Method for removing PFAS from water

Abstract

The invention relates to a method for removing PFAS from water. A method of removing PFAS from an aqueous phase containing PFAS, comprising adding to the aqueous phase a surfactant composition comprising at least one cationic surfactant such that the surfactant forms micelles in the aqueous phase, and contacting the aqueous phase containing micelles under pressure with an ultrafiltration membrane such that the micelles form micelles in the aqueous phase. To obtain a permeate stream aqueous phase having a reduced concentration of PFAS.

Description

[0001] This application is a divisional application of parent application number 202080046494.0. The parent application was filed on June 25, 2020; the invention is entitled "Method for removing PFAS from water". Technical Field

[0002] This invention relates to a method for removing perfluorinated compounds from water. More specifically, this invention relates to a method for removing PFAS from water by using micellar-enhanced ultrafiltration combined with the addition of cationic surfactants and / or detergents, or a mixture of cationic surfactants and / or detergents with nonionic surfactants and / or detergents. Background Technology

[0003] Ultrafiltration (UF) is a type of membrane filtration in which forces, such as pressure or a concentration gradient, cause separation through a semi-permeable membrane. High molecular weight suspended solids and solutes are retained in the so-called permeate, while water and low molecular weight solutes pass through the membrane in the permeate (filtrate). 1 This separation method is used in industry and research to purify and concentrate macromolecular solutions. 2 Especially protein solutions 3 .

[0004] Ultrafiltration can be used to remove particles and large molecules from raw water to produce drinking water. It has been used to replace existing secondary (coagulation, flocculation, sedimentation) and tertiary (sand filtration and chlorination) filtration systems in water treatment plants, or as a stand-alone system in isolated areas with growing populations. 4 It is used in the dairy processing industry to concentrate milk protein and remove water from milk. It is also used in the biotechnology industry to concentrate proteins. 5 .

[0005] Micellar-enhanced ultrafiltration (hereinafter also known as MEUF) is known as a recently developed and powerful separation method for removing a variety of contaminants, such as heavy metals (e.g., lead, cadmium, or zinc), toxic organic substances (e.g., phenol, dibutyl phosphate, tributyl phosphate, or trihalomethanes), and lower molecular weight contaminants, including organic dyes. 6, 8 .

[0006] In MEUF (Mean-to-Fluid) detergents are added to water at a concentration higher than the detergent's critical micelle concentration. When the detergent forms micelles, the hydrophobic portions of the detergent molecules aggregate and form hydrophobic spaces, while the hydrophilic groups of the detergent molecules remain exposed to water. 9This forms a typically spherical structure with a hydrophilic surface and a hydrophobic interior. The weight of these spherical micelles is at least 60,000 Daltons, making it possible to separate detergent micelles via ultrafiltration. The hydrophilic groups on the micelle surface create phase separation between the micelle's hydrophobic interior and water. Since organic pollutants are generally very hydrophobic, they typically prefer to reside within the micelles, which is the basis for MEUF's removal of pollutants. 7 .

[0007] PFAS (per- and polyfluoroalkyl substances) is a collective term for more than 3,000 industrially produced chemicals.

[0008] PFAS can be classified into (1) long-chain PFAA, (2) short-chain PFAA, (3) non-polymeric and polymeric fluoropolymer-based products, and (4) fluoroplastics and fluoropolymers; wherein long-chain PFAA includes perfluoroalkyl sulfonic acids (PFSA) with a carbon chain length of 6 and above and perfluorocarboxylic acids (PFCA) with a carbon chain length of 8 and above; and short-chain PFAA includes PFSA with a carbon chain length of 5 and below and PFCA with a carbon chain length of 7 and below.

[0009] The most common PFAS are perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, 6:2 fluoropolymer sulfonates, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, and 4:2 fluoropolymer sulfonates. 8:2 fluoropolymer sulfonates, perfluorooctane sulfonamides, N-methylperfluorooctane sulfonamides, N-ethylperfluorooctane sulfonamides, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, perfluorooctane sulfonamide acetate, N-methylperfluorooctane sulfonamide acetate, N-ethylperfluorooctane sulfonamide acetate, 7H-perfluoroheptanoic acid, perfluoro-3,7-dimethyloctanoic acid, and isomers, homologues, and other arrangements of these substances.

[0010] The most common measurement for PFAS is the so-called "PFAS Sum 11", which refers to the 11 most common PFAS, namely: perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluoropolymer sulfonate.

[0011] PFAS are used globally in a wide range of products, such as fire extinguishers and impregnating agents. PFAS are widely dispersed in the environment; they are persistent, and some are toxic. PFAS-contaminated land has been found in many parts of the world, where PFAS have leaked into groundwater and drinking water reservoirs. Recent studies have indicated several health problems associated with PFAS, and the threshold for PFAS in drinking water is currently under investigation. 10-12 .

[0012] PFAS are all man-made, and their supply to the natural world comes entirely from human activities. They are present in numerous production processes globally, such as as fabric protectants. For example, the most common point source of PFAS in the Swedish environment is fire-fighting foam used at airports. Military airports are the largest sources of PFAS leaks into the environment, followed by civilian airports. Because PFAS do not degrade in nature, and several PFAS are bioaccumulative, proactive measures must be taken to combat this pollution in addition to limiting their use.

[0013] PFAS can enter the human body through contaminated drinking water, through food such as fish and livestock, through irrigation of crops with contaminated water, and through inhalation of dust. 13 PFAS may cause liver and reproductive toxicity in humans. The largest study in the United States involved approximately 60,000 people who received high levels of the fluoride PFOA (perfluorooctanoic acid) from their drinking water. The study concluded that PFOA exposure in the studied population was potentially linked to high cholesterol levels, hypertension during pregnancy, ulcerative colitis, thyroid disease, and testicular and kidney cancer (C8 Science Panel 2013).

[0014] The most common water-soluble PFAS in the environment have negatively charged portions, which makes them soluble in water. Common PFAS such as perfluorobutyric acid (PFBA), perfluorooctane sulfonate (PFOS), and fluoropolymer sulfonates are present in high concentrations at most pollution sites. These perfluorinated molecules are extremely difficult to break down, cannot be removed by biological wastewater treatment methods, and are resistant to oxidation from ozone water treatment.

[0015] A common method for removing PFAS from water is by using different types of carbon filtration, typically granular activated carbon (GAC) filtration. Carbon filtration is effective for long-chain PFAS molecules such as perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorooctane sulfonic acid, 6:2 fluoropolymer sulfonates, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, 4:2 fluoropolymer sulfonates, 8:2 fluoropolymer sulfonates, perfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide, N-ethylperfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, perfluorooctane sulfonamide acetate, N-methylperfluorooctane sulfonamide acetate, N-ethylperfluorooctane sulfonamide acetate, 7H-perfluoroheptanoic acid, and perfluoro-3,7-dimethyloctanoic acid. However, GAC and other carbon filtration methods are less efficient when dealing with shorter PFAS molecules such as perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluoropentanesulfonic acid, and perfluoroheptanesulfonic acid. If the wastewater stream contains high concentrations of low molecular weight PFAS molecules, the carbon filter must be replaced at more frequent intervals; if the water also contains high levels of organic matter, this necessitates even more frequent replacements of the carbon filter. 14 .

[0016] Another recommended method for treating PFAS-contaminated wastewater is reverse osmosis (RO). RO can efficiently separate individual metal ions from water and has been proven to remove all types of PFAS from water. 15 However, a drawback of RO is that it cannot filter water with high ion concentrations. In fact, because RO relies on permeate flow across the membrane, very little permeate flow can be obtained at atmospheric pressure if the salt concentration in the treated water is high. RO efficiency can be quite high, but rarely exceeds 90%, meaning that RO can reduce the volume of waste by a maximum of 90%; more typically, this is around 75-80%. RO consumes more energy compared to ultrafiltration. Another disadvantage of RO is that it usually requires an ultrafiltration unit as a pre-filtration step, increasing the complexity of the system.

[0017] There seems to be an urgent and growing need for effective methods to remove PFAS from water. Summary of the Invention

[0018] This paper discloses a method for removing PFAS from water. This method is generally advantageous for all types of PFAS with improved efficiency and reduced waste volume, regardless of, for example, the molecular weight of the PFAS. This method can also generally be used to remove PFAS from any type of PFAS-containing water, such as effluent, leachate, process water, groundwater, etc., i.e., generally any type of PFAS-containing aqueous phase. Therefore, based on the reduced PFAS contamination, the method of the present invention can obtain water with improved purity.

[0019] Therefore, this paper discloses a method for removing PFAS from an aqueous phase containing PFAS, including (i) adding a surfactant composition comprising at least one cationic surfactant to the aqueous phase, such that the surfactant forms micelles in the aqueous phase; and (ii) The micelle-containing aqueous phase is brought into contact with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS.

[0020] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (i) Adding a surfactant composition comprising at least one cationic surfactant to the aqueous phase to cause the surfactant to form micelles in the aqueous phase; (ii) The micelle-containing aqueous phase is contacted with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS; and optionally (iii) Repeat (i) and (ii) at least once.

[0021] In some implementations, (i) and (ii) are repeated at least once. In some implementations, (i) and (ii) are repeated once. In some implementations, (i) and (ii) are repeated more than once.

[0022] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (i) Adding a surfactant composition comprising at least one cationic surfactant to the aqueous phase, such that the surfactant forms micelles in the aqueous phase. (ii) The micelle-containing aqueous phase is contacted with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS. (iii) Optionally determine the concentration of one or more PFAS in the aqueous phase of the permeate stream having a reduced concentration of PFAS, and (iv) If the determined concentration is higher than the predetermined threshold, optionally repeat (i) - (iii).

[0023] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (i) Adding a surfactant composition comprising at least one cationic surfactant to the aqueous phase, such that the surfactant forms micelles in the aqueous phase. (ii) The micelle-containing aqueous phase is contacted with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS. (iii) Determine the concentration of one or more PFAS in the aqueous phase of the permeate stream with reduced PFAS concentration, and (iv) If the determined concentration is higher than the predetermined threshold, repeat (i) - (iii).

[0024] The method of the present invention allows various types of water to be purified from PFAS to very low or even negligible residual levels of PFAS, which is important given the persistence of PFAS in the environment and its toxic effects on animals and humans. Attached Figure Description

[0025] Figure 1A This schematically illustrates a surfactant molecule with a hydrophilic head and a hydrophobic tail. Figure 1B The diagram illustrates a micelle structure formed by several surfactant molecules, which has a hydrophilic surface and a hydrophobic interior.

[0026] Figure 2 The chemical structure of the most common PFAS is shown, namely "PFAS Sum 11".

[0027] Figure 3A This explains the general principle of removing PFAS from water by adding a surfactant followed by ultrafiltration. Figure 3B This describes micelles carrying PFAS on the surface and inside the micelles, as formed during this process.

[0028] Figure 4 This is a block diagram schematically illustrating an ultrafiltration procedure for removing PFAS from water containing PFAS, as disclosed herein.

[0029] Figure 5This is a bar chart showing the remaining portion of PFAS, expressed as % of the residual PFAS Sum 11 in ultrafiltered water with an initial PFAS Sum 11 concentration of 25.13 μg / L, without surfactant (Ref. Example 10) or with the addition of anionic surfactant (Ref. Example 11), nonionic surfactant (Ref. Example 12), a mixture of anionic and nonionic surfactants (Ref. Example 13), cationic surfactant (Example 14), or a mixture of cationic and nonionic surfactants (Examples 15 and 16).

[0030] Figure 6 This is a graph showing the concentration (in μg / L) of PFAS Sum 11 in water initially containing 12 μg / L of PFAS Sum 11, with or without the addition of a surfactant, or with the addition of different amounts of the cationic surfactant cetyltrimethylammonium chloride (CTAC).

[0031] Figure 7 This is a bar chart showing the remaining portion of PFAS, expressed as % of the residual PFAS in water with an initial concentration of 69 μg / L after one (1), two (2), or three (3) repetitions of the method in the presence of hexadecyltrimethylammonium chloride (CTAC) as a surfactant. Detailed Implementation

[0032] definition As used herein, a "surfactant" is an organic compound that reduces the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants are amphiphilic compounds, meaning they contain both a hydrophobic portion ("hydrophobic tail") and a hydrophilic portion ("hydrophilic head" or "polar head") (see [link to relevant documentation]). Figure 1A ).

[0033] Most commonly, surfactants are classified according to their hydrophilic heads. "Nonionic surfactants" have no charged groups on their heads; "cationic surfactants" have a net positive charge on their hydrophilic heads, while "anionic surfactants" have a net negative charge on their hydrophilic heads.

[0034] As used herein, “micelle” refers to an aggregate or supramolecular assembly of surfactant molecules dispersed in a liquid phase. Typical micelles in aqueous solutions aggregate with the hydrophilic portion (“hydrophilic head”) of the surrounding liquid phase, isolating the hydrophobic portion (“hydrophobic tail”) at the micelle center. See [link to relevant documentation] Figure 1B .

[0035] The “critical micelle concentration” (“CMC”) used in this article refers to the concentration of surfactant in the liquid phase in which micelle formation occurs.

[0036] The term "hydrophilic" as used in this article refers to the property of having an affinity for water, that is, the tendency to dissolve in water.

[0037] As used in this article, "hydrophobic" refers to a property that tends to repel water or cannot mix with water.

[0038] As used herein, “ultrafiltration” refers to a method in which a liquid is typically brought into contact with a semi-permeable membrane (ultrafiltration membrane) containing pores of a specific size (cutoff size) at a certain pressure head, wherein molecules or complexes smaller than the membrane cutoff size can pass through the pores, while molecules or complexes larger than the membrane cutoff size cannot pass through the pores and are retained on the upstream side of the membrane.

[0039] As used herein, "residue" refers to molecules or complexes that do not pass through the pores of a semipermeable membrane during ultrafiltration but remain on the upstream side of the membrane.

[0040] As used in this article, "permeate" refers to molecules or complexes that have passed through the pores of a semipermeable membrane during ultrafiltration.

[0041] The term “cutoff size” or “molecular weight cutoff” used in this article for ultrafiltration membranes refers to the molecular weight of molecules or particles that are cut off by the membrane at a rate of 90%.

[0042] Dalton (Da) is equal to 12 One-twelfth the mass of a carbon atom. This is approximately 1.66 × 10⁻⁶. -27 kg.

[0043] The unit kDa corresponds to 10 3 Dalton.

[0044] The “CTAC” used in this article refers to hexadecyltrimethylammonium chloride.

[0045] The “CTAB” used in this article refers to hexadecyltrimethylammonium bromide.

[0046] As used in this article, "SDS" refers to sodium dodecyl sulfonate.

[0047] As used in this article, "PFAS Sum 11" refers to perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluoropolymer sulfonates.

[0048] As used herein, "PFAS" refers to perfluoroalkyl (or polyfluoroalkyl) substances. Therefore, while the term "PFAS" is a collective reference for a class of compounds, it can be used herein to refer to only one such compound, as well as a mixture of more than one such compound. For example, PFAS mentioned herein may include, for instance, perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, 6:2 fluoropolymer sulfonates, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, 4:2 fluoropolymer sulfonates, One or more of the following: 8:2 fluoropolymer sulfonates, perfluorooctane sulfonamides, N-methylperfluorooctane sulfonamides, N-ethylperfluorooctane sulfonamides, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, perfluorooctane sulfonamide acetate, N-methylperfluorooctane sulfonamide acetate, N-ethylperfluorooctane sulfonamide acetate, 7H-perfluoroheptanoic acid, and perfluoro-3,7-dimethyloctanoic acid, as well as isomers, homologues, and other variants and combinations thereof.

[0049] The term "PFAA" refers to perfluoroalkyl acids (or polyfluoroalkyl acids).

[0050] The term "PFSA" refers to perfluoroalkyl sulfonic acid (or polyfluoroalkyl sulfonic acid).

[0051] The term "PFCA" refers to perfluoroalkyl carboxylic acids (or polyfluoroalkyl carboxylic acids).

[0052] Generally, as used herein, the term PFAS does not refer to polymeric substances; that is, as is commonly used herein, the term PFAS refers to non-polymeric PFAS, especially water-soluble PFAS.

[0053] Therefore, as used herein, the term PFAS generally refers to one or more non-polymeric PFAS, such as long-chain PFAA, short-chain PFAA, and products based on non-polymeric fluoropolymers.

[0054] Water containing PFAS The aqueous phase treated by the method of the present invention can be any type of PFAS-containing water, such as PFAS-contaminated water, effluent, leachate, process water, groundwater and other types of water and / or aqueous solutions containing PFAS.

[0055] Typically, the aqueous phase containing PFAS to be treated according to the present invention is not an emulsion of PFAS in water. Typically, the aqueous phase contains PFAS dissolved therein.

[0056] The concentration of PFAS present in the aqueous phase to be treated can vary over time, for example, from very low to high. Moreover, without reducing the effectiveness of the method of the present invention, the specific types of PFAS present in the aqueous phase to be treated may be unknown or may vary.

[0057] In some embodiments, the aqueous phase to be treated by the method of the present invention comprises perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, 6:2 fluoropolymer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, and 4:2 Fluoropolymer sulfonates, 8:2 fluoropolymer sulfonates, perfluorooctane sulfonamides, N-methylperfluorooctane sulfonamides, N-ethylperfluorooctane sulfonamides, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, perfluorooctane sulfonamide acetate, N-methylperfluorooctane sulfonamide acetate, N-ethylperfluorooctane sulfonamide acetate, 7H-perfluoroheptanoic acid and perfluoro-3,7-dimethyloctanoic acid, and isomers, homologues and other arrangements of these substances.

[0058] In some embodiments, the aqueous phase to be treated by the method of the present invention comprises one or more of perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluoropolymer sulfonate.

[0059] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial total concentration of at least 10 g / L, or at least 5 g / L, or at least 2 g / L, or at least 1 g / L, or at least 500 mg / L, or at least 200 mg / L, or at least 100 mg / L, or at least 50 mg / L, or at least 20 mg / L, or at least 10 mg / L, or at least 5 mg / L, or at least 2 mg / L, or at least 1 mg / L, or at least 500 μg / L, or at least 200 μg / L, or at least 100 μg / L, or at least 50 μg / L, or at least 20 μg / L, or at least 10 μg / L, or at least 5 μg / L, or at least 2 μg / L, or at least 1 μg / L, or at least 0.5 μg / L, or at least 0.2 μg / L, or at least 0.1 μg / L.

[0060] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial total concentration of up to 10 g / L, or up to 5 g / L, or up to 2 g / L, or up to 1 g / L, or up to 500 mg / L, or up to 200 mg / L, or up to 100 mg / L, or up to 50 mg / L, or up to 20 mg / L, or up to 10 mg / L, or up to 5 mg / L, or up to 2 mg / L, or up to 1 mg / L, or up to 500 μg / L, or up to 200 μg / L, or up to 100 μg / L, or up to 50 μg / L, or up to 20 μg / L.

[0061] In some embodiments, the water treated by the method of the present invention contains PFAS at an initial concentration ranging from any of the aforementioned lower limits to any of the aforementioned upper limits, for example, initial concentration ranges of 0.1 μg / L to 10 g / L, 0.1 μg / L to 5 g / L, 0.1 μg / L to 2 g / L, 0.1 μg / L to 1 g / L, 0.1 μg / L to 500 mg / L, 0.1 μg / L to 200 mg / L, 0.1 μg / L to 100 mg / L, 0.1 μg / L to 50 mg / L, 0.1 μg / L to 20 mg / L, 0.1 μg / L to 10 mg / L, 0.1 μg / L to 5 mg / L, 0.1 μg / L to 2 mg / L, 0.1 μg / L to 1 g ... mg / L, 0.1 μg / L to 500 μg / L, 0.1 μg / L to 200 μg / L, 0.1 μg / L to 100 μg / L, 0.1 μg / L to 50 μg / L, or 0.1 μg / L to 20 μg / L.

[0062] In some of the above embodiments, the water treated by the method of the present invention contains PFAS at an initial concentration of at least 0.2 μg / L, or at least 0.5 μg / L, or at least 1 μg / L, or at least 2 μg / L, or at least 5 μg / L, or at least 10 μg / L.

[0063] Therefore, in some embodiments, the water treated by the method of the present invention contains PFAS with an initial concentration ranging from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 10 g / L, and from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 5 g / L.

[0064] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration ranging from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 2 g / L, and from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 1 g / L.

[0065] In some embodiments, the water treated by the method of the present invention contains PFAS at an initial concentration ranging from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 500 mg / L, and from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 200 mg / L.

[0066] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 100 mg / L.

[0067] In some embodiments, the water treated by the method of the present invention contains PFAS at an initial concentration ranging from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 50 mg / L, and from 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 20 mg / L.

[0068] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 10 mg / L.

[0069] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 5 mg / L.

[0070] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 2 mg / L.

[0071] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 1 mg / L.

[0072] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 500 μg / L.

[0073] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 200 μg / L.

[0074] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 100 μg / L.

[0075] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 50 μg / L.

[0076] In some embodiments, the water treated by the method of the present invention contains PFAS in an initial concentration range of 0.2 μg / L, or 0.5 μg / L, or 1 μg / L, or 2 μg / L, or 5 μg / L, or 10 μg / L to 20 μg / L.

[0077] In some embodiments, the initial concentration of PFAS is determined by measuring the initial concentration of at least one PFAS selected from PFAS Sum 11 and taking the measured value as the total initial PFAS concentration.

[0078] In some implementations, the initial concentration of PFAS is determined by measuring the initial total concentration of PFAS Sum 11 and taking the measured value as the total initial PFAS concentration.

[0079] In some implementations, the initial concentration of PFAS is determined by measuring the initial concentration of PFAS Sum 11, multiplying the measured value by a factor k (e.g., factor k is 1.2-10, 1.2-5, 1.2-4, 1.2-3, 1.2-3, 1.2-2, or 1.2-1.5), and taking the calculated value as the total initial PFAS concentration. For each type of water, a specific factor k can be determined; for example, for a particular type of water, this is achieved by determining the average total PFAS concentration in the water (e.g., excluding polymerized PFAS) and the average PFAS Sum 11 concentration.

[0080] Surfactant Composition To achieve efficient separation of PFAS from the aqueous phase, a surfactant composition containing at least one cationic surfactant is mixed with the aqueous phase to allow micelles to form in the aqueous phase.

[0081] As used herein, the term "surfactant composition" may refer to a specific surfactant compound or a mixture of surfactant compounds optionally in a liquid carrier such as water. Therefore, in some embodiments, the method of the present invention includes (i) adding a cationic surfactant to an aqueous phase containing PFAS to form micelles in the aqueous phase, and (ii) subjecting the aqueous phase to ultrafiltration, for example as described herein.

[0082] In some other embodiments, the method of the present invention includes (i) adding a mixture of cationic surfactants to an aqueous phase containing PFAS to form micelles in the aqueous phase, and (ii) subjecting the aqueous phase to ultrafiltration, for example as described herein.

[0083] In some embodiments, in addition to a cationic surfactant or a mixture of cationic surfactants, the surfactant composition also comprises a nonionic surfactant or a mixture of nonionic surfactants. For example, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 100:1 to 1:100, or 50:1 to 1:50, or 20:1 to 1:20, or 10:1 to 1:10, or 5:1 to 1:5, such as 2:1 to 1:2.

[0084] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 100:1 to 1:1, or 50:1 to 1:1, or 20:1 to 1:1, or 10:1 to 1:1, or 5:1 to 1:1, for example 2:1 to 1:1.

[0085] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 100:1 to 2:1, or 50:1 to 2:1, or 20:1 to 2:1, or 10:1 to 2:1, or 5:1 to 2:1.

[0086] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 100:1 to 5:1, or 50:1 to 5:1, or 20:1 to 5:1, or 10:1 to 5:1.

[0087] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 1:1 to 1:100, or 1:1 to 1:50, or 1:1 to 1:20, or 1:1 to 1:10, or 1:1 to 1:5, for example 1:1 to 1:2.

[0088] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 1:2 to 1:100, or 1:2 to 1:50, or 1:2 to 1:20, or 1:2 to 1:10, or 1:2 to 1:5.

[0089] In some other embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 1:5 to 1:100, or 1:5 to 1:50, or 1:5 to 1:20, or 1:5 to 1:10.

[0090] In some embodiments, the surfactant composition contains only cationic surfactants.

[0091] cationic surfactants Any cationic surfactant or mixture of cationic surfactants is generally considered to be usable in the methods of the present invention. As described above, the surfactant comprises a hydrophobic portion and a hydrophilic portion. The hydrophobic portion of the surfactant used in the present invention is generally a C4-C20 hydrocarbon group, such as an alkyl group containing 4-20 carbon atoms, for example, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, and eicosyl. As used herein, the hydrophilic portion of the cationic surfactant may be selected, for example, from ammonium, methylammonium, dimethylammonium, trimethylammonium, hydroxyethylammonium, methylhydroxyethylammonium, and dimethylhydroxyethylammonium.

[0092] For example, in some embodiments, the surfactant composition comprises the general formula R4N + Quaternary ammonium salts (e.g., as Cl) - or Br - A salt), wherein at least one R is a hydrophobic moiety, such as a C10-C20 alkyl chain, and wherein the R group may additionally contain NC or OC bonds, and may be branched or linear, substituted or unsubstituted, saturated or unsaturated, and aromatic or aliphatic. Examples of cationic surfactants are, for example, C10-C20 alkyltrimethylammonium salts, such as C10-C20 alkyltrimethylammonium halide.

[0093] In some embodiments, the surfactant composition comprises a cationic surfactant selected from hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride. However, it should be understood that the invention is not limited to any particular type of cationic surfactant. Furthermore, as noted above, unless otherwise stated or apparent from the context, references to "cationic surfactant" should also be understood to refer to mixtures of cationic surfactants.

[0094] In addition, cationic surfactants can also be cationic polymer surfactants, such as those described in RA Wessling & D. M. Pickelman (1981) Cationic Polymeric Surfactants, Journal of Dispersion Science and Technology, 2:2-3, 281-313, the contents of which are incorporated herein by reference in their entirety.

[0095] In some embodiments, the surfactant composition comprises hexadecyltrimethylammonium halide, such as CTAB or CTAC.

[0096] In some embodiments, the surfactant composition contains only cationic surfactants. In some embodiments, the surfactant composition is one or more cationic surfactants in a liquid carrier, such as one or more cationic surfactants in an aqueous liquid carrier.

[0097] Nonionic surfactants Examples of nonionic surfactants are alcohol ethoxylates and alkylphenol ethoxylates.

[0098] Alcohol ethoxylates can be derived from the general formula R(OCH2CH2). n OH indicates that R can be, for example, a C9-C18 straight-chain or branched alkyl group, and n can be an integer from 1 to 40, for example 5-20. Alkylphenol ethoxylated surfactants can be derived from the general formula R-(C6H4)-(OCH2CH2). n OH indicates that R can be, for example, a C8-C16 straight-chain or branched alkyl group, and n can be an integer from 1 to 30, for example 5-15.

[0099] For the purposes of this invention, unless otherwise stated or obvious from the context, references to "nonionic surfactant" should also be understood to include mixtures of nonionic surfactants.

[0100] Ultrafiltration membrane Ultrafiltration membranes are typically specified to have a specific cutoff size or molecular weight. Many types of ultrafiltration membranes (or filters) exist, made from a variety of materials, such as polyethersulfone, regenerated cellulose, or ceramic materials. In this invention, any type of ultrafiltration technology can be used. Ultrafiltration can be performed in a helically wound membrane via cross-flow filtration, where a feed stream is introduced into the membrane element under pressure and passes over the membrane surface in a controlled flow path, wherein permeate passes through the membrane, and repelled material can be flushed away as effluent.

[0101] Another commonly used ultrafiltration device uses hollow fiber membranes. These membranes are formed into long, very thin tubes or fibers (typically 0.6–2 mm in diameter) that are sealed at both ends to connectors. Hundreds of these fibers, each with an inlet and outlet connector, are called a “bundle” or “tube” and can be bundled together to form a “module.” The feed solution typically flows through one end of the fiber while the opposite end is completely or partially closed, forcing fluid through the membrane. Within the membrane, the fluid is collected in the tubular region surrounding the fiber, leaving the suspended material on the inner side of the membrane.

[0102] Therefore, in the method of the present invention, any type of ultrafiltration membrane can be used, such as spiral wound membranes, tubular membranes, hollow fiber membranes or flat sheet membranes made of materials such as cellulose acetate (CA), polyvinylidene fluoride (PVDF), polyacrylonitrile, polypropylene, polysulfone (PS), polyethersulfone (PES) or other polymers, which may also be made of ceramic materials.

[0103] Preferably, the ultrafiltration membrane has a molecular weight cutoff of no more than 100,000 Daltons (100 kDa), for example, preferably no more than 50 kDa, even more preferably no more than 30 kDa, no more than 25 kDa, no more than 20 kDa, no more than 15 kDa, or no more than 10 kDa, for example, 1-100 kDa, 5-50 kDa, 1-30 kDa, 1-25 kDa, 1-20 kDa, 1-15 kDa, or 1-10 kDa.

[0104] method In the method of the present invention, a surfactant composition as defined herein is mixed with an aqueous phase containing PFAS to form surfactant-containing micelles.

[0105] The amount of surfactant composition added is such that micelles are formed, i.e., at least the critical micelle concentration (CMC) of the surfactant composition in the aqueous phase is reached. In some embodiments, an excess of surfactant composition may be added, for example, an amount 10-100% (e.g., 20-50%) higher than the estimated amount required to reach the CMC.

[0106] Surfactant compositions can be added to an aqueous phase as a liquid solution or in solid form (e.g., powder or granules), such as as a salt to be dissolved in the aqueous phase. Micelle formation is considered a rapid process as long as the CMC is reached. Furthermore, once micelles are formed, the micelle-containing aqueous phase can be ultrafiltered without any significant delay in order to provide an emulsion of micelles in the PFAS-containing aqueous phase; that is, the partition of PFAS into the micelle phase is considered to occur quite rapidly, for example, within minutes (e.g., 1–10 minutes, or 1–5 minutes, or 2–5 minutes) or less.

[0107] The amount of surfactant composition to be added to any particular type of water can be determined by those skilled in the art, for example by collecting representative water samples and determining PFAS in the presence of the selected surfactant composition at a concentration of at least CMC before and after ultrafiltration, optionally testing several different surfactant compositions and / or different surfactant concentrations. Generally, the concentration of PFAS present in any water to be treated is considerably low compared to the CMC of any surfactant, and therefore the surfactant composition of the present invention is considered effective in the method of the present invention at the CMC.

[0108] An aqueous phase contaminated with PFAS, containing a surfactant composition as defined herein at a concentration higher than the CMC, is contacted under pressure with an ultrafiltration membrane to obtain a permeate stream and a residual stream. The residual stream will have a higher PFAS concentration than the PFAS-contaminated aqueous phase entering the ultrafiltration unit, while the aqueous permeate stream will have a lower PFAS concentration. PFAS are expected to be trapped within the micelles and on the surface of the micelles, and thus substantially retained in the residual stream.

[0109] In some embodiments of the invention, the water-based surfactant composition containing PFAS is treated repeatedly using ultrafiltration as described herein. Thus, in some embodiments, the permeate containing a reduced amount of PFAS, compared to the water stream entering the ultrafiltration unit, will undergo additional treatment with a surfactant composition containing a cationic surfactant and optionally a nonionic surfactant, which may be the same as or different from the previously added surfactant composition, and will subsequently be contacted again with the ultrafiltration unit, which may be the same as or different from the unit used in the previous filtration steps.

[0110] In some implementations, a recirculation system is used to achieve repetition, allowing the permeate to be recirculated multiple times through an ultrafiltration unit containing an ultrafiltration unit, each time adding a larger amount of surfactant composition than required to achieve CMC in the aqueous phase, and each time separating PFAS-rich residue and permeate with reduced PFAS concentration.

[0111] Recirculation can be repeated a predetermined number of times, such as 1-5 times, or 1-3 times (although even higher recirculations may be used if necessary, such as in the case of heavily contaminated water), or can be repeated until the analysis of the ultrafiltration permeate indicates that a satisfactory low PFAS concentration has been achieved.

[0112] Therefore, in some embodiments, methods for removing PFAS from an aqueous phase containing PFAS include (i) adding a surfactant composition to the aqueous phase, the surfactant composition comprising at least one cationic surfactant, to cause the surfactant to form micelles in the aqueous phase; and (ii) The micelle-containing aqueous phase is brought into contact with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS.

[0113] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (1) A surfactant composition is added to the aqueous phase, the surfactant composition comprising at least one cationic surfactant, such that the surfactant forms micelles in the aqueous phase; (2) The aqueous phase containing micelles is brought into contact with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a reduced concentration of PFAS. (3) Adding a surfactant composition to the aqueous phase having a reduced concentration of PFAS, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase having a reduced concentration of PFAS; (4) The aqueous phase containing micelles (which has a reduced concentration of PFAS) is contacted with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a further reduced concentration of PFAS; and optionally Repeat (3) and (4) once or more, for example, 1, 2, 3 or 4 times.

[0114] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (1) Add a surfactant composition to the aqueous phase containing PFAS at an initial concentration of c0, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase; (2) The micelle-containing aqueous phase is contacted with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a reduced PFAS concentration c1; optionally (3) Adding a surfactant composition to the aqueous phase having a reduced PFAS concentration c1, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase having a reduced PFAS concentration c1; and (4) The micelle-containing aqueous phase with a reduced PFAS concentration c1 is contacted with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a further reduced PFAS concentration c2; and (5) Optionally repeat (3) and (4) once or more, for example, repeat 1, 2, 3 or 4 times, for example, a pre-selected number of times, or for example until Cn + 1 is substantially equal to Cn.

[0115] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (1) Add a surfactant composition to the aqueous phase containing PFAS at an initial concentration of c0, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase; (2) The aqueous phase containing micelles is brought into contact with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a reduced PFAS concentration c1. (3) Adding a surfactant composition to the aqueous phase having a reduced PFAS concentration c1, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase having a reduced PFAS concentration c1. (4) The micelle-containing aqueous phase with a reduced PFAS concentration c1 is contacted with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a further reduced PFAS concentration c2; and optionally... Repeat (3) and (4) once or more, for example, repeat 1, 2, 3 or 4 times or more, for example, the number of times pre-selected, or for example until Cn + 1 is essentially equal to Cn.

[0116] In some implementations, methods for removing PFAS from an aqueous phase containing PFAS include (1) Adding a surfactant composition to the aqueous phase containing PFAS at an initial concentration of c0, wherein the surfactant composition comprises at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase; (2) The aqueous phase containing micelles is brought into contact with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a reduced PFAS concentration c1. (3) Determine the concentration of one or more PFAS in the permeate aqueous phase having a reduced concentration of PFAS; and optionally (4) If the concentration determined in (3) is higher than a threshold, a surfactant composition is added to the aqueous phase having a reduced PFAS concentration c1, the surfactant composition comprising at least one cationic surfactant to allow the surfactant to form micelles in the aqueous phase having a reduced PFAS concentration c1; and (5) The micelle-containing aqueous phase with a reduced PFAS concentration c1 is contacted with an ultrafiltration membrane under pressure to obtain an aqueous permeate stream with a further reduced PFAS concentration c2; and optionally... Repeat (3) and (4) once or more, for example, 1, 2, 3 or 4 times or more, such as the number of times pre-selected, or until the concentration determined in (3) is not greater than the threshold.

[0117] By repeatedly treating PFAS-contaminated water with the surfactant composition defined herein, PFAS can be removed by ultrafiltration to below the detection limit for PFAS analysis in several replicates.

[0118] In some embodiments, in the step of determining the concentration of one or more PFAS in the aqueous phase (e.g., the permeate aqueous phase), as described above, the concentration of at least one PFAS selected from PFAS Sum 11 is determined, for example, the total concentration of PFAS Sum 11 is determined.

[0119] The surfactant composition added in each step may be as generally described above, for example, it may be a cationic surfactant such as CTAB or CTAC or a concentrated aqueous solution thereof.

[0120] In some other embodiments, it is contemplated that instead of recirculating the aqueous phase through the same ultrafiltration membrane, several ultrafiltration devices in series can be used for ultrafiltration. These ultrafiltration devices may be of the same type or of different types, such as having different molecular weight cutoff sizes, in a method that includes adding a micelle-forming surfactant composition to the permeate stream exiting one ultrafiltration device. Thus, for each point of addition, the micelle-forming amount and surfactant may be different.

[0121] In addition, combinations of recirculation within the same ultrafilter and a series of ultrafiltration units are also possible.

[0122] The principle of this invention is as follows Figure 3A In general, the surfactant composition described herein (“surfactant”) is added to water 1 containing PFAS at a concentration that allows micelle formation. The PFAS present in the aqueous phase are expected to be anionic compound 2 and nonionic compound 3. The anionic PFAS 2 will bind to the micelles on the micelle surface as the counterion of the cationic surfactant within the micelles, while the nonionic PFAS 3 will substantially partition into the hydrophobic spaces within the micelles to form PFAS-loaded micelles 4, as well as… Figure 3B As shown. Compared to ultrafiltration, this reaction is considered rapid, so the solution can be ultrafiltered essentially immediately through an ultrafiltration membrane 5 with a molecular weight cutoff smaller than the size of the micelles formed 4, to obtain a osmotic residue 6 with an increased PFAS concentration and a permeate 7 (not shown) with a decreased PFAS concentration.

[0123] An advantageous feature of the method of the present invention is that the residual amount of the treated water is very small, typically less than 15% or even less than 10% of the inflow volume of water. This reduces the problems inherent in large volumes of wastewater.

[0124] Advantageously, according to the present invention, the initial concentration of PFAS in water can be reduced by at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 98%, at least 99% or even higher, for example, to the detection level.

[0125] The efficiency of PFAS removal from PFAS-contaminated water depends not only on the choice of surfactant but also on the molecular weight cutoff of the selected ultrafiltration membrane. Typically, the optimal molecular weight cutoff for ultrafiltration membranes has been found to be below 100 kDa, more preferably below 50 kDa, and even more preferably below 30 kDa, for example, 5–20 kDa. For instance, membranes with a molecular weight cutoff of 5–100 kDa, or 5–50 kDa, such as 5–30 kDa, can be used.

[0126] The present invention has been demonstrated to work in small-scale ultrafiltration devices used in the laboratory, such as membrane-filled centrifuge tubes or tangential flow ultrafiltration devices used in the laboratory, capable of processing 100 ml to several liters, as well as on a large scale in ultrafiltration devices used to treat several cubic meters of PFAS-contaminated water.

[0127] The present invention is illustrated by the following non-limiting embodiments. For comparison, reference embodiments not based on the invention are also described. Example

[0128] Material All surfactants used were commercially available, high-quality products obtained from commercial chemical suppliers, for example, in the form of commercial detergents. The water tested was contaminated water obtained from various PFAS-contaminated sites located in Sweden. The ultrafiltration membrane was a commercially available membrane obtained from the supplier of the ultrafiltration equipment.

[0129] PFAS analysis At each step, the water is analyzed by an authorized environmental analysis laboratory in Sweden using LC-MS-MS.

[0130] General procedure for purifying PFAS-contaminated water All experiments were conducted in accordance with Figure 4 The general procedure involves adding a cationic surfactant (“cationic detergent”) to PFAS-contaminated water, mixing the mixture for a few seconds, and then passing it through an ultrafiltration membrane. Two components are typically obtained from the ultrafiltration process: the major component, usually comprising 90-95% of the total volume, is permeate, which has a reduced concentration of PFAS compared to unfiltered water. A smaller component, typically comprising 5-10% of the total volume, is retained by the membrane and contains micelles carrying PFAS.

[0131] General Program 1 Add a surfactant to 15 ml of PFAS-contaminated water sample, shake the sample for 1–5 seconds, and then transfer it to ultrafiltration centrifuge tubes with different molecular weight cutoff values, Vivaspin® Turbo 15, as shown in the examples. The tubes are then centrifuged at 3000 rpm for 15 minutes to analyze the PFAS in the permeate. The results shown are primarily for PFAS Sum 11.

[0132] Example 1 Water: Landfill leachate Surfactant: Hexadecyltrimethylammonium bromide (CTAB) Surfactant concentration: 3 g / L Membrane molecular weight cutoff: 10 kDa According to General Procedure 1, experiments were conducted by adding 3 g / L CTAB to water. For reference, experiments were also conducted without the addition of surfactants. The results are shown in Table 1, where the concentration of residual PFAS Sum 11 (“Residual PFAS Sum 11”) is also expressed as a percentage of the amount measured in untreated water.

[0133] Table 1 deal with Unprocessed Ultrafiltration, surfactant-free Ultrafiltration with 3 g / L CTAB PFAS Sum 11 (µg / L) 57232 1157.3 54.31 Residual PFAS Sum 11 (%) 100 2.0 0.09 Example 2 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 1 g / L Membrane molecular weight cutoff: 5 kDa The experiment was conducted according to general procedure 1, by adding 1 g / L CTAB to water. For reference, the experiment was also conducted without the addition of surfactants. The results are shown in Table 2.

[0134] Table 2 deal with Unprocessed Ultrafiltration, surfactant-free Ultrafiltration with 1 g / L CTAB PFAS Sum 11 (µg / L) 25 20 1 Residual PFAS Sum 11 (%) 100 80 4 Example 3 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 5 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 1, by adding 5 g / L CTAB to water. For reference, the experiment was also conducted without the addition of surfactants. The results are shown in Table 3.

[0135] Table 3 deal with Unprocessed Ultrafiltration, surfactant-free Ultrafiltration with 5 g / L CTAB PFAS Sum 11 (µg / L) 9970 1659 159 Residual PFAS Sum 11 (%) 100 17 1.6 Example 4 Water: PFAS-contaminated water Surfactant: Luviquat® Mono LS (CAS No.: 68002-60-8) Surfactant concentration: 1 g / L Membrane molecular weight cutoff: 5 kDa Luviquat® Mono LS is an aqueous solution of lauryl / myristyl trimethylammonium-methyl sulfate, a cationic quaternary ammonium salt, sold, for example, by Sigma Aldrich, with a solids content of approximately 30%.

[0136] The experiment was conducted by adding 1 g / L (based on the dry weight of the surfactant) of LuviquatMono LS to water, following general procedure 1. The results are shown in Table 4.

[0137] Table 4 deal with Unprocessed Ultrafiltration, using 1 g / L Luviquat® Mono LS PFAS Sum 11 (µg / L) 20 8.2 Residual PFAS Sum 11 (%) 100 41 Example 5 Water: PFAS-contaminated water Surfactant: Tetranyl® CO-40 (CAS No. 155042-51-6) Surfactant concentration: 0.5 g / L Membrane molecular weight cutoff: 10 kDa Tetranyl® CO-40 is dioleoylethylhydroxyethylmethylammonium sulfate, a cationic quaternary ammonium salt, for example, sold by Kao Chemicals.

[0138] The experiment was conducted according to general procedure 1, by adding 0.5 g / L of Tetranyl® CO-40 to water. For reference, the experiment was also conducted without the addition of surfactants. The results are shown in Table 5.

[0139] Table 5 deal with Unprocessed Ultrafiltration, surfactant-free Ultrafiltration, using 0.5 g / L Tetranyl® CO-40 PFAS Sum 11 (µg / L) 15.08 7.84 2.43 Residual PFAS Sum 11 (%) 100 52 16 Example 6 Water: PFAS-contaminated water Surfactant: Tetranyl® CO-40 Surfactant concentration: 5 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to General Procedure 1, by adding 5 g / L of Tetranyl® CO-40 to water. For reference, the experiment was also conducted without the addition of surfactants. The results are shown in Table 6.

[0140] Table 6 deal with Unprocessed Ultrafiltration, surfactant-free Ultrafiltration, using 5 g / L Tetranyl® CO-40 PFAS Sum 11 (µg / L) 15.08 7.84 0.47 Residual PFAS Sum 11 (%) 100 52 3.1 Example 7 Water: PFAS-contaminated water Surfactant: Dehyquart® H 81 Surfactant concentration: 2.5 g / L Membrane molecular weight cutoff: 10 kDa Dehyquart® H 81 (via BASF) is a pseudo-cationic surfactant in the form of polyethylene glycol-polyamine condensation resin (INCI name: PEG-15 copolyamine).

[0141] The experiment was conducted by adding 2.5 g / L of Dehyquart® H 81 to water according to General Procedure 1. The results are shown in Table 7.

[0142] Table 7 deal with Unprocessed Ultrafiltration, using 2.5 g / L Dehyquart® H 81 PFAS Sum 11 (µg / L) 12.33 9.96 Residual PFAS Sum 11 (%) 100 81 Refer to Example 8 Water: Landfill leachate Surfactant: Empigen® BB Surfactant concentration: 5 g / L Membrane molecular weight cutoff: 3 kDa Empigen® BB is a 30% dry weight aqueous solution of lauryl dimethyl betaine (an amphoteric surfactant).

[0143] The experiment was conducted according to General Procedure 1 by adding 5 g / L of Empigen® BB surfactant (based on the dry weight of the surfactant) to water. The results are shown in Table 8.

[0144] Table 8 deal with Unprocessed Ultrafiltration, using 5 g / L Empigen® BB PFAS Sum 11 (µg / L) 3867.37 648.66 Residual PFAS Sum 11 (%) 100 17 Reference Example 9 Water: Landfill leachate Surfactant: Cremophor EL Surfactant concentration: 5 g / L Membrane molecular weight cutoff: 3 kDa Cremophor is a nonionic surfactant obtained by the ethoxylation of hydrogenated castor oil.

[0145] Following general procedure 1, the experiment was conducted by adding 5 g / L of Cremophor to water. The results are shown in Table 9.

[0146] Table 9 deal with Unprocessed Ultrafiltration, using 5 g / L Cremophor EL PFAS Sum 11 (µg / L) 3867.37 2697.62 Residual PFAS Sum 11 (%) 100 70 Examples 10-13 and 14-16 were carried out in water containing PFAS, with a PFAS concentration of 25.13 μg / L, expressed as PFAS Sum 11.

[0147] Reference Example 10 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) No surfactants are added.

[0148] Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 1, but without the addition of surfactants. The results are shown in Table 10.

[0149] Table 10 deal with Ultrafiltration, surfactant-free PFAS Sum 11 (µg / L) 12.07 Residual PFAS Sum 11 (%) 48 Refer to Example 11 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) Surfactant: Sodium dodecyl sulfate (SDS) Surfactant concentration: 3 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted by adding SDS to water at a concentration of 3 g / L, following general procedure 1. The results are shown in Table 11.

[0150] Table 11 deal with Ultrafiltration, using 3 g / L SDS PFAS Sum 11 (µg / L) 20.59 Residual PFAS Sum 11 (%) 82 Refer to Example 12 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) Surfactant: Glucopon® 600 CSUP, a nonionic surfactant Surfactant concentration: 3 g / L Membrane molecular weight cutoff: 10 kDa Glucopon® CSUP is a lauryl / myristyl / l-glucoside nonionic surfactant sold by BASF. Experiments were conducted according to General Procedure 1 by adding 3 g / L (based on the dry weight of the surfactant) of Glucopon® CSUP to water. The results are shown in Table 12.

[0151] Table 12 deal with Ultrafiltration, using 3 g / L Glucopon® 600 CSUP PFAS Sum 11 (µg / L) 13.59 Residual PFAS Sum 11 (%) 54 Refer to Example 13 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) Surfactant: A mixture of Glucopon® 600 CSUP and SDS Surfactant concentration: 1 g / L for each surfactant Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to General Procedure 1 by adding the surfactant mixture shown to water at a total concentration of 2 g / L. The results are shown in Table 13.

[0152] Table 13 deal with Ultrafiltration using 1 g / L Glucopon® 600 CSUP and 1 g / L SDS PFAS Sum 11 (µg / L) 18.67 Residual PFAS Sum 11 (%) 74 Example 14 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) Surfactant: Luviquat® HOLD (CAS No. 174761-16-1) (20% solids) Surfactant concentration: 3 g / L Membrane molecular weight cutoff: 10 kDa Luviquat® HOLD is a viscous liquid containing Polyquaternium-68 (Quaternium-68, CAS No. 827346-45-2), namely 1-vinyl-2-pyrrolidone, a polymer of 1-vinylimidazolium and 1-vinyl-3-methylimidazolium methyl sulfate, also known as 1H-imidazolium, 1-vinyl-3-methyl-,methyl sulfate (1:1), a polymer of 1-vinyl-1H-imidazolium, 1-vinyl-2-pyrrolidone and 2-methyl-2-acrylamide (Mw 510.6g), a polymeric cationic surfactant.

[0153] The experiment was conducted by adding 3 g / L (based on the dry weight of the surfactant) of Luviquat® HOLD to water according to General Procedure 1. The results are shown in Table 14.

[0154] Table 14 deal with Ultrafiltration, using 3 g / L Luviquat® HOLD PFAS Sum 11 (µg / L) 9.62 Residual PFAS Sum 11 (%) 38 Example 15 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) A mixture of surfactant compositions of Glucopon® CSUP and Luviquat® Mono LS Surfactant concentration: 2 g / L each Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to General Procedure 1 by adding a surfactant mixture to water in a total amount of 4 g / L. The results are shown in Table 15.

[0155] Table 15 deal with Ultrafiltration using 2 g / L Glucopon® CSUP and 2 g / L Luviquat® Mono LS PFAS Sum 11 (µg / L) 1.04 Residual PFAS Sum 11 (%) 4.1 Example 16 Water: PFAS-contaminated water (25.13 μg / L PFAS Sum 11) Surfactant: A mixture of Glucopon® CSUP and Luviquat® Mono LS Surfactant concentration: 1 g / L for each surfactant Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to General Procedure 1 by adding a surfactant mixture to water at a total concentration of 2 g / L. The results are shown in Table 16.

[0156] Table 16 deal with Ultrafiltration using 1 g / L Glucopon® CSUP and 1 g / L Luviquat® Mono LS PFAS Sum 11 (µg / L) 2.09 Residual PFAS Sum 11 (%) 8.3 Referring to the results of Examples 10-13 and Examples 14-16, the residual PFAS Sum 11, expressed as a percentage, is shown below, based on the concentration of PFAS Sum 11 in untreated water. Figure 5 middle.

[0157] Example 17 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 5 g / L Membrane molecular weight cutoff: 50 kDa The experiment was conducted according to general procedure 1, by adding 5 g / L CTAB to water. For reference, the experiment was also conducted without the addition of surfactants. The results are shown in Table 17.

[0158] Table 17 deal with Unprocessed Ultrafiltration, using 5 g / L CTAB PFAS Sum 11 (µg / L) 9970 6387 Residual PFAS Sum 11 (%) 100 64 General Program 2 Add the surfactant composition to a sample of 0.3–1 L of PFAS-contaminated water, stir the sample for 1–5 minutes, and then perform tangential flow ultrafiltration in a Vivaflow 50 polyethersulfone ultrafiltration filter. Perform tangential flow filtration until only 10% of the original volume is retained in the permeate. Analyze the PFAS in the obtained permeate.

[0159] Reference Examples 18 and 19-21 were all carried out in water containing PFAS, with the PFAS concentration expressed as PFAS Sum 11 as 12 μg / L.

[0160] Refer to Example 18 Water: PFAS-contaminated water (PFAS Sum 11, 12 μg / L) No surfactants added Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, but without the addition of surfactants. The results are shown in Table 18.

[0161] Table 18 deal with Ultrafiltration, surfactant-free PFAS Sum 11 (µg / L) 1.6 Residual PFAS Sum 11 (%) 12.5 Example 19 Water: PFAS-contaminated water (PFAS Sum 11, 12 μg / L) Surfactant: CTAC Surfactant concentration: 0.25 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 0.25 g / L CTAC added as a surfactant. The results are shown in Table 19.

[0162] Table 19 deal with Ultrafiltration, using 0.25 g / L CTAC PFAS Sum 11 (µg / L) 1.8 Residual PFAS Sum 11 (%) 15 Example 20 Water: PFAS-contaminated water (PFAS Sum 11, 12 μg / L) Surfactant: CTAC Surfactant concentration: 0.5 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 0.5 g / L CTAC added as a surfactant. The results are shown in Table 20.

[0163] Table 20 deal with Ultrafiltration, using 0.5 g / L CTAC PFAS Sum 11 (µg / L) 0.85 Residual PFAS Sum 11 (%) 7.1 Example 21 Water: PFAS-contaminated water (PFAS Sum 11, 12 μg / L) Surfactant: CTAC Surfactant concentration: 1 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 1 g / L CTAC added as a surfactant. The results are shown in Table 21.

[0164] Table 21 deal with Ultrafiltration, using 1 g / L CTAC PFAS Sum 11 (µg / L) 0.047 Residual PFAS Sum 11 (%) 0.39 Referring to the results of Examples 18 and 19-21, the residual PFAS Sum 11, expressed as a percentage, is shown below, based on the concentration of PFAS Sum 11 in untreated water. Figure 6 middle.

[0165] Examples 22-24 were all carried out in water containing PFAS, with the PFAS concentration expressed as PFAS Sum 11 of 18 μg / L.

[0166] Example 22 Water: PFAS-contaminated water (PFAS Sum 11, 18 μg / L) Surfactant: Hexadecyltrimethylammonium chloride (CTAC) Surfactant concentration: 0.5 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 0.5 g / L CTAC added as a surfactant. The results are shown in Table 22.

[0167] Table 22 deal with Ultrafiltration, using 0.5 g / L CTAC PFAS Sum 11 (µg / L) 1.1 Residual PFAS Sum 11 (%) 6.1 Example 23 Water: PFAS-contaminated water (PFAS Sum 11, 18 μg / L) Surfactant: Hexadecyltrimethylammonium chloride (CTAC) Surfactant concentration: 0.7 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 0.7 g / L CTAC added as a surfactant. The results are shown in Table 23.

[0168] Table 23 deal with Ultrafiltration, using 0.7 g / L CTAC PFAS Sum 11 (µg / L) 0.64 Residual PFAS Sum 11 (%) 3.6 Example 24 Water: PFAS-contaminated water (PFAS Sum 11, 18 μg / L) Surfactant: Hexadecyltrimethylammonium chloride (CTAC) Surfactant concentration: 1 g / L Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 2, with 1 g / L CTAC added as a surfactant. The results are shown in Table 24.

[0169] Table 24 deal with Ultrafiltration, using 1 g / L CTAC PFAS Sum 11 (µg / L) 0.48 Residual PFAS Sum 11 (%) 2.7 General Program 3 Add the surfactant composition to a sample of 0.3–1 L of PFAS-contaminated water and stir the sample for 1–5 minutes, then perform tangential flow ultrafiltration in a Vivaflow® 50 polyethersulfone ultrafiltration filter. Perform tangential flow filtration until only 10% of the original volume is retained in the permeate. Analyze the PFAS in the obtained permeate. Repeat this process at least n times to obtain a total of n+1 replicates.

[0170] Example 25 Water: Landfill leachate Surfactant: CTAB Number of repetitions: 4 Membrane molecular weight cutoff: 10 kDa Following general procedure 3, experiments were conducted using different amounts of CTAB, as shown in Table 25. Additionally, the concentration of PFAS in the pre-treatment leachate water and in the ultrafiltered water without surfactants was measured. The results are shown in Table 25.

[0171] Table 25 Example 26 Water: PFAS-contaminated water Surfactant: CTAB Number of repetitions: 3 Membrane molecular weight cutoff: 10 kDa The experiments were conducted according to general procedure 3, using different amounts of CTAB, as shown in Table 26. The concentration of PFAS in the water was also determined prior to treatment. The results are shown in Table 26.

[0172] Table 26 General Program 4 Add the surfactant composition to a 25 L water sample contaminated with PFAS, stir the sample for 1–5 minutes, and then perform tangential flow ultrafiltration in an ultrafiltration unit with a filtration capacity of 40–100 L / h until only 10% of the initial liquid volume is retained in the permeate. Analyze the PFAS in the obtained permeate. Repeat this process n times to obtain a total of n+1 replicates.

[0173] Example 27 Water: PFAS-contaminated water Surfactant: CTAC Number of repetitions: 3 Membrane molecular weight cutoff: 10 kDa The experiment was conducted according to general procedure 4, using different amounts of CTAC, as shown in Table 27. The concentration of PFAS in the water was also determined prior to treatment. The results are shown in Table 27 and [the table is missing from the original text]. Figure 7 middle.

[0174] Table 27 References

Claims

1. A method for removing PFAS from an aqueous phase containing PFAS, wherein the aqueous phase contains PFAS at a concentration of up to 2 g / L; the method comprising: (i) Adding a surfactant composition comprising at least one cationic surfactant having a C4-C20 alkyl group as a hydrophobic moiety to a given volume of the PFAS-containing aqueous phase, such that the surfactant forms micelles in the aqueous phase, and (ii) The micelle-containing aqueous phase is contacted with an ultrafiltration membrane under pressure to obtain a permeate aqueous phase with a reduced concentration of PFAS and a filtrate aqueous phase with a higher concentration of PFAS, wherein the volume of the filtrate aqueous phase is less than 10% of the volume of the PFAS-containing aqueous phase in (i), and wherein the concentration of PFAS in the permeate aqueous phase is reduced by at least 97%.

2. The method according to claim 1, wherein the surfactant comprises a hydrophilic portion of a polymer selected from ammonium, methylammonium, dimethylammonium, trimethylammonium, hydroxyethylammonium, methylhydroxyethylammonium, dimethylhydroxyethylammonium, or a polymer containing one or more of these groups.

3. The method according to claim 1 or 2, wherein the PFAS comprises perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, 6:2 fluoropolymer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentane sulfonic acid, perfluoroheptane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, and perfluorododecane sulfonic acid. One or more of the following: alkyl sulfonic acid, 4:2 fluoropolymer sulfonate, 8:2 fluoropolymer sulfonate, perfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide, N-ethylperfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, perfluorooctane sulfonamide acetate, N-methylperfluorooctane sulfonamide acetate, N-ethylperfluorooctane sulfonamide acetate, 7H-perfluoroheptanoic acid, and perfluoro-3,7-dimethyloctanoic acid.

4. The method according to claim 3, wherein the PFAS comprises one or more of perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluoropolymer sulfonate.

5. The method according to any one of claims 1 to 4, wherein the ultrafiltration membrane has a molecular weight cutoff of not more than 100,000 Daltons.

6. The method of claim 5, wherein the ultrafiltration membrane has a molecular weight cutoff in the range of 1,000 to 30,000 Daltons.

7. The method according to any one of claims 1 to 6, wherein the surfactant composition comprises at least one nonionic surfactant.

8. The method of claim 7, wherein the surfactant composition comprises a cationic surfactant and a nonionic surfactant, wherein the weight ratio of the cationic surfactant to the nonionic surfactant is 1:100 to 100:

1.

9. The method of claim 8, wherein the weight ratio is from 1:10 to 10:

1.

10. The method of claim 9, wherein the weight ratio is 1:5 to 5:

1.

11. The method according to any one of claims 1 to 10, comprising repeating (i) and (ii) at least once.

12. The method of claim 11, comprising repeating (i) and (ii) 1 to 5 times.

13. The method according to any one of claims 1 to 10, comprising (iii) determining the concentration of one or more PFAS in the aqueous phase of the permeate stream having a reduced concentration of PFAS, and repeating (i) and (ii) if the determined concentration is higher than a predetermined threshold.

14. The method according to any one of claims 1 to 13, wherein the aqueous phase is selected from landfill leachate, effluent, groundwater, and process water.

15. The method according to any one of claims 1 to 14, wherein the aqueous phase comprises PFAS in an initial concentration ranging from 0.1 μg / L to 1 g / L.

16. The method according to any one of claims 1 to 15, wherein the PFAS concentration in the permeate aqueous phase is reduced by at least 99%.

Images