PFAS defluorination methods

Abstract

Certain embodiments of the invention provide a photochemical method for aqueous PF AS contaminant degradation, such as for water and waste treatment, comprising irradiating an aqueous solution with UV light in the presence of iodide (I") and an electron-donating organic compound(s) described herein.

Description

[0001] PFAS DEFLUORINATION METHODS

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims priority to United States Provisional Application Number 63 / 608,549 that was filed on December 11, 2023. The entire content of the application referenced above is hereby incorporated by reference herein.

[0004] GOVERNMENT FUNDING

[0005] This invention was made with government support under 211117 awarded by the U.S. Department of Defense. The government has certain rights in the invention.

[0006] BACKGROUND OF THE INVENTION

[0007] Per- and polyfluoroalkyl substances (PFAS) have found extensive use in industry and consumer products as durable materials. Consequently, numerous communities across the United States and worldwide face urgent contamination issues in their water and soil. Current PFAS degradation solutions have limitations. There is a need for reliable and cost-effective treatment methods capable of removing PFAS pollutants from diverse environmental matrices.

[0008] SUMMARY OF THE INVENTION

[0009] Certain embodiments of the invention provide a method for degrading Perfluoroalkyl and polyfluoroalkyl substances (PFAS) impurity from a fluid, comprising: mixing PFAS impurity with iodide ion and an electron-donating compound (e.g., adding an iodide salt and methanol to the fluid), and irradiating the fluid with UV light.

[0010] Certain embodiments of the invention provide a fluid composition described herein.

[0011] Certain embodiments of the invention provide a photochemical reactor comprising a vessel container that holds a fluid composition described herein.

[0012] BRIEF DESCRIPTION OF THE FIGURES

[0013] Figure 1. Time profiles for the defluorination of 0.25 mM PFOA by UV / I (1 mM), UV / I (ImM) + N2, and UV / I (ImM) + CHsOH (100 mM). Reaction conditions: NaHCOi (5 mM), pH 12.0, 254 nm irradiation (an 18 W low pressure Hg lamp in 600 mL solution), and 20 °C.

[0014] Figures 2A-2F. Time profiles of the PFOA defluorination by UV / I + M at varied (Fig.2A) KI concentrations, (Fig.2B) solution pH, and CH3OH concentrations (Fig.2C) without and (Fig.2E) with 0.5 mM SO32added prior to the reaction; (Fig.2D) induction period removal by N2 sparging and SO32addition; (Fig.2F) PFBS defluorination by UV / I and UV / I + M. 0.5 mM SO32was added for (Figs.2D~2F) to facilitate DO removal, and it was not added for (Figs.2A~2C). Default reaction conditions: PFOA (0.25 mM), KI (1 mM), CH3OH (100 mM), NaHCOs (5 mM), pH 12.0, 254 nm irradiation (an 18 W low-pressure Hg lamp in 600 mL solution), and 20 °C.

[0015] Figures 3A-3B. (Fig.3A) Time profiles for the defluorination of PFOA of various initial concentrations by UV / I + M; (Fig.3B) time profiles for the defluorination of 0.5 mM PFOA by UV / I + M, UV / I (1 mM) + S (5 mM, no SO32spike), and UV / S (lOmM, with lOmM SO32spikes every 24 h). Reaction conditions for UV / I + M: KI (1 mM), CH3OH (5 mM), SO32(0.5 mM), NaHCOs (5 mM), pH 12.0, 254 nm irradiation (an 18 W low-pressure Hg lamp in 600 mL solution), and 20 °C.

[0016] Figures 4A-4D. Time profiles for defluorination from (Fig.4A) 100* diluted AFFF, (Fig.4B) 10x diluted still-bottom wastewater, and for (Fig.4C) nitrate and (Fig.4D) nitrite decay in still-bottom. Reaction conditions: 100-fold diluted AFFF or 10-fold diluted still-bottom wastewater, CH3OH (100 mM) or Na2SOs (100 mM), KI (1 mM), pH 12.0, 254 nm irradiation (a 16 W low-pressure Hg lamp in 750 mL solution).

[0017] DETAILED DESCRIPTION

[0018] Various physical separation methods, such as carbon adsorption, ion exchange, and membrane filtration, can remove per- and polyfluoroalkyl substances (PFAS) from contaminated water. Chemical approaches such as electrochemical oxidation, plasma techniques, and hydrothermal processes are also reported for PFAS destruction in water. Photochemical processes were also developed, including UV / sulfite and UV / sulfite / iodide, to destroy PFAS in water.

[0019] These technologies have limitations, for example, for physical separation methods, PF AS-enriched wastewaters from sorbent regeneration, membrane rejection, fire-fighting system cleaning must be treated to degrade PFAS for safe disposal. Electrochemical oxidation cannot treat still-bottom brines that contain concentrated chloride. Plasma treatment is not effective in degrading short-chain PFAS. Hydrothermal methods require specialized high- pressure equipment against leaking and corrosion. The previously developed UV / sulfite methods use sulfite as the electron source. The low atomic efficiency for the electron source and the production of large amount of sulfate are major hurdles for practical application.

[0020] Described herein include new methods to degrade PFAS (per- and polyfluoroalkyl substances) water pollutants, using ultraviolet (UV) light in the presence of iodide ion (e.g., such as supplied by potassium iodide), and electron-donating organic compound(s). Such new method is useful for destroying concentrated PF AS from various water treatment processes including ion-exchange regeneration, nanofiltration and reverse-osmosis membrane rejection, fire-fighting system cleaning, and Aqueous Film Forming Foam (AFFF) treatment, ensuring their safe disposal or reuse. This photochemical process may utilize inexpensive organics such as methanol to effectively destroy PF AS. Without wanting to be bound by theory, iodide ions (e.g., from potassium iodide KI) may serve as the catalyst and remain unchanged throughout the reaction. This method exhibits rapid reaction rates and can efficiently treat PFAS in a broad concentration range.

[0021] Accordingly, certain embodiments of the invention provide a method for degrading Perfluoroalkyl and polyfluoroalkyl substances (PFAS) impurity from a fluid, comprising: mixing PFAS impurity with iodide ion (T) and an electron-donating compound (e.g., adding an iodide salt, and methanol to the fluid), and irradiating the fluid with UV light, wherein the electron-donating compound is a branched or unbranched, saturated or unsaturated, hydrocarbon chain compound having from 1 to 12 carbon atoms, wherein one or more carbon atoms of the hydrocarbon chain is optionally replaced by (-O-), (-S-), or (-NRS-), wherein Rsis H, or alkyl; and wherein at least one terminal carbon of the electron-donating compound is substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, and (=0); or salt thereof.

[0022] In certain embodiments, when the electron-donating compound is a hydrocarbon chain compound having from 2 to 12 carbon atoms (e.g., 3 to 12), one or more other carbon atoms (e.g., another terminal carbon) of the compound is optionally substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, mercapto, oxo(=O), thioxo(=S), and sulfo (-S(=0)20H).

[0023] In certain embodiments, one terminal carbon is substituted with -OH, or -NH2.

[0024] In certain embodiments, one terminal carbon is substituted with -NH2.

[0025] In certain embodiments, one terminal carbon is substituted with -OH. In certain embodiments, the one terminal carbon is further substituted with oxo(=O), or sulfo (- S(=O)2OH).

[0026] In certain embodiments, one terminal carbon is substituted with -OH and (=0), such as in formic acid (HC(=0)0H).

[0027] In certain embodiments, one terminal carbon is substituted with (=0).

[0028] In certain embodiments, only one terminal carbon is substituted with -OH, or -NH2. In certain embodiments, two terminal carbons are each independently substituted with - OH, or -NH2.

[0029] In certain embodiments, the electron-donating compound comprises two or more carbon atoms that are each independently substituted with -OH, or -NH2.

[0030] In certain embodiments, two terminal carbons are substituted with -NH2.

[0031] In certain embodiments, two terminal carbons are substituted with -OH.

[0032] The term “terminal carbon” refers to the carbon(s) at the end of a branched or unbranched carbon chain. For example, an unbranched carbon chain (if n>=2) has two terminal carbons; a branched carbon chain has more than two terminal carbons due to the branch.

[0033] In certain embodiments, the electron-donating compound comprises two or more carbon atoms that are each independently substituted with -OH, or -NH2, wherein carbon atom(s) adjacent to the substituted carbon atoms is unsubstituted. For example, the electron-donating compound may have two hydroxyl or amino substituted carbon atoms, which are separated from each other by one or more intervening, unsubstituted carbon atom(s).

[0034] In certain embodiments, the electron-donating compound has 1 carbon atom. In certain embodiments, the compound is methanol (CH3OH), methylamine (CHsNH2), formic acid (HC(=O)OH), or hydroxymethanesulfonic acid (HO-CH2-S(=O)2OH), or salt thereof. In certain embodiments, the compound is methanol, formic acid, or hydroxymethanesulfonic acid.

[0035] In certain embodiments, the electron-donating compound is methanol.

[0036] In certain embodiments, the electron-donating compound has 1-10 carbon atoms.

[0037] In certain embodiments, the electron-donating compound has 1-8 carbon atoms.

[0038] In certain embodiments, the electron-donating compound has 1-6 carbon atoms.

[0039] In certain embodiments, the electron-donating compound has 1-5 carbon atoms.

[0040] In certain embodiments, the electron-donating compound has 1-4 carbon atoms.

[0041] In certain embodiments, the electron-donating compound has 1-3 carbon atoms.

[0042] In certain embodiments, the electron-donating compound has 1-2 carbon atoms.

[0043] In certain embodiments, the electron-donating compound has 2-8 carbon atoms.

[0044] In certain embodiments, the electron-donating compound has 2-5 carbon atoms.

[0045] In certain embodiments, the electron-donating compound has 3-4 carbon atoms.

[0046] In certain embodiments, the electron-donating compound has structure of formula I:

[0047] (Formula I), wherein n is i, 2, 3, 4, 5, 6, 7 ,8, 9, or 10,

[0048] Ri and R2 are each independently H, -OH, -NH2, (=0), or -S(=O)2OH, provided Ri and R2 are not both H.

[0049] A specific value of Ri is -OH, or -NH2.

[0050] A specific value of R2 is -OH, or -NH2.

[0051] In certain embodiments, both Ri and R2 are -OH.

[0052] In certain embodiments, both Ri and R2 are -NH2.

[0053] A specific value of n is 1.

[0054] In certain embodiments, n is 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, or 1-2.

[0055] In certain embodiments, n is 2-10, 2-6, 2-5, or 2-3.

[0056] In certain embodiments, n is 3-10, 3-6, or 3-5.

[0057] In certain embodiments, the compound is methanol, ethanol, 1-propanol, or 1-butanol.

[0058] In certain embodiments, the compound is CH3OH, or salt thereof.

[0059] In certain embodiments, the compound is CH3OH, or salt thereof.

[0060] In certain embodiments, the compound is CH3OH, or salt thereof.

[0061] The fluid is an aqeous sample to be treated so that PFAS impurity comprised within the aqeous sample could be degraded. In certain embodiments, the fluid is waste brine, such as ionexchange regeneration waste brine (still-bottom brine). In certain embodiments, the fluid is brine, foam fractionation concentrates, concentrated PFAS from nanofiltration or reverse osmosis, concentrated PFAS from electrodialysis, aqueous AFFFs concentrates, or diluted AFFFs (e.g., 100-fold diluted). In certain embodiments, the fluid is diluted still-bottom brine (e.g., 10-fold diluted). In certain embodiments, the aqeous sample (e.g., AFFF or still-bottom brine) is diluted for about 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100-fold or more. In certain embodiments, the aqeous sample (e.g., AFFF or still -bottom brine) is diluted for about 2 to 10-fold, 5 to 10-fold, 2 to 100-fold, 5 to 100-fold, or 10 to 100-fold.

[0062] Iodide ion (F) can be supplied by providing an iodide salt, such as potassium iodide (KI) or sodium iodide (Nal). In certain embodiments, after the iodide salt is added into the fluid, the fluid has an iodide ion concentration of about O.l-lOmM, 0.2-9mM, 0.3-8mM, 0.4-7mM, 0.5- 6mM, 0.6-5mM, 0.7-4mM, 0.8-3mM, or 0.9-2mM. In certain embodiments, the fluid has an iodide ion concentration of about 0.2-2mM. In certain embodiments, the fluid has an iodide ion concentration of about ImM.

[0063] In certain embodiments, the step of mixing PFAS impurity with iodide ion (F) and an electron-donating compound comprises, or consists of, adding an iodide salt into the fluid. In certain embodiments, the step of mixing further comprises adding the electron-donating compound into the fluid. Thus, in certain embodiments, the step of mixing comprises adding an iodide salt and the electron-donating compound into the fluid. In certain embodiments, before the step of adding the electron-donating compound into the fluid, the fluid is free of one or more electron-donating compound(s) (e.g., methanol) described herein.

[0064] In certain embodiments, the fluid has electron-donating compound concentration of about 0. l-500mM (e.g., after the electron-donating compound is added to the fluid). In certain embodiments, the fluid has electron-donating compound concentration of about 0.1-400mM, 0.1-300mM, 0.1-200mM, 0.1-100mM, 0.2-90mM, 0.3-80mM, 0.4-70mM, 0.5-60mM, 0.6- 50mM, 0.7-40mM, 0.8-30mM, or 0.9-20mM.

[0065] In certain embodiments, the fluid has electron-donating compound concentration of about 1-lOOmM. In certain embodiments, the fluid has electron-donating compound concentration of about 2-100mM, 5-100mM, 10-lOOmM, 25-100mM, or 50-100mM. In certain embodiments, the fluid has electron-donating compound concentration of about 1, 2, 5, 10, 25, 50, or lOOmM.

[0066] In certain embodiments, the fluid has electron-donating compound concentration of about O. l-lOmM. In certain embodiments, the fluid has electron-donating compound concentration of about 0.2-9mM, 0.3-8mM, 0.4-7mM, 0.5-6mM, 0.6-5mM, 0.7-4mM, 0.8-3mM, or 0.9-2mM.

[0067] In certain embodiments, the fluid has electron-donating compound concentration of about 1-1 OmM. In certain embodiments, the fluid has electron-donating compound concentration of about 2-9mM, 3-8mM, 4-7mM, or 5-6mM.

[0068] In certain embodiments, the fluid has electron-donating compound concentration of about l-8mM. In certain embodiments, the fluid has electron-donating compound concentration of about l-7mM, l-6mM, or l-5mM.

[0069] In certain embodiments, the fluid has electron-donating compound concentration of about l-5mM, 2-5mM, 3-5mM, or 4-5mM. In certain embodiments, the fluid has electrondonating compound concentration of about 5mM.

[0070] In certain embodiments, the electron-donating compound can be added prior to the beginning of the reaction, such as prior to UV irradiation.

[0071] In certain embodiments, the electron-donating compound can be added as one bolus dose, e.g., prior to the beginning of the reaction. However, the electron-donating compound can be added during the course of the defluorination reaction for one or more times. In certain embodiments, the step of mixing comprises adding the electron-donating compound two or more times (e.g., 2, 3, 4, 5, or 6 times). In certain embodiments, the step of mixing comprises adding the electron-donating compound every 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 24, 36, 48, or 72 hours. In certain embodiments, the step of mixing comprises adding the electron-donating compound continuously.

[0072] In certain embodiments, the fluid electron-donating compound concentration is maintained at about 0.1-500mM throughout the course of the defluorination reaction. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 0.1- 400mM, 0.1-300mM, 0.1-200mM, O.l-lOOmM, 0.2-90mM, 0.3-80mM, 0.4-70mM, 0.5-60mM, 0.6-50mM, 0.7-40mM, 0.8-30mM, or 0.9-20mM.

[0073] In certain embodiments, the fluid electron-donating compound concentration is maintained at about 1-lOOmM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 2-100mM, 5-100mM, 10-lOOmM, 25-100mM, or 50- lOOmM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 1, 2, 5, 10, 25, 50, or lOOmM.

[0074] In certain embodiments, the fluid electron-donating compound concentration is maintained at about O.l-lOmM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 0.2-9mM, 0.3-8mM, 0.4-7mM, 0.5-6mM, 0.6-5mM, 0.7- 4mM, 0.8-3mM, or 0.9-2mM.

[0075] In certain embodiments, the fluid electron-donating compound concentration is maintained at about 1-1 OmM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 2-9mM, 3-8mM, 4-7mM, or 5-6mM.

[0076] In certain embodiments, the fluid electron-donating compound concentration is maintained at about l-8mM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about l-7mM, l-6mM, or l-5mM.

[0077] In certain embodiments, the fluid electron-donating compound concentration is maintained at about l-5mM, 2-5mM, 3-5mM, or 4-5mM. In certain embodiments, the fluid electron-donating compound concentration is maintained at about 5mM.

[0078] One or more (e.g., 1, 2 or 3) electron-donating compound(s) can be added. Thus, in certain embodiments, the method further comprises adding a second electron-donating compound. For example, methanol and ethanol can be added as the first and the second electrondonating compounds respectively.

[0079] In certain embodiments, the method does not comprise adding a sulfite salt. In certain embodiments, the fluid does not comprise sulfite. However, sulfite may be added to faciliate removal of dissolved oxygen (DO). In certain embodiments, the method further comprises adding a sulfite salt, such as sodium sulfite QSfeSCh) or potassium sulfite (K2SO3), to the fluid.

[0080] In certain embodiments, the fluid has a sulfite concentration of about 0.1-20mM, 0.1- lOmM, 0.2-9mM, 0.3-8mM, 0.4-7mM, 0.5-6mM, 0.6-5mM, 0.7-4mM, 0.8-3mM, or 0.9-2mM. In certain embodiments, the fluid has a sulfite concentration of about 0.1 -5mM. In certain embodiments, the fluid has a sulfite concentration of about 0. l-2mM. In certain embodiments, the fluid has a sulfite concentration of about 5, or lOmM. In certain embodiments, the fluid has a sulfite concentration of about 0.5mM.

[0081] In certain embodiments, the method comprises adding a sulfite salt two or more times (e.g., 2, 3, 4, 5, or 6 times). In certain embodiments, the method comprises adding sulfite salt every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 24, 36, 48, or 72 hours. In certain embodiments, the method comprises adding sulfite salt every 24 hours.

[0082] In certain embodiments, the method further comprises adding a bicarbonate salt, such as NaHCCh.

[0083] In certain embodiments, the fluid has a bicarbonate concentration of about 0.1-20mM, O. l-lOmM, 0.2-9mM, 0.3-8mM, 0.4-7mM, 0.5-6mM, 0.6-5mM, 0.7-4mM, 0.8-3mM, or 0.9- 2mM. In certain embodiments, the fluid has a bicarbonate concentration of about 0.1-15mM. In certain embodiments, the fluid has a bicarbonate concentration of about 5mM.

[0084] In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 7-13 (e.g., by adding NaOH). In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 8-13. In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 10-13. In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 11-13. In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 11- 12.5. In certain embodiments, the method further comprises adjusting the pH of the fluid to a pH of about 12.

[0085] In certain embodiments, the method further comprises applying N2 sparging to the fluid.

[0086] In certain embodiments, the method does not comprise applying N2 sparging to the fluid.

[0087] In certain embodiments, the method further comprises maintaining the temperature of the fluid to about 4-90 °C. In certain embodiments, the method further comprises maintaining the temperature of the fluid to about 10-50 °C. In certain embodiments, the method further comprises maintaining the temperature of the fluid to about 15-30 °C. In certain embodiments, the method further comprises maintaining the temperature of the fluid to about 20-25 °C. In certain embodiments, the method further comprises maintaining the temperature of the fluid to about 20 °C.

[0088] In certain embodiments, the ultraviolet (UV) irradiation is provided by a light source comprising, or consisting of, UV light (e.g., 185nm, 254nm, 365nm, or 395nm). In certain embodiments, the light source is a low-pressure lamp. In certain embodiments, the light source is a medium-pressure lamp or high-pressure lamp.

[0089] Certain embodiments of the new methods described herein may also possess advantages over other systems. For example, compared to electrochemical oxidation and plasmatic techniques, the UV-based homogeneous system offers distinct advantages, as it can efficiently destruct various PF AS structures in brine and is not restricted by mass transfer limitations. With respect to cost, as compared to other photochemical systems, utilizing methanol as the electron donor enables superior cost-effectiveness. In addition, the regeneration of PF AS sorbents (e.g., activated carbon and ion-exchange resin) may use concentrated NaCl, NH4CI, NaOH, and methanol / ethanol. The fire-fighting system washing may use a mixture of water and alcohols to clean residual AFFF. In such scenarios, only iodide ion (e.g., KI) is required to add for the PF AS defluorination to occur.

[0090] Regarding higher treatment capacity, with iodide as a sustainable catalyst, in certain embodiments, continuous addition of methanol could provide a continuous capability of degrading concentrated or spiked PF AS. The water-miscible property of methanol means no solubility limit. Excess alcohol is naturally degradable. For comparison, UV / sulfite system is limited by the accumulated sulfate after reaction.

[0091] Certain embodiments of the invention provides a fluid composition comprising PF AS impurity, iodide ion, and an electron-donating compound as described herein (e.g., with concentrations or concentration ranges as described herein). In certain embodiments, the fluid composition further comprises sulfite (SCE2'). In certain embodiments, the fluid composition further comprises bicarbonate (HCO3 ). The PFAS impurity in the fluid composition could be defluorinated by a method described herein, eventually producing a final fluid composition comprising fluoride (F‘) after the reaction.

[0092] Certain embodiments of the invention provides a photochemical reactor comprising a vessel container that comprises a fluid composition described herein.

[0093] Certain embodiments of the invention provides a PFAS defluorination reaction method that is conducted in a photochemical reactor (e.g., that is airtight, and / or has opaque verssel container wall).

[0094] The term "Per- and polyfluoroalkyl substance" or "PFAS" refers to compound(s) comprising fully (per) or partly (poly) fluorinated carbon chain, e.g., that is optionally subsitituted with one or more substituents (e.g., ionizable functional group such as carboxyl, or sulfonic group (-S(=O)2OH)), or salt thereof. In certain embodiments, the PFAS compound is an anionic compound. In certain embodiments, the PFAS compound is a zwitterionic compound (e.g., comprising a quaternary amine group and an acid group). In certain embodiments, a PFAS compound is branched or unbranched, hydrocarbon chain having from 2 to 16 (e.g., 2-10, 3-9, or 4-8) carbon atoms, wherein one or more of the carbon atoms is optionally replaced by (-O-), (-S- ), or (-NRaRb-), wherein Rais H or alkyl, and Rb is absent or alkyl; wherein the hydrocarbon chain is substituted on carbon with two or more F and is further optionally substitute with one or more substituents selected from the group consisting of halo (e.g., Cl), hydroxy, oxo (=0), carboxyl, -NRcRd, -S(=O)2OH, and S(=O)2NReRf, wherein Re and Rf is each independently H or alkyl that is optionally substituted with -NRcRa, carboxy, or hydroxy, wherein Rcand Rd are each independently H or alkyl. In certain embodiments, all C-H bonds of the PF AS compound are substituted with halo (e.g., all C-F bonds in the compound and no C-H bond). In certain embodiments, at least 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of all C-H bonds of the compound are substituted with halo (e.g., compound having a plurality of C-F bonds).

[0095] In certain embodiments, the PF AS impurity comprises one or more PF AS compounds described herein (e.g., in Examples 1-2).

[0096] In certain embodiments, the PF AS impurity comprises a linear PF AS compound.

[0097] In certain embodiments, the PFAS impurity comprises perfluorocarboxylate (PFCA, C11F211 1COO , for example, n is 1-10, 2-9, 3-8, 4-7, or 5-6).

[0098] In certain embodiments, the PFAS impurity comprises perfluorosulfonate (PFSA, C11F211 1 SO3 , for example, n is 1-10, 2-9, 3-8, 4-7, or 5-6).

[0099] In certain embodiments, the PFAS impurity comprises perfluoroalkyl ether carboxylic acid (PFECA).

[0100] In certain embodiments, the PFAS impurity comprises fluorotelomer carboxylic acid (FTCA, for example, F(CF2)n-CH2-COOH or F(CF2)n-CH2CH2-COOH, wherein n is 2, 3, 4, 5, 6, 7, or 8).

[0101] In certain embodiments, the PFAS impurity comprises fluorotelomer sulfonic acid (FTS, for example, F(CF2)n-CH2CH2-SO3H wherein n is 4-8 or 4-10 such as 4, 6, 8, or 10).

[0102] The term "alkyl", by itself or as part of another substituent, means, unless otherwise stated, a straight or branched chain hydrocarbon radical, having the number of carbon atoms designated (i.e., C1-8 means one to eight carbons). Examples include (Ci-Cs)alkyl, (C2-Cs)alkyl, (Ci-Ce)alkyl, (C2-Ce)alkyl, (Ci-C3)alkyl, and (C3-Ce)alkyl. Examples of alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, sec-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, and higher homologs and isomers.

[0103] The term “halo” or “halogen” refers to bromo, chloro, fluoro or iodo. In some embodiments, halogen refers to chloro or fluoro.

[0104] In certain embodiments, the fluid has a PFAS concentration that is lower than about 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0.5 mM.

[0105] In certain embodiments, the fluid has a PFAS concentration that is about 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000pM, or higher. In certain embodiments, the fluid has a PFAS concentration that is about 0.1-9000pM, l-8000pM, 10-7000pM, 25-6000pM, 250-5000pM, 500-4000pM, 600-3000pM, 700-2000pM, 25-6000pM, 25-3000pM, or 25- lOOOpM. In certain embodiments, the Total fluorine (TF) concentrations (e.g., as determined by combustion ion chromatography) in the fluid comprising PFAS impurity to be treated is about 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000 ppm, or higher. In certain embodiments, the Total fluorine (TF) concentrations in the fluid to be treated is about l-200pm, 5-120ppm, 6-110ppm, 60-110ppm, l-2000pm, 5-1200ppm, 6-1100ppm, 60-1100ppm, 1- 12000ppm, 10-11000ppm, 100-10500ppm, 200-10200ppm, 300-10100ppm, 400-10000ppm, 500-9000ppm, 600-8000ppm, 650-7000ppm, or 650-10100ppm.

[0106] In certain embodiments, the PFAS impurity is degraded wherein the final defluorination ratio (e.g., as determined by a method described herein, see Example 1) is at least 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%.

[0107] In certain embodiments, the final defluorination ratio is at least 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, or 5% higher, as compared to that of a control photochemical method wherein no electron-donating compound is added or wherein the fluid does not comprise the electron-donating compound.

[0108] In certain embodiments, the defluorination ratio (deF%) at 6h, 12h, 24h, 36h, 48h, or 72h is at least 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, or 5% higher, as compared to that of a control photochemical method wherein no electron-donating compound is added or wherein the fluid does not comprise the electron-donating compound.

[0109] In certain embodiments, one or more PFAS compound (as described herein including Examples 1-2, such as PFCA, PFSA, PFECA, FTS, or FTCA, etc.) is partly or fully removed from the fluid (e.g., after 24hrs treatment) with a removal ratio (e.g., as determined by high- resolution mass spectrometry (HRMS)) of at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 98.9%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or higher.

[0110] Certain embodiments of the invention provides a concentrate composition (e.g., a ready to use aqueous concentrate composition) that could be added into a fluid (e.g., a to-be-treated fluid, such as waste having PFAS impurity). In certain embodiments, the concentrate composition comprises iodide ion, and an electron-donating compound as described herein. In certain embodiments, the concentrate composition is a 1 OX or 100X concentrate. In certain embodiments, the concentrate composition further comprises sulfite (SCE2-). In certain embodiments, the concentrate composition further comprises bicarbonate (HCCE ). In certain embodiments, the concentrate composition is a 10X concentrate that can be added into a fluid for dilution (e.g., in a 1 :9 mixing ratio) to produce IX final fluid to arrive at a suitable reaction condition as described herein for UV irradiation.

[0111] In certain embodiments, the concentrate composition has an iodide ion concentration of about 1-lOOmM. In certain embodiments, the concentrate composition has an iodide ion concentration of about lOmM.

[0112] In certain embodiments, the fluid has electron-donating compound concentration of about lmM-5M. In certain embodiments, the concentrate composition has an electron-donating compound concentration of about 50mM.

[0113] In certain embodiments, the concentrate composition has a sulfite concentration of about l-200mM. In certain embodiments, the concentrate composition has a sulfite concentration of about lOOmM, 50mM, or 5mM.

[0114] In certain embodiments, the concentrate composition has a bicarbonate concentration of about l-200mM. In certain embodiments, the concentrate composition has a bicarbonate concentration of about 50mM.

[0115] Certain non-limiting exemplary embodiments of the invention include: Embodiment 1. A method for degrading Perfluoroalkyl and polyfluoroalkyl substances (PFAS) impurity from a fluid, comprising: mixing PFAS impurity with iodide ion (F) and an electron-donating compound, and irradiating the fluid with UV light, wherein the electron-donating compound is a branched or unbranched, saturated or unsaturated, hydrocarbon chain compound having from 1 to 12 carbon atoms, wherein one or more carbon atoms of the hydrocarbon chain is optionally replaced by (-O-), (-S-), or (-NRS-), wherein Rsis H, or alkyl; wherein at least one terminal carbon of the compound is substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, and (=0); and wherein one or more other carbon atoms (e.g., another terminal carbon) of the compound (when the compound is a hydrocarbon chain compound having from 2 to 12 (e.g., 3 to 12) carbon atoms) is optionally substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, mercapto, oxo(=O), thioxo(=S), and sulfo (-S(=0)20H); or salt thereof.

[0116] Embodiment 2. The method of Embodiment 1, wherein at least one terminal carbon of the compound is substituted with -OH, or -NH2. Embodiment 3. The method of any one of Embodiments 1-2, wherein two terminal carbons are each independently substituted with -OH, or -NH2.

[0117] Embodiment 4. The method of any one of Embodiments 1-3, wherein the compound comprises two or more carbon atoms that are each independently substituted with -OH, or -NH2, wherein carbon atom(s) adjacent to the substituted carbon atoms is unsubstituted.

[0118] Embodiment 5. The method of any one of Embodiments 1-2, wherein the electron-donating compound comprises 1-6 carbon atoms.

[0119] Embodiment 6. The method of Embodiment 1, wherein the compound is methanol (CH3OH), methylamine (CH3NH2), formic acid (HC(=O)OH), or hydroxymethanesulfonic acid (HO-CH2-S(=O)2OH).

[0120] Embodiment 7. The method of any one of Embodiments 1-5, wherein the electron-donating compound has structure of formula I:

[0121] (Formula I), wherein n is i, 2, 3, 4, 5, 6, 7 ,8, 9, or 10,

[0122] Ri and R2 are each independently H, -OH, -NH2, (=0), or -S(=0)20H, provided Ri and R2 are not both H.

[0123] Embodiment 8. The method of Embodiment 7, wherein Ri and R2 are each independently

[0124] H, -OH, or -NH2.

[0125] Embodiment 9. The method of any one of Embodiments 7-8, wherein n is 1, 2, 3, 4, or 5.

[0126] Embodiment 10. The method of Embodiment 9, wherein the compound is methanol, ethanol, 1 -propanol, or 1 -butanol.

[0127] Embodiment 11. The method of Embodiment 10, wherein the compound is methanol.

[0128] Embodiment 12. The method of Embodiment 1, wherein the compound is CH3OH, or salt thereof.

[0129] Embodiment 13. The method of any one of Embodiments 1-12, wherein the mixing comprises adding an iodide salt (e.g., potassium iodide) into the fluid.

[0130] Embodiment 14. The method of any one of Embodiments 1-12, wherein the mixing comprises adding an iodide salt, and adding the electron-donating compound into the fluid.

[0131] Embodiment 15. The method of Embodiment 14, wherein the electron-donating compound is added into the fluid prior to irradiating with UV light.

[0132] Embodiment 16. The method of Embodiment 14, wherein the electron-donating compound is added two or more times (e.g., over the course of the reaction during irradiation with UV light).

[0133] Embodiment 17. The method of Embodiment 16, wherein the electron-donating compound is added every 3, 6, or 12 hours.

[0134] Embodiment 18. The method of Embodiment 16, wherein the electron-donating compound is added continuously.

[0135] Embodiment 19. The method of any one of Embodiments 1-18, wherein the fluid has an iodide ion concentration of about O.l-lOmM (e.g., ImM) after the iodide salt is added into the fluid.

[0136] Embodiment 20. The method of any one of Embodiments 1-19, wherein the fluid has an electron-donating compound concentration of about 0.1-500mM.

[0137] Embodiment 21. The method of any one of Embodiments 1-20, wherein the fluid has an electron-donating compound concentration of about 1-lOOmM.

[0138] Embodiment 22. The method of any one of Embodiments 1-21, wherein the fluid has an electron-donating compound concentration of about 1-lOmM (e.g., 5mM).

[0139] Embodiment 23. The method of any one of Embodiments 1-22, wherein the fluid electrondonating compound concentration is maintained at about 0.1-500mM.

[0140] Embodiment 24. The method of any one of Embodiments 1-23, wherein the fluid electrondonating compound concentration is maintained at about 1-lOOmM.

[0141] Embodiment 25. The method of any one of Embodiments 1-24, wherein the fluid electrondonating compound concentration is maintained at about 1-lOmM (e.g., 5mM).

[0142] Embodiment 26. The method of any one of Embodiments 1-25, further comprising adding a sulfite salt (e.g., sodium sulfite) one, or more times (e.g., every 6, 12, or 24 hours), to the fluid. Embodiment 27. The method of any one of Embodiments 1-25, wherein the method does not comprise adding a sulfite salt to the fluid.

[0143] Embodiment 28. The method of claim 26, wherein the fluid has a sulfite concentration of about 0.1-20mM (e.g., 0.5, 5, or lOmM).

[0144] Embodiment 29. The method of any one of Embodiments 1-28, further comprising adding a bicarbonate salt (e.g., NaHCOs) to the fluid.

[0145] Embodiment 30. The method of Embodiment 29, wherein the fluid has a bicarbonate concentration of about 0.1-20mM (e.g., 5mM).

[0146] Embodiment 31. The method of Embodiment 30, further comprises adjusting the pH of the fluid to a pH of about 10-13 (e.g., pH 12).

[0147] Embodiment 32. The method of any one of Embodiments 1-31, further comprises applying N2 sparging to the fluid.

[0148] Certain embodiments of the invention will be illustrated in the following non-limiting Example.

[0149] Example 1 Photochemical PFAS degradation methods

[0150] Materials and Methods

[0151] Chemicals

[0152] PFAS chemicals, including perfluorocarboxylates (PFCAs, CnF2n+iCOO ) and perfluorosulfonates (PFSAs, C11F211 1 SO3 ), were purchased from SynQuest Labs and used as received. Potassium iodide (KI), methanol (CH3OH), bicarbonate (NaHCOs), sodium hydroxide (NaOH), and sodium sulfite (Na2SOs) were purchased from Fisher Chemical.

[0153] Photochemical Reactor Settings and Reaction Parameters in Example 1

[0154] In our previous studies,1'3we established a non-limiting, exemplary reactor configuration, where the photoreactor was assembled using Ace Glass parts (#7864-10, #7874- 38, and #7506-14), and covered with aluminum foil. An 18W low-pressure mercury lamp (GPH212T5L / HO) was positioned in the center of the photoreactor, inside the quartz immerse well. To ensure no air intrusion, all three outlets of the photoreactor were sealed with rubber stoppers. For the experimental procedure, we prepared a 600 mL aqueous solution containing 250 pM individual PFAS, 5 mM NaHCCh, and specific concentrations of KI and an organic electron source (e.g., CH3OH). The pH was adjusted using NaOH, and the solution was then loaded into the photoreactor. To maintain a consistent temperature of 20 °C, jacketed cooling water was used. Finally, the reaction was initiated by turning on the UV light.

[0155] Sample Analyses

[0156] The measurement of fluoride ion (F") release was performed using an ion-selective electrode (Fisherbrand™ accumet™) connected to a benchtop meter (Thermo Orion Versa Star Pro). The validity of this method has been confirmed using ion chromatography (IC).1The percentage of defluorination (deF%) is defined as the ratio between the released F in the aqueous solution and the total F within the parent PF AS molecule.

[0157] Results and Discussion

[0158] Substantially Enhanced PEAS Degradation with UV / Iodide + Organics

[0159] The utilization of UV / iodide (UV / I) resulted in a mere 4.8% defluorination of PFOA (0.25 mM) after 24 h (Figure 1). Applying N2 sparging throughout the reaction for DO removal enhanced defluorination to 18.8% (Figure 1). To our surprise, the addition of organic compounds containing hydroxyl (-OH), formyl (-CHO) or amine (-NH2) functional groups into the UV / I system, without the need for DO removal, significantly enhances the defluorination of PFOA (Table 1). Among these compounds, methanol exhibits the highest efficacy, substantially boosting defluorination to 84.9% (Table 1). Moreover, we have identified two general rules for an organic compound to effectively act as an electron donor in the UV / I system: (1) Electrondonating functional groups must be attached to a primary carbon (e.g., -OH as -CH2OH; Table 1, entry 1-4 & 7 versus 5, 6, 8). (2) If there are two or more electron donating groups in the molecule, they cannot be attached to adjacent carbons (Table 1, entry 7 versus 11, 9 versus 10, 10 versus 12, and 22 versus 23).

[0160] Table 1. Enhanced Defluorination of PFOA using UV / I with Various Organic Compounds'

[0161]

[0162] 1 n=0 (methanol) 84.9

[0163] “Reaction conditions: PFOA (0.25 mM), KI (1 mM), organic (100 mM), NaHCCh (5 mM), pH

[0164] 12.0, 254 nm irradiation (an 18 W low-pressure Hg lamp in 600 mL solution), and 20 °C.

[0165] 6With the addition of 0.1 M butylamine, the solution turns white and turbid, consequently preventing UV light from penetrating far enough to induce significant defluorination.

[0166] Optimization of UV / Iodide + Methanol System

[0167] The UV / Iodide + Methanol (UV / I + M) system, which exhibited the highest efficiency, underwent further optimization. Upon investigation into varying concentrations of KI (Figure 2A) and pH (Figure 2B), we confirmed that 1 mM KI and pH 12.0 represents the optimal reaction conditions. The defluorination-time profile in the UV / I + M system displayed three distinct stages: an initial sluggish rate of defluorination, followed by a significant increase, and ultimately reaching a plateau (Figure 2C). We observed that the similar final defluorination ratio can be achieved with CHsOH concentrations ranging from 5 to 100 mM (Figure 2C). However, a higher CH3OH concentration resulted in a shorter duration of the initial induction period. Specifically, increasing the CH3OH concentration from 5 to 100 mM reduced the induction period from 8 to less than 2 h (Figure 2C). We found that performing an N2 purge throughout the reaction eliminates the induction period, even with CH3OH concentrations as low as 5 mM (Figure 2D). This finding suggests that the induction period is likely a result of dissolved oxygen (DO), and increasing the CH3OH concentration aids in the rapid removal of DO, leading to a shortened induction period. To simplify the DO removal process, we chose to add a small amount of SO32(0.5 mM) before the reaction and successfully eliminated the induction period (Figure 2D). Notably, the added SO32does not serve as an electron source and is fully transformed into SO42before the PFAS degradation. By adding 0.5 mM SO32before the reaction, we optimized the CH3OH concentration to 5 mM, resulting in the fastest defluorination rate and highest final defluorination ratio (Figure 2E). Therefore, in this Example, the optimized reaction conditions comprise 1 mM KI, 5 mM CH3OH, 0.5 mM SO32, and pH 12. Furthermore, we applied the optimized reaction conditions to treat a series of PFCAs and PFSAs with concentrations of 0.025 and 0.25 mM (Table 2). Remarkably, we achieved over 80% defluorination for all structures, except for the relatively recalcitrant PFBS. However, by adding 5 mM CH3OH under the condition of 1 mM KI and 0.5 mM SO32, the defluorination of PFBS (0.025 mM) significantly improved from 2.7 % to 46.3 % (Figure 2F).

[0168] Table 2. Defluorination Percentage of Various PFAS by Optimized UV / I + M.a

[0169] "Reaction conditions: KI (1 mM), CH3OH (5 mM), Na3SO3 (0.5 mM), NaHCOs (5 mM), pH 12.0, 254 nm irradiation (an 18 W low-pressure Hg lamp in 600 mL solution), and 20 °C.feThe defluorination of PFBS occurs at a slower rate compared to other structures, and the data represents the defluorination percentage observed at 24 h.

[0170] Comparison of UV / Iodide + Methanol with Other Photochemical Systems

[0171] Utilizing the optimized reaction conditions in the degradation of 0.5 mM PFOA results in a consistent final defluorination ratio (84.9 % for 0.25 mM vs. 82.1% for 0.5 mM, Figure 3 A), albeit with a longer reaction time. However, increasing the PFOA concentration to 1 mM significantly decreases defluorination efficiency (Figure 3 A). Hence, the effective upper concentration limit for PFOA treatment with UV / I + M (5 mM CH3OH applied) is 0.5 mM. When using the UV / sulfite (UV / S) system for the treatment of 0.5 mM PFOA, the utilization of 10 mM SO32only resulted in 34.6% defluorination at 24 h (Figure 3B), where most SO32had been depleted. Although additional 10 mM SO32spikes facilitated further defluorination, a total of 40 mM SO32was necessary to achieve a defluorination level comparable to UV / I + M (Figure 3B). In our prior study, we observed significantly improved SO32utilization with UV / Iodide + Sulfite (UV / I + S) in comparison to UV / S.4In comparing the UV / I + M and UV / I+ S systems, we utilized the same concentration of electron source (5mM CH3OH or SO32) and also kept all other reaction conditions the same (1 mM KI and pH 12.0). Although the initial defluorination rates for these two systems were the same, the UV / I+M system ultimately achieved a 10% higher defluorination ratio compared to UV / I + S (Figure 3B). Hence, CH3OH serves as a more cost-effective and efficient electron source compared to SO32.

[0172] References in Example 1 :

[0173] 1. Bentel, M. J.; Yu, Y.; Xu, L.; Li, Z.; Wong, B. M.; Men, Y.; Liu, J., Defluorination of per-and polyfluoroalkyl substances (PFASs) with hydrated electrons: structural dependence and implications to PF AS remediation and management. Environ. Sci. TechnoL 2019, 53, (7), 3718- 3728.

[0174] 2. Bentel, M. J.; Liu, Z.; Yu, Y.; Gao, J.; Men, Y.; Liu, J., Enhanced degradation of perfluorocarboxylic acids (PFCAs) by UV / sulfite treatment: Reaction mechanisms and system efficiencies at pH 12. Environ. Sci. TechnoL 2020, 7, (5), 351-357.

[0175] 3. Liu, Z.; Bentel, M. J.; Yu, Y.; Ren, C.; Gao, J.; Pulikkal, V. F.; Sun, M.; Men, Y.; Liu, J., Near-Quantitative Defluorination of Perfluorinated and Fluorotel omer Carboxylates and Sulfonates with Integrated Oxidation and Reduction. Environ. Sci. TechnoL 2021, 55, (10), 7052-7062.

[0176] 4. Liu, Z.; Chen, Z.; Gao, J.; Yu, Y.; Men, Y.; Gu, C.; Liu, J., Accelerated degradation of perfluorosulfonates and perfluorocarboxylates by UV / sulfite+ iodide: Reaction mechanisms and system efficiencies. Environ. Sci. TechnoL 2022, 56, (6), 3699-3709.

[0177] Example 2. Photochemical PFAS degradation in certain wastewater samples

[0178] We further treated real wastewater, including diluted aqueous film-forming foam (AFFF) and “still-bottom” waste brine from ion-exchange resin regeneration, using UV / I + M and compared its performance with UV / I + S. Total fluorine (TF) concentrations in the original AFFF and still-bottom were measured at 10,100 ppm and 650 ppm, respectively, using combustion ion chromatography. Table 3 shows the identified PFAS concentrations in the undiluted wastewater. In this section, the electron donor concentration (methanol (M) and sulfite (S)) was set at 100 mM to maximize defluorination and remove eaqquenchers (e.g., nitrate in still-bottom, as discussed below) without further optimization.

[0179] Table 3. Treatment of Real Wastewater by UV / I + M and UV / I + S.a

[0180] _ _ . ~ .X1Concentration Removal ratio by Removal ratio by

[0181] PFAS category Compound Cham length((iM)uv / I + M (o / o)iuv / I + S C / o)*

[0182] PFAS in still-bottom and their removal ratio after 24 h treatment

[0183] PFPrA n = 2 1887.6 >99.9 >99.9

[0184] PFBA n = 3 251.0 >99.9 >99.9

[0185] PFCAs PFPeA n = 4 13 2 >99 9 >99 9

[0186] (F(CF2)n-COOH) PFHxA n = 5 2.6 >99 >99.5

[0187] PFNA n = 8 6.4 >99.1 >99.1

[0188] 4:2 FTS n = 4 1.7 89.4 91.3 t (FFt(CCFF2t)n- CCHH2CCHH2- S SOO3HH1)68::22FFTTSSnn==682139966>995837 >993817

[0189] “Reaction conditions: 100-fold diluted AFFF or 10 -fold diluted still -bottom wastewater, CH3OH (100 mM) or Na2SOs (100 mM), KI (1 mM), pH 12.0, 254 nm irradiation (a 16 W low-pressure Hg lamp in 750 mL solution).

[0190] ^Concentrations without a definitive value indicate the limit of quantitation by the HRMS instrument in our study.

[0191] UV / I + M showed comparable or even superior performance in treating real wastewater compared to UV / I + S. Since AFFF is typically diluted about 100-fold for fire suppression, we diluted it 100 times before treatment. Using UV / I + M achieved a higher final defluorination ratio (50%, Figure 4A) compared to UV / I + S (42%). The still-bottom wastewater (UV254 absorbance: 3.9; TOC: 308.4 mg / L) was diluted 10-fold to reduce the influence of natural organic matter blocking UV light. UV / I + M showed nearly identical defluorination efficiency as UV / I + S (Figure 4B). During the first 6 h, PFAS defluorination was slow due to the presence of nitrate (18 mM after 10x dilution, Figure 4C), a major quencher of eaq~. Once nitrate and its intermediate products (e.g., nitrite, Figure 4D) were fully consumed, PFAS defluorination rate increased significantly. After 24 h, defluorination reached 66% for UV / I + M and 67% for UV / I + S (Figure 4B).

[0192] Most PFAS structures in both wastewaters were completely removed after treatment (below detection limit, Table 3). The remaining PFAS, which exhibited high recalcitrance with both UV / I + M and UV / I + S, included PFBS (77.1% removal), 2:3 FTCA (14.9% removal), and 4:2 FTS (89.4% removal). All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

CLAIMSWhat is claimed is:

1. A method for degrading Perfluoroalkyl and polyfluoroalkyl substances (PF AS) impurity from a fluid, comprising: mixing PF AS impurity with iodide ion (F) and an electron-donating compound, and irradiating the fluid with UV light, wherein the electron-donating compound is a branched or unbranched, saturated or unsaturated, hydrocarbon chain compound having from 1 to 12 carbon atoms, wherein one or more carbon atoms of the hydrocarbon chain is optionally replaced by (-O-), (-S-), or (-NRS-), wherein Rsis H, or alkyl; wherein at least one terminal carbon of the compound is substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, and (=0); and wherein one or more other carbon atoms (e.g., another terminal carbon) of the compound (when the compound is a hydrocarbon chain compound having from 2 to 12 (e.g., 3 to 12) carbon atoms) is optionally substituted on carbon with one or more substituents selected from the group consisting of -OH, -NH2, mercapto, oxo(=O), thioxo(=S), and sulfo (-S(=0)20H); or salt thereof.

2. The method of claim 1, wherein at least one terminal carbon of the compound is substituted with -OH, or -NH2.

3. The method of any one of claims 1-2, wherein two terminal carbons are each independently substituted with -OH, or -NH2.

4. The method of any one of claims 1-3, wherein the compound comprises two or more carbon atoms that are each independently substituted with -OH, or -NH2, wherein carbon atom(s) adjacent to the substituted carbon atoms is unsubstituted.

5. The method of any one of claims 1-2, wherein the electron-donating compound comprises 1-6 carbon atoms.

6. The method of claim 1, wherein the compound is methanol (CH3OH), methylamine(CH3NH2), formic acid (HC(=O)OH), or hydroxymethanesulfonic acid (HO-CH2-S(=O)2OH).

7. The method of any one of claims 1-5, wherein the electron-donating compound has structure of formula I:(Formula I), wherein n is i, 2, 3, 4, 5, 6, 7 ,8, 9, or 10,Ri and R2 are each independently H, -OH, -NH2, (=0), or -S(=O)2OH, provided Ri and R2 are not both H.

8. The method of claim 7, wherein Ri and R2 are each independently H, -OH, or -NH2.

9. The method of any one of claims 7-8, wherein n is 1, 2, 3, 4, or 5.

10. The method of claim 9, wherein the compound is methanol, ethanol, 1 -propanol, or 1- butanol.

11. The method of claim 10, wherein the compound is methanol.

12. The method of claim 1, wherein the compound is CH3OH,or salt thereof.

13. The method of any one of claims 1-12, wherein the mixing comprises adding an iodide salt (e.g., potassium iodide) into the fluid.

14. The method of any one of claims 1-12, wherein the mixing comprises adding an iodide salt, and adding the electron-donating compound into the fluid.

15. The method of claim 14, wherein the electron-donating compound is added into the fluid prior to irradiating with UV light.

16. The method of claim 14, wherein the electron-donating compound is added two or more times (e.g., over the course of the reaction during irradiation with UV light).

17. The method of claim 16, wherein the electron-donating compound is added every 3, 6, or 12 hours.

18. The method of claim 16, wherein the electron-donating compound is added continuously.

19. The method of any one of claims 1-18, wherein the fluid has an iodide ion concentration of about 0.1-lOmM (e.g., ImM) after the iodide salt is added into the fluid.

20. The method of any one of claims 1-19, wherein the fluid has an electron-donating compound concentration of about 0.1-500mM.

21. The method of any one of claims 1-20, wherein the fluid has an electron-donating compound concentration of about 1-lOOmM.

22. The method of any one of claims 1-21, wherein the fluid has an electron-donating compound concentration of about 1-1 OmM (e.g., 5mM).

23. The method of any one of claims 1-22, wherein the fluid electron-donating compound concentration is maintained at about 0. l-500mM.

24. The method of any one of claims 1-23, wherein the fluid electron-donating compound concentration is maintained at about 1-lOOmM.

25. The method of any one of claims 1-24, wherein the fluid electron-donating compound concentration is maintained at about 1-lOmM (e.g., 5mM).

26. The method of any one of claims 1-25, further comprising adding a sulfite salt (e.g., sodium sulfite) one, or more times (e.g., every 6, 12, or 24 hours), to the fluid.

27. The method of any one of claims 1-25, wherein the method does not comprise adding a sulfite salt to the fluid.

28. The method of claim 26, wherein the fluid has a sulfite concentration of about 0.1- 20mM (e.g., 0.5, 5, or lOmM).

29. The method of any one of claims 1-28, further comprising adding a bicarbonate salt (e.g., NaHCCh) to the fluid.

30. The method of claim 29, wherein the fluid has a bicarbonate concentration of about 0.1- 20mM (e.g., 5mM).

31. The method of claim 30, further comprises adjusting the pH of the fluid to a pH of about 10-13 (e.g., pH 12).

32. The method of any one of claims 1-31, further comprises applying N2 sparging to the fluid.

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