WO2025212369A1 - Compositions for regenerating ion exchange resins loaded with per- and polyfluorinated alkyl substances - Google Patents

Abstract

A regenerant solution for a per- and polyfluoroalkyl substances (PFAS)-exhausted anion exchange material includes a bromide or iodide metal salt present at a concentration of about 0.1% to about 60% by weight of the regenerant solution, ethanol present at about 0.1% to about 98% by weight of the regenerant solution, and water, or it can contain a tetrachloroferrate complex present at a concentration of about 0.1% to about 20% by weight of the regenerant solution, methanol or ethanol present at about 0.1% to about 98% by weight of the regenerant solution, and water. The solutions can be used to remove or recover one or more of Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), Perfluorohexane sulfonate (PFHxS), Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA) from an aqueous composition comprising (PFAS) by eluting an anion exchange resin material that is exhausted with the PFAS with the regenerant solutions.

Description

COMPOS)TIONS FOR REGENERATING ION EXCHANGE RESINS LOADED WITH PER- AND POLYFLUORINATED ALKYL SUBSTANCES

BACKGROUND

Fluorochemicals have been used in a wide variety of applications including the water-proofing of materials, as protective coatings for metals, as fire-fighting foams for electrical and grease fires, for semi-conductor etching, and as lubricants. Reasons for such widespread use of fluorochemicals include their favorable physical properties which include chemical inertness, low coefficients of friction, and low polarizabilities (i.e., fiuorophilicity). Per- and polyfluoroalkyl substances (PFAS) refer to a large group of fluorinated aliphatic chemicals, for which there is currently a focus due to the widespread contamination of water around the world with an array of these substances.

PFAS contain carbon-fluorine bonds, which are some of the strongest bonds in organic chemistry. Consequently, the substances are virtually non-biodegradable - an advantage when they are in use, but quite the opposite if they make their way into the environment Compounds in this class namely accumulate in the bodies of living organisms once ingested. Their durability means that even traces must be removed from wastewater and that contaminated groundwater must be cleaned up. This involves adhering to national and regional limits measured in parts per trillion (ppt), some of which are extremely low.

Anion exchange resins are one of the few effective technologies for removing PFAS during the water treatment process. Ion exchange is a process in which ions are exchanged between a solution and an ion exchanger, typically an insoluble solid or gel which may be treated to include functional groups. Anion exchangers are used for negatively charged anions. Cation exchangers are used for positively charged cations. Ion exchange can be a reversible process in that the ion exchanger can be regenerated or loaded by washing the ion exchange resin with an excess of the ions to be exchanged (e.g., chloride ions, sodium ions, hydrogen ions and hydroxide ions etc.).

A number of anion exchange resins have been marketed for their high selectivity for PFAS, e.g. AMBERLITE™ PSR 2 Plus, DOWEX™ PSR-2, AMBERLITE™ PSR 3, Lewatit® TP 108, Lewatit® TP 108 DW, Lewatit® MonoPlus TP 109, Lewatit® K 6362, Purofine® PFA694E, SIR- 110-MP-HP, SIR-110-HP, SEPLITE® LSI106, Calres® 2301, Calres® 2309, Calres® 2304, Sorbix® LC3 and use of such products is increasing. There is a need and desire for practical regeneration strategies so that such products can be reused during processes that remove PFAS from water.

Brine is commonly used to regenerate anion exchange resins. However, it is known that regenerating PFAS-exhausted resins is challenging because of the high affinity of the resins for PFAS and/or the reduced solubility of PFAS in concentrated brine, and regeneration recoveries and appropriate strategies vary depending on the PFAS and resin properties. To achieve effective generation may require use of organic solvents.

Deng et al., Removal of perfluorooctane sulfonate from wastewater by anion exchange resins: Effects of resin properties and solution chemistry, Water Research 44 (2010), 5188-5195 reported that when a mixture of 1% NaCI and 10%-70% methanol was used as regeneration solution for polyacrylic and polystyrene resins sorbed with perfluorooctane sulfonate (PFOS), the regeneration rate increased with the increase in methanol concentration. However, strongly basic anion exchange resin could only be regenerated with 1% NaCI and 70% MeOH, while the weakly basic anion exchange resin could be regenerated by either 1 % NaCI/70% MeOH or 1% NaOH/30%-70% MeOH. The test data showed styrenic resins performed poorly in loading PFAS species, which is contrary to subsequent studies, such as Liu and Sun (discussed below).

Chularueangaksorn et al., Regeneration and Reusability of Anion Exchange Resin Used in Perfluorooctane Sulfonate Removal by Batch Experiments, Journal of Applied Polymer Science 2013, 884-890. DOI: 10.1002/app.39169 utilized 1%-5% NaCI or NaOH with MeOH/deionized water (7:3) to regenerate Purolite Company (Japan) PFA300 polystyrene cross-linked DVB resin loaded with PFOS.

US Patent Nos. 10,287,185; 10,913,668; 11,027,988; and 11,174,175 are directed to a sustainable system for removing and concentrating PFAS from water that reclaims and reuses spent regenerant solution. The anion exchange resin is a macro-porous, strong base anion exchange resin. Exemplified is a cross-linked polystyrene chain and divinylbenzene cross-links. Regenerant solution may include a mixture of a salt or base, a solvent, such as an alcohol, and water. An optimized regenerant solution includes about 50% to about 90% methanol by volume, about 10% to about 50% water by volume, and about 1% to about 5% salt or base by weight, preferably about 70% methanol by volume, about 28% water by volume, and about 2% salt or base by weight.

However, sodium chloride has solubility issues in certain methanol/water mixtures. The inventors found that the concentration of sodium chloride could not exceed 2% when using 80% methanol, and that sodium chloride has an even lower solubility in ethanol. Further, sodium chloride was not very effective to strip PFAS off a polystyrene, strong anion exchange resin at low concentrations of 2% or less. Moreover, methanol is a toxic solvent and there is a desire to avoid using a high percentage of it from safety, environmental, and cost perspectives.

Y.-L. Liu and M. Sun, Ion exchange removal and resin regeneration to treat per- and polyfluoroalkyl ether acids and other emerging PFAS in drinking water, Water Research 207 (2021). https://doi.Org/10.1016/j.watres.2021.117781 studied five polystyrene-divinylbenzene (PS-DVB) resins and found that increasing brine concentration from 0.01% to 10% and using salts in the chloride form enhanced regeneration when used with up to 20% (v/v) methanol. However, neither the 10% salt solutions alone nor a combination of salt with up to 20% methanol could effectively regenerate the PFAS species off the ion exchange resins. Moreover, the regeneration tests in this study, as well as Deng et al., were conducted in bottles with a long equilibrium time and did not use a column test, which would better resemble practical conditions.

US 2005/0177000A1 discloses a method of recovering a fluorinated acid surfactant or salt thereof from activated carbon to which said fluorinated acid surfactant has been adsorbed. The regeneration fluid contains methanol, water and sulfuric acid.

EP1700869A1 discloses a method for recovery of a fluorinated anionic surfactant from a basic anion exchange resin having quaternary ammonium groups, the method comprising eluting the anion exchange resin with a composition comprising an ammonium salt and a water miscible organic solvent.

It is an objective of the present disclosure to provide alternative and improved regenerant solutions for anion exchange resins used in processes that remove PFAS from water. In particular, provision of an improved elution process, for example, being improved in the amount of PFAS, particularly the most strongly adsorbed Perfluorosulfonic acid species such as PFOS and Perfluorohexane sulfonate (PFHxS), that can be eluted, or by minimizing the amount of eluting liquid needed to recover the PFAS. The sulfonated PFAS species adsorb much more strongly on anion resins than the carboxylated PFAS species with equal chain length.

Conventional regenerants are not capable of effectively stripping off the longer chain sulfonated PFAS species at simple regeneration conditions. It is further an objective of the present disclosure to provide a process that is economically feasible, easy and convenient or a process that uses a simple, low cost eluant to elute strongly adsorbed sulfonated PFAS species. It is another objective to provide a regenerant solution for a PFAS-exhausted resin, where the solution comprises less than 50% methanol, and preferably no methanol.

SUMMARY OF THE INVENTION

The foregoing objectives are achieved in a first aspect by provision of a regenerant solution for a PFAS-exhausted anion exchange material, the solution comprising a bromide or iodide metal salt, preferably an iodide metal salt, present at a concentration of about 0.1% to about 60% by weight, preferably about 1% to about 20% by weight, more preferably about 5% to about 15% by weight of the regenerant solution, ethanol present at about 0.1% to about 98% by weight, preferably about 30% to about 95% by weight, more preferably about 50% to about 90% by weight of the regenerant solution, and water. The advantages of using a bromide metal salt to replace sodium chloride are two-fold. First, bromide is more effective to strip off PFAS than chloride at an equal molar concentration basis. Second, bromide is much more soluble in alcoholic solvents, therefore, it allows higher dosages of bromide in the regenerant solution, and also allows the use of a more environmentally friendly solvent (ethanol), rather than toxic methanol. Iodide salts, with similar solubility profile and stripping power to bromide salts, can also be used for this application. Comparably, sodium chloride has much lower solubility in methanol, and even lower solubility in ethanol. The sulfate and nitrate salts, even though potentially more effective to strip off PFAS than chloride at equal molar concentration basis, also have limited solubility issues in alcoholic solvents.

In some preferred embodiments, the metal of the bromide or iodide metal salt has a +1 , +2, or +3 charge, most preferably a +1 charge.

In certain preferable embodiments, a bromide metal salt is selected from sodium bromide (NaBr), potassium bromide (KBr), calcium bromide (CaBr₂), magnesium bromide (MgBr₂), silver bromide (AgBr), barium bromide (BaBr₂), strontium bromide (SrBr₂), aluminum bromide (AIBr₃), lithium bromide (LiBr), and cesium bromide (CsBr), most preferably sodium bromide.

In a second aspect, a regenerant solution for a PFAS-exhausted anion exchange material comprises a tetrachloroferrate complex present at a concentration of about 0.1% to about 20% by weight, preferably about 5% to about 10% by weight of the regenerant solution, methanol or ethanol present at about 0.1 % to about 98% by weight, preferably about 30% to about 95% by weight, more preferably about 50% to about 90% by weight of the regenerant solution, and water. In another aspect, a method for removal of PFAS from a polystyrene anion exchange resin having quaternary ammonium groups is provided. The method comprises eluting the anion exchange resin with a regenerant solution described herein. The eluting may be performed at around 1-15 BV/hr. The method can further include rinsing the resin with water. The PFAS species loaded on the resin (e.g., PFOA, PFOS, PFHxS, PFBA, and PFHxA) are removed and recovered in the effluent. In certain embodiments, a macroporous, monodisperse, polystyrene- based anion exchange resin having quaternary amine functional groups is utilized In certain of those embodiments, the mean bead size of the resin is about 0.6 to 0.7 mm, most preferably about 0.62 mm.

The method according to the invention may provide one or more of the following advantages. For example, the method can be designed to allow for recovery of substantially all of the PFAS from a basic anion exchange resin having quaternary ammonium groups, such as a polystyrene resin. In certain embodiments, greater than 80% of the PFOS and PFHxS loaded on the resin are removed and recovered in the effluent. Also, the liquid used for recovering the PFAS species from the anion exchange resin is a simple liquid that can be readily and cost effectively manufactured. Further the process may be carried out in a convenient and easy manner. Furthermore, the method generally does not require large amounts of the eluting composition and the regenerant solution is more environmentally friendly and less toxic than methanol-based regenerant solutions.

The method according to the present invention may be used to recover a PFAS compound, such as PFOA, PFOS, PFHxS, PFBA, PFHxA, from an anion exchange resin having quaternary ammonium groups following adsorption thereon from an aqueous composition that contained the PFAS. Such aqueous composition can be for example drinking water or industrial water. Accordingly, in a further aspect, the present invention provides a method of recovery of a PFOA, PFOS, PFHxS, PFBA, or PFHxA compound from an aqueous composition comprising one or more of said PFAS by (i) contacting a polystyrene basic anion exchange resin having quaternary ammonium groups with said aqueous composition; (ii) separating said aqueous composition from said anion exchange resin; and (iii) eluting the obtained anion exchange resin with a regenerant solution described herein. The method can further include (iv) rinsing the resin with water. The PFAS species can be collected and recovered from the effluent. In certain embodiments, a macroporous, monodisperse, polystyrene-based anion exchange resin having quaternary amine functional groups is utilized In certain of those embodiments, the mean bead size of the resin is about 0.6 to 0.7 mm, most preferably about 0.62 mm. DETAILED DESCRIPTION

The present disclosure discloses solutions for regenerating ion exchange materials used in PFAS removal, methods for removal of PFAS from a polystyrene anion exchange resin having quaternary ammonium groups using the solutions, and a method of recovery of a PFOA, PFOS, PFHxS, PFBA, or PFHxA compound from an aqueous composition comprising one or more of said PFAS using the solutions and a polystyrene anion exchange resin having quaternary ammonium groups. The solutions comprise a bromide salt, ethanol, and water or [FeCk]‘, methanol or ethanol, and water.

As used herein, “regeneration” refers to the transfer of an ion exchanger in the initial ionic form prior to the next cycle of use. A “regenerant” refers to the reagent applied to an ion exchanger in order to perform regeneration.

As used herein, “PFAS” refers to per- and polyfluoroalkyl substances. PFAS removed by anion exchange resins may include Perfluorobutyric acid (PFBA), Perfluoropentanoic acid (PFPeA), Perfluorobutane sulfonate (PFBS), Perfluorohexanoic acid (PFHxA), Perfluoroheptanoic acid (PFHpA), Perfluorohexane sulfonate (PFHxS), 6:2 Fiuorotelomer sulfonate (6:2 FTS), Perfluorooctanoic acid (PFOA), Perfluoroheptane sulfonate (PFHpS), Perfluorooctane sulfonate (PFOS), Perfluorononanoic acid (PFNA), 8:2 Fiuorotelomer sulfonate (8:2 FTS).

A “PFAS-exhausted material" refers to a resin or ion exchange material that has been used to remove PFAS from an inlet stream and to which a PFAS compound is bound. An exhausted material may also be referred to as a “spent” material.

As used herein, “resin” refers to an ion exchange resin.

As used herein, “eluting” or “elution” refers to the extraction of a targeted (desirable) ion from an ion exchange material. It may also be referred to as recovery, stripping, or desorption.

As used herein, “eluent” is the solvent or solution pumped through an exchange material to transfer previously sorbed species. It may also be referred to as mobile phase.

As used herein "effluent” refers to the solution collected at the outlet of a column.

The metal of the bromide or iodide metal salt typically has a +1 , +2, or +3 charge, most preferably a +1 charge. Suitable bromide salts for the regenerant solutions include Sodium bromide (NaBr), Potassium bromide (KBr), Calcium bromide (CaBr2), Magnesium bromide (MgBr2), Silver bromide (AgBr), Barium bromide (BaBr?), Strontium bromide (SrBr?), Aluminum bromide (AIBr₃), Lithium bromide (LiBr), and Cesium bromide (CsBr), most preferably sodium bromide. The appropriate salt concentration of the aqueous regenerant solution is in the range of 0.1% to 60% by weight, preferably about 1% to about 20% by weight, most preferably about 5% to about 15% by weight.

The advantages of using a bromide salt to replace sodium chloride are two-fold. First, bromide is more effective to strip off PFAS than chloride at an equal molar concentration basis. Second, bromide is much more soluble in alcoholic solvents, therefore, it allows higher dosages of bromide in the regenerant solution, and also allows the use of a more environmentally friendly solvent (ethanol), rather than toxic methanol. Iodide salts, with similar solubility profile and stripping power to bromide salts, can also be used for this application. Comparably, sodium chloride has much lower solubility in methanol, and even lower solubility in ethanol. The sulfate and nitrate salts, even though potentially more effective to strip off PFAS than chloride at equal molar concentration basis, also have limited solubility issues in alcoholic solvents.

Alternatively, an anionic iron(lll) chlorocomplex, preferably of tetrachloroferrate ([FeCk] ), can be utilized. The FeCk can be formed using iron(lll), such as by combining FeCh and a chloride containing molecule, e.g., NaCI or HCI. Typically, the concentration of tetrachloroferrate complex in the solution is about 0.1% to about 20% by weight, more preferably about 5% to about 10% by weight.

In certain preferred embodiments, when an acid is used to form the complex, the acid may comprise about 0.0018% to about 3.6%, more preferably about 0.018% to about 1.8% by weight of the regenerant solution, such as e.g., 0.01% to 20% or 0.1% to 10% of an 18% HCI solution.

Suitable alcohols that may be used in the regenerant solutions include methanol and ethanol, preferably ethanol. Typically, the concentration of alcohol is in the range of 0.1 % to 98% by weight of the regenerant solution, preferably about 30% to about 95% by weight, most preferably about 50% to about 90% by weight.

Water will make up the balance of the regenerant solution and is typically 0.1 % to 98% by weight, preferably about 5% to about 50% by weight, most preferably about 10% to about 30% by weight of the regenerant solution.

The components of the regenerant solution are admixed by means known in the art. As one example, when an anionic iron(lll) chlorocomplex is used, HCI and/or NaCI may be added into an aqueous FeCI3 solution and the resulting solution can be added into the organic alcohol solvent. The regeneration fluid may be prepared in advance and mixed with the ion exchange materials. Although the order of addition will not be particularly critical, it will generally be preferred to add the alcohol as the last component.

A basic anion exchange resin having quaternary ammonium groups that is loaded with PFAS or spent after PFAS removal may be eluted with the regenerant solution described above by contacting the regenerant solution with the exhausted anion exchange resin. Typically, the elution is carried out by pouring or pumping the regenerant solution over the loaded exchange resin held in a column. In certain preferred embodiments, the solution is eluted at 1-15 BV/hour. Optionally, a rinse may thereafter occur with water, e.g., demineralized water at a rate of 1-20 BV/hour. Upon exiting the column, the eluate will contain PFAS. The PFAS may then be recovered from the effluent by suitable separation methods such as distillation, extraction or crystallization. Alternatively, the exchange resin may be treated with the regenerant solution by gently stirring the anion exchange resin with the regenerant solution followed by separating the anion exchange resin from the regenerant solution e.g. by filtration. The amount of regenerant solution that is needed to recover PFAS from the anion exchange resin depends on the amount and nature of the PFAS that are adsorbed on the anion exchange resin as well as on the composition of the regenerant solution. It has been found that generally a composition comprising a metal salt, sodium bromide or iron chloride, is highly effective.

The total amount of regeneration solution and its composition is typically determined on basis of the amount of ion exchange material to be regenerated and the actual loading of the particles. One should generally apply a large excess of the regeneration liquid. It is preferred that the regenerant be used in an amount of at least 3 times, especially 4 to 12 times, the quantity (volume) of exchange material to be treated. The excess regeneration liquid can easily be drained from the regenerated particles after the regeneration process is finished. The drained liquid can be weighed and analyzed to determine the actual amount and composition of the drained regeneration liquid. The composition and amount of the drained regeneration liquid can then be adjusted by adding appropriate amounts of its components so that the drained regeneration liquid may be re-used. Reuse of the regeneration liquid will create less waste, is environmentally friendly, and reduces the costs.

Examples of anion exchange materials suitable for the present invention include: strong base, cross-linked Type I anion exchange resins, weak base cross-linked anion exchange resins with or without certain fractions of strong basic sites, strong base, cross-linked Type II anion exchange resins, and naturally occurring anion exchangers such as certain clays. The terms strong and weak base anion are known in the art and defined in Analyst, volume 30, No. 1, winter 2023, by Z Liu and F Mir. The structure of the anion exchange resins can be either gel or macro porous. The gel type resins often have higher capacity, while the macro porous type is usually fouling resistant and chemically/mechanically stronger. The anion exchange resins can be styrenic or acrylic polymers having a variety of amine exchange groups including, but not limited to, trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylethanolamine, dimethylamine, tripentylamine and trihexylamine. Strong base anion-exchange resins can be quaternary amine resin containing CH₂N(CH₃)n⁺X~ groups, that is the type known as Type I resin. Type II resins, which contain CH2N[(CH3)2(CH₂CCH₂OH)]⁺X" groups, may also be used effectively. The anion exchange material is said to be in the chloride form when X’ is the chloride ion (Cl"). However, it can be converted to other forms such as hydroxide, bicarbonate, bromide or sulfate. After loading of PFAS species and regeneration, any of these forms can be converted.

Preferred resins for this invention for PFAS loading and regeneration are polystyrene, strong anion exchange resins with macro porous structure and larger quarternaryamine functional groups such as triethylamine, tripropylamine and tripropylamine. Particularly, a resin with uniform resin bead size distribution is preferred due to its excellent hydraulics and better loading/regeneration performance. Examples of commercially available resins suitable for use herein include Lewatit® MonoPlus TP 109, Lewatit® TP 108, Lewatit® TP 108 DW, CALRES 2301 , CALRES 2109, CALRES 2304, SEPLITE® LSI106, SORBIX™ LC3, Amberlite™ PSR2 +, Purofine® PFA694E and ResinTech SIR-110-MP-HP.

The resins may be loaded to any degree with PFAS, but generally the process will be more efficient the higher the loading degree of the resins is. Typically, the resins will be loaded with PFAS in an amount positively correlated to the amount of PFAS in the to-be-treated water. The typical concentration levels of PFAS in the water are ppt or ppb (part per billion) levels, which are much lower than the other common non-PFAS species in the water such as chloride, sulfate, nitrate and naturally-occurring organic species at ppm (part per million) levels. Therefore, the PFAS loading on resin is only a small fraction of the total available loading capacity of the resin. PFAS species normally have much higher selectivity than the other competing species mentioned above, but can still be captured by the resin despite their significantly lower relative concentration in the water.

The method of eluting PFAS with the regenerant solution is typically practiced at room temperature, e.g. at a temperature of 15 to 30^QC. However, the method may also be carried out at a higher temperature for example at a temperature between 30 and 80°C. The elution of the PFAS may be somewhat more efficient at such higher temperature although an elution at higher temperature may increase costs for the recovery.

The method of the present invention may be used to elute a variety of PFAS from a basic anion exchange resin having quaternary ammonium groups. Advantageously, the solutions and methods described herein are able to elute the strongly adsorbed PFOS and PFHxS at unexpected and surprisingly greater amounts than with prior art regenerant solutions utilizing NaCI and methanol.

EXAMPLES

Example 1

A. Experimental:

1 . Materials

Perfluorooctanoic acid (PFOA, 95%) and iron chloride (98%) were purchased from Beantown Chemical Corporation. Perfluorooctanesulfonic acid (PFOS) and Perfluorohexanesulfonic acid (PFHxS) were from Synquest Laboratories Inc. Perfluorobutanoic acid (PFBA, 98%) and Perfluorohexanoic acid (PFHxA) were purchased from Millipore Sigma.

Sodium bicarbonate (99.9%), sodium sulfate anhydrous (99%), sodium nitrate (99%), sodium bromide (99%) and methanol (99.8%) were obtained from Thermo Fisher Scientific. Sodium chloride was ordered from VWR. Ethanol (95%) were purchased from IBI Scientific.

The resin used for this study was Lewatit® MonoPlus TP 109, manufactured by LANXESS Corporation. Lewatit® MonoPlus TP 109 is a macroporous, monodisperse, polystyrene-based anion exchange resin for the selective adsorption of anions, e.g. PFAS (Cl- delivery form, quaternary amine functional group, mean bead size 0.62 mm.

2. Test procedure a. PFAS Feed solution preparation

Two liters PFAS feed solution were prepared gravimetricaliy by adding the needed amount of raw materials to demineralized water. The final feed stock solution contains 0.248ppm PFOA, 0.3ppm PFOS, 0.24ppm PFHxS, 0.128ppm PFBA, 0.188ppm PFHxA, 70ppm bicarbonate, 44ppm sulfate, 57 ppm nitrate and 60ppm chloride. b. Regenerant solution preparation

Three regenerant solutions were prepared gravimetrically. The composition of the regenerant solutions are shown below: c. Column test

The test was performed on a glass column (0.9 inch diameter, and 20 inches long) manufactured by Ace Glasss Inc. The testing procedure is shown below:

Step 1. Load the resin

1). Measure 20 ml resin, loaded into a glass column with demineralized water

2). Feed the 250ml PFAS feed solution at 7ml/min

3). Rinse the resin with 250ml demineralized water at 20ml/min

4). Collect all the effluent in a beaker, then transfer them into two 250ml plastic bottles for analytical testing

Step 2. Regenerate the resin

1). Pass 60ml regenerant solution at 3ml/min

2). Pass 60ml demineralized water at 3ml/min

3). Pass 130ml demineralized water at 10ml/min

4). Collect all samples into a 250ml plastic bottle for analytical testing

Step 3.Reload the resin (repeat step 1)

1). Feed the 250ml PFAS mixture at 7ml/min

2). Rinse the resin with 250ml demineralized water at 20ml/min

3). Collect all the effluent in a beaker, then transfer them into two 250ml plastic bottles for analytical testing

3. Analytical method

The samples were analyzed for the concentrations of PFAS species by the RTI Laboratories Inc. in Livonia, Michigan.

B. Results:

The comparative example (regenerant A) had the conventional methanol and sodium chloride. It could regenerate the carboxylated PFAS species (PFOA, PFBA and PFHxA) very well, but performed quite poorly at the testing condition on the more strongly absorbed sulfonated PFAS species such as PFOS and PFHxS. The regenerant B used ethanol and sodium bromide. It significantly improved the regeneration efficiency of PFOS and PFHxS, while still maintaining high regeneration efficiency of PFOA, PFBA and PFHxA. The regenerant C, contains ferric chloride in methanol/HCI water solution at very acidic pH, showed similar performance to that of the comparative example A. However, Since ferric chloride is very soluble in the acidic methanol/water/HCI mixture, it is expected to perform better at higher dosages.

The following numbered embodiments are meant to be captured by the present disclosure:

1 . A regenerant solution for a per- and polyfluoroalkyl substances (PFAS)-exhausted anion exchange material, the regenerant solution comprising: a bromide or iodide metal salt present at a concentration of about 0.1% to about 60% by weight, preferably about 1 % to about 20% by weight, more preferably about 5% to about 15% by weight of the regenerant solution, ethanol present at about 0.1 % to about 98% by weight, preferably about 30% to about 95% by weight, more preferably about 50% to about 90% by weight of the regenerant solution, and water.

2. The regenerant solution according to embodiment 1, wherein the metal of the bromide or iodide metal salt has a +1 or a +2 charge.

3. The regenerant solution according to embodiment 1, wherein the bromide or iodide metal salt is a bromide metal salt.

4. The regenerant solution according to embodiment 3, wherein the bromide metal salt is selected from sodium bromide (NaBr), potassium bromide (KBr), calcium bromide (CaBr2), magnesium bromide (MgBr2), silver bromide (AgBr), barium bromide (BaBr2), strontium bromide (SrBr2), aluminum bromide (AIBra), lithium bromide (LiBr), and cesium bromide (CsBr), most preferably sodium bromide.

5. A regenerant solution for a per- and polyfluoroalkyl substances (PFAS)-exhausted anion exchange material, the regenerant solution comprising: a tetrachloroferrate complex present at a concentration of about 0.1% to about 20% by weight, preferably about 5% to about 10% by weight of the regenerant solution, methanol or ethanol present at about 0.1 % to about 98% by weight, preferably about 30% to about 95% by weight, more preferably about 50% to about 90% by weight of the regenerant solution, and water.

6. The regenerant solution according to embodiment 5, wherein the pH of the solution is acidic.

7. A method for removal of per- and polyfluoroalkyl substances (PF AS) from a polystyrene anion exchange resin having quaternary ammonium groups, the method comprising: eluting the anion exchange resin with a regenerant solution according to any of the foregoing embodiments.

8. The method according to embodiment 7, wherein the eluting is performed at 1-15 BV/hr.

9. The method according to embodiment 7 or 8, further comprising rinsing the resin with water.

10. The method according to any of embodiments 7-9, wherein Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), Perfluorohexane sulfonate (PFHxS), Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA) loaded on the resin are removed and recovered in the effluent. The method according to any one of embodiments 7 to 10, wherein the regenerant solution contains about 0.1 % to about 60% by weight bromide metal salt, preferably selected from sodium bromide (NaBr), potassium bromide (KBr), calcium bromide (CaBr₂), magnesium bromide (MgBr2), silver bromide (AgBr), barium bromide (BaBr2), strontium bromide (SrBr₂), aluminum bromide (AIBra), lithium bromide (LiBr), and cesium bromide (CsBr), most preferably sodium bromide, based on total weight of the regenerant solution, and about 0.1% to about 98% by weight, based on total weight of the regenerant solution, wherein greater than 80% of the PFOS and PFHxS loaded on the resin are removed and recovered in the effluent.

12. A method of recovery of one or more of Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), Perfluorohexane sulfonate (PFHxS), Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA) from an aqueous composition comprising per- and polyfluoroalkyl substances (PFAS), the method comprising

(i) contacting a polystyrene basic anion exchange resin having quaternary ammonium groups with said aqueous composition;

(ii) separating said aqueous composition from said anion exchange resin; and

(iii) eluting the obtained anion exchange resin with a solution according to any one of of embodiments 1 to 6.

Claims

What is claimed is:

1 . A regenerant solution for a per- and polyfluoroalkyl substances (PFAS)-exhausted anion exchange material, the regenerant solution comprising: a tetrachloroferrate complex present at a concentration of about 0.1% to about 20% by weight, preferably about 5% to about 10% by weight of the regenerant solution, methanol or ethanol present at about 0.1% to about 98% by weight, preferably about 30% to about 95% by weight, more preferably about 50% to about 90% by weight of the regenerant solution, and water.

2. The regenerant solution according to claim 1 , wherein the pH of the solution is acidic.

3. A method for removal of per- and polyfluoroalkyl substances (PFAS) from a polystyrene anion exchange resin having quaternary ammonium groups, the method comprising: eluting the anion exchange resin with a regenerant solution according to claim 1 or 2.

4. The method according to claim 3, wherein the eluting is performed at 1-15 BV/hr.

5. The method according to claim 3 or 4 further comprising rinsing the resin with water.

6. The method according to any of claims 3 to 5, wherein Perfluorooctanoic acid (PFOA),

Perfluorooctane sulfonate (PFOS), Perfluorohexane sulfonate (PFHxS), Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA) loaded on the resin are removed and recovered in the effluent.

7. A method of recovery of one or more of Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), Perfluorohexane sulfonate (PFHxS), Perfluorobutyric acid (PFBA), Perfluorohexanoic acid (PFHxA) from an aqueous composition comprising per- and polyfluoroalkyl substances (PFAS), the method comprising

(i) contacting a polystyrene basic anion exchange resin having quaternary ammonium groups with said aqueous composition;

(ii) separating said aqueous composition from said anion exchange resin; and

(iii) eluting the obtained anion exchange resin with a solution according to claim 1 or 2.