Divided electrochemical cell configurations for electrochemical PFAS destruction

Abstract

Systems and methods for the reduction and / or destruction of one or more per- or polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system. The systems and methods may include an electrochemical cell having an anolyte compartment, wherein the anolyte compartment includes at least one anode, a catholyte compartment, wherein the catholyte compartment includes at least one cathode, and an ion exchange membrane separating the anolyte compartment and the catholyte compartment, wherein at least one of the anolyte compartment and the catholyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds.

Description

DIVIDED ELECTROCHEMICAL CELL CONFIGURATIONS FOR ELECTROCHEMICAL PFAS DESTRUCTIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 571,593, filed March 29, 2024 and titled “Divided Electrochemical Cell Configurations for Electrochemical PFAS Destruction”, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTIONField of the Invention

[0002] The invention relates, in general, to a system and configuration for the destruction of one or more per- or polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system. In another embodiment, the present invention relates to electrochemical cells designed to destroy, mitigate, and / or reduce one or more polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system.Description of the Related Art

[0003] There is rising concern about the presence of various contaminants in municipal wastewater, surface water, drinking water and groundwater. For example, perchlorate ions in water are of concern, as well as PFAS and PFAS precursors, along with a general concern with respect to total organic carbon (TOC).

[0004] As is well known, PFAS are man-made chemicals that are used in numerous industries. Since PFAS molecules typically do not break down naturally, PFAS molecules accumulate in the environment and within various organic lifeforms such as humans. Additionally, PFAS molecules contaminate food products, commercial household and workplace products, municipal water, agricultural soil and irrigation water, and even drinking water. PFAS molecules have been shown to cause adverse health effects in humans and animals.

[0005] As is known, PFAS are organic compounds consisting of fluorine, carbon and heteroatoms such as oxygen, nitrogen and sulfur. PFAS is a broad class of molecules that furtherincludes polyfluoroalkyl substances. PFAS are carbon chain molecules having carbon-fluorine bonds. Polyfluoroalkyl substances are carbon chain molecules having carbon-fluorine bonds and also carbon-hydrogen bonds. Common PFAS molecules include perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and short-chain organofluorine chemical compounds, such as the ammonium salt of hexafluoropropylene oxide dimer acid (HFPO-DA) fluoride (also known as GenX). PFAS molecules typically have a tail with a hydrophobic end and an ionized end. The hydrophobicity of fluorocarbons and extreme electronegativity of fluorine give these and similar compounds unusual properties. Initially, many of these compounds were used as gases in the fabrication of integrated circuits. The ozone destroying properties of these molecules restricted their use and resulted in methods to prevent their release into the atmosphere. But other PFAS such as fluoro- surfactants have become increasingly popular. PFAS are commonly use as surface treatment / coatings in consumer products such as carpets, upholstery, stain resistant apparel, cookware, paper, packaging, and the like, and may also be found in chemicals used for chemical plating, electrolytes, lubricants, and the like, which may eventually end up in the water supply.

[0006] Further, PFAS have been utilized as key ingredients in aqueous film forming foams (AFFFs). AFFFs have been the product of choice for firefighting at military and municipal fire training sites around the world. AFFFs have also been used extensively at oil and gas refineries for both fire training and firefighting exercises. AFFFs work by blanketing spilled oil / fuel, cooling the surface, and preventing re-ignition. PFAS in AFFFs have contaminated the groundwater at many of these sites and refineries, including more than 100 U.S. Air Force sites.

[0007] In light of the various health impacts of PF As molecules, the U.S. Environmental Protection Agency (EP A) has issued a Contaminant Candidate List (CCL 5) which includes PFAS as a broad class inclusive of any PFAS that fits the revised CCL 5 structural definition of per- and polyfluoroalkyl substances (PFAS), namely chemicals that contain at least one of the following three structures: (i) R-(CF2)-CF(R')R", where both the CF2 and CF moieties are saturated carbons, and none of R, R', and R" are hydrogen, (ii) R-CF2OCF2-R', where both the CF2 moieties are saturated carbons, and none of R and R' are hydrogen; and (iii) CF3C(CF3)RR', where all the carbons are saturated, and none of R and R' are hydrogen.

[0008] The EPA's Comptox Database includes a CCL 5 PFAS list of over 10,000 PFAS substances that meet the Final CCL 5 PFAS definition. The EPA has committed to being proactiveas emerging PFAS contaminants or contaminant groups continue to be identified and the term PFAS as used herein is intended to be all inclusive in this regard.

[0009] Although used in relatively small amounts, PFAS compounds are readily released into the environment where their extreme hydrophobicity as well as negligible rates of natural decomposition results in environmental persistence and bioaccumulation. It appears as if even low levels of bioaccumulation of PFASs may lead to serious health consequences for contaminated animals such as human beings, the young being especially susceptible. The environmental effects of these compounds on plants and microbes are as yet largely unknown. Nevertheless, serious efforts to limit the environmental release of PFAS are now commencing.

[0010] Given the current atmosphere surrounding PFASs, it has become desirable to have flexibility in terms of what type of approach is used for treating water containing PFAS. For example, the source and / or constituents of the process water to be treated may be a relevant factor. The properties of PFAS compounds may vary widely, for example between long chain, short chain and ultrashort chain PFAS compounds. Various federal, state and / or municipal regulations may also be factors. The U.S. Environmental Protection Agency (EP A) developed revised guidelines in May 2016 of a combined lifetime exposure of 70 parts per trillion (ppt) for PFOS and PFOA. In June 2022, this EPA guidance was tightened to a recommendation of 0.004 ppt lifetime exposure for PFOA and 0.02 ppt lifetime exposure for PFOS. Federal, state, and / or private bodies may also issue relevant regulations. Market conditions may also be a controlling factor. These factors may be variable and therefore a preferred water treatment approach may change over time.

[0011] Use of various adsorption media is one technique for treating water containing PFAS. Activated carbon and ion exchange resin are both examples of adsorption media that may be used to capture PFAS from water to be treated. Such techniques may be used alone or in conjunction.

[0012] While conventional activated carbon adsorption systems and methods to remove PFAS from water have shown to be effective on the longer alkyl chain PFAS, such methods have reduced bed lives when treating shorter alkyl chain compounds. Activated carbon treated with a surfactant can help increase bed life and some conventional anion selective exchange resins have shown to be effective on the longer alkyl chain PFAS but also have reduced bed lives when treating shorter alkyl chain compounds.

[0013] Additionally, membrane processes such as nano-filtration and reverse osmosis have been used for PFAS removal. Normal oxidative processes have heretofore been unsuccessful in oxidizing PFAS. Even ozone has been reported to be an ineffective oxidant. Further, there have been reports of PFAS moi eties being destroyed by combined oxidative technologies such as ozone plus UV or use of specialized anodes to selectively oxidize PFAS.

[0014] Accordingly, there is a need in the art for a more effective and efficient method to achieve the destruction and / or remediation of PFAS in various effluent streams, water supplies, and / or other aqueous systems. As such, the present invention relates to a system configuration for the enhancement of PFAS destruction via electrochemical oxidation (EOX).SUMMARY OF THE INVENTION

[0015] The invention relates, in general, to a system and configuration for the destruction of one or more polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system. In another embodiment, the present invention relates to electrochemical cells designed to destroy, mitigate, and / or reduce one or more polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system.

[0016] According to one aspect, the present invention is directed to a system comprising: (a) an influent fluid, comprised by at least one PFAS species; (b) a reactant delivery device; (c) an electrochemical oxidation device; and (d) an effluent.

[0017] In another instance, the present invention is directed to a method of operating such a system, where the method comprises: (i) introducing oxygen to an influent fluid via a reactant delivery device; (ii) delivering the influent fluid to an electrochemical oxidation device; (iii) reducing a concentration of at least one PFAS species via electrochemical oxidation in the electrochemical oxidation device; and (iv) producing an effluent having a lower concentration of the at least one PFAS species relative to the influent. In one embodiment, the method of this embodiment utilizes a fluid velocity of between about 0.1 m / s and about 10 m / s in the electrochemical oxidation device.

[0018] In another embodiment, the present invention is directed to an electrochemical cell for reducing, mitigating, and / or eliminating one or more of the one or more PFAS compounds,where such an electrochemical cell has split architecture with an ion exchange membrane separating an anode compartment and a cathode compartment.

[0019] In still another embodiment, the present invention is directed to an electrochemical cell for reducing, mitigating, and / or eliminating one or more of the one or more PFAS compounds, where such an electrochemical cell has split architecture with a salt bridge.

[0020] Clause 1 : An electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and an ion exchange membrane separating the anolyte compartment and the catholyte compartment, wherein at least one of the anolyte compartment and the catholyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds.

[0021] Clause 2: The electrochemical cell of clause 1, wherein the ion exchange membrane is a cation exchange membrane.

[0022] Clause 3: The electrochemical cell of clause 1, wherein the at least one anode is a niobium-based boron-doped diamond (BDD) anode.

[0023] Clause 4: The electrochemical cell of clause 1, wherein the at least one cathode is a titanium cathode.

[0024] Clause 5: The electrochemical cell of clause 1, wherein the at least one cathode is a platinum-coated titanium cathode.

[0025] Clause 6: The electrochemical cell of clause 1, wherein the at least one influent fluid containing one or more PFAS compounds further comprises a sodium sulfate solution.

[0026] Clause 7: The electrochemical cell of clause 1, wherein the ion exchange membrane is positioned within a channel separating the anolyte compartment and the catholyte compartment.

[0027] Clause 8: The electrochemical cell of claim 1, wherein the at least one anode and the at least one cathode are coupled to at least one power source.

[0028] Clause 9: A method of operating an electrochemical cell for PFAS remediation, the method comprising: supplying an electrochemical cell, the electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and an ion exchange membrane separating the anolyte compartment and the catholyte compartment;supplying an influent fluid to at least one of the anolyte compartment and the catholyte compartment of the electrochemical cell, wherein the influent fluid comprises one or more PFAS compounds; and conducting electrochemical oxidation of the one or more PFAS compounds in order to reduce, mitigate, and / or eliminate one or more of the one or more PFAS compounds.

[0029] Clause 10: The method of clause 9, further comprising adding a sodium sulfate solution to the influent fluid to control the conductivity of the influent fluid.

[0030] Clause 11 : The method of clause 9, wherein the ion exchange membrane is a cation exchange membrane.

[0031] Clause 12: The method of clause 9, wherein the at least one anode is a niobium- based boron-doped diamond (BDD) anode.

[0032] Clause 13: The method of clause 9, wherein the at least one cathode is a titanium cathode.

[0033] Clause 14: The method of clause 9, wherein the at least one cathode is a platinum- coated titanium cathode.

[0034] Clause 15: An electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and a salt bridge connecting the two compartments, wherein at least the anolyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds.

[0035] Clause 16: The electrochemical cell of clause 15, wherein the electrochemical cell is designed to operate with an influent fluid velocity of between about 0.01 m / s to about 10 m / s.

[0036] Clause 17: The electrochemical cell of any of clauses 15 or 16, wherein the electrochemical cell is configured to operate with a PFAS initial content in the range of about 0.5 ppb to about 50,000,000 ppb.

[0037] Clause 18: The electrochemical cell of any of clauses 15-17, wherein the electrochemical cell utilizes a current density in the range between about 10 A / m2and about 5,000 A / m2.

[0038] Clause 19: The electrochemical cell of any of clauses 15-18, wherein electrochemical cell utilizes a voltage in the range of about 0. IV to about 10V.

[0039] Clause 20: The electrochemical cell of any of clauses 15-19, wherein electrochemical cell utilizes a dissolved oxygen content in the range of about 0.5 bar to about 10 bar.

[0040] Clause 21 : The electrochemical cell of any of clauses 15-20, wherein the influent fluid has a TDS value in the range of about 300 to about 200,000 mg / L.

[0041] Clause 22: The electrochemical cell of any of clauses 15-21, wherein the electrochemical cell utilizes at least one catalyst.

[0042] Clause 23: The electrochemical cell of any of clauses 15-22, wherein the electrochemical cell utilizes a pulsed waveform.

[0043] Clause 24: The electrochemical cell of any of clauses 15-23, wherein foaming is controlled in the electrochemical cell via one or more of the addition of oxygen and / or by increasing the partial pressure of the system such that the gas remains entrained in solution.

[0044] Clause 25: A method of operating a electrochemical cell for PFAS remediation, the method comprising: supplying an electrochemical cell, the electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and a salt bridge connecting the two compartments, wherein at least the anolyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds; supplying an influent fluid to the anolyte compartment of the electrochemical cell, wherein the influent fluid comprises one or more PFAS compounds; and conducting anodic electrochemical oxidation of the one or more PFAS compounds in order to reduce, mitigate, and / or eliminate one or more of the one or more PFAS compounds.

[0045] Clause 26: The method of clause 25, wherein the electrochemical cell is designed to operate with an influent fluid velocity of between about 0.01 m / s to about 10 m / s.

[0046] Clause 27: The method of any of clauses 25 or 26, wherein the electrochemical cell is configured to operate with a PFAS initial content in the range of about 0.5 ppb to about 50,000,000 ppb.

[0047] Clause 28: The method of any of clauses 25-27, wherein the electrochemical cell utilizes a current density in the range between about 10 A / m2and about 5,000 A / m2.

[0048] Clause 29: The method of any of clauses 25-28, wherein electrochemical cell utilizes a voltage in the range of about 0. IV to about 10V.

[0049] Clause 30: The method of any of clauses 25-29, wherein electrochemical cell utilizes a dissolved oxygen content in the range of about 0.5 bar to about 10 bar.

[0050] Clause 31 : The method of any of clauses 25-30, wherein the influent fluid has a TDS value in the range of about 300 to about 200,000 mg / L.

[0051] Clause 32: The method of any of clauses 25-31, wherein the electrochemical cell utilizes at least one catalyst.

[0052] Clause 33: The method of any of clauses 25-32, wherein the electrochemical cell utilizes a pulsed waveform.

[0053] Clause 34: The method of any of clauses 25-33, wherein foaming is controlled in the electrochemical cell via one or more of the addition of oxygen and / or by increasing the partial pressure of the system such that the gas remains entrained in solution.BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is cross-sectional view of an exemplary open channel electrochemical cell according to one embodiment of the present invention;

[0055] Figure 2 is a set of graphs illustrating the solubility of oxygen and hydrogen in fresh and salt water under various temperatures and pressures;

[0056] Figure 3 is a schematic illustration of an embodiment of a PFAS-mitigation, or destruction, system of the present invention;

[0057] Figure 4 is a schematic illustration of another embodiment of a PFAS-mitigation, or destruction, system in accordance with one embodiment of the present invention;

[0058] Figure 5A is an IV-curve of the system operating at a certain set of parameters, according to one embodiment;

[0059] Figure 5B is an IV-curve of the system operating at a certain set of parameters, according to another embodiment;

[0060] Figure 5C is an IV-curve of the system operating at a certain set of parameters, according to another embodiment;

[0061] Figure 5D is an IV-curve of the system operating at a certain set of parameters, according to yet another embodiment;

[0062] Figure 6 is a graph illustrating the destruction of PFOA via electrochemical oxidation according to one embodiment of the present invention;

[0063] Figure 7A is a schematic illustration of a portion of one embodiment of an electrochemical cell;

[0064] Figure 7B is a schematic illustration of a portion of another embodiment of an electrochemical cell;

[0065] Figure 8A is a schematic illustration of one embodiment of another electrochemical cell;

[0066] Figure 8B is a schematic illustration of one embodiment of another electrochemical cell; and

[0067] Figures 9A-9C are schematic illustrations of various electrochemical cell arrangements.DESCRIPTION OF THE INVENTION

[0068] The following description is provided to enable those skilled in the art to make and use the described embodiments contemplated for carrying out the invention. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present invention.

[0069] The invention relates, in general, to a system and configuration for the destruction of one or more polyfluoroalkyl substances (PF AS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system. In another embodiment, the present invention relates to electrochemical cells designed to destroy, mitigate, and / or reduce one or more polyfluoroalkyl substances (PFAS) and / or one or more PFAS precursors via an electrochemical oxidation (EOX) system.

[0070] Electrochemical oxidation (EOX) is a technology that can be utilized for the direct destruction of PFAS at the surface of an anodic electrode. In brief, PFAS molecules adhere to the surface of the electrode and are then degraded through the direct transfer of electrons. Further degradation can occur via solution mediated processes that result from the electrochemical generation of reactive oxidative species such as ozone, hydrogen peroxide, and hydroxyl radicals.

[0071] Aspects and embodiments disclosed herein are described as including one or more electrodes. The term “metal electrodes” or grammatical variations thereof as used herein is to be understood to encompass electrodes formed from, comprising, or consisting of one or more metals,for example, titanium, aluminum, or nickel although the term “metal electrode” does not exclude electrodes including of consisting of other metals or alloys. In some embodiments, a “metal electrode” may include multiple layers of different metals. Metal electrodes utilized in any one or more of the embodiments disclosed herein may include a core of a high-conductivity metal, for example, copper or aluminum, coated with a metal or metal oxide having a high resistance to chemical attack by electrolyte solutions, for example, a layer of titanium, platinum, a mixed metal oxide (MMO), magnetite, ferrite, cobalt spinel, tantalum, palladium, iridium, silver, gold, or other coating materials. “Metal electrodes” may be coated with an oxidation resistant coating, for example, but not limited to, platinum, a mixed metal oxide (MMO), magnetite, ferrite, cobalt spinel, tantalum, palladium, iridium, silver, gold, or other coating materials. Mixed metal oxides utilized in embodiments disclosed herein may include an oxide or oxides of one or more of ruthenium, rhodium, tantalum (optionally alloyed with antimony and / or manganese), titanium, iridium, zinc, tin, antimony, a titanium-nickel alloy, a titanium-copper alloy, a titanium-iron alloy, a titanium-cobalt alloy, or other appropriate metals or alloys. Anodes utilized in embodiments disclosed herein may be coated with platinum and / or an oxide or oxides of one or more of iridium, ruthenium, tin, rhodium, or tantalum (optionally alloyed with antimony and / or manganese). Cathodes utilized in embodiments disclosed herein may be coated with platinum and / or an oxide or oxides of one or more of iridium, ruthenium, and titanium. In still another embodiment, electrodes utilized in any one or more of the embodiments disclosed herein may include, or be coated with, any one or more catalysts compounds disclosed herein (whether or not specifically labeled herein as a catalyst) including boron-doped diamond and / or sinters of boron-doped diamond. Electrodes utilized in embodiments disclosed herein may include a base of one or more of titanium, tantalum, zirconium, niobium, tungsten, and / or silicon. Electrodes for any of the electrochemical cells disclosed herein can be formed as or from plates, sheets, foils, extrusions, and / or sinters.

[0072] In general, the conductivity of the feed stream may be between about 0 and 25 S / cm, as dependent on the salinity. Brackish water having a salinity between about 0.5% and 2.0% may have a conductivity of between about 0.5 S / cm and about 4.0 S / cm, for example, about 0.8 S / cm or about 3.0 S / cm. Seawater having a salinity of about 3.5% may have a conductivity of between about 4.5 S / cm and 5.5 S / cm, for example, about 5.0 S / cm or about 4.8 S / cm. Brine having a salinity between about 5.0% and 10% may have a conductivity of between about 7 S / cmand 13.0 S / cm, for example, about 12.6 S / cm. Saturated brine having a salinity of about 25% may have a conductivity of between about 20.0 S / cm and about 23.0 S / cm, for example, about 22.2 S / cm. In general, salinity and conductivity may follow the linear relationship such as that disclosed and detailed in United States Patent Nos. 11,795,074 and 11,802,063, the complete disclosures of which are hereby incorporated by reference herein.

[0073] It should also be noted that further additional information regarding electrodes, electrochemical cells, hydrogen generation, etc. can be found in United States Patent Nos. 11,795,074 and 11,802,063, the complete disclosures of which are again hereby incorporated by reference herein.

[0074] In some embodiments, PF AS-containing feed composition can be controlled by acid dosing. Acid injection can reduce pH, thus limiting formation of unwanted byproducts. In some embodiments, pH of the feed stream may be measured by a sensor. The measurement may be communicated to an acid injection system configured to dose the feed stream with acid, responsive to the pH measurement. PFAS-containing feed compositions may be controlled by any other method of controlling pH as disclosed herein.

[0075] In certain embodiments, a portion of the product solution may be recirculated to the feed stream. Optionally, the product solution may include, for example, H2O2 that can be recirculated as an oxidant, or any other suitable oxidant known in the electrochemical cell art. The ratio of recirculation to feed stream may be controlled, for example, with control valves. By recirculating a portion of the product solution to the feed stream, the overall PFAS mitigation or reduction may be increased. Employing recirculation of product may reduce a required number of electrochemical cells necessary to produce a desirable amount of PFAS reduction and / or mitigation, reducing overall footprint of the system and increasing options for end use.

[0076] Systems and methods disclosed herein may include electrochemical cells having features for abating, mitigating, minimizing, preventing, or eliminating scaling of the electrodes. In some embodiments, pH control may limit precipitation of unwanted byproducts at the cathode. During operation of a conventional electrochemical cell, local pH at the cathode can reach or exceed 11. Such high local pH may result in the precipitation of Mg and Ca ions, producing scaling on the electrode. In some embodiments, local pH at the cathode is controlled to between about 8 and 9. Average pH within the electrochemical cell may be controlled to between about 6 and 9, for example between about 7 and 8.

[0077] Feedforward control of pH may be implemented. In some embodiments, pH of the feed is measured with a sensor. One or more parameters of the system may be adjusted responsive to the pH measurement. For instance, PF AS-containing feed composition, flow rate, applied current / voltage, or oxidant concentration at one or more electrode may be adjusted to control pH within a desired range. In some embodiments, pH may be controlled by the addition of a pH adjuster, for example a mineral acid or a caustic such as NaOH. The measurement may be communicated to an injection system which may adjust one or more operating parameters to control pH. The injection system may control pH of the feed solution or of a solution within the electrochemical cell. Additionally, or alternatively, feedback control of pH may be implemented. For instance, pH of a product may be measured with a sensor. One or more parameters may be adjusted as described or the measurement may be communicated to an injection system which may adjust one or more operating parameters as described.

[0078] Systems and methods disclosed herein may employ a periodic polarity reversal of the anode and cathode to mitigate, minimize, prevent, or eliminate generation or accumulation of hydrogen gas at the cathode, for example, by controlling local pH at the electrodes. While not wishing to be bound to any one theory, hydrogen, or for that matter other gases such as oxygen, may cause PFAS-based foaming at one or more or the anode and / or cathode of an electrochemical cell, which may cause a drop in the ability of the systems of the present invention to efficiently reduce, mitigate, and / or destroy any PFAS in the feed stream. In some electrochemical cells, polarity is reversed after a long period of operation to reduce scaling, for example every 12 hours or every other day of operation. As disclosed herein, polarity may be reversed more often to limit hydrogen gas formation. For instance, polarity may be reversed every few minutes to limit formation of hydrogen gas, depending on system conditions.

[0079] Reversing polarity to limit formation of hydrogen gas may also limit formation of scaling. During operation of the electrochemical cell, localized acid generation typically occurs at the anode, while hydrogen and byproducts accumulate at the cathode. By reversing polarity, acid may be generated at the former cathode (now-anode), limiting the localized production of hydrogen gas and precipitates at the cathode. The acid generation at the now-anode may also control localized pH, minimizing the further precipitation of byproducts at the electrode, and preventing scaling.

[0080] The polarity reversal sequence may occur symmetrically or asymmetrically. In some embodiments, polarity is reversed every few minutes, for example, every 2, 5, 10, 15, 20, 30, 40, 50, or 60 minutes. In some embodiments, polarity is reversed every few hours, for example, every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, or 24 hours. Each polarity reversal may last between a few minutes to several hours. The type and length of the polarity reversal cycle is not limiting. Generally, the type and length of the polarity reversal cycle may depend on the PFAS-containing feed composition and conditions of the electrochemical cell. The type and length of polarity reversal may depend on average pH within the electrochemical cell or localized pH at the anode or cathode. In some embodiments, polarity reversal may be implemented responsive to a pH measurement outside a desired range.

[0081] Temperature can have an effect on product formation and reaction rates. In some embodiments, temperature is controlled to between about -2 to 45 °C. Outside this temperature range, the feed solution may react with the electrode catalyst to form unstable byproducts. Feedback or feedforward control of temperature may be implemented. In some embodiments temperature of the feed or product solution is measured with a thermometer. One or more parameters of the system may be adjusted responsive to the temperature measurement. For example, flow rate, pH, temperature, or dissolved oxygen concentration can be adjusted responsive to the measurement. Temperature may be adjusted, for example, with a heat exchanger.

[0082] Systems and methods disclosed herein include electrochemical cells having features for abating, mitigating, minimizing, preventing, or eliminating the formation of hydrogen gas (or some other gas or gaseous compound) in the electrochemical cell and / or hydrogen (or some other gas or gaseous compound) dissolved in an electrolyte in the electrochemical cell. Implementation of hydrogen abatement may be a function of current density, flow rate, dissolved hydrogen concentration, and / or dissolved oxygen concentration (optionally, as a function of pressure). Furthermore, hydrogen gas (or some other gas or gaseous compound) generation may be a function of temperature, pH, composition, and oxidation-reduction potential of the solution proximate the cathode in the electrochemical cell. The relationship between these parameters can be quantified by scanning current and voltage and plotting an IV-curve. A transition point from water generation to H2 production can be identified from the IV-curve. The IV-curve displays an inflection point when voltage exceeds a threshold that indicates production of hydrogen gas (orsome other gas or gaseous compound). Overall system performance can be calibrated by adjusting the aforementioned parameters.

[0083] Methods disclosed herein may comprise applying current across the anode and the cathode at a voltage sufficient to mitigate, and / or destroy any PFAS in the feed stream. The current may be applied in a constant mode until a change is required and / or desired. For example, current may be applied constantly until a polarity reversal or anode and cathode is to be applied or current is to be applied in a pulsed waveform. Such a change may occur, for example, when one or more parameter indicates that hydrogen gas may be generated at the cathode.

[0084] Generally, as a safety measure, H2 gas emissions may be monitored and controlled. H2 gas may be measured with a sensor. One or more of the methods disclosed herein may be implemented in response to a high measurement of H2 gas in the product or within the system.

[0085] Voltage across the anode and the cathode can be measured to determine when hydrogen gas begins to generate in the electrochemical cell. Parameters such as temperature, pH, and composition of the fluids may affect the voltage at which hydrogen gas begins to be generated. Pressure may increase diffusivity of oxygen in the fluid, thus increased pressure, flow rate, and turbulence may also have an effect on the voltage at which hydrogen gas begins to be generated. Generically, Figures 5A-5D are a set of graphs illustrating the enhancement of the oxygen evolution reaction (OER) at various partial pressures of oxygen and flow velocities. As shown in the graphs of Figures 5A-5D, an inflection point in the IV-curve indicates the voltage at which hydrogen gas is generated.

[0086] The data presented in Figure 5 A show the change in inflection point (between about1.0V and about 1.5V) for a flow rate of 3.1 m / s at varying pressure. The data presented in Figure 5B show the change in inflection point (between about 0.8V and about 1.1V) for oxygen injected at a pressure of about 1.4 bar at varying flow rates. Air introduced at about 6.9 bar can generate a dissolved oxygen content similar to oxygen injected at 1.4 bar. The data presented in Figure 5C show the change in inflection point (between about 1.0V and about 1.3V) for oxygen injected at about 3.1 bar at varying flow rates. The data presented in Figure 5D show the change in inflection point (between about 1.0V and about 1.5V) for oxygen injected at about 6.9 bar at varying flow rates.

[0087] In some embodiments, voltage may be maintained within or below any of the above identified ranges to limit hydrogen gas generation in the electrochemical cell, or even with therange of about 0.1V to about 10V, or even more specifically in the range of about 0.1V to about 2.1V. Alternatively, voltage in the PFAS-mitigation, or destruction, systems of the present invention can be in the range of about 0.1V to about 10V, or from about 0.2V to about 9.9V, or from about 0.3V to about 9.8V, or from about 0.4V to about 9.7V, or from about 0.5V to about 9.6V, or from about 0.6V to about 9.5V, or from about 0.7V to about 9.4V, or from about 0.8V to about 9.3 V, or from about 0.9V to about 9.2V, or from about IV to about 9.1V, 1.1V to about 9V, or from about 1.2V to about 8.9V, or from about 1.3V to about 8.8V, or from about 1.4V to about 8.7V, or from about 1.5V to about 8.6V, or from about 1.6V to about 8.5V, or from about 1.7V to about 8.4V, or from about 1.8V to about 8.3V, or from about 1.9V to about 8.2V, or from about 2V to about 8.1V, 2.1V to about 8V, or from about 2.2V to about 7.9V, or from about 2.3V to about 7.8V, or from about 2.4V to about 1.1N, or from about 2.5V to about 7.6V, or from about 2.6V to about 7.5V, or from about 2.7V to about 7.4V, or from about 2.8V to about 7.3V, or from about 2.9V to about 7.2V, or from about 3V to about 7.1V, 3.1V to about 7V, or from about 3.2V to about 6.9V, or from about 3.3V to about 6.8V, or from about 3.4V to about 6.7V, or from about 3.5V to about 6.6V, or from about 3.6V to about 6.5V, or from about 3.7V to about 6.4V, or from about 3.8V to about 6.3V, or from about 3.9V to about 6.2V, or from about 4V to about 6.1V, 4.1V to about 6V, or from about 4.2V to about 5.9V, or from about 4.3V to about 5.8V, or from about 4.4V to about 5.7V, or from about 4.5V to about 5.6V, or from about 4.6V to about 5.5V, or from about 4.7V to about 5.4V, or from about 4.8V to about 5.3V, or from about 4.9V to about 5.2V, or even from about 5V to about 5.1V. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non- disclosed, numerical ranges.

[0088] In still another embodiment, voltage may be maintained below about 0.8V, 0.9V, 1.0V, or 1.1V for a system introducing oxygen at 1.4 bar or air at 6.9 bar depending on the flow rate. Voltage may be maintained below about 1 ,0V, 1 ,2V, or 1 ,3 V for a system introducing oxygen at about 3.1 bar depending on the flow rate. Voltage may be maintained below about 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, or 1.5V for a system introducing oxygen at about 6.9 bar depending on the flow rate. Voltage may be maintained below about 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, or 1.5V for a system running a flow rate of about 3.1 m / s depending on the voltage. Further parameters may be determined from the graphs shown in Figures 5A-5D.

[0089] In some embodiments, conditions are controlled to maintain the system within the predetermined parameters that are associated with no formation of hydrogen gas. Current applied across the anode-cathode pair may be altered or reversed responsive to the parameters indication conditions which may result in hydrogen gas generation. Depending on the system parameters, conditions may be controlled to maintain the voltage below about 4.0V, 3.0V, 2.0V, 1.5 V, 1.0 V, or 0.5 V. The parameters may be controlled to maintain the voltage between about 1.5 V and about 0.5V. The parameters may be controlled to maintain the voltage between about 1.5V and about 4.0V. The parameters may be controlled to maintain the voltage between about 0.5V and about 4.0V.

[0090] In some embodiments, the addition of an oxidant (for example, oxygen) to the process solution may eliminate the generation and / or accumulation of hydrogen in these reactions. Thus, in some embodiments, the addition of an oxidant may not only reduce or suppress formation and / or accumulation of hydrogen as a byproduct of the operation of the PFAS-mitigation, or destruction, system of the present invention.

[0091] In addition to, or as an alternative to air or oxygen, the oxidizing agent may include any one or more suitable oxidants including, but not limited to, oxygen enriched air, ozone, carbon dioxide, hydrogen peroxide, fluorine, chlorine, bromine, iodine, nitric acid, nitrous oxide, a nitrate, sulfuric acid, peroxysulfuric acid, peroxymonosulfuric acid, a hexavalent chromium compound, a permanganate compound, sodium perborate, potassium nitrate, or any other known oxidizing compound known. The oxidizing agent may be a gas, a solid, or a liquid phase agent. The oxidizing agent may include a product of the electrochemical cell. For example, the oxidizing agent may be H2O2 produced by the electrochemical cell. The oxidizing agent may include any chemical compound having a sufficiently low reducing potential to intercept electrons from passing into a water molecule to generate free hydrogen. The oxidizing agent may include any chemical compound having a reducing potential that is less negative than -0.8277 volts versus a standard hydrogen electrode. The reducing potential of the oxidizing agent may vary based on kinetic factors such as concentration, temperature, and the effect of a catalyst.

[0092] Introducing the oxidizing agent into a process solution may include contacting the solution with the oxidizing agent gas or injecting an oxidizing agent-containing liquid into the solution. The oxidizing agent may be introduced into the feed stream or another process solution.In some embodiments, the oxidizing agent gas is an oxygen-containing gas. The oxidizing agentcontaining liquid may be an oxygen-containing liquid.

[0093] In some embodiments, oxidation reduction potential (ORP) can be measured in the feed, within the system, or at the product with a sensor. Any one or more parameters of the system may be adjusted responsive to the ORP measurement. For example, dissolved oxygen concentration, flow rate, pH, temperature, or feed composition can be adjusted responsive to the ORP measurement.

[0094] Composition of the solution within the system may be altered by altering flow rate or velocity of the feed stream. Generally, increasing flow rate or velocity may increase turbulence and mixing of the solution within the system. Since reactions typically occur locally at the anode or cathode of the electrochemical cell, increasing turbulence may have an effect on normalizing solution composition and pH within the system. In particular, increasing turbulence or flow rate may increase a rate of PFAS-destruction, or mitigation, and decrease a rate of generation of unwanted hydrogen gas.

[0095] Feedback or feedforward control of flow rate or velocity may be implemented. In some embodiments, flow rate or flow velocity of the feed is measured with a flow meter. One or more parameters of the system may be adjusted responsive to the flow rate or velocity measurement. For example, flow rate or velocity, pH, temperature, or dissolved oxygen concentration can be adjusted responsive to the measurement. The measurement may be communicated to a circulation pump to control flow rate or velocity as necessary. Flow rate may be controlled to be between about 0.1 and about 10 m3 / hr. Flow rate may be controlled to be about 0.1 m3 / hr, about 0.5 m3 / hr, about 1.0 m3 / hr, about 2.0 m3 / hr, about 3.0 m3 / hr, about 4.0 m3 / hr, about 5.0 m3 / hr, about 6.0 m3 / hr, about 7.0 m3 / hr, about 8.0 m3 / hr, about 9.0 m3 / hr, about 9.5 m3 / hr, or even about m3 / hr. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0096] Flow velocity may be controlled between about 0.01 m / s and 10 m / s or even between about 0.1 m / s and 10 m / s. In any of the embodiments disclosed herein, the electrochemical cell of the present invention are configured to operate at high fluid velocities, which can nominally be in the range of about 0. 1 m / s (meter per second) to about 10 m / s, or from about 0.25 m / s to about 9.75 m / s, or from about 0.5 m / s to about 9.5 m / s, or from about 0.75 m / sto about 9.25 m / s, or from about 1 m / s to about 9 m / s, or from about 1 .25 m / s to about 8.75 m / s, or from about 1.5 m / s to about 8.5 m / s, or from about 1.75 m / s to about 8.25 m / s, or from about 2 m / s to about 8 m / s, or from about 2.25 m / s to about 7.75 m / s, or from about 2.5 m / s to about 7.5 m / s, or from about 2.75 m / s to about 7.25 m / s, or from about 3 m / s to about 7 m / s, or from about3.25 m / s to about 6.75 m / s, or from about 3.5 m / s to about 6.5 m / s, or from about 3.75 m / s to about6.25 m / s, or from about 4 m / s to about 6 m / s, or from about 4.25 m / s to about 5.75 m / s, about 4.5 m / s to about 5.5 m / s, or from about 4.75 m / s to about 5.25 m / s, or even about 5 m / s. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / n on-disclosed, numerical ranges.

[0097] Alternatively, flow velocity may be controlled to be any value stated herein including, but not limited to, about 1.0 m / s, 2.0 m / s, 3.0 m / s, or 4.0 m / s. In some embodiments, flow velocity can be controlled to between about 2.0 and about 2.5 m / s. Flow velocity can be controlled to between about 2.5 m / s and about 3.0 m / s. Flow velocity can be controlled to be between about 3.0 m / s and about 3.5 m / s. In some embodiments, flow velocity can be controlled to be about 2.0 m / s, 2.1 m / s, 2.2 m / s, 2.3 m / s, 2.4 m / s, 2.5 m / s, 2.6 m / s, 2.7 m / s, 2.8 m / s, 2.9 m / s, 3.0 m / s, 3.1 m / s, 3.2 m / s, 3.3 m / s, 3.4 m / s, or 3.5 m / s. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges. Flow rate or velocity may be increased or decreased as necessary to increase or decrease foaming, turbulence, and / or and mixing. In still another instance, flow velocity can be varied, and / or increased, in any suitable manner and / or any suitable range to accomplish one or more of self-cleaning and / or scale mitigation in any of the electrochemical systems, or cells, disclosed herein.

[0098] Additionally, one or more parameters of the product or within the system may be measured to determine a required adjustment of flow rate or flow velocity. For example, flow rate or velocity may be increased or decreased based on a measurement of local pH within the system or composition of the product. Flow rate or velocity may be increased where local pH within the system varies widely to neutralize pH, or where a measurement of the product indicates that there may be scaling of the electrodes.

[0099] In some embodiments, the pH of the system and local pH at the cathode can be controlled by adjusting flow rate or velocity. The bulk pH of PF AS-containing feed stream is generally in a neutral range. However, the kinetics of the reactions occurring within theelectrochemical cell may drive up pH within the system. As such, the local pH around the cathode can exceed 10 or 11. Local OH- concentration at the cathode can be increased by increasing velocity (i.e., turbulence and mixing). In some embodiments, flow rate is increased to increase local OH- concentration at the cathode. Thus, in some embodiments, flow rate or velocity is increased to decrease local pH at the cathode. Further, in some embodiments, increasing flow velocity can mitigate for high pH and / or OH- formation results in more basic conditions (e.g. pH greater than 10). In some instances, a high local pKb can increase the rate of scale formation. While not wishing to be bound to any one embodiment, in such cases high flow velocities can help to promote mass transfer, facilitating the Oxygen Reducing Reaction (ORR) whilst also preventing Ca2+ / Mg2+scale formation.

[0100] In another embodiment, the dissolved oxygen content of the treatment stream can be modified in real time due to feedback provided from dissolved oxygen sensor 228. In one embodiment, the pH of the treatment stream in a system according to the present invention can be in any suitable range including, but not limited to, a pH of from about 5 to about 9, or from about 5.1 to about 8.9, or from about 5.2 to about 8.8, or from about 5.3 to about 8.7, or from about 5.4 to about 8.6, or from about 5.5 to about 8.5, or from about 5.6 to about 8.4, or from about 5.7 to about 8.3, or from about 5.8 to about 8.2, or from about 5.9 to about 8.1, or from about 6 to about 8, or from about 6.1 to about 7.9, or from about 6.2 to about 7.8, or from about 6.3 to about 7.7, or from about 6.4 to about 7.6, or from about 6.5 to about 7.5, or from about 6.6 to about 7.4, or from about 6.7 to about 7.3, or from about 6.8 to about 7.2, or from about 6.9 to about 7.1 , or even about 7. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0101] At concentrations above its solubility, H2 (or some other gas or gaseous compound) may outgas as it is produced, displacing fluid volume, causing foaming, and / or blinding the cathode. In some embodiments, flow rate and velocity may be controlled to decrease local fluid volume at the cathode. By decreasing local fluid volume while maintaining the same OH- production rate, local pH at the cathode may be increased. Flow rate and velocity may be controlled to ensure an adequate volume at the electrodes for the reactions.

[0102] Systems and methods may be operated at a controlled current density. In some embodiments, current density is controlled to generate product solution while suppressing hydrogen generation. The current density corresponding to induced hydrogen generation may varywith other parameters. In one example, for an exemplary feed stream (brine) that is exposed to air at atmospheric pressure, hydrogen generation may begin at a current density of about 200 A / m2. In contrast, for the same feed stream being exposed to air at 6.9 bar, hydrogen generation may not begin until about 2,250 A / m2. Similarly, increasing flow rate or oxygenation of the feed stream may allow the electrochemical device to operate at higher current densities, and thus to permit a more efficient mitigation / destruction of PFAS, or a higher amount of PF AS mitigated / destroyed in a given period, before hydrogen generation begins. In some embodiments, current density is optimized (i.e., increased) to generate product solution while suppressing hydrogen generation. Depending on the parameters, current density may range between about 10 A / m2to about 5,000 A / m2, or even between about 200 A / m2and about 3,000 A / m2. In another embodiment, the current density can be higher, up to about 20,000 A / m2, in conjunction with the use of various catalysts including, but not limited to, boron-doped diamond and / or sinters of boron-doped diamond. It should be noted that although various numerical values (such as, e.g., current densities, voltages, etc.) are given in positive numbers, they can also be the same in corresponding negative values if measured at the cathode rather than at the anode of the electrochemical cell in a system according to the present invention.

[0103] In still another embodiment, the current density of the present invention is between about 10 A / m2and about 5,000 A / m2, between about 15 A / m2and about 4,900 A / m2, between about 20 A / m2and about 4,800 A / m2, between about 30 A / m2and about 4,700 A / m2, between about 40 A / m2and about 4,600 A / m2, between about 50 A / m2and about 4,500 A / m2, between about 60 A / m2and about 4,400 A / m2, between about 70 A / m2and about 4,300 A / m2, between about 80 A / m2and about 4,200 A / m2, between about 90 A / m2and about 4,100 A / m2, between about 100 A / m2and about 4,000 A / m2, between about 200 A / m2and about 3,900 A / m2, between about 300 A / m2and about 3,800 A / m2, between about 400 A / m2and about 3,700 A / m2, between about 500 A / m2and about 3,600 A / m2, between about 600 A / m2and about 3,500 A / m2, between about 700 A / m2and about 3,400 A / m2, between about 800 A / m2and about 3,300 A / m2, 900 A / m2and about 3,200 A / m2, between about 1,000 A / m2and about 3,100 A / m2, between about 1,100A / m2and about 3,000 A / m2, between about 1,200 A / m2and about 2,900 A / m2, between about1,300 A / m2and about 2,800 A / m2, between about 1,400 A / m2and about 2,700 A / m2, between about 1,500 A / m2and about 2,500 A / m2, between about 1,600 A / m2and about 2,400 A / m2, between about 1,700 A / m2and about 2,300 A / m2, between about 1,800 A / m2and about 2,300A / m2, between about 1,900 A / m2and about 2,200 A / m2, between about 2,000 A / m2and about 2, 100 A / m2, or even about 2,050 A / m2. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0104] Current may be increased by operating with a high linear flow velocity. Without being bound to a particular theory, it is believed that with increased flow rate of the feed stream oxygen consumed by reaction with hydrogen may be more quickly replenished by fresh feed. Increasing the flow rate of the feed stream thus may provide for the electrodes to operate at higher current densities, and produce more product solution before hydrogen generation begins. In some embodiments, increased oxygenation may similarly increase current, for example, either by increasing flow rate or increasing availability of oxidant in the feed stream. Additionally, the relationship between the interplay between hydrogen and oxygen described herein is a function of the ORR in the case of electrochemical pathways relative to pH.

[0105] The current across the anode-cathode pair may be applied at a voltage sufficient to generate product solution. Generally, the electrochemical cell may be designed to operate at an applied current / voltage that enables all or substantially all of the hydrogen to react with oxygen supplied by the feed stream. In some embodiments, the current / voltage applied across the anodecathode pair may be controlled to limit generation of free hydrogen. In some embodiments, current and voltage can be measured across the electrode pair with an electrical sensor. For example, a potentiostat may be utilized to measure electrical parameters and generate a current-voltage curve. Any one or more parameters of the system may be adjusted responsive to the electrical measurement. For example, applied current and voltage can be adjusted accordingly. In some embodiments, flow rate or feed composition (for example, oxidant concentration) can be adjusted responsive to the electrical parameter measurement.

[0106] Additionally, variations in total dissolved solids (TDS) of the feed stream may affect its conductivity. Cell voltage and conductivity are inversely related. Thus, in some embodiments, overall power consumption of an electrochemical cell can be controlled by controlling TDS concentration in the feed stream. Feed stream TDS concentration may be controlled by selectively introducing either seawater, brackish water, or brine. Conductivity of the feed stream or product stream may be measured with a sensor. Any one or more parameters of the system may be adjusted responsive to the conductivity measurement. In some embodiments, flowrate, feed composition, or pH may be adjusted responsive to the conductivity measurement. In some embodiments, oxidant may be overdosed to reach a saturation limit of the oxidant in the feed stream. As previously described, the solubility limit of oxygen can be a challenge to eliminating the generation and / or accumulation of hydrogen within the electrochemical cell. In some embodiments, the dissolved oxygen concentration may be increased by increasing feed stream pressure or increasing the pressure of injected oxidant (for example, oxygen or air). The amount of oxygen overdosing may be dependent on, for example, flow conditions or turbulence within the electrochemical cell, diffusivity of oxygen within the electrochemical cell, operating current, cathode area, etc.

[0107] In the embodiments of the present invention, the electrochemical cells and / or electrolyzer utilized herein are configured to operate with a total dissolved solids (TDS) in the range of about 300 to about 35,000 mg / L, or from about 400 to about 34,000 mg / L, or from about 500 to about 33,000 mg / L, or from about 600 to about 32,000 mg / L, or from about 700 to about 31,000 mg / L, or from about 800 to about 30,000 mg / L, or from about 900 to about 29,000 mg / L, or from about 1,000 to about 28,000 mg / L, or from about 2,000 to about 27,000 mg / L, or from about 3000 to about 26,000 mg / L, or from about 4,000 to about 25,000 mg / L, or from about 5,000 to about 24,000 mg / L, or from about 6,000 to about 23,000 mg / L, or from about 7,000 to about 22,000 mg / L, or from about 8,000 to about 21,000 mg / L, or from about 9,000 to about 20,000 mg / L, or from about 10,000 to about 19,000 mg / L, or from about 11,000 to about 180,00 mg / L, or from about 12,000 to about 17,000 mg / L, or from about 13,000 to about 16,000 mg / L, or from about 14,000 to about 15,000 mg / L, or even about 14,500 mg / L. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0108] In the embodiments of the present invention, the electrochemical cells utilized herein are configured to operate with a dissolved oxygen content in the treatment stream being in the range of about 0.5 bar to about 10 bar, about 0.6 bar to about 9.9 bar, about 0.7 bar to about 9.8 bar, about 0.8 bar to about 9.7 bar, about 0.9 bar to about 9.6 bar, about 1 bar to about 9.5 bar, about 1.1 bar to about 9.4 bar, about 1.2 bar to about 9.3 bar, about 1.3 bar to about 9.2 bar, about1.4 bar to about 9.1 bar, about 1.5 bar to about 9 bar, about 1.6 bar to about 8.9 bar, about 1.7 bar to about 8.8 bar, about 1.8 bar to about 8.7 bar, about 1.9 bar to about 8.6 bar, about 2 bar to about8.5 bar, about 2.1 bar to about 8.4 bar, about 2.2 bar to about 8.3 bar, about 2.3 bar to about 8.2bar, about 2.4 bar to about 8.1 bar, about 2.5 bar to about 8 bar, about 2.6 bar to about 7.9 bar, about 2.7 bar to about 7.8 bar, about 2.8 bar to about 7.7 bar, about 2.9 bar to about 7.6 bar, about 3 bar to about 7.5 bar, about 3.1 bar to about 7.4 bar, about 3.2 bar to about 7.3 bar, about 3.3 bar to about 7.2 bar, about 3.4 bar to about 7.1 bar, about 3.5 bar to about 7 bar, about 3.6 bar to about 6.9 bar, about 3.7 bar to about 6.8 bar, about 3.8 bar to about 6.7 bar, about 3.9 bar to about 6.6 bar, about 4 bar to about 6.5 bar, about 4.1 bar to about 6.4 bar, about 4.2 bar to about 6.3 bar, about 4.3 bar to about 6.2 bar, about 4.4 bar to about 6.1 bar, about 4.5 bar to about 6 bar, about 4.6 bar to about 5.9 bar, about 4.7 bar to about 5.8 bar, about 4.8 bar to about 5.7 bar, about 4.9 bar to about 5.6 bar, about 5 bar to about 5.5 bar, about 5. 1 bar to about 5.4 bar, or even about 5.2 bar to about 5.3 bar. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0109] In another embodiment, the dissolved oxygen content of the treatment stream can be modified in real time due to feedback provided from the one or more dissolved oxygen sensors described below.

[0110] In some embodiments, the oxidant may be injected under pressure greater than atmospheric pressure to increase the solubility of the oxidant in the feed stream or process solution as compared to the solubility of the oxidant in solution under atmospheric pressure. For example, oxygen, air, and / or another oxidant may be introduced into the feed stream at an elevated pressure as noted above, or even at a pressure of from about 1 bar gauge to about 7 bar gauge, about 3 bar gauge to about 5 bar gauge, or at any other pressure desired to introduce a desired amount of oxidant into the solution. In some embodiments, the oxidant may form microbubbles in the electrochemical cell as the oxygenated feed enters the electrochemical cell. The pressure applied to the oxygenated PFAS solution may be reduced relative to the pressure applied to the feed stream during introduction or exposure to the oxidizing agent.[0U1] In accordance with certain embodiments, the electrodes may apply power in a pulsed waveform to limit or eliminate factors that inhibit electrochemical reactions such as polarization and surface adsorption. Applying power in a pulsed waveform may minimize polarization on the electrode surface and mitigate blocking of the electrode surface due to adsorption. Generally, when a cathode is used to reduce dissolved oxygen, its surface may become blocked with ionic species. A corresponding increase in voltage is required to maintain a constantcurrent. The reduced surface catalysis sites may result in an increased current density or potential at the electrode.

[0112] The temporary surface adsorption block on the electrode may be reversible. While not wishing to be bound by any particular theory, it is believed that applying a pulsed waveform may overcome depletion, presumably resulting from the temporary surface adsorption block. The pulsed waveform may deliver electrons for the electrolysis reaction to avoid electrode surface deactivation resulting from polarization, surface adsorption, and other processes that cause oscillation between active and passive modes. In some embodiments, the pulsed waveform may be applied by coupling a non-electrochemical pulse with an electrochemical pulse to improve reaction efficiency, scale prevention and / or mitigation, and / or polarization.

[0113] A pulsed DC waveform may be used to provide intermittent reaction and relaxation modes for an electrochemical reaction. For example, the pulsed waveform may be applied to reversibly alternate an electrode between an “active” and “deactivated” state during steady state DC operation. The pulsed waveform may be applied to any electrochemical reaction. The pulsed waveform may be applied to any electrode, catalyst coated or otherwise. The pulsed waveform may be especially beneficial when using electrochemistry to reduce, mitigate, and / or destroy PFASs, which tend to produce undesirable byproducts, for example, hydrogen. Additionally, in some embodiments, the use of a pulsed waveform in the systems of the present invention are especially desirable when one, or both, of the anode and cathode in an electrochemical cell of a system of the present invention both contain catalysts capable of PFAS mitigation and / or destruction.

[0114] In some embodiments, the active and deactivated states may comprise an increase / decrease in magnitude of applied current, respectively. The active and deactivated states may comprise an on / off mode operation. The active and deactivated states may comprise a reversal of electrical current, such that the anode and cathode electrodes reverse function periodically. By operating in a pulsed waveform, the electrolysis cell may run with less potential. The shaped of the pulsed waveform is non-limiting. The shape may comprise a square wave, a sine wave, a triangular wave, or other shapes. The pulse may be symmetrical or asymmetrical. For example, the pulse shape may be the result of a random waveform generation. The timing between pulses may be regular or irregular.

[0115] The pulsed waveform may be designed to optimize reduction of dissolved oxygen while limiting generation of hydrogen. For example, the pulse may be designed to run as long as possible until calculated that hydrogen will generate or until hydrogen is detected. In some embodiments, power is applied in a pulse of less than 500 seconds, less than 200 seconds, or less than 100 seconds. For example, current may be run in a pulsed mode having a duration of about 90 seconds, 80 seconds, 70 seconds, 60 seconds, 50 seconds, 40 seconds, 30 seconds, 20 seconds, or 10 seconds for each pulse. Additionally, such pulsed power supply may result in a cathodic potential of less than about 1.6 volts, about 1.5 volts, about 1.3 volts, or even about 1.0 volts. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0116] Electrode design may affect one or more parameters described herein. In some embodiments, the dissolved oxygen concentration can be increased by employing a porous carbon based electrode. The carbon based electrode may have a specific surface area of less than about 10 m2 / g. The current density passed on such an electrode is generally low, while the respective total current density is generally less than 5,000 A / m2. In some embodiments, the total current density is less than 4,000 A / m2, less than 3,000 A / m2, less than 2,000 A / m2, less than 1,500 A / m2, or less than 1,000 A / m2. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0117] In some embodiments, a catalyst may be incorporated on the surface of the electrode to mitigate the generation and / or accumulation of hydrogen. The catalyst may be employed to promote the formation of water from dissolved oxygen and generated hydrogen. Typically, the catalyst may be incorporated on the surface of a cathode, where hydrogen gas is generated. The catalyst may comprise a platinum series metal, a noble metal, a rare earth metal, an oxide, or a combination thereof. Exemplary catalysts include rare earth metal oxides, for example, iridium and ruthenium oxides, and other mixed metal oxides (MMO). The catalyst may comprise tin, titanium, tantalum, or antimony. The MMO may comprise platinum. In some embodiments, the coating may be deposited through electrodeposition or thermal deposition.

[0118] The porous carbon based electrode, when combined with a platinum catalyst, may suffer from poor mechanical strength, catalyst instability, and electrode blockage. In some embodiments, the electrodes may be non-porous. For example, the electrodes may be a platinum-plated titanium electrode. The platinum-plated titanium electrode with a geometric surface area may be combined with any of the approaches discussed above, namely, increasing feed stream or oxidant pressure, operating at a high linear flow velocity, or applying a pulsed waveform power supply.

[0119] The electrode surface area to volume ratio can be manipulated through selection of factors such as electrode thickness, inter-electrode spacing, as well as overall cell size. Electrode composition and surface area may be selected to permit polarity reversal. In some embodiments, the anode and cathode are of substantially equal area. In some embodiments, the anode and cathode are both coated with a catalyst. The substantially equal area and catalyst composition of both electrodes promotes interchangeability of anode and cathode, allowing polarity reversal of the electrodes to mitigate scaling.

[0120] Systems may also be designed to promote efficient pulsed power supply. A deactivated electrode during pulsing may be recovered when not in operation or at an opposite potential. In some embodiments, systems disclosed herein may contain multiple electrodes at each anode and cathode. During operation, one electrode may be activated while another electrode is deactivated, i.e., recovering for operation. The activated and deactivated state of each electrode may be reversible. Between pulses, the previously-deactivated electrode may be activated while the previously-activated electrode may be deactivated for recovery.

[0121] In some electrochemical cells, the electrodes may be arranged in parallel split flows, parallel splitting flows, parallel merging flows, and / or parallel splitting / merging flows (as are described in United States Patent Nos. 11,795,074 and 11,802,063, the complete disclosures of which are again hereby incorporated by reference herein. The electrodes may be in fluid communication through direct flow in series, splitting flows, merging flows, or a combination of these. In some embodiments, the electrodes may be fluidically separate and joined by one or more ionic connection, for example, a salt bridge or ion-permeable membrane. The ion-permeable membrane may be selective to monovalent ions.

[0122] Electrochemical cells for use in the systems and methods described herein may include concentric tube electrodes (CTE), flat electrodes (for example, disposed in a parallel plate electrochemical (PPE) cell), spiral wound electrodes, radially arranged electrodes, or interleaved electrodes. The electrochemical cell may be a single pass or a multiple pass device. The electrodes may comprise a valve metal substrate, for example, titanium, tantalum, or niobium. The electrodesmay be rigid metal electrodes. The electrodes may be formed by extrusion. The electrodes may be formed by bending of sheet metal, for example, by folding sheet metal over onto itself. The electrodes may be gas diffusion electrodes, for example, porous gas diffusion electrodes. Exemplary electrochemical cells are described in further detail in International Application Publication No. WO 2017 / 049052, which is incorporated herein by reference in its entirety for all purposes.

[0123] The electrodes may be mono-polar or bipolar. The electrodes may be arranged such that current flows in one pass between electrodes. Current may flow from the anode to the cathode. Alternatively, the electrodes may be arranged such that current flows in more than one pass through the device. Such a device may contain outer electrodes and inner electrodes. In some embodiments, one of the outer electrodes is coated on the inside surface to serve as an anode. The other electrode may be uncoated or coated (for example, to allow for polarity reversal). In some embodiments, the inner electrode may be a bipolar electrode, such that a portion of the outer surface of the inner electrode may be coated, and the remaining portion may be uncoated. In an exemplary embodiment, current may flow through the electrolyte from the coated outer electrode to the uncoated portion of the inner electrode, along the inner electrode to the coated portion, then finally back across the electrolyte to the uncoated outer electrode.

[0124] In some embodiments, the electrodes may be arranged such that current flows in multiple passes through the device with multiple outer electrodes and one inner electrode. By alternating coated and uncoated outer electrodes and coating the inner electrodes at matching intervals, current can flow back and forth through the electrolyte in multiple passes. In some embodiments, outer and inner electrodes are coated to allow for polarity reversal. By allowing multiple passes, the mitigation and / or destruction rate of PFAS can be increased without a proportional increase in applied current. In some instances, increasing the electrical current would require larger wires or bus bars from the DC power supply to the electrochemical cell, larger electrical connectors on the cell and thicker titanium for the electrodes.

[0125] For the same current, a multiple pass device may achieve a higher production rate than a single pass cell. However, the overall voltage drop may be higher for a multiple pass device, and approximately proportional to the number of passes. For the same production rate, a multiple pass cell may require lower current, approximately inversely proportional to the number of passes.Additionally, for the same power output (kW), power supply costs may be more sensitive to output current than output voltage, thereby favoring the multi-pass cells.

[0126] In some embodiments, a system may include sets of electrodes arranged in parallel. The sets of electrodes may be electrically connected in parallel, with one set connected to a positive output from a DC power supply and another set connected to the negative output. In some embodiments, the electrodes in between may be bipolar. The sets of flat electrodes may allow a higher packing density of active electrode area per unit volume of the device, when arranged such that both sides of each electrode are exposed to the electrolyte solution and therefore participate in electrode reactions. The tighter packing and multiple passes may result in a higher pressure drop.

[0127] The electrodes may be housed within a housing designed to electrically isolate the electrodes from the outside environment and to withstand the fluid pressure of electrolyte passing through the electrochemical cell. The housing may be a cylindrical or substantially cylindrical vessel. The housing may be non-conductive, chemically non-reactive to electrolyte solutions, and may have sufficient strength to withstand system pressures. For example, the housing may be designed to withstand up to 10 bar gauge or up to 16 bar gauge to be compatible with the injection of oxidant under pressure, as may be required. In some embodiments, a solid core, central core element, or fluid flow director that prevents fluid from flowing down the center and bypassing the gap between electrodes may be provided. Spacers may be provided between the anode and cathode to maintain a fixed separation. A central gas conduit may be provided for reactant delivery (i.e., any reactant disclosed herein such as oxygen delivery) so that the suitable reactant and / or oxygen may combine with hydrogen produced by, for example, PFAS mitigation and / or destruction reactions in the cell. Fluid, for example, electrolyte undergoing treatment in the cell may flow through the fluid channels in the housing. For example, fluid may be directed in a direction parallel, or at least substantially parallel, to a central longitudinal axis of the electrochemical cell.

[0128] In embodiments disclosed herein including multiple anode or cathode electrodes, the multiple anode electrodes may be referred to collectively as the anode or the anode tube, and the multiple cathode electrodes may be referred to collectively as the cathode or the cathode tube. In embodiments including multiple anode and / or multiple cathode electrodes, the multiple anode electrodes and / or multiple cathode electrodes may be collectively referred to herein as an anodecathode pair.

[0129] Electrical connection may be made between electrode pairs by one or more conductive bridges, which may be formed of the same material as the electrodes, for example, titanium. The electrochemical cell may include a plurality of anodes separated from cathodes by fluid channels. Electrochemical and chemical reactions occur at the surfaces of the electrodes and in the bulk solution to generate a product solution with a lower PF AS concentration.

[0130] Electrochemical cells including spiral wound, concentric, radially arranged, and interleaved electrodes are described in further detail in International Application Publication No. WO 2016 / 133985, which is incorporated herein by reference in its entirety for all purposes.

[0131] As illustrated in Figure 1, within an electrochemical cell 100 various reactions occur at both anode 102 and cathode 104. In order to effect the desired electrochemical reactions electrochemical cell 100 further comprises a power source 106, an electrochemical cell gap 108, a PF AS-containing solution 110, and a proton-exchange membrane (PM) coating 112 on anode 102. Of particular interest is the Hydrogen Evolving Reaction (HER) which occurs at cathodic electrode 104 within cell 100. Hydrogen is stoichiometrically generated in proportion to the rate of electron transfer at cathode 104. Hydrogen has a very low solubility in water (see Figure 2) and, once generated, will off-gas at standard temperatures and pressures. As can be seen from Figure 2, oxygen by comparison has a much higher solubility that increases significantly as pressure is applied.

[0132] As is known, many PFAS species have surfactant properties where such surfactants are chemical compounds that can decrease the surface tension between two matrices. When a surfactant is applied to a fluid-gas mixture it can result in the generation of foam. The presence of foam can, in turn, compromise the rate of electron transfer within a fluid matrix by concurrently decreasing fluid density along with the rate of electron transfer at the electrode surfaces.

[0133] As illustrated in Figure 1, the Oxygen Reducing Reaction (ORR) is one of the critical reactions that occurs at a cathodic surface. Generally speaking, the ORR is rate limited by mass transfer, relative to the amount of oxygen present in solution and the diffusion of oxygen to the surface of the cathode. Once the oxygen present at the electrode surface has been consumed, the cathode will transition to the Hydrogen Evolving Reaction (HER) and begin generating hydrogen. As noted above, when hydrogen is generated it, in turn, will off-gas and cause a surfactant solution to foam. Further information relating to ORRs can be found at, for example,https: / / www.researchgate.net / publication / 338351441_Oxygen_Reduction_Reaction, the full text of which is hereby incorporated herein by reference.

[0134] By increasing the amount of oxygen in solution, while simultaneously increasing fluid velocities at the surface of the cathode, one embodiment of the present invention makes it possible to enhance the OER rate and suppress the HER rate. In doing so, the repent invention makes it possible to achieve the destruction of PFAS-laden fluids while simultaneously suppressing foam generation.

[0135] One exemplary embodiment of an electrochemical system according to the present invention is illustrated in Figure 3, indicated generally at 1200. System 1200 includes an electrochemical cell 1000 (which can be an electrochemical cell 100 according to Figure 1) that may be similar to any of the embodiments of electrochemical cells disclosed herein. When referring to the electrochemical cell and / or electrolyzer of the present invention items 100 and 1000 can be used interchangeably and can be viewed as able to replace one another with modifying any system referring to either one, or both , of items 100 and 1000. A source of oxidizing agent or oxidizing system may be disposed in any suitable conduit upstream of electrochemical cell 1000. The source of PF AS-containing solution 900 is illustrated as a tank.

[0136] Various pumps may control the flow of fluid through the system. One or more sensors may monitor one or more parameters of fluid flowing through the system, for example, of PFAS solution to be introduced to an electrochemical cell in the one or more electrochemical systems, fluid internal to the electrochemical cell, liquid in the point of use, or of product solution produced or generated in the electrochemical cell. These parameters may include, for example, flow rate, ionic concentration, oxygen concentration, hydrogen concentration, pH, electrical parameters, temperature, oxygen reduction potential (ORP), or any other parameters of interest. Additional sensors may monitor parameters of the electrochemical cell itself, for example, current and / or voltage across an anode-cathode pair in the electrochemical cell, temperature of or within the electrochemical cell, or flow rate of electrolyte through the electrochemical cell.

[0137] The pumps and sensors may be in communication with a control system or controller 2000 which communicates with the sensors and pumps and controls operation of the pumps and other elements of the system to achieve desired operating parameters.

[0138] Various operating parameters of the electrochemical systems disclosed herein may be controlled or adjusted by an associated control system or controller based on various parametersmeasured by various sensors located in different portions of the electrochemical systems. The controller may be programmed or configured to regulate introduction of oxidizing agent into PFAS solution to be introduced to the electrochemical cell of a system based at least on one or more of a flow rate of the PFAS solution, a concentration of PFAS in the PFAS solution, or an oxidationreduction potential of a liquid in a point of use for a product solution generated in the electrochemical cell. The controller may be programmed or configured to regulate introduction of the oxidizing agent into the PFAS solution based at least on a concentration of a product compound generated in the electrochemical cell. The controller may be further configured to regulate the concentration of the product compound generated in the electrochemical cell based at least on an oxidation-reduction potential of liquid in a point of use fluidly connectable to the outlet of the housing of the electrochemical cell. In some embodiments, the controller may be configured to introduce the oxidizing agent into PFAS solution in an amount sufficient to prevent formation of hydrogen gas during operation of the electrochemical cell.

[0139] The controller may be programmed or configured to regulate introduction of the oxidizing agent into the PFAS solution or introduction of the PFAS solution into the electrochemical cell based at least on one or more of temperature in the electrochemical cell, pH of the PFAS solution, pH of a product solution generated in the electrochemical cell, flow rate of the aqueous or product solution, ORP of the aqueous or product solution, or current or voltage applied across the anode and the cathode. The controller may be programmed or configured to regulate introduction of the oxidizing agent into the PFAS solution or introduction of the PFAS solution into the electrochemical cell based at least on one or more of an amount of gaseous hydrogen present in the electrochemical cell, a concentration of hydrogen dissolved the PFAS solution, a concentration of oxygen dissolved in the PFAS solution, or a concentration of oxygen dissolved in a product solution generated in the electrochemical cell.

[0140] The controller may be programmed or configured to regulate a current across the anode-cathode pair based on a flow rate of the PFAS solution or a rate of introduction of the oxidizing agent into the PFAS solution. The controller may be programmed or configured to reverse polarity of the anode and the cathode to reduce, prevent, or suppress hydrogen gas generation in the electrochemical cell. For example, the controller may be programmed or configured to reverse polarity of the electrodes responsive to the voltage measured across the anode-cathode pair or the dissolved hydrogen concentration exceeding a predetermined threshold.In some embodiments, the controller may be programmed or configured to reverse polarity of the anode and the cathode to prevent generation of hydrogen gas in the electrochemical cell.

[0141] The controller may be programmed or configured to cause current to be applied in a pulsed waveform as disclosed herein. The controller may be configured to change, alter, or regulate the current applied by the electrodes. In some embodiments, the controller is configured to regulate a duration of pulses of the current. The controller may additionally or alternatively regulate a rate of incidence of pulsed current. The duration of pulses and / or the rate of incidence may occur on regular or irregular intervals (for example, as needed or as determined necessary by a sensor). The controller may regulate a voltage applied across the anode and the cathode. The controller may be programmed or configured to regulate the applied current, applied voltage, or pulsed waveform responsive to a flowrate of the PFAS solution into the electrochemical cell, a voltage measured across the anode and the cathode, or hydrogen gas concentration in the product solution. The controller may be programmed or configured to regulate the applied current, applied voltage, polarity of the electrodes, or pulsed waveform responsive to a flow rate, a pH measurement, a temperature measurement, or an oxidation-reduction potential of at least one process solution. The controller may be programmed or configured to regulate the applied current, applied voltage, polarity of the electrodes, or pulsed waveform responsive to a dissolved oxygen concentration or dissolved hydrogen concentration of at least one process solution.

[0142] In some embodiments, the controller may be programmed or configured to apply current in a pulsed waveform to reduce, prevent, or suppress generation or accumulation of hydrogen gas. For example, the controller may be programmed or configured to apply current in a pulsed waveform responsive to a hydrogen gas concentration exceeding a predetermined threshold sufficient to cause generation of hydrogen gas during operation of the electrochemical cell. In some embodiments, the controller may be programmed or configured to apply current in a pulsed waveform to suppress substantially all hydrogen gas accumulation within the electrochemical cell.

[0143] The controller may be programmed or configured to regulate the applied current, applied voltage, polarity of the electrodes, or pulsed waveform sufficient to prevent generation of hydrogen gas within the electrochemical cell. The applied current, applied voltage, polarity of the electrodes, or pulsed waveform may be dependent on, for example, flow conditions or turbulencewithin the electrochemical cell, diffusivity of oxygen within the electrochemical cell, operating current, cathode area, etc.

[0144] In some embodiments, the controller may be programmed or configured to regulate one or more conditions of the PFAS solution in an amount sufficient to prevent generation of hydrogen gas within the electrochemical cell. The controller may be programmed or configured to regulate a flow rate or composition of the PFAS solution, such that the available oxidant is provided in an amount approximately stoichiometric with a quantity of product compound produced in the electrochemical cell. The regulation of PFAS solution may be dependent on, for example, flow conditions or turbulence within the electrochemical cell, diffusivity of oxygen within the electrochemical cell, operating current, cathode area, etc. The composition of the PFAS solution may be regulated by dosing with one or more compounds, for example, a pH balancing agent or an oxidant.

[0145] In some embodiments, the controller may additionally be programmed or configured to introduce the oxidizing agent into the PFAS solution in an amount sufficient to prevent generation of hydrogen gas within the electrochemical cell. The controller may be programmed or configured to introduce the oxidizing agent into the PFAS solution in an amount approximately stoichiometric with a quantity of product compound produced in the electrochemical cell, and potentially overdose the oxidizing agent above the stoichiometric amount, for example, to provide sufficient oxidizing agent availability at the cathode(s) of the electrochemical cell such that hydrogen is not generated at the cathode(s) during operation. The amount of oxygen overdosing may be dependent on, for example, flow conditions or turbulence within the electrochemical cell, diffusivity of oxygen within the electrochemical cell, operating current, cathode area, etc. The controller may be programmed or configured to introduce the oxidizing agent into the PFAS solution in an amount sufficient to provide for substantially all free hydrogen in the electrochemical cell to be oxidized.

[0146] In general, the controller may be programed to make any change to limit or prevent generation of hydrogen gas. In an IV-curve, a change in voltage may indicate generation of hydrogen gas. Thus, the controller may be enabled to control conditions that maintain the voltage indicative of hydrogen gas production (or predetermined threshold voltage) below the limit that may indicate generation of hydrogen gas. Because hydrogen gas generation is generally dependent on conditions such as temperature, pH, ORP, dissolved oxygen concentration, and dissolvedhydrogen concentration, any one or more of these parameters may be controlled to be maintained within a predetermined range that indicates limited or no production of hydrogen gas within the system.

[0147] The controller for monitoring and controlling operation of the various elements of system may include a computerized control system. The output devices configured to act in response to instructions from the controller may comprise valves, pumps, or switches which may be utilized to introduce PFAS solution from the source into the electrochemical system and / or to control the speed of pumps. One or more sensors may also provide input to the controller. These sensors may include, for example, sensors which may be, for example, pressure sensors, chemical concentration sensors, temperature sensors, or sensors for any other parameters of interest to system. These sensors may be located in any portion of the system where they would be useful, for example, upstream of point of use in fluid communication with a product solution, within the electrochemical cell or in fluid communication with a solution proximate the anode or the cathode, and / or upstream of an inlet of the electrochemical cell in fluid communication with the source of PFAS solution. In addition, the controller may contain one or more interfaces (not shown) that connect the controller to a communication network in addition or as an alternative to the disclosed interconnection mechanisms.

[0148] Referring again to the exemplary system shown in Figure 3, system 1200 may include multiple sensors S1-S5 that may feed data to a control system or controller 2000 which may adjust operating parameters of components of the system 1200 based on the data from the sensors.

[0149] The sensors may include a sensor for measuring hydrogen gas concentration. The sensor for measuring hydrogen gas may be in fluid communication with the product solution. For example, the sensor may be downstream of a cathode, where hydrogen gas tends to be generated. The sensor may be provided to determine when the hydrogen gas has accumulated to a threshold concentration which is dangerous. The sensor for measuring hydrogen gas concentration may be used to provide data to the controller which may be used to reverse polarity of the electrodes, modify applied current or voltage (for example, apply a pulsed waveform), or modify a rate of introduction of PFAS solution or oxidant in response a predetermined threshold.

[0150] The sensors may include a temperature sensor S 1 downstream of the heat exchanger 1210 which may provide feedback for control of the heat exchanger, a temperature sensor SI in oron the electrochemical cell 1000 which may be used to provide data that the controller may use to reverse polarity of the anode and the cathode, modify or apply current in a pulsed waveform, adjust a rate of introduction of the PFAS solution into the electrochemical cell, adjust dosages of oxidizing agent into the PFAS solution, or any other action that may be taken in response to a temperature measurement. The system may additionally or alternatively include a temperature sensor SI which may provide feedback to the controller that may be used to determine when and how much product should be dosed into the system of Figure 3.

[0151] In some embodiments, pH sensors S2 may be provided upstream and / or downstream of the electrochemical cell 1000 and may provide feedback to the controller that may be used to adjust operation of the pH adjustment system 1205 to keep the pH of the PFAS solution entering the electrochemical cell 1000 and / or product solution exiting the electrochemical cell 1000 within desired ranges. For example, the pH adjustment system 1205 may be operated to keep the pH of the PFAS solution (which is generally an aqueous PF AS-containing solution) entering the electrochemical cell 1000 between about 4 and about 10. A pH sensor S2 may be used to provide data that the controller may use to reverse polarity of the anode and the cathode, modify or apply current in a pulsed waveform, adjust a rate of introduction of the PFAS solution into the electrochemical cell, adjust dosages of oxidizing agent into the PFAS solution, or any other action that may be taken in response to a pH measurement.

[0152] System 1200 may include a pH adjustment system 1205 including a source of pH adjuster, for example, a mineral acid or a caustic such as NaOH and a heat exchanger 1210. The pH adjustment system 1205 may adjust the pH of the PFAS solution to a pH rendering reactions for generation of a desired species of product in the electrochemical cell 1000 favorable, to a pH high enough such that the formation of hydrogen gas in the electrochemical cell 1000 is suppressed, and / or to a pH low enough such that precipitation of magnesium from the PFAS solution in the electrochemical cell 1000 is suppressed. The pH adjustment system 1205 may adjust the pH of the PFAS solution to a pH of, for example, between about 2 and about 14 or between about 7 and about 10. The heat exchanger may be used to adjust the temperature of the PFAS solution to a temperature that results in desired reaction kinetics in the electrochemical cell 1000 and / or to adjust the solubility of oxygen or hydrogen in the PFAS solution.

[0153] A dissolved oxygen sensor S3 may be used to measure dissolved oxygen levels in the PFAS solution. A dissolved hydrogen sensor S3 may be used to measure dissolved hydrogenlevels in the PFAS solution. A dissolved oxygen or hydrogen sensor may measure oxygen or hydrogen at an electrode of the system or in the product solution. The controller may utilize an indication of the dissolved oxygen or hydrogen level in the PFAS solution to control the source of oxidizing agent to maintain the dissolved oxygen level in the PFAS solution to be introduced into the electrochemical cell within a desired range. The controller may utilize an indication of the dissolved oxygen or hydrogen level in the product solution to control the source of oxidizing agent to maintain the dissolved oxygen level in the PFAS solution to be introduced into the electrochemical cell within a desired range.

[0154] A flow sensor S4 may provide product solution flow rate data to the controller which may use this data to control operation of pump P, the source of oxidizing agent, and / or current or voltage applied across the anode-cathode pair of the electrochemical cell 1000. In some embodiments, a flow sensor may provide PFAS solution flow rate data to the controller.

[0155] An electrical meter S5, for example, a potentiostat may be utilized to measure electrical parameters and / or generate a current-voltage curve of the PFAS solution or product solution, which may be utilized to gain information about whether the electrochemical cell is operating in a desired range. In some embodiments, the desired range is one in which a divalent hardness concentration falls below a predetermined threshold such that no hydrogen gas is generated within the electrochemical cell. In some embodiments, the desired range is one in which substantially all hydrogen in the electrochemical cell is being reacted with oxygen supplied in the PFAS solution. Data from the electrical meter S5 may be used by the controller to control operation of pump P (i.e., a rate of introduction of the PFAS solution into the electrochemical cell), the source of oxidizing agent, and / or current or voltage applied across the anode-cathode pair of the electrochemical cell 1000. Data from the electrical meter S5 may be used by the controller to reverse polarity of the anode and the cathode or modify or apply current in a pulsed waveform.

[0156] System 1200 may further include a gas separation column 1215 that may be used to remove residual hydrogen from the product solution. A breakout loop 1220 may be provided to allow for sampling of the product solution and / or addition of additional or alternate sensors, for example, sensors for measuring PFAS, oxygen, or hydrogen levels in the product solution.

[0157] Various components of the system 1200 may be serially repeated in line with one another. For example, system 1200 may have multiple repeated subsystems including a heatexchange 1210, pH adjustment system 1205, source of oxidizing agent, electrochemical cell 1000, and possibly pump P arranged serially in line with one another.

[0158] Another embodiment of an electrochemical system is indicated generally at 1300 in Figure 4. System 1300 includes similar components as system 1200 of Figure 3 which are labelled with identical indicators. System 1300 differs from system 1200 in that system 1300 is a “feed & bleed” system whereas system 1200 is a “once through” type of system. In system 1300 product solution generated by electrochemical cell 1000 circulates around loop L until it is desired to output some product solution to storage tank 1105. As or after product solution is removed from loop L, additional PFAS solution may be introduced to loop L from the source of PFAS solution 900.

[0159] With regard to electrochemical cell 1000, electrochemical cell 1000 can also be a multiple celled electrolyzer that can be formed from one or more electrochemical cells as illustrated in Figure 1, be they connected in series and / or in parallel. While not wishing to be bound to any one electrochemical cell setup in such a multiple cell electrolyzer, one suitable electrochemical cell design for use in connection with the present invention is illustrated in Figure 1 and utilizes a proton-exchange membrane (PM) coating 112 on anode 102, however other electrochemical cell designs are within the scope of the present invention so long as at least one of the process parameters discussed herein can be accomplished by the aforementioned electrochemical cell and / or electrolyzer.

[0160] In one or more embodiments according to the present invention, the electrochemical cell and / or electrolyzer is configured to operate with a PFAS initial content in the range of about 0.5 ppb to about 50,000,000 ppb, or from about 5 ppb to about 40,000,000 ppb, or from about 10 ppb to about 30,000,000 ppb, or from about 15 ppb to about 20,000,000 ppb, or from about 20 ppb to about 10,000,000 ppb, or from about 25 ppb to about 9,000,000 ppb, or from about 30 ppb to about 8,000,000 ppb, or from about 35 ppb to about 7,000,000 ppb, or from about 40 ppb to about 6,000,000 ppb, or from about 45 ppb to about 5,000,000 ppb, or from about 50 ppb to about 4,000,000 ppb, or from about 55 ppb to about 3,000,000 ppb, or from about 60 ppb to about 2,000,000 ppb, or from about 65 ppb to about 1,000,000 ppb, or from about 70 ppb to about 900,000 ppb, or from about 75 ppb to about 800,000 ppb, or from about 80 ppb to about 700,000 ppb, or from about 85 ppb to about 600,000 ppb, or from about 90 ppb to about 500,000 ppb, or from about 95 ppb to about 400,000 ppb, or from about 100 ppb to about 300,000 ppb, orfrom about 150 ppb to about 200,000 ppb, or from about 200 ppb to about 100,000 ppb, or from about 250 ppb to about 90,000 ppb, or from about 300 ppb to about 80,000 ppb, or from about 350 ppb to about 70,000 ppb, or from about 400 ppb to about 60,000 ppb, or from about 450 ppb to about 50,000 ppb, or from about 500 ppb to about 40,000 ppb, or from about 750 ppb to about 30,000 ppb, or from about 1,000 ppb to about 20,000 ppb, or from about 1,100 ppb to about 10,000 ppb, or from about 1,200 ppb to about 9,000 ppb, or from about 1,300 ppb to about 8,000 ppb, or from about 1,400 ppb to about 7,000 ppb, or from about 1,500 ppb to about 6,000 ppb, or from about 1,600 ppb to about 5,000 ppb, or from about 1,700 ppb to about 4,000 ppb, or from about 1,800 ppb to about 3,000 ppb, or even from about 1,900 ppb to about 2,000 ppb. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges. Both systems 1200 and 1300 are designed to reduce, remediate, or eliminate PFAS concentrations based on any type of PFAS molecule including, but not limited to C4 to C8 PFAS chain lengths.

[0161] In one embodiment, systems 1200 and 1300 can further optionally include the addition of one or more polar and / or non-polar solvents to the treatment line. Such solvents include, but are not limited to polar aprotic solvents such as dimethyl sulfoxide, sulfolane, dimethyl formamide, N-methylpyrollidinone and others, while non-polar solvents include nonane, decane, hexadecane, naphthalene and others.

[0162] Given the above, as noted above Figures 5A-5D illustrates various graphs relating to the enhancement of the OER at various partial pressures of oxygen and flow velocities in systems 1200 and 1300 of the present invention, while Figure 6 depicts the destruction of PFOA via electrochemical oxidation at various times and in terms of ppm of PFOA. In brief, 11 ppm of PFOA was degraded to approximately 2 ppm over 6.7 hours in the Example of Figure 6 using a system according to any embodiment disclosed herein.

[0163] Turning to Figure 8A, Figure 8A discloses another exemplary electrochemical cell 500. Electrochemical cell 500 may be designed to destroy, mitigate, and / or reduce one or more PFAS compounds. Electrochemical cell 500 includes a first chamber 520, an anode 502 disposed within the first chamber 520, a second chamber 530 with a cathode 503 disposed within the second chamber 530, and an ionic connection 540. Each of the first chamber and the second chamber may have an inlet and an outlet. The first chamber and the second chamber may be positioned remote from each other. In some embodiments, the first chamber and the second chamber are disposedwithin a housing. In other embodiments, the first chamber and the second chamber are disposed within respective housings, separate from each other. Separate housings may facilitate placing the chambers remotely, for example, when the chambers are to be filled with different liquid electrolytes. The first chamber and the second chamber may be fluidically continuous or may be constructed and arranged such that their respective liquid electrolytes do not mix.

[0164] In some embodiments, the ionic connection is constructed and arranged to selectively allow passage of ions, preventing the liquid electrolyte in the first chamber from mixing with the liquid electrolyte in the second chamber. The ionic connection may comprise, for example, a channel, a salt bridge, or an ion-permeable membrane. In some embodiments, the ion- permeable membrane is selectively permeable to monovalent ions. Such an embodiment 500a is illustrated in Figure 8B where an ion exchange membrane 600 is positioned between first chamber 520 with anode 502 and second chamber 530 with cathode 503. In some embodiments, the configuration illustrated in Figure 8B may be configured in an “H-Cell” configuration, wherein the first and second chambers are separated by a channel containing an ion exchange membrane such as, e.g., a cation exchange membrane.

[0165] A salt bridge is a structure which facilitates the transfer of electrons between an anolyte and catholyte solution. Examples of salt bridges include, but are not limited to, ion exchange membranes, proton exchange membranes, agarose plugs, or stagnant fluidic connections. Examples of flow configurations for salt bridged electrochemical cells are shown in Figures 8A and 8B. Further detail in this regard can be found in United States Patent Nos. 11,795,074 and 11,802,063, the complete disclosures of which are again hereby incorporated by reference herein.

[0166] As disclosed in Figures 8A and 8B, it is possible in one embodiment to optimize the destruction of high concentration PFAS containing fluid matrices through the separation of the anolyte and catholyte. In a non-limiting embodiment, an electrochemical cell is configured with an anolyte compartment, a salt bridge, and a catholyte compartment. A fluid containing a high concentration of PFAS is introduced to the anolyte compartment, which is isolated from the catholyte compartment by the salt bridge. Current is applied and the direct electrochemical oxidation of the PFAS solution is enacted at the anode. Hydrogen is generated at the cathode. However, the presence of a salt bridge prevents the infiltration of hydrogen into the anolyte, thus suppressing foam generation.

[0167] In some embodiments, the liquid electrolyte of the first chamber, second chamber, or both may contain one or more PFAS compounds. Typically, as the separation distance increases between electrodes, electrical resistance, which scales with increasing area and path length, becomes a primary concern in electrochemical cell design. In some embodiments, PFAS treatment electrochemical cells disclosed herein may have a resistance per area of the channel or membrane of less than about 10.0 Q / mm2The resistance per area may be less than about 1.0 Q / mm2, less than about 0.1 Q / mm2, or even less than about 0.01 Q / mm2. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0168] The first chamber 520 and the second chamber 530 may be arranged in series, as shown in Figure 7A. The common flow of liquid electrolyte may occur in any direction. The channel length between the first chamber 520 and the second chamber 530 may be greater than about 5 mm, greater than about 10 mm, greater than about 50 mm, greater than about 100 mm, greater than about 500 mm, or greater than about 1,000 mm. The channel length may be at least about 20% of the length of an electrode. For instance, the channel length may be at least about 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, or 100% of the length of an electrode. In some embodiments, the channel length may be equivalent or greater than the channel length of an electrode. The channel length may be at least 100%, 200%, 300%, 400%, or 500% of the length of an electrode. Here, as well as elsewhere in the specification and claims, individual numerical values can be combined to form additional, or even new / non-disclosed, numerical ranges.

[0169] Alternatively, the first chamber 520 and the second chamber 530 may be arranged in parallel, as shown in Figures 7B and the “Split Flow” illustration at the left of Figure 9C. An inlet and outlet of each chamber may be split or merging, as shown in the middle two illustrations in Figure 9C. In particular, a shared electrolyte channel may split into a first channel fluidly connected with at least one of the inlet and the outlet of the first chamber and a second channel fluidly connected with at least one of the inlet and the outlet of the second chamber. The shared electrolyte channel may be fluidly connected to a source of PF AS-containing feed compositions on a first end or any other suitable solution on the other end.

[0170] Each of the first and second chambers (520, 530) may be a single-pass chamber, such that liquid electrolyte is not recycled. Although not shown, in other embodiments, the electrochemical cell may include a recirculating channel. The recirculating channel may extendbetween the outlet and inlet of the same chamber to recirculate liquid electrolyte. In some embodiments, the recirculating channel may comprise an outlet for drawing fluid from the recirculating channel. The outlet may be used to bleed product of the recirculating stream, for example, for testing or to dilute the recirculating stream.

[0171] The first and second chamber may be in fluid communication with different sources of aqueous solution. The different sources of aqueous solution may generally have different compositions. In some embodiments, the different sources of aqueous solution may have different conductivities, PFAS concentrations, etc. For example, in a system for destroying, mitigating, and / or reducing one or more PFAS compounds, the first chamber (anodic chamber) may be fed with one or more PF AS-containing feed compositions and / or solutions. In such an embodiment, the ionic connection may be monovalent selective. Additionally, or alternatively, the first chamber may be constructed and arranged to recirculate liquid electrolyte while the second chamber is constructed and arranged to be a single-pass chamber. In yet another configuration, an oxidant may be introduced into the second chamber to control formation of hydrogen gas. In some embodiments, a dissolved oxygen concentration may be increased in the first chamber and decreased in the second chamber, or vice versa.EXAMPLES

[0172] Several tests related to PFAS destruction using divided electrochemical cell configurations were performed in accordance with embodiments of the present disclosure. Specifically, three tests were performed utilizing an H-Cell configuration similar to that shown and described above with respect to Figure 8B.Test 1

[0173] Test 1 was conducted using a regular H-Cell, dual-compartment electrochemical cell configuration, with an anodic compartment separated from a cathodic compartment by an ion exchange membrane, specifically a cation exchange membrane (CEM) from lonomr Innovations, Inc. Electrodes were provided in each compartment, with the anodic compartment including a niobium-based boron-doped diamond (BDD) anode (dimensions: 2.0 cm x 1.0 cm), while the cathodic compartment included a titanium (Ti) cathode (dimensions: 1.5 cm x 0.6 cm). Both the anodic compartment and the cathodic compartment were filled with approximately 125 mb ofelectrolyte as a working solution, with the conductivity of the electrolytes being controlled using approximately 1400 ppm sodium sulfate (Na2SO4), providing a conductivity of approximately 2000 pS / cm in each compartment. Table 1 below provides the PFAS concentrations of the initial (raw) electrolyte solutions used in each compartment:Table 1

[0174] Test 1 was conducted in a batch mode under continuous magnetic stirring. The IT- Cell module was powered at 50 mA and 12.5 mA / cm2anodic current density, with resulting operating voltage of approximately 9 V using the Chronopotentiometry (CP) electrochemical technique. No pH adjustment was made to the electrolyte solutions. A BioLogic® potentiostat was used to power the H-cell module, and the resulting CP data was recorded as set forth in Table 2 below. Test 1 was run for a total of 4 hours, and samples were collected at 0 hours and 4 hours.Table 2

[0175] Utilizing the data from Table 2, the percent removal of the various PFAS compounds measured in Test 1 were determined, as shown in Table 3:Table 3

[0176] As shown in Table 3, Test 1 resulted in some removal of the various PFAS compounds over the 4 hour run time, including 30% removal of PFOS in the cathode solution.Test 2

[0177] Next, another test (Test 2) was conducted using a similar H-Cell configuration as Test 1, but over a substantially longer run time (i.e., 28.5 hours) and with slightly varying PFAS compound and sodium sulfate concentrations. Specifically, Test 2 was conducted using a regular H-Cell, dual-compartment electrochemical cell configuration, with an anodic compartmentseparated from a cathodic compartment by an ion exchange membrane (i.e., a cation exchange membrane (CEM) from lonomr Innovations, Inc.). Electrodes were provided in each compartment, with the anodic compartment including a niobium-based boron-doped diamond (BDD) anode (dimensions: 2.0 cm x 1.0 cm), while the cathodic compartment included a titanium (Ti) cathode (dimensions: 1.5 cm x 0.6 cm). Both the anodic compartment and the cathodic compartment were filled with approximately 125 m of electrolyte as a working solution, with the conductivity of the electrolytes being controlled using approximately 16,000 ppm sodium sulfate (Na2SO4), equating to a conductivity of approximately 16,000 pS / cm in each compartment. Table 4 below provides the PFAS concentrations of the initial (raw) electrolyte solutions used in each compartment:Table 4

[0178] Test 2 was also conducted in a batch mode under continuous magnetic stirring. The H-Cell module was powered at 50 mA and 12.5 mA / cm2anodic current density, with resulting operating voltage of approximately 9 V using the Chronopotentiometry (CP) electrochemical technique. No pH adjustment was made to the electrolyte solutions. A BioLogic® potentiostat was used to power the H-cell module, and the resulting CP data was recorded as set forth in Table 5 below. As noted above, Test 2 was run for a total of 28.5 hours, and samples were collected at 0 hours and 28.5 hours.Table 5

[0179] Utilizing the data from Table 5, the percent removal of the various PFAS compounds measured in Test 2 were determined, as shown in Table 6:Table 6

[0180] As shown in Table 6, Test 2 resulted in significant removal of the various PFAS compounds after the 28.5 hour run time, including, e.g., 94% removal of PFOA in the anode solution and 98% removal of PFOS in the anode solution.

[0181] The samples obtained in Test 2 were further analyzed for adsorbable organic fluorine (AOF) and fluoride (F-) in order to assess PFAS mineralization. Table 7 below provides the determined adsorbable organic fluorine and fluoride concentrations in the anode solution and cathode solution, respectively:Table 7

[0182] The detection of 16.8 mg / L of fluoride in the anode solution and 9.80 mg / L of fluoride in the cathode solution demonstrates PFAS mineralization in Test 2.Test 3

[0183] Finally, Test 3 was conducted under substantially similar operating parameters and run time (i.e., 28.5 hours) as Test 2, but utilizing differing cathode materials as both Test 1 and Test 2.

[0184] Specifically, Test 3 was conducted using a regular H-Cell, dual-compartment electrochemical cell configuration, with an anodic compartment separated from a cathodic compartment by an ion exchange membrane (i.e., a cation exchange membrane (CEM) from lonomr Innovations, Inc.). Electrodes were provided in each compartment, with the anodic compartment including a niobium-based boron-doped diamond (BDD) anode (dimensions: 2.0 cm x 1.0 cm), while the cathodic compartment included a platinum-coated titanium (Pt / Ti) cathode (dimensions: 1.5 cm x 0.6 cm). Both the anodic compartment and the cathodic compartment were filled with approximately 125 mL of electrolyte as a working solution, with the conductivity of the electrolytes being controlled using approximately 16,000 ppm sodium sulfate (Na2SO4), equating to a conductivity of approximately 16,000 pS / cm in each compartment. Table 8 below provides the PFAS concentrations of the initial (raw) electrolyte solutions used in each compartment:Table 8

[0185] Test 3 was also conducted in a batch mode under continuous magnetic stirring. The H-Cell module was powered at 50 mA and 12.5 mA / cm2anodic current density, with resulting operating voltage of approximately 9 V using the Chronopotentiometry (CP) electrochemical technique. No pH adjustment was made to the electrolyte solutions. A BioLogic*" potentiostat was used to power the H-cell module, and the resulting CP data was recorded as set forth in Table9 below. As noted above, Test 3 was also run for a total of 28.5 hours, and samples were collected at 0 hours and 28.5 hours.Table 9

[0186] Utilizing the data from Table 9, the percent removal of the various PFAS compounds measured in Test 3 were determined, as shown in Table 10:Table 10

[0187] As shown in Table 10, Test 3 resulted in the removal of the various PFAS compounds after the 28.5 hour run time, including, e.g., 87% removal of PFOA in the anode solution and 90% removal of PFOS in the anode solution.

[0188] Aspects and embodiments disclosed herein are not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Aspects and embodiments disclosed herein are capable of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term “plurality” refers to two or more items or components. The terms “comprising,” “including,” “carrying,” “having,” “containing,” and “involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean “including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases “consisting of’ and “consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims. Use of ordinal terms such as “first,” “second,” “third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Claims

CLAIMSWhat is claimed is:

1. An electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and an ion exchange membrane separating the anolyte compartment and the catholyte compartment, wherein at least one of the anolyte compartment and the catholyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds.

2. The electrochemical cell of claim 1, wherein the ion exchange membrane is a cation exchange membrane.

3. The electrochemical cell of claim 1, wherein the at least one anode is a niobium- based boron-doped diamond (BDD) anode.

4. The electrochemical cell of claim 1, wherein the at least one cathode is a titanium cathode.

5. The electrochemical cell of claim 1, wherein the at least one cathode is a platinum- coated titanium cathode.

6. The electrochemical cell of claim 1, wherein the at least one influent fluid containing one or more PFAS compounds further comprises a sodium sulfate solution.

7. The electrochemical cell of claim 1, wherein the ion exchange membrane is positioned within a channel separating the anolyte compartment and the catholyte compartment.

8. The electrochemical cell of claim 1, wherein the at least one anode and the at least one cathode are coupled to at least one power source.

9. A method of operating an electrochemical cell for PFAS remediation, the method comprising: supplying an electrochemical cell, the electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and an ion exchange membrane separating the anolyte compartment and the catholyte compartment; supplying an influent fluid to at least one of the anolyte compartment and the catholyte compartment of the electrochemical cell, wherein the influent fluid comprises one or more PFAS compounds; and conducting electrochemical oxidation of the one or more PFAS compounds in order to reduce, mitigate, and / or eliminate one or more of the one or more PFAS compounds.

10. The method of claim 9, further comprising adding a sodium sulfate solution to the influent fluid to control the conductivity of the influent fluid.

11. The method of claim 9, wherein the ion exchange membrane is a cation exchange membrane.

12. The method of claim 9, wherein the at least one anode is a niobium-based boron- doped diamond (BDD) anode.

13. The method of claim 9, wherein the at least one cathode is a titanium cathode.

14. The method of claim 9, wherein the at least one cathode is a platinum -coated titanium cathode.1 . An electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and a salt bridge connecting the two compartments, wherein at least the anolyte compartment of the electrochemical cell is supplied with at least one influent fluid containing one or more PFAS compounds.

16. The electrochemical cell of claim 15, wherein the electrochemical cell is designed to operate with an influent fluid velocity of between about 0.01 m / s to about 10 m / s.

17. The electrochemical cell of any of claims 15 or 16, wherein the electrochemical cell is configured to operate with a PFAS initial content in the range of about 0.5 ppb to about 50,000,000 ppb.

18. The electrochemical cell of any of claims 15-17, wherein the electrochemical cell utilizes a current density in the range between about 10 A / m2and about 5,000 A / m2.

19. The electrochemical cell of any of claims 15-18, wherein electrochemical cell utilizes a voltage in the range of about 0. IV to about 10V.

20. The electrochemical cell of any of claims 15-19, wherein electrochemical cell utilizes a dissolved oxygen content in the range of about 0.5 bar to about 10 bar.

21. The electrochemical cell of any of claims 15-20, wherein the influent fluid has a TDS value in the range of about 300 to about 200,000 mg / L.

22. The electrochemical cell of any of claims 15-21, wherein the electrochemical cell utilizes at least one catalyst.

23. The electrochemical cell of any of claims 15-22, wherein the electrochemical cell utilizes a pulsed waveform.

24. The electrochemical cell of any of claims 15-23, wherein foaming is controlled in the electrochemical cell via one or more of the addition of oxygen and / or by increasing the partial pressure of the system such that the gas remains entrained in solution.

25. A method of operating an electrochemical cell for PFAS remediation, the method comprising: supplying an electrochemical cell, the electrochemical cell comprising: an anolyte compartment, wherein the anolyte compartment comprises at least one anode; a catholyte compartment, wherein the catholyte compartment comprises at least one cathode; and a salt bridge connecting the two compartments; supplying an influent fluid to the anolyte compartment of the electrochemical cell, wherein the influent fluid comprises one or more PFAS compounds; and conducting anodic electrochemical oxidation of the one or more PFAS compounds in order to reduce, mitigate, and / or eliminate one or more of the one or more PFAS compounds.

26. The method of claim 25, wherein the electrochemical cell is designed to operate with an influent fluid velocity of between about 0.01 m / s to about 10 m / s.

27. The method of any of claims 25 or 26, wherein the electrochemical cell is configured to operate with a PFAS initial content in the range of about 0.5 ppb to about 50,000,000 PPb.

28. The method of any of claims 25-27, wherein the electrochemical cell utilizes a current density in the range between about 10 A / m2and about 5,000 A / m2.

29. The method of any of claims 25-28, wherein electrochemical cell utilizes a voltage in the range of about 0. IV to about 10V.

30. The method of any of claims 25-29, wherein electrochemical cell utilizes a dissolved oxygen content in the range of about 0.5 bar to about 10 bar.

31. The method of any of claims 25-30, wherein the influent fluid has a TDS value in the range of about 300 to about 200,000 mg / L.

32. The method of any of claims 25-31, wherein the electrochemical cell utilizes at least one catalyst.

33. The method of any of claims 25-32, wherein the electrochemical cell utilizes a pulsed waveform.

34. The method of any of claims 25-33, wherein foaming is controlled in the electrochemical cell via one or more of the addition of oxygen and / or by increasing the partial pressure of the system such that the gas remains entrained in solution.

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