Method and system for removing nitrates in aqueous systems to improve PFAS breakdown

Abstract

A method, system, and apparatus for PFAS destruction, comprising: removing nitrates from water containing PFAS; preparing a treatment solution having a pH of about 10 or higher by combining the water with a sensitizer and a sufficient amount of base; and destroying a portion of the PFAS by irradiating the treatment solution with UV light in a photoreactor. The nitrates can be removed electrolytically, for example, by electrolytic reduction of the nitrates to nitrogen gas and / or ammonia. The nitrates can be removed by filtration with a selective membrane, such as reverse osmosis, forward osmosis, nanofiltration, and / or ultrafiltration. The system may include an electrolytic cell system comprising a first cell (having a cathode in contact with the water containing PFAS in the first cell), a second cell containing an anode in an electrolyte, a power supply, and brine and / or a membrane separating the first and second cells.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority to U.S. Provisional Application No. 63 / 513,782, filed July 14, 2023, Processes for Effective Photochemical Destruction of PFAS from Waste Streams; U.S. Provisional Application No. 63 / 591,040, filed October 17, 2023, Systems and Methods of PFAS Destruction; and U.S. Provisional Patent Application No. 63 / 635,938, filed April 18, 2024, all of which are incorporated herein by reference. [Background technology]

[0002] Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a type of synthetically produced compound that has been used in numerous consumer and industrial applications for decades. PFAS possess several inherent surface properties and can be both hydrophobic and oleophobic. As a result, PFAS are used as coating additives, lubricants, foaming aids, and various surface treatment agents. They have proven particularly useful as flame retardants in the form of aqueous film-forming foams (AFFFs). Furthermore, some PFAS are known to bioaccumulate in plants and animals. There is growing evidence that exposure to PFAS can also cause a variety of health problems. Due to these concerns, various regulatory bodies worldwide are beginning to establish strict limits on the presence of PFAS in food and water.

[0003] PFAS are a type of chemical substance containing a perfluoroalkyl group or polyfluoroalkyl group. The definition and classification of PFAS have changed over time. PFAS are defined as fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (without any H / Cl / Br / I atoms bonded to it), i.e., with a few notable exceptions, any chemical substance having at least a perfluorinated methyl group (-CF3) or a perfluorinated methylene group (-CF2-) is a PFAS. Some of the most important examples of PFAS include perfluorosulfonic acids (PFSAs), such as perfluorooctanesulfonic acid (PFOS), and perfluorocarboxylic acids (PFCAs), such as perfluorooctanecarboxylic acid (PFOA). Fluorotelomers are fluorocarbon oligomers or telomers synthesized by telomerization. Some fluorotelomers and fluorotelomer compounds are sources of environmentally persistent perfluorinated carboxylic acids, such as PFOA.

[0004] The persistence, health concerns, and regulatory landscape of PFAS have spurred significant research efforts to reduce their presence in the environment. Much of the early research focused on detecting them, for example, in drinking water. However, more recently, there has been a more intense effort to destroy these materials. One characteristic of PFAS is their resistance to degradation in the environment. PFAS are not readily metabolized by organisms and do not decompose upon exposure to visible light or longer-wavelength UV irradiation, which is typically found under terrestrial conditions.

[0005] Some methods proven effective for the decomposition (destruction) of PFAS include supercritical hydroxide oxidation (SCWO) and treatment of PFAS in aprotic polar solvents. SCWO works by heating water to 374°C under high pressure (over 3000 psi). Therefore, SCWO is very energy-intensive and can suffer from clogging problems. The use of SCWO often requires waste containing high solids content, as it depends on the heat capacity (btu) generated from this waste to make the process cost-effective. The advantage of SCWO lies in its short residence time to become effective, ranging from 30 seconds to several minutes. The use of basic aprotic media to decompose PFAS is hampered by the fact that most waste streams are aqueous and therefore do not readily migrate to aprotic media that require minimal water levels. In other cases, it has also been shown that PFAS compounds are decomposed by generating subcritical water conditions in an alkaline environment. This process, called hydrothermal alkali treatment (HALT), is carried out at a temperature of about 350°C and a pressure of about 2400 psi.

[0006] Other processes for breaking down (degrading) PFAS include the use of electrochemistry. Electrochemical degradation can break down long-chain PFAS (e.g., PFOS and PFOA), while short-chain PFAS are less susceptible. It is hypothesized that longer-chain PFAS readily aggregate on electrodes and are therefore readily oxidized or reduced. Other studies have shown that sonication can lead to PFAS degradation.

[0007] Improved processes are needed to efficiently and effectively destroy PFAS, especially PFAS in water. [Overview of the project]

[0008] Various embodiments disclosed herein include methods, systems, and apparatus for PFAS destruction using UV irradiation at 222 nanometers. For example, some embodiments include a method for PFAS destruction comprising adding a sulfite to an aqueous solution containing PFAS, and then irradiating the aqueous solution with light at 222 nm. This method may also include adding a base to the aqueous solution containing PFAS in an amount sufficient to raise the pH of the aqueous solution to about 10 or more. This method may also include adding a halide salt, such as a bromide salt or iodide salt, to the aqueous solution containing PFAS. Some embodiments also include adding a carbonate to the aqueous solution containing PFAS. Irradiation of the aqueous solution can destroy more than about 90% of the PFAS in the solution, or more than about 99% of the PFAS in the solution. In some embodiments, this method also includes adding persulfates and acids or bases to the aqueous solution containing PFAS to raise or lower the pH before irradiating the aqueous solution containing PFAS, and then exposing the aqueous solution containing PFAS to the increased temperature and increased pressure for a period of time sufficient for thermal oxidation. For example, the increased temperature may be approximately 100 to 140°C, and the increased pressure may be approximately 1 to 5 bar.

[0009] Various embodiments include a photoreactor for PFAS destruction, comprising a reaction vessel configured to receive an aqueous solution containing PFAS, and a first light source including an ultraviolet light source configured to deliver light of about 222 nm to the PFAS-containing aqueous solution in the reaction vessel. In some embodiments, the light source may be a krypton / chloride excimer lamp. The photoreactor may also include a second or more light sources arranged to guide light to the aqueous solution in the reaction vessel, and these light sources may be identical to the first light sources. In some embodiments, the reaction vessel may be a continuous reactor, such as a stirred-tank reaction vessel. Some embodiments may also include one or more sources of sulfites and / or halides configured to deliver sulfites and / or halides to the aqueous solution upstream of the reaction vessel, before entering the reaction vessel, or within the reaction vessel. Some embodiments may also include a source of bases configured to deliver a base to the aqueous solution upstream of the reaction vessel, before entering the reaction vessel, or within the reaction vessel, such that the aqueous solution has a pH of about 10 or higher within the reaction vessel.

[0010] Other embodiments include a system PFAS decompression comprising a pretreatment vessel configured to contain an aqueous solution containing PFAS under high pressure and including a heating element for heating the aqueous solution contained therein; a pretreatment reactor comprising a persulfate and acid or base supply configured to deliver persulfate and acid or base to the aqueous solution in front of or within the pretreatment vessel; and a photoreactor downstream of the pretreatment reactor. The photoreactor may comprise a reaction vessel configured to receive the aqueous solution; a plurality of ultraviolet light sources configured to deliver 222 nm light to the aqueous solution containing PFAS in the reaction vessel; and a sulfite supply configured to deliver sulfite to the aqueous solution in front of or within the reaction vessel.

[0011] Some embodiments include methods, systems, and apparatus for the oxidative pretreatment of aqueous solutions containing PFAS. For example, in some embodiments, the PFAS destruction method includes oxidative pretreatment of an aqueous foam separation solution containing PFAS to form a pretreatment solution, wherein the step of oxidative pretreatment of the aqueous foam separation solution includes mixing the aqueous foam separation solution with a persulfate and an acid or base to raise or lower the pH, then oxidizing the aqueous foam separation solution, and subjecting the pretreatment solution to UV photodegradation. UV photodegradation may include directing UV light of 222 nm and / or 254 nm and / or 185 nm onto the pretreated aqueous foam separation solution. In some embodiments, oxidizing the aqueous foam separation solution includes exposing the aqueous foam separation solution to an elevated temperature and elevated pressure for a period sufficient for thermal oxidation. For example, the elevated temperature may be about 100 to about 140°C, and / or the elevated pressure may be about 1 to about 5 bar. In some embodiments, oxidizing the aqueous foam separation solution includes subjecting the aqueous foam separation solution to ozone oxidation. In some embodiments, the method also includes separating solid particles from the aqueous foam separation solution before and / or after oxidative pretreatment of the aqueous foam separation solution.

[0012] In various other embodiments, the PFAS destruction method involves mixing the aqueous foam separation solution with a persulfate and an acid or base to raise or lower the pH, subjecting the aqueous foam separation solution to thermal oxidation at a temperature of about 100 to about 140°C and a pressure of about 1 bar to about 5 for a sufficient amount of time, and subjecting the pre-treated solution to UV photodegradation at about 222 nm. The persulfate may be, for example, potassium persulfate, sodium persulfate and / or aluminum persulfate. The persulfate may be added to the aqueous foam separation solution to achieve a concentration of about 100 to about 200 mM in the aqueous foam separation solution. In some embodiments, an acid is mixed into the aqueous fractionation solution to lower the pH of the aqueous foam separation solution to about 2 to about 4, etc. In other embodiments, a base is mixed into the aqueous foam separation solution to raise the pH of the aqueous foam separation solution to about 10 to about 14, etc.

[0013] Various other embodiments include a system for pretreatment of PFAS-containing water, comprising a pretreatment reactor configured to contain PFAS-containing water under high pressure and including a heating element for heating the PFAS-containing water contained therein, and a persulfate and acid or base supply configured to deliver persulfates and acids or bases to the PFAS-containing water upstream of or within the pretreatment vessel. The system may also include a sedimentation tank upstream or before and / or downstream or after the pretreatment reactor. In some embodiments, the pretreatment reactor may also be a photoreactor and may include a UV light source configured to induce UV light in the PFAS-containing water after pretreatment. For example, the UV light supply source may emit UV light with a peak at about 222 nm.

[0014] Other embodiments include methods, systems, and apparatus for photoelectrochemical PFAS destruction. Various embodiments include a photoelectrolytic apparatus for destroying PFAS, comprising a photoreactor vessel configured to receive an aqueous solution containing PFAS; a UV light source configured to direct UV light into the aqueous solution containing PFAS in the photoreactor vessel; a cathode in the photoreactor vessel configured to contact the aqueous solution containing PFAS in the photoreactor vessel; an anode in an electrolyte; a power supply configured to provide a voltage difference between the anode and the cathode; and a membrane or ion bridge between the anode and the cathode. The UV light source may be, for example, a mercury lamp having an emission peak at about 185 nm and / or 254 nm, or a krypton / chloride excimer lamp having an emission peak at about 222 nm. In some embodiments, the UV light source may include a UV lamp in a quartz tube immersed in the photoreactor vessel. For example, the quartz tube may be placed at a distance of about 2 cm or less from the cathode. In some embodiments, the cathode may be a doped diamond cathode. In some embodiments, the cathode may be a platinum, titanium, and / or stainless steel electrode. In various embodiments, the cathode may include a mesh material. In some embodiments, the cathode may include a high surface area structure having an electrochemically active surface and a geometric surface area, where the electrochemically active surface area is greater than the geometric surface area. In some embodiments, the apparatus may also include an inert gas source connected to the photoreactor vessel and configured to bubble through an aqueous solution containing PFAS in the reaction vessel and / or through the anode electrolyte. In some embodiments, the photoelectric reaction vessel may be a continuous reactor, such as a stirred-tank reactor.

[0015] Other embodiments include a photoelectrolytic device for destroying PFAS, comprising: a photoreactor vessel configured to receive an aqueous solution containing PFAS; a UV light source in a tube within the photoreactor vessel configured to guide UV light into the aqueous solution containing PFAS within the photoreactor vessel; a cathode within the photoreactor vessel configured to contact the aqueous solution containing PFAS within the photoreactor vessel, located within about 2 cm from the UV light source, and having a high surface area structure with an electrochemically active surface area greater than its geometric surface area; an anode in an electrolyte; a power supply configured to provide a voltage difference between the anode and the cathode; and a membrane or ion bridge between the anode and the cathode. The UV light source may be, for example, a mercury lamp having an emission peak at about 185 nm and / or 254 nm, or a krypton / chloride excimer lamp having an emission peak at about 222 nm. In some embodiments, the photoreactor vessel may be a stirred-tank reactor.

[0016] Other embodiments include a method for destroying PFAS in a photoelectrolyzer, comprising the steps of supplying water containing PFAS to a photoelectrolyzer, wherein the photoelectrolyzer includes a photoreactor vessel configured to receive an aqueous solution containing PFAS, a UV light source, a cathode located within the photoreactor vessel and in contact with the aqueous solution containing PFAS in the photoreactor vessel, an anode in a cell containing an aqueous electrolyte, a power supply 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 supply to generate a voltage difference between the anode and the cathode; and irradiating the water containing PFAS in the reaction vessel with UV light. The steps of applying power and irradiating the water may be performed, for example, as simultaneous or overlapping steps. This method may also include continuously flowing water containing PFAS into the photoreactor vessel. This method may also include generating hydrogen gas at the cathode. In some embodiments, this method also includes mixing the aqueous solution containing PFAS with the electrolyte, and the destruction of PFAS is performed without the addition of a sensitizer. In some embodiments, this method also includes mixing an aqueous solution containing PFAS with a sensitizer and an electrolyte. In some embodiments, this method also includes mixing an aqueous solution containing PFAS with a sulfite and a halide salt. In some embodiments, this method also includes 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 a halide. For example, in some such 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, this method also includes mixing an aqueous solution containing PFAS with a sulfite and an electrolyte, and applying a voltage between the anode and cathode sufficient to reduce a sulfite radical anion or dithionate to a sulfite ion.

[0017] Various other embodiments include methods, systems, and apparatus for nitrate removal in aqueous systems to improve PFAS breakdown. Various embodiments include methods for PFAS breakdown that include removing nitrates from water containing PFAS, preparing a treatment solution having a pH of about 10 or higher by combining the water containing PFAS with a sensitizer and a sufficient amount of base, and irradiating the treatment solution with UV light in a photoreactor to break down a portion of the PFAS. In some embodiments, removing nitrates from water containing PFAS includes electrolytic removal of nitrates from water containing PFAS. For example, in some embodiments, electrolytic removal of nitrates includes electrolytic reduction of nitrates to nitrogen gas and / or ammonia. This method may include bringing water containing PFAS into contact with an electrode and applying an electric current to the electrode. The electrode may be, for example, an iron, copper, or iron:copper electrode. The electrode may also be the cathode of an electrolytic cell system which also includes an anode in an aqueous electrolyte. In some such embodiments, this method may also include forming oxygen gas at the anode while reducing nitrates at the cathode. In various other embodiments, the removal of nitrates from water containing PFAS may involve filtration by a selective membrane. Examples of selective membranes that may be used include reverse osmosis, forward osmosis, nanofiltration (NF), and / or ultrafiltration (UF). In various embodiments, the removal of nitrates from water containing PFAS is a pretreatment step before irradiation of the treatment solution. In various other embodiments, the removal of nitrates from water containing PFAS is a step performed in a photoreactor.

[0018] Various embodiments include a method for destroying PFAS, comprising contacting water containing PFAS with a cathode; applying an electric current to the cathode to electrolytically reduce nitrates in the water containing PFAS; combining the water containing PFAS with sulfites, halides, and a sufficient amount of base to prepare 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, the halides may be iodides, and the UV light may be light having an emission peak at about 222 nm. In some embodiments, the method also includes oxidative pretreatment of the water containing PFAS before irradiating the PFAS. In some such embodiments, oxidative pretreatment of the water containing PFAS includes mixing the water containing PFAS with persulfates and an acid or base, and then exposing the water to an increased temperature and increased pressure.

[0019] Various embodiments include a system for destroying PFAS in water, comprising a nitrate removal system configured to remove nitrates from water containing PFAS and nitrates, comprising a selective membrane and / or an electrolytic cell system, and a photoreactor comprising a reaction vessel configured to contain an aqueous solution and an ultraviolet light source positioned to direct light onto the contents of the reaction 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 comprising a cathode configured to contact water containing PFAS in a first cell, a second cell comprising an anode in an electrolyte, a power supply, and brine and / or a membrane separating the first and second cells. In some embodiments, the cathode is located in the photoreactor, and the photoreactor vessel forms the vessel of the first cell. In various embodiments, the cathode may include, for example, iron, copper and / or iron:copper.

[0020] Other embodiments include methods, systems, and apparatus for capturing iodine from aqueous solutions. Various embodiments include a method for removing iodide from an aqueous solution, comprising immersing an iodine-affinity electrode in an aqueous solution containing iodide, applying an electric current to the electrode, and electrochemically oxidizing the iodide to iodine within the electrode. This method may also include adjusting the pH of the aqueous solution to about 3 to about 8. In some embodiments, the step of applying an electric current generates a voltage of 0.3 V or higher for Ag / AgCl. In various embodiments, the iodine-affinity electrode comprises an iodine-affinity material and a conductive material. For example, the iodine-affinity material may be cellulose, starch, cationic polymer, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene), metallocene, metallocene-containing polymer, and / or cationic metal complexes. In some embodiments, the iodine-affinity electrode may also include a binder material. In some embodiments, the iodine-affinity material may include starch, chitosan, or carboxycellulose. In some embodiments, the iodine-affinity material may be a cationic polymer. In some embodiments, the iodine-affinity material may be an anion exchange membrane. In some embodiments, the conductive material may be graphite, graphene, carbon nanotubes, conductive polymers, or doped semiconductors and / or metals. In some embodiments, the binder may be polyvinylidene fluoride (PVDF), polyfluoroethylene (PTFE), styrene-butadiene rubber, and / or polyamide. In some embodiments, the aqueous solution may be water after treatment by UV photodegradation for the breakdown of PFAS. In some such embodiments, the method may further include removing the electrode from the aqueous solution, then immersing the electrode in a second solution, then applying an electric current to the electrode to reduce iodine and release it from the electrode into the second solution in the form of iodide.

[0021] Other embodiments include a method for capturing and recirculating iodide from a photochemical advanced reduction process (ARP) solution, comprising: receiving a photochemical ARP solution produced by the ARP process; adjusting the pH of the photochemical ARP solution to about 4 to about 8; then contacting the ARP solution with the ion exchange medium for a time sufficient for the ion exchange medium to bind to the iodide; and then contacting the ion exchange medium with a salt solution to remove the bound iodide. In some embodiments, the ion exchange medium contains quaternary ammonium groups. In some embodiments, the salt solution is a mixture of water and 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.

[0022] Other embodiments include a system for recovering iodine from an aqueous solution comprising an iodine-affinity electrode containing an iodine-affinity material, a conductive material, a binder, and a current collector, wherein the electrode is coupled to the current collector. In some such embodiments, the iodine-affinity material is 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 conductive material is graphite, graphene, carbon nanotubes, conductive polymers, and / or doped semiconductors or metals. In some embodiments, the binder is polyvinylidene fluoride (PVDF), polyfluoroethylene (PTFE), styrene-butadiene rubber, and / or polyamide.

[0023] Other embodiments include methods, systems, and apparatus for recirculating the material during PFAS destruction. Various embodiments include a method for PFAS destruction, comprising: a) supplying water containing PFAS to a reaction vessel; b) irradiating the water in the reaction vessel with UV light under conditions that destroy at least a portion of the PFAS to form treated water; c) passing the treated water through a selective membrane to form a permeate and a membrane rejection containing PFAS; d) returning the membrane rejection to the reaction vessel; e) supplying additional water containing PFAS to the reaction vessel, wherein the membrane rejection and the additional water containing PFAS are combined in or before being supplied to the reaction vessel; and f) irradiating the membrane rejection and the additional water containing PFAS in the reaction vessel with UV light. This method may further include repeating the steps multiple times so that undestroyed PFAS is recirculated through the reaction vessel. In some embodiments, this method also includes adding a sensitizer to the water containing PFAS before step b). In some such embodiments, the membrane rejection also includes the sensitizer. In some such embodiments, the selective membrane may be a reverse osmosis membrane or a nanofiltration membrane. For example, in some such embodiments, the selective membrane rejects at least about 99% of PFAS and sensitizer. In some embodiments, the method also includes adding an additional sensitizer to the additional water or membrane rejection material containing PFAS before step f). In various embodiments, the sensitizer includes, for example, a halide salt such as iodide. In some embodiments, the method also includes removing sulfates from the membrane rejection material before step d). For example, removing sulfates includes adding calcium to the membrane rejection material to form a sulfate precipitate and separating the sulfate precipitate from the membrane rejection material. In some embodiments, the method also includes passing the membrane rejection material through a water softener before step d to remove calcium, magnesium and / or iron.

[0024] Various embodiments include a method for destroying PFAS, comprising: a) providing water containing PFAS to a reaction vessel; b) adding sulfites and halides to the water containing PFAS either before step a) or inside the reaction vessel to form a reaction solution; c) irradiating the reaction solution in the reaction vessel with UV light under conditions that destroy at least a portion of the PFAS to form a treatment solution; d) passing the treatment solution through a selective membrane to form a permeate, thereby forming a membrane rejection product containing residual PFAS and halides, wherein the selective membrane removes more than about 99% of the residual PFAS and halides present in the treatment solution; and e) providing the membrane rejection product to the reaction vessel or a separate reaction vessel. This method may further include a step of discharging the permeate into the environment. In some embodiments, the steps can be carried out sequentially.

[0025] Other embodiments include a system for PFAS destructuring, comprising a photoreactor including a reaction vessel configured to receive water containing PFAS; a UV light source configured to direct UV light into the water containing PFAS in the reaction vessel; a selective membrane fluidly communicating with the photoreactor and located downstream or after the photoreactor, which is selective for more than 99% of the PFAS present in the water containing PFAS after photodegradation in the photoreactor; and means for fluidly transporting the membrane rejects formed by the selective membrane to a location upstream of the photoreactor for further transport into or direct transport to the photoreactor. The selective membrane may be, for example, a reverse osmosis membrane or a nanofiltration membrane. The system may also include a sedimentation system downstream of the selective membrane along a membrane rejection discharge path before transporting the membrane rejects to the photoreactor. In some embodiments, the system may also include a water softener downstream or after the sedimentation system and before transporting the membrane rejects to the photoreactor. In various embodiments, the reaction vessel may be a continuous reactor.

[0026] The following drawings are illustrative of embodiments and do not limit the scope of the present invention. The drawings are not necessarily to scale and are intended to be used in conjunction with the following detailed description. Embodiments of the present invention are described with reference to the drawings, where similar reference numerals may represent similar elements. [Brief explanation of the drawing]

[0027] [Figure 1] This is a schematic diagram showing an example of an integrated system incorporating pretreatment, photodegradation, and posttreatment according to various embodiments.

[0028] [Figure 2] These are schematic diagrams of electrolytic coal in various embodiments.

[0029] [Figure 3] These are schematic diagrams of electrolytic cells for nitrate reduction according to various embodiments.

[0030] [Figure 4] This figure shows a method for integrating filtration and photodestruction according to various embodiments.

[0031] [Figure 5] This is a flowchart of the process of PFAS breakdown in wastewater.

[0032] [Figure 6] This is a flowchart of the process for PFAS breakdown in wastewater streams, including thermal oxidation pretreatment.

[0033] [Figure 7] This is a flowchart showing the breakdown of PFAS in wastewater streams containing ozone oxidation.

[0034] [Figure 8] This figure shows an example of a UV reactor as the photochemical component of a processing system.

[0035] [Figure 9] This is a schematic diagram of another embodiment of a photoelectrolytic cell according to various embodiments.

[0036] [Figure 10] This figure shows the chemical structures of examples of polymers that can be used in various embodiments.

[0037] [Figure 11] This figure shows the chemical structures of further examples of polymers that can be used in various embodiments.

[0038] [Figure 12] This figure shows examples of polymer n-type organic semiconductor structures that can be used in various embodiments.

[0039] [Figure 13] This figure shows examples of oxidation of disodium salts bonded to polymers using various embodiments.

[0040] [Figure 14] This figure shows an example of a chemically structured polymer that can be used in various embodiments.

[0041] [Figure 15] This figure shows an example of the chemical structure of a polymer having oxidizable units that can be used in various embodiments.

[0042] [Figure 16] This figure shows an example of a system for electrochemically regenerating reduced iodide from iodine or iodine radicals.

[0043] [Figure 17] This figure shows examples of the electrochemical regeneration of oxidized iodide using various embodiments.

[0044] [Figure 18] This figure shows another example of a system for electrochemically regenerating oxidized iodide according to various embodiments.

[0045] [Figure 19] This figure shows the use of electrochemical systems to locally change the pH of a solution according to various embodiments.

[0046] [Figure 20] This is a schematic diagram of an example of a system for 185mm photoelectrolytic irradiation accompanied by hydrogen generation, according to various embodiments.

[0047] [Figure 21] This figure shows the reaction resulting from the absorption of 185nm light by water.

[0048] [Figure 22] This is a schematic diagram of a non-electrochemical system for iodine reduction according to various embodiments.

[0049] [Figure 23] This figure shows the chemical structure of polyvinylferrocene, which can be used in various embodiments.

[0050] [Figure 24] This figure shows the chemical structure of a polymer having a tetramethylpiperidine 1-oxyl (TEMPO) side chain, which can be used in various embodiments.

[0051] [Figure 25] This figure shows an example of a process for the destruction of PFAS, including the use of aromatic compounds.

[0052] [Figure 26] This figure shows an overview of the post-processing process.

[0053] [Figure 27] This figure shows an example of an electrolytic cell for iodide recovery.

[0054] [Figure 28]This figure shows an example of a PFAS treatment method that is completed in a post-treatment step and a subsequent finishing step.

[0055] [Figure 29] This figure shows a graph of the total PFAS defluorination rate when the electrochemical nitrate reduction pre-step was performed and when it was not performed in the example.

[0056] [Figure 30] This figure shows the dependence of the NO3 concentration (ppm) on the enrichment factor of membrane rejects using RO and NFX in the example.

[0057] [Figure 31] This figure shows a graph comparing the defluorination rates from photoreduction of film rejects from RO films and NFX films.

[0058] [Figure 32] This figure shows a series of photographs of wastewater during PFAS breakdown, including thermal oxidation pretreatment.

[0059] [Figure 33] This figure shows graphs of the UV transmittance spectra of untreated wastewater, as well as wastewater diluted 0, 2, 5, and 10 times with thermal oxidation and DI water.

[0060] [Figure 34] This figure shows a series of graphs of the total PFAS destruction rates by UV222 and UV254 photoreduction processes at various dilution ratios of wastewater samples pretreated by thermal oxidation.

[0061] [Figure 35] This figure shows a series of photographs of wastewater during PFAS decomposition, including ozone oxidation pretreatment.

[0062] [Figure 36]This figure shows a pair of graphs representing the percentage of total PFAS destruction over time by UV222 and UV254 photoreduction processes for ozone-oxidized samples, at 10x and 5x dilution ratios.

[0063] [Figure 37] This figure shows a pair of bar graphs representing the PFAS destruction results obtained by photoreduction treatment at UV222nm and UV254nm after pretreatment by thermal oxidation or ozone oxidation.

[0064] [Figure 38] This figure shows photographs of wastewater samples subjected to thermal oxidation with various doses of potassium persulfate and sodium hydroxide.

[0065] [Figure 39] This figure shows bar graphs of PFAS breakdown in wastewater using photoreduction and different photosensitizer concentration levels.

[0066] [Figure 40] This figure shows graphs of concentration as a function of time for photoreduction of PFAS solutions at 222 nm, for six different solutions.

[0067] [Figure 41] This figure shows a graph of the PFAS destruction rate as a function of time for photoreduction of PFAS solutions at 222 nm, for six different solutions.

[0068] [Figure 42] This figure shows a graph of the PFAS destruction rate as a function of time using 222nm photoreduction, compared to direct irradiation.

[0069] [Figure 43] This figure shows a graph of data-fitted data using a single exponential function for time-dependent PFAS breakdown using 1 mM KI, 5 mM Na2SO3, and bicarbonate solutions.

[0070] [Figure 44] This figure shows a graph of the time-dependent breakdown of PFOA during photodegradation at 222 nm using 5 mM Na2SO3 and 150 mM KBr or 5 mM Na2SO3 alone.

[0071] [Figure 45] This figure shows a graph of the time-dependent fluoride ion concentration during photodecomposition at 222 nm using 5 mM Na2SO3 and 150 mM KBr or 5 mM Na2SO3 alone.

[0072] [Figure 46] This figure shows graphs of PFAS breakdown and PFAS concentration versus time for UV breakdown of foam separation water samples at 222 nm and 254 nm.

[0073] [Figure 47] This figure shows a graph of experimental results for the recycling of iodide without the use of sulfites, by electrochemical reduction of photochemically generated iodine radicals.

[0074] [Figure 48] This figure shows a graph of PFOS destruction using electrochemically generated hydrogen gas.

[0075] [Figure 49] This figure shows graphs of experimental results from oxidation (left) and reduction (right) linear sweep voltammetry using an iodide recovery electrode.

[0076] [Figure 50] This figure shows a graph of the experimental results for the removal and recovery of all iodide using an iodide recovery electrode. [Modes for carrying out the invention]

[0077] The systems and methods described herein relate to processes for the photochemical destruction of PFAS. More specifically, the systems and methods relate to a class of UV photochemical destruction called UV-based advanced reduction treatment (UV-ARP). The UV-ARP method is based on the generation of potent reducing species, such as solvated electrons, produced by irradiation with a photosensitizer. The photosensitizer or sensitizer absorbs UV energy and generates solvated electrons and oxidative sensitizer species. The solvated electrons can react with PFAS molecules.

[0078] Various embodiments include processes that enhance the efficiency of photochemical decomposition of PFAS and enable the more common use of photochemical methods in various PFAS-containing waste flows. Other embodiments include the design of UV photodecomposition reactors to achieve more efficient decomposition of PFAS. Still other embodiments include systems and methods for recovering high-value materials after UV photodecomposition of PFAS materials. Other embodiments include systems and methods for further treatment of waste flows after UV photodecomposition before release into the environment or for reuse in industrial applications.

[0079] Various embodiments include the photochemical decomposition of PFAS as a method for destroying so-called “eternal chemicals.” In some embodiments, the photochemical system includes a reaction vessel equipped with one or more UV light sources. The reactor may be filled with a liquid consisting of one or more PFAS, water (or another solvent), and a sensitizer that can absorb UV light to generate reactant species. Furthermore, one or more other chemical additives may be optionally present to facilitate the reaction. The processes, systems, and methods disclosed herein result in improved efficiency, reduced costs, and reduced use of chemicals. In some embodiments, the materials used in the process can be recycled and reused, further increasing efficiency and lowering costs. Further embodiments involve treating the photodegraded solution so that the solution can be recycled, further purified, or disposed of.

[0080] Various embodiments involve the use of ultraviolet-based advanced reduction treatment processes (UV-ARP), which may be effective for treating certain classes of persistent chemical contaminants in water. Advanced reduction treatment processes are based on the generation of strongly reducing hydrated electrons that exhibit fast bimolecular reaction rate constants with inorganic and organic compounds. In UV-ARP, solvated electrons can be generated by irradiation of a sensitizer that can generate solvated electrons when irradiated with a UV light source. The photogenerated solvated electrons generated by the systems and methods described herein can react with PFAS and other contaminants, resulting in the breakdown of PFAS.

[0081] The results of UV-ARP indicate mineralization of PFAS by converting the carbon-fluoride bond to fluoride ions and carbon species, such as acetates, formates, carbon dioxide, short-chain PFAS molecules, other polyfluoride molecules, and / or carbonates. In this regard, mineralization is due to the conversion of fluoride ions F of the carbon-bonded fluorine on PFAS. - It means a reduction to.

[0082] In some embodiments, UV-ARP can be used to directly treat PFAS present in wastewater or other water sources in high-throughput treatment systems, etc. In other embodiments, UV-ARP can be used to treat PFAS extracted or absorbed from the environment, such as wastewater or other water sources, isolated, and / or concentrated. This PFAS can be suspended or dissolved in an aqueous solution for use in the UV-ARP methods and systems described herein.

[0083] The PFAS destruction methods and systems described herein include the ability to destroy PFAS contaminants, including 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), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonic acid (PFOS). Two or more PFAS can be treated and destroyed simultaneously using the photoreaction methods described herein.

[0084] Destruction of PFAS involves altering the identity of the target chemical contaminant through the cleavage of chemical bonds. Destruction that results in complex chemical compounds as the final product is called decomposition. Destruction includes removing one or more chemical groups to reduce or eliminate toxicity.

[0085] The PFAS used in the various embodiments may be present in aqueous solutions of PFAS present in water from contaminated natural sources or other sources, or may be concentrated by prior capture or pretreatment methods or other treatment methods.

[0086] Some embodiments include an electrochemical system for converting photochemical byproducts back into the original sensitizer and preventing the accumulation of significant concentrations of solvated electron-capturing species.

[0087] Compared to other contaminants, there are relatively few processes for destroying PFAS. Since photodegradation of solvated electrons is one of these methods, it is beneficial to minimize potential interference with photochemical processes. Therefore, in some cases, it may be desirable to pre-treat the waste stream using other processes to allow the photodegradation reaction to proceed with maximum efficiency. Furthermore, the photodegradation reaction for efficient solvated electron generation may require highly alkaline conditions, such as a pH greater than 10 or 12. Additionally, other inorganic salts can be added to remove photoproducts and minimize the concentration of molecular oxygen. As a result, the concentration of inorganic ions can become very high. PFAS destruction is also achieved by inorganic fluoride anions (F). - ) are generated. Therefore, it may be desirable to reduce the concentration of potentially corrosive or other undesirable species in order to dispose of the waste stream after photolysis. Also, even if photolysis can remove more than 90%, often more than 99%, of PFAS, it may still be beneficial to further reduce PFAS concentrations using other separation techniques, such as complying with regulatory limits or shortening reactor time. Many of these processes, such as ion exchange techniques, reverse osmosis, or granular activated carbon (GAC) beds used to further reduce PFAS concentrations, can be adversely affected by the presence of competing ionic species. Therefore, reducing the ionic load may also be beneficial in order to effectively deploy these techniques.

[0088] For these reasons at least, an effective system for photochemically destroying PFAS may consist of the following steps: pretreatment, followed by photodegradation, followed by posttreatment, and then optionally a finishing step. Different systems and methods may be used for each of these steps in various combinations. Often, all steps may be used, but in other cases, the system of the method may not include all of these steps. Furthermore, the system and embodiments may further include fluid transport means, including pipes, pumps, valves, inlets, outlets, etc., for connecting the various components and connecting to and from the inlets and outlets of the various components. An example of an integrated system incorporating pretreatment, photodegradation, and pretreatment is shown in Figure 1.

[0089] <Pre-treatment process>

[0090] Various embodiments successfully implement UV-ARP by minimizing the time required for photochemical degradation of PFAS, including the use of pretreatment, and by minimizing reagent costs.

[0091] PFAS are found in many waste streams. Some common PFAS-containing waste streams that can be treated according to various embodiments include effluents from industrial producers of PFAS, effluents from textile mills, foam fractionation concentrates, aqueous film-forming foam (AFFF), AFFF rinses, landfill leachates, contaminated groundwater, municipal wastewater streams, and the bottoms of pot stills. Some of these waste streams can follow simple pretreatment protocols such as filtering. Other waste streams may require their own pretreatment, such as the removal of solvated electron scavengers, scattering materials, or UV absorbers. In some cases, pretreatment steps can be omitted, for example, when the composition of the waste stream is known and the properties of non-PFAS species are understood. One or more pretreatment systems and methods described herein may be used in various embodiments.

[0092] Solvated electrons react with a variety of naturally occurring chemical species in water. Any photochemical system that uses solvated electrons to react with PFAS may also be sensitive to other chemical species in the waste stream. These other chemical species can capture the solvated electrons. In fact, many common chemical contaminants react with solvated electrons faster than PFAS. Depending on the concentration and nature of these chemical species, the solvated electrons may preferentially react with these materials until these species are consumed. This can significantly increase the reaction time to break down the PFAS.

[0093] Therefore, in various embodiments, these contaminants may be preferentially consumed before the target PFAS. In some cases, the contaminants are present in sufficient quantities that PFAS breakdown does not occur or occurs very slowly over several days or weeks. Nitrates are an example of common contaminants in wastewater that readily react with solvated electrons and reduce UV efficiency. There are two reasons why nitrates can interfere with the photochemical breakdown of PFAS: 1) nitrates are efficient scavengers of electrons, and 2) nitrates have strong light absorption in the UV portion of the electromagnetic spectrum. UV photodegradation is one of the processes that can break down PFAS under ambient conditions, and since other contaminants can be efficiently removed by other processes, pretreatment steps can be used to remove these contaminants.

[0094] Various embodiments disclosed herein include systems and methods for oxidative pretreatment of wastewater streams containing PFAS prior to UV photoreduction. Examples of pretreatment processes include oxidation processes, including thermal oxidation and / or ozone oxidation. In some embodiments, thermal oxidation may involve mixing wastewater with a persulfate such as potassium persulfate or sodium persulfate, and a base or acid to raise or lower the pH of the wastewater, and treating the wastewater at high temperature and / or high pressure. In some embodiments, ozone treatment involves mixing wastewater with a base to raise the pH of the wastewater, followed by ozone treatment. After pretreatment, UV photoreduction of the wastewater may be more efficient, achieving a higher reduction rate of PFAS after photoreduction. For example, the thermal oxidation disclosed herein, using UV photoreduction at 222 nm, results in much more efficient PFAS breakdown, requiring far less dilution and thus making the photoreduction process much more efficient and cost-effective.

[0095] Pretreatment is beneficial because, in addition to the PFAS targets for UV photoreduction, the waste stream 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 chemical reactions occurring during UV photoreduction. Various embodiments include methods for reducing or eliminating the presence of these components, enabling more efficient subsequent PFAS photoreduction. The pretreatment processes described herein can remove solvated electron scavengers, scattering materials, and / or UV absorbers. This process and system enhances the efficiency of photochemical destruction of PFAS, enabling the more common use of photochemical methods in various PFAS-containing waste streams and reducing the time and cost required for PFAS destruction.

[0096] Pretreatment can improve light transmission, allowing UV light to penetrate the wastewater completely. At the same time, pretreatment may not interact with PFAS substances or remove them from the water components of the wastewater. Thus, since the PFAS components of the wastewater are not separated during pretreatment, treatment of not only the liquid components of the wastewater but also the PFAS separated from them becomes necessary, increasing complexity and cost. While pretreatment is not expected to result in the defluorination of PFAS, it may convert PFAS (such as telomers) into other PFAS that are more readily photoreduced. However, the primary purpose of pretreatment is to interact with, modify, or remove non-PFAS components of the wasteflow, as these components could otherwise hinder 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 increases light transmission without the separation of PFAS and the generation of interfering substances, resulting in a wasteflow that is more readily receptive to UV photoreduction and therefore more efficient.

[0097] The challenges to successfully implementing UV photoreduction of PFAS in wastewater include maximizing destructive performance, minimizing photochemical destructive time, and minimizing reagent costs. The pretreatment disclosed herein results in less dilution of the waste stream and more efficient UV photoreduction. As a result, this process requires less volume and uses fewer reagents overall.

[0098] Another problem associated with using UV-ARP is that the cost of sensitizers tends to dominate the bill of materials. Therefore, a practical and efficient method for recovering sensitizers or sensitizer precursors is desired.

[0099] In some cases, the composition of the waste stream is well understood, and steps can be taken to reduce potential scavengers. This may be the case with industrial waste streams where the reactants and products are known. In other cases, various embodiments can characterize the waste stream by one or more analytical techniques such as mass spectrometry, gas chromatography-mass spectrometry, multinuclear NMR, infrared spectroscopy, and / or UV absorption spectroscopy. Determination of the concentration and chemical composition makes it possible to treat the waste stream before UV photodegradation. Pretreatment of the waste stream before UV photodegradation can result in a significant reduction in the time required to break down PFAS.

[0100] In some embodiments, an intermediate step can be performed between multiple photoreactors in series. For example, photodegradation can be carried out in a first reactor. The waste stream can then be further processed in a second reactor (or further reactors in series) which may employ different processing conditions than the first reactor, such as different wavelengths of light, sensitizers, pH, and temperature.

[0101] In some embodiments, multiple pretreatment steps can be used before the photolysis process. For example, a clarification step can be used between the pretreatment process and the photolysis process, which may allow for the sedimentation and separation of solids from the wastewater.

[0102] Multiple techniques can be used to remove contaminants that capture active photochemical species. For example, nitrates and nitrites can be particularly problematic impurities in UV-ARP and can be reduced or removed in various embodiments before UV treatment. Other water impurities that also capture solvated electrons and can be removed by pretreatment in various embodiments include: 1) organic impurities such as chlorinated organic compounds (COCs) including chlorinated biphenyls, chlorinated dibenzodioxins, chloroform, tetrachloroethylene and other chlorinated solvents and washing fluids; and 2) halogen oxides: OCl - ClO2 - ClO3 - ClO4 - , OBr -, BrO2 - , BrO3 - , BrO4 - , IO - , IO2 - , IO3 - , IO4 - or their corresponding conjugate acids, but are not limited thereto. <00007​​​​​​​​​​​​​​In some embodiments, hydrogen gas can be used as a reducing agent. For example, hydrogen gas can be bubbled into the solution or generated electrochemically and used in combination with the catalyst system described above as a pretreatment to remove non-PFAS contaminants. Various embodiments may include monometallic systems, and other embodiments may include bimetallic catalysts for selective reduction. Examples of bimetallic catalysts that can be used in various embodiments include a first metal such as a noble metal such as Pd or Pt, and a second metal (co-catalyst metal) such as Cu, Sn, or In. Combinations such as a bimetallic catalyst in which the first metal is Rh, Ru, or Ir and the second metal (co-catalyst metal) is Ni, Ag, Zn, or Fe can also be used.

[0106] Like bromates, halogen oxides are catalytically reduced at room temperature and pressure by many metals, including Pd, Pt, Ir, Rh, Ru, Fe, Sn, Cu, Zu, and Ni, supported on activated carbon, as well as by hydrogen gas. All of these catalysts are active in the conversion of bromates to bromides. Ruthenium, palladium, platinum, and rhodium are the most efficient, with platinum showing the best activity. Halogen oxides can also be reduced electrochemically. Organometallic rhenium catalysts deposited on Ti4O7 reactive electrochemical films are used in ClO4 - Aqueous solution of Cl - It was effective in electrocatalytically reducing them. Sulfite ions can also reduce the number of halogen oxides to benign species such as halides.

[0107] <Electrochemical pretreatment> In some embodiments, pretreatment of the waste flow can be carried out using electrochemistry. Since electrochemistry may only break down longer-chain PFAS (e.g., PFOS or PFOA), it may not constitute an efficient solution for completely destroying PFAS. However, in various embodiments, electrochemistry can be used as a pretreatment step to partially react PFAS into a form that is susceptible or more susceptible to the subsequent UV-ARP process. In this regard, for example, pre-reacting various telomers can significantly reduce photodegradation time and maximize process efficiency.

[0108] <Nitrate pretreatment> Various embodiments include pretreatment of the waste stream to remove nitrates and nitrites. One or more methods can be used, including chemical reduction, ion exchange membranes, electrodialysis, electrochemical reduction, photochemical reduction, and bioremediation in which nitrates or nitrites are broken down by organisms. In principle, any of these methods may be effective, but an important consideration is to minimize the formation of potential products that may efficiently capture electrons, such as other nitrogen oxides, or products with UV absorption transitions that may reduce the amount of light that can be absorbed by the sensitizer. If the concentrations of potentially interfering chemical species are determined, chemicals can be added that convert these contaminants into materials that do not react with or react less readily with solvated electrons.

[0109] In some embodiments, pretreatment for reducing or removing nitrates may include reducing the nitrates to molecular nitrogen or ammonia. For example, in acidic solutions, nitrates may be reduced as pretreatment by, for example, formic acid, iron metal or zero-valent iron, aluminum-iron alloys, methanol and ammonium ions. In basic solutions, nitrates may be reduced by, for example, aluminum powder, zinc and iron metal or zero-valent iron, Fe 2+The material can be chemically reduced as a pretreatment with components such as, but not limited to, ammonia, hydrazine, glucose, hydrogen, and thiosulfates. In some embodiments, these reactions can be accelerated using a suitable catalyst. Examples of suitable catalysts that can be used in various embodiments include palladium-supported carbon.

[0110] In some embodiments, the photochemical process may be used alone or in combination with pretreatment for the reduction of nitrates. For example, in some cases, the addition of an inorganic photocatalyst such as titanium dioxide, iron, or manganese may be used in the photoreactor to selectively reduce and remove nitrates and nitrites before the addition of hydration electron-generating species for the reduction of PFAS. In other embodiments, an organic acid or base, including but not limited to oxalic acid and / or formate, may be added to the photochemical reactor and treated under UV light as a means of removing nitrates. The inorganic and organic photocatalysts may be used in separate UV reactors or in combination in the same UV reactor used for PFAS reduction.

[0111] In some embodiments, an electrochemical process for reducing nitrates and other contaminants can be used to treat nitrates or nitrites in water. For example, this method can use a system comprising three components: 1) a cathode where reduction occurs, 2) an anode where oxidation occurs, and 3) an electrolyte that can assist ion transport.

[0112] Various embodiments may include the electrochemical reduction of nitrates to nitrogen gas and may include numerous reactions, products, and intermediates (e.g., ammonia, nitrites, hydrazine, hydroxylamine, nitric oxide, and nitrous oxide). However, N2 and NH3 / NH4 + This is nitrogen in its thermodynamically most stable form under standard conditions. Electrochemical nitrate reduction in various embodiments can be described by the following reactions. 2NO3 - +12H + +10e -→N2+6H2O E 0 = 1.17V / SHE NO3 - +9H + +8e - →NH3+3H2O E 0 = -0.12V / SHE

[0113] All of the above reactions are multi-electron transfer processes. Several factors, such as electrode materials or crystal planes, can be modified or adjusted to determine the final product of the electrochemical reduction of nitrates. For example, various embodiments may use catalysts and / or electrode materials or other conditions selected to produce molecular nitrogen as the reaction product.

[0114] In some embodiments, the electrochemical reduction of nitrogen may involve the use of monometallic catalysts of noble metals (e.g., Ru, Rh, Pd, Ag, Pt, Au, etc.) and / or first-row transition metal systems. For example, several first-row transition metal systems that can be used in various embodiments exhibit high catalyst selectivity, effective removal, and low cost for the electrochemical reduction of nitrates, and include, among others, iron or copper metal foams, Cu nanosheets, Cu on 3,4,5,9-perylenetetracarboxylic anhydride, and cobalt nanoarrays. In some embodiments, two-component metal catalyst systems such as Pt and Pd-based catalysts modified by introducing modified metals (Sn, Cu, Bi, Ge) to the electrode surface can be used, which can result in higher nitrate reduction activity. Other bimetallic catalysts that can be used in various embodiments include Cu / Fe systems and Pt on carbon. 78 Ru 22 Cu 50 Ni 50 Examples include: electrochemical reduction of nitrates, NiO porous nanoplates on Co3O4, nanotube heterostructures of Co / CoO nanosheet arrays having Schottky interfaces on nickel foam, Cu / Cu2O nanowire arrays, and TiO 2-x This may include the use of a metal oxide catalyst such as TiO2.

[0115] In some embodiments, electrochemistry can be carried out as a pretreatment to reduce nitrates using an iron cathode. For example, in various embodiments, the electrode is used under a constant reduction bias to reduce Fe which may dissolve and cause corrosion of the electrode. 2+ or Fe 3+ The formation of nitrates can be restricted. The solution may be adjusted, for example, by adding a base to limit the dissolution of iron that may occur under acidic conditions, or it may be maintained within the basic range, for example, above about 10, or within the pH range of about 10 to about 12. A voltage in the range of -1.0V to -1.5V relative to Ag / AgCl can be applied to the iron electrode. Higher voltages may be used, but this may reduce the selectivity of nitrate reduction due to increased reduction of water. Electrolysis should be continued until the desired nitrate concentration is reached.

[0116] In some embodiments, electrochemistry can be carried out as a pretreatment to reduce nitrates using a copper cathode. For example, in various embodiments, the electrode is used under a constant reduction bias to reduce Cu, which may dissolve and cause corrosion of the electrode. + or Cu 2+ The formation of nitrite can be limited. The solution may be modified or maintained to a pH range of, for example, about 2 to about 12. In some embodiments, ammonia is the main product of nitrate reduction under acidic conditions, and ammonia does not interfere with ARP, so the pH may be modified by adding an acid, or maintained within an acidic range such as less than about 4, or about 2 to about 4. Under basic conditions, nitrite is the main product of nitrate reduction, and nitrite may interfere 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 may cause the formation of nitrite instead of ammonia and can be avoided. Electrolysis should be continued until the desired nitrate concentration is reached.

[0117] In some embodiments, electrochemistry can be carried out as a pretreatment to reduce nitrates using a copper:iron cathode. The electrode contains Cu, which can dissolve and cause corrosion of the electrode. + Cu 2+ Fe 2+ , or Fe 3+ The solution may be under a certain reduction bias to limit the formation of nitrates. The solution may be modified by adding a base or otherwise to limit the dissolution of iron that may occur under acidic conditions, or it may be maintained in a basic pH range, for example, above about 10, or between about 10 and 12. A voltage in the range of -1.3V to -1.4V can be applied to the Cu:Fe cathode relative to Ag / AgCl. This is sufficient to effectively reduce nitrates and nitrites to nitrogen gas while limiting competition with the reduction of water. Electrolysis should be continued until the desired nitrate concentration is reached.

[0118] Electrochemical systems can be used before or simultaneously with UV irradiation. Figure 2 shows examples of electrochemical systems that may be used in various embodiments described herein, including before UV irradiation, during various pretreatment processes. The vessels in which the anode and cathode are located may also be called the anode compartment and cathode compartment, respectively. A system like the one shown may be used, for example, in pretreatment for the reduction of nitrates as described above. The system may also be used in posttreatment steps for the recovery of valuable reagents, such as sensitizers. The illustrated electrolytic cell is an electrochemical device that uses an external power source to supply electrical energy and drives a chemical reaction 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 may be a solvent containing dissolved salts. For example, in many embodiments, the solvent is water, and the salts are inorganic salts 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 may be excluded from use as electrolytes. In the various embodiments, including aqueous solutions, the concentration of the electrolyte may be about 0.01 M to 1.0 M, or at least about 0.1 M, for example, about 0.1 M to about 1.0 M, in order to allow charge transfer.

[0119] In the exemplary electrolytic cell shown in Figure 2, the system includes two electrodes, a power supply, 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 performs several important functions, including maintaining electrical neutrality, stabilizing the junction potential, and minimizing cross-contamination. A typical membrane used in this device is a cation exchange membrane. Examples of cation exchange membranes that may be used include, but are not limited to, perfluorinated or partially fluorinated polymers such as Nafion. In alternative embodiments, the electrodes may be in the same compartment. Although not shown, in various embodiments, the electrolyte may be stirred in both chambers by a mechanical stirrer or a magnetic stirrer, such as a magnetic stirrer containing magnets in a chamber on which the cell is placed. In this electrolytic cell configuration, the reaction products formed at each electrode are separated. This is useful because, in some cases, some of the products may interfere with the desired reaction. Figure 2 shows a single electrode in the anode and cathode compartments, but multiple electrodes can be placed in these compartments. These electrodes may be of the same or different materials.

[0120] Figure 3 shows 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 nitrate / nitrite reduction electrolytic cell with two separated electrodes. The nitrate / nitrite solution and another electrolyte are separated by a cation exchange membrane. Both solutions are purged with an inert gas such as argon. The cathode is placed in the nitrate / nitrite solution and the anode is placed in the other electrolyte. A voltage is applied between the cathode and the anode to reduce the nitrate / nitrite to N2 at the cathode and induce a sacrificial oxidation reaction 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 can be added to lower the voltage requirement of the cell.

[0121] In some examples, 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, thereby removing these impurities from wastewater while simultaneously photolysis of pre-purified water. For example, the system may include a first chamber where pretreatment takes place and a second chamber where photolysis takes place. 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. Then, the pretreatment chamber can be replenished with wastewater, such as PFAS-contaminated water, for pretreatment. In this way, pretreatment and photolysis can be carried out simultaneously in separate chambers.

[0122] In some embodiments, the post-electrolysis solution may pass through a cation exchange resin before the ARP. In this way, any cations present in the solution due to the dissolution of the nitrate reducing cathode that are detrimental to the ARP can be exchanged for Na or K that are not detrimental to the ARP.

[0123] <Pre-filtration treatment> Various embodiments may include pretreatment filtration of wastewater. For example, Figure 4 is a schematic diagram showing potential pathways for implementing membrane-based separation techniques such as reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration, forward osmosis, and / or electrodialysis before photoreduction to improve water throughput and defluorination performance. In some embodiments, the process begins with concentrating PFAS in contaminated wastewater by pretreatment filtration using one or more membrane systems, such as RO, NF, and / or UF. The membrane rejection solution, also called the concentrate, contains substances that do not pass through the membrane, such as large PFAS molecules whose molecular weight exceeds half of the molecular weight cutoff (MWCO). As a result, the concentration of PFAS increases in the membrane rejection solution, while the water that passes through the membrane contains no PFAS compounds or only trace amounts of PFAS compounds. After filtration of the wastewater, the membrane rejection solution can be filtered one or more times by passing the membrane rejection solution through the same and / or different membrane systems again. A membrane rejection solution containing PFAS at a higher concentration than the initial concentration can then be subjected to photoreduction. After photoreduction, the solution can be optionally filtered again through one or more membrane systems to remove residual PFAS compounds from the effluent. The subsequent filtration process also helps to recover chemicals used in the destruction process (e.g., recirculating the concentrated rejection to a photoreactor). This filtration process can be used in any of the various PFAS destruction systems and methods described herein. Furthermore, PFAS can be selectively concentrated and isolated from background components using other types of filtration media or membranes. For example, PFAS can be selectively isolated into the rejection solution using membranes with alternative pore sizes, such as macro or nano-sized pores, while allowing anions such as nitrates, chlorides, or sulfates to pass through the membrane into the permeate.

[0124] <Organic material pretreatment> Other contaminants that may inhibit the UV-ARP process are those that obstruct the transmission of UV light into the water stream. These include, but are not limited to, organic substances such as humic acid, particulate matter / suspended solids, and UV-absorbing non-metallic substances such as iron. These contaminants can also be reduced in concentration or removed by pretreatment according to various embodiments.

[0125] Multiple techniques can be used to remove UV-inhibiting substances. Techniques for removing solids include, but are not limited to, flocculation, solidification, clarification, filtration, centrifugation, and sedimentation. For the removal of organic components, pretreatments such as photochemical oxidation, chemical oxidation, ozonolysis, or electrochemical oxidation processes, but are not limited to these, can be used. Furthermore, biological or hydrothermal treatments can be used in various embodiments. Possible oxidizing species include, but are not limited to, ozone, hydrogen peroxide, persulfates, and permanganates.

[0126] <Reagent pretreatment> In various embodiments, the pretreatment method may include adding reagents used in UV-ARP that yield byproducts that do not interfere with the UV-ARP reaction. For example, sulfites can be added as a pretreatment agent to reduce or eliminate oxyhalide contaminants. The byproducts of this reaction are halides and sulfate ions that have minimal effect on UV-ARP.

[0127] <Metal complex pretreatment> Another class of solvated electron scavengers that can be removed by pretreatment in various embodiments are metal ions or metal complexes. Heavy metals, including zinc, mercury, nickel, chromium, and arsenic, have been found to be increasing in levels in wastewater, and these raise concerns for human health. The increased presence of these species is a result of industrial activities (e.g., plating, 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 absorbents, membrane treatment, chemical treatment, electrotherapy, and photocatalytic treatment. The absorption treatment may include carbon-based absorbents, one or more of activated carbon, carbon nanotubes, and graphene, and in some embodiments, other chemical species may be grafted into the carbon treatment. Other absorbents that can be used in various embodiments include chitosan, various minerals such as mica, clay and zeolites, magnetic adsorbents in which magnetic nanoparticles are bound to the absorbent species, and metal-organic skeletal materials. For example, the treatment solution can be passed through a column or bed to remove scavengers. Alternatively, reagents can be added to the treatment solution to induce precipitation, coagulation, or aggregation. This can be followed by sedimentation, and then the clear solution can be removed by decantation or siphon. In other alternative methods, the solid can be removed by passing the solution through a filter. Membranes are also used to reduce metal contamination in various embodiments. Membrane treatment methods may include ultrafiltration, nanofiltration, microfiltration, reverse osmosis, forward osmosis, and electrodialysis, as described above with respect to pre-filtration treatment. Other embodiments may include removing metals from water by chemical separation methods such as precipitation, coagulation, and / or aggregation. Various electrochemical treatments that can be used in some embodiments to remove metal species include electrochemical oxidation-reduction and electrocoagulation. Furthermore, ion exchange treatment can be considered a form of electro-based separation and is an effective means of removing metal ions in some embodiments.

[0128] In some embodiments, cation exchange can be used to eliminate or reduce the concentration of one or more metal contaminants. For example, a cation exchange membrane can be deployed to capture multiple cationic transition metal species (e.g., Fe) that can solvate electrons. 2+ Fe 3+ Mn 3+ Cu 2+ +, Cu 1+ Pb 2+ , Cd 2+ The concentration of ) can be reduced simultaneously. The cation exchange membrane can also precipitate as Mg(OH)2 and Ca(OH)2, respectively, upon addition of a base. 2+ and Ca 2+ The concentration of alkali metal cations such as can be reduced or substantially removed. The inclusion of bases can be used to achieve high pH conditions for highly reducing processes, as will be discussed further below. However, fine precipitates of Mg(OH)2 and / or Ca(OH)2 may result in light scattering, potentially reducing the number of photons available for absorption by the sensitizer. As a result, energy consumption may be higher and / or reaction times may be longer. Therefore, Mg 2+ and Ca 2+ A pretreatment method that promotes the removal of [unclear material] may be desirable.

[0129] <Solid> Depending on the source of the waste flow, some embodiments may include a sedimentation step, which may be performed before and / or after other pretreatments, such as before and / or after oxidation pretreatment. This optional sedimentation step may be used to settle solids, such as soil particles, from the liquid and improve UV transmission. For example, pretreatment of waste flows including landfill leachate and natural water sources may include a sedimentation step, which may include letting the waste flow stand for at least 1 hour, e.g., about 1 hour to 1 day, or about 6 hours to about 18 hours, or about 10 to about 14 hours, or about 12 hours. If a sedimentation step is present, the time required for the sedimentation step may depend on the source of the waste flow and the level of solids present. Once completed, the liquid components can be removed from the settled solid components and then further treated by pretreatment and UV photoreduction to break down the PFAS.

[0130] <Oxidative pretreatment> In some embodiments, an oxidative pretreatment process can be used to treat PFAS containing a target fluorotelomer species. In some embodiments, partial degradation of long-chain telomers can be carried out by an oxidative process.

[0131] Oxidative pretreatment can be used, for example, to treat fluorotelomer species contained in aqueous film-forming foam (AFFF) products. Oxidative pretreatment and other chemical treatments are also beneficial for PFAS concentrate sources, such as PFAS in wastewater and concentrates produced by foam fractionation processes. Foam fractionation occurs when a gas (e.g., air or nitrogen) is bubbling into water containing PFAS. The PFAS adheres to the bubbles and is transported to a surface that can capture the foam. In some cases, additional surfactants are added to facilitate the process.

[0132] The pretreatment can utilize one or more techniques that can be applied in combination, simultaneously, and / or sequentially, according to several embodiments. For example, oxidation treatment can be used to reduce or eliminate several organic species, such as humic acid and / or fulvic acid. Humic acid and fulvic acid absorb the UV spectrum, and their presence can reduce the number of photons absorbed by the sensitizer. As described above, a cation exchange medium can be used to eliminate or reduce the concentration of one or more metal contaminants. In various embodiments, the pretreatment method may involve Mg 2+ and Ca 2+ This may include the removal of [something].

[0133] One example of sequential pretreatment is to perform oxidative pretreatment, followed by passing the solution through an ion exchange membrane, and then a nanofiltration step. However, Mg 2+ and / or Ca 2+ In some embodiments, such as when the objective is to remove Mg, oxidative pretreatment can be omitted. For example, an ion exchange membrane can be used, and subsequent nanofiltration can be omitted. Alternatively, a base such as NaOH / KOH can be added to raise the pH, and Mg 2+ and / or Ca 2+ The material can be removed to induce sedimentation, and then separated via a sedimentation tank or other method.

[0134] In some embodiments, the oxidative pretreatment processes disclosed herein can be used to treat targeted fluorotelomer species, such as fluorotelomer species contained in aqueous film-forming foam (AFFF) products. The thermal and ozone oxidative pretreatment processes described herein can also be used to treat waste streams generated by foam fractionation processes. Foam fractionation occurs when a gas (e.g., air or nitrogen) is bubbling into water containing PFAS. The PFAS adheres to the bubbles and is carried to a surface that can capture the foam. In some cases, the foam fraction may include additional surfactants added to facilitate the process.

[0135] Depending on the source of the waste flow, some embodiments may include a step of settling the waste flow before and / or after the oxidation pretreatment, as described above.

[0136] In addition to solid particles that may be present in the waste stream, other substances present in the waste stream may also reduce the chemical processes of UV transmission or photoreduction. Therefore, pretreatment of the waste stream is useful to improve UV transmission, but it is important not to introduce any substances that interfere with the UV photoreduction process. Various embodiments disclosed herein for oxidative pretreatment can pretreatment the waste stream not only to improve UV transmission but also without interfering with the UV photoreduction reaction. In some embodiments disclosed herein, such as the embodiments for oxidative pretreatment, subsequent UV photoreduction can be improved without improving UV transmission. For example, pretreatment may not result in improved UV transmission but may still result in improved photodegradation, which may be due to other means, such as pretreatment products that interact with the reagents used for photodegradation.

[0137] Pretreatment methods that can be used in various embodiments include oxidation of the waste flow. For example, the waste flow may be pretreated using thermal oxidation. In other embodiments, it may be pretreated using ozone oxidation.

[0138] Embodiments involving thermal oxidation may include combining the waste flow with chemical additives to adjust the pH. The chemical additives may include persulfates and acids or bases to adjust the pH.

[0139] In some embodiments, the persulfate may be, for example, potassium persulfate, sodium persulfate, and / or aluminum persulfate. The amount of persulfate used may be adjusted as needed to achieve the desired concentration in the final treatment solution. For example, the concentration of the persulfate 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 in the final solution.

[0140] 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 the desired pH. For example, if the thermal oxidation is carried out under basic 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. If the thermal oxidation is carried out 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.

[0141] Thermal oxidation can be carried out in a container in which wastewater is treated at high temperature and pressure. Examples of containers that can be used include, for example, an autoclave. In some embodiments, the thermal oxidation process may be carried out in the same container as the UV treatment, such as in a sequential batch mode. In other embodiments, the oxidation process may be carried out in a separate treatment container prior to the UV treatment in the UV light treatment container.

[0142] In some embodiments, the thermal oxidation pretreatment can be carried out at elevated temperatures. For example, the wastewater and added chemicals may be heated to temperatures of about 80 to about 160°C, or about 100 to about 140°C, or about 115 to about 125°C, or about 120°C, but other temperatures may be used.

[0143] In some embodiments, thermal oxidation can be carried out at increased pressure along with increased temperature. For example, the wastewater and added chemicals may 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, for example, about 2 bar.

[0144] Embodiments involving ozone oxidation may include combining the waste stream with a base such as sodium hydroxide, potassium hydroxide, and / or calcium hydroxide. The amount of base used may be adjusted as needed to raise the pH to a desired level, for example, about 10 to about 14, or about 11.5 to about 12.5, or about 11.8 to about 12.3, or about 12.

[0145] Next, wastewater containing bases can be treated by ozone oxidation. For example, wastewater can be treated with an ozone generator, such as a portable ozone generator like the MultiPurpose Ozone Machine available from Shenzhen VANSU Technology Co. in China. The treatment may be carried out at a rate of approximately 500 mg / h O3 to approximately 2000 mg / h O3, for example, 800 mg / h O3 to approximately 1000 mg / h O3, or approximately 1000 mg / h O3. The treatment period may be approximately 3 to approximately 9 hours, for example, approximately 7 to approximately 10 hours or approximately 6 hours. The duration of the treatment may depend on the rate of ozone generation and exposure.

[0146] Pretreatment by thermal oxidation or ozone oxidation, and optionally by a sedimentation process, can result in a substantial improvement in UV transmission. For example, UV transmission can increase from 0% to about 10-20%, or to about 25-45%.

[0147] Furthermore, pretreatment by thermal oxidation or ozone oxidation, and optionally by a sedimentation step, can result in a substantial improvement in UV transmission without separating PFAS from the liquid. This is an improvement over some pretreatment methods that remove some of the PFAS while simultaneously removing substances that, by removing them, improve UV transmission. This separation of PFAS necessitates treating two PFAS streams, substantially increasing the complexity and cost of the treatment. In contrast, the oxidative pretreatment methods disclosed herein can improve UV transmission and promote PFAS breakdown without removing PFAS from the wastewater, thereby maintaining a single waste stream for subsequent treatment.

[0148] Following pretreatment according to the embodiments described herein, wastewater can be treated using UV photoreduction. However, in some cases, it may be preferable to dilute the waste stream before UV photoreduction. For example, the waste stream may be diluted about 1.5 to about 10 times, for example, about 2 to about 5 times, or about 2 to about 3 times. The amount of dilution may depend on the source and properties of the waste stream. However, less dilution is required for the improved UV transmission (without interference to UV photoreduction) brought about by various embodiments. This results in a much more efficient process, as the treatment volume does not increase substantially compared to some other methods.

[0149] Following pretreatment and optional dilution, the waste stream may be treated using a photoreactor for UV photoreduction, for example, to break down the PFAS. Various embodiments use a photoreactor that includes a light source that delivers a narrow range of ultraviolet radiation with a peak at about 222 nm, such as a krypton / chloride excimer lamp.

[0150] Photoreduction methods are based on the generation of potent reducing species, generally solvated electrons, by irradiation with a photosensitizer. The oxidative pretreatment of wastewater described herein enhances the efficiency of photochemical breakdown of PFAS and makes the photochemical method more commonly usable in various PFAS-containing waste streams.

[0151] In some embodiments, the UV photoreduction process can be carried out using one or more reaction vessels having one or more UV light sources, as will be further described below. The reactor is fed pretreatment wastewater containing PFAS, water, and a sensitizer that can absorb UV light to generate reactive species. Furthermore, one or more other chemical additives may be optionally present to facilitate the reaction.

[0152] Figure 5 shows an example of a PFAS treatment method that can be used in various embodiments. This method optionally begins with settling the wastewater 10, followed by decantation or other removal of the liquid from the settled wastewater 20. For example, as an alternative to decantation, the purified water can be pumped from the top above the solid, the solid can be pumped from the bottom below the purified water or drained, or other separation methods can be used. Next, optionally the decanted (or otherwise separated) wastewater is pretreated 30 by oxidative pretreatment, etc. The pretreated wastewater is then optionally diluted 40, and the pretreated and optionally diluted wastewater is then photoreduction 50 by UV treatment at 222 nm and / or 254 nm, etc.

[0153] Figure 6 shows a diagram of the thermal oxidation and photoreduction method. This method optionally begins with settling the wastewater 110, followed by decantation or other removal of the liquid from the settled wastewater 120. The decanted (or otherwise separated) liquid wastewater is then optionally mixed with a persulfate and an acid or base 130. The wastewater is then pretreated by thermal oxidation 140 by exposure to increased temperature and increased pressure for a sufficient time to complete the reaction. The pretreated wastewater may then optionally be diluted 150 and mixed with a photosensitizer 160. Alternatively, steps 150 and 160 may be in reverse order or performed simultaneously. The wastewater is then subjected to photoreduction 170, such as UV treatment at 222 nm and / or 254 nm.

[0154] Figure 7 shows a diagram of the ozono-oxidation and photoreduction method. This method optionally begins with settling the wastewater 210, followed by decantation or other removal of the liquid from the settled wastewater 220. Next, optionally, the decanted liquid wastewater is mixed with a base 230. The wastewater is optionally settled 240 and then subjected to ozono-oxidation 250 for a sufficient time to complete the pretreatment reaction. Next, the pretreated wastewater may optionally be diluted 260 and mixed with a photosensitizer 270. Alternatively, steps 260 and 270 may be in reverse order or performed simultaneously. The wastewater is then subjected to photoreduction 280, such as UV treatment at 222 nm and / or 254 nm.

[0155] The methods shown in Figures 5 to 7 may optionally include additional sedimentation and / or decantation steps (or other separation steps), or the sedimentation and / or decantation steps (or other separation steps) may be performed at other points in time. For example, the method in Figure 6 may include an optional sedimentation and decantation step (or other separation step) after mixing the wastewater with persulfate and acid or base 130, followed by decanting (or removing by other means) the separated liquid, and then applying thermal oxidation to the decanted liquid 140. As another example, the method in Figure 7 may include decanting (or removal of other forms of the separated liquid) after the step of sedimentation of the wastewater 240 and before the step of applying ozone oxidation 250.

[0156] In exemplary embodiments, the wastewater stream containing PFAS is allowed to settle for a suitable period, e.g., about 6 to about 18 hours, to allow solid sedimentation. The liquid is decanted or otherwise separated from the solid and combined with persulfate and acid or base. The resulting wastewater contains persulfate at a concentration of about 150 mM and has a pH of about 11 to about 13 or about 12. The wastewater is then treated at a high temperature, such as about 100 to about 140°C or about 100°C, and 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, for a sufficient time to complete the reaction, e.g., about 1 to about 3 hours or about 2 hours. Following the pretreatment, the wastewater is combined with a photosensitizer containing sulfite and halide salts, as well as a base. The resulting wastewater contains approximately 40–60 mM sulfites and approximately 7–13 mM halide salts, with a pH of approximately 13–15. Alternatively, the resulting wastewater contains approximately 5–15 mM sulfites and approximately 1–4 mM halide salts, with a pH of approximately 12. The wastewater may then be optionally diluted by approximately 2–5 times or approximately 2–3 times. The wastewater is then treated by UV photoreduction at 222 nm and / or 254 nm for the time required to complete the reaction, e.g., approximately 1 hour–24 hours, or approximately 2 hours–12 hours, or approximately 4 hours–8 hours. After completion of photoreduction, a large portion of the PFAS, e.g., approximately 70%–90%, or approximately 80%, may be destroyed. For example, after approximately 8 hours of photoreduction, approximately 80% of the PFAS may be destroyed compared to the original level of PFAS in the wastewater.

[0157] In some embodiments, in addition to what is disclosed above, additional pretreatment can also be used. For example, pretreatment for removing nitrates, nitrites or other contaminants can be achieved by several methods including chemical reduction, ion exchange membranes, electrodialysis, electrochemical reduction, photochemical reduction, and bioremediation where contaminants are decomposed by organisms. Also, for removing UV inhibitors, techniques such as flocculation, coagulation, clarification, filtration, centrifugation, and sedimentation can be used. For removing organic components, treatments such as chemical oxidation such as photochemical or electrochemical oxidation processes, and other chemical or ozone decomposition methods can be utilized. Further, biological or hydrothermal treatments can be utilized. Other oxidizing species that can be used include permanganate species. The oxidative pretreatment systems and methods described herein can be used in combination with any of these processes.

[0158] A system for the UV destruction of PFAS can consist of a single reaction vessel in which oxidative pretreatment, optional additional pretreatment such as sedimentation, UV photoreduction, and other steps are carried out sequentially. Alternatively, for example, to maximize the efficiency of the process, the above processes can be carried out in a single vessel or separate vessels or chambers.

[0159] <Photolysis step>

[0160] <UV reactor> In some embodiments, a system for the UV destruction of PFAS can include a single reaction vessel in which pretreatment, photolysis, and post-treatment steps are carried out sequentially. In other embodiments, one or more or all of the pretreatment, photolysis, and post-treatment steps can be carried out in separate vessels or chambers, for example, for a continuous process.

[0161] In some embodiments, the UV photoreduction process can be carried out using one or more reaction vessels having one or more UV light sources. The reactor is charged with pretreated wastewater containing PFAS, water, and a sensitizer that can absorb UV light and generate reactive species. Additionally, optionally, one or more other chemical additives may be present to facilitate the reaction.

[0162] The reaction vessel may include one or more UV light sources that emit light such as 222 nm UV light or 254 nm UV light. In some embodiments, the light source or sources can emit multiple wavelengths, and in addition to 222 nm and 254 nm, light of other wavelengths such as 185 nm can contribute to the PFAS photoreduction.

[0163] The photoreactor can be used alone or in combination with other reactors, such as in a series configuration, which can also use photoreduction at the same or different wavelengths, or other PFAS destruction methods. Alternatively, one or more steps may be carried out within the same vessel.

[0164] Examples of PFAS capture systems, processing systems, and preprocessing are provided in other applications of the applicant, U.S. Patent Application No. 18 / 212,603, filed June 21, 2023, entitled "METHOD AND APPARATUS FOR THE DESTRUCTION AND DEFLUORINATION OF PER-AND POLYFLUOROALKYL SUBSTANCES (PFAS), FLUOROTELOMERS AND OTHER PERSISITENT ORGANIC POLLUTANTS," U.S. Patent Application No. 63 / 513,782, filed July 14, 2023, entitled "PROCESSES FOR EFFICIENT PHOTOCHEMICAL DESTRUCTION OF PFAS FROM WASTE STREAMS," and Sorbents and Methods for the Capture and Deflurry of Per-and Polyfluoroalkyl Substances (PFAS), Fluorotelomeres and Other Persistent Organic Pollutants (PFAS), FROM WASTE STREAMS (PFAS), U.S. Patent Application No. 63 / 513,782, filed July 14, 2023, and October 12, 2023, entitled "SORBENTS AND METHODS FOR THE CAPTURE AND DEFLUORINATION OF PER-AND POLY FLUOROALKYL These are described in U.S. Patent Application No. 18 / 555,135 (National Phase Entry) entitled SUBSTANCES (PFAS), all of which are incorporated herein by reference. The systems and methods described herein may be used in combination with the methods and systems described in those applications.

[0165] An example of a photoreactor that can be used in various embodiments includes one or more lamps, such as cylindrical bulbs or lamps including other bulb shapes, and one or more photoreactor vessels are configured so that the light from the lamps is projected onto the contents of one or more reaction vessels. The lamps may be supported on a frame, such as a metal support frame, at a desired distance above the top surface of the photoreactor vessel and / or above the top surface of the liquid inside the photoreactor vessel, in order to directly illuminate the surface of the reaction solution when in use, or to illuminate through the walls of the reaction vessel. Alternatively, the lamps may be fitted inside the reaction vessel to directly irradiate the contents from inside the reaction vessel. The bulbs may be protected and / or separated from the reaction solution inside the reaction vessel by a sleeve or other barrier, etc. In some embodiments, the photoreactor vessel may include two cylindrical lamps and a support frame that holds the two lamps horizontally at a selected distance above the level surface of the photoreactor vessel. Other lights and the configuration and orientation of the reaction vessel can be used to optimize energy delivery and PFAS breakdown.

[0166] The photoreactor vessel may be made of any suitable material, such as quartz or other non-reactive and transparent to 222 nm radiation. In other embodiments, such as those in which a light bulb is placed inside the reaction vessel, the reaction vessel does not need to be transparent and may be made of an opaque and non-reactive material, such as stainless steel. The vessel may be configured to contain a fluid and may include a top that can seal the vessel. In some embodiments, the photoreactor may include a single reaction vessel, and in other embodiments, it may include two or more reaction vessels, such as two or three or more reaction vessels. The reaction vessel may be of any size or shape. In some embodiments, the reaction vessel is cylindrical.

[0167] One or more lamps, lamp supports, and reaction vessels may be housed in a housing such as a metal enclosure or other enclosure.

[0168] An example of a lamp that can be used in various embodiments is a krypton / chloride excimer lamp that emits radiation at 222 nm. Other excimer lamps that emit narrowband radiation at other wavelengths can be used as alternatives. The lamp may consume 100 watts of power, or more or less. The power supply to the lamp may be 20 kilovolts, or greater or less. In some embodiments, the lamp power of lamps including those that emit light at 222 nm and 254 nm may be about 50 to about 5000 W, for example, about 100 to about 1000 W or about 100 to about 300 W. A single lamp may be used, or multiple lamps, which may be the same or different, may be used.

[0169] The photoreaction methods described herein can be carried out at room temperature or above room temperature. For example, in some embodiments, the temperature of the photoreactor may be about 55 to about 60°C during the reaction. However, higher or lower temperatures may be used instead. Furthermore, heating and / or cooling elements such as air ducts, fans and lamps may be added to the reactor and / or the room containing the reactor to raise or lower the temperature.

[0170] The reactor solution may remain still during UV treatment or may be stirred. For example, the reactor may include a stirrer or agitator capable of stirring or mixing the solution. In some embodiments, stirring or mixing the reactor solution during irradiation can facilitate exposure of the PFAS compound to areas with higher radiation. Alternatively, the solution may be recirculated through a heat exchange unit.

[0171] Ultimately, optimizing the reactor solution for increased efficiency may also rely on directly stirring or agitating the compounds to expose more solution components to a greater area of ​​radiation in a shorter time.

[0172] In some embodiments, PFAS irradiation at 222 nm and / or 254 nm may be carried out in a reaction solution containing only an aqueous solution of PFAS. However, the results may be improved by including a suitable reducing solution of appropriate concentration. This may result in a faster, more efficient, and more complete destruction of the PFAS.

[0173] Photoreduction of PFAS can destroy PFAS through mineralization, which involves converting the carbon-fluorine bond to 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 PFAS to fluoride ions F-.

[0174] Some embodiments result in near-complete destruction of the PFAS, such as complete destruction or destruction of more than 99%. Some embodiments result in destruction of at least 90% or at least 95% of the PFAS, for example, about 90% to about 100% or about 95% to about 100% of the PFAS.

[0175] The duration of the process required to achieve complete or near-complete destruction of PFAS may depend on the design of the photoreactor used, as well as other variables.

[0176] Various embodiments include a UV reactor for the photochemical breakdown 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 recirculation system which may have a heat exchange system configured to control the solution temperature. The UV reactor may further include a sensor module configured to allow continuous monitoring of 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.

[0177] As an example of a UV reactor according to various embodiments, a reactor configured to supply UV light exceeding 1000 Ws and maintain the solution below 50 °C can be mentioned. The UV reactor can include a sensor module configured to provide information useful for maintaining optimal photochemical conditions via a closed-loop control system for automatically maintaining the conditions. In some embodiments, one or more sensor systems are configured to monitor one or more of temperature, pressure, pH, UV intensity, fluoride ion concentration, and redox potential.

[0178] Additives filled from the port can be added continuously or in one or more batches. Typical additives include, but are not limited to, bases such as sulfites, initiators, sodium hydroxide or sodium carbonate.

[0179] Depending on the waste stream, it may be useful to perform both oxidation and reduction treatments. These two treatments can be carried out sequentially in the same container, or can be carried out in separate containers. The order in which these steps are carried out may vary depending on the components in the waste stream.

[0180] An example of a UV reactor as the photochemical part of the treatment system is shown in Figure A. The UV reactor in Figure 8 can be operated in batch mode or continuous mode. One embodiment of this design is a continuous stirred tank reactor.

[0181] <Sensitizer> Various embodiments include a sensitizer added to the wastewater. The photoreduction method is based on the generation of strong reducing species such as solvated electrons generated by irradiation of the photosensitizer.

[0182] In UV-ARP, the sensitizer absorbs UV photons, and as a result, an oxidized sensitizer and solvated electrons are generated as shown below. a. Sensitizer + hn (UV photon) → Sensitizer + + e aq - (Solvated electron)

[0183] Examples of photosensitizers that can be used in various embodiments include halides, pseudohalogens, inorganic oxoanions, anionic metal complexes, metal clusters, Zintol phase compounds, transition metal nanoparticles, organic anions, nitrogen heterocycles, boron-doped nanodiamonds, and / or nitrotriacetic acid. These sensitizers can be used in combination with or separately from different light sources.

[0184] Examples of halides that may be used include iodides, chlorides, and bromides. Examples of pseudohalogens that may be used include cyanides, isocyanates, cyanates, isocyanides, azides, hydroxides, hydrosulfides, hydroselenides, hydrotellides, fulminates, thiocyanates, selenocyanates, telluricyanates, isothiocyanates, nitroxides, tetracarbonylcorbaltates, trinitromethanides, tricyanomethanides, 1,2,3,4-thiatriazole-5-thiolates, fulminates, siafides, and aurids. Examples of inorganic oxoanions that may be used include sulfurous acid (SO3). 2- ), sulfuric acid (SO4 2- ), hyposulfurous acid (SO2 2- ), thiosulfate (S2O3 2- ), carbon dioxide (CO3 2- ), phosphoric acid (PO4 3- ), phosphorous acid (PO3 3- ), hypophosphorous acid (PO2 -3 ), and borate (BO3 3- ) are examples, and the protonation forms of these anions (e.g., HSO3) - HSO4 - , HCO3 - ) is included. Examples of anionic metal complexes that can be used include ferricyanide ions, ferrioxalate ions, tetrachloroplatinate ions, hexachloroiridiate ions, cyanocopper salts, and cerium(III) complexes. An example of a metal cluster that can be used is Mo6Cl 14 2 -, Zr6CCl 12 Ta6Cl 18 4- Re3Cl 123- Examples include iron-sulfur clusters. An example of a sintol phase compound that can be used is [Bi3] 3- [Sn9] 4- Examples of transition metal nanoparticles that can be used include gold, copper, and iron. Examples of organic anions that can be used include ascorbate anion, ascorbate dianion, phenolates, cresolates, dihydroxybenzene anion, methoxyphenolate, and thiophenolates. An example of a nitrogen heterocycle that can be used is indole-3-acetic acid.

[0185] Other components that may be included in the reactor include photosensitizers such as halide salts, either alone or in combination with other components such as sulfites. The concentration of the sensitizer depends on the electron absorption of the sensitizer spectrum, the spectral output of the lamp, and the concentrations of other sensitizers included in the reactor. The concentration of the halide salt may be about 1 mM to about 150 mM, or about 5 to about 15 mM, or about 7 mM to about 13 mM. For example, the concentration of KI may be about 1 mM to about 10 mM when 254 nm UV or 222 nm UV radiation is used in the photoreactor. The concentration of KBr may be about 10 mM to about 150 mM, for example when 22 nm UV radiation is used. The concentration of sulfite may be about 5 mM to about 100 mM, for example, about 25 mM to about 75 mM, or about 35 mM to about 65 mM, or about 45 mM to about 55 mM. For example, when 222 nm UV light is used in the reactor, the sulfite concentration may be about 5 mM. The pH may be, for example, greater than 10, greater than 12, or greater than 13. In some embodiments, the pH may be, for example, about 11 to about 15, or about 13 to about 15. In other embodiments where 185 nm UV light is used in the photoreactor, the concentration of the photosensitizer, which may include halide salts, sulfites, and sulfates, may be about 1 micromol to about 10 mM. For example, the concentration of NaCl may be about 150 micromoles, and the concentrations of sulfates and sulfites may be 1 mM. The pH range of the solution may be, for example, greater than about 7, greater than about 8, or greater than about 10.

[0186] Other components that may be included in the reactor include halide salts alone or in combination with other components such as sulfites. In some embodiments, such as those utilizing 222 nm UV light or 254 nm UV light, KI and Na2SO3 may be included in the reactor solution as 1 mM KI and 5 mM Na2SO3, although higher or lower concentrations, such as 10 mM KI and 50 mM Na2SO3, may be used. Other components that may be used in the reactor solution instead include KBr and Na2SO3, such as about 10 mM KBr and 50 mM Na2SO3 when 222 nm UV light is used, or about 150 mM KBr and 5 mM Na2SO3 when 222 nm UV light is used, although higher or lower concentrations may be used instead. In some embodiments utilizing either 222 nm UV light or 254 nm UV light, the photosensitizer contains 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 and about 10 mM KI at a pH of about 14. Further embodiments may comprise only a sulfite such as Na2SO3, such as about 50 mM Na2SO3, although higher or lower concentrations may be used instead.

[0187] In some embodiments, additional components, such as halide salts, can be used at lower concentrations, such as micromolar concentrations. These lower levels can be optimized and facilitated for efficient light absorption at 222 nm and 185 nm. For example, halide salts at micromolar concentrations can be used.

[0188] In some embodiments, it is preferable to maintain a high pH, ​​for example, 10 or higher, or 11 or higher, or 12 or higher, or 13 or higher, during photoreduction. Therefore, in addition to the above reagents, it may be useful to include a base such as sodium carbonate and / or one or more other bases such as hydroxides to increase the efficiency of the reaction.

[0189] In some embodiments, iodide (I -) can be used as a photosensitizer during photoreduction. As a result of absorption of UV photons, iodine radicals (I · ), iodine (I2), iodine radical anion (I2 - .) and triiodide anion (I3 - A variety of iodine-containing species, including but not limited to those listed above, are potentially generated. 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 these species increases, reducing the efficiency of the resulting PFAS breakdown.

[0190] Furthermore, in some cases, the water being treated may contain other substances that can interfere with the efficiency of the reaction. pH also plays a significant role in reaction efficiency. In some embodiments, the pH may be greater than 9 or about 10, for example, 12-14. Moreover, higher pH levels may increase the degree of mineralization of PFAS through their influence on the chemilysis mechanism. In some cases, chemicals may be added to alter the properties of the liquid being treated, which can result in significant costs and the generation of large amounts of waste.

[0191] Photosensitizers including, but not limited to, those described above may be further synthetically modified to induce PFAS selectivity in order to improve the kinetics and degree of PFAS mineralization in photochemical reactions. Means of conferring PFAS selectivity according to various embodiments, but not limited to, include the addition of fluorophilic, hydrophobic moieties or functional groups, or those that induce electrostatic interactions with the charged end groups of PFAS molecules. PFAS-selective synthetic modifications of photosensitizers may simultaneously encompass one or more of these moieties. These modified PFAS-selective photosensitizers may be further intercalated into mesoporous clay materials, including, but not limited to, montmorillonite, bentonite, or kaolinite. Thus, the capture of PFAS into the interlayer of mesoporous clay allows for the co-localization of PFAS molecules with the photosensitive active site in a local environment free from scavengers and co-contaminants.

[0192] The effectiveness of each of these sensitizers, and their selection for a particular embodiment, may depend on the wavelength of the light source.

[0193] <Light source> Low-pressure mercury lamps, medium-pressure mercury lamps, and mercury amalgam lamps are relatively inexpensive and highly efficient at converting electrical energy into UV photons, and thus can be used as UV radiation sources in various embodiments. Mercury lamps exhibit prominent spectral lines in the ultraviolet and visible light. For PFAS destruction, 184.5 nm (typically referred to as 185 nm) and 253.7 nm (typically referred to as 254 nm) are important wavelengths. However, in various embodiments, other light sources can also be used. In particular, various excimer lamps having high efficiency, high output, and narrow-band emission across 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 type of discharge lamp that contains a noble gas such as argon (Ar), krypton (Kr), or xenon (Xe), or a halogen dimer (F2, Cl2, Br2, or I2), or a combination of a halogen and a noble gas. The UV light from an excimer source is due to the emission from the excited states of noble gas dimers (Ar2 * , Kr2 * and Xe2 * ), halogen dimers (F2 * , Cl2 * Br2 * or I2 * ), and noble gas halide excimers (ArF * , ArCl * , ArBr * , ArI * , KrF * , KrCl * , KrBr * , KrI * , XeF * , XeCl * , XeBr * and XeI * ), where the asterisk indicates the excited state. Examples of excimer light sources and their principal emission outputs that can be used in various embodiments include XeXe * (172 nm), ArCl* (175nm), KrI * (190nm), ArF * (193nm), KrBr * (207nm), KrCl * (222nm), KrF * (248nm), XeI (253nm), Cl2 * (259nm), XeBr * , Br2 * (289nm) and XeCl * (308nm) is one example. Preferred lamps have an output between 190nm and 289nm. Strong KrCl * The wavelength output and availability of excimer lamps make them particularly desirable in certain embodiments. While the efficiency of excimer lamps may not be as high as that of mercury lamps, their ability to fine-tune the emission to suit a given sensitizer is useful for the overall effectiveness of photochemical processes in various embodiments. These lamps have the additional advantage of being mercury-free.

[0194] Other UV light sources that can be used in various embodiments include xenon arc lamps, deuterium arc lamps, mercury / xenon arc lamps, metal / halide arc lamps, and UV LEDs. The amount of light (power) from UV LEDs is generally much lower than that from mercury or other discharge lamps, and therefore multiple LEDs can be included in various embodiments to destroy PFAS, for example, over a time frame of several minutes to several hours.

[0195] The light sources included in various embodiments generate sufficient energy to solvate electrons from the sensitizer. The UV light generated by the light source and used in various embodiments may have a wavelength of about 190 nm to 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, such as an excimer lamp, e.g., a krypton / chloride excimer lamp, may be used. Ultraviolet light-emitting diodes can also be used as light sources.

[0196] Light sources, including but not limited to those listed above, may be used separately or in combination, sequentially or simultaneously, in a single reactor or a series of reactors.

[0197] <Photodecomposition at 222nm> The various embodiments described herein relate to systems and methods for the photochemical destruction of PFAS using 222 nm radiation with UV-ARP to generate potent reducing species, such as solvated electrons, produced by irradiation with a photosensitizer. This process and system enhances the efficiency of PFAS photochemical destruction, enables the more common use of photochemical methods in various PFAS-containing waste streams, and reduces the time and cost required for PFAS destruction.

[0198] In various embodiments, the photochemical system includes a reaction vessel equipped with one or more UV light sources emitting 222 nm light. The reactor is fed a liquid consisting of PFAS, water (and / or another solvent), and a sensitizer that can absorb UV light to generate reactive species. Optionally, one or more other chemical additives may be present to accelerate the reaction. The photoreactor may be used alone or in combination with other reactors, such as in a series configuration. These other reactors may also use UV-ARP at the same or different wavelengths, or use other PFAS decomposition methods. Furthermore, the photoreactor system may include one or more processes for pretreatment of PFAS-contaminated materials, such as wastewater or other water sources, as well as post-treatment and finishing processes.

[0199] Various embodiments utilize a photoreactor that includes a light source that delivers a narrow range of ultraviolet radiation with a peak at approximately 222 nm, such as a krypton / chloride excimer lamp.

[0200] The photoreactor vessel may be made of any suitable material, such as quartz or other non-reactive and transparent to 222 nm radiation. (If UV-ARP is performed using light of different wavelengths, the photoreactor vessel must, alternatively or additionally, be transparent to radiation of those wavelengths.) In other embodiments, such as those in which the light bulb is located inside the reaction vessel, the reaction vessel does not need to be transparent and may be made of an opaque and non-reactive material, such as stainless steel. The vessel may be configured to contain a fluid and may include a top that can seal the vessel. In some embodiments, the photoreactor may include a single reaction vessel, and in other embodiments, it may include two or more reaction vessels, such as two or three or more reaction vessels. The reaction vessel may be of any size or shape. In some embodiments, the reaction vessel is cylindrical. One or more lamps, lamp supports, and reaction vessels may be housed in a housing, such as a metal enclosure or other enclosure. The same design may be used for UV-ARP systems that deliver at other wavelengths.

[0201] An example of a lamp that can be used in various embodiments is a krypton / chloride excimer lamp that emits radiation at 222 nm. Other excimer lamps that emit narrowband radiation at other wavelengths can be used as alternatives. The lamp may consume 100 watts of power, or more or less. An excimer lamp system, which may include a bulb, wiring, and ballast (power supply), may have a total power conversion efficiency of 0.1% to about 20%, with the conversion efficiency decreasing as the lamp intensity increases. The power supplied to the lamp may be about 20 kilovolts in some embodiments supporting high-power lamps, for example, and about 3 kV in embodiments supporting lower-intensity lamps.

[0202] The photoreaction methods described herein can be carried out at room temperature or above room temperature. For example, in some embodiments, the temperature of the photoreactor may be about 55 to about 60°C during the reaction. However, higher or lower temperatures may be used instead. Furthermore, heating and / or cooling elements such as air ducts, fans and lamps may be added to the reactor and / or the room containing the reactor to raise or lower the temperature.

[0203] The reactor solution may remain still during UV treatment or may be stirred. For example, the reactor may include a stirrer or agitator capable of stirring or mixing the solution. In some embodiments, stirring or mixing the reactor solution during irradiation can facilitate exposure of the PFAS compound to areas with higher radiation. Alternatively, the solution may be recirculated through a heat exchange unit.

[0204] Ultimately, optimizing the reactor solution for increased efficiency may also rely on directly stirring or agitating the compounds to expose more solution components to a greater area of ​​radiation in a shorter time.

[0205] In some embodiments, PFAS irradiation at 222 nm may be carried out in a reaction solution containing only an aqueous solution of PFAS. However, the results may be improved by including a suitable reducing solution of appropriate concentration. This may result in a faster, more efficient, and more complete destruction of the PFAS.

[0206] Some embodiments result in near-complete destruction of the PFAS, such as complete destruction or destruction of more than 99%. Some embodiments result in destruction of at least 90% or at least 95% of the PFAS, for example, about 90% to about 100% or about 95% to about 100% of the PFAS.

[0207] The duration of processing required to achieve complete or near-complete destruction of PFAS may depend on the design of the photoreactor used, as well as other variables. However, in some embodiments, complete or near-complete (e.g., 99% or more) destruction of PFAS can be achieved after processing for approximately 5 minutes to 6 hours, for example, after processing for approximately 2 to 5 hours.

[0208] In some examples included herein, control samples without reagents were tested. Even in the absence of reagents, irradiation at 222 nm resulted in the destruction of PFAS via a direct photodegradation process. However, the PFAS destruction was much slower and less complete. In contrast, when reagents were included, PFAS destruction was faster and more complete. It is believed that the superior results obtained using the advanced reduction process described herein were due to the generation of solvated electrons that can react with the carbon-fluorine bond, rather than relying on the direct absorption of energy by PFAS and subsequent bond cleavage.

[0209] Furthermore, direct irradiation at 222 nm in the absence of reagents may result in some enhanced photodegradation of perfluoroalkyl carboxylic acids (PFCAs), fluorotelomers, unsaturated carboxylic acids, and GenX PFAS compounds compared to photodegradation at 254 nm, although 222 nm treatment alone exhibits minimal performance / efficiency for perfluoroalkyl sulfonic acids. In contrast, the use of the highly reducing process at 222 nm described herein results in the more rapid, complete, and overall more efficient destruction of both perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs).

[0210] <Combinations of photochemistry and electrochemistry> In some embodiments, UV photolysis can be used in combination with an electrochemical system. This may be used alone or in combination with other UV photolysis methods described herein, and the combination can further increase the breakdown rate of PFAS. An example of an electrolytic cell that can be used in combination with photochemistry is the photoelectrolytic cell shown in Figure 9, in which the cathode is immersed in an electrolyte along with a UV lamp. This photoelectrolytic cell is similar to the photoelectrolytic cell described above with respect to Figure 2. For example, a photoelectrolytic cell such as the one shown can be used to reduce the photo-oxidized sensitizer back to a sensitizer to prevent the accumulation of species that can react with solvated electrons. In other embodiments, a photoelectrolytic cell can be used to increase the pH around the electrode, and thus minimize the reaction between solvated electrons and protons. In yet another embodiment, a photoelectrolytic cell can be used to increase the concentration of solvated electrons under certain conditions, thereby generating hydrogen gas which can significantly increase the photodestruction efficiency of PFAS.

[0211] We believe that oxidized sensitizers may undergo further reactions. For example, if iodide is the sensitizer, the following reactions may occur: I - (Iodine) + hn (UV photon) → I · (iodine radical) + e aq - (solvated electron) I · +I · →I2 (iodine) I2+I - →I3 - (Triiodide anion)

[0212] Iodine radicals, iodine, and triiodide anions are all byproducts of photodegradation. All of these species are efficient scavengers of solvated electrons and have a higher second-order rate than PFAS in their reaction with solvated electrons. The presence and accumulation of these species reduces the efficiency of PFAS decomposition, and therefore, various embodiments can remove these species. As mentioned above, one way to achieve this is to introduce a sacrificial reducing agent that can reduce the photochemical byproducts back to the original sensitizer. An example of a sacrificial reducing agent that can be used in various embodiments is sulfite. Sulfite can react with the iodide product as follows: SO3 2- +I · →SO3 - +I - 2SO3 2- +I2 → 2SO3 - +2I - 2SO3 2- +I3 - →2SO3 - +3I -

[0213] These reactions are thought to occur via a series of sulfur-iodine intermediates. Furthermore, the chemistry appears to be particularly well-suited for iodides.

[0214] In other embodiments, iodide byproducts can be electrically reduced. 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) within the photolysis reactor. In the case of iodide as the sensitizer, the following reaction may occur at the cathode. I · +e - →I - E ° = +0.93V / SHE I² + 2e - →2I - E ° = +0.620V / SHE I3 - +2e - →3I- E ° = +0.536V / SHE

[0215] Depending on the pH and temperature of the water, iodine is also hydrolyzed, and I3 - , IO - HOI2 - And several products such as HOI can be produced. Electrodes that can be used in various embodiments may include Ru or Pt-based electrodes, metal oxides such as TiO2 as cathode materials capable of reducing triiodide to iodide, and graphene oxide deposited with Cu-Pt dimetallic nanoparticles for reducing triiodide to iodide.

[0216] To complete the circuit, the appropriate oxidation process takes place at the anode. Several possible anodic reactions exist in aqueous media, but if a high overpotential is present, the following reactions may occur at the anode. 2H2O → O2 + 4e - +4H + E ° = -1.23V / SHE

[0217] By combining the half-cell reactions of iodine reduction and water oxidation, the following overall reactions can be obtained in various embodiments. I2 + H2O → 2I - +1 / 2O2(g)+2H +

[0218] The products from this reaction are acid and O2, both of which are undesirable because they can react with solvated electrons. This problem can be mitigated in various embodiments, for example, by neutralizing the acid with the addition of a base such as sodium hydroxide, or by removing the oxygen gas by blowing in an inert gas. Another way to avoid oxygen interference is to provide the electrodes in separate compartments.

[0219] In some embodiments, the production of O2 from 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. The oxidation of carbon at the anode is a Faraday process involving the following reactions: 1 / 4C + 1 / 2H2O → 1 / 4CO2 + H + +e - E ° =0.7~0.9V / SHE

[0220] The oxidation of H2O can be avoided in various embodiments by the addition of a sacrificial reducing agent. Similar to the chemical reaction for UV sulfite / I2 described above, sulfite could be added to the reaction solution. In this case, the anode and overall reaction are as follows: Anode (oxidation): SO3 2- +2OH - →SO4 2- +H2O+2e - E ° =0.936V / SHE Cathode (reduction): I2 + 2e - →2I - E ° = +0.620V / SHE Overall response: I2+SO3 2- +2OH - →2I - +SO4 2- +H2O

[0221] In this case, sulfate ions (SO4 2- ) is a reaction product, similar to the acid. The sulfate has a low affinity for solvated electrons and therefore does not compete with PFAS for solvated electrons.

[0222] Another option that can be used in various embodiments is S2 that undergoes oxidation. -2 This involves including polysulfide species such as those found in the reaction solution. Anode (oxidation): 2S2 2- →S4 2- +2e - E ° =0.497V / SHE Cathode (reduction): I2 + 2e - →2I - E ° = +0.620V / SHE Overall response: I2+2S2 2- →2I - +S4 2-

[0223] Various embodiments may involve electrochemistry to generate solvated electrons and thus reduce other oxidized photosensitizers back to their original form. For example, in some embodiments, ferrocyanide Fe(CN)6 at wavelengths shorter than 313 nm 4- Using irradiation, solvated electrons and ferricyanide anion Fe(CN)6 3- This can generate ferricyanide ions, which can then be reduced to ferrocyanide anions at the cathode. Fe(CN)6 4- +UV photon → Fe(CN)6 3- +solvated electron Fe(CN)6 3- +electron→Fe(CN)6 4- (Reaction at the cathode)

[0224] Sulfites can also act as sensitizers, especially at shorter wavelengths, such as 222 nm or 185 nm. In this case, solvated electrons and sulfite radicals (SO3) .- ) is generated. The sulfite radical dimerizes to form dithionate S2O6. 2- These can form or undergo further reactions. These types of electrolytic reductions can reduce the amount of sulfite required.

[0225] Photoelectrolysis devices can enhance the efficiency of PFAS breakdown in several ways. As mentioned above, photo-oxidized sensitizers can be electrochemically reduced back to sensitizers. Photoelectrolysis devices can also reduce the presence of scavenging species. For example, oxygen is an efficient scavenger of solvated electrons and hinders PFAS breakdown. Reducing oxygen levels is useful. Oxygen levels can be reduced by electrochemically reducing oxygen to less reactive species such as water. In this case, the electrolytic reaction can occur before and / or during photodegradation. The substitution of fluorine on PFAS for hydrogen requires two electrons. This mechanism is thought to involve two separate one-electron reduction steps. One of these electrons can be provided by a reaction with solvated electrons, and in an electrolytic device, the second electron can be provided electrochemically.

[0226] In some embodiments, the anode may consist of a semiconductor polymer on a conductive substrate such as a metal or carbon electrode. For example, Al 3+ Metals that oxidize to diamagnetic species having empty d-shells, such as Zn 2+Filled materials such as the above may be used. In some embodiments, a polymer semiconductor can be coated onto the anode to prevent the diffusion of potential capture species that may compete with the breakdown of the PFAS. For example, the anode may be coated with an oxidizable substance. Examples of oxidizable substances that may be used in various embodiments include, but are not limited to, π-conjugated polymers including polyacetylene, polyaniline, polythiophene, polypyrrole, poly(p-phenylene), poly(p-phenylenevinylene) and their derivatives, as well as polymers based on reduced forms of n-type semiconductor polymers or blends thereof. Examples include, but are not limited to, polymer quinones (PQ), poly(5-amino-1,4-naphthoquinone) (PANQ), poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM), poly(anthraquinonyl sulfide) (PAQS), poly(2-vinylanthraquinone) (PVAQ), polymer-linked pyrene-4,5,9,10-tetraone (PPYT), naphthalenediimide (PNDI) derivatives, pyromellitic diimide (PPMDI) derivatives, polylactam / lactone derivatives, polymer isoindigo (IIG) derivatives, polymer diketopyrrolopyrrole (DPP) derivatives, and acceptor-acceptor derivatives. Other examples include, but are not limited to, ascorbic acid and alkali or alkali metal salts of polymerized ascorbic acid, or polymers having oxidizable pendant groups, such as anthracene, pyrene, and naphthalene. In some embodiments, the anionic semiconductor is an alkali cation (Na + , K + , Rb + ) or alkali metals (Mg 2+ Ca 2+ Ba 2+) or tetraalkylammonium cations can be charge-equalized. When electrons are removed from the reduced semiconductor, cations are released into the solution. Some of the above undergo irreversible reactions, while others can be recharged to the anionic state by electrochemical reduction. For all polymers having pendant units, the bond between the polymer backbone and the pendant groups should not be hydrolyzable under photodegradation conditions, which are generally high pH (>9). Examples of polymers that may be used in various embodiments are shown in Figures 10 and 11. Figure 12 shows an example of a polymer n-type organic semiconductor structure that may be used in embodiments of this disclosure.

[0227] In some embodiments, the anode may be contained within a UV-opaque material while still allowing contact with the irradiated wastewater. This may be beneficial when organic semiconductor molecules are part of the anode, in order to prevent undesirable photodegradation reactions that could lead to the decomposition of the organic semiconductor and the introduction of undesirable byproducts that can react with solvated electrons.

[0228] Other potential materials that can be coated or bonded to the anode in various embodiments are polymer alcohols and sugars that can be oxidized. Polymer alcohols or sugars can be oxidized to aldehydes, ketones, carboxylic acids, or carbon dioxide. In the case of polymer alcohols or sugars, they may be consumed and may be considered sacrificial reducing agents. An example of a polymer alcohol that can be used in various embodiments is polyvinyl alcohol.

[0229] In some embodiments, oxidizable units can be bonded to polymeric alcohols such as polymer-bonded ascorbic acid, the disodium salt is oxidized to the corresponding dehydroascorbic acid form, and the sodium is released into the solution as shown in the reaction in Figure 13. Water-insoluble ascorbic acid-containing polymers, such as those disclosed in International Publication No. 2000072959, can be used in various embodiments. This polymer acts as an antioxidant through the reaction of ascorbic acid units with oxidizing agents present in the environment. When used in a reaction solution, it can then 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 compounds such as the previously defined molecular oxygen and photosensitizer byproducts.

[0230] In various embodiments, polymeric ascorbic acid and high pH-stable derivatives can be used. For example, in the chemical structure shown in Figure 14, the linking group X is an oxy(-O-), thio(-S-), aza(-NR1-) where R1 is hydrogen, alkyl, or aryl, and alkylene(-(CR2R3)) where R2 and R3 are independently selected from hydrogen, hydroxy, alkyl, or aryl. n -), arylene, and aralkylene, alkalirene, amide (-C(O)NH-) or combinations thereof can be selected. The polymer can be selected from polyacrylate, polystyrene, polyurethane, polycarbonate, polyolefin, polypeptide, polyamide, polyether, and siloxane.

[0231] Other examples of polymers having oxidizable units that can be used in various embodiments include, but are not limited to, sulfur-containing polymers, including polyether-thioethers and polyethersulfones, such as those shown in Figure 15. One such example that can be used in various embodiments is a polymer designed for use in lithium-ion polymers as a polymer electrolyte, as reported by Sarapas and Tew (Sarapas, J.Mand Tew, GN; Poly(ether-thioethers) by Thiol-Ene Click and Their Oxidized Analogues as Lithium Polymer Electrolytes; Macromolecules 2016, 49, 1154-1162).

[0232] The electrodes can be of various shapes or structures. For example, in some embodiments, the cathode may be a metal wire electrode. In other embodiments, the cathode may be a mesh structure, which increases the surface area and allows for more efficient and uniform capture of light-generated products. Examples of electrode materials include high-density graphite, platinum, gold, or other non-dynamically reactive conductors. In some embodiments, metals such as iron, zinc, or aluminum can be used depending on the pH.

[0233] <Recirculation of sensitizer> As described above, in the Advanced Reduction Process (ARP), solvated electrons are generated by UV irradiation of the sensitizer. A common sensitizer is an iodide, and UV light generates solvated electrons and iodine radicals. The solvated electrons react with PFAS molecules. However, the two iodine radicals can combine to form iodine, and iodine and the iodine radical can react with the solvated electrons. Therefore, as the iodine concentration increases, the breakdown of PFAS may be impaired. One solution to this problem, which can be used in various embodiments, is the inclusion or addition of a millimolar concentration of sulfite to the reaction mixture. The sulfite reduces iodine or iodine radicals back to iodide. The sulfite eventually reacts to form sulfate, which does not hinder the photochemical breakdown of PFAS. While the use of sulfite is a good solution, however, high concentrations of sulfite also react with the solvated electrons, resulting in the presence of chemical byproducts.

[0234] In alternative embodiments, electrochemical reduction of iodine or iodine radicals can be used to prevent interference with the breakdown of PFAS. Compared to processes using sulfite as described above, the use of electrochemical reduction allows for the use of lower concentrations or eliminates the use of sulfite altogether. Although electrochemistry involves the generation of oxidized species at the anode, oxidation and reduction can occur in separate compartments of the photoelectrolyte, and therefore the oxidized species do not interfere with the breakdown of PFAS. For example, as shown in Figure 16, photodegradation and iodine reduction may occur in a single compartment, while oxidation may occur in a separate compartment separated by a membrane or ion bridge. Once water is oxidized, an inert gas such as argon or nitrogen can be blown into the chamber to prevent oxygen from entering the compartment where photodegradation and reduction are occurring.

[0235] An example of the electrochemical regeneration of oxidized iodide is shown in Figures 17 and 18, using a system such as the one shown in Figure 9. At one electrode, iodine radicals generated by the photo-oxidation of iodide are reduced to iodide. At the other electrode, an oxidation process takes place. 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 ascorbates, which can also act as reducing agents.

[0236] <Solvated electron> In some embodiments, an electrochemical system can be used to locally change the pH of a solution, as shown in Figure 19. Electrolysis of water at the cathode increases the pH. Hydrogen ions (H) + Since PFAS reacts rapidly with solvated electrons, a high pH is generally desirable for the breakdown of PFAS by solvated electrons. The pH decreases near the anode. Therefore, if solvated electrons are generated near the cathode, they have a sufficient lifetime to react with PFAS. One possible configuration is to have a light source that irradiates a semiconductor such as diamond-like carbon or boron-doped diamond in close proximity to the cathode. Such a system has the advantage of requiring minimal salt concentration and pH adjustment.

[0237] In some embodiments, boron-doped diamond can be used as an electrode and solvated electron source when irradiated with UV photons of sufficient energy. Hydrogen-terminated diamond has been considered a preferred diamond for use in UV generation of solvated electrons because it is a negative electron affinity material. Electrolysis of water causes an increase in pH around the cathode. Irradiation of boron-doped diamond at the cathode may be used, resulting in the generation of solvated electrons with a sufficiently long lifetime to react with PFAS.

[0238] Doped diamond can be used to generate solvated electrons and electrochemically reduce holes formed on the diamond. The doped diamond used in various embodiments may have other atoms incorporated into the diamond structure at the time the diamond structure is synthesized.

[0239] For example, in some embodiments, solvated electrons can be generated by irradiating hydrogen-terminated diamond, as described in "Degradation of perfluorooctanoic acid with hydrated electron heterogeneous catalytic system," Liu, G.; Feng C.; and Shao, P.; Environ. Sci. Technol. 2022, 56, 6223-6231. In this process, UV light can be used to propel electrons from the valence band of the diamond to the conduction band. The electrons are released into an aqueous solution. The solvated electrons can then react with the PFAS. For example, in some embodiments, the diamond may be irradiated in one compartment of an electrochemical cell. The other compartment may contain iodide and may be connected to the first compartment by a cation exchange membrane. As photodegradation proceeds, the solvated electrons generated by the irradiation of the diamond react with the PFAS, and the electron "holes" in the valence band of the diamond are reduced by the reaction of the iodide to iodine at the electrodes. This is an example of a galvanic apparatus. However, since iodine is neutral and not hindered by the membrane, it accumulates within the cell and eventually diffuses across the membrane barrier. An improvement to this is to irradiate the diamond while applying a voltage across the two electrodes so that protons are reduced to hydrogen at the cathode, raising the pH around the cathode. The higher pH at this electrode allows the photochemically generated solvated electrons to persist longer, giving them 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 by blowing an inert gas (e.g., argon or nitrogen) into the compartment. Other species can also be added to this chamber to lower the potential. These species include, but are not limited to, sulfites, iodides, ascorbic acid salts, ascorbate anions, and readily oxidizable metal ions.

[0240] <Hydroxyradical generation at 185nm>

[0241] In some embodiments, gases such as hydrogen can be produced by the electrolysis of water. Using hydrogen gas in conjunction with vacuum UV photolysis can significantly accelerate the decomposition of PFAS.

[0242] When an aqueous solution containing PFAS is irradiated with 185 nm UV light, the PFAS is moderately decomposed via the generation of 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 in conjunction with the simultaneous electrochemical generation of hydrogen gas. In such embodiments, irradiation of water at 185 nm results in the generation of hydroxyl radicals in the aqueous PFAS solution in the presence of hydrogen gas.

[0243] Under basic conditions, hydrogen gas reacts with hydroxyl radicals to form hydrogen atoms and water, and the hydrogen atoms generate solvated electrons. This combination of electrochemical generation of hydrogen gas in water and irradiation of water with 185 nm light to generate hydroxyl radicals can be used in various embodiments for a more efficient PFAS breakdown process.

[0244] By generating hydrogen gas by electrolysis according to various embodiments, the need to separately supply hydrogen gas to saturate the solution is avoided. In addition to being more complex, such processes involve the use and storage of highly flammable materials. Rather, by generating hydrogen gas electrochemically using the method described herein, the hydrogen gas can be generated in close proximity to the location where light is absorbed, for example, less than 2 cm, or about 0.5 to 2 cm, or about 1 cm.

[0245] For example, in some embodiments, a photoelectrolytic cell as shown in Figure 20 can be used. A light source, such as a 185 nm light source, can be placed in a test tube or other transparent container and immersed in the PFAS solution. The electrodes may be wrapped around the test tube, for example, at a position about 1 cm from the end of the test tube. A voltage sufficient to generate hydrogen gas can be applied to both ends of the electrodes. These electrodes are electrically connected to electrodes in a separate compartment where oxidation occurs. If water is the reducing agent, oxygen is the product. The electrodes may be, for example, a mesh. The electrodes may be, for example, platinum, titanium, or stainless steel. In some embodiments, the electrodes may be platinum-coated titanium, such as a platinum-coated titanium mesh. For example, the cathode may 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 ways.

[0246] After photolysis is complete, excess hydrogen can be electrochemically oxidized, reversing the flow of current and thus reversing the electrochemical process to produce water.

[0247] Vacuum ultraviolet (VUV) is defined as the portion of the electromagnetic spectrum between 100 and 200 nm. A mercury lamp can emit 185 nm in this region. As shown in Figure 21, water absorbs 185 nm radiation and can decompose into hydrogen radicals and hydroxyl radicals with a quantum efficiency of approximately 0.3, while hydroxide also absorbs 185 nm light and generates hydroxyl radicals and solvated electrons with a quantum efficiency of approximately 0.1. Furthermore, water absorbs 185 nm radiation and can form hydroxyl radicals, solvated electrons, and protons with a quantum efficiency of approximately 0.045.

[0248] In various embodiments, hydrogen gas can be generated electrochemically by electrolysis of water near the location where UV light is absorbed. The electrochemical generation of hydrogen at the electrodes results in an increase in pH. This system does not require an external hydrogen source. This allows for the construction of a simple and inexpensive device that does not require additional chemicals such as hydrogen or sulfites. Furthermore, after photolysis is complete, excess hydrogen can be reacted with oxygen.

[0249] The electrolysis of water may be continuous or intermittent during the photolysis process. At high pH levels, such as 9–12, an intermittent electrolysis process may suffice, primarily to provide a high concentration of hydrogen gas. Continuous electrolysis increases the pH in the volume surrounding the electrodes, and is therefore sometimes preferred at neutral pH levels, such as 6–8. In some cases, pH adjustment is not necessary. However, in some embodiments, such as when the pH is below approximately 6, it may be necessary to raise the pH by adding a base or other means.

[0250] The above method provides a way to destroy PFAS with minimal additives. Therefore, it may be useful as a device capable of treating drinking water to remove PFAS, such as in the form of a self-contained household unit that can be operated by connecting to a power source, such as a power outlet, and a household water dispenser. Alternatively, it can be used in conjunction with an RO system to destroy PFAS in RO-rejected water. Such a system can be deployed in small commercial or residential facilities. The main by-products of the reaction are free fluoride and carbon dioxide, as well as hydrogen and oxygen resulting from the electrolytic 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.

[0251] <Reduction of by-products by non-mobile media> Non-electrochemical methods that can be used in various embodiments include utilizing polymer species as a non-mobile medium capable of reducing oxidized by-products of a photochemical reaction back to the original sensitizer, such as iodide. The non-mobile medium may include, for example, beads or membranes or other structures having a polymer-bound reducing agent. For example, in the case of iodide as a sensitizer, the oxidized by-product (iodine radical, iodine, or triiodide) can react with polymerized ascorbic acid, which can be used as a polymer binder in various embodiments. In such embodiments, salts such as sodium sulfite are not often required, and the polymer-bound ascorbate and the oxidized form can be physically separated from the photodegradation reaction. Figure 22 shows one possible configuration. The photodegraded solution is pumped through a cartridge containing a reducing species capable of reducing the photo-oxidized sensitizer back to the sensitizer. The polymer-bound reducing agent is physically separated from the position that captures solvated electrons and therefore cannot react with solvated electrons. For example, the irradiated solution can be pumped through a container containing a material capable of reducing iodine back to iodide. Many of the aforementioned polymer semiconductors can also be included to reduce sensitizer byproducts back to sensitizers. Preferred semiconductor polymers can be chemically or electrochemically regenerated and thus these materials can be reused in subsequent photodegradation. Another example of a polymer medium that can be used in various embodiments to reduce iodine radicals, iodine, or triiodide back to iodide is polymer ferrocene, e.g., polyvinylferrocene shown in Figure 23, or polymers based on reduced forms of the n-type semiconductor polymers or blends thereof listed above. Alternatively, these types of reductions can be achieved in some embodiments by metals or metal alloys such as zinc or aluminum. For example, the solution can be pumped through a column containing metal shots. In the case of metals, metal ions that may be generated from the process should not act as scavengers of solvated electrons.

[0252] Another example of a polymer radical scavenger that can be used in various embodiments is a polymer that can undergo redox reactions, such as a polymer containing a stable radical. One example is a polymer having a tetramethylpiperidine 1-oxyl (TEMPO) side chain, as shown in Figure 24.

[0253] <Oxygen Reduction> In some embodiments, the UV reactor may include one or more electrochemical systems for one or more functions (such as removal of impurities from water, removal or reuse of photoproducts, and / or local pH modification). For example, dissolved oxygen in water may compete with the sensitizer in capturing hydrated electrons and therefore may be removed in some embodiments. Several cathode-driven O2 reduction (ORR) reactions can be achieved by electrochemical systems according to various embodiments, such as the following: O2 + 2H + +2e - →H2O2E o = +0.69V / SHE O2 + 2H2O + 4e - →4OH - E o = +0.40V / SHE O2 + 4H + +4e - →2H2O E o = 1.23V / SHE

[0254] <Alternative solvents> In some embodiments, the decomposition of PFAS can be carried out using solvents other than water. In some such embodiments, electrochemistry can be used in a polar aprotic solvent to generate highly reduced or oxidized species, which can then be photodegraded 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 such as dicyanoanthracene (DCA), which can be used in various embodiments, can be electrochemically radicalized to generate a radical anion (DCA - It is reduced to a dicyanoanthracene radical anion excited state (DCA), which is a more powerful reducing agent. -* This can generate ). Other aromatic species that can be used are 2,6-diisopropylphenyl-naphlene and perylenebisimide. Since many of the radical anions that can be used in various embodiments are absorbed in the visible or near-UV region of the electromagnetic spectrum, this approach has the potential advantage of allowing the creation of highly reactive species at lower energies (below UV-C). This may also allow for more complete absorption of lamp energy when used with higher energy photons. An example of a process involving aromatic compounds is shown in Figure 25.

[0255] In some embodiments, the photochemical reactor may include an electrochemical system for decomposing pharmaceuticals, hormones, pesticides, antibiotics, and other persistent contaminants such as washing solvents.

[0256] <Post-processing steps>

[0257] Following the photochemical breakdown of PFAS, it may be desirable to further treat the solution before final disposal or recycling of the photodegraded wastewater. A potential post-treatment scheme is shown in Figure 26. In some cases, all of these steps may be followed. In other cases, only one or some may be required. The post-treatment steps may be performed sequentially, and in some cases, a given process may perform two or more of these functions at once.

[0258] The post-treatment used in various embodiments may depend on the treated water outlet. In some industrial environments, it may be desirable to reuse or recover the water. In other cases, the treated water may be returned to the environment. In other cases, the water may be evaporated or incinerated. The goal of post-treatment may be to prepare the water to specifications for reuse or to meet regulatory or anticipated regulatory requirements. In other cases, a portion of the photochemically treated water may be treated with a membrane, in which case membrane rejects (water that does not pass through the membrane) are recycled back to a photoreactor for further treatment.

[0259] The schematic diagram shown in Figure 26 illustrates the steps of a possible post-treatment process. In some scenarios, it may be necessary to perform all the steps outlined. In many scenarios, only some of the post-treatment steps are required. In many embodiments, it is necessary to adjust the pH to 6-8.

[0260] Sensitizers can be the most expensive reagents used in photoreduction processes, and therefore, it may be desirable to recover the sensitizer or a material that can be readily converted into a sensitizer. When iodide is the sensitizer, one useful method for capturing the iodide is to electrochemically reduce it to iodine or polyiodide in a specific electrode. To recover the iodide, the captured polyiodide can be electrochemically or chemically reduced from the iodine-containing electrode. To achieve this, it may be preferable to lower the pH to 5-8, as iodine and polyiodide are susceptible to other reactions at high pH. Excess sulfites can potentially reduce the efficiency of the electrochemical process, and therefore, a step involving the destruction or removal of sulfites before sensitizer recovery may also be preferable.

[0261] In some applications, recovering iodide may not be economically viable, but removing iodide from final treatment water may still be necessary. In this case, iodide, fluoride, sulfite, or sulfate can be removed by adjusting the pH and then passing the solution through one or more anion exchange media. Further iodide reduction can then be achieved using final finishing processes such as GAC treatment to meet reclaimed water specifications or regulatory requirements.

[0262] In some embodiments, all anionic components, including sulfites, iodides, sulfates, and fluorides, can be simultaneously removed by an anion exchange medium, with or without pH adjustment, such as a direct finishing means for photochemically treated water.

[0263] In some embodiments, the photochemically treated water can be removed by an evaporation process such as thermal vaporization or spray drying, and the ions and their salts can be recovered by precipitation.

[0264] A potentially low-cost but more time-consuming post-treatment, which can be used in various embodiments, involves lowering the pH by adding lime to settle and clarify the solid, and then producing precipitates such as fluorides and sulfates. The clarified water can then pass through a GAC ​​bed or go through a final finishing process such as RO.

[0265] To return water containing PFAS to the environment, these molecules must be removed to appropriate levels to comply with existing regulations regarding the permissible concentrations of certain PFAS molecules. While photoreduction processes can successfully destroy most of the regulated PFAS, some small amounts of new PFAS and polyfluorides may be generated. These molecules currently have no specific restrictions. Regulations may be changed in the future to include these materials. One option for eliminating these materials, which may be used in various embodiments, is to perform a thermal oxidation process using persulfates as a post-treatment step. Alternatively or additionally, electrolytic processes may be used to reduce or eliminate these materials. Another method, which may be used in various embodiments, is nucleophilic substitution of fluorine atoms from these molecules, increasing the amount of free fluoride and reducing the levels of PFAS and polyfluoride species. These post-treatments can result in the near-complete destruction of materials containing carbon-fluorine bonds.

[0266] Various UV-ARP processes can be carried out at high pH, ​​which is highly caustic. Therefore, in some embodiments, the post-treatment solution may include lowering the pH to 6–8 by adding an acid. In addition to lowering the causticity of the solution, some subsequent post-treatment steps are more effective at lower pH.

[0267] Various UV-ARP processes utilize sensitizers and sacrificial electron donors. For example, in UV-ARP at 254 nm, the sensitizer may be an iodide, and the sacrificial donor may be a sulfite. At shorter wavelengths, such as 254 nm and 185 nm, sulfites may also be effective sensitizers. Excess sulfite can be converted to sulfate by oxidation using air, oxygen, or peroxides, or by electrochemical oxidation. UV light can be used to accelerate the oxidation of sulfite to sulfate. However, as mentioned above, sulfite can hinder the recovery of iodide oxidized species such as iodine, triiodide, or other polyiodides. Therefore, in some embodiments, it may be preferable to reduce or remove sulfite before electrochemically recovering the iodide species from the post-treatment solution.

[0268] Sensitizers are often the most expensive reagents in ARP. Iodide salts are frequently used as sensitizers. Therefore, a method for recovering iodide, such as those disclosed above, is desirable.

[0269] <Iodine recovery> In some embodiments, iodide can be recovered by an iodide-specific anion exchange membrane (AEM). In some embodiments, the AEM can be used in conjunction with an electrochemical cell for iodine-iodide recirculation and recovery.

[0270] In some embodiments, photodegradation conditions may require a high pH, ​​a sensitizer, and one or more inorganic salts. Photochemical decomposition of PFAS results in the formation of fluoride ions. Further processes can be used to purify the water and recover the valuable material. For example, in one embodiment where iodide is used as a sensitizer, the iodide can be oxidized to iodine, which is relatively insoluble in water. The iodine can be precipitated and recovered by filtration. However, in some cases, the iodine concentration is low enough that all of the iodine remains in the solution. In this case, the precipitation process is not effective. Also, iodine is unstable at high pH. Therefore, some embodiments may further include lowering the pH to 3-8 or 5-7 to recover the iodine more completely. The pH can be lowered by using a suitable acid, such as a mineral acid.

[0271] Sulfites also reduce iodine to iodide. To enable the recovery of photosensitizer species in various chemical forms, such as iodide, separation processes can be used to isolate the photosensitizer from other components, such as sulfites. These methods include, but are not limited to, ion-exchange membranes, ion-selective resins, and size exclusion materials.

[0272] In some embodiments, such as those in which sulfites are present, post-treatment may be carried out to convert the sulfites to sulfates. For example, sulfites may be converted to sulfates by adding a suitable oxidizing agent to the reaction solution after UV treatment. Examples of oxidizing agents that may be used in various embodiments include, for example, air, oxygen, and / or hydrogen peroxide. Oxygen or air may be preferred in some embodiments because it oxidizes sulfites but not iodide, and can therefore be used in excess concentrations. Alternatively or additionally, in some embodiments, other oxidizing agents may be used to selectively remove sulfites. In some embodiments, the post-photolysis process that converts sulfites to sulfates may be achieved or accelerated by the addition of a catalyst or electrochemically.

[0273] In some embodiments, the iodine species can be recovered by adding a tetraalkylammonium salt, such as tetraalkylammonium hydroxide, which can directly precipitate iodide ions to form tetraalkylammonium iodide. In other embodiments, the iodide can be removed by complex formation with a quaternary ammonium or other cationic polymer. Furthermore, the cationic polymer material can be blended with the electrode coating. However, tetraalkylammonium cations tend to decompose under strongly alkaline conditions, as they tend towards Hoffmann elimination among other decomposition pathways. Therefore, cationic units can be selected from those whose stability has been proven. These include, but are not limited to, alkyltrimethylammonium cations, cyclic ammonium cations, and imidazolium cations, whose alkyl chains are longer than four carbon atoms. Other cationic centers that can be used include phosphonium cations, cobaltocenium cations, and ruthenium cations.

[0274] In some embodiments, after the sulfite has been converted and / or removed, the iodide can be oxidized to iodine, which can then be precipitated. The precipitated iodine can then be recovered. In some embodiments, the iodine can be electrochemically precipitated within a module, the module can be removed, and the iodine within it can be recovered and reused. A similar series of reactions can be used to recover pseudohalogen species that can be oxidized to neutral, insoluble species in an aqueous medium.

[0275] Various embodiments include processes that enable the efficient destruction of PFAS materials, including the use of an electrochemical system to convert the reaction products of a UV sensitizer back into the original sensitizer. For example, in some embodiments, iodine species can be recovered from a solution that has been photodegraded by electrochemical means.

[0276] For example, some methods for recovering iodine species from aqueous solutions include the electrochemical oxidation of iodide-containing aqueous solutions 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. - 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- These include: - , I2, and I - It can be formed from the interaction of three components.

[0277] In some embodiments, the electrochemical oxidation of iodide may involve the use of an iodine-affected electrode, such as an electrode comprising 1) an iodine-affected material having an affinity for iodide, iodine, or polyiodide, 2) a conductive material, and 3) a binder material to provide mechanical and chemical integrity to the electrode. The iodine-affected material may be, for example, an anion exchange resin, starch and / or an inorganic or organometallic complex that forms an iodide salt or polyiodide salt. The conductive material may be, for example, graphite, graphene, carbon nanotubes and / or a conductive polymer or metal. The iodine-affected material may be present in the range of about 20% to about 70% of the composite electrode material. The conductive material may be present in the range of about 10% to about 60% of the composite electrode material. The binder material may be present in the range of about 20% to about 50% of the composite electrode material. For example, in some embodiments, the electrode material may consist of approximately 35% to 60% iodine affinity material, approximately 20% to 50% conductive material, and approximately 30% to 50% binder material.

[0278] Iodine-affinity materials may be used during post-treatment to concentrate and immobilize iodine-containing species present in the treatment solution after UV-ARP. Conductive materials may be used to enable efficient electron transport throughout the electrode composition. Binders may be used to provide chemical and mechanical integrity to the electrode. In some embodiments, conductive materials that act as both conductors and binders may be used. In some embodiments, iodine-affinity materials that are also conductive, such as conductive polymers like polyaniline, may be used. In such embodiments, the electrode may consist of only two components.

[0279] The binder material can provide mechanical integrity to the electrode and support the electrochemical process. The iodine-affinity material and conductive material may be, for example, organic or inorganic powders, and therefore, the binder material, such as a polymer, may be required to maintain the structural integrity of the electrode and to make the electronic network continuous by bonding the active material and conductive additive together. In addition to the binder material, such as a polymer, which holds the active material and conductive agent together, it may also function to adhere the electrode to the current collector. Furthermore, the binder material can ensure the electrochemical reaction by promoting the formation of electronic and ionic circuits and supporting conductivity by providing good mechanical integrity. The iodine-affinity electrode may be a freestanding structure (electrically connected but without a current collector), or it may be attached to or bonded to a current collector.

[0280] Examples of binders that may be used include, but are not limited to, polyvinylidene fluoride (PVDF) and / or styrene-butadiene rubber (SBR). PVDF synthesis can usually be carried out by emulsion polymerization or suspension polymerization processes, and commercially available materials such as HSV900 (Arkema) and 5130 (Solvay), each produced by two different methods, are examples. Other binders that may be used include polytetrafluoroethylene (PTFE). Many binders used in lithium-ion battery cathode structures can also be used for this application.

[0281] The purpose of iodine-affinity materials in electrodes that have a high affinity for iodine / iodide / polyiodide is to interact with some or all of the iodide species in the treatment solution and immobilize them in or on the electrode. These iodine-containing species can exist in equilibrium with each other. Therefore, materials that can interact with iodine, iodide, or polyiodide species may be useful. For example, anion exchange membranes are effective for capturing iodide. Anion exchange membranes are cross-linked polymers with low solubility. Iodine is a Lewis acid and therefore can form complexes with electron donors.

[0282] One method for reducing the solubility of various iodine-affinity polymers in aqueous media is by crosslinking the material. Many polymers can be used; for example, starch and other polymer 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 with an electrode capable of reducing iodide. In some embodiments, starch that can be crosslinked to become water-soluble may be used.

[0283] Iodine forms a strong iodine complex with the crosslinked cationic starch derivative N-(2-hydroxyl)propyl-3-trimethylammonium chloride, and this material can be used as an iodine-affinity material in various embodiments. Starch can be, for example, crosslinked starch or crosslinked during ball milling or formulation processes. Other iodine-affinity materials that can be used in various embodiments include crosslinked polyvinyl alcohol (PVA), chitosan, cellulose, several derivatives of cellulose, crosslinked copolymers of N-vinylpyrrolidone (N-VP) and / or copolymers of polyethylene glycol. Water-soluble chitosan may also be used, and its solubility is determined or adjusted by the degree of deacetylation, pH, and crystallinity. One consideration for the selection of an iodine-affinity material is that its solubility in aqueous solution is limited within the time frame of the electrodeposition process.

[0284] Other possible materials having a high affinity for iodides that can be used as iodine-affinity materials in various embodiments include metallocenes, such as ferrocene and its substituted derivatives, or polymeric ferrocenes, such as polyvinylferrocene, all of which form triiodide salts. In yet another embodiment, materials used in organic semiconductors, such as polythiophenes, polypyrroles, and polyanilines that can form polyiodide salts, can also be used as iodine-affinity materials. One iodine-affinity material may be used for the electrode, or a combination of two or more materials, such as those listed herein, may be used in various embodiments.

[0285] Various systems and methods can utilize iodine affinity electrodes to recover iodine species from aqueous solutions, and the iodide acts as a photosensitizer in advanced reduction (ARP) processes used to generate solvated electrons in the breakdown of PFAS compounds. These systems and methods are particularly useful for cost reduction, as photosensitizers are often the most expensive reagents in UV-ARP processes. The use of iodide recovery electrodes allows for the isolation of iodide from other photochemical byproducts and reuse in subsequent additional UV-ARP cycles using different batches of wastewater.

[0286] Unlike other iodine recovery methods used in other settings, such as the use of polyhalide ion exchange resins containing bromine or chlorine, the use of an iodine affinity electrode for iodine recovery as taught herein does not require the addition of such additional highly reactive species. Similarly, halide recovery methods using electrochemical oxidation precipitate the iodide at the electrode and then recover it as a solid. In contrast, the process disclosed herein using an iodine affinity electrode results in the capture of iodide / triiodide / polyiodide in the volume of the electrode. The electrode can then be removed and the iodide can be released by electrochemical reduction using a current in the opposite direction.

[0287] This system and method can be used with treatment solutions having any concentration of iodide, however, lower concentrations result in lower oxidation rates and, consequently, longer electrolysis times. Iodide concentrations above 1 mM may be preferred. In some embodiments, anion exchange materials can be used to concentrate the iodide near the electrodes. In some embodiments, the time required to capture iodine can be shortened by increasing the surface area of ​​the electrodes. Since molecular iodine, and therefore triiodides and polyiodides, are more readily formed at neutral and acidic pH, an operating pH below pH 9 is preferred. Various embodiments involve adding an acid to a treatment solution having a basic pH to bring the pH of the treatment solution to below about 9, for example, about 4 to about 9, or about 5 to about 9. It is also useful if the iodide-containing treatment solution has sufficient conductivity to minimize the overpotential required for iodide oxidation. Therefore, in various embodiments, total electrolyte concentrations above about 10 mM are preferred, and higher concentrations, such as above about 100 mM, may be useful to achieve rapid iodide oxidation. If the solution does not yet contain a sufficient electrolyte concentration, an electrolyte that does not interfere with the oxidation reaction can be added. For example, various embodiments may include adding a suitable electrolyte such as Na2SO4, K2SO4, NaCl, and / or KCl, among others, to increase conductivity before iodide recovery using an iodine affinity electrode.

[0288] When preparing a treatment solution for iodide recovery, since iodide is stable at all pH levels, it may not be necessary to adjust the pH for iodine stability. However, pH can affect the chemical stability of the electrode depending on its composition. While many conductive and binder materials used in electrodes can have good chemical stability, iodine-affinity materials used in electrodes may be pH-sensitive, and therefore, it may be necessary to adjust the pH depending on the selection of the iodine-affinity material and the pH of the treatment solution. In some embodiments, iodine-affinity electrodes may be used in a treatment solution having a near-neutral pH, such as about 6 to about 8, to provide good chemical stability. The treatment solution may be adjusted by adding an acid or base to achieve this pH range before post-treatment using the iodine-affinity electrode.

[0289] In various embodiments, to avoid competition with the oxidation and reduction of water, the iodine affinity electrode may be operated in a voltage range where neither oxidation nor reduction of water is present. For example, in a solution with a pH of about 7, a voltage range of about -1.0 to about 1.2V for Ag / AgCl is appropriate and can be used in various embodiments. If the solution has a higher pH, the voltage range used may shift by -0.059V for every 1 increment in pH. If the solution has a lower pH, the voltage range used may shift by +0.059V for every 1 increment in pH.

[0290] The electrodes can be used, for example, under either constant current or constant potential conditions. In methods and systems using constant current operation, a constant current is applied to the electrodes. To balance speed and efficiency, a current of 0.1 to 10 mA / cm² is used. 2 The range may be due to oxidation, and is -0.1 to -10 mA / cm². 2While this may be for reduction, lower or higher ranges may be used as alternatives. The reaction may continue until the total charge that has passed through is sufficient to substantially or completely load / remove the electrodes, and then it may be stopped, for example. Alternatively, to avoid, for example, oxidation or reduction of water, the reaction may be continued until the voltage reaches the cutoff limit set before the reaction was started, and then it may be stopped. In potentiometer operation, a constant potential may be applied to the electrodes. As described above, for the anode, a potential sufficient to oxidize the iodide to triiodide / polyiodide without inducing oxidation of water may be selected, and for the cathode, a potential sufficient to reduce the triiodide / polyiodide to iodide without inducing reduction of water may be selected.

[0291] The electrodes described above may be part of an electrochemical apparatus. The electrochemical apparatus may include an anode chamber containing iodide, such as iodide in the post-UV-ARP treatment solution, and a cathode chamber that does not contain iodide separated by a cation exchange membrane. In the anode chamber, an oxidation current is applied to the electrodes described, and the iodide is oxidized to triiodide / polyiodide, which is then immobilized on the electrodes. In the cathode chamber, a cathode current is applied to an iodide-capturing electrode loaded with triiodide / polyiodide, and the triiodide / polyiodide is reduced to iodide and then released into the solution.

[0292] Various embodiments of the cell include a two-electrode system in which an unloaded iodide capture electrode is used as the anode and a loaded iodide capture electrode is used as the cathode. An example of an electrolytic system that can be used for iodine recovery is shown in Figure 27. This example includes a two-electrode system in which iodide recovery electrodes are used for both the cathode and the anode. In this system, for example, an iodide recovery electrode pre-loaded with triiodide / polyiodide is used as the cathode and an empty iodide recovery electrode is used as the anode. The cathode is initially placed in an iodide-free iodide recovery solution at the start of electrolysis. The anode is placed in an iodide-containing solution. Current is applied to the electrodes from an external power source so that triiodide / polyiodide is reduced to iodide at the cathode and the iodide is oxidized to triiodide / polyiodide at the anode. During electrolysis, the concentration of iodide in the cathode chamber increases as it is released from the cathode, and the concentration of iodide in the anode chamber decreases as it is stored in the anode in the form of triiodide / polyiodide. When the reaction is complete, electrode B is depleted of triiodide / polyiodide and placed in a new iodide-containing solution, where it acts as the anode, while electrode C is fully loaded with triiodide / polyiodide and placed in a new iodide recovery solution, where it acts as the cathode. In this way, iodide is recovered from the iodide-containing solution.

[0293] Various embodiments of the cell also include a three-electrode system in which the iodide recovery 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 as alternatives. In this system, the iodide recovery electrode is initially used as an anode in an iodide-containing solution, such as a post-UV-ARP treatment solution, by applying a controlled voltage between the WE and RE to oxidize the iodide to triiodide / polyiodide. Both the CE and RE may be in water, with the CE reducing the water to equilibrium the current flow. Once the triiodide / polyiodide is loaded onto the iodide recovery electrode, the WE chamber is switched to an iodide-free solution. The WE is then used as the cathode to reduce the immobilized triiodide / polyiodide to iodide released into the recovery solution. CE oxidizes water. By adding a sacrificial oxidizing agent (e.g., O2) and a reducing agent (e.g., sulfites) to the CE chamber, the required cell voltage can be reduced.

[0294] In some embodiments, alternative iodine-affinity electrodes may be used. The electrode may be a bilayer cathode having a first layer formed from a conductive material and a second layer in contact with the first layer, the second layer adsorbing triiodide ions, and the triiodide ions being reduced at the interface between the first and second layers. The first layer may include a two-dimensional carbon structure such as graphene or carbon fiber cloth. The second layer may include, for example, polypyrrole, polyaniline, or poly(3,4-ethylenedioxythiophene) at least.

[0295] Various embodiments include iodide / iodine / triiodide / polyiodide-specific electrodes, and methods and apparatus for capturing and / or recirculating iodide / iodine / triiodide / polyiodide from aqueous media, such as capturing iodide / iodine / triiodide / polyiodide for repeated use in UV-ARP and returning it to a photochemical reactor for recirculation.

[0296] In some embodiments, iodine can be recovered from the post-treatment solution by passing the solution through a module containing an anion exchange medium that forms a complex with iodide. This step can be performed, for example, after pH adjustment and sulfite removal as described above. The pH can be lowered, for example, to a range of about 4 to about 9, or about 5 to about 9, by adding acid.

[0297] In other embodiments, iodide can be recovered using an anion exchange membrane. 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 include Type I resins containing trialkylammonium chloride or hydroxide, and Type II resins containing dialkyl 2-hydroxyethylammonium chloride or hydroxide. Some examples of these resins are Dowex 1X2, Dowex 1X4, Dowex 1X8, Dowex 2X8-100, 2X8-200, and 2X8-400. Weak anion exchange resins lacking exchangeable ions can also be used.

[0298] For example, in some embodiments, after photolysis, the pH can be adjusted, and then the solution can be passed through or flowed through an ion-exchange membrane, after which the iodide can be bonded to the membrane. The iodide can then be released by passing a salt solution, such as a sodium chloride solution, through the membrane, returning the iodide to the solution. The solution containing the released iodide can be added to the UV-ARP reactor for reuse. Therefore, the salt should be selected so as not to interfere with the subsequent photochemical reaction. 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 include species that have a high affinity for solvated electrons or have strong absorption in UV from 180 nm to 400 nm. Sodium nitrite and sodium nitrate are two examples of salts that are unsuitable for iodide substitution because the nitrates are absorbed by UV and also react with solvated electrons.

[0299] The concentration of the salt solution can be selected to be high enough to release and return iodide into the solution. For both type I and type II resins, the affinities for various anions are known. The required salt concentration can be determined by determining the relative affinity of iodide and the selected salt and comparing it with the iodide concentration of the starting solution.

[0300] <Removal of PFAS> In some embodiments, for example, when further reduction of the PFAS concentration is required prior to discharge of the treated wastewater to meet stringent EPA limits, the photochemically treated liquid may undergo one or more further post-treatment processes to further reduce the level of PFAS. Some processes that can be used for further reduction of the PFAS concentration are granular activated carbon (GAC), ion exchange or reverse osmosis. In some embodiments, the ion exchange resin may be regenerable. However, the efficiency of these processes can be affected by the presence of high concentrations of ions.

[0301] Even after the acidification step, oxidation step and iodine recovery step, high concentrations of fluoride ion species and possibly sulfates may still be present in the solution. Thus, in some embodiments, the reduction of the concentrations of these sulfates and fluorides can be achieved by adding alkaline earth-containing species to the post-treatment solution. Examples of alkaline earth-containing include some calcium or barium compounds. In some embodiments, the use of calcium compounds may be preferred for economic reasons or the like. Suitable calcium compounds include calcium hydroxide and / or calcium oxide. Alkaline earth ions react with fluorides and sulfates to form fluorite (CaF2) and CaSO4 (anhydrite) or CaSO4 .Minerals such as 2H2O (gypsum) may form, which can precipitate from the solution. In some embodiments, the fluoride can be precipitated by adding, for example, hydroxyapatite to form fluoroapatite. The solid can then be allowed to settle, and the supernatant can be subjected to further processes to remove residual PFAS. Alternatively, in some embodiments, the solid can be removed by electrocoagulation, which changes the surface charge of the suspended particles, leading to aggregation and precipitation of the solid material.

[0302] In some embodiments, unreacted target PFAS molecules can be treated by an adsorption process and reintroduced into the photodegradation process.

[0303] Even after the majority of PFASs have been destroyed, some partially fluorinated organic species may still be present. Non-limiting examples of partially fluorinated organic species include fluoroacetic acid, difluoroacetic acid, 2-fluoropropanoic acid, 2,2-difluoropropanoic acid, 1,2-difluoropropanoic acid, 1,1-difluoropropanoic acid, 2,2,2-trifluoropropanoic acid, 1,2,2-trifluoropropanoic acid, 1,1,2-trifluoropropanoic acid, 1,2,2-tetrafluoropropanoic acid, 1,1,2,2-tetrafluoropropanoic acid, monofluorosubstituted butanoic acid, difluorosubstituted butanoic acid, trifluorosubstituted butanoic acid, tetrafluorosubstituted propanoic acid, pentafluorosubstituted butanoic acid, hexafluorosubstituted butanoic acid, and various isomers of other partially fluorosubstituted pentanoic acid, hexanoic acid, heptanoic acid, and octanoic acid. These partially fluorinated organic species contribute to a certain proportion of residual fluorine-containing species as measured by total organofluorine analysis. Some partially fluorinated species are considered toxic. Therefore, wastewater can be further treated after photolysis to reduce or remove residual partially fluorinated species. In some embodiments, prolonged UV irradiation and ARP sufficiently reduce the concentration of these species, but 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, post-treatment may include one or more of various oxidation processes. Potential oxidizing agents that may be used include, for example, various organic peroxides (e.g., and inorganic oxides (e.g., peroxides, peroxydisulfates, bleaches)) and various transition metal oxidizing agents (e.g., permanganates). In some embodiments, these post-treatment reactions can be accelerated by the use of UV irradiation and / or heat.

[0304] Partially fluorinated organic species may be more susceptible to substitution reactions than PFAS. Therefore, various nucleophiles can be added to destroy some of these species. Nucleophiles containing nitrogen or sulfur can be used to substitute fluorine in various embodiments. Some non-limiting examples of sulfur nucleophiles that can be used in various embodiments include, for example, hydrogen sulfide and its salts, thiols (RSH), thiolate anions (RSH). - ), anions of thiol carboxylic acids where R is alkyl, aryl, or arylalkyl group (RC(O)-S - ), as well as xanthanthates (RO-C(S)-S) where R is alkyl, aryl, or arylalkyl. - ) and dithiocarbamate (R2N-C(S)-S - ) anions, and thiosulfate (S2O3 2- Examples include: Some non-limiting examples of nitrogen-containing nucleophiles that can be used in various embodiments include ammonia, amines, hydroxylamines, hydrazines, carbazides, phenylhydrazines, semicarbazides, and amides. For example, these may be mixed with a post-treatment solution and then the mixture may be heated in an autoclave or the like.

[0305] Effluent from post-treatment may still contain contaminants that cannot be released into the environment without treatment. Therefore, after photoreduction, the effluent can be collected and tested for PFAS. Depending on the requirements and the amount of residual PFAS, the effluent may undergo further treatment. For example, additional treatment can be used to remove residual contaminants to an acceptable level. For example, in some embodiments, the systems and methods may include additional systems downstream of the UV photoreduction system, such as the use of one or more of the following individually or in combination: reverse osmosis (RO), nanofiltration (NF), microfiltration (MF), ultrafiltration (UF), ion exchange resin (IXR), and granular activated carbon adsorption (GAC). Furthermore, these techniques can be used in optimization scenarios, thereby allowing the destruction process to operate over a shorter period and the effluent residue to be concentrated using the post-treatment described above. Such configurations enable shorter residence times and higher throughput throughout the destruction process while still maintaining the target of the process effluent.

[0306] The photochemical breakdown of PFAS is a sequential process. Several mechanisms are thought to be responsible for PFAS breakdown. One mechanism involves the substitution of fluorine atoms on the 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 (reaction products) also contain fluorine-carbon bonds. These reaction products may undergo further photochemical breakdown. Some of these molecules are also PFAS molecules and, although not necessarily regulated, their removal may be desirable or necessary in the future.

[0307] One measure of the effectiveness of the destruction of PFAS molecules and their reaction products is the amount of fluoride ions generated. The defluorination percentage (deF%) can be defined as the ratio of the generated fluoride ions to the total number of fluorine atoms in all PFAS molecules. For example, in some photochemical processes, the total defluorination level may be approximately 70–90%. This means that in such cases, up to 10–30% of the fluorine is still bonded to carbon.

[0308] Post-treatment to remove these molecules may include several processes. For example, in some embodiments, partially defluorinated PFAS molecules can be oxidized using persulfates, which may result in complete or near-complete defluorination. For example, the above oxidation process for pre-treatment may also be used for post-treatment. Alternatively or additionally, in some embodiments, electrochemical oxidation may be used to increase the total defluorination level.

[0309] In some cases, it may be beneficial to shorten the photolysis time to reduce the time spent in the photoreactor and to rely on a post-treatment defluorination process to achieve high levels of PFAS destruction. For example, the combination of shortened photolysis time and post-treatment defluorination may be more efficient than photolysis alone, which may require longer processing times using more energy-intensive processes to achieve the same results, and / or may achieve higher levels of PFAS destruction.

[0310] <Reduction of fluoride ions> As previously stated in this disclosure, fluoride ions are products of the photochemical breakdown of PFAS. While some concentrations of fluoride ions are acceptable in water, high concentrations are undesirable. High fluoride concentrations can cause health problems and may impair the capacity of ion exchange resins or granulated activated carbon beds.

[0311] The reduction in fluoride ion concentration after photochemical (direct or reductive, etc.) decomposition of PFAS can be achieved by several means. Some effective methods that may be used in various embodiments include reverse osmosis and column adsorption using special bone carbide carbon filter media or materials such as activated alumina. Bone carbide, also known as Brimac, which may be used in various embodiments, is prepared by washing and drying animal bones, followed by heating the bones to about 700°C in the absence of oxygen. The resulting material is porous with a high surface area and is composed of calcium phosphate, calcium carbonate, and carbon.

[0312] In various embodiments, fluorides can be removed from the post-treatment solution by precipitation. An example of a precipitation process that may be used in various embodiments includes: 1) adding a material that mineralizes fluorides into fluorite CaF2 or fluoroapatite Ca5(PO4)3F to the fluoride-containing solution; 2) allowing the minerals to precipitate; and 3) removing a clear solution from the precipitated solid. Alternatively, the precipitated fluoride minerals may be removed by filtration. In other embodiments, alum can be added to the fluoride-containing solution to solidify the fluorides. In this way, the fluorite can be trapped as an insoluble solid mineral. In yet another embodiment, magnesium hydroxide can be added to the fluoride solution to absorb the fluorides. The resulting fluorite is non-toxic and can be optionally used in other processes, such as for the production of PFAS.

[0313] In some embodiments, fluoride may precipitate as fluorite (CaF2) or fluoroapatite Ca5(PO4)3F. For example, the following materials can be added to the fluoride-containing solution to induce precipitation: 1) slaked lime Ca(OH)2, 2) a combination of water-soluble calcium salt and phosphate for producing hydroxyapatite, 3) hydroxyapatite powder, or 4) bone carbide powder.

[0314] The fluoride treatments disclosed herein can be used alone or in combination with other methods.

[0315] <Sulfate precipitation> ARP often uses sulfites. Some of the sulfites are converted to sulfates during the photochemical process. After photolysis, residual sulfites can be converted to sulfates as described above. For example, many of the processes used to precipitate fluorides as fluorite use sulfates in various embodiments of gypsum (CaSO4). . It can also be used to precipitate as 2H2O. In some embodiments, fluorite and gypsum can be precipitated together. Gypsum can be removed simultaneously with fluorite by the same procedure listed above for the removal of fluorite or fluoroapatite. Removing these minerals reduces the concentration of free ions in the solution.

[0316] <Finishing Process>

[0317] Effluent from post-treatment may still contain contaminants that cannot be discharged into the environment without treatment, even after one or more post-treatment steps have been applied. A finishing step can function as a final treatment unit that may be useful or necessary to remove residual contaminants, such as reducing residual contaminants to below a desired threshold, such as an acceptable level. Some methods of finishing treatment may be included downstream of one or more post-treatment units and may include processes such as reverse osmosis (RO), ion exchange resin (IXR), granular activated carbon beds, and / or membrane filtration. Finishing steps may be considered separate steps or additional post-treatment steps. In some embodiments, finishing may be performed after photolysis and post-treatment steps to limit the levels of one or more components in the wastewater, for example, to below the regulatory limits required for the release of treated wastewater into the environment.

[0318] An example of a PFAS treatment method that is completed by a post-processing step and a subsequent finishing step is shown in Figure 28.

[0319] Embodiments of this disclosure include, but are not limited to, the following:

[0320] Various embodiments include ultraviolet decomposition reactors equipped with one or more electrochemical systems capable of reducing photochemical byproducts. For example, in some embodiments, a photoreactor for PFAS decomposition includes an ultraviolet light source configured to deliver 222 nm light and a reaction vessel configured to contain an aqueous solution containing PFAS, wherein the light source is positioned to direct the light onto the solution contained in the reaction vessel. The light source may be a krypton / chloride excimer lamp. Optionally, a second light source, identical or different from the first light source, may be present, and the second or more light sources may also be positioned to direct the light onto the contents of the reaction vessel.

[0321] Various embodiments include a method for destroying PFAS, comprising irradiating an aqueous solution containing PFAS and sulfites with 222 nm light. The solution may further contain a base sufficient to adjust the pH of the aqueous solution to about 10 or higher. The solution may further contain a halide salt such as a bromide salt or iodide salt. The solution may further contain a carbonate.

[0322] Various embodiments include photochemical processes and apparatus for reducing by-products of photosensitizers used in UV photodegradation back to the original sensitizer. The sensitizer may be a halogen or pseudohalogen, such as a bromide or iodide. The photochemical processes 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 by-products of a sensitizer species back to the original sensitizer.

[0323] Various embodiments include processes for PFAS breakdown using a highly reducing process in which an oxidized sensitizer, generated by the interaction of the sensitizer with UV light and the release of solvated electrons, is reduced back to the sensitizer by an electrochemical process. In some such embodiments, the sensitizer is a sulfite and / or iodide. Various embodiments include methods for capturing and / or recirculating iodine, including adjusting the pH to about 3 to about 8 or about 5 to 7, removing any reducing species that can reduce iodine to iodide, and electrochemically oxidizing iodide ions to iodine, in a module or the like that allows for easy recovery of iodine. Various embodiments may also include recovering iodine-containing species by electrochemical oxidation of iodide at an electrode containing an iodine-affinity material and a conductive material such as a conductive polymer, wherein the oxidized iodide species are contained within the electrode, and optionally a binder material is also included, and an electrode for carrying out the method. The iodine-affinity material may be, for example, starch, chitosan, and / or carboxycellulose, or it may be 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 iodine-affinity material is a cationic polymer. The conductive material may be, for example, graphite, graphene, carbon nanotubes, conductive polymers, and / or doped semiconductors and metals. The binder may be polyvinylidene fluoride (PVDF), polyfluoroethylene (PTFE), and / or styrene-butadiene rubber, or polyamide. A voltage of 0.3V or higher can be applied to Ag / AgCl so that the iodide is oxidized to iodine or polyiodide. This method may optionally further include removing the electrode from the solution and then reducing the iodine / polyiodide-containing electrode to release the iodide into the solution. The electrode may be connected to a current collector.

[0324] Various embodiments include a method for recovering and / or capturing and recirculating iodide from a photochemical ARP solution, comprising: 1) adjusting the pH of the photochemical advanced reduction process (ARP) solution to 4-8; 2) contacting the ARP solution with an ion exchange medium; and 3) removing the ion exchange medium from the ARP solution and contacting the iodide-containing ion exchange medium with a saline solution to remove the iodide 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 saline solution may be a mixture of water and sodium chloride, sodium bromide, potassium chloride, potassium bromide, sodium hydroxide, potassium hydroxide, sodium sulfate, or potassium sulfate.

[0325] Various embodiments include methods for capturing iodine, such as in a module that enables iodine recovery, which include adjusting the pH to about 3 to about 8 or about 5 to about 7, removing reducing species, and electrochemically oxidizing iodide to iodine. For example, embodiments include methods for capturing iodine, which include adjusting the pH to about 3 to about 8 or about 5 to about 7, selective removal of reducing species by adding an oxidizing agent and electrochemical oxidation of iodide ions to iodine. In other examples, various embodiments include methods for capturing iodide, which include adjusting the pH to 5 to 7, selective removal of reducing species by adding an oxidizing agent, and selective removal of iodide by passing the solution through an ion exchange medium, or precipitating tetraalkylammonium iodide by adding a tetraalkylammonium salt, or both.

[0326] Various embodiments include photochemical and electrochemical composite apparatuses and processes comprising a UV light source, a boron-doped diamond coated substrate capable of generating solvated electrons upon UV irradiation, and electrodes positioned close to the diamond coated substrate so that the solvated electrons are generated in a high pH region so that they have a sufficient lifetime to react with PFAS and / or other halogenated contaminants. For example, an apparatus for PFAS destruction may include a UV lamp, an electrochemical cell, where the first reducing electrode is a boron-doped diamond acting as a reducing electrode in a compartment, and the second oxidizing electrode is in a separate compartment, with the two compartments separated by an ion-exchange membrane. Various embodiments also include a process for PFAS destruction using a highly reducing process in which the solvated electron source is a boron-doped diamond acting as a reducing electrode in an electrochemical system, thereby generating hydrogen gas and high pH during photodegradation.

[0327] Other embodiments include a photochemical and electrochemical device comprising a UV light source and an electrochemical device capable of reducing photochemical byproducts of sensitizer species to the original sensitizer and / or reducing aromatic species to their corresponding radical anions, the radical anions capable of absorbing UV radiation and reacting directly with PFAS or other halogenated pollutants, and / or reacting with other molecules to produce species capable of reacting with PFAS, for example, reacting with carbon dioxide to produce carbon dioxide radical anions, and generating highly reactive excited states.

[0328] Various embodiments include: 1) a step of identifying the main chemical composition of the waste stream; 2) a step of remediating the waste stream to remove chemicals that may interfere with the efficiency of the photochemical process; 3) a step of enabling the UV photodegradation process by adding a reagent to the treated waste stream containing the following materials: i) at least one reagent capable of absorbing UV photons and generating chemically active species that can react with one or more PFAS upon UV excitation; ii) one or more bases to raise the pH of the solution above 10; iii) optionally one or more chemicals capable of reacting with UV-generated photodegradation products, converting them back to the original sensitizer, or capturing molecular oxygen. 4) optionally, a step of applying a voltage to the cathode so that the UV-generated products of the sensitizer are reduced back to the original sensitizer; 4) optionally, a step of adding an additive base or basic solution to compensate for pH changes caused by the electrochemical or photodegradation process; 5) optionally, a step of purging with an inert gas; 5) optionally, means for providing a suitable flow; 6) optionally, a step of separating the sensitizer or sensitizer by-products to be removed from the reaction mixture; 7) optionally, a step of adding an acid to the UV-photodegraded mixture to lower the pH to 4-8; 8) optionally, one or more modules for capturing either the sensitizer or the reduction products of the sensitizer.

[0329] 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 partitioning a base or acid to change the pH of the reaction mixture; 4) optionally a system for partitioning an inert gas; 5) a device for providing flow; and 6) optionally a module for recovering and / or recirculating either the sensitizer or a reduced form of the sensitizer.

[0330] Other embodiments include a process and apparatus for PFAS decomposition in which an aqueous solution containing PFAS is irradiated with 185 nm UV light and a voltage is applied to an electrode adjacent to the irradiated area to generate hydrogen gas in this area. For example, in some embodiments, the apparatus for decomposing PFAS includes a 185 nm lamp and an electrochemical apparatus capable of generating hydrogen at one electrode. In some embodiments, after photodecomposition, the hydrogen reacts with oxygen. The apparatus optionally also includes a system for removing free fluoride ions after photodecomposition.

[0331] Various embodiments include a photoreactor for PFAS destruction comprising an ultraviolet light source configured to deliver 222 nm light and a reaction vessel configured to contain an aqueous solution, wherein the light source is positioned to direct the light onto the contents of the reaction vessel. The light source may be, for example, a krypton / chloride excimer lamp. The photoreactor according to claim 5 further comprises a second or more light source, identical or different from the first light source, wherein the second or more light sources are also positioned to direct the light onto the contents of the reaction vessel. Various embodiments include a method for PFAS destruction comprising irradiating an aqueous solution containing PFAS and sulfite with 222 nm light, for example, using the photoreactor described above. This method may include adding a base sufficient to bring the pH of the aqueous solution to be treated to about 10 or higher. It may further include adding a halide salt such as 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 that can destroy PFAS at a faster rate than iodine salt under the same conditions in which the bromide salt is present at the same or lower concentrations. The aqueous solution may further contain carbonates. These apparatuses and methods may be capable of destroying more than 90%, more than 95%, or more than 99% of the PFAS in the solution.

[0332] Various embodiments include processes for PFAS breakdown using a highly reducing process in which an oxidized sensitizer, such as a sulfite or iodide, generated by the interaction of the sensitizer with UV light and the release of solvated electrons, is reduced back to the sensitizer by an electrochemical process.

[0333] Various embodiments include apparatus for PFAS destruction, which includes a UV lamp and an electrochemical cell capable of regenerating the sensitizer after photodegradation.

[0334] Various embodiments include a process for PFAS breakdown using a highly reducing process in which the solvation electron source is a boron-doped diamond that functions as a reducing electrode in an electrochemical system, thereby generating hydrogen gas and high pH during photolysis. The solvation electron source may also be a boron-doped diamond that functions as a reducing electrode in an electrochemical system, thereby generating hydrogen gas and high pH during photolysis. The apparatus that may be used in this PFAS breakdown process may include a UV lamp and an electrochemical cell, where the first reducing electrode is a boron-doped diamond located in one compartment, and the second oxidizing electrode is located in a separate compartment, with the two compartments separated by an ion exchange membrane.

[0335] Various embodiments include a method for treating wastewater to reduce PFAS, comprising the steps of: a) mixing the wastewater with a persulfate and an acid or base to raise or lower the pH; b) subjecting the wastewater containing the persulfate and acid or base to an elevated temperature and pressure for a period sufficient for thermal oxidation; and c) subjecting the thermally oxidized wastewater to photoreduction. Photoreduction may be carried out using UV radiation of 222 nm and / or 254 nm. For example, the elevated temperature may include about 100 to about 140°C and the elevated pressure includes about 1 to about 5 bar. Step b may be carried out for, for example, about 15 to about 120 minutes. Some embodiments may further include diluting the wastewater about 1 to about 10 times or about 2 to about 5 times after thermal oxidation and before photoreduction. Some embodiments may further include, after step b and before step c, mixing the wastewater from step b with a second persulfate and acid or base to raise or lower the pH, and then subjecting the wastewater, including the second addition of persulfate and acid or base, to the elevated temperature and pressure for a period sufficient for thermal oxidation.

[0336] Various embodiments include methods for treating wastewater to reduce PFAS, which include mixing the wastewater with persulfates and bases to lower the pH, subjecting the wastewater containing the bases to ozone treatment at a rate and duration sufficient for ozone oxidation, and subjecting the ozone-oxidized wastewater to photoreduction. Photoreduction may be carried out, for example, using UV radiation at 222 nm and / or 254 nm.

[0337] Various embodiments include methods for treating wastewater for PFAS reduction, which include subjecting the wastewater to a pretreatment including thermal oxidation or ozone oxidation, mixing the oxidized wastewater with a photosensitizer containing sulfites, halides, and bases, and subjecting the ozone-oxidized wastewater to photoreduction at 222 nm and / or 254 nm. After oxidizing the wastewater and before photoreduction, the method may also include diluting the wastewater 1 to 10 times, or about 1 to 5 times. [Examples]

[0338] [example]

[0339] [Example 1]

[0340] Electrochemical nitrate reduction. A DI aqueous solution was prepared containing 500 ppm nitrate (8.06 mM NaNO3), 0.5 M Na2SO4, 20 mM NaOH, and 10 μM PFHxS. 100 mL of this solution was added to both the working electrode chamber and the counter electrode chamber of a divided electrochemical cell. The cell was divided using a Nafion 212 cation exchange membrane. Porous iron was used as the working electrode, platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. The working electrode chamber was purged using an argon gas stream. To reduce the nitrate, a voltage of -1.3 V relative to Ag / AgCl was applied to the working electrode for 15 hours. Both the solution recovered from the working electrode chamber and the same nitrate-containing solution were subjected to a photoreduction process to defluorinate PFHxS. The defluorination rate was measured by a photodestruction process, and the results are shown in Figure 29.

[0341] Figure 29 shows a graph of the total percentage of PFAS defluorination by the UV254 photoreduction process of a 500 ppm nitrate solution, with and without electrochemical nitrate reduction pretreatment. The photoreduction reaction conditions were 10 mM Na2SO3 and 2 mM KI. These results demonstrate that photoreduction is unable to defluorinate PFHxS in the presence of 500 ppm nitrate, resulting in 0% defluorination after 24 hours. However, electrochemical reduction of nitrate in combination with photoreduction was shown to be effective in defluorinating PFHxS, achieving >80% defluorination after 24 hours.

[0342] [Example 2]

[0343] Nitrate nanofiltration. Nitrate ions (NO3) - The PFOA degradation dynamics in a membrane rejection solution generated by nanofiltration (NF) were compared with those of reverse osmosis (RO) in the presence of [unclear].

[0344] In the membrane filtration process, 100 ppm NO3 - A 10 L synthetic aqueous solution containing approximately 5 μM PFOA was transferred to a feed tank of a Benchtop Cross Flow Filtration System (Sterlitech Corporation, Auburn, Washington, USA). The benchtop system consisted of an 1812 element housing and either an RO (SKU: 1180001, manufactured by TriSep, Vacaville, California, USA) or NFX (SKU: 1180057, manufactured by Synder, Vacaville, California, USA) spiral membrane element. The neutral synthetic solution was filtered through the RO or NFX system at a flow rate of approximately 2 gal / min and an operating pressure of approximately 250 psi. The membrane permeates were collected separately. A 100 mL sample of membrane rejection was collected at the specified concentration factor in both membrane systems. NO3 in the membrane rejection - The concentration was quantified using UV-Vis absorbance spectroscopy (UV-2600i, Shimadzu, Kyoto, Japan), utilizing its characteristic 301 nm peak and photoreduction at UV254 nm.

[0345] For photoreduction of membrane rejects, 100 mL samples from RO and NFX membrane reject solutions were transferred to separate 100 mL quartz vials (QP062, Aireka Scientific Co., Ltd., Hong Kong). 0.12604 g of Na2SO3 (10 mM) and 0.332 g of KI (2 mM) were mixed into each 100 mL solution. Then, 0.2 mL (20 mM) of 10 M NaOH was added to each solution to increase the alkalinity to pH 12. Finally, the solutions were photodegraded using a UV 254 nm photoreactor (LZC-ORG type, Luzchem Research Inc., Canada). This photoreactor is equipped with eight 10-watt UV 254 nm lamps. During photoreduction, 3 mL samples were taken from the quartz vials at specified time points for defluorination quantification.

[0346] The destructive performance of the treatment process was evaluated and compared using the defluorination rate (DeF%). During the treatment process, free fluoride (F) was extracted by an ion-selective electrode (ISE, Fisher brand accumet solid-state) connected to a Thermo Scientific Orion Versa Star Pro meter. - The concentration was determined. Next, the measured F - Based on this, the defluorination rate (DeF%) is calculated using the following formula:

number

[0347] The results are shown in the graphs in Figures 30 and 31. Figure 30 shows the relationship between the concentration coefficient of membrane rejects using RO and NFX and NO3 - It shows concentration (ppm) dependence. The operating conditions were 100 ppm NO3 - The solution also contained approximately 5 μM of PFOA.

[0348] From Figure 30, NFX is NO3 - It is more effective than RO in that it allows NO3 to pass through the membrane, and NO3 remains in the membrane rejection. - It was found that there was less of it. Compared to NFX rejects, RO rejects contained about twice the concentration of NO3. - NO3 was present in the RO rejection solution with a concentration factor of 3. - The concentration is 290 ppm, which corresponds to NO3 in the NFX rejection solution. - The concentration was higher than (for example, 123 ppm).

[0349] Figure 31 shows a comparison of the defluorination rate (DeF%) from photoreduction of film rejects from RO and NFX films. The film rejects are 100 ppm NO3 - It was also produced at pH 12 from an initial aqueous solution containing approximately 5 μM PFOA along with 10 mM Na2SO3 and 2 mM KI.

[0350] Figure 31 shows that the film rejection from NFX exhibited superior degradation dynamics compared to that from RO. After 4 hours of photodegradation, the sample produced by NFX showed 40.2% defluorination, while the sample produced by RO showed only 23.9%. This difference is attributed to NO3 in the RO sample, which traps UV-generated hydrated electrons, reduces their availability, and inhibits the degradation dynamics. - This is thought to be due to the relatively high concentration of [the substance].

[0351] Both RO and NF showed excellent rejection of long-chain PFAS, but NF did not reject NO3 - It did not reject much. This is thought to be because NF has a larger pore size and lower electrostatic repulsion than RO. As a result, NO3 remains in the film rejection material to capture hydrated electrons, which are essential for promoting the defluorination reaction.- The amount of PFOA degradation decreased. Both methods were effective, but nanofiltration pretreatment resulted in improved PFOA degradation dynamics compared to reverse osmosis in the presence of nitrates.

[0352] [Example 3]

[0353] Thermal oxidation pretreatment. In this example, as in Examples 4-8 below, the wastewater used in the experiment was foam separation (FF) from landfill leachate obtained from ALTRA SANEXEN. PFAS concentrations were measured using the EPA 1633 method with a triple quadrupole mass spectrometer (LCMS-8060, Shimadzu Corporation, USA). The concentrations of all PFAS compounds listed in the EPA (U.S. Environmental Protection Agency) 1633 method, including 40 PFAS analyzers, were measured.

[0354] 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 NaOH.

[0355] The addition of these reagents yielded a turbid solution. The tube was loosely sealed to reduce the significant pressure increase during processing and placed in a pressure vessel. The pressure vessel containing the tube was then heated to 120°C and maintained for 120 minutes. After thermal oxidation, the solution was clear and nearly colorless.

[0356] Figure 32 shows photographs of the untreated sample, the sample after sedimentation, the decanted sample after mixing with potassium persulfate and sodium hydroxide, and the sample after thermal oxidation treatment. These photographs show that the original, highly turbid sample became clear after thermal oxidation treatment.

[0357] A portion of the thermally oxidized sample was further diluted 10-fold, 5-fold, or 2-fold with deionized water (DI water). The UV transmission spectra of the untreated sample and the undiluted and diluted samples after thermal oxidation are shown in Figure 33 below. Table 1 lists the UV transmittance (%) at 222 nm and 254 nm for the untreated wastewater and for samples diluted 0, 2, 5, and 10-fold with DI water after thermal oxidation.

[0358] [Table 1]

[0359] Next, the samples were treated with a photoreactor. Then, 100 mL of diluted and undiluted samples were transferred to 100 mL quartz vials (QP062, Aireka Scientific Co., Ltd., Hong Kong). Next, 100 mL of the solution was mixed with 126 mg of sodium sulfite (10 mM sodium sulfite), 33 mg of potassium iodide (2 mM potassium iodide), and 40-80 mg of NaOH (10-20 mM NaOH) as needed to adjust the pH to approximately 12. The samples were photodegraded separately using a 254 nm photoreactor and a 222 nm photoreactor. The 254 nm photoreactor (LZC-ORG type, Luzchem Research Inc., Canada) 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 222nm photoreactor is provided in another application of the present applicant, U.S. Patent Application No. 63 / 591,040, entitled "SYSTEMS AND METHODS OF PFAS DESTRUCTION," filed on 17 October 2023.

[0360] During the photoreaction, 3 mL samples were taken from quartz vials at appropriate time intervals for PFAS quantification. PFAS concentrations were measured using the EPA 1633 method with a triple quadrupole mass spectrometer (LCMS-8060, Shimadzu Corporation, USA). The total PFAS destruction rate (destruction %) was calculated based on the sum of PFAS detected by the EPA 1633 method, and the results are shown in Figure 34. Figure 34 shows graphs of the total PFAS destruction rates by UV222 and UV254 photoreduction processes at various dilution ratios of the thermally oxidized samples.

[0361] As shown in Figure 34, UV222 generally exhibits better destructive performance than UV254 for thermal oxidation samples. For example, in the case of a 2-fold diluted sample, the total PFAS destructive rate reached 53.9% after 2 hours in the UV222 photoreduction process, while less than 5% destructive rate was observed in UV254 photoreduction after 2 hours of reaction. After 8 hours of reaction, the total PFAS destructive rate increased to 87.5% in the UV222 photoreduction process compared to 48.2% in UV254 photoreduction. The lower dilution in the UV222 photoreduction process requires less solvent, minimizes waste generation, and is therefore very beneficial for wastewater treatment applications as it is practical for large-scale applications.

[0362] Tables 2a and 2b, and 3a and 2b below, show the concentrations of selected representative PFAS compounds during photoreduction under UV222 and UV254, respectively, after thermal oxidation treatment and 2-fold dilution of wastewater samples. 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. The results showed that UV222 and UV254 photoreduction are generally effective against a wide range of PFAS compounds, including perfluoroalkyl carboxylates and perfluoroalkyl sulfonates. In particular, UV222 is more effective in the breakdown of perfluoroalkyl sulfonates (e.g., PFBS). For example, in the case of PFBS with an initial concentration of 168-172 μg / L, the residual PFBS concentration was undetectable after 8 hours of UV222 photoreduction, while 152 μg / L of PFBS remained after UV254 photoreduction.

[0363] [Table 2a]

[0364] [Table 2b]

[0365] [Table 3a]

[0366] [Table 3b]

[0367] [Example 4]

[0368] Ozone oxidation pretreatment. In this example, wastewater was pretreated by ozone oxidation. The same wastewater as in Example 3 was used. The wastewater was allowed to stand for 12 hours. The nearly clear liquid was then decanted. Next, 1.2 g of NaOH was added to 300 mL of the decanted liquid. A turbid solution was formed upon addition of NaOH, and the sample was allowed to stand for 12 hours. Then, 200 mL of the solution was treated with 1000 mg / h of O3 for 6 hours using a portable ozone generator, 1000 mg / h Multipurpose Ozone Machine, manufactured by Shenzhen VANSU Technology Co., Ltd., China. The resulting solution was clear and nearly colorless. The ozone-oxidized liquid sample was further diluted 10, 5, and 2 times with deionized water. The undiluted and diluted samples were analyzed for UV transmittance. Photographs of the wastewater before treatment, after sedimentation, after mixing with NaOH, after further sedimentation, and after ozone treatment are shown in Figure 35.

[0369] Figure 33 shows the UV transmission spectra of untreated wastewater and diluted samples after ozone oxidation, and Table 4 below shows the data from these spectra. Table 4 shows the UV transmittance (%) at 254 nm for untreated wastewater and diluted samples after ozone oxidation.

[0370] [Table 4]

[0371] These results indicate that ozone oxidation improved the UV transmittance of wastewater. However, the transmittance due to ozone oxidation was lower than that due to thermal oxidation.

[0372] Next, the samples were treated with a photoreactor, and the PFAS levels were measured using the same process as described in Example 3 above. Briefly, 100 mL of ozone-oxidized diluted samples were mixed with 126 mg of sodium sulfite (10 mM sodium sulfite), 33 mg of potassium iodide (2 mM potassium iodide), and optionally 40–80 mg of NaOH (10–20 mM NaOH) to adjust the pH to approximately 12, and then photodegraded using either a 254 nm or 222 nm photoreactor. The PFAS levels were measured, and the results of the total PFAS destruction rate (destruction %) are shown in Figure 36. Figure 36 shows graphs of the percentage of total PFAS destruction by UV222 and UV254 photoreduction processes over time for ozone-oxidized samples at 10-fold and 5-fold dilutions. Since PFAS destruction was 0% for both UV222 and UV254 treatments, graphs for 2-fold dilutions are not shown.

[0373] Figure 36 shows that the UV222 photoreduction system exhibited better destructive performance than the UV254 photoreduction system for the ozone-oxidized diluted sample. This is consistent with the results for the thermally oxidized sample in Example 3. In the UV222 photoreduction system, after 8 hours of reaction, the total PFAS destructive rate increased to 61% and 22% for the 10-fold and 5-fold diluted samples, respectively. In contrast, almost no destructive performance was observed with the UV254 photoreduction system.

[0374] Figure 37 shows bar graphs of PFAS destruction results from Example 1 and Example 2. Figure 37 shows the total PFAS destruction rate after 4 hours of treatment in UV254 and UV222 photoreduction systems, following either thermal oxidation or ozono-oxidation as a pretreatment step. Thermal oxidation was more effective than ozono-oxidation in improving the subsequent photoreduction treatment. For 5-fold diluted samples, thermal oxidation pretreatment improved the 4-hour destruction rate to 85.5% and 91.9% in UV254 and UV222, respectively, which is higher than 4.7% and 9.6% in UV254 and UV222 after ozono-oxidation as a pretreatment approach.

[0375] [Example 5]

[0376] Thermal oxidation pretreatment. In this example, thermal oxidation of wastewater was performed using various dosages of oxidizing agents (e.g., potassium persulfate). First, 300 mL of wastewater was mixed with 1.2 g of NaOH (in 3 mL of 10 M NaOH solution). A turbid solution was formed upon addition of NaOH, and the sample was allowed to stand for 12 hours. Next, 30 mL of the decanted solution was placed into individual glass pressure vessels. 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 vessels were loosely sealed and heated to 120°C for 120 minutes.

[0377] Figure 38 shows photographs of solutions after thermal oxidation with various doses of potassium persulfate and sodium hydroxide. Containers a-f are shown in order of increasing dose from the lowest dose (a) to the highest dose (f). The reaction conditions were 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.

[0378] As shown in Figure 38, in the case of solutions with small doses of the chemical substance, the solution still appears yellow after thermal oxidation (containers a-e in Figure 38). However, under the conditions of the highest doses of 150 mM K2S2O8 and 750 mM NaOH, the solution became colorless after thermal oxidation (container f in Figure 38).

[0379] [Example 6]

[0380] Thermal oxidation pretreatment. In this example, thermal oxidation of wastewater was carried out under various pH conditions. Approximately 10 mL of untreated wastewater and 0.4 g of potassium persulfate were added to each of three glass pressure vessels. For the acid reaction condition, 0.2 mL of 1 M sulfuric acid was added to the sample in the first vessel. For the base reaction condition, 0.75 mL of 10 M sodium hydroxide solution was added to the sample in the second vessel. For the neutral reaction condition, no additional chemicals were added to the sample in the third vessel. The pressure vessels were loosely sealed and heated to 120°C for 120 minutes. The resulting solutions were clear and nearly colorless, with some precipitate at the bottom of the vessels. The clear upper layer of each oxidation sample was then diluted 10, 5, and 2-fold with deionized water, and the UV transmittance was measured. Table 5 shows the UV transmittance at 254 nm for each condition of untreated and thermally oxidized samples diluted 0, 2, 5, and 10-fold with DI water.

[0381] [Table 5]

[0382] [Example 7]

[0383] Two-stage thermal oxidation pretreatment. In this example, two-stage thermal oxidation of wastewater was performed, and the results of different reaction time combinations were compared. First, 300 mL of wastewater was mixed with 1.2 g of NaOH (in 3 mL of 10 M NaOH solution). A turbid solution was formed upon addition of NaOH, and the sample was allowed to stand for 12 hours. Next, 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 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 to 15-120 minutes. After the first stage of thermal oxidation, the resulting solution was clear and almost colorless. For the second stage of thermal oxidation, an additional 1.2 g of potassium persulfate was added to the 30 mL of solution in the glass pressure vessel, and the mixture was maintained at 120°C for 30-60 minutes. After the second stage of thermal oxidation, the oxidized samples were further diluted 10, 5, and 2 times with deionized water, and the UV transmittance was measured. Table 6 lists the UV transmittance at 254 nm for untreated raw wastewater and wastewater treated by two-stage thermal oxidation, diluted 0, 2, 5, and 10 times with DI water.

[0384] [Table 6]

[0385] Table 6 shows that two-step thermal oxidation significantly improved UV transmittance at 254 nm compared to untreated wastewater. Thermal oxidation with reaction times of 120 minutes followed by 60 minutes increased the UV transmittance at 254 nm from 0.0% to 11.1% for the undiluted sample. Reducing the reaction time to 30 minutes followed by 30 minutes further increased the UV transmittance at 254 nm to 42.2%. Compared to the 120-minute and 60-minute reaction time combination, the 30-minute and 30-minute combination is beneficial for practical applications due to its higher processing capacity and better improvement in UV transmittance.

[0386] [Example 8]

[0387] Comparison of photosensitizers. In this example, aqueous samples containing PFAS were treated with two different photosensitizer concentrations using photoreduction without pretreatment. The aqueous samples were treated with approximately 0.9 ppm TFA(CF3-COO-), approximately 0.6 ppm PFBA(C3F7-COO-), and 31.8 ppm 7H-PFHpA(H-C6F 12 It included -COO-).

[0388] A first sample of wastewater was mixed with photosensitizer A containing 10 mM Na2SO3 and 2 mM KI at pH 12. A second sample of the same wastewater was mixed with photosensitizer B containing 50 mM Na2SO3 and 10 mM KI at pH 14.

[0389] Next, the two samples are treated in a 750 mL tubular reactor at 254 nm for 24 hours, and samples are taken at appropriate time points for analytical purposes such as kinetic fitting of PFAS degradation and calculation of defluorination performance in the process.

[0390] PFAS levels were measured before and after photoreduction. The degradation dynamics were analyzed using a quasi-first-order dynamic model (ln(C)). TThe calculation is based on the fitting by / C0)=kt), and in the formula, C T C0 and C0 refer to the PFAS concentrations in photoreduction at time T and time 0, respectively.

[0391] Figure 39 shows a bar graph comparing the degradation kinetics achieved using photosensitizer A with those achieved using photosensitizer B. Figure 39 shows the degradation kinetics results for TFA, PFBA, and 7H-PFHpA. In all cases, photosensitizer B yielded remarkably superior results, with reaction rates 4 to 6 times higher than those in this example.

[0392] [Example 9]

[0393] UV light reduction at 222 and 254 nm. The photoreactor used in this example is referred to herein as 222REACTOR1. 222REACTOR1 included two cylindrical lamps, machined metal supports used to horizontally support the lamps at a distance above the horizontal plane, a photoreactor container, and a metal enclosure. The cylindrical lamps were krypton / chloride excimer lamps emitting UV radiation at approximately 222 nm. Each lamp was powered by a 20-kilovolt power supply located in a separate enclosure from the lamps, and each lamp consumed 100 watts of power. The lamps had a diameter of 54 mm and a length of 460 mm. The lamps were statically held parallel to each other at a distance of 100 mm (center-to-center) from the horizontal floor of the metal container, at a fixed distance of 57.2 mm (from the surface to the center of the cylinder) from the horizontal floor. In other possible embodiments of this photoreactor, lamps of different diameters and lengths may be used. In other possible embodiments, the machined supports of the lamps may be of different dimensions, resulting in the distance between the lamps being narrower or wider, and the distance from the horizontal floor being narrower or wider.

[0394] The reaction vessel was a cylindrical quartz vial with a diameter of 40.1 mm. The total height of the reaction vessel was 114.6 mm, of which 100 mm was of a constant diameter, and the remaining 14 mm tapered to form a threaded upper cylinder with a diameter of 12 mm. In other embodiments, the reaction vessel may have a different diameter and / or height.

[0395] The photoreactor was housed in a metal enclosure. A metal file drawer was used as the metal enclosure. Other structured enclosures, such as a structured metal enclosure, can be used as an alternative.

[0396] Seven different PFAS substances were treated in a photoreactor as described below. The PFAS substances tested included perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonic acid (PFOS).

[0397] PFAS stock solutions of seven different PFAS substances were prepared at concentrations of 2.5–10 ppm and used in this example. The PFAS stock solutions were combined with 25 mM NaHCO3 and one of various reducing solutions. A control solution without PFAS was also tested.

[0398] Five types of reducing solutions were used: 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).

[0399] The solutions were added separately to the reaction vessels, and threaded plastic caps with silicon septums were screwed onto the tops of the vials to form leak-proof seals. The reaction vessels were placed between parallel krypton / chloride lamps inside the 222 Reactor 1, so that radiation entered the vessels from both sides. Each solution was irradiated in the photoreactor at 222 nm for 3 hours. During the reaction, the reactor temperature was in the range of 55°C to 60°C.

[0400] The amount of PFAS present in the solution was measured periodically during the photoreactor process by stopping the reactor, removing samples of the reactor solution, and pipetting them into vials for storage for LC-MS analysis.

[0401] The results of the photoreaction treatment of each PFAS in each solution are shown in the graphs in Figures 40 and 41.

[0402] Figure 40 shows the concentration of PFAS as a function of time for photoreduction of PFAS in each reducing solution at 222 nm. Qualitative analysis in Figure 1 reveals that the PFAS breakdown rate is faster in iodide / sulfite-containing solutions compared to the PFAS breakdown rate under direct irradiation in pure water. It is also clear that the rate of PFAS concentration loss in the model solution, 1 mM KI, and 5 mM KI is faster than in the other solutions.

[0403] Figure 41 shows the PFAS destruction rate as a function of time for photoreduction of PFAS in each reducing solution at 222 nm. In both of these figures, the reducing solution used is indicated in the header. Figure 2 demonstrates that PFAS destruction quantitatively increases within 3 hours when the model solution is compared to all other solutions and reagent water. Furthermore, it is clear that in the model solution, the percentages of destruction of both carboxylated and sulfonated PFAS are greater than in the other solutions and are much greater than in the case of direct irradiation in reagent water.

[0404] Figure 41 also includes data for PFAS substances prepared as treatment solutions and treated as described in Example 1 above using 10 mM KI and 50 mM Na2SO3 reducing solutions. However, these solutions were irradiated at 254 nm in a separate photoreactor referred to herein as the 254REACTOR. The 254REACTOR was a LUZCHEM LZC-ORG box reactor equipped with 10 8-watt low-pressure mercury lamps. The treatment solutions were irradiated in the 254REACTOR for 3 hours. These results are shown in column 5 of Figure 41.

[0405] The selected experiments were repeated three times, and the results of these three independent experiments were averaged and plotted using statistical analysis. The results are shown in Figure 42. The results are compared with those obtained by direct irradiation of the PFAS solution at 222 nm. Examining Figure 3 reveals that in n=3 repeated tests, the time-dependent degradation rates and concentration decreases of individual PFAS compounds are statistically distinguishable in the model solution. For example, the time-dependent degradation rates of carboxylated derivatives are greater to a 68% confidence level than the degradation rates of PFHxS and PFOS, which are greater than those of PFBS. This difference is more pronounced in solutions without bicarbonates. Within the confidence limits, the degradation in the 1 mM KI / 5 mM Na2SO3 solution is also much greater than the degradation caused by direct irradiation in reagent water.

[0406] The data from this example was normalized and fitted to a single exponential function.

number

[0407] Table 7 below shows the fitting results of Equation 1 to data on time-dependent PFAS breakdown using 1 mM KI, 5 mM Na2SO3, and bicarbonate solutions. The first-order time constant τ was determined from the data plotted in columns 1, 3, 4, 5, and 6 and converted to the half-lives in Table 7. Table 7 shows the time constant versus time of PFAS breakdown using a 222 nm light source for several solutions and reagent water. 1 / 2 σ is a first-order time constant, and σ is t at a 68% confidence interval. 1 / 2 This is an error. The dashes of PFBS, PFHxS, and PFOS in the reagent water column are very high. 1 / 2 This indicates that it corresponds to a value.

[0408] [Table 7]

[0409] The half-life data plotted in Figure 42 is shown in Table 8. Table 8 shows a comparison of the time constant versus time of PFAS breakdown using a 222 nm light source for n=1 and n=4 experiments using 1 mM KI and 5 mM Na2SO3 solutions. Half-life t 1 / 2 σ is the half-life of PFAS breakdown, and σ is t at a 68% confidence interval. 1 / 2 This is the error.

[0410] [Table 8]

[0411] The exemplary fitting results shown in Figure 43, and the results for all solutions with n=1, are shown in Table 7. Figure 43 shows the fitting results of Equation 1 to data for time-dependent PFAS breakdown using 1 mM KI, 5 mM Na2SO3, and bicarbonate solutions. Within the confidence limits, the rates of the model solution are distinguishable from other solutions and reagent water.

[0412] [Example 11]

[0413] Photoreduction at 222 nm. In this example, a different 222 nm photoreactor design was used. This photoreactor, referred to herein as 222REACTOR2, included a photoreactor vessel, clamps, lamps, a transparent sleeve, a pump, and various valves and tubing.

[0414] The photoreactor container was a non-porous cylinder sealed at one end to contain the liquid. The lamp bulb was also cylindrical, with a diameter smaller than the diameter of the photoreactor container cylinder. The cylindrical lamp bulb was placed inside the cylinder (in a transparent sleeve) and fixed so that the long axis of the bulb was parallel to the long axis of the cylinder and centered on the photoreactor container cylinder. The photoreactor container cylinder included a flow control outlet near the base of the cylinder through which the discharged liquid passed. The photoreactor container cylinder also included an inlet near the top of the cylinder for adding liquid to the cylinder. A clamp held the photoreactor container cylinder with the long axis of the cylinder oriented perpendicular to a horizontal tabletop.

[0415] The photoreactor vessel cylinder was made of stainless steel, with a diameter of approximately 75 mm, a length of 500 mm, and walls approximately 3 mm thick. The inlet and outlet of the photoreactor vessel cylinder were mechanically threaded openings that could accept connections to flexible or rigid pipes. In this particular configuration, the mechanically threaded openings were 1 / 2-inch National Pipe Thread fittings made of stainless steel, welded, brazed, or soldered to the surface of the metal cylinder.

[0416] A cylindrical lamp bulb was positioned at the center of the top surface of the cylinder of the photoreactor container and inserted into a transparent sleeve parallel to the long axis of the cylinder. A stainless steel cap held and secured the sleeve. The cap included a central hole into which the sleeve was inserted and an outer cylindrical ring having an inner diameter (ID) slightly larger than the outer diameter of the stainless steel cylinder. The cap was a welded and machined stainless steel cylinder approximately 70 mm long and 100 mm in diameter. The transparent sleeve was approximately 500 mm long and 55 mm in diameter (OD), and its lower end was sealed to prevent liquid from coming into contact with the lamp. The transparent sleeve was made of quartz, which can transmit light with wavelengths of approximately 225 nm or less.

[0417] The lamp was a krypton / chloride excimer that consumed 100 watts of power and was powered by an external 20 kV power supply. The lamp bulb had a diameter of approximately 54.6 mm, a length of 460 mm, produced radiation of approximately 222 nm, and had a full width at half maximum of approximately 4 nm.

[0418] The 222REACTOR2 also included a pump connected in series with a rigid stainless steel tube between the outlet and inlet of the photoreactor vessel. A series of valves could be placed in series with the suction-side tube of the pump to stop the flow of liquid from the bottom of the reaction vessel, switching the pump suction to the vessel and drawing liquid from that vessel into the reactor. A series of valves could also be placed in series with the pressure-side of the pump to stop the flow of liquid from the pump, diverting the pump flow to an external vessel and recovering the fluid from there out of the reactor. The pump was a low-flow circulation pump of a type often used for passive or active solar heating applications. The tube consisted of 1 / 4-inch OD stainless steel tubing bent to form a sealing matrix of connections between the valves and the pump and the metal cylinder of the photoreactor.

[0419] A comparison was made between using Na2SO3 alone and using Na2SO3 and KBr. Each treatment solution contained either 10 ppm PFOA and either 5 mM Na2SO3 alone, or 5 mM Na2SO3 and 150 mM KBr. The pH reached 12 upon addition of sodium hydroxide, but none of the treatment solutions contained NaHCO3.

[0420] The reactor solutions were placed separately into photoreactor containers and irradiated at 222 nm for 24 hours in 222REACTOR2.

[0421] The amount of PFOA present in the solution was measured periodically during the photoreactor vessel treatment by removing samples from the outlet of the photoreactor vessel and storing them for LC-MS analysis. The results for the first four hours are shown in Figures 44 and 6.

[0422] Figure 44 shows data for the time-dependent breakdown of PFAS during photodegradation of PFOA using 5 mM Na2SO3 and 150 mM KBr (blue squares), and for the time-dependent defluorination of PFOA using 5 mM Na2SO3 alone (red triangles). Data are represented by symbols, and the best exponential fit is shown by a line.

[0423] Figure 45 shows the fluoride ions (F) produced from the defluorination of PFOA. - The graph shows the time dependence of the fluoride ion concentration. The blue squares show the fluoride ion concentration (symbol) versus time using 5 mM Na2SO3 and 150 mM KBR, with the blue line indicating the best exponential fit. The red triangles show the fluoride ion concentration versus time using 5 mM Na2SO3 only, with the red line indicating the best exponential fit.

[0424] These results indicate that the reactor solution containing bromide resulted in faster and more complete defluorination than the reactor solution containing only Na2SO3.

[0425] In Example 10, it is noteworthy that there was essentially no statistically significant difference in decay rates between the 10mM KBr / 50mM Na2SO3 solution and the 50mM Na2SO3 solution without KBr. However, in Example 10, which contained higher levels of KBr (and lower levels of sulfites), the inclusion of KBr had a clear positive effect on PFOA breakdown.

[0426] The molar absorptivity of sulfite at 222 nm is 70 times greater than that of KBr (77.61 M). -1 cm -1 Compared to [Birkmann et al, Water Practice and Technology (2018) 13(4); 879-892], the value for sulfites is 5400M. -1 cm -1 [Internal experiment] Considering this, it is thought that in Example 1, sulfite absorbed most of the light. In contrast, in Example 2, when sulfite was reduced and bromide was increased, KBr was effective in improving PFOA breakdown. Assuming that the yields are equivalent for KBr and KI, the relative quantum efficiency of photogenerated electrons at this wavelength is unknown, but if the concentration of KBr is increased 147 times relative to the concentration of KI (77.61M for KBr) -1 cm -1 In comparison, ε = 11,527M in KI -1 cm -1 [Birkmann et al, Water Practice and Technology (2018) 13(4); 879-892]), similar effects may be achievable. ε is the molar extinction coefficient.

[0427] Similarly in Example 10, no significant difference in PFAS breakdown rates was observed when comparing a 10 mM KI / 50 mM Na2SO3 solution with a 50 mM Na2SO3 solution. In fact, adding KI may slightly decrease the rate. Therefore, it is reasonable to study the rate of PFAS breakdown with respect to the concentration of a solution containing only Na2SO3 in more detail. A direct comparison of the breakdown rates between a 5 mM Na2SO3 solution and the model solution should clearly show whether 1 mM KI is relevant at this concentration. Furthermore, calculations have shown that concentrations of KI and Na2SO3 up to three orders of magnitude lower than those in the model solution are required for light to penetrate at least 1 cm into the reactor cell at 222 nm. Recognizing the important inverse correlation between light transmission and the concentration of left-out electrons in the solution required for PFAS breakdown, concentrations of KI, Br, and Na2SO3 in the tens to hundreds of μM range may affect the PFAS breakdown rate.

[0428] [Example 12]

[0429] UV photoreduction at 222 and 254 nm. Further experiments were conducted to evaluate the disruption of PFAS foam separation using UV irradiation at 222 nm and 254 nm.

[0430] Foam separatory water was obtained from the Minnesota Pollution Control Agency (MPCA). The major compounds in the MPCA sample were determined to be PFOA and PFOS. Other compounds (PFHxA, PFHxS, PFHpS) were detected at concentrations below the limit of quantification. For a 5-fold dilution of the sample for LC-MS analysis, the limit of quantification (LOQ) for analysis was calculated to be approximately 10 ppb for each compound in the fractionated sample.

[0431] 222 nm radiation was delivered using 222REACTOR1. The reagents used with the 222 nm radiation included 1 mM potassium iodide (KI) and 5 mM sodium sulfite (Na2SO3). A 5-fold diluted sample was placed in 222Reactor1 and irradiated under 222 nm UV light for 5 hours.

[0432] 254 nm radiation was delivered using a 254 REACTOR. The reactor solution used with the 254 nm radiation contained 40 mM potassium iodide (KI) and 200 mM sodium sulfite (Na2SO3). A 5-fold diluted sample was placed in the 254 Reactor and irradiated under 254 nm UV light for 6 hours.

[0433] For each reactor, the amount of PFAS present in the solution was periodically measured during the photoreactor vessel processing by stopping the reactor, removing the sample from the reaction vessel, and pipetting it into vials for storage for LC-MS analysis.

[0434] The results are shown in Figure 46, which shows the percentage of PFAS breakdown over time (top row) and the PFAS concentration over time (bottom row) for both 222 nm (left) and 254 nm treatments. The 5-fold diluted sample reached a degree of complete breakdown (approximately 99%) by 5 hours under 222 nm UV and by 6 hours under 254 nm UV. Other compounds (PFHxA, PFHxS, PFHpS) also showed concentrations below the limit of quantification at this point.

[0435] The results demonstrate that PFAS destruction is similar between the two experiments. However, the 222 nm treatment achieved these results using significantly lower iodide and sulfite concentrations (1 / 40) than the 254 nm treatment. This is particularly important with respect to iodine due to its very high cost compared to other reagents. Therefore, equivalent or better destruction performance in the 222 nm system under significantly reduced iodide concentrations, and thus a corresponding reduction in cost, represents a significant step towards the development of effective and economical means of PFAS destruction. This cost reduction is particularly important in large-scale processes from the standpoint of efficiency and reduction of operating costs.

[0436] [Example 13]

[0437] The following photoreactor and experimental design were used in Examples 13, 14, and 15. The photoreactor included a Pyrex cylindrical beaker (84 mm in diameter, 124 mm in height, 600 ml total capacity), a rubber stopper with a tapered end and a diameter of 84 mm at half its height, two quartz sleeves (Technical Glass, GE214) sealed at one end and 23 mm in diameter and 190 mm in length, and two 15-watt ultraviolet bulbs. Depending on the experiment, two distinctly different types of ultraviolet bulbs were used interchangeably within the reactor: 1) a UV222 nm excimer bulb with a diameter of 23 mm and a length of 190 mm, and 2) a UV185 / 254 nm bulb with a diameter of 19 mm and a length of 200 mm.

[0438] The rubber stopper had two 23mm diameter holes cut along its diameter, 16mm from the center of the stopper, and similarly, four smaller holes (2×6.3mm, 2×7.6mm) arranged in a 60mm square pattern, the center of which coincided with the center of the stopper. If a salt bridge was used, an additional 1cm hole was present in the stopper to accommodate it. The quartz sleeve was fitted into the 23mm hole, protruding through the stopper so that the sealed end of the sleeve protruded more than 75mm beyond the lower flat surface of the tapered plug. The rubber stopper was fitted tightly into the beaker so that the quartz sleeve protruded into the beaker. A UV bulb was placed inside the quartz sleeve through the opening (upper end) of these sleeves protruding into the beaker. The beaker (with stirring rod) was placed on a stirring plate. The smaller diameter holes present in the reactor are ports for probes, electrodes, and sparging lines in the experiment described below.

[0439] Photodestruction was performed by decanting a 450 ml sample PFAS solution into a 600 ml beaker. Argon was blown into the solution for 15 minutes, stirred, and then the lamp was turned on (time 0). Samples were taken at regular time intervals during the photodestruction process. These samples were analyzed with a fluoride sensor to detect the release of free fluoride ions from the destruction of PFAS.

[0440] Electrochemical reduction of iodine. In this example, the recycling of iodide without the use of sulfites was tested by electrochemical reduction of photochemically generated iodine radicals.

[0441] A 450 ml solution containing 5 ppm perfluorooctanesulfonic 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 (1 M KCl) salt bridge was inserted into the reactor solution through a stopper. The other end of the salt bridge was placed in a stirred 1 M KCl aqueous solution containing a 2 × 2 cm platinum mesh counter electrode, which would function as the anode throughout the experiment. A 2 × 2 cm platinum mesh working electrode and an Ag / AgCl reference electrode were suspended in the reactor cell solution. A potentiostat (BioLogic) was used to apply a potential of -0.7 V relative to Ag / AgCl to the working electrode. The platinum working electrode functioned as the cathode, reducing oxidized iodine radicals to iodide. Argon was blown into the solution before and during the PFOS destruction experiment. The working electrode was positioned approximately 2 cm from the quartz sleeve housing the lamp. Time 0 in the PFOS destruction experiment was the moment the lamp was switched on. A UV 222nm light bulb was used in this experiment. The transmittance of the quartz sleeve at 222nm was 0.8. Samples were taken at regular time intervals through the access port of the rubber stopper with a sampling error of + / - 30 seconds.

[0442] The results are shown in the graph in Figure 47. Figure 47 is a graph of the percentage of free fluoride against the theoretical maximum value as a function of time for the destruction of 5 ppm PFOS mentioned above. The percentage of free fluoride is for the solution with a potential of -0.7 V applied to the electrode relative to Ag / AgCl (black square). No potential was applied to the control electrode (gray circle). Error bars are drawn at a 95% confidence level. After 120 minutes, only 3% defluorination was achieved in the control experiment without potential application, while 18% defluorination was achieved in the electrochemical experiment after 120 minutes. This demonstrates the ability of the electrochemical system to regenerate iodide during the photoreduction experiment, achieving effective PFAS destruction with no or minimal sulfite.

[0443] [Example 14]

[0444] Destruction of perfluorooctanesulfonic acid (PFOS) using electrochemical generation of hydrogen. In this example, hydroxyl radicals were generated using 185 nm light. These hydroxyl radicals react with electrochemically generated molecular hydrogen to ultimately form solvated electrons used for the reductive destruction of PFOS. Herein, as part of this example, three experiments are shown: 14(a) a control destruction experiment using 185 nm radiation on a reactor solution of PFOS, sodium sulfate, and sodium hydroxide, but without voltage applied to the electrodes; 14(b) a destruction experiment performed using 185 nm radiation on both the anode and cathode present in the reactor cell on a reactor solution of PFOS, sodium sulfate, and sodium hydroxide; and 14(c) a destruction experiment performed using 185 nm radiation on the cathode in the reactor cell and the anode isolated in a separate cell on a reactor solution of PFOS, sodium sulfate, and sodium hydroxide. The anode and cathode cells were connected by a salt bridge.

[0445] In Examples 14(a)–14(c), the start point (time 0) of the PFOS destruction experiment was when the lamp was switched on. During the experiment, argon was blown into the reactor solution. The blowing began 15 minutes before the start of the experiment. The reactor solution was constantly stirred throughout the experiment. A UV 185 / 254 nm bulb was used in this experiment. The transmittance of the quartz sleeve at 185 nm was 0.63. Samples were taken through the access port of the rubber stopper at regular time intervals with a sampling error of + / - 30 seconds.

[0446] In 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 in a photoreactor. This experiment served as a control. No voltage was applied to the cell. UV light was lit in the photoreactor during this experiment.

[0447] In 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 × 10 cm platinum-coated Ti mesh electrodes were square and bent to match the diameter of the reactor beaker), as well as the reference electrode (Ag / AgCl), were suspended in the reaction cell solution. A potential of -1.1 V relative to Ag / AgCl was applied to the working electrode, which acted as the cathode. This applied potential was higher than the potential required to electrolyze water to molecular hydrogen at the cathode and to molecular oxygen at the anode. The electrodes were positioned approximately 2 cm from the quartz sleeve of the reactor housing the lamp.

[0448] In 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. The working electrode (a 10 × 10 cm platinum-coated Ti mesh electrode, square in shape and bent to match the diameter of the reactor beaker) was suspended in the photoreactor solution. One end of a (1 M sodium sulfate) salt bridge was inserted into the reactor solution through a stopper. The other end of the salt bridge was placed in a beaker of stirred 1 M sodium sulfite aqueous solution containing a platinum mesh counter electrode identical to the working electrode. This electrode functioned as the anode throughout the experiment. The counter electrode oxidized sulfite to sulfate at the electrode interface. The salt bridge ensured charge neutrality between the anode and the cathode cell. The working electrode was positioned approximately 2 cm from the quartz sleeve of the reactor housing the lamp. During the destructive test, a voltage of 58.13 volts was applied between the electrodes, and a current of 49 mA was applied at the start of the experiment and 86 mA at the end of the experiment after 2 hours. After applying the initial current for 5 minutes, visible hydrogen bubbles could be observed forming on the platinum mesh electrode.

[0449] The results of Example 14 are shown in the plot in Figure 48. This figure plots the percentage of free fluoride produced against the theoretical maximum value as a function of time for the breakdown of 5 ppm PFOS described for Examples 14(a) to 14(c). Error bars are drawn at a 95% confidence level. The results of Example 14(a), a control experiment, are plotted as gray circles. After 120 minutes, only about 10% defluorination was achieved in this control experiment. The results of Example 14(b) are plotted as gray squares, where both the anode and cathode were present in the photoreactor. In this experiment, virtually no defluorination was achieved after 2 hours. This may be due to oxygen present in the reactor cell due to the photolysis of water. Oxygen is a strong quencher of solvated electrons. The results of Example 14(c) are plotted as black squares. In this experiment, the anode and cathode were present in different cells connected by a salt bridge. In this experiment, 35% defluorination was achieved after 120 minutes. This experiment demonstrates that effective PFOS decomposition can be achieved without the addition of chemical photosensitizers by utilizing in-situ electrochemical hydrogen generation.

[0450] [Example 15]

[0451] Synthesis of Iodide Recovery Electrode. An iodide recovery 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 and operated at 1200 rpm for 60 minutes. The resulting powder was then mixed with 5 mL of 60% PTFE solution using a mortar and pestle. This yielded a flexible putty-like material, which was repeatedly folded to create uniformity and structural integrity. The material was then dried in an 800°C oven for 6 hours to remove water from the structure. This resulted in a rigid yet flexible sheet. A 2 x 2 cm square was cut from the sheet and attached to a conductive carbon paper current collector using conductive carbon paint. The carbon paper was then masked with Teflon® tape and lacquer so that only the iodide recovery material was exposed to the solution during the operation.

[0452] [Example 16]

[0453] Iodide recovery using electrodes. A 0.1 M Na3PO4, pH 7 solution was prepared for use in a three-electrode cell where the working electrode was the iodide recovery 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 shown in graph a of Figure 49, and reduced LSV was performed as shown in graph b of Figure 49.

[0454] Next, potassium iodide was added to the solution to make it 50 mM KI. The same oxidation LSV was performed as shown in graph a. The significantly high current generated in the 50 mM KI solution indicates that oxidation of the iodide is occurring. Then, constant current electrolysis was performed at 0.25 mA / cm². 2 The procedure was performed. After 40 minutes, a yellow color was observed in the solution near the working electrode, which indicates that the electrode was I3 - This indicates complete saturation. Next, a new 0.1 M Na3PO4, pH 7 solution was prepared and the same reducing LSV was performed as shown in graph b.

[0455] In graph a, the oxidative LSV of the iodide recovery electrode in 0.1 M Na3PO4, pH 7 is shown for no iodide (solid line) and with 50 mM KI (dashed line). In graph b, the reduced LSV of the iodide recovery electrode is shown for 0.1 M Na3PO4, pH 7 (solid line) and after loading with I3- (dashed line). The much higher current, with the peak centered at -1.1 V relative to Ag / AgCl, is due to I3- immobilized in the electrode. - This may be due to reduction. Next, constant current electrolysis is performed at -0.25 mA / cm². 2 Perform this for 40 minutes, I3 - to I - It was converted to [a specific substance] and released into the solution. The resulting solution contained 0.44 mM iodide.

[0456] [Example 17]

[0457] Iodide recovery using electrodes. Four cycles of iodide capture and discharge were performed using the iodide recovery electrode described in Example 14. The iodide capture medium was 100 mL of 0.1 M Na3PO4, 2 mM KI, pH 7 solution. For iodide capture, a three-electrode non-divided cell was used, with the working electrode being the iodide recovery electrode described in Example 13, the counter electrode being a Pt mesh, and the reference electrode being Ag / AgCl. The iodide capture process was performed using constant current electrolysis at 0.25 mA / cm². 2 The procedure was carried out for 30 minutes. After each iodide capture step, the electrodes were thoroughly rinsed with DI water, dried, and prepared for the iodide recovery step. The iodide recovery medium was 100 mL of 0.1 M Na3PO4, pH 7 solution. For iodide recovery, a three-electrode cell divided by a Nafion 212 cation exchange membrane was used, with the working electrode being the iodide recovery electrode described in Example 13, the counter electrode being a Pt mesh, and the reference electrode being Ag / AgCl. The iodide recovery step was performed using constant current electrolysis at -0.25 mA / cm². 2 The procedure was carried out for 30 minutes. After each iodide recovery step, the electrodes were thoroughly rinsed with DI water, dried, and prepared for the iodide capture and recovery step.

[0458] Figure 50 shows the removal and recovery of iodide after the second and fourth cycles, which shows the total iodide removed (circles) and recovered (squares) from the 0.1 M Na3PO4, 2 mM KI, pH 7 solution after two and four iodide capture and release cycles. After two cycles, with an efficiency of 53%, 5.5% of the initial iodide was removed from the iodide capture solution and 2.9% of the initial iodide was recovered in the recovery solution. After four cycles, with an efficiency of 53%, a total of 10.3% of the initial iodide was removed from the iodide capture solution and 5.4% of the initial iodide was recovered in the recovery solution.

[0459] [Example 18]

[0460] Iodide recovery using anion exchange resin. 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 the form of beads approximately 2 mm in diameter were placed in a bottle. 300 mL of the solution and 0.5 g of commercially available AmberLite anion exchange resin in the form of beads approximately 2 mm in diameter were placed in a separate bottle. Both bottles were shaken for 24 hours to mix the solution and resin together. After 24 hours, the solution containing AmberSep contained 0.94 mM iodide, meaning that 53% of the iodide was removed. After 24 hours, the solution containing AmberLite contained 0.62 mM iodide, meaning that 69% of the iodide was removed.

[0461] The iodide-loaded resins were filtered from the solution and rinsed with DI water. They were then placed into separate bottles, each containing 50 mL of 0.2 M KCl. The two bottles were shaken for 24 hours to mix the solution and resin together. After 24 hours, the solution containing AmberSep contained 2.0 mM iodide, meaning 17% of the initial iodide was recovered. The solution containing AmberLite contained 1.91 mM iodide, meaning 16% of the initial iodide was recovered.

[0462] As used herein, the terms “substantially” or “generally” refer to the degree or extent of complete or near-completeness of an action, feature, characteristic, state, structure, item, or result. For example, an object included “substantially” or “generally” means that the object is either included completely or nearly completely. The exact acceptable degree of deviation from absolute completeness may, in some cases, depend on the specific circumstances. However, proximity to completion generally results in the same overall outcome as if absolute and complete completion had been achieved. The use of “substantially” or “generally” is equally applicable when used in a negative sense to refer to the complete or near-complete absence of an action, feature, characteristic, state, structure, item, or result. For example, an element, combination, embodiment, or composition that “substantially” or “generally” does not include an element may still actually include such an element, insofar as it does not have a significant effect.

[0463] The above description has illustrated the present invention with reference to specific embodiments. However, it will be understood that various modifications and changes can be made without departing from the scope of the invention.

Claims

1. Removing nitrates from water containing PFAS, To prepare a treatment solution having a pH of approximately 10 or higher by combining water containing PFAS with a sensitizer and a sufficient amount of base, The process involves irradiating the processing solution with UV light inside the photoreactor to destroy a portion of the PFAS. A method of PFAS destruction, including the method described above.

2. The method according to claim 1, wherein removing nitrates from the water containing PFAS includes electrolytic removal of nitrates from the water containing PFAS.

3. The method according to claim 2, wherein the electrolytic removal of the nitrate includes electrolytically reducing the nitrate to nitrogen gas and / or ammonia.

4. The method according to claim 2, wherein the electrolytic removal of nitrates from water containing PFAS comprises bringing water containing PFAS into contact with an electrode and applying an electric current to the electrode.

5. The method according to claim 4, wherein the electrode includes an iron, copper, or iron:copper electrode.

6. The method according to claim 4, wherein the electrode includes a cathode of an electrolytic cell system, and the electrolytic cell system further includes an anode in an aqueous electrolyte.

7. The method according to claim 6, further comprising forming oxygen gas at the anode while reducing nitrate at the cathode.

8. The method according to claim 12, wherein the removal of nitrates from the water containing the PFAS includes filtration by a selective membrane.

9. The method according to claim 8, wherein the filtration by the selected membrane includes reverse osmosis, forward osmosis, nanofiltration (NF), and / or ultrafiltration (UF).

10. The method according to claim 1, wherein the removal of nitrates from the water containing the PFAS is a pretreatment step before irradiating the treatment solution.

11. The method according to claim 1, further comprising the step of removing nitrates from the water containing the PFAS, which is performed within the photoreactor.

12. Bringing water containing PFAS into contact with the cathode, Applying an electric current to the cathode to electrolytically reduce nitrates in water containing PFAS, To prepare a treatment solution with a pH of approximately 10 or higher by combining water containing PFAS with sulfites, halides, and a sufficient amount of base, By irradiating the processing solution with UV light inside the photoreactor, a portion of the PFAS is destroyed. A method of PFAS destruction, including the method described above.

13. The method according to claim 12, wherein the halide salt contains iodide and the UV light contains light having an emission peak at approximately 222 nm.

14. The method according to claim 13, further comprising oxidatively pre-treating water containing PFAS before irradiating the PFAS.

15. The method according to claim 14, wherein the oxidative pretreatment of the water containing PFAS includes mixing the water containing PFAS with a persulfate and an acid or base, and then exposing the water to an increased temperature and increased pressure.

16. A system for destroying PFAS in water, said system A nitrate removal system configured to remove nitrates from water containing PFAS and nitrates, comprising a selective membrane and / or an electrolytic cell system, Photoreactor and The photoreactor includes, A reaction vessel configured to contain an aqueous solution, An ultraviolet light source positioned to direct light towards the contents of the reaction vessel, A system for destroying PFAS in water, including [specific component].

17. The system according to claim 16, wherein the nitrate removal system is located upstream of the photoreactor.

18. The nitrate removal system described above is A first cell comprising a cathode configured to come into contact with water containing PFAS within the first cell, A second cell containing an anode in an electrolyte, Power supply and Saltwater and / or membrane for separating the first and second cells The system according to claim 16, which is an electrolytic cell system including

19. The system according to claim 19, wherein the cathode is arranged in the photoreactor and the photoreactor container forms the container of the first cell.

20. The system according to claim 18, wherein the cathode comprises iron, copper and / or iron:copper.

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