathode. For example, the UV light source may be a mercury lamp with an emission peak of approximately 185 nm and / or 254 nm or a krypton / chlorine excimer lamp with an emission peak of approximately 222 nm. In some embodiments, the photoreactor container may be a stirred tank reactor.

[0017] Other embodiments include a method for destroying PFAS in a photoelectrolysis apparatus, the method comprising supplying PFAS-containing water to the photoelectrolysis apparatus, the photoelectrolysis apparatus comprising: a photoreactor container configured to receive an aqueous solution containing PFAS, a UV light source, a cathode within the photoreactor container and in contact with the PFAS-containing aqueous solution within the photoreactor container, an anode in a pool containing an aqueous electrolyte, a power source configured to provide a voltage difference between the anode and the cathode, and a membrane or ion bridge located between the anode and the cathode, applying power from the power source to generate a voltage difference between the anode and the cathode, and irradiating the PFAS-containing water within the photoreactor container with UV light. The steps of applying power and irradiating the water may be performed, for example, as simultaneous or overlapping steps. The method may also include continuously flowing the PFAS-containing water through the photoreactor container. The method may include generating hydrogen gas at the cathode. In some embodiments, the method further comprises mixing the PFAS-containing aqueous solution with an electrolyte and causing PFAS destruction without the addition of a sensitizer. In some embodiments, the method further comprises mixing the PFAS-containing aqueous solution with a sensitizer and an electrolyte. In some embodiments, the method further comprises mixing the PFAS-containing aqueous solution with a sulfite and a halide salt. In some embodiments, the method further comprises mixing an aqueous solution containing PFAS with a halide salt and an electrolyte, and applying a voltage between the anode and cathode sufficient to reduce the halogen to the halide. For example, in some methods, the halide is an iodide salt, and the voltage applied between the anode and cathode is sufficient to reduce iodine to iodide. In some embodiments, the method further comprises mixing an aqueous solution containing PFAS with a sulfite and an electrolyte, and applying a voltage between the anode and cathode sufficient to reduce sulfite radical anions or dithiosulfate to sulfite ions.

[0018] Various other embodiments include methods, systems, and apparatus for removing nitrates in improved aqueous systems for destroying PFAS. Various embodiments include methods for destroying PFAS, which involve removing nitrates from PFAS-containing water by combining the PFAS-containing water with a sensitizer and a sufficient amount of alkali to produce a treatment solution having a pH of about 10 or higher, and irradiating the treatment solution with UV light in a photoreactor to destroy a portion of the PFAS. In some embodiments, removing nitrates from PFAS-containing water comprises electrolytically removing nitrates from the PFAS-containing water. For example, in some embodiments, electrolytically removing nitrates comprises electrolytically reducing nitrates to nitrogen and / or ammonia. The method may include contacting the PFAS-containing water with an electrode and applying a current to the electrode. The electrode may be, for example, an iron, copper, or iron:copper electrode. The electrode may be the cathode of an electrolytic cell system that also includes an anode in an aqueous electrolyte solution. In some such embodiments, the method may also include the formation of oxygen at the anode while reducing nitrates at the cathode. In various other embodiments, removing nitrates from PFAS-containing water may include filtration through a selective membrane. Examples of selective membranes that can be used include reverse osmosis, forward osmosis, nanofiltration (NF), and / or ultrafiltration (UF). In various embodiments, nitrate removal from water containing PFAS is a pretreatment step prior to irradiating the treatment solution. In other various embodiments, nitrate removal from water containing PFAS is a step that occurs within the photoreactor.

[0019] Various embodiments include methods for destroying PFAS, which include contacting PFAS-containing water with a cathode, applying an electric current to the cathode to electrolytically reduce nitrates in the PFAS-containing water, combining the PFAS-containing water with sulfites and halide salts and a sufficient amount of alkali to produce a treatment solution with a pH of about 10 or higher, and irradiating the treatment solution with UV light in a photoreactor to destroy some of the PFAS. In some embodiments, the halide salt may be an iodide, and the UV light may be light with an emission peak approximately 222 nm. In some embodiments, the method further includes oxidatively pretreating the PFAS-containing water prior to PFAS irradiation. In some such embodiments, oxidatively pretreating the PFAS-containing water comprises mixing the PFAS-containing water with persulfate and an acid or alkali, and then subjecting the water to elevated temperature and pressure.

[0020] Various embodiments include systems for destroying PFAS in water, comprising a nitrate removal system configured to remove nitrate from water containing PFAS and nitrate, the nitrate removal system comprising a selective membrane and / or electrolytic cell system and a photoreactor comprising a reactor vessel configured to contain an aqueous solution and a source of ultraviolet light positioned to direct light onto the contents of the reactor vessel. In some embodiments, the nitrate removal system may be located upstream of the photoreactor. In some embodiments, the nitrate removal system is an electrolytic cell system comprising a first cell containing a cathode configured to contact the PFAS-containing water in the first cell, a second cell including an anode in an electrolyte, a power source, and salt brine and / or a membrane separating the first and second cells. In some embodiments, the cathode is located within the photoreactor, and the photoreactor vessel forms a container for the first cell. In various embodiments, for example, the cathode may comprise iron, copper, and / or iron:copper.

[0021] Other embodiments include methods, systems, and apparatus for capturing iodine from aqueous solutions. Various embodiments include methods for removing iodides from aqueous solutions, comprising immersing a iodophilic electrode in an aqueous solution containing iodide, applying a current to the electrode, and electrochemically oxidizing the iodide to iodine within the electrode. The method may also include adjusting the pH of the aqueous solution to between about 3 and about 8. In some embodiments, the current-applying step generates a voltage of 0.3 V or higher relative to Ag / AgCl. In various embodiments, the iodophilic electrode comprises an iodophilic material and a conductive material. For example, the iodophilic material may be cellulose, starch, cationic polymers, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), metallocene, metallocene-containing polymers, and / or cationic metal complexes. In some embodiments, the iodophilic electrode may also comprise a binding agent material. In some embodiments, the iodophilic material may comprise starch, chitosan, or carboxycellulose. In some embodiments, the iodophilic material may be a cationic polymer. In some embodiments, the iodophilic material may be an anion-exchange membrane. In some embodiments, the conductive material may comprise graphite, graphene, carbon nanotubes, conductive polymers, or doped semiconductors and / or metals. In some embodiments, the binder may comprise polyvinylidene fluoride (PVDF), polyvinyl fluoride (PTFE), styrene-butadiene rubber, and / or polyamide. In some embodiments, the aqueous solution may be water that has been photolyzed by UV to destroy PFAS. In some such embodiments, the method may further comprise removing the electrode from the aqueous solution, immersing the electrode in a second solution, applying a current to the electrode to reduce iodine, and releasing it from the electrode as an iodide into the second solution.

[0022] Other embodiments include a method for capturing and recycling iodide from a photochemical advanced reduction process (ARP) solution. The method includes receiving a photochemical ARP solution produced by the ARP process, adjusting the pH of the photochemical ARP solution to between approximately 4 and approximately 8, then contacting the ARP solution with an ion exchange medium for a sufficient duration to allow the ion exchange medium to bind iodide, and then contacting the ion exchange medium with an aqueous salt solution to remove the bound iodide. In some embodiments, the ion exchange medium contains quaternary ammonium groups. In some embodiments, the aqueous salt solution contains water and a mixture of sodium chloride, sodium bromide, potassium chloride, potassium bromide, sodium hydroxide, potassium hydroxide, sodium sulfate, and / or potassium sulfate. In some embodiments, the ion exchange medium is a strong anion exchange medium.

[0023] Other embodiments include systems for recovering and reusing iodine from aqueous solutions, the systems comprising iodophilic electrodes comprising iodophilic materials, conductive materials, binders, and current collectors, wherein the electrode is connected to the current collector. In some such embodiments, the iodophilic materials comprise cellulose, starch, cationic polymers, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), metallocenes, metallocene-containing polymers, and / or cationic metal complexes. In some embodiments, the conductive materials comprise graphite, graphene, carbon nanotubes, conductive polymers, and / or doped semiconductors or metals. In some embodiments, the binders comprise polyvinylidene fluoride (PVDF), polyvinyl fluoride (PTFE), styrene-butadiene rubber, and / or polyamides.

[0024] Other embodiments include methods, systems, and apparatus for recycling materials during PFAS destruction. Various embodiments include methods for destroying PFAS, comprising: a) feeding PFAS-containing water into a reactor vessel; b) irradiating the water within the reactor vessel with UV light under specific conditions to destroy at least a portion of the PFAS to form treated water; c) passing the treated water through a selective membrane to form permeate and a membrane rejectant comprising PFAS; d) providing the membrane rejectant back to the reactor vessel; e) providing additional PFAS-containing water to the reactor vessel, wherein the membrane rejectant binds to the additional PFAS-containing water within the reactor vessel or before being provided to the reactor vessel; and f) irradiating the membrane rejectant and the additional PFAS-containing water within the reactor vessel with UV light. The method may further comprise repeating these steps multiple times such that any undestroyed PFAS is recycled through the reactor vessel. In some embodiments, the method further comprises adding a sensitizer to the PFAS-containing water prior to step b). In some such embodiments, the membrane rejectant also comprises a sensitizer. In some such embodiments, the selective membrane may be a reverse osmosis or nanofiltration membrane. For example, in some such embodiments, the selective membrane rejects at least about 99% of the PFAS and sensitizer. In some embodiments, the method further includes adding additional sensitizer to additional water or membrane rejectant containing PFAS prior to step f). In various embodiments, the sensitizer comprises, for example, a halide salt (e.g., an iodide). In some embodiments, the method further includes removing sulfate from the membrane rejectant prior to step d). For example, sulfate removal comprises adding calcium to the membrane rejectant to form a sulfate precipitate and separating the sulfate precipitate from the membrane rejectant. In some embodiments, the method further includes passing the membrane rejectant through a water softener prior to step d to remove calcium, magnesium, and / or iron.

[0025] Various embodiments include a method for destroying PFAS, the method comprising: a) providing PFAS-containing water to a reactor vessel; b) adding sulfite and halide salts to the PFAS-containing water prior to step a) or within the reactor vessel to form a reaction solution; c) irradiating the reaction solution within the reactor vessel with UV light under specific conditions to form a treated solution; d) passing the treated solution through a selective membrane to form permeate and a membrane repellent comprising residual PFAS and halide salts, wherein the selective membrane repelles approximately 99% or more of the residual PFAS and halide salts present in the treated solution; and e) providing the membrane repellent to the reactor vessel or to a separate reactor vessel. The method may further comprise discharging the permeate into the environment. In some embodiments, these steps may be performed continuously.

[0026] Other embodiments include a system for destroying PFAS, comprising: a photoreactor including a reactor vessel configured to receive water containing PFAS; a UV light source configured to direct UV light onto the PFAS-containing water within the reactor vessel; a selective membrane in fluid communication with the photoreactor and located downstream or after the photoreactor, the selective membrane being selective for more than 99% of the PFAS present in the PFAS-containing water after hydrolysis in the photoreactor; and means for transporting a membrane rejectant stream formed by the selective membrane to a location upstream of the photoreactor for further transport to the photoreactor or direct transport to the photoreactor. For example, the selective membrane may be a reverse osmosis or nanofiltration membrane. The system may also include a sedimentation system connected in series downstream of the selective membrane along the outflow of the membrane rejectant, prior to transport of the membrane rejectant to the photoreactor. In some embodiments, the system may further include a water softener downstream of the sedimentation system or after the sedimentation system and prior to transport of the membrane rejectant to the photoreactor. In various embodiments, the reactor vessel may be a continuous reactor. Attached Figure Description

[0027] The following figures are illustrative of embodiments and are intended to, but do not limit, the scope of the invention. The figures are not necessarily drawn to scale and are intended to be used in conjunction with the following detailed description. Embodiments of the invention will be described with reference to the figures, wherein like numbers may represent like elements.

[0028] Figure 1 These are schematic diagrams of examples of integrated systems according to different embodiments, which integrate preprocessing, photolysis, and post-processing. Figure 2 These are schematic diagrams of electrolytic cells according to different embodiments; Figure 3 These are schematic diagrams of electrolytic cells for nitrate reduction according to different embodiments; Figure 4 This is a schematic diagram of a method integrating filtering and light destruction according to various embodiments; Figure 5 This is a flowchart of the process of destroying PFAS in wastewater flow; Figure 6 It is a flowchart of a process that includes thermal oxidation pretreatment to destroy PFAS in the wastewater stream; Figure 7 It is a flowchart that includes ozone oxidation to destroy PFAS in wastewater flow; Figure 8 This is a depiction of an example of a UV reactor as the photochemical component of a treatment system; Figure 9 These are schematic diagrams of alternative embodiments of the photoelectrolysis cell according to various embodiments; Figure 10These are examples of the chemical structures of polymers that can be used in various embodiments; Figure 11 These are other examples of the chemical structures of polymers that can be used in various embodiments; Figure 12 Examples of polymer n-type organic semiconductor structures that can be used in various embodiments are shown; Figure 13 This is a drawing illustrating examples of disodium salt oxidation attached to a polymer according to various embodiments; Figure 14 These are examples of polymer chemical structures that can be used in various embodiments; Figure 15 Examples of chemical structures of polymers with oxidizable units that can be used in various embodiments; Figure 16 This is an example diagram depicting a system for the electrochemical regeneration of iodides reduced from iodine or iodine radicals; Figure 17 These are illustrations of examples of electrochemical regeneration of iodide oxides according to various embodiments; Figure 18 This is a depiction of another example of electrochemical regeneration of iodide oxide according to various embodiments; Figure 19 It is a drawing based on various embodiments of using an electrochemical system to change the local pH of a solution; Figure 20 This is a schematic diagram of an example of a system for photoelectrolysis of 185 mm irradiation accompanying hydrogen evolution, according to various embodiments; Figure 21 The reaction caused by water absorbing 185 nm light is described; Figure 22 This is a schematic diagram of a non-electrochemical system for iodine reduction according to various embodiments; Figure 23 It is a drawing of the chemical structure of polyvinyl ferrocene that can be used in various embodiments; Figure 24 It is a drawing of the chemical structure of polymers having tetramethylpiperidine-1-oxy (TEMPO) side chains that can be used in various embodiments; Figure 25 This is an example of a process that involves the destruction of PFAS using aromatic compounds; Figure 26 This is a schematic diagram illustrating an example of the post-processing procedure; Figure 27 This is an example of an electrolytic battery used for recycling iodides; Figure 28 This is a diagram illustrating an example of the PFAS processing method, following the completion of subsequent processing steps and the refinement steps. Figure 29This is a graph showing the percentage of total PFAS defluorination in examples with / without an electrochemical nitrate reduction prestep; Figure 30 The example shows NO3, which is a membrane rejectant with RO and NFX. - A graph showing how concentration (ppm) varies with concentration factor; Figure 31 This is a comparison chart of the percentage of defluorination due to photoreduction of membrane rejectants from RO and NFX membranes.

[0029] Figure 32 These are a series of photographs of wastewater during the destruction of PFAS, which includes thermal oxidation pretreatment. Figure 33 These are UV transmittance spectra of the original wastewater and the wastewater after thermal oxidation treatment and dilution with DI water at 0, 2, 5 and 10 times. Figure 34 is a series of graphs showing the percentage of total PFAS destruction in wastewater samples after thermal oxidation pretreatment under varying dilution factors via UV222 and UV254 photoreduction processes. Figure 35 A series of photographs of wastewater during the destruction of PFAS, including ozone oxidation pretreatment. Figure 36 These are a pair of graphs showing the percentage of total PFAS destruction relative to time after ozone oxidation of samples via UV222 and UV254 photoreduction processes at dilution factors of 10x and 5x.

[0030] Figure 37 This is a pair of bar graphs showing the results of PFAS destruction after pretreatment with UV222 nm and UV254 nm photoreduction treatment following thermal oxidation or ozone oxidation pretreatment. Figure 38 The images show photographs of wastewater samples subjected to thermal oxidation with varying doses of potassium persulfate and sodium hydroxide; and... Figure 39 This is a bar chart showing the destruction of PFAS in wastewater using photoreduction and photosensitizers at different concentration levels.

[0031] Figure 40 This is a graph showing the concentration of PFAS solution reduced by 222 nm light over time for six different solutions; Figure 41 This is a graph showing the percentage of PFAS destruction in PFAS solutions reduced by 222 nm light over time for six different solutions; Figure 42 This is a graph showing the percentage of PFAS destruction over time, comparing reduction with 222 nm light with direct irradiation. Figure 43This is a graph showing the change over time of data fitted to a single exponential function using 1 mM KI, 5 mM Na2SO3 and bicarbonate solutions to destroy PFAS. Figure 44 The graph shows the time-dependent degradation of PFOA during photolysis at 222 nm using 5 mM Na2SO3 and 150 mM KBr or only 5 mM Na2SO3. Figure 45 The graph shows the change in fluoride ion concentration over time during photolysis at 222 nm using 5 mM Na₂SO₃ and 150 mM KBr, or 5 mM Na₂SO₃ alone; and... Figure 46 This is a graph showing the changes in PFAS destruction and PFAS concentration relative to time when foam fractionated water samples were subjected to UV destruction at 222 nm and 254 nm.

[0032] Figure 47 This is a graph showing the experimental results of recycling iodides by electrochemically reducing photochemically generated iodine free radicals without using sulfites.

[0033] Figure 48 This is a diagram showing how hydrogen gas generated by electrochemistry destroys PFOS.

[0034] Figure 49 shows a graph of experimental results for linear sweep voltammetry of oxidizing (left) and reducing (right) properties using an iodide recovery and reuse electrode.

[0035] Figure 50 The figure shows the experimental results of total iodide removal and recycling using an iodide recovery and reuse electrode. Detailed Implementation

[0036] The systems and methods described herein relate to processes for the photochemical destruction of PFASs. More specifically, these systems and methods involve a class of UV photochemical destruction known as UV-ARP (UV-based advanced reduction processes). The UV-ARP method is based on the generation of highly reducing species (e.g., solvated electrons) produced by irradiating a photosensitizer. This photosensitizer or sensitizer absorbs UV energy and generates solvated electrons and oxidized sensitizer species. The solvated electrons can then react with PFAS molecules.

[0037] Various embodiments include processes for improving the efficiency of photochemical destruction of PFAS and allowing for broader application of photochemical methods to various types of PFAS-containing waste streams. Other embodiments include the design of UV photolysis reactors to more efficiently destroy PFASs. Still other embodiments include systems and methods for recycling high-value materials after UV photolysis of PFAS materials. Other embodiments include systems and methods for additional treatment of waste streams after UV photolysis and before discharge into the environment or reuse in industrial applications.

[0038] Various embodiments involve photochemical destruction of PFASs as a method of destroying so-called "permanent chemicals." In some embodiments, the photochemical system includes a reactor vessel with one or more UV light sources. The reactor may be filled with a liquid consisting of one or more of the following: PFAS, water (or another solvent), and a sensitizer that absorbs UV light and generates reactive species. Optionally, one or more other chemical additives may also be included to facilitate the reaction. The processes, systems, and methods disclosed herein result in improved efficiency, lower costs, and reduced chemical usage. In some embodiments, materials used in the process can be recycled and reused, further improving efficiency and reducing costs. Another embodiment involves treating the photolysis solution so that it can be recycled, further purified, or disposed of.

[0039] Various embodiments include the use of ultraviolet light-based advanced reduction processes (UV-ARP), which can effectively treat several classes of stubborn chemical contaminants in water. Advanced reduction processes are based on the generation of highly reducing hydrated electrons that exhibit rapid bimolecular reaction rate constants with inorganic and organic compounds. In UV-ARP, solvation electrons can be generated by illuminating a sensitizer capable of generating solvation electrons when irradiated with a UV light source. The photogenerated solvation electrons generated by the systems and methods described herein can react with PFASs and other contaminants, leading to the destruction of PFASs.

[0040] UV-ARP results in the mineralization of PFAS by converting carbon-fluorine bonds into fluoride ions and carbon species (such as acetates, formates, carbon dioxide, shorter-chain PFAS molecules, other polyfluorides, and / or carbonates). In this context, mineralization refers to the reduction of carbon-bonded fluorine in PFAS to fluoride ions (F). - .

[0041] In some embodiments, the UV-ARP method can be used directly, for example, in a high-throughput treatment system to treat PFAS present in wastewater or other water sources. In other embodiments, the UV-ARP method can be used to treat PFAS extracted, adsorbed, separated, and / or concentrated from the environment (e.g., from wastewater or other water sources). PFAS can be suspended or dissolved in an aqueous solution for use in the UV-ARP methods and systems described herein.

[0042] The methods and systems described herein for destroying PFAS include the ability to destroy PFAS contaminants comprising carboxylated and sulfonated PFAS contaminants. Examples of PFAS that can be destroyed by the embodiments described herein include, but are not limited to, trifluoroacetic acid (TFA), perfluorobutyric acid (PFBA), perfluorovalerate (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS). Using the photoreactive methods described herein, more than one type of PFAS can be treated and destroyed simultaneously.

[0043] The destruction of PFAS involves altering the nature of the target chemical pollutant through the breaking of chemical bonds. Destruction that produces complex chemical compounds as the final product is called degradation. Destruction involves removing one or more chemical groups to reduce or eliminate toxicity.

[0044] The PFAS used in the various embodiments may be in the form of an aqueous solution, such as PFAS present in water from contaminated natural or other sources, or may be concentrated by pre-capture or pretreatment methods or other treatment methods.

[0045] Some embodiments include an electrochemical system to convert photochemical byproducts back into the original sensitizer and prevent the accumulation of high concentrations of species that remove solvated electrons.

[0046] Compared to other pollutants, the processes that destroy PFASs are relatively fewer. Since photolysis generates solvated electrons, minimizing potential interference with the photochemical process is advantageous. Therefore, in some cases, it may be ideal to pretreat the waste stream using other processes to allow the photolysis reaction to proceed at its highest efficiency. Furthermore, photolysis reactions that efficiently generate solvated electrons may require very strong alkaline conditions, such as pH above 10 or 12. Additionally, other inorganic salts can be added to remove photolysis products and minimize the concentration of molecular oxygen. Therefore, the concentration of inorganic ions can be quite high. The destruction of PFASs also generates inorganic fluoride anions (F... -Therefore, for the disposal of waste streams after photolysis, it is likely desirable to reduce the concentration of potentially corrosive species or other unwanted species. Furthermore, although photolysis can remove over 90%, and often more than 99%, of PFASs, it is still advantageous to use other separation technologies to further reduce PFAS concentrations, such as to meet regulatory restrictions or shorten reactor time. The presence of competing ionic species can negatively impact many processes used to further reduce PFAS concentrations, such as ion exchange technologies, reverse osmosis, or granular activated carbon (GAC) beds. Therefore, reducing ion loading to effectively deploy these technologies may also be advantageous.

[0047] For at least these reasons, an effective system for photochemical destruction of PFAS can consist of the following steps: pretreatment, then photolysis, then posttreatment, and then optional sizing. Each of these steps can be employed in various combinations using different systems and methods. While all steps may be used in many cases, in other cases the system of the method may not include all of these steps. Furthermore, the system and embodiments may further include means of fluid delivery, comprising pipes, pumps, valves, inlets, outlets, etc., thereby connecting and connecting to the inlets and outlets of the components and from the inlets and outlets of the components. Figure 1 An example of an integrated system that incorporates preprocessing, photolysis, and preprocessing is shown.

[0048] Preprocessing step

[0049] Various embodiments successfully implement UV-ARP by minimizing the photochemical degradation time of PFAS and minimizing reagent costs, including the use of pretreatment.

[0050] PFASs are found in many waste streams. Some common PFAS-containing waste streams that can be treated according to various embodiments include effluents from PFAS industrial producers, effluents from textile mills, foam fractionation concentrates, aqueous film-forming foams (AFFFs), AFFF rinsates, landfill leachate, contaminated groundwater, municipal waste water streams, and pot still bottoms. Some of these waste streams may be suitable for simple pretreatment procedures such as filtration. Other waste streams may require unique pretreatment, such as removal of solvated electron scavengers, scattering materials, or UV absorbers. In some cases (e.g., when the composition of the waste stream is known and the properties of non-PFAS species are understood), pretreatment steps may be omitted. One or more pretreatment systems and methods described herein can be used in various embodiments.

[0051] Solvated electrons react with a variety of naturally occurring chemical species in water. Any photochemical system that uses solvated electrons to react with PFASs may be sensitive to other chemical species in the waste stream. These other chemical species may remove the solvated electrons. In fact, many common chemical contaminants react with solvated electrons faster than PFASs. Depending on the concentration and nature of these chemical species, solvated electrons may preferentially react with them until they are consumed. This can result in a significantly longer reaction time that destroys PFASs.

[0052] Therefore, in various embodiments, these contaminants may preferably be consumed before the target PFAS. In some cases, the contaminant concentration is high enough that PFAS destruction cannot occur, or it occurs very slowly (e.g., over several days or weeks). Nitrates are a common example of contaminants in wastewater that readily react with solvated electrons and reduce UV efficiency. Nitrates may interfere with the photochemical destruction of PFASs for two reasons: 1) nitrates are highly efficient electron scavengers, and 2) nitrates have strong light absorption in the UV portion of the electromagnetic spectrum. Given that UV photolysis is one of the processes that can destroy PFASs under ambient temperature conditions, and that other contaminants can be efficiently removed by other processes, a pretreatment step can be used to remove these contaminants.

[0053] The various embodiments disclosed herein encompass systems and methods for oxidative pretreatment of PFAS-containing waste streams prior to UV photoreduction. The pretreatment process may include an oxidative process involving thermal oxidation and / or ozone oxidation. In some embodiments, thermal oxidation may involve mixing wastewater with a persulfate (e.g., potassium persulfate or sodium persulfate) and an alkali or acid to raise or lower the pH of the wastewater, and treating the wastewater under elevated temperature and / or pressure. In some embodiments, ozone treatment involves mixing wastewater with an alkali to raise the pH of the wastewater, followed by ozone treatment. Following pretreatment, UV photoreduction of the wastewater may be more efficient, resulting in a higher percentage reduction in PFAS achieved after photoreduction. For example, the thermal oxidation treatment disclosed herein makes PFAS destruction by 222 nm UV light reduction more efficient, significantly reduces dilution requirements, and thus makes the photoreduction process more efficient and cost-effective.

[0054] Pretreatment is advantageous because, in addition to the PFAS target of UV photoreduction, waste streams may contain other components that inhibit or interfere with photoreduction. Some of these components may interfere with light transmission, reducing the effectiveness of the UV-based PFAS destruction process. Others may interfere with the chemical reactions that occur during UV photoreduction. Various embodiments include methods to reduce or eliminate the presence of these components, thereby achieving more efficient subsequent PFAS photoreduction. The pretreatment process described herein removes solvated electron scavengers, scattering materials, and / or UV absorbers. This process and system improve the photochemical destruction efficiency of PFAS, allowing for a wider range of photochemical methods for various types of PFAS-containing waste streams, and reducing the time and cost required to destroy PFAS.

[0055] Pretreatment enhances light transmittance, allowing UV light to penetrate the wastewater more fully. Simultaneously, pretreatment does not interact with PFAS species or remove them from the aqueous components of the wastewater. In this way, the PFAS components in the wastewater are not separated during pretreatment, which would require treating not only the liquid components of the wastewater but also the PFAS separated from them, increasing complexity and cost. Pretreatment is not expected to cause defluorination of PFAS, but it may change PFAS (e.g., telomers) into another type of PFAS that is more easily photoreducible. However, the primary purpose of pretreatment is to interact with, change, or remove non-PFAS components from the waste stream, which could otherwise interfere with subsequent UV reduction. Furthermore, pretreatment does not generate chemical products that interfere with or reduce the efficiency of the UV photoreduction process. The pretreatment disclosed herein yields a waste stream more suitable for UV photoreduction and is more efficient due to increased light transmittance, the elimination of PFAS separation, and the absence of interfering substances.

[0056] The challenges of successfully implementing UV photoreduction of PFAS in wastewater include maximizing destructive performance, minimizing photochemical destruction time, and minimizing reagent costs. The pretreatment disclosed in this paper achieves more efficient UV photoreduction with less dilution of the waste stream. Consequently, the process requires a smaller volume and less reagent overall.

[0057] Another problem with using UV-ARP is that the cost of the sensitizer tends to account for a major portion of the material's cost. Therefore, a practical and efficient method for recycling and reusing the sensitizer or sensitizer precursor is desired.

[0058] In some cases, the composition of the waste stream is well understood, and steps can be taken to reduce potential scavenging agents. This may be the case for industrial waste streams where the reactants and products are known. In other cases, various embodiments can be characterized, for example, by one or more analytical techniques (e.g., mass spectrometry, gas chromatography-mass spectrometry, multinuclear NMR, infrared spectroscopy, and / or UV absorption spectroscopy). The determination of concentration and chemical composition allows for the treatment of the waste stream prior to UV photolysis. Pretreatment of the waste stream prior to UV photolysis results in a significant reduction in the time required to destroy PFASs.

[0059] In some embodiments, the treatment may occur as an intermediate step between several photoreactors in series. For example, photolysis may be carried out in a first reactor. The waste stream may then be further treated in a second reactor (or one or more additional reactors in series) that may employ different treatment conditions than those in the first reactor (e.g., different wavelengths of light, sensitizers, pH, temperature, etc.).

[0060] In some embodiments, several pretreatment steps may be performed prior to the photolysis process. For example, a sorting step may be used between the pretreatment and photolysis processes, which allows solids to settle and separate from the wastewater.

[0061] Various techniques can be employed to remove contaminants that remove active photochemical species. For example, nitrates and nitrites can be particularly troublesome impurities in UV-ARP and may be reduced or removed prior to UV treatment in various embodiments. Other water impurities that also remove solvated electrons, and water impurities that can be removed by pretreatment in various embodiments, include, but are not limited to, the following: 1) organic impurities, such as chlorinated organic compounds (COCs), including: chlorobiphenyls, chlorodibenzo-p-dioxins, chloroform, tetrachloroethylene, and other chlorinated solvents and washing fluids; 2) halogen oxides: OCl - ClO2 - ClO3 - ClO4 - ,OBr - BrO2 - BrO3 - BrO4 - IO - IO2 - IO3 - IO4 - Or their corresponding conjugate acids.

[0062] One approach to managing impurities that interfere with UV treatment is to consume them as part of the ARP (Activated Particulate Reduction). In this case, for example, with nitrates, the impurities may be consumed before PFAS destruction occurs during the induction period. However, some wastewater is contaminated with impurities such as nitrates at extremely high concentrations, for example, near water sources associated with intensive agricultural activities. In such cases, nitrate levels may exceed 400 mg / L (400 ppm). It is uncommon to further concentrate these wastewaters to levels of 20,000 ppm or higher using other techniques, such as reverse osmosis or solvent extraction of adsorption media (e.g., in distillation bottoms). In PFAS samples with these nitrate levels, PFAS destruction is not only delayed but also ineffective (below 5% after a 24-hour UV photolysis period). In such cases, alternative pretreatment methods, such as those described herein, may be particularly useful.

[0063] In various embodiments incorporating a catalytic system, the catalyst may be placed on a support and configured to allow the water to be treated to flow through the catalyst and the support. For example, using a noble metal as a catalyst to reduce nitrate with hydrogen can produce NH4+. + The generation of . Furthermore, when hydrogen is used, t, H + As a byproduct, this can lead to a decrease in the pH of the system. Therefore, in various embodiments, a base may be added to compensate for these changes.

[0064] In some embodiments, hydrogen can be used as a reducing agent. For example, hydrogen can be bubbled to generate it in solution or electrochemically and used in conjunction with the catalytic system described above as a pretreatment that can be used to remove non-PFAS contaminants. Various embodiments may include a single-metal system, while other embodiments may include a bimetallic catalyst for selective reduction. Examples of bimetallic catalysts that can be used in various embodiments include a first metal such as a noble metal (e.g., Pd or Pt) and a second metal (promoter metal) such as Cu, Sn, or In. Although combinations of bimetallic catalysts may also be used, such as Rh, Ru, or Ir, and the second metal (promoter metal) is Ni, Ag, Zn, or Fe.

[0065] Halogen oxides (such as bromates) can also be catalytically reduced by many metals supported on activated carbon (including Pd, Pt, Ir, Rh, Ru, Fe, Sn, Cu, Zu, and Ni) and hydrogen at room temperature and chamber pressure. All of these catalysts are active in the conversion of bromates to bromides. Ruthenium, palladium, platinum, and rhodium are the most efficient; platinum exhibits the highest activity. Halogen oxides can also be reduced electrochemically. Organometallic rhenium catalysts deposited on reactive electrochemical films on Ti4O7 can be used to reduce aqueous ClO4... – Electrocatalytic reduction to Cl –This is effective. Sulfite ions can also reduce the amount of halogen oxides, reducing them to harmless species such as halides.

[0066] Electrochemical pretreatment. In some embodiments, electrochemistry can be used to pretreat the waste stream. Since electrochemistry can only break down longer-chain PFASs (e.g., PFOS or PFOA), it may not be a solution for destroying all PFASs. However, in various embodiments, electrochemistry can be used as a pretreatment step to partially react the PFASs into a form that is easier or more readily processed by subsequent UV-ARP processes. In this regard, for example, pre-reacting various telomers can significantly reduce photolysis time and maximize the efficiency of the process.

[0067] Nitrate Pretreatment. Various embodiments involve pretreating waste streams to remove nitrates and nitrites. One or more methods that can be used include chemical reduction, ion exchange membranes, electrodialysis, electrochemical reduction, photochemical reduction, and bioremediation in which nitrates or nitrites are degraded by organisms. While any of these methods may be effective in principle, a key consideration is minimizing the formation of potential byproducts that could efficiently remove electrons, such as other nitrogen oxides, or those products that have absorption transitions in the UV that may reduce the amount of light that the sensitizer can absorb. If the concentration of potentially interfering chemical species has been determined, chemicals can be added that transform these contaminants into materials that do not react with or are not readily reactive with solvated electrons.

[0068] In some embodiments, pretreatment to reduce or remove nitrates may include reducing nitrates to molecular nitrogen or ammonia. For example, in acidic solutions, as a pretreatment, nitrates may be reduced, for example, by formic acid, iron metal or zero-valent iron, aluminum-iron alloys, methanol, and ammonium ions. In alkaline solutions, nitrates may be chemically reduced by, but not limited to, aluminum powder, zinc and iron metal or zero-valent iron, Fe... 2+ Pretreatment of the components, including ammonia, hydrazine, glucose, hydrogen, and thiosulfate. In some embodiments, a suitable catalyst may be used to help accelerate these reactions. Examples of suitable catalysts that may be used in various embodiments include palladium / carbon.

[0069] In some embodiments, photochemical processes can be utilized alone or in combination with pretreatment to reduce nitrates. For example, in some cases, the addition of inorganic photocatalysts (such as titanium dioxide, iron, or manganese) can be used in a photoreactor to selectively reduce and remove nitrates and nitrites prior to the addition of hydrated electron-generating species for PFAS reduction. In other embodiments, organic acids or bases (including, but not limited to, oxalic acid and / or formic acid) can be added to the photochemical reactor and treated under UV light as a means of nitrate removal. Inorganic and organic photocatalysts can be used in separate UV reactors or in combination with the same UV reactor used for PFAS reduction.

[0070] Some embodiments may use electrochemical processes to reduce nitrates and other contaminants to treat nitrates or nitrites in water. For example, these methods may use a system comprising three components: 1) a cathode where a reduction reaction occurs, 2) an anode where an oxidation reaction occurs, and 3) an electrolyte solution capable of supporting ion transport.

[0071] Various embodiments may involve the electrochemical reduction of nitrates to nitrogen gas and may involve several reactions, products, and intermediates (e.g., ammonia, nitrite, hydrazine, hydroxylamine, nitric oxide, and nitrous oxide). However, under standard conditions, N2 and NH3 / NH4 + Nitrate is the thermodynamically stable form of nitrogen. The electrochemical reduction of nitrate according to various embodiments can be described by the following reaction: 2 NO3 - + 12H + +10 e - à N2 + 6H2O E 0 = 1.17 V / SHE NO3 - + 9 H + + 8 e - à NH3 + 3H2O E 0 = -0.12 V / SHE Both of the above reactions are multi-electron transfer processes. The final products of the electrochemical reduction of nitrates can be determined by altering or adjusting various factors, such as electrode materials or crystal facets. For example, various embodiments may employ catalysts and / or electrode materials, or other selected conditions, to generate molecular nitrogen as the reaction product.

[0072] In some embodiments, the electrochemical reduction of nitrogen may involve a single-metal catalyst using noble metals (e.g., Ru, Rh, Pd, Ag, Pt, Au, etc.) and / or first-row transition metal systems. For example, some first-row transition metal systems used in various embodiments exhibit high catalytic selectivity, efficient removal, and low cost for the electrochemical reduction of nitrates, including iron or copper metal foams, copper nanosheets, copper-supported 3,4,5,9-perylenetetracarboxylic anhydride, cobalt nanoarrays, etc. In some embodiments, a two-component metal catalyst system may be used, such as Pt-based and Pd-based catalysts modified by introducing modified metals (Sn, Cu, Bi, and Ge) onto the electrode surface, potentially resulting in higher nitrate reduction activity. Other two-metal catalysts used in various embodiments include Cu / Fe systems, carbon-supported Pt... 78 Ru 22 Cu 50 Ni 50 In other embodiments, the electrochemical reduction of nitrates may involve the use of metal oxide catalysts, such as Co3O4-supported NiO porous nanoplatelets, nanotube heterostructures of Co / CoO nanosheet arrays with Schottky interfaces supported on nickel foam, Cu / Cu2O nanowire arrays, TiO2, etc. 2-x Or TiO2.

[0073] In some embodiments, electrochemistry may be used as a pretreatment to reduce nitrates using an iron cathode. For example, in various embodiments, the electrode may be used under a constant reduction bias to limit the dissolution of Fe that could lead to electrode corrosion. 2+ or Fe 3+ The formation of nitrates can be achieved by altering the solution, for example by adding a base or maintaining it in an alkaline range, such as a pH range of about 10 or higher, or about 10 to about 12, to limit iron dissolution that may occur under acidic conditions. A voltage in the range of -1.0 to -1.5 V (relative to Ag / AgCl) can be applied to the iron electrode. Higher voltages can be used, but they may cause a decrease in the selectivity of nitrate reduction due to the increased water reduction. Electrolysis should continue until the desired nitrate concentration is reached.

[0074] In some embodiments, electrochemistry can be performed as a pretreatment using a copper cathode to reduce nitrates. For example, in various embodiments, the electrode can be used under a constant reduction bias to limit the dissolution of Cu that could lead to electrode corrosion. + or Cu 2 +The formation of nitrates can occur. For example, the solution can be altered or maintained in a pH range of about 2 to about 12. In various embodiments, the pH can be altered, for example by adding acid, or maintained in an acidic range, for example below about 4 or between about 2 and about 4, because ammonia is the major product of nitrate reduction under acidic conditions and ammonia does not interfere with ARP. Under alkaline conditions, nitrite is the major product of nitrate reduction and nitrite interferes with ARP. Under acidic conditions, a voltage in the range of -0.6 to -1.0 V (relative to Ag / AgCl) can be applied to the copper electrode. Higher voltages will cause the formation of nitrite instead of ammonia and should be avoided. Electrolysis should continue until the desired nitrate concentration is reached.

[0075] In some embodiments, electrochemistry may be performed as a pretreatment to reduce nitrates using a copper:iron cathode. The electrode is operated under a constant reduction bias to limit the dissolution of Cu that could lead to electrode corrosion. + Cu 2+ Fe 2+ , or Fe 3+ The formation of nitrates and nitrites is achieved. The solution can be altered, for example by adding a base, or by maintaining the solution in an alkaline pH range, such as above about 10, or between about 10 and about 12, to limit iron dissolution that may occur under acidic conditions. A voltage in the range of -1.3 to -1.4 V (relative to Ag / AgCl) can be applied to the Cu:Fe cathode. This is sufficient to effectively reduce nitrates and nitrites to nitrogen gas while limiting competition from water reduction. Electrolysis should continue until the desired nitrate concentration is reached.

[0076] An electrochemical system can be used before or simultaneously with UV irradiation. Figure 2Examples of electrochemical systems that can be used in various embodiments described herein are shown, for example, during various pretreatment processes prior to UV irradiation. Containers containing anodes or cathodes may also be referred to as anode compartments and cathode compartments, respectively. For example, as described above, the system shown can be used for pretreatment to reduce nitrates. The system can also be used in post-treatment steps to recover and reuse valuable reagents, such as sensitizers. The electrolytic cell shown is an electrochemical device that uses an external power source to provide electrical energy to drive chemical reactions that would not occur without the application of electrical energy. The electrical energy establishes a voltage difference between two electrodes immersed in an electrolyte. The electrolyte can be a solvent containing dissolved salts or a combination of salts. For example, in many embodiments, the solvent is water and the salt is an inorganic salt (such as sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, sodium sulfate, and / or potassium sulfate). However, in the various embodiments described herein, some salts (such as sodium nitrate, potassium nitrate, sodium perchlorate, and potassium perchlorate) may interfere with the photochemical reaction because they react with solvated electrons, and therefore these salts are excluded from use as electrolytes. Various embodiments include an aqueous solution, and the concentration of the electrolyte may be between about 0.01 M and 1.0 M, or at least about 0.1 M, for example between about 0.1 M and about 1.0 M, to allow charge migration.

[0077] exist Figure 2 In the illustrated electrolytic cell example, the system comprises two electrodes, a power source, an electrolyte, and an inert gas that can be bubbled through the system. The electrodes are in separate compartments connected by a membrane or salt bridge (also known as an ion bridge). The salt bridge or membrane serves several important functions, including maintaining electroneutrality, stabilizing the junction potential, and minimizing cross-contamination. A typical membrane used in the device is a cation exchange membrane. Examples of usable cation exchange membranes include, but are not limited to, perfluorinated or partially fluorinated polymers, such as Nafion. In alternative embodiments, the electrodes may be located in the same compartment. Although not shown, in various embodiments, the electrolyte can be stirred in both compartments, for example by a mechanical stirrer or a magnetic stirrer containing a magnet in the compartment with the battery located at the top of the magnetic stirrer. In this electrolytic cell configuration, reaction products formed at each electrode are separated. This is useful in some cases because some products may interfere with the desired reaction. Although Figure 2 A single electrode is shown in the anode and cathode compartments, but several electrodes can be placed in these compartments. These electrodes can be made of the same material or different materials.

[0078] Figure 3This is an example of an electrolytic system that can be used for nitrate reduction according to various embodiments. In this example, the electrolytic cell is a separated 2-electrode nitrate / nitrite reduction electrolytic cell. The nitrate / nitrite solution and the separate electrolyte solution are separated by a cation exchange membrane. Both solutions are purified with an inert gas (e.g., argon). The cathode is placed in the nitrate / nitrite solution, and the anode is placed in another electrolyte solution. A voltage is applied between the cathode and anode to cause the nitrate / nitrite to be reduced to N2 at the cathode and a sacrificial oxidation reaction to occur at the anode. The oxidation reaction occurring at the anode may be the oxidation of water to form O2. In another embodiment, a sacrificial electron donor (such as sodium sulfite) may be added to reduce the voltage requirement of the cell.

[0079] In some embodiments, the electrode system can be used in a separate compartment from the photolysis chamber. For example, some embodiments may have an electrochemical system, separate from the photolysis chamber, that removes impurities such as nitrates and nitrites, allowing impurities to be washed away from the wastewater while simultaneously photolyzing the pre-purified water. For example, the system may include a first chamber where pretreatment occurs and a second chamber where photolysis occurs. The system may also have additional chambers. After the photolysis of the first batch of wastewater is complete, the treated wastewater can be removed from the photolysis chamber, and the pretreated solution can be transferred from the pretreatment chamber to the photolysis chamber. The pretreatment chamber can then be refilled with wastewater, such as PFAS-contaminated water, for further pretreatment. In this way, pretreatment and photolysis can occur simultaneously, but in separate chambers.

[0080] In some embodiments, the post-electrolysis solution may pass through a cation exchange resin prior to ARP treatment. In this way, any cations in the solution that would be harmful to ARP due to the dissolution of the nitrate reduction cathode can be replaced with Na or K, which are harmless to ARP.

[0081] Pre-treatment filtration. Various embodiments may include pre-treatment filtration of wastewater. For example, Figure 4A schematic diagram illustrates potential pathways to implement membrane-based separation technologies, such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration, forward osmosis, and / or electrodialysis, prior to photoreduction to improve water flux and defluorination performance. In some embodiments, the process begins with pretreatment filtration through one or more membrane systems (e.g., RO, NF, and / or UF) to concentrate PFAS in contaminated wastewater. The membrane rejectant solution, also known as the concentrate, contains material that did not pass through the membrane, such as large PFAS molecules with a molecular weight greater than half the molecular weight cutoff (MWCO). Therefore, the PFAS concentration in the membrane rejectant solution increases, while the water that passed through the membrane contains no or only trace amounts of PFAS compounds. After wastewater filtration, the membrane rejectant solution can be further filtered once or multiple additional times by passing it through the same and / or different membrane systems. The membrane rejectant solution with a PFAS concentration higher than the initial concentration can then undergo photoreduction. After photoreduction treatment, the solution can optionally be filtered again through one or more membrane systems to remove any remaining PFAS compounds in the effluent. Subsequent filtration processes also facilitate the recovery and reuse of chemicals used in the destruction process (e.g., recycling concentrated rejects back to the light reactor). This filtration process can be used in any of the various systems and methods for destroying PFAS described herein. Furthermore, other types of filter media or membranes can be used to selectively concentrate and isolate PFAS from background components. For example, alternative pore size membranes with macropores or nanopores can be used to selectively isolate PFAS into rejects while allowing anions such as nitrates, chlorides, or sulfates to pass through the membrane into the permeate.

[0082] Organic matter pretreatment. Other contaminants that may inhibit the UV-ARP process are those that inhibit UV light transmission into the water flow. These contaminants include, but are not limited to, organic matter such as humic acid, particulate / suspended solids, and inorganic species such as iron that absorb UV light. These contaminants can also be reduced in concentration or removed through pretreatment according to various embodiments.

[0083] Various techniques can be used to remove UV-inhibiting substances. Techniques for removing solids include, but are not limited to, flocculation, coagulation, clarification, filtration, centrifugation, and sedimentation. For removing organic components, pretreatment methods such as chemical oxidation can be used, including, but not limited to, photochemical, chemical, ozone decomposition, or electrochemical oxidation processes. Furthermore, in various embodiments, biological or hydrothermal treatments can be utilized. Oxidizing species that can be used include, but are not limited to, ozone, hydrogen peroxide, persulfates, and permanganate species.

[0084] Reagent pretreatment. In various embodiments, the pretreatment method may include adding a reagent used in UV-ARP that yields byproducts that do not interfere with UV-ARP. For example, sulfites may be added as a pretreatment to reduce or eliminate oxyhalide contaminants. The byproducts of this reaction are halides and sulfate ions that have minimal impact on UV-ARP.

[0085] Metal complex pretreatment. In various embodiments, another class of solvated electron scavengers that can be removed through pretreatment are metal ions or metal complexes. The levels of heavy metals in wastewater are constantly increasing, including zinc, mercury, nickel, chromium, and arsenic, which pose concerns for human health. The increase in these species is a result of industrial activities such as electroplating, battery manufacturing and disposal, textiles, petrochemicals, and papermaking. Wastewater may also contain silver, iron and manganese, calcium, molybdenum, antimony, arsenic, and cobalt. Various embodiments include methods and systems for removing these species, including electrocoagulation, adsorption treatment (using synthetic and / or natural adsorbents), membrane treatment, chemical treatment, electrotreatment, and photocatalytic treatment. Adsorption treatment may include carbon-based adsorbents, including one or more of activated carbon, carbon nanotubes, and graphene, and in some embodiments, other chemical species may be grafted onto the carbon treatment. Other adsorbents that can be used in various embodiments include chitosan, various minerals (e.g., mica, clay, and zeolite), magnetic adsorbents (where magnetic nanoparticles are attached to the adsorbate species), and metal-organic framework materials. For example, the treatment solution can be passed through a column or bed to remove the cleaning agent. Alternatively, reagents can be added to the treatment solution to cause precipitation, coagulation, or flocculation. The supernatant can then be settled and removed, for example, by decantation or siphoning. In other alternatives, solids can be removed by passing the solution through a filter. In various embodiments, membranes are also used to treat metal contamination. Membrane configurations can include ultrafiltration, nanofiltration, microfiltration, reverse osmosis, forward osmosis, and electrodialysis, as described above regarding filtration pretreatment. Other embodiments can include the removal of metals from water by chemical separation methods, such as precipitation, coagulation, and / or flocculation. Various electrochemical treatments available for removing metal species in some embodiments include electrochemical oxidation or reduction and electrocoagulation. Furthermore, in some embodiments, ion exchange treatment can be considered as an electrochemical form of separation and is an effective means of removing metal ions.

[0086] In some embodiments, cation exchange can be used to eliminate or reduce the concentration of one or more metal contaminants. For example, cation exchange membranes can be deployed to simultaneously reduce various cationic transition metal species (e.g., Fe) that may remove solvated electrons. 2+ Fe 3+ Mn 3+ Cu 2+ Cu 1+ Pb 2+ Cd 2+The concentration of cation exchange membranes can also reduce or substantially eliminate basic metal cations (such as Mg). 2+ and Ca 2+ The concentrations of these cations, upon the addition of alkali, are such that they precipitate as Mg(OH)₂ and Ca(OH)₂, respectively. The addition of alkali can be used to achieve high pH conditions for advanced reduction processes, as discussed further below. However, the fine precipitates of Mg(OH)₂ and / or Ca(OH)₂ can cause light scattering, which may reduce the number of photons that can be absorbed by the sensitizer. The consequences could be higher energy usage and / or longer reaction times. Therefore, it is preferable to use alkali to promote the removal of Mg. 2+ and Ca 2 + Preprocessing methods.

[0087] Solids. Depending on the source of the waste stream, some embodiments may include a settling step, which may be performed before and / or after other pretreatments, such as before and / or after oxidation pretreatment. This optional settling step may be used to allow solids (e.g., soil particles) to settle from the liquid, as well as to increase UV transmittance. For example, pretreatment of a waste stream containing landfill leachate and natural water sources may include a settling step, which may involve allowing the waste stream to stand for a period of time (e.g., at least one hour, e.g., about one hour to one day, or about 6 hours to about 18 hours, or about 10 to about 14 hours, or about 12 hours). The time required for the settling step (if any) may depend on the source of the waste stream and the level of solids present. Once completed, liquid components can be removed from the settled solids and then further treated to break down PFAS by pretreatment and UV photoreduction.

[0088] Oxidative pretreatment. In some embodiments, an oxidative pretreatment process may be used to treat PFAS containing the target fluoropolymer species. In some embodiments, partial decomposition of long-chain fluoropolymers may be carried out via an oxidation process.

[0089] Oxidative pretreatment can be used, for example, to treat fluoropolymer species contained in aqueous film-forming foam (AFFF) products. Oxidative pretreatment and other chemical treatments are also beneficial for PFAS in wastewater and from sources of PFAS concentration, such as concentrates generated by foam fractionation processes. Foam fractionation occurs when a gas (e.g., air or nitrogen) is bubbled through water containing PFAS. PFASs adhere to the bubbles and are carried to the surface, where they can trap the foam. In some cases, additional surfactants are added to facilitate this process.

[0090] According to some embodiments, pretreatment may utilize one or more techniques that can be applied in combination, simultaneously, and / or sequentially. For example, oxidative treatment may be used to reduce or eliminate several organic species (such as humic acid and / or fulvic acid). Humic acid and fulvic acid have absorption in the UV spectrum, and their presence may reduce the number of photons absorbed by the sensitizer. As mentioned above, cation exchange media may be used to eliminate or reduce the concentration of one or more metallic contaminants. In various embodiments, the pretreatment method may include the removal of Mg. 2+ and Ca 2+ .

[0091] An example of sequential pretreatment is: performing an oxidative pretreatment, then passing the solution through an ion-exchange membrane, followed by a nanofiltration step. However, in some embodiments, such as when the goal is to remove Mg... 2+ and / or Ca 2+ In this case, oxidative pretreatment can be omitted. For example, an ion exchange membrane can be used, and subsequent nanofiltration can be omitted. Alternatively, an alkali (e.g., NaOH / KOH) can be added to raise the pH to remove Mg. 2+ and / or Ca 2+ This leads to precipitation, which is then separated using settling tanks or other methods.

[0092] In some embodiments, the oxidative pretreatment processes disclosed herein can be used to treat target fluoropolymer species, such as those contained in aqueous film-forming foam (AFFF) products. The thermal oxidative and ozone oxidative pretreatment processes described herein can also be used to treat waste streams generated during foam fractionation. Foam fractionation occurs when a gas (e.g., air or nitrogen) is bubbled through water containing PFASs. PFASs adhere to the bubbles and are carried to the surface, where foam can be trapped. In some cases, the foam fraction may contain additional surfactants added to facilitate the process.

[0093] Depending on the source of the waste stream, some embodiments may include a step of settling the waste stream before and / or after oxidation pretreatment, as described above.

[0094] Besides solid particles that may be present in the waste stream, other species present in the waste stream can also reduce the chemical processes of UV transmission or photoreduction. Therefore, pretreating the waste stream to improve UV transmission is useful, but it is important not to introduce any species that would interfere with the UV photoreduction process. The various oxidative pretreatment embodiments disclosed herein can pretreat the waste stream not only to improve UV transmission, but also without disrupting the UV photoreduction reaction. In some embodiments disclosed herein, such as oxidative pretreatment embodiments, subsequent UV photoreduction may be improved even without increasing UV transmittance. For example, pretreatment may not result in improved UV transmission, but improved photolysis may still be possible by other means, such as through pretreatment products that interact with the reagents used in photolysis.

[0095] Pretreatment methods that can be used in various embodiments include the oxidation of the waste stream. For example, the waste stream can be pretreated using thermal oxidation. In other embodiments, ozone oxidation can be used for pretreatment.

[0096] Examples involving thermal oxidation may involve combining the waste stream with chemical additives and adjusting the pH. The chemical additives may contain persulfates and acids or bases to adjust the pH.

[0097] For example, in some embodiments, the persulfate may be potassium persulfate, sodium persulfate, and / or aluminum persulfate. The amount of persulfate may be adjusted as needed to achieve the desired concentration in the final treated solution. For example, the concentration of persulfate in the final solution may be about 100 to about 200 mM, or about 125 mM to about 175 mM, or about 140 to about 160 mM, or about 150 mM.

[0098] In some embodiments, the base may be, for example, sodium hydroxide, potassium hydroxide, and / or calcium hydroxide. In some embodiments, the acid may be, for example, sulfuric acid, hydrochloric acid, and / or phosphoric acid. The amount of acid or base may be adjusted as needed to achieve a desired pH. For example, when thermal oxidation is performed under alkaline conditions, the pH may be adjusted to about 12, for example, about 10 to about 14, or about 11.5 to about 12.5, or about 11.8 to about 12.3. For example, when thermal oxidation is performed under acidic conditions, the pH may be adjusted to about 3.0, for example, about 1.5 to about 5, or about 2 to about 4, or about 2.5 to about 3.5.

[0099] Thermal oxidation can be carried out in a vessel treating wastewater under elevated temperature and pressure. Examples of vessels that can be used include, for example, autoclaves. In some embodiments, the thermal oxidation process can be carried out in the same vessel as the UV treatment, for example, in a batch process. In other embodiments, the oxidation process can be carried out in a separate treatment vessel prior to UV light treatment in the UV light treatment vessel.

[0100] In some embodiments, the thermal oxidation pretreatment can be carried out at elevated temperatures. For example, the wastewater and added chemicals can be heated to about 80 to about 160 degrees Celsius, or about 100 to about 140 degrees Celsius, or about 115 to about 125 degrees Celsius, or about 120 degrees Celsius, but other temperatures may also be used.

[0101] In some embodiments, thermal oxidation can be carried out at elevated pressure and elevated temperature. For example, wastewater and added chemicals can be heated at a pressure of about 0.5 to about 10 bar, or about 1 to about 5 bar, or about 1.5 to about 2.5 bar (e.g., about 2 bar).

[0102] Examples of ozone oxidation may involve combining the waste stream with an alkali (e.g., sodium hydroxide, potassium hydroxide, and / or calcium hydroxide). The amount of alkali used may be adjusted as needed to raise the pH to a desired level, for example, pH from about 10 to about 14, or from about 11.5 to about 12.5, or from about 11.8 to about 12.3, or about 12.

[0103] Wastewater containing alkalinity can then be treated by ozone oxidation. For example, the wastewater stream can be treated using an ozone generator, such as a portable ozone generator like the MultiPurpose Ozone Machine from VANSU Technology Co., Ltd. in Shenzhen, China. Treatment rates can be, for example, from approximately 500 mg / h O3 to approximately 2000 mg / h O3, such as 800 mg / h O3 to approximately 1000 mg / h O3, or approximately 1000 mg / h O3. Treatment duration can be from approximately 3 to approximately 9 hours, such as from approximately 7 to approximately 10 hours, or approximately 6 hours. The treatment duration may depend on the ozone generation rate and exposure.

[0104] Pretreatment with thermal oxidation or ozone oxidation, and optionally a sedimentation step, can significantly improve UV transmittance. For example, UV transmittance can be increased from 0% to approximately 10-20%, or to approximately 25-45%.

[0105] Furthermore, pretreatment with thermal or ozone oxidation, along with an optional sedimentation step, can significantly improve UV transmittance without separating PFAS from the liquid. This surpasses some pretreatment methods that remove substances that improve UV transmittance but also remove some PFAS. This separation of PFAS necessitates treating two PFAS streams, significantly increasing treatment complexity and cost. In contrast, the oxidative pretreatment method disclosed herein allows for improved UV transmittance to enhance PFAS destruction without removing PFAS from the wastewater, thus maintaining a single waste stream for subsequent treatment.

[0106] After pretreatment according to the embodiments described herein, the wastewater can be treated using UV photoreduction. However, in some cases, it may be preferable to dilute the wastewater stream before UV photoreduction. For example, the wastewater stream can be diluted by about 1.5 to about 10 times, such as about 2 to about 5 times, or about 2 to about 3 times. The amount of dilution may depend on the source and nature of the wastewater stream. However, due to the improved UV transmittance (which does not disrupt UV photoreduction) resulting from the various embodiments, lower dilution is required. This makes the process more efficient because the treatment volume is not significantly increased compared to some other methods.

[0107] Following pretreatment and optional dilution, the waste stream can be treated to break down PFAS, for example, by using a photoreactor for UV photoreduction. The photoreactors employed in various embodiments comprise a light source that delivers a narrow range of ultraviolet radiation with a peak at approximately 222 nm, such as a krypton / chlorine excimer lamp.

[0108] Photoreduction methods are based on the generation of highly reducing species, typically solvated electrons produced by irradiation of photosensitizers. As described herein, oxidative pretreatment of wastewater can improve the efficiency of photochemical destruction of PFAS and enable photochemical methods to be more widely used in various PFAS-containing waste streams.

[0109] In some embodiments, the UV photoreduction process can be carried out using one or more reactor vessels having one or more UV light sources, as described below. The reactor is filled with pretreated wastewater containing PFAS, water, and sensitizers capable of absorbing UV light and generating reactive species. Additionally, alternatively, one or more other chemical additives may be present to promote the reaction.

[0110] Figure 5 Examples of PFAS treatment methods applicable to various embodiments are shown. The method begins with the optional settling of wastewater 10, followed by decanting or otherwise removing liquid from the settled wastewater 20. For example, as an alternative to decanting, the clarified water can be removed from the top above the solids, the solids can be removed or discharged from the bottom below the clarified water, or other separation methods can be used. Next, the wastewater, after optional decanting (or otherwise separated), is pretreated 30, for example by oxidative pretreatment. The pretreated wastewater is then optionally diluted 40, and then the pretreated and optionally diluted wastewater is subjected to photoreduction 50, for example by UV treatment at 222 nm and / or 254 nm.

[0111] Figure 6A block diagram of a thermal oxidation and photoreduction method is shown. The method begins with optional sedimentation of wastewater 110, followed by decanting or otherwise removing liquid from the settled wastewater 120. Next, the optionally decanted (or otherwise separated) liquid wastewater is mixed with persulfate and an acid or base 130. The wastewater is then pretreated by thermal oxidation 140 by placing it under elevated temperature and pressure for a sufficient duration to complete the reaction. Next, the pretreated wastewater is optionally diluted 150 and mixed with a photosensitizer 160. The order of steps 150 and 160 can be alternately reversed or performed simultaneously. The wastewater is then subjected to photoreduction 170, for example, UV treatment at 222 nm and / or 254 nm.

[0112] Figure 7 A block diagram of an ozone oxidation and photoreduction method is shown. The method begins with optional sedimentation of wastewater 210, followed by decanting or otherwise removing liquid from the settled wastewater 220. Next, the decanted liquid wastewater is optionally mixed with persulfate and an acid or alkali 230. The wastewater is optionally subjected to sedimentation treatment 240, followed by ozone oxidation 250 for a sufficient time to complete the pretreatment reaction. Next, the pretreated wastewater is optionally diluted 260 and mixed with a photosensitizer 270. The order of steps 260 and 270 can be alternatively reversed or performed simultaneously. The wastewater is then subjected to photoreduction 280, for example by UV treatment at 222 nm and / or 254 nm.

[0113] Figures 5 to 7 The method shown may optionally include additional settling and / or decantation steps (or other separation steps), or the settling and / or decantation steps (or other separation steps) may be performed at other times. For example, Figure 6 The method may include mixing wastewater with persulfate and an acid or alkali for 130°C, followed by optional sedimentation and decantation steps (or other separation steps), then decantation (or otherwise removal) of the separated liquid, followed by thermal oxidation of the decanted liquid for 140°C. As another example, Figure 7 The method shown may include a decantation step (or other form of removal of the separated liquid) after wastewater settling step 240 and before ozone oxidation step 250.

[0114] In an exemplary embodiment, a wastewater stream containing PFAS is settled for a suitable period of time to allow solids to settle, for example, about 6 to about 18 hours. The liquid is decanted or otherwise separated from the solids and mixed with persulfate and an acid or base. The resulting wastewater contains a concentration of about 150 mM persulfate and a pH of about 11 to about 13 or about 12. The wastewater is then treated at a temperature sufficient to complete the reaction, for example, about 100 to about 140 degrees Celsius or about 100 degrees Celsius and about 0.5 to about 10 bar, or about 1 to about 5 bar, or about 1.5 to about 2.5 bar, for example, about 2 bar, for example, about 1 to about 3 hours, or about 2 hours. After pretreatment, the wastewater is then combined with a photosensitizer containing sulfite and halide salts and a base. The resulting wastewater contains about 40 to about 60 mM sulfite, about 7 to about 13 mM halide salts, and a pH of about 13 to about 15. Alternatively, the resulting wastewater may contain about 5 to about 15 mM sulfites, about 1 to about 4 mM halide salts, and a pH of about 12. The wastewater may then be optionally diluted about 2 to 5 times, or about 2 to 3 times. The wastewater is then subjected to UV photoreduction at 222 nm and / or 254 nm for the time required to complete the reaction, for example, about 1 hour to about 24 hours, or about 2 hours to about 12 hours, or about 4 hours to about 8 hours. After photoreduction, most of the PFAS may be destroyed, for example, about 70% to about 90%, or about 80%. For example, after about 8 hours of photoreduction, about 80% of the PFAS may be destroyed compared to the original PFAS levels in the wastewater.

[0115] In some embodiments, in addition to the methods disclosed above, additional pretreatment methods may be employed. For example, pretreatment to remove nitrates, nitrites, or other contaminants can be accomplished through a variety of methods, including chemical reduction, ion exchange membranes, electrodialysis, electrochemical reduction, photochemical reduction, and bioremediation in which contaminants are degraded by organisms. Furthermore, to remove UV-inhibiting species, techniques such as flocculation, coagulation, clarification, filtration, centrifugation, and sedimentation can be used. To remove organic components, treatments such as chemical oxidation (e.g., photochemical oxidation) or electrochemical oxidation processes, as well as other chemical or ozone decomposition methods, can be used. Additionally, biological or hydrothermal treatments can be utilized. Other usable oxidizing species include permanganate species. The oxidizing pretreatment systems and methods described herein can be used in conjunction with any of the processes described above.

[0116] Systems for UV-induced destruction of PFAS can consist of a single reactor vessel in which oxidative pretreatment, optional additional pretreatment (e.g., sedimentation), UV photoreduction, and other steps are performed sequentially. Alternatively, for example, to maximize process efficiency, the above processes can occur in a single vessel or in separate vessels or chambers.

[0117] Photolysis steps

[0118] UV reactor. In some embodiments, the system for destroying PFAS may comprise a single reactor vessel in which pretreatment, photolysis, and posttreatment steps are performed sequentially. In other embodiments, one or more of the pretreatment, photolysis, and posttreatment steps may occur in separate vessels or chambers of a vessel, for example, for a continuous process.

[0119] In some embodiments, the UV photoreduction process can be carried out using one or more reactor vessels equipped with one or more UV light sources. The reactor is filled with pretreated wastewater containing PFAS, water, and a sensitizer capable of absorbing UV light and generating reactive species. Additionally, optionally, one or more other chemical additives may be present to promote the reaction.

[0120] The reactor vessel may contain one or more UV light sources that emit light, such as 222 nm or 254 nm UV light. In some embodiments, a light source, or various light sources, may emit several wavelengths, and light of other wavelengths besides 222 nm and 254 nm (e.g., 185 nm) may also contribute to the photoreduction of PFAS.

[0121] The photoreactor can be used alone or in combination with other reactors, for example, in a series configuration, which may employ light reduction at the same or different wavelengths, or other PFAS destruction methods. Alternatively, one or more steps can be performed in the same container.

[0122] The applicant has provided examples of PFAS species capture systems, treatment systems, and pretreatment in other applications, such as U.S. Patent Application No. 18 / 212,603, filed June 21, 2023, entitled “METHOD AND APPARATUS FOR THE DESTRUCTION AND DEFLUORINATION OF PER- AND POLYFLUOROALKYLSUBSTANCES (PFAS), FLUOROTELOMERS AND OTHER PERSISITENT ORGANIC POLLUTANTS”, and U.S. Patent Application No. 63 / 513,782, filed July 14, 2023, entitled “PROCESSES FOR EFFICIENT PHOTOCHEMICAL DESTRUCTION OF PFAS FROM WASTE”. The disclosures of all these applications are incorporated herein by reference. These include STREAMS, and U.S. Patent Application No. 18 / 555,135, filed October 12, 2023 (national period entry), entitled "SORBENTS AND METHODS FOR THE CAPTURE AND DEFLUORINATION OF PER AND POLY FLUOROALKYLSUBSTANCES (PFAS)". The systems and methods described herein may be used in combination with the methods and systems described in these applications.

[0123] An example of a photoreactor that can be used in various embodiments includes one or more lamps, such as lamps comprising cylindrical bulbs or other shaped bulbs, and one or more photoreactor containers configured such that the light from the lamps can be projected onto the reactor container or the contents of the container. The lamps may be supported on a frame, such as a metal support frame, and in use, the lamps are positioned at a desired distance above the top surface of the photoreactor container and / or above the top surface of the liquid within the photoreactor container to directly illuminate the surface of the reaction solution or to illuminate through the reactor container walls. Alternatively, the lamps may be adapted within the reactor container to directly illuminate the contents from inside the reactor container. The bulbs may be protected and / or isolated from the reaction solution within the reactor container, for example, through sleeves or other barriers. In some embodiments, the photoreactor container may include two cylindrical lamps and a support frame that horizontally holds the two lamps at a selected distance above the horizontal plane of the photoreactor container. Other lamp and reactor container configurations and orientations can be used to optimize energy delivery and PFAS destruction.

[0124] The photoreactor container can be any suitable material, such as quartz or other non-reactive and transparent materials to 222 nm radiation. In other embodiments, such as those where the light bulb is located within the reactor container, the reactor container does not need to be transparent and can be a non-transparent and non-reactive material, such as stainless steel. The container may be configured to contain fluid and may include a sealable top. In some embodiments, the photoreactor may contain a single reactor container, while in other embodiments it may contain more than one reactor container, such as two or three or more. The reactor container can be of any size or shape. In some embodiments, the reactor container is cylindrical.

[0125] The lamp, lamp holder, and reactor vessel can be housed in a shell, such as a metal shell or other enclosure.

[0126] Examples of lamps that may be used in various embodiments include krypton / chlorine excimer lamps that emit 222 nm radiation. Alternatively, other excimer lamps that emit narrowband radiation at other wavelengths may be used. These lamps may consume 100 watts of power or may consume more or less power. The lamp power supply may be 20 kV or may be higher or lower than 20 kV. In some embodiments, the power of the lamp for emitting 222 nm and 254 nm may, for example, be between about 50 and about 5000 W, for example between about 100 and about 1000 W, or between about 100 and about 300 W. A single lamp or several lamps may be used, and these lamps may be the same or different.

[0127] The photoreaction method described herein can be carried out at room temperature or above room temperature. For example, in some embodiments, the temperature of the photoreactor during the reaction can be between about 55 and about 60 degrees Celsius. However, higher or lower temperatures can be used alternatively. Furthermore, heating and / or cooling elements (e.g., ducts, fans, and lights) can be added to the reactor and / or to the space containing the reactor to raise or lower the temperature.

[0128] During UV treatment, the reactor solution may be stagnant or agitated. For example, the reactor may include a stirrer or agitator capable of stirring or agitating the solution. In some embodiments, stirring or agitating the reactor solution during irradiation may facilitate exposure of the PFAS compound to areas of higher radiation. Alternatively, the solution may be recycled via a heat exchange unit.

[0129] Ultimately, optimizing the reactor solution to improve efficiency may also depend on directly stirring or agitating the compounds to expose more solution components to areas with higher radiation fields in a shorter time.

[0130] In some embodiments, irradiation of PFAS at 222 nm and / or 254 nm can be carried out in a reaction solution containing only an aqueous solution of PFAS. However, the results can be improved by adding a reducing solution of appropriate concentration. This may result in faster, more efficient, and more complete PFAS destruction.

[0131] Photoreduction of PFASs may disrupt PFASs through mineralization, involving the conversion of carbon-fluorine bonds into fluoride ions and carbon species, such as acetates, carbon dioxide, and / or carbonates. In this context, mineralization may involve the reduction of carbon-bonded fluorine on PFASs to fluoride ions (F-).

[0132] Some embodiments achieve complete or near-complete destruction of PFAS, such as destruction of more than 99%. Some embodiments achieve at least 90% or at least 95% destruction of PFAS, such as about 90% to about 100%, or about 95% to about 100% destruction of PFAS.

[0133] The processing time required to achieve complete or near-complete destruction of PFAS can depend on the design of the photoreactor used and other variables.

[0134] Various embodiments include a UV reactor for photochemical destruction of PFAS. In some embodiments, the UV reactor includes a photochemical chamber containing one or more UV light sources. The UV reactor may further include a recycling system equipped with a heat exchange system configured to control the solution temperature. The UV reactor may further include a sensor module configured to continuously monitor the physical and / or chemical state of the reaction solution. In some embodiments, the UV reactor may also include one or more ports for adding additional reagents and / or sampling the reaction mixture.

[0135] Examples of UV reactors according to various embodiments include a reactor that provides UV light greater than 1000 Ws and is configured to maintain a solution below 50°C. The UV reactor includes a sensor module configured to provide information via a closed-loop control system to help maintain optimal photochemical conditions, automatically maintaining these conditions. In some embodiments, the sensor system includes one or more sensors configured to monitor one or more of the following: temperature, pressure, pH, UV intensity, fluoride ion concentration, and redox potential.

[0136] Additives filled from the port can be added continuously or in one or more batches. Typical additives include, but are not limited to, sulfites, initiators, bases (such as sodium hydroxide), or sodium carbonate.

[0137] Depending on the waste stream, it may be useful to perform both oxidative and reductive treatments. While these two treatments can be carried out sequentially in the same container, they can also be performed in separate containers. The order in which these steps are performed can vary depending on the composition of the waste stream.

[0138] Figure A shows an example of a UV reactor as the photochemical component of a treatment system. Figure 8 The UV reactor in the system can operate in batch or continuous mode. One embodiment of this design would be a continuous stirred tank reactor.

[0139] Sensitizers. Various embodiments include sensitizers added to the wastewater. Photoreduction is based on the generation of highly reducing species, such as solvated electrons, produced by irradiation with a photosensitizer.

[0140] In UV-ARP, the sensitizer absorbs UV photons and thus generates oxidized sensitizer and solvated electrons, as shown below: a. Sensitizer + hn (UV photons) → Sensitizer + + e aq - (solventized electrons) Photosensitizers that can be used in various embodiments include halides, pseudohalogens, inorganic oxyanions, anionic metal complexes, metal clusters, Zintl compounds, transition metal nanoparticles, organic anions, nitrogen heterocycles, boron-doped nanodiamonds, and / or hypozonotriacetic acid. These photosensitizers can be used in conjunction with different light sources or independently.

[0141] Examples of usable halides include iodides, chlorides, and bromides; examples of usable pseudohalogens include cyanides, isocyanates, cyanates, isocyanates, isocyanates, azides, hydroxides, hydrosulfides, hydroselenides, hydrotellurides, fulminates, thiocyanates, selenocyanates, tellurates, isothiocyanates, nitrogen oxides, tetracarbonylcobaltate, trinitromethane, tricyanomethane, 1,2,3,4-thiatriazole-5-thiolate, fulminates, cyanophosphides, and gold compounds. Examples of usable inorganic oxyanions include sulfite (SO32-). 2- ), sulfate (SO4 2- ), hyposulfate (SO2) 2- ), thiosulfate (S2O3) 2- ), carbonate (CO3) 2- ), phosphate (PO4) 3- ), phosphate (PO3) 3- ), hypophosphate (PO2) -3 ) and borate (BO3) 3- ), including the protonated forms of these anions (e.g., HSO3), - HSO4 - HCO3 - Examples of usable anionic metal complexes include ferricyanide ions, ferric(III) tris(oxalato) ions, tetrachloroplatinate ions, hexachloroiridate ions, cyanocopperate ions, and cerium(III) complexes. Examples of usable metal clusters include Mo6Cl. 14 2- Zr6CCl 12 Ta6Cl 18 4- Re3Cl 12 3- And iron-sulfur clusters. Examples of usable Zintl compounds include [Bi3]. 3- [Sn9] 4- Examples of usable transition metal nanoparticles include gold, copper, and iron. Examples of usable organic anions include ascorbic acid anion, ascorbic acid dianion, phenolates, cresolates, dihydroxybenzene anion, methoxyphenolates, and thiophenes. Examples of usable nitrogen heterocycles include indole-3-acetic acid.

[0142] Other components that may be included in the reactor include photosensitizers (e.g., halide salts) alone or in combination with other components (e.g., sulfites). The concentration of the photosensitizer will depend on the electronic absorption spectrum of the photosensitizer, the spectral output of the lamp, and the concentration of other photosensitizers contained in the reactor. The concentration of the halide salt can be from about 1 mM to about 150 mM, or from about 5 mM to about 15 mM, or from about 7 mM to about 13 mM. For example, when UV 254 nm or UV 222 nm radiation is used in a photoreactor, the concentration of KI can be from about 1 mM to about 10 mM. For example, when UV 22 nm radiation is used, the concentration of KBr can be from about 10 mM to about 150 mM. The concentration of sulfites can be from about 5 mM to about 100 mM, for example from about 25 mM to about 75 mM, or from about 35 mM to about 65 mM, or from about 45 mM to about 55 mM. For example, when using UV 222 nm light in the reactor, the concentration of sulfite can be about 5 mM. For example, the pH can be above 10, or above 12, or above 13. For example, in some embodiments, the pH can be from about 11 to about 15, or from about 13 to about 15. In other embodiments using UV 185 nm light in the photoreactor, the concentration of the photosensitizer, which may contain halide salts, sulfites, and sulfates, can be from about 1 μmol to about 10 mM. For example, the concentration of NaCl can be about 150 μmol, and the concentrations of sulfate and sulfite are 1 mM. For example, the pH range of the solution can be from about 7, or above 8, or above 10.

[0143] Other components that may be included in the reactor include halide salts alone or halide salts in combination with other components (e.g., sulfites). In some embodiments, such as those utilizing UV 222 nm or UV 254 nm light, the reactor solution may contain KI and Na₂SO₃ (e.g., 1 mM KI and 5 mM Na₂SO₃), but higher or lower concentrations (e.g., 10 mM KI and 50 mM Na₂SO₃) may also be used. Alternatively, other components that may be used in the reactor solution include KBr and Na₂SO₃, for example, about 10 mM KBr and 50 mM Na₂SO₃ when using UV 222 nm light; or about 150 mM KBr and 5 mM Na₂SO₃ when using UV 222 nm light, but higher or lower concentrations may also be used. In some embodiments utilizing UV 222 nm or UV 254 nm light, the photosensitizer comprises about 10 mM Na₂SO₃ and about 2 mM KI at a pH of about 12. In some embodiments, the photosensitizer comprises about 50 mM Na2SO3 at pH about 14 and about 10 mM KI. Other embodiments may contain only sulfites (e.g., Na2SO3), such as about 50 mM Na2SO3, but higher or lower concentrations may be used alternatively.

[0144] In some embodiments, for components such as halide salts, additional components at lower concentrations (e.g., micromolar concentrations) can be used. These low levels can optimize and facilitate efficient light absorption at 222 nm and 185 nm. For example, micromolar concentrations of halide salts can be used.

[0145] In some embodiments, it is preferable to maintain a high pH during photoreduction, for example, a pH of 10 or above, or 11 or above, or 12 or above, or 13 or above. Therefore, in addition to the reagents described above, the inclusion of a base (e.g., sodium carbonate) and / or one or more other bases (e.g., hydroxides) may be useful in increasing reaction efficiency.

[0146] In some embodiments, iodide (I) may be used during photoreduction. - As a photosensitizer, iodides absorb UV photons and can potentially generate various iodine-containing species, including but not limited to iodine free radicals (I₂). . ), iodine (I2), iodine radical anion (I2) - .) and triiodine anion (I3) - Many of these iodine-containing species also react with solvated electrons. If these species are not removed from the system, the concentration of one or more of them will increase, reducing the efficiency of PFAS destruction.

[0147] Furthermore, in some cases, the water to be treated contains other materials that can interfere with reaction efficiency. pH also plays a significant role in reaction efficiency. In some embodiments, the pH may be greater than 9 or about 10, for example, between 12 and 14. Additionally, higher pH may increase the mineralization of PFAS through its effect on chemical degradation mechanisms. In some cases, chemicals may need to be added to alter the properties of the liquid to be treated, which can result in significant costs and generate larger amounts of waste.

[0148] Photosensitizers, including but not limited to those mentioned above, can be further synthetically modified to induce selectivity for PFAS, thereby improving the kinetics and extent of PFAS mineralization in the photochemical reaction. According to various embodiments, the means of imparting PFAS selectivity may include, but are not limited to, the addition of fluorinated, hydrophobic, or other moieties or functional groups that induce electrostatic interactions with the charged terminal groups of the PFAS molecule. The PFAS-selective synthetic modification of the photosensitizer may simultaneously possess one or more of these moieties. These modified PFAS-selective photosensitizers can be further embedded in mesoporous clay materials (including but not limited to montmorillonite, bentonite, or kaolin). PFAS sequestration into the interlayers of the mesoporous clay will thus co-localize the PFAS molecule with the photosensitive active site in a localized environment free of scavengers and co-contaminants.

[0149] The effectiveness of these sensitizers and their selection in a particular embodiment may depend on the wavelength of the light source.

[0150] Light source. In various embodiments, low-pressure mercury lamps, medium-pressure mercury lamps, and amalgam lamps are used as UV radiation sources because they are relatively inexpensive and relatively efficient at converting electrical energy into UV photons. Mercury vapor lamps exhibit distinct spectral lines in both ultraviolet and visible light. 184.5 nm (generally referred to as 185 nm) and 253.7 nm (generally referred to as 254 nm) are important wavelengths for PFAS destruction. However, other light sources can also be used in various embodiments. In particular, various excimer lamps with high efficiency, high power, and narrow-band radiation spanning the UV spectrum (near UV to vacuum UV) are also excellent light sources and can be used in various embodiments. An excimer lamp is a discharge lamp involving a rare gas (e.g., argon (Ar), krypton (Kr), or xenon (Xe), or a halogen dimer (F2, Cl2, Br2, or I2) or a combination of halogens and rare gases). UV light from an excimer source is due to the rare gas dimer (Ar2) Kr2 and Xe2 ), halogen dimer (F2) Cl2 Br2 or I2 ) and rare gas halide excimers (ArF) ArCl ArBr ArI 、KrF 、KrCl 、KrBr 、KrI XeF 、XeCl 、XeBr and XeI The emission of an excited state, where an asterisk denotes an excited state. Examples of excimer light sources that can be used in various embodiments and their main emission outputs include XeXe. (172 nm), ArCl (175 nm), KrI (190 nm), ArF (193 nm), KrBr (207 nm), KrCl (222 nm), KrF (248 nm), XeI (253 nm), Cl2 (259 nm), XeBr Br2 (289 nm) and XeCl (308 nn). The preferred lamp output is between 190 nm and 289 nm. Powerful KrCl The wavelength output and availability of excimer lamps make them particularly favored in certain embodiments. Although excimer lamps may not be as efficient as mercury lamps, the ability to finely tune light emission for a given sensitizer is useful for the overall effectiveness of the photochemical process in various embodiments. These lamps have the added advantage of being mercury-free.

[0151] Other UV light sources that can be used in various embodiments include xenon arc lamps, deuterium arc lamps, mercury / xenon arc lamps, metal / halogen arc lamps, and UV LEDs. The amount of light (power) from UV LEDs is typically much lower than that from mercury lamps or other discharge lamps, and therefore, multiple LEDs can be included in various embodiments to destroy PFASs over a time span, such as from a few minutes to a few hours.

[0152] The energy generated by the light source included in the various embodiments is sufficient for the sensitizer to generate solvated electrons. The wavelength of the UV light generated by the light source and used in the various embodiments may be between about 190 nm and about 300 nm. For example, some embodiments may include a mercury lamp with a strong output peak at 254 nm. In other embodiments, higher energy (lower wavelength) irradiation may be used, such as excimer lamps (e.g., krypton / chlorine excimer lamps). Ultraviolet light-emitting diodes may also be used as the light source.

[0153] Light sources, including but not limited to those listed above, may be used independently or in combination, sequentially or simultaneously, and may be used in a single reactor or in reactors in series.

[0154] Photolysis at 222 nm. The various embodiments described herein relate to systems and methods for photochemically destroying PFASs using UV-ARP with 222 nm radiation to generate highly reducing species (e.g., solvated electrons) produced by irradiating photosensitizers. These processes and systems improve the efficiency of photochemical destruction of PFASs, allowing for broader application of photochemical methods to various PFAS-containing waste streams, and reducing the time and cost required to destroy PFASs.

[0155] In various embodiments, the photochemical system comprises a reactor vessel with one or more UV light sources emitting 222 nm light. The reactor is filled with a liquid consisting of PFAS, water (and / or other solvents), and sensitizers capable of absorbing UV light and generating reactive species. Additionally, one or more other chemical additives may optionally be present to promote the reaction. The photoreactor may be used alone or in combination with other reactors (e.g., in a series configuration). These other reactors may also employ UV-ARP of the same or different wavelengths, or may employ other methods to destroy PFAS. Furthermore, the photoreactor system may include one or more processes for pretreatment of PFAS-contaminated materials (e.g., wastewater or other water sources), as well as post-treatment and fining processes.

[0156] Various embodiments employ a photoreactor containing a light source that delivers narrow-range ultraviolet radiation with a peak of approximately 222 nm, such as a krypton / chlorine excimer lamp.

[0157] The photoreactor container can be any suitable material, such as quartz or other non-reactive materials that are transparent to 222 nm radiation. (When using light of different wavelengths for UV-ARP, the photoreactor container should be alternatively or additionally transparent to that wavelength of radiation.) In other embodiments, such as those where the bulb is located within the reactor container, the reactor container does not need to be transparent and can be a non-transparent and non-reactive material, such as stainless steel. The container can be configured to contain fluid and may include a sealable top. In some embodiments, the photoreactor may comprise a single reactor container, while in other embodiments it may comprise more than one reactor container, such as two or three or more. The reactor container can be of any size or shape. In some embodiments, the reactor container is cylindrical. The lamp, lamp holder, and reactor container can be housed in a shell, such as a metal shell or other enclosure. The same design can also be used for UV-ARP systems delivering other wavelengths.

[0158] Examples of lamps that can be used in various embodiments include krypton / chlorine excimer lamps that emit 222 nm radiation. Alternatively, other excimer lamps emitting narrowband radiation at other wavelengths can be used. These lamps may consume 100 watts of power, or more or less. An excimer lamp system may include a bulb, wiring, and a ballast (power supply), with an overall power conversion efficiency ranging from 0.1% to approximately 20%, decreasing with increasing lamp intensity. In some embodiments supporting high-power lamps, the power supplied to the lamp may be approximately 20 kV, or, for example, in embodiments supporting lower-intensity lamps, the power may be approximately 3 kV.

[0159] The photoreaction method described herein can be carried out at room temperature or above room temperature. For example, in some embodiments, the temperature of the photoreactor can be between about 55 and about 60 degrees Celsius during the reaction. However, higher or lower temperatures may optionally be used. In addition, heating and / or cooling elements (e.g., ducts, fans, and lights) may be added to the reactor and / or the room containing the reactor to raise or lower the temperature.

[0160] During UV treatment, the reactor solution may be stagnant or it may be agitated. For example, the reactor may include a stirrer or agitator capable of stirring or agitating the solution. In some embodiments, stirring or agitating the reactor solution during irradiation may facilitate exposure of the PFAS compound to areas of higher radiation. Alternatively, the solution may be recycled via a heat exchange unit.

[0161] Ultimately, optimizing the reactor solution for improved efficiency may depend on directly stirring or agitating the compounds to expose more solution components to areas with higher radiation fields in a shorter time.

[0162] In some embodiments, irradiation of PFAS at 222 nm can be carried out in a reaction solution containing only an aqueous solution of PFAS. However, the results can be improved by adding an appropriate concentration of a suitable reducing solution. This may result in faster, more efficient, and more complete PFAS destruction.

[0163] Some embodiments achieve complete or near-complete destruction of PFAS, such as destruction of more than 99%. Some embodiments achieve at least 90% or at least 95% destruction of PFAS, such as about 90% to about 100%, or about 95% to about 100% destruction of PFAS.

[0164] The processing time required to achieve complete or near-complete destruction of PFAS can depend on the design of the photoreactor used and other variables. However, in some embodiments, complete destruction can be achieved after processing for about 5 minutes to about 6 hours, for example, complete or near-complete (e.g., 99% or more) destruction of PFAS can be achieved after processing for about 2 hours to about 5 hours.

[0165] In some of the examples included in this paper, control samples without reagents were tested. Even without reagents, PFAS destruction via a direct photolysis process was achieved under irradiation at 222 nm. However, PFAS destruction was much slower and less complete. In contrast, PFAS destruction was faster and more complete when reagents were included. The advanced reduction process described in this paper is believed to yield superior results by generating solvated electrons capable of reacting with carbon-fluorine bonds, without relying on direct energy absorption by PFAS and subsequent bond breaking.

[0166] Furthermore, while direct irradiation at 222 nm may produce some enhanced photolysis of perfluoroalkyl carboxylic acids (PFCAs), fluoropolymers, unsaturated carboxylic acids, and GenX PFAS compounds in the absence of reagents, compared to photolysis at 254 nm, the performance / efficiency of 222 nm treatment alone for perfluoroalkyl sulfonic acids is minimal. In contrast, the advanced reduction process using 222 nm described herein yields a more rapid, complete, and overall more efficient destruction of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs).

[0167] A combination of photochemical and electrochemical methods. In some embodiments, UV photolysis can be used in conjunction with an electrochemical system. This method can be used alone or in combination with other UV photolysis methods described herein, and the combination can further enhance the degradation rate of PFASs. Figure 9 The photoelectrolysis cell shown is an example of an electrolysis cell that can be used in combination with photochemistry, wherein the cathode is immersed in an electrolyte with a UV lamp. This photoelectrolysis cell is similar to the one described above. Figure 2The photoelectrolysis cells discussed are similar. For example, a photoelectrolysis cell like the one shown can be used to reduce a photo-oxidized sensitizer back to a sensitizer to prevent the accumulation of species that can react with solvated electrons. In other embodiments, the photoelectrolysis cell can be used to raise the pH around the electrode and thereby minimize the reaction of solvated electrons with protons. In still other embodiments, the photoelectrolysis cell can be used to generate hydrogen gas, which, under certain conditions, can increase the concentration of solvated electrons, which can significantly improve the photodestructive efficiency of PFAS.

[0168] Considering that the sensitizer may undergo further reactions after oxidation, for example, when iodide is used as the sensitizer, the following reaction may occur: I - (iodide) + hn (UV photon) à I · (iodine free radical) + e aq - (solventized electrons) I · + I · I2 (iodine) I2 + I - à I3 - (Triiodine anion) Iodine radicals, iodine, and triiodine anions are all photolysis byproducts. All of these species are highly efficient scavengers of solvated electrons and exhibit higher second-order reaction rates with solvated electrons than PFASs. The presence and accumulation of these species reduce the efficiency of PFAS destruction; therefore, various embodiments aim to remove these species. For example, as described above, one way to achieve this is by introducing a sacrificial reducing agent capable of reducing the photochemical byproducts back to the original sensitizer. An example of a sacrificial reducing agent that can be used in various embodiments is a sulfite. Sulfites can react with iodide products as follows: SO3 2- + I · SO3 - + I - 2 SO3 2- + I2 à 2 SO3 - + 2 I - 2 SO3 2- + I3 - à 2 SO3 - + 3 I - These reactions are thought to occur via a series of sulfur-iodine intermediates. Furthermore, the chemical reaction appears to be particularly well-suited to iodides.

[0169] In other embodiments, the iodide byproducts can be electroreduced. For example, an electrochemical system can be used to regenerate the original sensitizer (iodide) in situ from the photolysis byproducts (iodine radicals, iodide, and triiodide) in a photolysis reactor. When iodide is used as the sensitizer, the following reaction can occur at the cathode: I · + e - → I - E ° = +0.93 V / SHE I² + 2e - → 2 I - E ° = +0.620 V / SHE I3 - + 2 e - → 3 I - E ° = +0.536 V / SHE Depending on the pH and temperature of the water, iodine can also hydrolyze to produce several products, such as I3. - IO - HOI2 - And HOI. Electrodes that can be used in various embodiments may comprise Ru-based or Pt-based electrodes and metal oxides (e.g., TiO2) as cathode materials that can reduce triiodide to iodide, and graphene oxide deposited with copper-platinum (Cu-Pt) bimetallic nanoparticles to reduce triiodide to iodide.

[0170] For the circuit to be complete, a suitable oxidation process occurs at the anode. In an aqueous medium, various reactions may occur at the anode, but when a high overpotential is present, the following reactions may occur at the anode: 2H₂O → O₂ + 4e - + 4H + E ° = -1.23 V / SHE In various embodiments, the half-cell reactions of iodine reduction and water oxidation are combined to obtain the following overall reaction: I₂ + H₂O → 2 I - + ½ O2(g) + 2 H + The products of this reaction are acid and O2, both of which are undesirable because they may react with solvated electrons. This problem can be mitigated in various embodiments by neutralizing the acid with a base (such as sodium hydroxide) or by removing oxygen, for example, by purging with an inert gas. Another method to avoid oxygen interference is to place the electrodes in separate compartments.

[0171] In some embodiments, the generation of O2 by H2O oxidation can be avoided, for example, by including a sacrificial carbon layer in the electrode material or by using a porous carbon-based anode. Carbon oxidation at the anode is a Faraday process as follows: ¼ C + ½ H₂O → ¼ CO₂ + H₂ + + e - E ° = 0.7-0.9 V / SHE In various embodiments, the oxidation of H2O can be avoided by adding a sacrificial reducing agent. For example, in the UV sulfite / I2 chemical reaction described above, sulfite can be added to the reaction solution. In this case, the anodic and overall reactions will be as follows: Anode (oxidation): SO3 2- + 2OH - SO4 2- + H2O + 2 e - E ° = 0.936 V / SHE Cathode (reduction): I₂ + 2e⁻ - à 2I - E ° = +0.620 V / SHE Overall reaction: I2 + SO3 2- + 2OH - à 2 I - + SO4 2- + H2O In this case, sulfate ions (SO4) 2- Sulfates are both reaction products and acids. Sulfates have a low affinity for solvation electrons and therefore do not compete with PFASs for solvation electrons.

[0172] Another option available in various embodiments is to include polysulfide species (such as S2) in the reaction solution. -2 This species undergoes oxidation: Anode (oxidation): 2 S2 2- à S4 2- + 2e - E ° = 0.497 V / SHE Cathode (reduction): I₂ + 2e⁻ - à 2I - E ° = +0.620 V / SHE Overall reaction: I₂ + 2S₂ 2- à 2 I - + S4 2- Various embodiments may include electrochemical methods to reduce other photosensitizers that have generated solvated electrons and are thus oxidized back to the original photosensitizer. For example, in some embodiments, irradiation with ferrocyanide Fe(CN)6 at wavelengths shorter than 313 nm is employed. 4- It can be used to generate solvated electrons and ferricyanide anions Fe(CN)6 3- Ferricyanide ions can then be reduced back to ferricyanide anions at the cathode: Fe(CN)6 4- +UV photons → Fe(CN)6 3- + Solvated electrons Fe(CN)6 3- + electrons → Fe(CN)6 4- (Reaction at the cathode) Sulfites can also act as sensitizers, especially at shorter wavelengths (e.g., 222 nm or 185 nm). In this case, solvated electrons and sulfite radicals (SO3) are generated. .- Sulfite radicals can dimerize to form dithionite (S₂O₆). 2 - Or undergo further reactions. Electrolytic reduction of these species can reduce the amount of sulfite required.

[0173] Photoelectrolysis devices can improve the efficiency of PFAS destruction in several ways. As mentioned above, the sensitizer after photooxidation can be electrochemically reduced back to the sensitizer. Photoelectrolysis devices can also reduce the presence of scavenging species. For example, oxygen is a highly efficient scavenger of solvated electrons and interferes with PFAS destruction. Lowering oxygen levels would be useful. Oxygen levels can be lowered by electrochemically reducing oxygen to a less reactive species (such as water). In this case, the electrolysis reaction may occur before and / or during photolysis. Replacing fluorine with hydrogen in PFAS requires two electrons. The reaction mechanism is thought to involve two separate single-electron reduction steps. One of these electrons can be provided through a reaction with solvated electrons, and in an electrolysis device, the second electron can be electrochemically provided.

[0174] In some embodiments, the anode may comprise a semiconductor polymer, such as a metal or carbon electrode, on a conductive substrate. For example, a metal (e.g., Al) oxidized to a dimagnetic species having an empty d-shell can be used. 3+ ), or metals of diamagnetic species filling the d-shell (e.g., Zn). 2+In some embodiments, a polymeric semiconductor may be coated on the anode to prevent the diffusion of potential scavenging species that may compete with destructive PFASs. For example, the anode may be coated with an oxidizable entity. Examples of oxidizable entities that may be used in various embodiments include π-conjugated polymers, including, but not limited to, polyacetylene, polyaniline, polythiophene, polypyrrole, poly(p-phenylenevinylene), and derivatives thereof, as well as polymers based on reduced forms of n-type semiconductor polymers or blends thereof. Examples include, but are not limited to, polymeric quinone (PQ), poly(5-amino-1,4-naphthoquinone) (PANQ), poly-(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM), polyanthraquinone sulfides (PAQS), poly(2-vinylanthraquinone) (PVAQ), polymerically bonded pyrene-4,5,9,10-tetraone (PPYT), naphthalene diimide (PNDI) derivatives, pyromellitic diimide (PPMDI) derivatives, polylactam / lactone derivatives, polymeric isoindigo (IIG) derivatives, polymeric diketone pyrrolopyrrole (DPP) derivatives, and receptor-receptor derivatives. Another example includes polymers with oxidizable side groups comprising, but not limited to, ascorbic acid and bases or alkali metal salts of polymeric ascorbic acid, or anthracene, pyrene, and naphthalene. In some embodiments, the anionic form of the semiconductor can be via an alkali metal cation (Na₂O₃). + K + 、Rb + ) or alkali metals (Mg) 2+ Ca 2+ Ba 2+ The charge balance is achieved by either a tetraalkylammonium cation or a tetraalkylammonium cation. The cation is released into solution when electrons are removed from the reduced form of the semiconductor. Some of the above species undergo irreversible reactions, but others can be electrochemically reduced back to an anionic state. In the case of all polymers with side units, the connection between the polymer backbone and the side groups should generally not be hydrolyzed under photolytic conditions at high pH (>9). Examples of polymers that can be used in various embodiments are as follows: Figure 10 and 11 As shown. Figure 12 Examples of polymer n-type organic semiconductor structures that can be used in embodiments of this disclosure are shown.

[0175] In some embodiments, the anode can be housed in a UV-opaque material while still allowing contact with the irradiated wastewater. When organic semiconductor molecules are part of the anode, this can be beneficial in preventing unwanted photolysis reactions that could lead to the decomposition of the organic semiconductor and in the introduction of unwanted byproducts that could react with solvated electrons.

[0176] Other possible materials that can be coated or incorporated into the anode in the various embodiments are oxidizable polyols and sugars. Polyols or sugars can be oxidized to aldehydes, ketones, carboxylic acids, or carbon dioxide. In polyols or sugars, they may be consumed and may be considered sacrificial reducing agents. An example of a polyol that can be used in the various embodiments is polyvinyl alcohol.

[0177] In some embodiments, the oxidizable unit may be attached to a polymeric alcohol, such as polymerically bound ascorbic acid, wherein the disodium salt is oxidized to the corresponding dehydroascorbic acid form, and sodium is released into the solution, for example... Figure 13 The reaction is illustrated. For example, water-insoluble polymers containing ascorbic acid, disclosed in WO2000072959A1, can be used in various embodiments. Such polymers act as antioxidants through the reaction of ascorbic acid units with oxidants present in the environment. If used in a reaction solution, they can subsequently be removed from the solution, for example, by filtration. In some embodiments, similar polymers can be used in conjunction with a UV-ARP process to reduce, for example, molecular oxygen and photosensitizer byproducts as defined above.

[0178] In various embodiments, polymeric ascorbic acid and its derivatives that are stable at high pH can be used. For example, in Figure 14 In the chemical structure shown, the linking group X can be selected from the following: oxygen (-O-), sulfur (-S-), azirmono(-NR1-) (where R1 is hydrogen, alkyl, or aryl), alkylene(-(CR2R3)). n - (wherein R2 and R3 may be independently selected from hydrogen, hydroxyl, alkyl or aryl, arylene, and arylenealkyl), alkylenearyl, amide (-C(O)NH-), or combinations thereof. The polymer may be selected from polyacrylates, polystyrene, polyurethanes, polycarbonates, polyolefins, peptides, polyamides, polyethers, and siloxanes.

[0179] Other examples of polymers with oxidizable units that can be used in various embodiments are sulfur-containing polymers, including, but not limited to, polyether-thioethers and polyethersulfones, for example... Figure 15Those shown. One such example that can be used in various embodiments is a polymer designed for use as a polymeric electrolyte in lithium-ion polymers, such as those reported by Sarapas and Tew (Sarapas, JM and Tew, GN; Poly(ether-thioethers) by Thiol-Ene Click and Their Oxidized Analogues as Lithium Polymer Electrolytes; Macromolecules 2016, 49, 1154-1162).

[0180] Electrodes can be used in various shapes or structures. For example, in some embodiments, the cathode can be a metal wire electrode. In other embodiments, the cathode can be a mesh structure, which can increase the surface area and allow for more efficient capture of light-generated products. The material of such electrodes can include, for example, high-density graphite, platinum, gold, or other non-kinetically reactive conductors. In some embodiments, depending on the pH, metals such as iron, zinc, or aluminum can be used.

[0181] Recycling the sensitizer. For example, as described above, in advanced reduction processes (ARP), solvated electrons are generated by UV irradiation of the sensitizer. A common sensitizer is an iodide; UV light generates solvated electrons and iodine radicals. The solvated electrons react with PFAS molecules. However, two iodine radicals can combine to form iodine, and both iodine and iodine radicals can react with the solvated electrons. Therefore, if the concentration of iodine accumulates, it can impair the destruction of PFAS. One solution that can be used in various embodiments is to include or add millimoles of sulfite to the reaction mixture. The sulfite reduces iodine or iodine radicals back to the iodide. The sulfite eventually reacts to form a sulfate that does not interfere with the photochemical destruction of PFAS. The use of sulfite is a good solution; however, high concentrations of sulfite can also react with the solvated electrons and produce chemical byproducts.

[0182] In alternative embodiments, electrochemical reduction of iodine or iodine radicals can be used to prevent the destruction of PFAS that interferes with their formation. Compared to processes using sulfites as discussed above, the use of electrochemical reduction allows for the use of lower concentrations or no sulfites at all. Although electrochemistry involves the formation of oxide species at the anode, oxidation and reduction can be carried out in separate compartments of the photoelectrolysis apparatus, and therefore the oxide species do not interfere with the destruction of PFAS. For example, as... Figure 16The photolysis and iodine reduction shown may occur in one compartment, while oxidation may occur in separate compartments separated by membranes or ion bridges. If water is oxidized, the compartment can be purged with an inert gas such as argon or nitrogen, which prevents oxygen from entering the compartment where photolysis and reduction are taking place.

[0183] Use such as Figure 9 An example of the system shown is used for the electrochemical regeneration of iodide oxidation. Figure 17 and 18 As shown. At one electrode, iodine radicals generated by the photo-oxidation of iodide are reduced back to iodide. An oxidation process occurs at the other electrode. In an aqueous medium, water can be oxidized to oxygen and provide electrons. Other examples of species that can act as reducing agents include sulfites, iodides, ascorbic acid, or ascorbate salts.

[0184] Solvation of electrons. In some embodiments, the electrochemical system can be used to alter the local pH of the solution, such as... Figure 19 As shown. Electrolysis of water at the cathode leads to an increase in pH. A high pH is generally ideal for the destruction of PFAS via solvated electrons because hydrogen ions (H+)... + The solvated electrons react rapidly with the solvated electrons. The pH near the anode decreases. Therefore, if the solvated electrons are generated near the cathode, they will have a sufficient lifetime to react with PFASs. One possible configuration is a light source that irradiates the semiconductor (e.g., diamond-like carbon or boron-doped diamond) near the cathode. Such a system has the advantage of requiring minimal salt concentration and minimal pH adjustment.

[0185] In some embodiments, boron-doped diamond can be used as an electrode and a source of solvated electrons when irradiated with UV photons of sufficient energy. Hydrogen-terminated diamonds are considered preferred for UV generation because they are materials with negative electron affinity. Electrolysis of water causes an increase in pH around the cathode. Irradiation of boron-doped diamond at the cathode can be used to generate solvated electrons with a sufficiently long lifetime to react with PFAS.

[0186] Doped diamond can be used to generate solvated electrons, and the pores formed on the diamond can be electrochemically reduced. The doped diamond used in various embodiments may have another atom incorporated into the diamond structure during its synthesis.

[0187] For example, in some embodiments, solvated electrons can be generated by irradiating hydrogen-terminated diamond, as described in Liu, G.; Feng, C.; and Shao, P., “Degradation of perfluorooctanoic acid with hydrated electron heterogeneous catalytic system”, *Environmental Science & Technology*, 2022, pp. 56, 6223-6231. In this process, UV light excites electrons from the valence band to the conduction band of diamond. The electrons are emitted into an aqueous solution. The solvated electrons can then react with PFAS. For example, in some embodiments, diamond can be irradiated in one compartment of an electrochemical cell. Another compartment can contain iodide and can be connected to the first compartment via a cation exchange membrane. As photolysis proceeds, the solvated electrons generated by irradiating diamond react with PFAS, and the electron “holes” in the diamond valence band are reduced at the electrodes by the reduction of iodide to iodine. This is an example of a current-driven device. However, iodine will accumulate in the battery and eventually diffuse across the membrane barrier because it is neutral and not hindered by the membrane. An improvement to this is to apply a voltage across both electrodes while irradiating the diamond, causing protons to be reduced to hydrogen at the cathode, resulting in an increase in pH around the cathode. A higher pH at this electrode allows for a longer lifetime of photochemically generated solvated electrons and more time to react with the PFAS. At the electrode in the second compartment, an oxidation reaction occurs. In one embodiment, water can be oxidized to oxygen, which can be removed from the compartment by purging with an inert gas such as argon or nitrogen. Other species can also be added to this compartment to lower the potential. These species include, but are not limited to, sulfites, iodides, ascorbates, ascorbate anions, and easily oxidized metal ions.

[0188] Generation of 185 nm hydroxyl radicals

[0189] In some embodiments, hydrogen gas, for example, can be generated by the electrolysis of water. Hydrogen gas can be used in conjunction with vacuum UV photolysis to significantly enhance the degradation of PFAS.

[0190] Irradiation of an aqueous solution containing PFAS with 185 nm UV light yields moderate degradation of PFAS by generating hydroxyl radicals. However, hydroxyl radicals do not react efficiently with PFAS. Therefore, in some embodiments, irradiation of an aqueous solution of PFAS at 185 nm to form hydroxyl radicals can be used simultaneously with the electrochemical generation of hydrogen gas. In these embodiments, irradiation of water at 185 nm yields the generation of hydroxyl radicals in an aqueous solution of PFAS in the presence of hydrogen gas.

[0191] Under basic conditions, hydrogen reacts with hydroxyl radicals to form hydrogen atoms and water, with the hydrogen atoms generating solvated electrons. This combination of electrochemically generating hydrogen in water and irradiating water with 185 nm light to generate hydroxyl radicals can be used in various embodiments to obtain a more efficient PFAS destruction process.

[0192] Hydrogen is produced by electrolysis according to various embodiments, avoiding the need to separately supply hydrogen to saturate the solution. Besides becoming more complex, such a process would involve the use and storage of highly flammable materials. In contrast, by the electrochemical method of hydrogen production described herein, hydrogen can be produced close to where light is absorbed, for example, less than 2 cm, or between about 0.5 and 2 cm, or about 1 cm.

[0193] For example, in some embodiments, the following can be used: Figure 20 The photoelectrolysis cell is shown. A light source (e.g., a 185 nm light source) can be placed in a test tube or other transparent container and immersed in a PFAS solution. Electrodes can be wrapped around the test tube, for example, about 1 cm away. A voltage sufficient to produce hydrogen can be applied across the electrodes. This electrode is electrically connected to electrodes in separate compartments where oxidation occurs. If water is the reducing agent, oxygen is the product. For example, the electrodes can be meshes. The electrodes can be, for example, platinum, titanium, or stainless steel. In some embodiments, the electrodes can be platinum-coated titanium, for example, a platinum-coated titanium mesh. For example, the cathode can be made of a high surface area structure, such as a mesh or foam, where the electrochemically active surface area is greater than the geometric surface area. Other electrodes described elsewhere in this disclosure can also be constructed in these manner.

[0194] After photolysis is complete, the electrochemical process is reversed by reversing the flow of current, and excess hydrogen can be electrochemically oxidized to produce water.

[0195] Vacuum ultraviolet (VUV) is defined as the portion of the electromagnetic spectrum between 100 and 200 nm. Mercury lamps can emit light at 185 nm in this region. Figure 21 As shown, water absorbs radiation at 185 nm and can be decomposed into hydrogen radicals and hydroxyl radicals with a quantum efficiency of ~0.3; hydroxides also absorb light at 185 nm and generate hydroxyl radicals and solvated electrons with a quantum efficiency of ~0.1. Furthermore, water can absorb 185 nm radiation and form hydroxyl radicals, solvated electrons, and protons with a quantum efficiency of ~0.045.

[0196] In various embodiments, hydrogen can be electrochemically produced by electrolyzing water near the UV light-absorbing area. The consequence of electrochemical hydrogen production at the electrodes is an increase in pH. This system does not require an external hydrogen source. It allows for the construction of simple, inexpensive equipment that does not require the addition of chemicals such as hydrogen or sulfites. Furthermore, any excess hydrogen can react with oxygen after photolysis is complete.

[0197] During the photolysis process, water electrolysis can be continuous or intermittent. At high pH levels (e.g., pH 9–12), intermittent electrolysis may be sufficient, where the primary effect is to provide a high concentration of hydrogen. Continuous electrolysis at neutral pH levels (e.g., pH 6–8) may be preferred because electrolysis raises the pH of the volume surrounding the electrodes. In some cases, pH adjustment is not necessary. However, in some embodiments, such as if the pH is less than about 6, it may be necessary to raise the pH (e.g., by adding alkali).

[0198] The method described above provides a process for destroying PFAS with minimal additives. Therefore, it could be useful as a device for treating drinking water to remove PFAS, for example, as a self-contained unit for domestic use, which can be operated by connecting to a power source (such as an electrical outlet) and a domestic water supply. Alternatively, it can be used in conjunction with an RO system to destroy PFAS rejected by the RO system. Such a system can be deployed in small commercial or residential settings. The main byproducts of the reaction will be free fluoride and hydrogen carbon dioxide, as well as hydrogen and oxygen from the electrolysis reaction. Free fluoride levels can be controlled by treating the water with lime or bone ash. Hydrogen and oxygen can be combined to produce water.

[0199] Non-mobile medium reduction of byproducts. Non-electrochemical methods applicable in various embodiments involve utilizing a polymer as a non-mobile medium to reduce oxidized byproducts of a photochemical reaction back to the original sensitizer (e.g., iodide). The non-mobile medium may comprise, for example, beads or films or other structures having a polymerically bound reducing agent. For example, in the case of iodide as the sensitizer, the oxidized byproducts (iodine radicals, iodine, or triiodide) can react with polymeric ascorbic acid, which can be used as a polymeric binder in various embodiments. In this embodiment, less salt (e.g., sodium sulfite) is required, and the polymerically bound ascorbic acid and its oxidized form can be physically separated from the photolysis reaction. Figure 22The image illustrates one possible configuration. The photolyzed solution is pumped through a container containing a reducing species that can reduce the photo-oxidized sensitizer back to the sensitizer. The polymerized reducing agent is physically separated from the solvated electrons and therefore cannot react with them. For example, the irradiated solution can be pumped through a container containing a material capable of reducing iodine back to iodide. It is also possible to include a plurality of the aforementioned polymeric semiconductors to reduce sensitizer byproducts back to the sensitizer. Preferred semiconductor polymers would be those capable of being chemically or electrochemically regenerated, thus allowing for reuse of these materials in subsequent photolysis runs. Another example of a polymeric medium that can be used in various embodiments to reduce iodine radicals, iodine, or triiodide back to iodide is polymeric ferrocene, such as... Figure 23 The polymers shown are polyvinyl ferrocene or polymers based on the reduced form of n-type semiconductor polymers or mixtures thereof listed above. Alternatively, in some embodiments, the reduction of these species can be accomplished by means of metals (such as zinc, aluminum) or metal alloys. For example, the solution can be pumped through a column containing metal pellets. In the case of metals, metal ions that may be generated by the process should not act as scavengers of solvated electrons.

[0200] Another example of a polymeric free radical scavenger that can be used in various embodiments is a polymer capable of undergoing reduction / oxidation reactions, such as a polymer containing stable free radicals. One example is a polymer having a tetramethylpiperidine 1-oxy (TEMPO) side chain, such as... Figure 24 As shown.

[0201] Oxygen reduction. In some embodiments, the UV reactor may include one or more electrochemical systems for one or more functions (e.g., removing impurities from water, removing or recycling photoproducts, and / or altering local pH). For example, dissolved oxygen in the water may compete with sensitizers for scavenging hydrated electrons and may therefore be removed in some embodiments. Several cathode-driven O2 reduction reactions (ORRs) can be implemented in the electrochemical systems according to various embodiments, such as: O2 + 2H + + 2e - → H2O2 E o = +0.69 V / SHE O2 + 2H2O + 4e - → 4OH - E o = +0.40 V / SHE O2 + 4H + + 4e - → 2H2O E o = 1.23 V / SHE Alternative solvents. In some embodiments, solvents other than water can be used for PFAS destruction. Some such embodiments utilize electrochemistry in polar aprotic solvents to generate highly reduced or oxidized species that can be subsequently photolyzed to generate other highly reactive species. Examples of aprotic polar solvents that can be used in various embodiments include acetonitrile, pyridine, dimethyl sulfoxide, N,N-dimethylformamide, acetone, ethyl acetate, oxalane / tetrahydrofuran, and crown ethers. For example, aromatic species that can be used in various embodiments (such as dicyanoanthracene (DCA)) can be electrochemically reduced to free radical anions (DCA). - ), and is then irradiated to generate even stronger reducing agents, excited-state dicyanoanthracene radical anions (DCA). - Other aromatic species that can be used are 2,6-diisopropylphenylnaphthalene and perylene diimide. Since many radical anions that can be used in various embodiments have absorption in the visible or near-UV region of the electromagnetic spectrum, this method has the potential advantage of allowing the production of very highly reactive species at lower energies (below UV-C). It can also allow for more complete absorption of lamp energy if used in conjunction with higher-energy photons. Examples of processes involving aromatic compounds are as follows... Figure 25 As shown.

[0202] In some embodiments, the photochemical reactor may be equipped with an electrochemical system to decompose other stubborn pollutants such as pharmaceuticals, hormones, pesticides, antibiotics, and detergent solvents.

[0203] Post-processing steps

[0204] After the photochemical destruction caused by PFAS, the ideal approach would be to further treat the solution before final disposal or recycling of the photolysis wastewater. Potential post-treatment solutions include... Figure 26 As shown. In some cases, all of these steps may be necessary. In other cases, only one or a few may be required. Post-processing steps may be performed sequentially, and in some cases, a given process may perform more than one of these functions simultaneously.

[0205] The post-treatment used in various embodiments may depend on the discharge of the treated water. In some industrial settings, reuse or recycling of the water may be ideal. In other cases, the treated water may be returned to the environment. In other cases, the water may be allowed to evaporate or must be incinerated. The goal of post-treatment may be to adjust the water to reuse specifications or to meet regulatory or anticipated regulatory requirements. In other cases, some photochemically treated water may be treated with a membrane, where membrane rejects (water that does not pass through the membrane) are recycled back to the photoreactor for further treatment.

[0206] Figure 26The diagram illustrates the possible post-processing steps. In some scenarios, all the shown steps may be necessary. In many scenarios, only a few post-processing steps will be required. In many embodiments, the pH needs to be adjusted to 6-8.

[0207] Sensitizers are likely the most expensive reagents used in the photoreduction step; therefore, it is ideal to recycle them or materials that can be readily converted into them. When iodides are used as sensitizers, an effective method for capturing iodides is to electrochemically reduce them to iodine or polyiodides in a specific electrode. To recover and reuse the iodides, the captured polyiodides can be reduced electrochemically or chemically from the iodine-containing electrode. To achieve this, it is preferable to lower the pH to between 5 and 8, as iodine and polyiodides readily undergo other reactions at higher pH levels. Excess sulfites may potentially reduce the efficiency of the electrochemical reaction; therefore, steps involving the destruction or removal of sulfites prior to sensitizer recycling may also be preferred.

[0208] For some applications, recycling iodide may be uneconomical, but it may still be necessary to remove iodide from the final treated water. In such cases, adjusting the pH and then passing the solution through one or more anion exchange media can remove iodide, fluoride, sulfite, or sulfate. A final refurbishment step (e.g., GAC treatment) can then be used to further reduce iodide levels, for example, to meet water specifications or regulatory requirements for recycling.

[0209] In some embodiments, all anionic components, including sulfites, iodides, sulfates, and fluorides, can be removed simultaneously by an anion exchange medium with or without pH adjustment, such as by means of direct purifying photochemically treated water.

[0210] In some embodiments, the photochemically treated water can be removed by an evaporation process (e.g., thermal evaporation or spray drying), and the ions and their salts can be recovered and reused by precipitation.

[0211] Potentially lower-cost but more time-consuming post-treatments that can be used in various embodiments involve lowering the pH by adding lime and allowing solids to settle and clarify, followed by precipitation, such as for fluoride and sulfate. The clarified water can then be treated with a final polishing step, such as through a GAC ​​bed or by RO.

[0212] To return PFAS-containing water to the environment, these molecules must be removed to appropriate levels to comply with current regulations regarding the permissible concentrations of certain PFAS molecules. Photoreduction processes may successfully destroy most regulated PFAS; however, small amounts of new PFAS and polyfluorides may be generated. Currently, there are no specific restrictions on these molecules. In the future, regulations may change to include these materials. One option for eliminating these materials, available in various embodiments, is by performing a thermal oxidation process followed by persulfate as a post-treatment step. Alternatively or additionally, electrolytic processes can be used to reduce or eliminate these materials. Another method available in various embodiments, alternatively or additionally, is nucleophilic substitution of fluorine atoms from these molecules to increase the amount of free fluorides and reduce the levels of PFAS and polyfluoride species. These post-treatments can result in the near-complete destruction of materials containing carbon-fluorine bonds.

[0213] Various UV-ARP processes can be carried out at highly corrosive high pH levels. Therefore, in some embodiments, post-treatment solutions may involve lowering the pH to 6-8 by adding acid. Besides reducing the corrosivity of the solution, some subsequent post-treatment steps are more effective at lower pH levels.

[0214] Various UV-ARP processes utilize sensitizers and sacrificial electron donors. For example, the sensitizer used for UV-ARP at 254 nm is an iodide, and the sacrificial donor may be sulfite. At shorter wavelengths (e.g., 254 nm and 185 nm), sulfite can also be an effective sensitizer. Excess sulfite can be converted to sulfate by oxidation with air, oxygen, or peroxides or electrochemical oxidation. UV light can be used to accelerate the oxidation of sulfite to sulfate. However, as discussed above, sulfite may hinder the recovery and reuse of iodide species, such as iodine, triiodide, or other polyiodides. Therefore, in some embodiments, it is preferable to reduce or eliminate sulfite before electrochemically recovering and reusing iodide species from the post-treatment solution.

[0215] Sensitizers are often the most expensive reagents in ARP. Iodide salts are frequently used as sensitizers. Therefore, methods for recycling and reusing iodides (such as those disclosed above) are desirable.

[0216] Iodine recovery and reuse. In some embodiments, iodides can be recovered and reused via iodide-specific anion exchange membranes (AEMs). In some embodiments, the AEMs can be used in conjunction with electrochemical cells for iodine-iodide recycling and reuse.

[0217] In some embodiments, photolysis conditions may require high pH, ​​a sensitizer, and one or more inorganic salts. The photochemical destruction of PFAS results in the formation of fluoride ions. Further processes can be used to treat water and recycle high-value materials. For example, in an embodiment where an iodide is used as a sensitizer, the iodide may be oxidized to iodine, which is relatively insoluble in water. Iodine can be precipitated and recycled by filtration. However, in some cases, the iodine concentration is low enough that all the iodine remains in solution. In this case, the precipitation process would be ineffective. Furthermore, iodine is unstable at high pH. Therefore, some embodiments may also include lowering the pH to between 3-8 or 5-7 to more fully recycle iodine. The pH can be lowered by using a suitable acid, such as an inorganic acid.

[0218] Sulfites can also reduce iodine back to iodides. To enable the recycling and reuse of various chemical forms of photosensitizer species (such as iodides), separation processes can be employed to isolate the photosensitizer from other components (such as sulfites). These processes include, but are not limited to, ion-exchange membranes, ion-selective resins, and size exclusion materials.

[0219] In some embodiments, such as those where sulfites are present, post-processing can be performed to convert sulfites to sulfates. For example, sulfites can be converted to sulfates by adding a suitable oxidant to the reaction solution after UV treatment. Examples of oxidants that can be used in various embodiments include, for example, air, oxygen, and / or hydrogen peroxide. In some embodiments, oxygen or air may be preferred because they oxidize sulfites but not iodides, and therefore can be used in excess concentrations. In some embodiments, other oxidants may be used alternatively or additionally to selectively remove sulfites. In some embodiments, the post-photolysis process of converting sulfites to sulfates can be accomplished or accelerated by adding a catalyst or electrochemically.

[0220] In some embodiments, iodine species can be recovered and reused by adding a tetraalkylammonium salt (such as tetraalkylammonium hydroxide), which directly precipitates iodide ions to form tetraalkylammonium iodide. In other embodiments, iodides can be removed by complexing with quaternary ammonium or other cationic polymers. Furthermore, cationic polymer materials can be mixed with the electrode coating. However, quaternary ammonium cations may be readily degraded under strongly alkaline conditions because they tend to undergo Hoffmann elimination in other degradation pathways. Therefore, the cationic unit can be selected from those units that have proven stable. These units include, but are not limited to, alkyltrimethylammonium cations (where the alkyl chain is longer than 4 carbons), cyclic ammonium cations, and imidazolium cations. Other usable cationic centers include phosphonium, cobaltene, and ruthenium cations.

[0221] In some embodiments, after the sulfite is converted and / or removed, the iodide may be oxidized to precipitated iodine. The precipitated iodine can then be collected. In some embodiments, the iodine may be electrochemically precipitated in a removable module, or the iodine may be recycled and then reused. A similar reaction sequence can be used to recycle pseudohalogen species, which may be oxidized to neutral, aqueous-insoluble species.

[0222] Various embodiments include processes for allowing efficient degradation of PFAS materials, including the use of electrochemical systems to convert reaction products of the UV sensitizer back into the original sensitizer. For example, in some embodiments, iodine species can be recovered and reused from the photolysis solution by electrochemical means.

[0223] For example, some methods for recovering and reusing iodine species from aqueous solutions involve the electrochemical oxidation of aqueous solutions containing iodides to iodine species, such as triiodide ions or other polyiodide anions. Polyiodides are a class of anions composed entirely of iodine atoms. The most common member is the triiodide ion, I... - 3. Other known polyiodides include [I4]. 2- [I5] - [I6] 2- [I7] - [I8] 2- [I9] - 、[I 10 ] 2- [I] 10 ] 4- [I] 11 ] 3- [I] 12 ] 2- [I] 13 ] 3- 、[I 14 ] 4- 、[I 16 ] 2- 、[I 22 ] 4- [I] 26 ] 3- [I] 26 ] 4- [I] 28 ] 4- and [I 29 ] 3- All of these could be caused by I - I2 and I - It is formed by the interaction of the three components.

[0224] In some embodiments, the electrochemical oxidation of iodides may involve the use of a iodophilic electrode, such as an electrode comprising: 1) a iodophilic material having an affinity for iodides, iodine, or polyiodides; 2) a conductive material; and 3) a binding material providing mechanical and chemical integrity to the electrode. The iodophilic material may be, for example, anion exchange resins that form iodides or polyiodides, starch, and / or inorganic or organometallic complexes. The conductive material may be, for example, graphite, graphene, carbon nanotubes, and / or conductive polymers or metals. The iodophilic material may be present in the combined electrode material in the range of about 20% to about 70%. The conductive material may be present in the combined electrode material in the range of about 10% to about 60%. The binding material may be present in the combined electrode material in the range of about 20% to about 50%. For example, in some embodiments, the iodophilic material may be about 35% to about 60% of the electrode material, the conductive material may be about 20% to about 50% of the electrode material, and the binding material may be about 30% to about 50% of the electrode material.

[0225] During post-treatment, iodine-containing species present in solution during the post-treatment period following UV-ARP can be concentrated and immobilized using iodophilic materials. Conductive materials can be used to allow efficient electron transport throughout the electrode composition. Binders can be used to provide chemical and mechanical integrity to the electrode. In some embodiments, conductive materials that act as both conductors and binders can be used. In some embodiments, iodophilic materials that are also conductive, such as conductive polymers (e.g., polyaniline), can be used. In these embodiments, the electrode may contain only two components.

[0226] Binder materials provide mechanical integrity to the electrode, thereby supporting electrochemical processes. Iodophilic and conductive materials can be, for example, organic or inorganic powders, thus requiring binder materials (e.g., polymers) to maintain the structural integrity of the electrode and ensure the continuity of the electronic network by binding the active material and conductive additives together. In addition to binder materials (e.g., polymers that hold the active material and conductive agent together), they can also serve to adhere the electrode to a current collector. Furthermore, by providing good mechanical integrity to support conductivity, binder materials can promote the formation of electronic and ionic circuits to safeguard electrochemical reactions. Iodophilic electrodes can be freestanding structures (electrically connected but without a current collector) or attached to or connected to a current collector.

[0227] Examples of usable binder materials include, but are not limited to, polyvinylidene fluoride (PVDF) and / or styrene-butadiene rubber (SBR). PVDF can often be synthesized via emulsion polymerization or suspension polymerization processes; for example, commercially available materials HSV900 (from Arkema) and 5130 (from Solvay) are produced by these two methods, respectively. Other examples of usable binder materials include polytetrafluoroethylene (PTFE). Many binders used in lithium-ion battery cathode structures can also be used in this application.

[0228] The purpose of using iodophilic materials with high affinity for iodine / iodides / polyiodides in electrodes is to interact with some or all of the iodide species in the treatment solution and immobilize them within or on the electrode. These iodine-containing species can exist in equilibrium with each other. Therefore, materials that can interact with iodine, iodides, or polyiodide species can be useful. For example, anion exchange membranes can be effective for capturing iodides. Anion exchange membranes are cross-linked polymers with low solubility. Iodine is a Lewis acid and therefore can form complexes with electron donors.

[0229] One method to reduce the solubility of various iodophilic polymers in aqueous media is by crosslinking the material. Many polymers can be used; for example, starch and other polymeric sugars are known to have a strong affinity for capturing triiodide anions. Starch can be crosslinked with epichlorohydrin or 2,3-epoxypropyltrimethylammonium chloride. For example, in some embodiments, the membrane material may help capture iodide at the electrode, where it can be reduced. In some embodiments, starch that can be crosslinked to be water-soluble can be used.

[0230] Iodine forms a strong iodine complex with the cross-linked cationic starch derivative N-(2-hydroxy)propyl-3-trimethylammonium chloride, and this material can be used as a iodophilic material in various embodiments. For example, the starch can be cross-linked starch, or it can be cross-linked during ball milling or formulation steps. Other iodophilic materials that can be used in various embodiments include cross-linked polyvinyl alcohol (PVAs), chitosan, cellulose, some derivatives of cellulose, cross-linked copolymers of N-vinylpyrrolidone (N-VP), and / or copolymers of polyethylene glycol. Water-soluble chitosan can be used, the solubility of which is determined or adjusted by the degree of deacetylation, pH, and crystallinity. One consideration in choosing a iodophilic material is its limited solubility in aqueous solutions over the time span of the electrodeposition process.

[0231] Other possible materials with a high affinity for iodides that can be used in various embodiments of the iodophilic material include metallocenes, such as ferrocene and its substituted derivatives, or polymeric ferrocene (e.g., polyvinyl ferrocene), all of which form triiodide salts. In other embodiments, materials used in organic semiconductors (e.g., polythiophene, polypyrrole, and polyaniline, which can form polyiodide salts) can also be used as iodophilic materials. A iodophilic material that can be used in electrodes or combinations of two or more materials (e.g., those listed herein) can be used in various embodiments.

[0232] Various systems and methods can utilize iodophilic electrodes to recover and reuse iodine species from aqueous solutions in which iodides act as photosensitizers in advanced reduction processes (ARPs) that generate solvated electrons to destroy PFAS compounds. These systems and methods are particularly useful for cost reduction, as photosensitizers are typically the most expensive reagents in UV-ARP processes. Using iodide recovery and reuse electrodes allows for the isolation of iodides from other photochemical byproducts and their reuse in additional subsequent cycles of UV-ARP with different batches of wastewater.

[0233] Unlike other methods of iodine recovery and reuse used in other settings (e.g., by using polyhalogenated ion exchange resins of bromine or chlorine), as taught in this disclosure, using a iodophilic electrode to recover and reuse iodine does not require the addition of such additional highly reactive species. Similarly, methods of halide recovery and reuse using electrochemical oxidation result in the precipitation of iodide at the electrode, where it is then collected as a solid. In contrast, the process disclosed herein using a iodophilic electrode allows for the capture of iodide / triiodide / polyiodide within the electrode volume. The electrode can then be removed, and the iodide can be released by electrochemical reduction using a current in the opposite direction.

[0234] This system and method can be used for post-treatment solutions of any iodide concentration, but lower concentrations may result in lower oxidation rates and therefore require longer electrolysis times. Iodide concentrations above 1 mM are preferred. In some embodiments, anion exchange materials can be used to concentrate the iodide near the electrode. In some embodiments, the iodine capture time can be reduced by increasing the surface area of ​​the electrode. Molecular iodine, and therefore triiodides and polyiodides, are more readily formed at neutral and acidic pH levels, so operating at pH below pH 9 is preferred. Various embodiments involve adding acid to the treatment solution having an alkaline pH to bring the pH of the treatment solution below about 9, for example, between about 4 and about 9, or between about 5 and about 9. It is also useful if the post-treatment solution containing iodide has sufficient conductivity to minimize the overpotential required for iodide oxidation. Therefore, in various embodiments, a total electrolyte concentration above about 10 mM is preferred, and higher concentrations (e.g., above about 100 mM) can facilitate rapid iodide oxidation. If the solution does not already contain a sufficient electrolyte concentration, an electrolyte that does not interfere with the oxidation reaction can be added. For example, various embodiments may include the addition of suitable electrolytes, such as Na2SO4, K2SO4, NaCl and / or KCl, etc., to improve conductivity before using iodophilic electrodes to recover and reuse iodides.

[0235] When preparing treated solutions for iodide recovery and reuse, it may not be necessary to adjust the pH for iodine stability since iodides are stable at all pH values. However, depending on the electrode composition, pH can affect the electrode's chemical stability. While many conductive and binding materials used in electrodes may have good chemical stability, iodophilic materials used in electrodes may be pH-sensitive, and therefore may need to be adjusted depending on the choice of iodophilic material and the pH of the treated solution. In some embodiments, iodophilic electrodes can be used in treated solutions with a near-neutral pH (e.g., from about 6 to about 8) to provide good chemical stability. The treated solution can be adjusted to this pH range by adding an acid or base prior to post-treatment with the iodophilic electrode.

[0236] In various embodiments, to avoid competition from water oxidation and water reduction, the iodophilic electrode can operate within a voltage range where neither water oxidation nor water reduction is present. For example, in solutions with a pH of approximately 7, a voltage range of approximately -1.0 to approximately 1.2 V (relative to Ag / AgCl) is suitable and can be used in various embodiments. When the solution has a higher pH, the voltage range used may shift by -0.059 V for each point increase in pH. When the solution has a lower pH, the voltage range used may shift by +0.059 V for each point decrease in pH.

[0237] For example, electrodes can be used under constant current or constant potential conditions. In methods and systems using constant current operation, a constant current is applied to the electrodes, ranging from 0.1 to 10 mA / cm². 2 The range is suitable for oxidation, and is from -0.1 to -10 mA / cm. 2 This can be used for reduction to balance rate and efficiency, although alternatively, lower or higher ranges can be used. For example, the reaction can continue until the total charge passing through is sufficient to substantially or completely load / unload the electrode, and then can be stopped. Alternatively, for example, the reaction can continue until the voltage reaches an interruption limit set before the reaction began, for example, to avoid oxidation or reduction of water, and then can be stopped. In potentiostatic operation, a constant potential can be applied to the electrode. A potential sufficient to oxidize iodide to triiodide / polyiodide can be selected, without causing oxidation of water at the anode, and a potential sufficient to reduce triiodide / polyiodide to iodide without causing reduction of water at the cathode can be selected, as described above.

[0238] The aforementioned electrode can be part of an electrochemical device. This device may include an anode chamber containing iodide, such as iodide in a post-UV-ARP treated solution, and a cathode chamber not containing iodide separated by a cation exchange membrane. In the anode chamber, an oxidation current is applied to the electrode, and the iodide is oxidized to triiodide / polyiodide, which is immobilized within the electrode. In the cathode chamber, a cathode current is applied to an iodide-capturing electrode already loaded with triiodide / polyiodide, causing the triiodide / polyiodide to be reduced back to iodide, which is then released into the solution.

[0239] Various embodiments of the battery include a dual-electrode system in which an unloaded iodide trapping electrode serves as the anode and a loaded iodide trapping electrode serves as the cathode. Figure 27An example of an electrolytic system for the recovery and reuse of iodine is shown. This example comprises a dual-electrode system in which an iodide recovery and reuse electrode is used for both the cathode and the anode. In this system, a previously loaded triiodide / polyiodide electrode is used as the cathode, and an empty iodide recovery and reuse electrode is used as the anode. The cathode is placed in an iodide recovery and reuse solution that is iodide-free at the start of electrolysis. The anode is placed in an iodide-containing solution. A current is applied to the electrodes from an external power source, causing the triiodide / polyiodide to be reduced to iodide at the cathode and the iodide to be oxidized to triiodide / polyiodide at the anode. During electrolysis, the iodide concentration in the cathode chamber increases as it is released from the cathode, and the iodide concentration in the anode chamber decreases as it is stored in the anode as triiodide / polyiodide. When the reaction is complete, electrode B will be depleted of triiodide / polyiodide and placed in a new iodide-containing solution, where it will act as the anode. Electrode C will be fully loaded with triiodide / polyiodide and placed in a new iodide recycling solution, where it will act as the cathode. In this way, iodide is recovered and reused from the iodide-containing solution.

[0240] Various embodiments of the battery also include a three-electrode system in which an iodide recycling electrode is used as the working electrode (WE), a stable metal (e.g., Pt, Ir, Ti, etc.) is used as the counter electrode (CE), and Ag / AgCl is used as the reference electrode (RE), although other materials, such as calomel electrodes or Hg / HgO electrodes, may be used alternatively. In such a system, the iodide recycling electrode is first used as the anode in an iodide-containing solution (e.g., a solution after UV-ARP treatment), where a controlled voltage is applied between the WE and RE to oxidize the iodide to triiodide / polyiodide. Both the CE and RE are in water, and the CE will undergo water reduction to balance the current. When the iodide recycling electrode is loaded with triiodide / polyiodide, the WE chamber is switched to an iodide-free solution. The WE is then used as the cathode to reduce the fixed triiodide / polyiodide back to iodide, which is released into the recycling solution. The CE will then undergo water oxidation. Sacrificial oxidants (such as O2) and reducing agents (such as sulfites) can be added to the CE chamber to reduce the required battery voltage.

[0241] In some embodiments, alternative iodophilic electrodes can be used. The electrode can be a bilayer electrode having a first layer and a second layer, the first layer being formed of a conductive material, and the second layer being in contact with the first layer, wherein the second layer adsorbs triiodide ions, and wherein the triiodide ions are reduced at the interface between the first and second layers. The first layer can comprise a two-dimensional carbon structure, such as graphene or carbon fiber cloth. The second layer can comprise at least, for example, polypyrrole, polyaniline, or poly(3,4-ethylenedioxythiophene).

[0242] Various embodiments include iodide / iodine / triiodide / polyiodide specific electrodes, and methods and apparatus for capturing and / or recovering iodide / iodine / triiodide / polyiodide from aqueous media, such as capturing and recycling iodide / iodine / triiodide / polyiodide back into a photochemical reactor for reuse in UV-ARP.

[0243] In some embodiments, iodine can be recovered and reused from a post-treatment solution by passing the solution through a module containing anion exchange medium that complexes with iodide. This step can be performed, for example, after pH adjustment and sulfite removal as discussed above. The pH can be lowered to, for example, a range of about 4 to about 9, or about 5 to about 9, by adding acid.

[0244] In other embodiments, the anion exchange membrane can be used to recover and reuse iodides. For example, strong anion exchange resins containing quaternary ammonium groups can be used in various embodiments. Two types of anion exchange membranes that can be used comprise type I and type II resins, with type I resins containing trialkylammonium chloride or trialkylammonium hydroxide, and type II resins containing dialkyl-2-hydroxyethylammonium chloride or dialkyl-2-hydroxyethylammonium hydroxide. Some examples of these resins are Dowex 1X2, Dowex 1W4, Dowex 1X8, Dowex 2X8-100, 2X8-200, and 2X8-400. Weak anion exchange resins lacking exchangeable ions can also be used.

[0245] For example, in some embodiments, after photolysis, the pH can be adjusted, and the solution can then be passed through or flowed through an ion-exchange membrane, where the iodide binds to the membrane. The iodide can then be released by following a salt solution (e.g., sodium chloride solution) through the membrane to release the iodide back into the solution. The solution containing the released iodide can be added to the reactor in UV-ARP for reuse. Therefore, the salt is chosen so that it does not interfere with subsequent photochemical reactions. Suitable salts that can be used in various embodiments include, for example, sodium chloride, sodium bromide, potassium chloride, potassium bromide, sodium hydroxide, potassium hydroxide, and / or sodium sulfate. Unsuitable salts may contain species that have a high affinity for solvated electrons or strong absorption in the UV between 180 nm and 400 nm. Sodium nitrite and sodium nitrate are two examples of salts unsuitable for displacing iodides because nitrates absorb in the UV and react with solvated electrons.

[0246] The concentration of the salt solution can be chosen to be high enough to release the iodide back into the solution. The affinities of Type I and Type II resins for various anions are known. The necessary salt concentration can be determined by relating the relative affinities for the iodide and the selected salt and then comparing it to the iodide concentration of the starting solution.

[0247] PFAS removal. In some embodiments, where further reduction of PFAS concentration is required before the release of treated wastewater, for example, to meet stringent EPA restrictions, the photochemically treated liquid may undergo one or more further post-treatment processes to further reduce PFAS levels. Some processes that can be used to further reduce PFAS concentrations are granular activated carbon (GAC), ion exchange, or reverse osmosis. In some embodiments, the ion exchange resin may be regenerable. However, the presence of high concentrations of ions can affect the efficiency of these processes.

[0248] Even after the acidification, oxidation, and iodine recovery and reuse steps, high concentrations of fluoride ion species and possibly sulfates may still remain in the solution. Therefore, in some embodiments, the concentrations of these sulfates and fluorides can be reduced by adding alkaline earth species to the post-treatment solution. These may include, for example, calcium or barium compounds. In some embodiments, the use of calcium compounds may be preferred, for example, for economic reasons. Suitable calcium compounds include calcium hydroxide and / or calcium oxide. Alkaline earth ions can react with fluorides and sulfates to form minerals such as fluorite (CaF2) and CaSO4 (anhydrite) or CaSO4·2H2O (gypsum) that may precipitate from the solution. In some embodiments, fluorides can be precipitated, for example, by adding hydroxyapatite to form fluorapatite precipitate. Solid precipitation can then be allowed, and the supernatant can undergo further processes to remove residual PFASs. Alternatively, in some embodiments, solids can be removed by electrocoagulation, thereby altering the surface charge of the suspended particles and resulting in the agglomeration and precipitation of the solid matter.

[0249] In some embodiments, unreacted target PFAS molecules can be treated by an adsorption process and reintroduced into the photolysis process.

[0250] Even after most PFASs are destroyed, some partially fluorinated organic species may still remain. Non-limiting examples of partially fluorinated organic species include the following: fluoroacetic acid, difluoroacetic acid, 2-fluoropropionic acid, 2,2-difluoropropionic acid, 1,2-difluoropropionic acid, 1,1-difluoropropaneic acid, 2,2,2-trifluoropropionic acid, 1,2,2-trifluoropropaneic acid, 1,1,2-trifluoropropionic acid, 1,2,2-tetrafluoropropionic acid, 1,1,2,2-tetrafluoropropionic acid, monofluorosubstituted butyric acid, difluorosubstituted butyric acid, trifluorosubstituted butyric acid, tetrafluorosubstituted propionic acid, pentafluorosubstituted butyric acid, hexafluorosubstituted butyric acid, and various isomers of other partially fluorinated pentanoic acid, hexanoic acid, heptanoic acid, and octanoic acid. These partially fluorinated organic species constitute a percentage of the remaining fluorinated species, as measured by total organic fluorine analysis. Some partially fluorinated species are considered toxic. Therefore, the wastewater can be further treated after photolysis to reduce or remove any remaining partially fluorinated species. In some embodiments, prolonged UV irradiation and ARP will sufficiently reduce the concentration of these species; however, this may result in inefficient use of the photochemical reactor. Therefore, post-treatment of the reaction mixture is another means of reducing or eliminating these species. In various embodiments, the post-treatment may comprise one or more various oxidation processes. Potential oxidants that can be used include, for example, various organic peroxides (e.g., and inorganic oxides (e.g., peroxides, persulfates, bleaching agents) and various transition metal oxidants (e.g., permanganates). In some embodiments, UV irradiation and / or heating may be used to accelerate these post-treatment reactions.

[0251] Partially fluorinated organic species may be more readily subjected to substitution reactions than PFASs. Therefore, various nucleophiles can be added to disrupt some of these species. In various embodiments, nitrogen- or sulfur-containing nucleophiles can replace fluorine. Some non-limiting examples of sulfur nucleophiles that can be used in various embodiments include, for example, hydrogen sulfides and their salts, thiols (RSH), thiols anions (RS... - ), Thiocarboxylic acid anion (RC(O)-S) - ), where R is an alkyl, aryl, or aralkyl group; and xanthate anion (RO-C(S)-S - ) and dithiocarbamate anion (R2N-C(S)-S - ), where R is an alkyl, aryl, or aralkyl group; and thiosulfate (S2O3) 2- Some non-limiting examples of nitrogen-containing nucleophiles that can be used in various embodiments include ammonia, amines, hydroxylamine, hydrazine, carbazide, phenylhydrazine, aminourea, and amides. For example, these can be mixed with a post-treatment solution, and the mixture can then be heated (e.g., in an autoclave).

[0252] Effluent from post-treatment may still contain contaminant species that cannot be released into the environment without treatment. Therefore, after photoreduction, the effluent can be collected to test PFAS. Depending on requirements and the amount of remaining PFAS, the effluent may undergo further treatment. For example, additional treatment may be used to remove remaining contaminants down to permissible levels. For instance, in some embodiments, systems and methods may include additional systems downstream of the UV photoreduction system, such as using one or more reverse osmosis (RO), nanofiltration (NF), microfiltration (MF), ultrafiltration (UF), ion exchange resins (IXR), or granular activated carbon adsorption (GAC), either alone or in combination. Furthermore, these techniques can be used to optimize scenarios where the disruption process is operated for a shorter period and the effluent is concentrated using the post-treatment methods listed above. This configuration will enable shorter residence times and higher yields during disruption while still maintaining process effluent targets.

[0253] The photochemical degradation of PFAS is a sequential process. Several mechanisms are believed to be responsible for PFAS degradation. One mechanism involves the substitution of fluorine atoms on PFAS with hydrogen atoms. Another mechanism involves the loss of carboxylate or sulfonate head groups, followed by hydrolysis and chain shortening. The resulting new molecules (daughters) also contain fluorine-carbon bonds. These daughter molecules can undergo further photochemical degradation. Some of these molecules are also PFAS molecules, and while not necessarily regulated, their removal may be desirable or necessary in the future.

[0254] The amount of fluoride ions generated is a measure of the effectiveness of the destruction of PFAS molecules and their progeny. The defluorination percentage (deF%) can be defined as the proportion of fluoride ions generated relative to the total number of fluorine atoms in all PFAS molecules. For example, in some photochemical processes, the total defluorination level may be ~70-90%. This means that in such cases, up to 10-30% of the fluorine remains bound to carbon.

[0255] Post-treatment to remove these molecules can involve multiple processes. For example, in some embodiments, persulfate can be used to oxidize partially defluorinated PFAS molecules, which may result in complete or near-complete defluorination. For example, the oxidation processes described above for pretreatment can also be used for post-treatment. Alternatively or additionally, in some embodiments, electrochemical oxidation can be used to increase the overall defluorination level.

[0256] In some cases, reducing photolysis time can be advantageous, allowing for shorter time in the photoreactor and relying on post-treatment defluorination steps to achieve high levels of PFAS destruction. For example, a combination of reduced photolysis time and post-treatment defluorination may be more efficient and / or may achieve higher levels of PFAS destruction than photolysis alone, which might require longer processing times and the use of more energy-intensive processes to achieve the same results.

[0257] Fluoride ion reduction. As discussed earlier in this disclosure, fluoride ions are a product of photochemical degradation of PFAS. While some concentrations of fluoride ions in water are acceptable, high concentrations are undesirable. High fluoride concentrations can lead to health problems and interfere with the function of ion exchange resins or granular activated carbon beds.

[0258] Following the photochemical (e.g., direct or reductive) decomposition of PFAS, fluoride ion concentrations can be reduced through various means. Some effective methods applicable to various embodiments include reverse osmosis and adsorption using material columns (e.g., specialized bone char carbon filter media or activated alumina). Bone char, also known as brimac, which can be used in various embodiments, is prepared by washing and drying animal bones and then heating them to ~700°C in an oxygen-free environment. The resulting material is a porous material with a high surface area and consists of calcium phosphate, calcium carbonate, and carbon.

[0259] In various embodiments, fluorides can be removed from the post-treatment solution by precipitation. One example of a precipitation process that can be used in various embodiments includes the following steps: 1) adding a material to the fluoride-containing solution that causes the fluoride to mineralize into fluorite CaF2 or fluorapatite Ca5(PO4)3F, 2) allowing the minerals to settle, and 3) removing the supernatant from the settled solids. Alternatively, the precipitated fluoride minerals can be removed by filtration. In other embodiments, alum can be added to the fluoride-containing solution to coagulate the fluoride. In this way, fluorite can be locked into an insoluble solid mineral. In still other embodiments, magnesium hydroxide can be added to the fluoride solution to absorb the fluoride. The resulting fluorite is non-toxic and can optionally be used in other processes, such as the production of PFAS.

[0260] In some embodiments, the fluoride may precipitate as fluorite (CaF2) or fluorapatite Ca5(PO4)3F. For example, the following materials may be added to a solution containing fluoride to cause precipitation: 1) quicklime Ca(OH)2, 2) a combination of water-soluble calcium salts and phosphates to produce hydroxyapatite, 3) hydroxyapatite powder, or 4) bone char powder.

[0261] The fluoride treatment methods disclosed herein can be used independently or in combination with these or other methods.

[0262] Sulfate precipitation. Sulfites are often used in ARP. Some sulfites are converted to sulfates during the photochemical process. After photolysis, the remaining sulfites can be converted to sulfates as discussed above. For example, many treatments used in various embodiments to precipitate fluorides as fluorite can also be used to cause sulfate precipitation as gypsum (CaSO4). .(2H₂O). In some embodiments, fluorite and gypsum can precipitate together. Gypsum can be removed simultaneously with fluorite using the same procedure listed above for removing fluorite or fluorapatite. Removal of these minerals reduces the concentration of free ions in the solution.

[0263] Fine processing steps

[0264] Even after one or more post-treatment steps, the effluent from the post-treatment may still contain contaminant species that would otherwise be unsuitable for release into the environment without further treatment. A filtration step, which may serve as a final treatment unit, can be useful or necessary for removing any residual contaminants, e.g., reducing them to below an ideal threshold for permissible levels. Various filtration methods can be incorporated downstream of one or more post-treatment units and may include steps such as reverse osmosis (RO), ion exchange resins (IXR), granular activated carbon beds, and / or membrane filtration. The filtration step can be viewed as a separate step or as an additional post-treatment step. In some embodiments, filtration may be performed after photolysis and post-treatment steps to bring the levels of one or more components in the wastewater below limits, such as regulatory limits required for releasing the treated wastewater into the environment.

[0265] like Figure 28 The block diagram shows an example of a method for processing PFAS by performing a fine-tuning step after the subsequent processing steps are completed.

[0266] The embodiments disclosed herein include, but are not limited to, the following: Various embodiments include ultraviolet photolysis reactors equipped with one or more electrochemical systems capable of reducing photochemical byproducts. For example, in some embodiments, a photoreactor for destroying PFAS comprises an ultraviolet light source configured to deliver 222 nm light and a reactor vessel configured to contain an aqueous solution containing PFAS, wherein the light source is positioned to direct the light to the solution contained in the reactor vessel. The light source may be a krypton / chlorine excimer lamp. Optionally, there may be a second or more light sources, the same as or different from the first light source, wherein the second or more light sources are also positioned to direct the light to the contents of the reactor vessel.

[0267] Various embodiments include methods for destroying PFAS, which involve irradiating an aqueous solution comprising PFAS and sulfites with 222 nm light. The solution may further contain a base sufficient to adjust the pH of the aqueous solution to approximately 10 or higher. The solution may further contain a halide salt, such as a bromide or iodide salt. The solution may further contain a carbonate.

[0268] Various embodiments include photochemical processes and apparatus for reducing photochemical sensitizers used for UV photolysis byproducts back to the original sensitizer. The sensitizer may be a halogen or pseudohalogen, such as a bromide or iodide. The photochemical process and apparatus may also include electrochemical elements. For example, a combination of photochemical and electrochemical apparatus may include a UV light source and an electrochemical device capable of reducing photochemical byproducts of the sensitizer species back to the original sensitizer.

[0269] Various embodiments include a step of destroying PFAS using an advanced reduction process, wherein the oxidized sensitizer, generated by the interaction of the sensitizer with UV light and the emission of solvated electrons, is reduced back to the sensitizer via an electrochemical process. In some such embodiments, the sensitizer is sulfite and iodide. Various embodiments include methods for capturing and / or recovering iodine, comprising adjusting the pH to between about 3 and about 8 or between about 5 and 7, removing any reducing species that could reduce iodine to iodide, and electrochemically oxidizing iodide ions to iodine, for example, in a module that allows for easy recovery and reuse of iodine. Various embodiments include methods and electrodes for carrying out the method, which may include recovering and reusing iodine-containing species by electrochemically oxidizing iodide at an electrode comprising a iodophilic material and a conductive material (e.g., a conductive polymer), wherein the electrode contains oxidized iodide species and optionally a binding material. The iodophilic material can be, for example, starch, chitosan, and / or carboxycellulose, or derived from cellulose, starch, cationic polymers, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, polypyrrole, polyaniline, or poly(3,4-ethylenedioxythiophene), metallocene, metallocene-containing polymers, and / or cationic metal complexes. In some embodiments, the iodophilic material is a cationic polymer. The conductive material can be, for example, graphite, graphene, carbon nanotubes, conductive polymers, and / or doped semiconductors and metals. The binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and / or styrene-butadiene rubber, or polyamide. A voltage of 0.3V (relative to Ag / AgClxx.x volts) or higher can be applied to the electrode, causing the iodide to be oxidized to iodine or polyiodides. The method may optionally further include removing the electrode from the solution and then reducing the iodide / polyiodide-containing electrode to release the iodide into the solution. The electrode can be coupled to a current collector.

[0270] Various embodiments include methods for recovering and / or capturing and recycling iodides from photochemical advanced reduction process (ARP) solutions, comprising: 1) adjusting the pH of the photochemical ARP solution to between 4 and 8; 2) allowing the ARP solution to contact an ion exchange medium; and 3) removing the ion exchange medium from the ARP solution and allowing the iodide-containing ion exchange medium to contact an aqueous salt solution to remove iodides bound to the ion exchange medium. The ion exchange medium may be a strong cation exchange medium. For example, the ion exchange medium may contain quaternary ammonium groups. The aqueous salt solution may be water and a mixture of sodium chloride, sodium bromide, potassium chloride, potassium bromide, sodium hydroxide, potassium hydroxide, sodium sulfate, and potassium sulfate.

[0271] Various embodiments include methods for capturing iodine, comprising adjusting the pH between about 3 and about 8 or between about 5 and about 7, removing reducing species, and electrochemically oxidizing iodide to iodine, for example in a module that allows for the recycling and reuse of iodine. For example, embodiments include methods for capturing iodine comprising adjusting the pH between about 3 and about 8, or between about 5 and about 7, selectively removing (e.g., by adding an oxidant) reducing species, and electrochemically oxidizing iodide ions to iodine. In other examples, various embodiments include methods for capturing iodine comprising adjusting the pH to between 5 and 7, selectively removing reducing species by adding an oxidant, and flowing the solution through an ion exchange medium to selectively remove iodide, or adding a tetraalkylammonium salt to precipitate tetraalkylammonium iodide, or both.

[0272] Various embodiments include combinations of photochemical and electrochemical devices and processes, comprising a light source, a boron-doped diamond-coated substrate capable of generating solvated electrons under UV irradiation, and electrodes located near the diamond-coated substrate such that solvates are generated in a high pH region, allowing the solvated electrons sufficient lifetime to react with PFAS and / or other halogenated contaminants. For example, a device for destroying PFAS may include a UV lamp, an electrochemical cell, wherein a first reduction electrode is boron-doped diamond, which serves as the reduction electrode in a compartment, and a second oxidation electrode is located in a separate compartment, the two compartments being separated by an ion-exchange membrane. Various embodiments also include processes for destroying PFAS using an advanced reduction process, wherein the source of the solvated electrons is boron-doped diamond, which serves as the reduction electrode in an electrochemical system, wherein hydrogen gas and a high pH are generated during photolysis.

[0273] Other embodiments include photochemical and electrochemical devices comprising a UV light source and an electrochemical device capable of reducing photochemical byproducts of sensitizer species back to the original sensitizer, and / or capable of reducing aromatic species to their corresponding radical anions, which are capable of absorbing UV radiation to generate highly reactive excited states that can react directly with PFAS or other halogenated contaminants, and / or capable of reacting with another molecule to generate species that can react with PFAS, for example, those that can react with carbon dioxide to generate carbon dioxide radical anions.

[0274] Various embodiments include a process for the efficient destruction of PFAS molecules, comprising one or more of the following steps: 1) identifying the main chemical composition of a waste stream, 2) treating the waste stream to remove chemicals that may interfere with the efficiency of the photochemical process, and 3) adding a reagent to the treated waste stream to enable a UV photolysis process, the reagent comprising: i) at least one reagent capable of absorbing UV photons and generating chemically active species capable of reacting with one or more PFASs under UV excitation, ii) one or more bases to raise the solution pH to above 10, and iii) optionally, one or more chemicals capable of reacting with UV-generated... 4) Optionally, a voltage is applied to the cathode so that the UV-generated products of the sensitizer are reduced back to the original sensitizer. 5) Optionally, an added base or alkaline solution is added to compensate for pH changes caused by the electrochemical or photolysis process. 6) Optionally, the mixture is purged with an inert gas. 7) Optionally, a device is provided with sufficient flow rate. 8) Optionally, the sensitizer or sensitizer byproducts to be removed from the reaction mixture are separated. 9) Optionally, an acid is added to the UV photolysis mixture to lower the pH to between 4 and 8. 10) Optionally, a module is provided for capturing the sensitizer or the reduction products of the sensitizer.

[0275] Various embodiments include a UV photochemical reactor comprising 1) one or more UV sources, 2) one or more electrochemical systems, 3) optionally, one or more systems for dispensing bases or acids to change the pH of the reaction mixture, 4) optionally, a system for dispensing inert gases, 5) a flow-providing device, and 6) optionally, a module for collecting and / or recycling sensitizers or reduced forms of sensitizers.

[0276] Other embodiments include processes and apparatus for destroying PFAS, wherein an aqueous solution containing PFAS is irradiated with 185 nm UV light while a voltage is applied to an electrode near the irradiated volume to generate hydrogen gas in that volume. For example, in some embodiments, the apparatus for destroying PFAS comprises a 185 nm lamp and an electrochemical device capable of generating hydrogen at the electrode. In some embodiments, hydrogen reacts with oxygen after photolysis. The apparatus may optionally also include a system for removing free fluoride ions after photolysis.

[0277] Various embodiments include a photoreactor for destroying PFAS, the photoreactor comprising an ultraviolet (UV) light source configured to deliver 222 nm light, and a reactor vessel configured to contain an aqueous solution, wherein the light source is positioned to direct the light onto the contents of the reactor vessel. For example, the light source may be a krypton / chlorine excimer. The photoreactor of claim 5 further comprises a second or more light sources, the same as or different from the first light source, wherein these second or more light sources are also positioned to direct the light onto the contents of the reactor vessel. Various embodiments include a method for destroying PFAS, the method comprising irradiating an aqueous solution comprising PFAS and sulfites with 222 nm light, for example, using the photoreactor described above. The method may comprise adding an alkali sufficient to bring the aqueous solution to be treated to a pH of about 10 or higher. It may further comprise adding a halide salt (e.g., bromide or iodine) to the aqueous solution to be treated. In some embodiments containing bromide, the bromide is present in the aqueous solution at a concentration capable of destroying PFAS at a faster rate than iodine salt under the same conditions (where the bromide salt is present at the same or lower concentration). The aqueous solution may further comprise carbonates. These devices and methods may be able to destroy more than 90%, or more than 95%, or more than 99% of PFAS in solution.

[0278] Various embodiments include processes for destroying PFAS using advanced reduction processes, wherein the oxidized sensitizer (e.g., sulfite or iodide) generated by the interaction of the sensitizer and UV light and the emission of solvated electrons is reduced back to the sensitizer via an electrochemical process.

[0279] Various embodiments include a device for destroying PFAS, the device comprising: a UV lamp and an electrochemical cell that can regenerate the sensitizer after photolysis.

[0280] Various embodiments include processes for destroying PFAS using an advanced reduction process, wherein the source of solvation electrons is boron-doped diamond, which serves as the reduction electrode in an electrochemical system, where hydrogen gas and a high pH are generated during photolysis. The source of solvation electrons can be boron-doped diamond, which serves as the reduction electrode in an electrochemical system, where hydrogen gas and a high pH are generated during photolysis. Apparatus that can be used for this process of destroying PFAS may include a UV lamp and an electrochemical cell, wherein the first reduction electrode is boron-doped diamond in a compartment, and a second oxidation electrode is in a separate compartment, the two compartments being separated by an ion-exchange membrane.

[0281] Various embodiments include methods for treating wastewater containing reduced PFAS, comprising the steps of: a. mixing the wastewater with persulfate and an acid or base to raise or lower the pH; b. subjecting the wastewater containing persulfate and an acid or base to elevated temperature and pressure for a sufficient duration for thermal oxidation; and c. subjecting the thermally oxidized wastewater to photoreduction. Photoreduction may be performed using UV radiation of 222 nm and / or 254 nm. The elevated temperature may be, for example, from about 100 to about 140 degrees Celsius, and the elevated pressure may include from about 1 bar to about 5 bar. Step b may be performed, for example, for about 15 to about 120 minutes. Some embodiments may further include diluting the wastewater by about 1 to about 10 times, or from about 2 to about 5 times, after thermal oxidation and before photoreduction. Some embodiments may further include, after step b and before step c, a secondary mixing of the wastewater from step b with persulfate and with an acid or base to raise or lower the pH, and then subjecting the wastewater containing the second addition of persulfate and an acid or base to elevated temperature and pressure for a sufficient duration for thermal oxidation.

[0282] Various embodiments include methods for treating wastewater containing reduced PFAS, comprising mixing the wastewater with persulfate and alkali to lower the pH, subjecting the alkali-containing wastewater to ozone treatment at a sufficient rate and for a sufficient duration for ozone oxidation, and photoreducing the ozone-oxidized wastewater. Photoreduction may be performed, for example, using UV radiation of 222 nm and / or 254 nm.

[0283] Various embodiments include methods for treating wastewater containing reduced PFAS, comprising pretreatment of the wastewater including thermal oxidation or ozone oxidation, mixing the oxidized wastewater with a photosensitizer comprising sulfites, halide salts, and bases, and photoreduction of the ozone-oxidized wastewater at 222 nm and / or 254 nm. These methods may further include diluting the wastewater by 1 to 10 times, or about 1 to 5 times, after oxidation and before photoreduction.

[0284] Example

[0285] Example 1

[0286] Electrochemical reduction of nitrate. A 500 ppm nitrate solution (8.06 mM NaNO3), 0.5 M Na2SO4, 20 mM NaOH, and 10 μM PFHxS were prepared in DI water. 100 mL of each solution was added to the working electrode chamber and the counter electrode chamber of a separated electrochemical cell. The cell was separated using a Nafion 212 cation exchange membrane. A porous iron was used as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. The working electrode chamber was purged with an argon flow. A voltage of -1.3 V (relative to Ag / AgCl) was applied to the working electrode for 15 hours to reduce the nitrate. The solution collected from the working electrode chamber and the same nitrate-containing solution were subjected to a photoreduction process to defluorinate the PFHxS. The percentage of defluorination was measured throughout the photodegradation process, and the results are shown in the figure. Figure 29 As shown.

[0287] Figure 29 The graph shows the total percentage of PFAS defluorination via UV254 photoreduction with and without electrochemical nitrate reduction pretreatment. The photoreduction reaction conditions were 10 mM Na2SO3 and 2 mM KI. These results indicate that photoreduction in the presence of 500 ppm nitrate failed to defluorinate PFHxS, achieving 0% defluorination after 24 hours. However, electrochemical reduction of nitrate in conjunction with photoreduction showed effectiveness for defluorinating PFHxS, achieving >80% defluorination after 24 hours.

[0288] Example 2

[0289] Nitrate nanofiltration. In the presence of nitrate (NO3) - In the case of nanofiltration (NF), the degradation kinetics of PFOA in the membrane rejection solution generated by nanofiltration (NF) were compared with those in reverse osmosis (RO).

[0290] During membrane filtration, 10 L of a solution containing 100 ppm NO3 is filtered. -A synthetic aqueous solution of ~5 µM PFOA was transferred to the feed tank of a benchtop cross-flow filtration system (Benchtop Cross Flow Filtration System, Sterlitech, Auburn, ., USA). The benchtop system was equipped with an 1812 element housing and a spiral-wound membrane element (RO, TriSep, Vacaville, .C., SKU: 1180001) or NFX (Synder, Vacaville, .C., SKU: 1180057). The neutral synthetic solution was filtered through the RO or NFX system at a flow rate of ~2 gal / min and an operating pressure of ~250 psi. Membrane permeates were collected separately. 100 mL samples of membrane rejects were collected in both systems at specific concentration factors. NO3 in the membrane rejects was analyzed using UV-Vis absorption spectroscopy (Shimadzu, Kyoto, Kyoto, Japan, UV-2600i) with its characteristic peak at 301 nm and photoreduction at UV 254 nm. - The concentration was quantified.

[0291] For the photoreduction of membrane rejectants, 100 mL samples from the RO and NFX membrane rejectant solutions were transferred to separate 100 mL quartz vials (Aireka Scientific Ltd., Hong Kong, QP062). 0.12604 g (10 mM) of Na₂SO₃ and 0.332 g (2 mM) of KI were mixed into each 100 mL solution. Then, 0.2 mL (20 mM) of 10 M NaOH was added to each solution to raise the alkalinity to pH 12. Finally, the solutions were photolyzed in a UV 254 nm photolysis photoreactor (Lugchem Research Ltd., Canada, LZC-ORG type). This photoreactor was equipped with eight 10-watt UV 254 nm lamps. During photoreduction, 3 mL samples were removed from the quartz vials at designated time points for quantification of defluorination.

[0292] The percentage of defluorinated fluoride (DeF%) was used to assess and compare the destructive performance of the treatment process. During the treatment, free fluoride (F) was measured using an ion-selective electrode (ISE, Fisher brand accumet solid-state) connected to a Thermo Scientific Orion Versa Star Pro meter. - The concentration of F was then determined based on the following equation. - Calculate the percentage of defluorinated fluoride (DeF%):

[0293] Where F t - and F0- F at time t - Concentration and initial F - Concentration. TOF is the total organic fluorine present. Initial F - The concentration is 0, and the TOF is calculated based on the initial PFOA concentration and the number of CF bonds per molecule. A higher DeF% value indicates that the treatment process converts organic fluorine into free fluorine F. - It has better performance and better conversion efficiency.

[0294] The results are as follows Figure 30 and 31 As shown in the diagram. Figure 30 NO3 was shown - Dependence of concentration (ppm) on the concentration factor of membrane rejectants using RO and NFX. Operating conditions: 100 ppm NO3. - And a ~5 μM aqueous solution of PFOA.

[0295] from Figure 30 It can be seen that NFX allows NO3 - It is more efficient than RO in terms of membrane technology, leaving less NO3 in the membrane rejection process. - NO3 present in RO rejectants - The concentration of NO3 was approximately twice that of the NFX rejectant. At a concentration factor of 3x, NO3... - The concentration in the RO rejectant solution was 290 ppm, which is higher than that concentration in the NFX rejectant solution (e.g., 123 ppm).

[0296] Figure 31 The comparison shows the percentage of defluorination (DeF%) resulting from the photoreduction of membrane rejectants from RO and NFX membranes. The membrane rejectants consist of NO3 containing 100 ppm. - The initial aqueous solution contained 10 mM Na2SO3, ~5 μM PFOA, 2 mM KI, and was generated at pH 12.

[0297] from Figure 31 It can be seen that the membrane repellent from NFX exhibits higher degradation kinetics than that from RO. After 4 hours of photolysis, the NFX-derived sample showed 40.2% defluorination, while the RO-derived sample showed only 23.9%. This difference is believed to be due to the presence of NO3 in the RO sample. - The relatively high concentration of these substances removes hydrated electrons generated by UV radiation, reducing their availability and inhibiting degradation kinetics.

[0298] Both RO and NF exhibited excellent rejection of long-chain PFAS, but NF rejected NO3. -Less. This is believed to be due to the larger pore size and lower electrostatic repulsion of NF compared to RO. Therefore, less NO3 remains in the membrane repellent. - To remove hydrated electrons, water and electrons are essential for promoting the defluorination reaction. While both methods are effective, nanofiltration pretreatment improves PFOA degradation kinetics compared to reverse osmosis in the presence of nitrates.

[0299] Example 3

[0300] Thermal oxidation pretreatment. In this example, and in Examples 4-8 below, the wastewater used in the experiments was foam fraction (FF) from landfill leachate obtained from ALTRA SANEXEN. PFAS concentrations were measured using the EPA 1633 method on a triple quadrupole mass spectrometer (Shimadzu Corporation, USA, LCMS-8060). Concentrations of all PFAS compounds listed in the EPA (Environmental Protection Agency) 1633 method, comprising 40 PFAS analytes, were measured.

[0301] Approximately 10 mL of wastewater was placed in a glass pressure vessel, and 0.4 g of potassium persulfate and 75 mL of 10 M sodium hydroxide were added. Therefore, the thermal oxidation reaction conditions were 150 mM potassium persulfate and 750 mM sodium hydroxide.

[0302] The addition of these reagents caused the solution to become turbid. The tube was loosely sealed to relieve the significant pressure buildup during treatment and placed in a pressure vessel. The pressure vessel containing the tube was then heated to and maintained at 120°C for 120 minutes. After thermal oxidation, the solution became clear and nearly colorless.

[0303] Figure 32 The images show the original sample, the sample after sedimentation, the sample after decantation following mixing with potassium persulfate and sodium hydroxide, and the sample after thermal oxidation. These photographs demonstrate that the originally very turbid sample became clear after thermal oxidation.

[0304] The thermally oxidized samples were further diluted with deionized water (DI water) at factors of 10, 5, or 2. The UV transmission spectra of the original sample, undiluted sample, and diluted sample after thermal oxidation are shown below. Figure 33 Table 1 below shows the UV transmittance (%) of the original wastewater and samples diluted with DI water by 0, 2, 5 and 10 times after thermal oxidation at 222 nm and 254 nm.

[0305] Table 1

[0306] Next, the samples were processed in photoreactors. Then, 100 mL of both diluted and undiluted samples were transferred to 100 mL quartz vials (Aireka Scientific Ltd., Hong Kong, QP062). The 100 mL solution was then mixed with 126 mg sodium sulfite (10 mM), 33 mg potassium iodide (2 mM), and 40–80 mg NaOH (10–20 mM) to bring the pH to approximately 12 as needed. The samples were photolyzed separately in 254 nm and 222 nm photoreactors. The 254 nm photoreactor (Lugchem Research Ltd., Canada, LZC-ORG type) was equipped with eight 10-watt UV254 lamps. The 222 nm photoreactor was equipped with two 100-watt UV222 lamps. A detailed description of the 222 nm photoreactor is provided in another application by the applicant, U.S. Patent Application No. 63 / 591040, entitled “Systems and Methods of PFAS Destruction”, filed on October 17, 2023.

[0307] During the photoreaction, 3 mL samples were taken from the quartz vials at appropriate time intervals for PFAS quantification. PFAS concentrations were measured using the EPA 1633 method on a triple quadrupole mass spectrometer (Shimadzu LCMS-8060, USA). The total PFAS destruction percentage (destruction %) was calculated based on the sum of PFAS detected using the EPA 1633 method, and the results are shown in Figure 34. Figure 34 shows a graph of the total PFAS destruction percentage by photoreduction processes via UV222 and UV254 at various dilution factors for thermally oxidized samples.

[0308] As shown in Figure 34, UV222 generally exhibits better destructive performance than UV254 for thermally oxidized samples. For example, for a 2-fold diluted sample, the total PFAS destruction percentage reached 53.9% after 2 hours of UV222 photoreduction, while <5% destruction was observed after 2 hours of UV254 photoreduction. After 8 hours of reaction, the total PFAS destruction percentage increased to 87.5% during UV222 photoreduction, compared to 48.2% in UV254 photoreduction. The lower dilution required for UV222 photoreduction is highly beneficial for wastewater treatment applications, as it requires less solvent and minimizes waste generation, making it more suitable for large-scale applications.

[0309] Tables 2a and b, and 3a and b below, show the concentrations of selected representative PFAS, respectively, during photoreduction at UV222 and UV254 after thermal oxidation treatment and 2-fold dilution of wastewater samples. As described above, the thermal oxidation reaction conditions were 150 mM potassium persulfate and 750 mM NaOH, maintained at 120°C for 2 hours. The photoreduction reaction conditions were 10 mM Na2SO3, 2 mM KI, and pH 12, as described above. The results indicate that UV222 and UV254 photoreduction are generally effective for a variety of PFAS compounds, such as perfluoroalkyl carboxylates and perfluoroalkyl sulfonates. Notably, UV222 is more effective in destroying perfluoroalkyl sulfonates (e.g., PFBS). For example, for PFBS with an initial concentration of 168–172 µg / L, no residual PFBS concentration was detected after 8 h of UV222 photoreduction, while 152 µg / L of residual PFBS was observed after UV254 photoreduction.

[0310] Table 2a

[0311] Table 2b

[0312] Table 3a

[0313] Table 3b

[0314] Example 4

[0315] Ozone oxidation pretreatment. In this example, wastewater was pretreated with ozone oxidation. The same wastewater as in Example 3 was used. The wastewater was allowed to settle for 12 hours. The nearly clear liquid was then decanted. Next, 1.2 g NaOH was added to 300 mL of the decanted liquid. The addition of NaOH caused turbidity in the solution, and the sample was allowed to settle for 12 hours. Then, 200 mL of the solution was treated with 1000 mg / h O3 for 6 hours using a portable ozone generator (a 1000 mg / h multi-functional ozone generator from VANSU Technology Co., Ltd., Shenzhen, China). The resulting solution was clear and nearly colorless. The oxidized liquid sample was further diluted with deionized water by multiples of 10, 5, or 2. UV transmittance was analyzed for both undiluted and diluted samples. Figure 35 The images show wastewater before treatment, after sedimentation, after mixing with NaOH, after further settling, and after ozone treatment.

[0316] Figure 33The UV transmittance spectra of the raw wastewater and the diluted sample after ozone oxidation are shown, and Table 4 below shows the data from these spectra. Table 4 lists the UV transmittance (%) of the raw wastewater and the diluted sample after ozone oxidation at 254 nm.

[0317] Table 4

[0318] These results indicate that ozone oxidation improves the UV transmittance of wastewater. However, the transmittance results from ozone oxidation are lower than those from thermal oxidation.

[0319] Next, the sample was processed in a photoreactor, and PFAS levels were measured using the same procedure described in Example 3 above. Briefly, 100 mL of ozone-oxidized diluted sample was mixed with 126 mg sodium sulfite (10 mM sodium sulfite), 33 mg potassium iodide (2 mM potassium iodide), and 40–80 mg NaOH (10–20 mM NaOH) to bring the pH to approximately 12 as needed, and photolysis was performed in a 254 nm or 222 nm photoreactor. PFAS levels were measured, and the results for the total PFAS destruction percentage (destruction %) are as follows: Figure 36 As shown. Figure 36 The graphs show the percentage of total PFAS destruction relative to time for ozone-oxidized samples at 10x and 5x dilutions via UV222 and UV254 photoreduction processes. Graphs for 2x dilutions are not shown because PFAS destruction was 0% for both UV222 and UV254 treatments.

[0320] from Figure 36 As can be seen, the UV222 photoreduction system exhibits better destructive performance than the UV254 photoreduction system for ozone oxidation of diluted samples. This is consistent with the results for the thermally oxidized samples in Example 3. In the UV222 photoreduction system, after 8 hours of reaction, the percentage of total PFAS destruction increased to 61% and 22% for samples diluted 10-fold and 5-fold, respectively. Conversely, very little destructive performance was observed in the UV254 photoreduction system.

[0321] Figure 37 The bar charts show the broken PFAS results for Examples 1 and 2. Figure 37The percentage of total PFAS destroyed after 4 hours of treatment in UV254 and UV222 photoreduction systems is shown, following either thermal oxidation or ozone oxidation as a pretreatment step. Thermal oxidation was more effective than ozone oxidation in improving subsequent photoreduction treatment. For samples diluted 5-fold, thermal oxidation pretreatment improved the percentage of destruction in UV254 and UV222 by 85.5% and 91.9% after 4 hours, respectively, which is higher than the 4.7% and 9.6% achieved by the method following ozone pretreatment in UV254 and UV222, respectively.

[0322] Example 5

[0323] Thermal oxidation pretreatment. In this example, wastewater was thermally oxidized using various dosages of oxidant (e.g., potassium persulfate). First, 300 mL of wastewater was mixed with 1.2 g NaOH (3 mL of 10M NaOH solution). The addition of NaOH caused turbidity in the solution, and the sample was allowed to settle for 12 hours. Then, 30 mL of the decanted solution was placed in a separate glass pressure vessel. Subsequently, 30 mL of the solution was mixed with various dosages of potassium persulfate (0.04 g, 0.08 g, 0.2 g, 0.4 g, 0.6 g, 1.2 g) and 10 M sodium hydroxide (0.075 mL, 0.15 mL, 0.375 mL, 0.75 mL, 1.125 mL, 2.25 mL). The pressure vessel was loosely sealed and heated to 120°C for 120 minutes.

[0324] Figure 38 Photographs of solutions after thermal oxidation with various doses of potassium persulfate and sodium hydroxide are shown. Containers af are shown in order of dose from lowest dose (a) to highest dose (f). The reaction conditions are: a) 5 mM K2S2O8 and 25 mM NaOH; b) 10 mM K2S2O8 and 50 mM NaOH; c) 25 mM K2S2O8 and 125 mM NaOH; d) 50 mM K2S2O8 and 250 mM NaOH; e) 75 mM K2S2O8 and 375 mM NaOH; and f) 150 mM K2S2O8 and 750 mM NaOH, each maintained at 120°C for 2 hours.

[0325] like Figure 38 As shown, for solutions with lower chemical concentrations, the solution remains yellow after thermal oxidation. Figure 38 The container in the middle (ae). However, under the conditions of the highest dosage, 150 mM K2S2O8 and 750 mM NaOH, the solution after thermal oxidation became colorless ( Figure 38 The container f in the middle.

[0326] Example 6

[0327] Thermal oxidation pretreatment. In this example, the wastewater was thermally oxidized under various pH conditions. Approximately 10 mL of wastewater and 0.4 g of potassium persulfate were added to each of three glass pressure vessels. For acidic reaction conditions, 0.2 mL of 1 M sulfuric acid was added to the sample in the first vessel. For alkaline reaction conditions, 0.75 mL of 10 M sodium hydroxide solution was added to the sample in the second vessel. For neutral reaction conditions, no additional chemicals were added to the sample in the third vessel. The pressure vessels were loosely sealed and heated at 120°C for 120 minutes. The resulting solutions were clear and nearly colorless, with some sediment at the bottom of the vessels. The clear top layers of each oxidized sample were diluted with deionized water at multiples of 10, 5, and 2, and the UV transmittance was measured. Table 5 lists the UV transmittance at 254 nm for the original sample and the thermally oxidized samples diluted 0, 2, 5, and 10 times with DI water for each condition.

[0328] Table 5

[0329] Example 7

[0330] Two-stage thermal oxidation pretreatment. In this example, a two-stage thermal oxidation of wastewater was performed, and the results of different combinations of reaction times were compared. First, 300 mL of wastewater was mixed with 1.2 g of NaOH (3 mL of 10 M NaOH solution). The addition of NaOH caused the solution to become turbid, and the sample was allowed to settle for 12 hours. Then, 30 mL of the decanted solution was placed in each glass pressure vessel, and 1.2 g of potassium persulfate and 2.25 mL of 10 M sodium persulfate were added. The pressure vessels were loosely sealed and maintained at 120°C. In the first stage of thermal oxidation, the reaction time was controlled between 15 and 120 minutes. After the first stage of thermal oxidation, the resulting solution was clear and nearly colorless. As the second stage of thermal oxidation, an additional 1.2 g of potassium persulfate was added to the 30 mL solution in the glass pressure vessel, and the solution was maintained at 120°C for 30 to 60 minutes. After the second stage of thermal oxidation, the oxidized sample was further diluted with deionized water by factors of 10, 5, and 2, and the UV transmittance was measured. Table 6 lists the UV transmittance at 254 nm of untreated raw wastewater and wastewater diluted with DI water by 0, 2, 5, and 10 times after two-stage thermal oxidation treatment.

[0331] Table 6

[0332] Table 6 shows that, compared to the original wastewater, the two-stage thermal oxidation significantly improved the UV transmittance at 254 nm. For the undiluted sample, thermal oxidation for 120 minutes followed by 60 minutes increased the UV transmittance at 254 nm from 0.0% to 11.1%. When the reaction time was shortened to 30 minutes followed by another 30 minutes, the UV transmittance at 254 nm further increased to 42.2%. Compared to the combination of 120 minutes and 60 minutes of reaction time, the combination of 30 minutes and 30 minutes of reaction time is more advantageous for practical applications due to its higher processing capacity and better improvement in UV transmittance.

[0333] Example 8

[0334] Comparison of photosensitizers. In this example, a water sample containing PFAS was treated with photoreduction without pretreatment and two different photosensitizer concentration levels were used. The water sample contained ~0.9 ppm TFA (CF3-COO-), ~0.6 ppm PFBA (C3F7-COO-), and ~31.8 ppm 7H-PFHpA (H-C6F-). 12 -COO-).

[0335] The first sample of wastewater was mixed with photosensitizer A, which contained 10 mM Na2SO3 and 2 mM KI at pH 12. The second sample of the same wastewater was mixed with photosensitizer B, which contained 50 mM Na2SO3 and 10 mM KI at pH 14.

[0336] Next, the two samples were treated at 254 nm for 24 hours in a 750 mL tubular reactor, and samples were taken at appropriate time points for analytical purposes, such as kinetic fitting of PFAS degradation during the process and calculation of defluorination performance.

[0337] PFAS levels were measured before and after photoreduction. Degradation kinetics were based on a pseudo-first-order kinetic model (ln(C)). T / C0)= k t) is calculated by fitting, where C t C0 refers to the PFAS concentrations at time T and time 0 during photoreduction, respectively.

[0338] A comparison of degradation kinetics achieved using photosensitizer A versus photosensitizer B is as follows: Figure 39 The bar chart is shown in the figure. Figure 39 The degradation kinetics results for TFA, PFBA, and 7H-PFHpA are shown. In each case, photosensitizer B yielded surprisingly better results, with reaction kinetics 4 to 6 times higher than those in this example.

[0339] Example 9

[0340] 222 and 254 nm UV light reduction. The photoreactor used in this example is referred to herein as 222reactor 1 (222REACTOR1). 222reactor 1 comprises two cylindrical lamps, machined metal supports for horizontally supporting the lamps at a distance above a horizontal plane, a photoreactor container, and a metal housing. The cylindrical lamps are krypton / chlorine excimer lamps emitting approximately 222 nm UV radiation. Each lamp is powered by a separate 20 kV power supply located within the housing, and each lamp consumes 100 watts of power. The lamps have a diameter of 54 mm and a length of 460 mm. The lamps are statically held parallel to each other at a distance of 100 mm (center to center) from each other by rigid machined aluminum clamps at a fixed distance of 57.2 mm (surface to center of cylinder) from the horizontal ground of the metal container. In other possible embodiments of this photoreactor, lamps of different diameters and lengths may be used. In other possible embodiments, the machined supports for the lamps may be of different sizes to result in shorter or longer distances between the lamps and between the lamps and the horizontal ground.

[0341] The reactor vessel is a cylindrical quartz vial with a measured diameter of 40.1 mm. The total height of the reactor vessel is 114.6 mm, with the first 100 mm of the total height having a uniform diameter, and the remaining 14 mm gradually tapering to form a threaded top cylinder with a diameter of 12 mm. In other embodiments, the reactor vessel may have other diameters and / or heights.

[0342] The photoreactor is housed within a metal enclosure. A metal filing drawer is used as the metal enclosure. Alternatively, other structured enclosures, such as structured metal enclosures, may also be used.

[0343] Seven different PFAS substances were treated in the photoreactor, as described below. The tested PFAS included perfluorobutyric acid (PFBA), perfluorovalerate (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS).

[0344] Seven different PFAS substances were prepared at concentrations between 2.5 and 10 ppm and used in this example. The PFAS stock solutions were mixed with 25 mM NaHCO3 and one of various reducing solutions. A control solution containing no PFAS was also tested.

[0345] The following five solutions were used as reducing solutions: 1 mM KI and 5 mM Na2SO3; 1 mM KI and 50 mM Na2SO3; 10 mM KBr and 50 mM Na2SO3; 10 mM KI and 50 mM Na2SO3; and 50 mM Na2SO3. A sixth solution containing only reagent water was also used (for direct irradiation).

[0346] The solution was added separately to the reactor vessel, and threaded plastic caps with silicone diaphragms were screwed onto the top of the vials to create a leak-proof seal. In reactor 1 (222), the reactor vessel was placed between parallel krypton / chlorine lamps, allowing radiation to enter the vessel from both sides. The solution was irradiated at 222 nm in the photoreactor for three hours. The reactor temperature was maintained between 55 and 60 degrees Celsius during the reaction.

[0347] During photoreactor processing, the amount of PFAS present in the solution was periodically measured by extracting samples from the reactor solution and transferring them into vials to preserve them for LCMS analysis after stopping the reactor.

[0348] The results of photoreaction treatment of each PFAS in each solution are as follows: Figure 40 and 41 As shown in the chart.

[0349] Figure 40 The PFAS concentration as a function of time is shown for photoreduced PFAS in each reduction solution at 222 nm. Figure 1 Qualitative analysis showed that the PFAS degradation rate was faster in solutions containing iodide / sulfite compared to the degradation rate observed under direct irradiation in pure water. Furthermore, it was evident that the PFAS concentration loss rate was faster in the model solutions (1 mM KI and 5 mM KI) than in any other solution.

[0350] Figure 41 The percentage of PFAS destroyed by photoreduction in each reducing solution at 222 nm is shown over time. The reducing solution used is indicated in the title of both sets of figures. Figure 2 The study demonstrated a quantitative increase in PFAS destruction over a 3-hour period when the model solution was compared to all other solutions and reagent water. Furthermore, it was evident that the percentage of destruction of both carboxylated and sulfonated PFAS was significantly higher in the model solution than in other solutions, and considerably higher than in direct irradiation with reagent water.

[0351] Figure 41Data also includes PFAS materials prepared as treatment solutions and treated with 10 mM KI and 50 mM Na2SO3 reduction solutions as described in Example 1 above. However, these solutions were irradiated in a separate photoreactor referred to herein as the 254 reactor (254REACTOR) at 254 nm. The 254 reactor is a LUZCHEM LZC-ORG box reactor equipped with ten 8-watt low-pressure mercury lamps. The treatment solutions were irradiated in the 254 reactor for three hours. These results are as follows... Figure 41 As shown in column 5.

[0352] The selected experiment was repeated three times, and the average of the three independent experimental results was taken and plotted using statistical analysis. The results are as follows: Figure 42 As shown. These results were compared with those obtained by direct irradiation of the PFAS solution at 222 nm. Figure 3 The examination showed that, in repeated trials with n=3, the percentage destruction of individual PFAS compounds and the decrease in concentration over time were statistically distinguishable in the model solutions. For example, the percentage destruction over time of carboxylated derivatives (at a 68% confidence level) was greater than that of PFHxS and PFOS, which was greater than that of PFBS. This difference was even more pronounced in solutions without bicarbonate. Within the confidence limits, destruction in 1 mM KI / 5 mM Na2SO3 solution was also significantly greater than destruction caused by direct irradiation in reagent water.

[0353] The data from this example is normalized and fitted to a single exponential function. (1) in C ( t () is the concentration at time t. C 0 This is the initial concentration, and τ is the first-order time constant (the reciprocal of the rate constant). The first-order rate constant is converted to half-life (multiplied by 0.6901). From... Figure 2 The plotted data is fitted into Equation 1. Figure 4 Exemplary fits are shown for the destruction of PFAS over time using solutions of 1 mM KI, 5 mM Na2SO3, and 25 mM NaHCO3. Smaller time constants indicate that less time is required to destroy PFAS.

[0354] Table 7 below shows the fit of Equation 1 to data on the destruction of PFAS using 1 mM KI, 5 mM Na2SO3, and bicarbonate solutions over time. The first-order time constant τ was determined from the data plotted in columns 1, 3, 4, 5, and 6 and converted to half-life in Table 7. Table 7 shows the variation of the time constant relative to time for the destruction of PFAS using a 222 nm light source for various solutions and reagent water. 1 / 2 It is a first-order time constant, σ is at the 68% confidence limit t 1 / 2 The error. The dashes in PFBS, PFHxS, and PFOS in the reagent water column indicate that they correspond to very high t. 1 / 2 value.

[0355] Table 7

[0356] Figure 42 The half-life data plotted are shown in Table 8. Table 8 shows a comparison of the time constant of PFAS destruction using 222 nm as a function of time for experiments with n=1 and n=4 using solutions of 1 mM KI and 5 mM Na2SO3. Half-life t 1 / 2 It is the half-life that destroys PFAS, σ is t 1 / 2 With an error at a 68% confidence limit.

[0357] Table 8

[0358] Figure 43 The results of these exemplary fittings, as well as the results of exemplary fittings for all n=1 solutions, are shown in Table 7. Figure 43 Equation 1 is shown, fitting data on the destruction of PFAS over time using 1 mM KI, 5 mM Na2SO3, and bicarbonate solutions. Within the confidence limits, the rates of the model solutions are distinguishable from those of other solutions and reagent water.

[0359] Example 11

[0360] 222 nm light reduction. This example uses a different design of a 222 nm photoreactor. This photoreactor, referred to in this paper as 222reactor2, includes a photoreactor container, fixtures, lamps, a transparent sleeve, pumps, and various valves and piping.

[0361] The photoreactor container is a non-porous cylinder sealed at one end to contain liquid. The lamp bulb is also cylindrical, with a diameter smaller than that of the photoreactor container. The cylindrical lamp bulb is placed inside the cylinder (within a transparent sleeve) and fixed such that the bulb's long axis is parallel to the long axis of the cylinder and centered within the photoreactor container. The photoreactor container cylinder includes a flow adjustment outlet near the base through which liquid is discharged. The reactor container cylinder also includes an inlet near the top through which liquid is added to the cylinder. Clamps hold the photoreactor container cylinder so that its long axis is perpendicular to the horizontal tabletop.

[0362] The photoreactor container column is approximately 75 mm in diameter and 500 mm in length, and is made of stainless steel with a wall thickness of approximately 3 mm. The inlet and outlet of the photoreactor container column are machined threaded openings that can accept connections to flexible or rigid piping. In this particular arrangement, the machined threaded openings are stainless steel, ½-inch national pipe thread fittings, welded, brazed, or soft-welded to the face of the metal column.

[0363] A cylindrical lamp bulb is inserted into a transparent sleeve centered on the top surface of the photoreactor container cylinder and parallel to its long axis. A stainless steel cap holds and secures the sleeve. The cap includes a central bore through which the sleeve is inserted, and an outer cylindrical ring with an inner diameter (ID) slightly larger than the outer diameter of the stainless steel cylinder. The cap is a welded and machined stainless steel cylinder, approximately 70 mm long and 100 mm in diameter. The transparent sleeve is approximately 500 mm long and 55 mm in diameter (OD), and is sealed at the bottom to prevent liquid contact with the lamp. The transparent sleeve is made of quartz capable of transmitting light at wavelengths of approximately 225 nm and below.

[0364] The lamp is a krypton / chlorine excimer lamp consuming 100 watts of power and powered by an external 20 kV power supply. The bulb of the lamp is measured to be approximately 54.6 mm in diameter and 460 mm in length, and produces radiation of approximately 222 nm with a full width at half maximum (FWHM) of approximately 4 nm.

[0365] Reactor 222 also includes a pump connected in series along a rigid stainless steel conduit between the outlet and inlet of the photoreactor vessel. A series of valves are located in the conduit along the suction side of the pump to block liquid flow from the bottom of the reactor vessel and direct the pump inlet to a container from which liquid can be drawn into the reactor. A series of valves are also located in series along the pressure side of the pump to block liquid flow from the pump and direct the pump flow to an external container from which fluid can be collected from the reactor. The pump is a low-flow circulating pump of the type typically used in passive or active solar heating applications. The conduit comprises ¼-inch OD stainless steel tubing that is bent to form a sealed connection matrix between the valves and pump and the metal column of the photoreactor.

[0366] A comparison was made between using only Na₂SO₃ and using Na₂SO₃ and KBr. Each treatment solution contained 10 ppm PFOA and only 5 mM Na₂SO₃ or 5 mM Na₂SO₃ and 150 mM KBr. NaHCO₃ was not present in either treatment solution, although pH 12 was achieved by adding sodium hydroxide.

[0367] The reactor solutions were placed separately in photoreactor containers and irradiated at 222 nm for 24 hours in reactor 222.

[0368] During photoreactor treatment, the amount of PFOA present in the solution was periodically measured by extracting samples from the outlet of the photoreactor vessel and preserving them for LCMS analysis. Results for the first four hours are as follows: Figure 44 and 6 As shown.

[0369] Figure 44 The data show the time-varying destruction of PFAS by photolysis of PFAO using 5 mM Na2SO3 and 150 mM KBr (blue squares), and the time-varying defluorination of PFOA using only 5 mM Na2SO3 (red triangles). Data are represented by symbols, and the best exponential fit is shown by lines.

[0370] Figure 45 The diagram shows the fluoride (F-) concentration over time obtained from the defluorination of PFOA. Blue squares show the change in fluoride concentration (symbol) over time using 5 mM Na₂SO₃ and 150 mM KBR, with the blue line indicating the best exponential fit. Red triangles show the change in fluoride concentration over time using only 5 mM Na₂SO₃, with the red line indicating the best exponential fit.

[0371] These results indicate that reactor solutions containing bromides achieve faster and more complete defluorination than reactor solutions containing only Na2SO3.

[0372] It is noteworthy that in Example 10, there was essentially no statistically significant difference in the decay rate between the 10 mM KBr / 50 mM Na2SO3 solution and the KBr-free solution compared to the 50 mM Na2SO3 solution. However, in Example 10, which contained higher levels of KBr (and lower levels of sulfite), the presence of KBr had a clearly positive effect on PFOA destruction.

[0373] Given that the molar absorptivity of sulfite at 222 nm is 70 times greater than that of KBr (5400 nm for sulfite), -1 cm -1[Internal experiments], compared to KBr's 77.61 M -1 cm -1 [Birkmann et al., Water Practice and Technology, 2018, 13(4); pp. 879-892], it is believed that sulfites absorbed most of the light in Example 1. In contrast, in Example 2, KBr was effective in improving the destruction of PFOA when sulfites decreased and bromides increased. Although we do not know the relative quantum efficiency of photogenerated electrons at that wavelength, assuming this yield is comparable in KBr and KI, then increasing the concentration of KBr by 147 times relative to the concentration of KI (ε = 11527 M for KI) would require... -1 cm -1 Compared to KBr's ε=176.61 M, - 1 cm -1 [Birkmann et al., Water Practice and Technology, 2018, 13(4); pp. 879-892]) may produce a considerable effect. ε is the molar extinction coefficient.

[0374] Similarly, in Example 10, no significant difference in the PFAS degradation rate was observed when comparing a 10 mM KI / 50 mM Na₂SO₃ solution with a 50 mM Na₂SO₃ solution. In fact, it is debatable whether the rate would be slightly lower with the addition of KI. Therefore, it would be meaningful to study the PFAS degradation rate in more detail with respect to the concentration of the solution containing only Na₂SO₃. A direct comparison between the degradation rates of a 5 mM Na₂SO₃ solution and the model solution should provide a clear indication of whether 1 mM KI is significant at this concentration. Furthermore, calculations showed that the concentrations of KI and Na₂SO₃ need to be up to three orders of magnitude lower than those of the model solution for light to penetrate at least 1 cm into the reactor cell at 222 nm. Recognizing the important inverse relationship between light penetration and the concentration of electrons removed in solution required to degrade PFAS, the concentrations of KI, Br, and Na₂SO₃ in the tens to hundreds of μM range can influence the rate of PFAS degradation.

[0375] Example 12

[0376] 222 nm and 254 nm UV light reduction. Further experiments were conducted using 222 nm and 254 nm UV radiation to evaluate the destruction of PFAS foam fractions.

[0377] Foam-distilled water was obtained from the Minnesota Department of Pollution Control (MPCA). The major compounds in the MPCA sample were identified as PFOA and PFOS. Other compounds (PFHxA, PFHxS, PFHpS) were detected, although at concentrations below the limit of quantitation. Since the sample was diluted 5-fold for LC-MS analysis, the limit of quantitation (LOQ) for each compound in the fractionated sample was back-calculated to ~10 ppb.

[0378] Reactor 222 was used to deliver 222 nm radiation. The reagents used with the 222 nm radiation consisted of 1 mM potassium iodide (KI) and 5 mM sodium sulfite (Na2SO3). A 5x diluted sample was placed in reactor 222 and irradiated with 222 nm UV for 5 hours.

[0379] The 254 reactor was used to deliver 254 nm radiation. The reactor solution used with the 254 nm radiation contained 40 mM potassium iodide (KI) and 200 mM sodium sulfite (Na2SO3). A 5x diluted sample was placed in the 254 reactor and irradiated with 254 nm UV for 6 hours.

[0380] For each reactor, during photoreactor processing, the amount of PFAS present in the solution is periodically measured by stopping the reactor, extracting samples from the reactor vessel, and transferring them into vials to preserve them for LCMS analysis.

[0381] The results are as follows Figure 46 As shown, the percentage of PFAS destroyed over time (top row) and the concentration of PFAS over time (bottom row) are presented for treatments at 222 nm (left) and 254 nm. The 5x diluted sample achieved complete destruction after 5 hours at 222 nm UV and ~99% after 6 hours at 254 nm UV. Other compounds (PFHxA, PFHxS, PFHpS) also showed concentrations below the quantitation limit at this time point.

[0382] The results showed that PFAS destruction was similar between the two experiments. However, the treatment at 222 nm achieved these results using significantly lower iodide and sulfite concentrations (1 / 40) than the treatment at 254 nm. This is particularly important for the iodine aspect due to its much higher cost compared to other reagents. The comparable or better destruction performance in the 222 nm system under significantly reduced iodide concentrations – and therefore correspondingly lower costs – represents a significant advance towards developing an efficient and economical means of PFAS destruction. This cost saving is particularly important in large-scale processes, in terms of both efficiency and operational savings.

[0383] Example 13

[0384] Use the following photoreactor and experimental design in Examples 13, 14, and 15. The photoreactor comprises: a Pyrex cylindrical beaker (84 mm in diameter, 124 mm in height, total volume 600 mL); a rubber stopper with tapered sides, 84 mm in diameter at half height; two quartz sleeves sealed at one end, 23 mm in diameter and 190 mm in length (technical glass, GE 214); and two 15-watt UV lamps. Depending on the following experiments, two different types of UV lamps are used, which are interchangeable in the reactor: 1) a UV 222 nm excimer lamp, 23 mm in diameter and 190 mm in length; and 2) a UV 185 / 254 nm lamp, 19 mm in diameter and 200 mm in length.

[0385] The rubber stopper has two 23 mm diameter holes cut along its diameter, centered 16 mm from the center of the stopper, and four smaller holes (2 x 6.3 mm and 2 x 7.6 mm) arranged in a 60 mm square, the center of which coincides with the center of the stopper. When using a salt bridge, an additional 1 cm hole is present in the stopper to accommodate it. A quartz sleeve fits into the 23 mm holes and protrudes through the stopper, such that the sealing end of the sleeve protrudes 75 mm beyond the lower plane of the conical stopper. The rubber stopper fits tightly into the beaker, causing the quartz sleeve to protrude into the beaker. A UV lamp is placed into these sleeves through the opening (top) of the quartz sleeve protruding into the beaker. The beaker (with a stir bar) is placed on a stirring plate. The smaller diameter holes appearing in the reactor are ports for probes, electrodes, and purge wires used in the experiments described below.

[0386] Photodegradation was performed by decanting 450 ml of the sample PFAS solution into a 600 ml beaker. The solution was purged with argon for 15 minutes, stirred, and then the lamp was turned on (at zero time). Samples were taken at regular time intervals throughout the photodegradation process. These samples were analyzed using a fluoride sensor to detect free fluoride ions released by the degradation of PFOS.

[0387] Electrochemical reduction of iodine. In this example, the recycling of iodide without the use of sulfites is tested by electrochemically reducing iodine free radicals generated by photochemistry.

[0388] A 450 ml solution containing 5 ppm perfluorooctane sulfonic acid (PFOS), 1 mM potassium iodide (KI), 0.1 M sodium sulfate, and 20 mM sodium hydroxide (NaOH) was decanted into the reactor. One end of a salt bridge (1 M KCl) was passed through a stopper and inserted into the reactor solution. The other end of the salt bridge was placed in a stirred 1 M aqueous KCl solution containing a 2 x 2 cm platinum mesh counter electrode, which served as the anode throughout the experiment. The 2 x 2 cm platinum mesh working electrode and the Ag / AgCl reference electrode were suspended in the reactor cell solution. A potential of -0.7 V (relative to Ag / AgCl) was applied to the working electrode using a potentiostat (BioLogic). The platinum working electrode served as the cathode and reduced the oxidized iodine radicals back to iodide. The solution was purged with argon before and during the PFOS destruction experiment. The working electrode was positioned approximately 2 cm from the quartz sleeve housing the lamp. The zero point of the PFOS destruction experiment was when the lamp was turned on. In this experiment, a 222 nm UV lamp was used. The quartz sleeve had a transmittance of 0.8 at 222 nm. Samples were drawn at regular time intervals through the channel port in the rubber stopper, with a sampling error of + / - 30 seconds.

[0389] The results are as follows Figure 47 As shown in the diagram. Figure 47 This is a graph showing the percentage change in free fluoride over time relative to the theoretical maximum for the destruction of 5 ppm PFOS, as described above. The percentage of free fluoride is for a solution in which a potential of -0.7 V (relative to Ag / AgCl) was applied to the electrodes (black squares). For the control group, no potential was applied between the electrodes (grey circles). The error bars are plotted at a 95% confidence level. After 120 minutes, the control experiment without applied potential achieved only 3% defluorination, while the electrochemical experiment achieved 18% defluorination after 120 minutes. This demonstrates that the electrochemical system regenerates iodide during photoreduction experiments, achieving efficient PFAS destruction with little or no sulfite.

[0390] Example 14

[0391] Electrochemically regenerated hydrogen is used to destroy perfluorooctane sulfonic acid (PFOS). In this example, 185 nm light is used to generate hydroxyl radicals. These hydroxyl radicals react with electrochemically generated molecular hydrogen to ultimately form solvated electrons for the reductive destruction of PFAS. As part of this example, three experiments are shown here: 14(a) a destruction control in which reactor solutions of PFOS, sodium sulfate, and sodium hydroxide are run under 185 nm radiation but no voltage is applied to the electrodes; 14(b) a destruction experiment in which reactor solutions of PFOS, sodium sulfate, and sodium hydroxide are run under 185 nm radiation with both the anode and cathode present in the reactor cell; and 14(c) a destruction experiment in which reactor solutions of PFOS, sodium sulfate, and sodium hydroxide are run under 185 nm radiation with the cathode in the reactor cell and the anode isolated in a separate cell. The anode and cathode cells are connected by a salt bridge.

[0392] In Examples 14(a)–14(c), the starting point (time zero) for the PFOS disruption experiments is the time the lamp is turned on. The reactor solution is purged with argon during the experiments. Purging begins 15 minutes before the start of the experiments. The reactor solution is continuously stirred throughout the experiments. A UV 185 / 254 nm lamp was used in this experiment. The quartz sleeve has a transmittance of 0.63 at 185 nm. Samples are drawn at regular time intervals through the channel port in the rubber stopper, with a sampling error of + / - 30 seconds.

[0393] Example 14(a): A 450 ml solution containing 0.1 M sodium sulfate, 20 mM sodium hydroxide, and 5 ppm PFOS was stirred and decanted into a photoreactor. This experiment served as a control. No voltage was applied to the battery. A lamp was turned on in the photoreactor during this experiment.

[0394] Example 14(b): A 450 ml solution containing 5 ppm PFOS, 1 mM sodium hydroxide, and 5 mM sodium sulfate (electrolytes) was decanted into a photoreactor. The working electrode and counter electrode (both 10 x 10 cm platinum-coated titanium mesh square electrodes, bent to fit the reactor beaker diameter) and the reference electrode (Ag / AgCl) were suspended in the reactor cell solution. A potential of -1.1 V (relative to Ag / AgCl) was applied to the working electrode, which served as the cathode. This applied potential was higher than the potential required to electrolyze water into molecular hydrogen at the cathode and into molecular oxygen at the anode. The working electrode was located approximately 2 cm from the quartz sleeve of the reactor housing the lamp.

[0395] Example 14(c): A 450 ml solution containing 5 ppm PFOS, 1 mM sodium hydroxide, and 5 mM sodium sulfate was decanted into a photoreactor. A working electrode (a 10 x 10 cm square electrode made of platinum-coated titanium mesh, bent to fit the diameter of the reactor beaker) was suspended in the photoreactor solution. One end of a salt bridge (1 M sodium sulfate) was passed through a plug and inserted into the reactor solution. The other end of the salt bridge was placed in a beaker containing a 1 M aqueous sodium sulfite solution under stirring, and a counter electrode, also made of platinum-coated titanium mesh, was suspended in this solution. This electrode served as the anode throughout the experiment. The counter electrode oxidized the sulfite to sulfate at the electrode interface. The salt bridge ensured charge neutrality between the anode and cathode cells. The working electrode was positioned approximately 2 cm from the quartz sleeve of the reactor housing the lamp. During the destructive experiment, a voltage of 58.13 volts was applied between the electrodes, resulting in a current between the electrodes of 49 mA at the start of the experiment and 86 mA at the end of the experiment after 2 hours. Five minutes after the initial current was applied, visible hydrogen bubbles could be seen forming on the platinum mesh electrode.

[0396] The result of Example 14 is as follows Figure 48 The plot shown is a graph illustrating the percentage of free fluoride destroyed at 5 ppm PFOS, as described in Examples 14(a)-14(c), versus the theoretical maximum over time. Error bars are drawn at a 95% confidence level. The results of Example 14(a) (control experiment) are plotted with gray circles. After 120 minutes, this control experiment achieved only about 10% defluorination. The results of Example 14(b) are plotted with gray squares; here, both the anode and cathode are present in the photoreactor. In this experiment, essentially zero defluorination was achieved after 2 hours. This is likely due to oxygen present in the reactor pool due to water photolysis. Oxygen is a strong quencher of solvated electrons. The results of Example 14(c) are plotted with black squares. In this experiment, the anode and cathode are present in separate pools connected by a salt bridge. In this experiment, 35% defluorination was achieved after 120 minutes. This experiment demonstrates that PFOS can be effectively destroyed without the addition of chemical photosensitizers by utilizing in-situ electrochemical hydrogen generation.

[0397] Example 15

[0398] Synthesis of Iodide Recycling Electrode. The iodide recycling electrode was synthesized by mixing 2 g of starch and 2 g of graphite using a mortar and pestle. The mixed powder was then placed in a ball mill running at 1200 rpm for 60 minutes. The resulting powder was then mixed with 5 mL of 60% PTFE solution using a mortar and pestle. The result was a flexible putty-like material, which was repeatedly folded to create homogeneity and structural integrity. The material was then dried in an oven at 80°C for 6 hours to remove water from the structure. The result was a strong but flexible sheet. 2x2 cm squares were cut from this sheet, and the sheet was attached to a conductive carbon paper current collector using a conductive carbon coating. The carbon paper was then covered with Teflon tape and varnish, so that only the iodide recycling material was exposed to the solution during operation.

[0399] Example 16

[0400] Electrodes were used to recover and reuse iodides. A 0.1 M Na3PO4 pH 7 solution was prepared for use in a 3-electrode cell, wherein the working electrode was the iodide recovery and reuse electrode described in Example 14, the counter electrode was a Pt mesh, and the reference electrode was Ag / AgCl. Oxidative linear sweep voltammetry (LSV) was performed, as seen in Figure 49a, and reductive LSV was performed, as seen in Figure 49b.

[0401] Potassium iodide was then added to the solution to reach 50 mM KI. The same oxidation LSV was performed, as shown in Figure a. The significantly higher current generated in the 50 mM KI solution indicates that iodide oxidation is occurring. Then, at 0.25 mA / cm²... 2 Constant current electrolysis was performed. After 40 minutes, a yellow color was observed in the solution near the working electrode, indicating that the electrode was affected by I3. - Completely saturated. Then a fresh 0.1 M Na3PO4 pH 7 solution was prepared and the same reduction LSV was performed, as seen in Figure b.

[0402] Figure a shows the oxidized LSV in 0.1 M Na3PO4 at pH 7 with and without iodide (solid line) and with 50 mM KI (dashed line). Figure b shows the reduced LSV in 0.1 M Na3PO4 at pH 7 with and without iodide (solid line) and with I3- loading (dashed line). The much higher current at -1.1 V (relative to Ag / AgCl) can be attributed to the I3- already immobilized in the electrode. - The reduction was then performed at -0.25 mA / cm². 2 Constant current electrolysis was performed for 40 minutes to remove I3 - Convert to I -It was then released into the solution. The resulting solution contained 0.44 mM iodide.

[0403] Example 17

[0404] Iodides were recovered and reused using an electrode. Four cycles of iodide capture and evacuation were performed using the iodide recovery and reuse electrode described in Example 14. The iodide capture medium was 100 mL of a 0.1 M Na₃PO₄ + 2 mM KI pH 7 solution. For iodide capture, a three-electrode unsplit cell was used, with the working electrode being the iodide recovery and reuse electrode described in Example 13, the counter electrode being a Pt mesh, and the reference electrode being Ag / AgCl. A current of 0.25 mA / cm² was used. 2 The iodide capture step was performed using constant current electrolysis for 30 minutes. After each iodide capture step, the electrode was thoroughly cleaned and dried with DI water and set up for the iodide recovery and reuse step. The iodide recovery and reuse medium was 100 mL of 0.1 M Na3PO4 pH 7 solution. A three-electrode cell separated by a Nafion 212 cation exchange membrane was used to recover and reuse iodide, wherein the working electrode was the iodide recovery and reuse electrode described in Example 13, the counter electrode was a Pt mesh, and the reference electrode was Ag / AgCl. The current was -0.25 mA / cm². 2 The iodide recovery and reuse step is performed by constant current electrolysis for 30 minutes. After each iodide recovery and reuse step, the electrode is thoroughly cleaned and dried with DI water and set up for the iodide capture step.

[0405] The removal and recycling of iodide after the second and fourth cycles, such as Figure 50 As shown, it illustrates the total iodide recovered (squares) and removed (circles) from a 0.1 M Na3PO4 2 mM KI pH 7 solution after 2 and 4 cycles of iodide capture and emission. After 2 cycles, 5.5% of the initial iodide had been removed from the iodide capture solution, and 2.9% of the initial iodide had been recovered and reused in the recovery solution with an efficiency of 53%. After 4 cycles, a total of 10.3% of the initial iodide had been removed from the iodide capture solution, and 5.4% of the initial iodide had been recovered and reused in the recovery solution with an efficiency of 53%.

[0406] Example 18

[0407] Iodide was recovered and reused using anion exchange resins. A solution of 2 mM KI and 10 mM Na2SO4 was prepared using DI water. 300 mL of the solution and 0.5 g of commercially available AmberSep anion exchange resin in bead form (approximately 2 mm in diameter) were placed in separate bottles. 300 mL of the solution and 0.5 g of commercially available AmberLite anion exchange resin in bead form (approximately 2 mm in diameter) were placed in separate bottles. Both bottles were shaken for 24 hours to mix the solution and resin. After 24 hours, the solution containing AmberSep contained 0.94 mM iodide, indicating that 53% of the iodide had been removed. After 24 hours, the solution containing AmberLite contained 0.62 mM iodide, indicating that 69% of the iodide had been removed.

[0408] The iodide-loaded resins were filtered from the solution and washed with DI water. They were then placed in separate bottles containing 50 mL of 0.2 M KCl. Both bottles were shaken for 24 hours to mix the solution and resin. After 24 hours, the solution containing AmberSep contained 2.0 mM iodide, meaning 17% of the initial iodide had been recovered and reused. The solution containing AmberLite contained 1.91 mM iodide, meaning 16% of the initial iodide had been recovered and reused.

[0409] As used herein, the terms “substantially” or “approximately” refer to the degree or level of completeness or near-completeness of a behavior, feature, characteristic, state, structure, item, or result. For example, an object that is “substantially” or “approximately” enclosed means that the object is either completely enclosed or nearly completely enclosed. In some cases, the degree of deviation from absolute completeness may be permissible depending on the specific circumstances. However, a degree of near-completeness will result in an overall result that is substantially the same as obtaining absolute and complete completeness. The use of “substantially” or “approximately” also applies to situations with a negative connotation, indicating the complete or near-complete absence of a certain behavior, feature, characteristic, state, structure, item, or result. For example, an element, combination, embodiment, or composition that is “substantially free” or “approximately free” may actually still contain that element, provided that there is no significant effect thereon.

[0410] The present invention has been described in the foregoing specification with reference to specific embodiments. However, it is understood that various modifications and variations can be made without departing from the scope of the present invention.

Claims

1. A method for disrupting PFAS, comprising: Add sulfite to an aqueous solution containing PFAS; Then The aqueous solution was irradiated with 222 nm light.

2. The method of claim 1, further comprising adding a sufficient amount of alkali to the aqueous solution containing PFAS to raise the pH of the aqueous solution containing PFAS to about 10 or higher.

3. The method of claim 2, further comprising adding a halide salt to the aqueous solution containing PFAS.

4. The method according to claim 3, wherein the halide salt is a bromide salt.

5. The method according to claim 3, wherein the halide salt is an iodized salt.

6. The method of claim 3 further comprises adding a carbonate to the aqueous solution containing PFAS.

7. The method of claim 1, wherein irradiation of the aqueous solution destroys more than 90% of the PFAS in the solution.

8. The method of claim 1, wherein irradiation of the aqueous solution destroys more than 99% of the PFAS in the solution.

9. The method according to claim 1, further comprising: Before irradiating the aqueous solution containing PFAS, persulfate and acid or base are added to the aqueous solution containing PFAS to raise or lower the pH. Then The aqueous solution containing PFAS is placed at elevated temperature and pressure for a sufficiently long time to undergo thermal oxidation.

10. The method of claim 9, wherein the increased temperature comprises about 100 to about 140 degrees Celsius, and the increased pressure comprises about 1 to about 5 bar.

11. A photoreactor for destroying PFAS, comprising: A reactor vessel configured to receive an aqueous solution containing PFAS; A first light source, including an ultraviolet light source, is configured to deliver light of approximately 222 nm to the aqueous solution containing PFAS in the reactor vessel.

12. The photoreactor of claim 11, wherein the light source comprises a krypton / chlorine excimer lamp.

13. The photoreactor according to claim 11, further comprising: The second light source is also positioned to direct light onto the aqueous solution in the reactor vessel.

14. The reactor of claim 13, wherein the second light source is the same as the first light source.

15. The photoreactor according to claim 11, wherein the photoreactor is a continuous reactor.

16. The photoreactor of claim 15, wherein the reactor vessel comprises a stirred tank reactor vessel.

17. The photoreactor of claim 11 further comprises a sulfite source configured to deliver the sulfite to the aqueous solution upstream of the reactor vessel or within the reactor vessel.

18. The photoreactor of claim 17 further includes a source of a halide salt, the source of which is configured to supply the halide salt to the aqueous solution upstream of the reactor vessel or within the reactor vessel.

19. The photoreactor of claim 18 further includes a source of alkali configured to supply alkali to the aqueous solution upstream of or within the reactor vessel, such that the pH of the aqueous solution within the reactor vessel is approximately 10 or higher.

20. A system for disrupting PFAS, comprising: The pretreatment reactor includes: A pretreatment container, configured to contain an aqueous solution containing PFAS under pressure, and including a heating element to heat the aqueous solution contained therein; and A source of persulfate and acid or base, configured to deliver persulfate and acid or base to the aqueous solution before or within the pretreatment container; A photoreactor, downstream of the pretreatment reactor, the photoreactor comprising: A reactor vessel configured to receive an aqueous solution; Multiple ultraviolet light sources are configured to deliver 222 nm light to the aqueous solution containing PFAS in the reactor vessel; and A source of sulfite is configured to deliver the sulfite to the aqueous solution before or within the reactor vessel.

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