Method of removing PFAS from water

Abstract

To provide a method of removing PFAS from a PFAS-containing aqueous phase.SOLUTION: Provided is a method including the steps of: adding a surfactant composition containing at least one kind of cationic surfactant to a PFAS-containing aqueous phase and enabling the surfactant to form a micelle in the aqueous phase; and bringing the micelle-containing aqueous phase into contact with an ultrafilter membrane under a pressure and obtaining a transmission liquid flow aqueous phase having a reduced concentration of PFAS.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for removing perfluoro compounds from water. More particularly, the present invention relates to a method for removing PFAS from water by the use of micellar-enhanced ultrafiltration in combination with the addition of a cationic surfactant and / or detergent, or a mixture of a cationic surfactant and / or detergent and a non-ionic surfactant and / or detergent, to the water. [Background technology]

[0002] Ultrafiltration (UF) is a variety of membrane filtration in which forces such as pressure or a concentration gradient lead to separation across a semipermeable membrane. High molecular weight suspended solids and solutes are retained in the so-called retentate, while water and low molecular weight solutes pass through the membrane in the permeate (filtrate). 1 This separation process is carried out by 2 , especially protein solutions 3 It is used in industry and research to purify and concentrate

[0003] Ultrafiltration can be used to remove particulates and macromolecules from raw water to produce drinking water. Ultrafiltration has been used in water treatment plants either to replace existing secondary filtration (coagulation, flocculation, sedimentation) and tertiary filtration (sand filtration and chlorination) systems, or as a stand-alone system in isolated areas with growing populations. 4 Ultrafiltration is used by the dairy industry to concentrate milk proteins and remove water from milk. Ultrafiltration is used by the biotechnology industry to concentrate proteins. 5 .

[0004] Micellar-enhanced ultrafiltration (hereinafter: MEUF) is known as a powerful separation process that has been recently developed to remove a variety of contaminants, such as low molecular weight contaminants, including heavy metals (e.g., lead, cadmium, or zinc), toxic organic materials (e.g., phenol, di-butyl phosphate, tri-butyl phosphate, or trihalomethanes), and organic dyes. 6,8 .

[0005] In MEUF, detergent is added to water at a concentration above the detergent's critical micelle concentration. When the detergent forms micelles, the hydrophobic portions of the detergent molecules aggregate together to form hydrophobic spaces, while the hydrophilic groups of the detergent molecules remain exposed to the water. 9 This forms a spherical structure, usually with a hydrophilic surface and a hydrophobic interior. The weight of the spherical micelles is at least 60,000 Daltons, which allows the detergent micelles to be separated by ultrafiltration. The hydrophilic groups on the surface of the micelles form a phase separation between the hydrophobic interior of the micelles and the water. Since organic pollutants are often quite hydrophobic, they generally preferentially reside in the interior of the micelles, which is the basis of MEUFs for removing pollutants. 7 .

[0006] PFAS (per- and polyfluoroalkyl substances) is a collective name for more than 3,000 industrially produced chemicals. PFAS can be classified into (1) long-chain PFAAs, (2) short-chain PFAAs, (3) non-polymeric and polymeric fluorotelomer-based products, and (4) fluoroplastics and fluoropolymers; long-chain PFAAs include perfluoroalkanesulfonic acids (PFSAs) with carbon chain lengths of 6 or more, and perfluorocarboxylic acids (PFCAs) with carbon chain lengths of 8 or more; short-chain PFAAs include PFSAs with carbon chain lengths of 5 or less, and PFCAs with carbon chain lengths of 7 or less.

[0007] The most common PFAS are perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, and perfluorononanoic acid. perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctanesulfonic acid, 6:2 fluorotelomer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentanesulfonic acid, perfluoroheptanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 4:2 fluorotelomer sulfonate, 8:2 fluorotelomer sulfonate, perfluorooctanesulfonic acid 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, perfluoro-3,7-dimethyloctanoic acid and isomers, homologs and other permutations of these substances.

[0008] The most common standard for PFAS is the so-called "PFAS Sum11," which covers 11 of the most common PFAS: perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluorotelomer sulfonate.

[0009] PFAS are used worldwide in many products, e.g., fire extinguishing agents and impregnation agents. PFAS are widely distributed in the environment; they are persistent and some are toxic. PFAS-contaminated land is found in many parts of the world, where PFAS leak into groundwater and drinking water reservoirs. Recent studies have shown several health problems from PFAS, and PFAS thresholds in drinking water are ongoing. 10~12 .

[0010] PFAS are all produced by humans and their supply to nature comes exclusively from human activities. They occur worldwide in many manufacturing processes, for example as fabric protectants. For example, the most common point source of PFAS in the Swedish environment is extinguishing foam used at airports. Military airports are the most frequent source of PFAS leaking into the environment, followed closely by civilian airports. As PFAS do not degrade in nature and some PFAS have bioaccumulation properties, in addition to limiting their use, it is necessary to combat this contamination with active measures.

[0011] PFAS enter people through contaminated drinking water, through food such as fish and livestock, through crop irrigation with contaminated water, and through inhalation of dust. 13 PFAS can cause liver damage and reproductive toxicity in humans. The largest study was conducted on approximately 60,000 people in the United States who received large amounts of the highly fluorinated substance PFOA (perfluorooctanoic acid) in their drinking water. The study concluded that there was a probable relationship between PFOA exposure in the people studied and high blood cholesterol levels, high blood pressure during pregnancy, ulcerative colitis, thyroid disease, and cancer of the testes and kidneys (C8 Science Panel 2013).

[0012] The most common water-soluble PFASs in the environment have negatively charged moieties that make them soluble in water. Common PFASs, such as perfluorobutanoic acid, perfluorooctane sulfonic acid, and fluorotelomer sulfonates, are all present in high concentrations in most contaminated sites. These perfluorinated molecules are very difficult to break down, meaning they cannot be removed by biological wastewater treatment methods, but are susceptible to oxidation by ozonation water treatment. They are resistant.

[0013] The usual method for removing PFAS from water is different types of carbon filtration, often granular activated carbon (GAC) filtration. Carbon filtration removes the long-chain PFAS molecules perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorooctanesulfonic acid, 6:2 fluorotelomer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 4:2 fluorotelomer sulfonate, 8:2 fluorotelomer sulfonate, perfluorooctanesulfonamide, N-methylperfluoropyrrolidone, and N-methylperfluoropyrrolidone. Perfluorooctanesulfonamide, N-ethylperfluorooctanesulfonamide, N-methylperfluorosulfonamidoethanol, N-ethylperfluorooctanesulfonamideethanol, perfluorooctanesulfonamide acetate, N-methylperfluorooctanesulfonamide acetate, N-ethylperfluorooctanesulfonamide acetate, 7H-perfluoroheptanoic acid, and perfluoro-3,7-dimethyloctanoic acid. However, GAC and other carbon filtration methods are less effective with shorter PFAS molecules, such as perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluoropentanesulfonic acid, and perfluoroheptanesulfonic acid. If there are high concentrations of low molecular weight PFAS molecules in the wastewater stream, it will be necessary to change the carbon filter at more frequent intervals; if the water also contains high levels of organic matter, this will lead to the need to change the carbon filter even more frequently. 14 .

[0014] Another proposed method for treating PFAS-contaminated wastewater is reverse osmosis (RO), which can separate individual metal ions from water with high efficiency and has been shown to remove all types of PFAS from water. 15However, the disadvantage of RO is that it cannot filter water with high ion concentration. In fact, since RO depends on the osmotic mobility of the membrane, the osmotic mobility of the membrane can hardly be achieved at normal pressure when the salt concentration of the water to be treated is high. Although the efficiency of RO can be quite high, efficiencies above 90% can hardly be achieved, meaning that RO can reduce the amount of waste volume by at most 90%; more usually, this volume is about 75-80%. Compared to ultrafiltration, RO consumes more energy. A further disadvantage of RO is that it often requires an ultrafiltration unit as a prefiltration, which increases the complexity of the system. Summary of the Invention [Problem to be solved by the invention]

[0015] There appears to remain an urgent and growing need for methods to effectively remove PFAS from water. [Means for solving the problem]

[0016] Disclosed herein is a method for removing PFAS from water.The method advantageously has improved efficiency and reduced waste volume, regardless of the molecular weight of the PFAS, and is generally useful for all types of PFAS.The method is also generally useful for removing PFAS from any type of PFAS-containing water, such as wastewater, leachate, process water, groundwater, etc., i.e., generally, any type of PFAS-containing aqueous phase.Thus, the method of the present invention allows obtaining water of improved purity in terms of reducing PFAS contamination.

[0017] Accordingly, disclosed herein is a method for removing PFAS from a PFAS-containing aqueous phase, comprising: (i) adding to the aqueous phase a surfactant composition comprising at least one cationic surfactant and allowing the surfactant to form micelles in the aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate flow aqueous phase having a reduced concentration of PFAS. The method includes:

[0018] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (i) adding to the aqueous phase a surfactant composition comprising at least one cationic surfactant and allowing the surfactant to form micelles in the aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate stream aqueous phase having a reduced concentration of PFAS; and optionally (iii) repeating (i) and (ii) at least one time; Includes.

[0019] In some embodiments, (i) and (ii) are repeated at least once. In some embodiments, (i) and (ii) are repeated once. In some embodiments, (i) and (ii) are repeated two or more times.

[0020] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (i) adding to the aqueous phase a surfactant composition comprising at least one cationic surfactant and allowing the surfactant to form micelles in the aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate stream aqueous phase having a reduced concentration of PFAS; (iii) optionally, determining the concentration of one or more PFASs in the permeate stream aqueous phase having a reduced concentration of PFASs; (iv) optionally repeating (i)-(iii) if the determined concentration is above a predefined threshold; Includes.

[0021] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (i) adding to the aqueous phase a surfactant composition comprising at least one cationic surfactant, allowing the surfactant to form micelles in the aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate stream aqueous phase having a reduced concentration of PFAS; (iii) determining the concentration of one or more PFASs in the permeate stream aqueous phase having a reduced concentration of PFASs; (iv) repeating (i) to (iii) if the determined concentration is higher than a predetermined threshold. Includes.

[0022] The methods of the invention allow 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 their toxic effects in animals and humans. [Brief description of the drawings]

[0023] [Figure 1A] FIG. 1A is a schematic diagram of a surfactant molecule having a hydrophilic head and a hydrophobic tail. [Figure 1B] FIG. 1B is a schematic diagram of a micellar structure formed by several surfactant molecules, which has a hydrophilic surface and a hydrophobic interior. [Diagram 2] FIG. 1 shows the chemical structures of the most common PFAS, so-called “PFAS Sum11.” [Figure 3A] FIG. 3A shows the general principle by which PFAS are removed from water by addition of surfactants followed by ultrafiltration. [Figure 3B] FIG. 3B shows micelles formed during the process that carry PFAS on the micelle surface and in the micelle interior. [Figure 4]FIG. 1 is a block diagram that illustrates a schematic of an ultrafiltration procedure for removing PFAS from PFAS-containing water, as disclosed herein. [Diagram 5] FIG. 1 is a bar graph showing the remaining portion of PFAS, expressed as % residual PFAS Sum11, of water that has been subjected to ultrafiltration with no surfactant (Comparative Example 10), or with the addition of an anionic surfactant (Comparative Example 11), a nonionic surfactant (Comparative Example 12), a mixture of anionic and nonionic surfactants (Comparative Example 13), a cationic surfactant (Example 14), or a mixture of cationic and nonionic surfactants (Examples 15 and 16) in water having an initial PFAS Sum11 concentration of 25.13 μg / L. [Figure 6] FIG. 1 is a graph showing the concentration of PFAS Sum11 (μg / L) after ultrafiltration with no added surfactant or with different amounts of the cationic surfactant cetyltrimethylammonium chloride (CTAC) in water initially containing PFAS Sum11 at a concentration of 12 μg / L. [Figure 7] FIG. 1 is a bar graph showing the remaining fraction of PFAS, expressed as % Residual PFAS Sum11, after one (1), two (2) or three (3) repetitions of the process in water with an initial concentration of 69 μg / L, in the presence of cetyltrimethylammonium chloride (CTAC) as a surfactant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] definition As used herein, "surfactant" refers to 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, i.e., compounds that contain a hydrophobic portion (the "hydrophobic tail") and a hydrophilic portion (the "hydrophilic head" or "polar head") (see Figure 1A).

[0025] Most commonly, surfactants are classified by their hydrophilic head: "nonionic surfactants" have no electrically charged groups in their head; the hydrophilic head of a "cationic surfactant" carries a net positive charge, and the hydrophilic head of an "anionic surfactant" carries a net negative charge.

[0026] As used herein, "micelle" refers to an aggregate or supramolecular assembly of surfactant molecules dispersed in a liquid phase. Typical micelles in aqueous solution form aggregates with the hydrophilic portions ("hydrophilic heads") in contact with the surrounding liquid phase and the hydrophobic portions ("hydrophobic tails") sequestered in the center of the micelle. See Figure 1B.

[0027] As used herein, "critical micelle concentration" ("CMC") refers to the concentration of a surfactant in the liquid phase at which the formation of micelles occurs. As used herein, "hydrophilic" refers to the property of having an affinity for water, i.e., a tendency to dissolve in water.

[0028] "Hydrophobicity" as used herein refers to the property of repelling or tending not to mix with water. As used herein, "ultrafiltration" refers to the process by which a liquid is filtered through a filter, typically at some hydraulic head pressure (h Ultrafiltration refers to a process in which a filter is placed under a constant current of pressure in contact with a semipermeable membrane (ultrafiltration membrane) that contains pores of a specified size (cutoff size), whereby molecules or complexes having a size less than the membrane's cutoff size are able to pass through the pores, while molecules or complexes having a size greater than the membrane's cutoff size do not pass through the pores and are retained on the upstream side of the membrane.

[0029] As used herein, "retentate" refers to the semi-retentive liquid that is removed during ultrafiltration. It refers to a molecule or complex that does not pass through the pores of a permeable membrane and is retained on the upstream side of the membrane. As used herein, "permeate" refers to molecules or complexes that pass through the pores of a semipermeable membrane during ultrafiltration.

[0030] The term "cutoff size" or "molecular weight cutoff" as used herein with respect to ultrafiltration membranes refers to the molecular weight of molecules or particles that are 90% retained by the membrane. Dalton (Da) 12 A unit of mass equal to one-twelfth the mass of a C atom. It is approximately 1.66 × 10 -27 Equivalent to kg.

[0031] The unit kDa is 10 3 Equivalent to Dalton. As used herein, "CTAC" refers to cetyltrimethylammonium chloride. As used herein, "CTAB" refers to cetyltrimethylammonium bromide.

[0032] As used herein, "SDS" refers to sodium dodecyl sulfonate. As used herein, "PFAS Sum 11" refers to perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluorotelomer sulfonate.

[0033] As used herein, "PFAS" refers to perfluoroalkyl (or polyfluoroalkyl) substances. Thus, while the term "PFAS" is a collective reference to a type of compound, the term may be used herein to refer simply to one such compound, as well as to mixtures of two or more such compounds. For example, PFASs referred to herein include, for example, perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctanesulfonic acid, 6:2 fluorotelomer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentanesulfonic acid, perfluoroheptanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 4:2 fluorotelomer sulfonate ...pentanesulfonic acid, perfluoropentanesulfonic acid, perfluorooctanesulfonic acid, perfluorooctanesulfonic acid, 4:2 fluorotelomer sulfonate, perfluoropentanesulfonic acid, perfluoropentanesulfonic acid, perfluorooctanesulfonic acid, perfluorooctanesulfonic acid, 4:2 fluorotelomer sulfonate, perfluoropentanesulfonic acid, perfluoropentanesulfonic acid, perfluorooctanesulfonic acid Perfluorooctane sulfonamide, 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, as well as one or more of the isomers, homologs and other variations and combinations of these materials.

[0034] The term "PFAA" refers to perfluoroalkyl acids (or polyfluoroalkyl acids). The term "PFSA" refers to perfluoroalkylsulfonic acid (or polyfluoroalkylsulfonic acid).

[0035] The term "PFCA" refers to perfluoroalkyl carboxylic acids (or polyfluoroalkyl carboxylic acids). Generally as used herein, the term PFAS does not refer to polymeric materials; i.e., as generally used herein, the term PFAS refers to non-polymeric PFAS, and in particular water-soluble PFAS.

[0036] Thus, as used herein, the term PFAS generally refers to one or more non-polymeric PFAS, e.g., long-chain PFAAs, short-chain PFAAs, and non-polymeric fluorotelomer-based products.

[0037] PFAS-containing water The aqueous phase treated by the method of the present invention can be any type of water containing PFAS, such as contaminated water, wastewater, leachate, process water, groundwater and other types of water and / or aqueous solutions containing PFAS. Generally, the aqueous phase containing PFAS treated by the present invention is not an emulsion of PFAS in water. Generally, the aqueous phase contains PFAS dissolved in the aqueous phase.

[0038] The concentration of PFASs present in the aqueous phase being treated can vary over time, for example, from very low to high. Moreover, the specific types of PFASs present in the water being treated can be unknown or can vary without compromising the effectiveness of the methods of the invention.

[0039] In some embodiments, the aqueous phase treated by the method of the present invention is selected from the group consisting of perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctane sulfonic acid, 6:2 fluorotelomer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentanesulfonic acid, perfluoroheptanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 4:2 fluoroisopropyl ether sulfonate, per ... Perfluorooctane sulfonate, 8:2 fluorotelomer 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, as well as one or more of the isomers, homologs and other substitutions of these materials.

[0040] In some embodiments, the aqueous phase treated by the methods of the present invention contains one or more of perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctane sulfonic acid, and 6:2 fluorotelomer sulfonate.

[0041] In some embodiments, the water treated by the methods of the present invention has a phosphate ion 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 1 g / L. 00 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.

[0042] In some embodiments, water treated by the methods of the invention contains an initial total concentration of PFASs of 10 g / L or less, or 5 g / L or less, or 2 g / L or less, or 1 g / L or less, or 500 mg / L or less, or 200 mg / L or less, or 100 mg / L or less, or 50 mg / L or less, or 20 mg / L or less, or 10 mg / L or less, or 5 mg / L or less, or 2 mg / L or less, or 1 mg / L or less, or 500 μg / L or less, or 200 μg / L or less, or 100 μg / L or less, or 50 μg / L or less, or 20 μg / L or less.

[0043] In some embodiments, the water treated by the method of the present invention has an initial concentration within a range from any above specified lower limit to any above specified upper limit, e.g., 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 2 ... PFAS containing initial concentrations in the ranges of 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 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.

[0044] In some of the above embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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.

[0045] Thus, in some embodiments, water treated by the methods of the invention contains an initial concentration of PFAS 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, 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.

[0046] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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, 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.

[0047] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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, 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.

[0048] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 100 mg / L.

[0049] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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, 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.

[0050] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 mg / L.

[0051] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 5 mg / L.

[0052] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 mg / L.

[0053] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 1 mg / L.

[0054] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 μg / L.

[0055] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 200 μg / L.

[0056] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 100 μg / L.

[0057] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS 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 μg / L.

[0058] In some embodiments, the water treated by the methods of the invention contains an initial concentration of PFAS in the 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.

[0059] In some embodiments, the initial concentration of PFAS is determined by measuring the initial concentration of at least one PFAS selected from PFAS Sum11 and taking the measured value as the value for the total initial PFAS concentration.

[0060] In some embodiments, the initial concentration of the PFAS is determined by measuring the initial total concentration of PFAS Sum11 and taking the measured value as the value for the total initial PFAS concentration. In some embodiments, the initial concentration of PFAS is determined by measuring the initial concentration of PFAS Sum11, multiplying the measured value by a factor k, e.g., a factor k ranging from 1.2 to 10, or 1.2 to 5, or 1.2 to 4, or 1.2 to 3, or 1.2 to 3, or 1.2 to 2, or 1.2 to 1.5, and taking the calculated value as the value for the total initial PFAS concentration. A particular factor k can be determined for each type of water, e.g., by determining, for a particular type of water, the average total concentration of PFAS (e.g., other than polymeric PFASs) in the water, and the average concentration of PFAS Sum11.

[0061] Surfactant Composition To achieve effective separation of PFAS from the aqueous phase, a surfactant composition comprising at least one cationic surfactant is mixed with the aqueous phase to allow for the formation of micelles in the aqueous phase.

[0062] As used herein, the term "surfactant composition" can refer to one particular surfactant compound or a mixture of surfactant compounds, optionally in a liquid carrier, e.g., water. Thus, in some embodiments, the method of the invention includes the steps of (i) adding a cationic surfactant to a PFAS-containing aqueous phase to form micelles in said aqueous phase, and (ii) subjecting the aqueous phase to ultrafiltration, e.g., as described herein.

[0063] In some other embodiments, the methods of the invention include (i) adding a mixture of cationic surfactants to a PFAS-containing aqueous phase to form micelles in the aqueous phase; and (ii) subjecting the aqueous phase to ultrafiltration, e.g., as described herein.

[0064] In some embodiments, in addition to the cationic surfactant or mixture of cationic surfactants, the surfactant composition further comprises a nonionic surfactant or mixture of nonionic surfactants.For example, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of 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, for example, 2:1 to 1:2 of cationic surfactant to nonionic surfactant.

[0065] In some further embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of cationic surfactant to nonionic surfactant of from 100:1 to 1:1, or from 50:1 to 1:1, or from 20:1 to 1:1, or from 10:1 to 1:1, or from 5:1 to 1:1, e.g., from 2:1 to 1:1.

[0066] In some further embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of cationic surfactant to nonionic surfactant of from 100:1 to 2:1, or from 50:1 to 2:1, or from 20:1 to 2:1, or from 10:1 to 2:1, or from 5:1 to 2:1.

[0067] In some further embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of cationic surfactant to nonionic surfactant of from 100:1 to 5:1, or from 50:1 to 5:1, or from 20:1 to 5:1, or from 10:1 to 5:1.

[0068] In some further embodiments, the surfactant composition comprises a cationic surfactant and a non-ionic surfactant. The cationic surfactant and the nonionic surfactant are contained in a weight ratio of 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.

[0069] In some further embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of cationic surfactant to nonionic surfactant of from 1:2 to 1:100, or from 1:2 to 1:50, or from 1:2 to 1:20, or from 1:2 to 1:10, or from 1:2 to 1:5.

[0070] In some further embodiments, the surfactant composition comprises a cationic surfactant and a nonionic surfactant in a weight ratio of cationic surfactant to nonionic surfactant of from 1:5 to 1:100, or from 1:5 to 1:50, or from 1:5 to 1:20, or from 1:5 to 1:10.

[0071] In some embodiments, the surfactant composition comprises only cationic surfactants.

[0072] Cationic Surfactants Any cationic surfactant or mixture of cationic surfactants is generally considered to be useful in the method of the present invention. As described herein above, the surfactant comprises a hydrophobic portion and a hydrophilic portion. The hydrophobic portion of the surfactant useful herein is generally a C4-C20 hydrocarbyl group, such as an alkyl group containing 4-20 carbon atoms, such as butyl, pentyl, hexyl, heptyl, octyl, nonyl, decanyl, undecanyl, dodecanyl, tridecanyl, tetradecanyl, pentadecanyl, hexadecanyl, heptadecanyl, octadecenyl, nonadecanyl, and acosanyl. The hydrophilic portion of the cationic surfactant used herein may be selected from, for example, ammonium, methylammonium, dimethylammonium, trimethylammonium, hydroxyethylammonium, methylhydroxyethylammonium, and dimethylhydroxyethylammonium.

[0073] For example, in some embodiments, the surfactant composition may comprise a surfactant such as (e.g., Cl - Salt or Br - (as salt) of general formula R4N + where at least one R is a hydrophobic moiety, e.g., a C10-C20 alkyl chain, and the R groups may further contain N-C or O-C bonds, and may be branched or straight chain, substituted or unsubstituted, saturated or unsaturated, and aromatic or aliphatic. Examples of cationic surfactants are, for example, C10-C20 alkyl trimethyl ammonium salts, e.g., C10-C20 alkyl trimethyl ammonium halides.

[0074] In some embodiments, the surfactant composition comprises a cationic surfactant selected from cetyltrimethylammonium bromide and cetyltrimethylammonium chloride.However, it should be recognized that the present invention is not limited to any particular type of cationic surfactant.Furthermore, as pointed out hereinabove, unless otherwise specified or clear from the context, reference to "cationic surfactant" should also be understood to refer to a mixture of cationic surfactants.

[0075] Further, the cationic surfactant may be a cationic polymeric surfactant, for example, the cationic polymeric surfactant described in RAWessling & D.M. Pickelman (1981) Cationic Polymeric Surfactants, Journal of Dispersion The cationic polymeric surfactants may also be those described in Science and Technology, 2:2-3, 281-313, the contents of which are incorporated herein in their entirety.

[0076] In some embodiments, the surfactant composition comprises a cetyltrimethylammonium halide, such as CTAB or CTAC. In some embodiments, the surfactant composition comprises only cationic surfactant.In some embodiments, the surfactant composition is one or more cationic surfactants in a liquid carrier, for example, one or more cationic surfactants in an aqueous liquid carrier.

[0077] Nonionic Surfactants Examples of non-ionic surfactants are alcohol ethoxylates and alkylphenol ethoxylates. Alcohol ethoxylates have the general formula R(OCH2CH2) n OH, where R can be, for example, a C9-C18 linear or branched alkyl, and n can be an integer from 1 to 40, for example, from 5 to 20. Alkylphenol ethoxylate surfactants can be represented by the general formula R-(C6H4)-(OCH2CH2) nOH, where R can be, for example, a C8-C16 linear or branched alkyl, and n can be an integer from 1 to 30, for example, from 5 to 15.

[0078] For purposes of the present invention, unless otherwise specified or clear from the context, reference to a "nonionic surfactant" should also be understood to include mixtures of nonionic surfactants.

[0079] Ultrafiltration Membrane Ultrafiltration membranes are typically specified to have a particular cut-off size or molecular cut-off weight. There are many types of ultrafiltration membranes (or filters) made from a variety of materials, such as polyethersulfone, regenerated cellulose, or ceramic materials. Any type of ultrafiltration technique can be used in the present invention. Ultrafiltration can be carried out by cross-flow filtration with spiral wound membranes, where the feed stream is introduced into the membrane element under pressure and passed across the membrane surface in a controlled flow path, with the permeate passing through the membrane while the rejected material can be poured off as retentate.

[0080] Another common ultrafiltration device uses hollow fiber membranes. The membranes are formed into long, very thin tubes or fibers (typically 0.6-2 mm in diameter) sealed in connectors at both ends. Hundreds of these fibers, each with a single inlet and outlet connector, are called a "bundle" or "cartridge" and are grouped 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. Fluid is thus collected in the cartridge area surrounding the fibers and forced through the membrane, with suspended materials remaining inside the membrane.

[0081] Thus, in the process of the invention, any type of ultrafiltration membrane may be used, for example, spiral-wound, tubular, hollow fiber or flat sheet membranes of materials such as cellulose acetate (CA), polyvinylidene fluoride (PVDF), polyacrylonitrile, polypropylene, polysulfone (PS), polyethersulfone (PES), or other polymers, and the membranes may also be made from ceramic materials.

[0082] Preferably, the ultrafiltration membrane has a molecular weight cutoff of 100,000 Daltons (100 kDa) or less, for example, preferably 50 kDa or less, more preferably 30 kDa or less, 25 kDa or less, 20 kDa or less, 15 kDa or less, or 10 kDa or less, for example 1-100 kDa, 5-50 kD, 1-30 kD, 1-25 kDa, 1-20 kDa, 1-15 kDa, or 1-10 kDa.

[0083] method In the methods of the invention, a surfactant composition as defined herein is mixed with a PFAS-containing aqueous phase to form surfactant-containing micelles.

[0084] The surfactant composition is added to the surfactant composition in the aqueous phase in an amount that causes the formation of micelles, i.e., achieves at least the critical micelle concentration (CMC). In some embodiments, an excess amount of the surfactant composition may be added, e.g., 10-100% (e.g., 20-50%) more than the amount estimated to be needed to reach the CMC.

[0085] The surfactant composition can be added to the aqueous phase as a liquid solution or in solid (e.g., powder or granule) form, e.g., in the form of a salt that dissolves in the aqueous phase. The formation of micelles is believed to be a rapid process as long as the CMC is reached. Moreover, once the micelles are formed to provide an emulsion of micelles in the PFAS-containing aqueous phase, the micelle-containing aqueous phase can be subjected to ultrafiltration without substantial delay. That is, partitioning of the PFAS into the micellar phase is believed to occur fairly quickly, e.g., within a few minutes (e.g., 1-10 minutes, or 1-5 minutes, or 2-5 minutes) or less.

[0086] The amount of surfactant composition to be added to any particular type of water can be determined by one of skill in the art, for example, by collecting a representative sample of the water and determining the PFAS before and after ultrafiltration in the presence of a selected surfactant composition at a concentration of at least the CMC, and optionally testing several different surfactant compositions and / or different surfactant concentrations. Typically, the concentration of PFAS present in any water to be treated is significantly lower than the CMC of any surfactant, and therefore, at the CMC, the surfactant composition of the present invention is considered to be effective in the method of the present invention.

[0087] The PFAS-contaminated aqueous phase, containing a surfactant composition as defined herein at a concentration above the CMC, is contacted under pressure with an ultrafiltration membrane to obtain a permeate stream and a retentate stream. The retentate stream will have a higher concentration of PFAS than the PFAS-contaminated aqueous phase entering the ultrafiltration unit, while the aqueous permeate stream will have a reduced PFAS concentration. It is assumed that the PFAS is trapped within the micelles and on the surfaces of the micelles, and thus is essentially retained in the retentate stream.

[0088] In some embodiments of the present invention, the PFAS-containing water is treated in an iterative manner with the surfactant composition described herein by using ultrafiltration. Thus, in some embodiments, the permeate, which contains a reduced amount of PFAS compared to the aqueous stream entering the ultrafiltration device, is subjected to a further addition of a surfactant composition containing a cationic surfactant and optionally a nonionic surfactant, which may be the same or different from the surfactant composition previously added, and then contacted again with the ultrafiltration device, which may be the same or different from the device used in the previous filtration step.

[0089] In some embodiments, the repetition is accomplished using a recirculation system to recirculate the permeate multiple times through an ultrafiltration unit containing an ultrafilter, each time adding a surfactant composition in an amount greater than that required to reach the CMC in the aqueous phase, and each time separating a PFAS-rich retentate and a permeate having a reduced concentration of PFAS.

[0090] Recirculation may be repeated a set number of times, for example 1-5 times, or 1-3 times (although more iterations may be used if necessary, for example in the case of highly contaminated water), or until analysis of the ultrafiltration permeate indicates that a satisfactorily low PFAS concentration has been reached.

[0091] Thus, in some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (i) adding a surfactant composition to the aqueous phase, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate stream aqueous phase having a reduced concentration of PFAS; Includes.

[0092] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (1) adding a surfactant composition to the aqueous phase, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase; (2) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having 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, and allowing the surfactant to form micelles in the aqueous phase having a reduced concentration of PFAS; (4) contacting the micelle-containing aqueous phase having a reduced concentration of PFAS with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a further reduced concentration of PFAS; and optionally repeating (3) and (4) one or more times, e.g., 1, 2, 3, or 4 times. Includes.

[0093] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (1) adding a surfactant composition to the aqueous phase containing PFAS at an initial concentration c0 of PFAS, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase; (2) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a reduced concentration c1 of PFAS; and optionally (3) adding a surfactant composition to the aqueous phase having a reduced concentration c1 of PFAS, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase having a reduced concentration c1 of PFAS; (4) contacting the micelle-containing aqueous phase having a reduced concentration c1 of PFAS with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a further reduced concentration c2 of PFAS; (5) optionally performing (3) and (4) one or more times, e.g., 1, 2, 3, or 4 or more times, e.g., a preset number of times, or, e.g., n+1 C n and repeating the steps until Includes. In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (1) adding a surfactant composition to the aqueous phase containing PFAS at an initial concentration c0 of PFAS, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase; (2) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a reduced concentration c1 of PFAS; (3) adding a surfactant composition to the aqueous phase having a reduced concentration c1 of PFAS, the surfactant composition comprising at least one cationic surfactant, forming micelles in the aqueous phase having a reduced concentration c1 of PFAS; (4) contacting the micelle-containing aqueous phase having a reduced concentration of PFAS, c1, with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a further reduced concentration of PFAS, c2; and optionally repeating (3) and (4) one or more times, e.g., 1, 2, 3, or 4 or more times, e.g., a predetermined number of times, or, e.g., c n+1 C n and repeating the steps until Includes.

[0094] In some embodiments, a method for removing PFAS from a PFAS-containing aqueous phase includes: (1) adding a surfactant composition to the aqueous phase containing PFAS at an initial concentration c0, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase; (2) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a reduced concentration c1 of PFAS; (3) determining the concentration of one or more PFASs in the permeate stream aqueous phase having a reduced concentration of PFASs; and optionally (4) if the concentration determined in (3) is greater than a threshold value, adding a surfactant composition to the aqueous phase having a reduced concentration c1 of PFAS, the surfactant composition comprising at least one cationic surfactant, and allowing the surfactant to form micelles in the aqueous phase having a reduced concentration c1 of PFAS; (5) contacting the micelle-containing aqueous phase having a reduced concentration c1 of PFAS with an ultrafiltration membrane under pressure to obtain an aqueous phase permeate stream having a further reduced concentration c2 of PFAS; and optionally repeating (3) and (4) one or more times, e.g., 1, 2, 3, or 4 or more times, e.g., a predetermined number of times, or until the concentration determined in (3) no longer exceeds a threshold value. Includes.

[0095] By repeating the treatment of PFAS-contaminated water several times with the surfactant compositions defined herein, PFAS can be removed by ultrafiltration to below the detection limit of PFAS analysis.

[0096] In some embodiments, as mentioned hereinabove, in the step of determining the concentration of one or more PFASs in the aqueous phase (e.g., the permeate stream aqueous phase), the concentration of at least one PFAS selected from PFAS Sum11 is determined, e.g., PFAS The total concentration of Sum11 is determined.

[0097] The surfactant composition added at each step can generally be as described herein above, for example, it can be a cationic surfactant such as CTAB or CTAC or a concentrated aqueous solution thereof.

[0098] In some other embodiments, in methods involving adding a micelle-forming amount of a surfactant composition to the permeate stream exiting one ultrafiltration filter, where the micelle-forming amount and surfactant may be different for each point of addition, it is envisioned that rather than subjecting the aqueous phase to recirculation through one and the same ultrafiltration membrane, ultrafiltration may be carried out using several ultrafiltration filters in series, either of the same type, or of different types, e.g., having different molecular weight cut-off sizes.

[0099] Additionally, it is envisioned that a combination of recirculation and a series of ultrafiltration units on the same ultrafiltration filter is possible. The principle of the invention is as shown diagrammatically in FIG. 3A, where a surfactant composition ("surfactant") described herein is added to PFAS-containing water 1 at a concentration that allows for the formation of micelles. It is envisioned that the PFAS present in the aqueous phase can be anionic compounds 2 and nonionic compounds 3. As also shown in FIG. 3B, the anionic PFAS 2 will associate with the micelles at the micelle surface as a counterion to the cationic surfactant of the micelles, while the nonionic PFAS 3 will essentially partition into the hydrophobic space within the micelles to form PFAS-bearing micelles 4. Compared to ultrafiltration, the reaction is believed to be rapid, and thus the solution can be essentially immediately ultrafiltered through an ultrafiltration membrane 5 with a molecular weight cutoff smaller than the size of the formed micelles 4 to obtain a retentate 6 with an increased concentration of PFAS and a permeate 7 (not shown) with a reduced concentration of PFAS.

[0100] It is an advantageous feature of the process of the present invention that the retentate proportion of the treated water is fairly small, generally accounting for less than 15% by volume, or even less than 10% by volume of the inlet water volume, which reduces the problems inherent in large volumes of wastewater.

[0101] Advantageously, a reduction in the initial concentration of PFAS in water of 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, e.g., down to detection levels, can be achieved by the present invention.

[0102] The efficiency of removing PFAS from PFAS-contaminated water depends not only on the choice of surfactant, but also on the molecular weight cut-off of the ultrafiltration membrane selected. In general, the optimal molecular weight cut-off for ultrafiltration membranes has been found to be less than 100 kDa, more preferably less than 50 kDa, and even more preferably less than 30 kDa, for example, 5-20 kDa. For example, membranes with molecular weight cut-offs of 5-100 kDa, or 5-50 kDa, for example, 5-30 kDa, can be used.

[0103] The invention has been shown to work in small-scale ultrafiltration devices for laboratory use, such as centrifuge tubes fitted with membranes, or tangential flow ultrafiltration devices for laboratory use that can process from 100 ml to several liters, and on a larger scale, in ultrafiltration devices used to treat cubic meters of PFAS-contaminated water.

[0104] The invention is illustrated by the following non-limiting examples. For comparison, comparative examples not according to the invention are also set forth. EXAMPLES

[0105] material All surfactants used were of commercial quality and were obtained from commercial chemical suppliers, e.g., in the form of commercial detergents. The waters tested were contaminated waters from various sources at a PFAS-contaminated site located in Sweden. The ultrafiltration membranes were commercially available membranes obtained from an ultrafiltration equipment supplier.

[0106] PFAS analysis The water was analysed step by step by an accredited environmental analytical laboratory located in Sweden and the water analysis was performed by LC-MS-MS.

[0107] General Procedure for Purifying PFAS-Contaminated Water All experiments were performed according to the general procedure shown in Figure 4. A "nonionic detergent" ("peptide") was added to the PFAS-contaminated water, the mixture was subjected to mixing for several seconds, and then passed through an ultrafiltration membrane. Two fractions were generally obtained from the ultrafiltration process, the major fraction, usually consisting of 90-95% of the total volume, was the permeate, which had a reduced concentration of PFAS compared to the unfiltered water. The minor fraction, usually consisting of 5-10% of the total volume, was retained by the membrane and contained PFAS-carrying micelles.

[0108] General Procedure 1 As shown in the examples, surfactant was added to 15 ml samples of PFAS-contaminated water, the samples were shaken for 1-5 seconds, and then transferred to ultrafiltration centrifuge tubes, Vivaspin® Turbo 15, with different molecular weight cut-offs. The tubes were then centrifuged at 3000 rpm for 15 minutes, and the permeate was analyzed for PFAS. The results shown are essentially for PFAS Sum 11.

[0109] Example 1 Water: Landfill leachate Surfactant: Cetyltrimethylammonium bromide (CTAB) Surfactant concentration: 3g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out by adding CTAB to the water at 3 g / L, according to General Procedure 1. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 1, which also shows the residual concentration of PFAS Sum11 ("Residual PFAS Sum11") as a % of the amount measured in the untreated water.

[0110] [Table 1]

[0111] Example 2 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 1g / L Membrane molecular weight cutoff: 5kDa The experiment was carried out by adding CTAB to water in an amount of 1 g / L according to General Procedure 1. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 2.

[0112] [Table 2]

[0113] Example 3 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 5g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out by adding CTAB to water in an amount of 5 g / L according to General Procedure 1. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 3.

[0114] [Table 3]

[0115] Example 4 Water: PFAS-contaminated water Surfactant: Luviquat® Mono LS (CAS number: 68002-60-8) Surfactant concentration: 1g / L Membrane molecular weight cutoff: 5kDa Luviquat® Mono LS is an aqueous solution of lauryl / myristyl trimethylammonium methosulfate, a cationic quaternary ammonium salt, sold, for example, by Sigma Aldrich, and has a solids content of about 30%.

[0116] The experiment was carried out by adding Luviquat Mono LS to water in an amount of 1 g / L (based on the dry weight of the surfactant) according to General Procedure 1. The results are shown in Table 4.

[0117] [Table 4]

[0118] Example 5 Water: PFAS-contaminated water Surfactant: Tetranyl® CO-40 (CAS number 155042-51-6) Surfactant concentration: 0.5g / L Membrane molecular weight cutoff: 10kDa Tetranyl® CO-40 is dioleoylethyl hydroxyethylmonium methosulfate, a cationic quaternary ammonium salt, sold, for example, by Kao Chemicals.

[0119] The experiment was carried out according to General Procedure 1 by adding Tetranyl® CO-40 to water in an amount of 0.5 g / L. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 5.

[0120] [Table 5]

[0121] Example 6 Water: PFAS-contaminated water Surfactant: Tetranyl® CO-40 Surfactant concentration: 5g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 1 by adding Tetranyl® CO-40 to water in an amount of 5 g / L. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 6.

[0122] [Table 6]

[0123] Example 7 Water: PFAS-contaminated water Surfactant: Dehyquart® H81 Surfactant concentration: 2.5g / L Membrane molecular weight cutoff: 10kDa Dehyquart® H81 (BASF) is a pseudo-cationic surfactant in the form of a polyglycol-polyamine condensation resin (INCI name: PEG-15 Cocopolyamine).

[0124] The experiment was carried out by adding Dehyquart® H81 to water in an amount of 2.5 g / L according to General Procedure 1. The results are shown in Table 7.

[0125] [Table 7]

[0126] Comparative Example 8 Water: Landfill leachate Surfactant: Empigen® BB Surfactant concentration: 5g / L Membrane molecular weight cutoff: 3kDa Empigen® BB is a 30% dry weight aqueous solution of lauryl dimethyl betaine, an amphoteric surfactant.

[0127] The experiment was carried out by adding Empigen® BB to water at a surfactant level of 5 g / L (by dry weight of surfactant) according to General Procedure 1. The results are shown in Table 8.

[0128] [Table 8]

[0129] Comparative Example 9 Water: Landfill leachate Surfactant: Cremophor EL Surfactant concentration: 5g / L Membrane molecular weight cutoff: 3kDa Cremophor is a non-ionic surfactant obtained by ethoxylation of hydrogenated castor oil.

[0130] The experiment was carried out by adding Cremophor to water at 5 g / L according to General Procedure 1. The results are shown in Table 9.

[0131] [Table 9]

[0132] Comparative Examples 10-13 and Examples 14-16 were carried out on PFAS-containing water having a PFAS concentration of 25.13 μg / L in terms of PFAS Sum11.

[0133] Comparative Example 10 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) No surfactant was added.

[0134] Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 1 but without the addition of surfactant, and the results are shown in Table 10.

[0135] [Table 10]

[0136] Comparative Example 11 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant: Sodium dodecyl sulfate (SDS) Surfactant concentration: 3g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out by adding SDS to water in an amount of 3 g / L according to General Procedure 1. The results are shown in Table 11.

[0137] [Table 11]

[0138] Comparative Example 12 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant: Glucopon® 600 CSUP, a non-ionic surfactant Surfactant concentration: 3g / L Membrane molecular weight cutoff: 10kDa Glucopon® CSUP is lauryl / myristyl / l glucoside, a non-ionic surfactant sold by BASF. The experiment was carried out according to General Procedure 1 by adding Glucopon® CSUP to water in an amount of 3 g / L (based on the dry weight of the surfactant). The results are shown in Table 12.

[0139] [Table 12]

[0140] Comparative Example 13 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant: Glucopon® 600 CSUP and SDS mixture Surfactant concentration: 1g / L for each surfactant Membrane molecular weight cutoff: 10kDa The experiments were carried out by adding the indicated surfactant mixtures to water at a total amount of 2 g / L according to General Procedure 1. The results are shown in Table 13.

[0141] [Table 13]

[0142] Example 14 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant: Luviquat® HOLD (CAS number 174761-16-1) (20% solids) Surfactant concentration: 3g / L Membrane molecular weight cutoff: 10kDa Luviquat® HOLD is a viscous liquid, polymeric cationic surfactant containing Polyquaternium-68 (Quaternium-68, CAS number 827346-45-2), i.e., 1-ethenyl-2-pyrrolidinone, 1-ethenylimidazole and 1-ethenyl-3-methylimidazolium methylsulfate, also known as 1H-imidazolium, polymer with 1-ethenyl-3-methyl-, methylsulfate (1:1), polymer with 1-ethenyl-1H-imidazole, 1-ethenyl-2-pyrrolidinone and 2-methyl-2-propenamide (Mw 510.6 g).

[0143] The experiment was carried out by adding Luviquat® HOLD to water in an amount of 3 g / L (based on the dry weight of the surfactant) according to General Procedure 1. The results are shown in Table 14.

[0144] [Table 14]

[0145] Example 15 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant Composition Mixture of Glucopon® CSUP and Luviquat® Mono LS Surfactant concentration: 2g / L each Membrane molecular weight cutoff: 10kDa The experiment was carried out by adding the surfactant mixture to water at a total amount of 4 g / L according to General Procedure 1. The results are shown in Table 15.

[0146] [Table 15]

[0147] Example 16 Water: PFAS contaminated water (PFAS Sum11 at 25.13μg / L) Surfactant: a mixture of Glucopon® CSUP and Luviquat® Mono LS Surfactant concentration: 1g / L for each surfactant Membrane molecular weight cutoff: 10kDa The experiment was carried out by adding the surfactant mixture to water at a total amount of 2 g / L according to General Procedure 1. The results are shown in Table 16.

[0148] [Table 16]

[0149] The results of Comparative Examples 10 to 13 and Examples 14 to 16 are shown in FIG. 5 in terms of the % of residual PFAS Sum11 relative to the concentration of PFAS Sum11 in untreated water.

[0150] Example 17 Water: Landfill leachate Surfactant: CTAB Surfactant concentration: 5g / L Membrane molecular weight cutoff: 50kDa The experiment was carried out by adding CTAB to water in an amount of 5 g / L according to General Procedure 1. As a comparison, an experiment was also carried out without adding any surfactant. The results are shown in Table 17.

[0151] [Table 17]

[0152] General Procedure 2 The surfactant composition was added to 0.3-1 L samples of PFAS-contaminated water, the samples were stirred for 1-5 minutes, and then subjected to tangential flow ultrafiltration in a Vivaflow50 polyethersulfone ultrafiltration filter. Tangential flow filtration was carried out until only 10% of the original volume remained in the retentate. The resulting permeate was analyzed for PFAS.

[0153] Comparative Example 18 and Examples 19-21 were all carried out with respect to PFAS-containing water having a PFAS concentration of 12 μg / L in terms of PFAS Sum11.

[0154] Comparative Example 18 Water: PFAS contaminated water (PFAS Sum11 at 12μg / L) No surfactant added Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, but without the addition of surfactant, and the results are shown in Table 18.

[0155] [Table 18]

[0156] Example 19 Water: PFAS contaminated water (PFAS Sum11 at 12μg / L) Surfactant: CTAC Surfactant concentration: 0.25g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 0.25 g / L of CTAC added as surfactant, and the results are shown in Table 19.

[0157] [Table 19]

[0158] Example 20 Water: PFAS contaminated water (PFAS Sum11 at 12μg / L) Surfactant: CTAC Surfactant concentration: 0.5g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 0.5 g / L of CTAC added as surfactant, and the results are shown in Table 20.

[0159] [Table 20]

[0160] Example 21 Water: PFAS contaminated water (PFAS Sum11 at 12μg / L) Surfactant: CTAC Surfactant concentration: 1g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 1 g / L CTAC added as surfactant, and the results are shown in Table 21.

[0161] [Table 21]

[0162] The results of Comparative Example 18 and Examples 19-21 are shown in FIG. 6 in terms of the % of residual PFAS Sum11 relative to the concentration of PFAS Sum11 in untreated water. Examples 22 to 24 were all carried out on PFAS-containing water having a PFAS concentration of 18 μg / L in terms of PFAS Sum 11.

[0163] Example 22 Water: PFAS contaminated water (PFAS Sum11 at 18μg / L) Surfactant: Cetyltrimethylammonium chloride (CTAC) Surfactant concentration: 0.5g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 0.5 g / L of CTAC added as surfactant, and the results are shown in Table 22.

[0164] [Table 22]

[0165] Example 23 Water: PFAS contaminated water (PFAS Sum11 at 18μg / L) Surfactant: Cetyltrimethylammonium chloride (CTAC) Surfactant concentration: 0.7g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 0.7 g / L of CTAC added as surfactant, and the results are shown in Table 23.

[0166] [Table 23]

[0167] Example 24 Water: PFAS contaminated water (PFAS Sum11 at 18μg / L) Surfactant: Cetyltrimethylammonium chloride (CTAC) Surfactant concentration: 1g / L Membrane molecular weight cutoff: 10kDa The experiment was carried out according to General Procedure 2, with 1 g / L CTAC added as surfactant, and the results are shown in Table 24.

[0168] [Table 24]

[0169] General Procedure 3 The surfactant composition was added to 0.3-1 L samples of PFAS-contaminated water, the samples were stirred for 1-5 minutes, and then subjected to tangential flow ultrafiltration in a Vivaflow® 50 polyethersulfone ultrafiltration filter. Tangential flow filtration was performed until only 10% of the original volume remained in the retentate. The resulting permeate was analyzed for PFAS. The procedure was repeated n additional times to give a total number of replicates of n+1.

[0170] Example 25 Water: Landfill leachate Surfactant: CTAB Number of iterations: 4 Membrane molecular weight cutoff: 10kDa The experiments were carried out according to General Procedure 3, using different amounts of CTAB as shown in Table 25. PFAS concentrations were additionally measured in the leachate water before treatment and in the water that underwent ultrafiltration without surfactant. The results are shown in Table 25.

[0171] [Table 25]

[0172] Example 26 Water: PFAS-contaminated water Surfactant: CTAB Number of iterations: 3 Membrane molecular weight cutoff: 10kDa The experiments were carried out according to General Procedure 3 using different amounts of CTAB as shown in Table 26. PFAS concentrations were additionally measured in the water before treatment. The results are shown in Table 26.

[0173] [Table 26]

[0174] General Procedure 4 The surfactant composition was added to a 25 L sample of PFAS-contaminated water, the sample was stirred for 1-5 min, and then subjected to tangential flow ultrafiltration in an ultrafiltration unit with a filtration capacity of 40-100 L / h. Tangential flow filtration was carried out until only 10% of the original liquid volume remained in the retentate. The resulting permeate was analyzed for PFAS. The procedure was repeated n times to obtain a total number of replicates of n+1.

[0175] Example 27 Water: PFAS-contaminated water Surfactant: CTAC Number of iterations: 3 Membrane molecular weight cutoff: 10kDa The experiments were carried out according to General Procedure 4 using different amounts of CTAC as shown in Table 27. PFAS concentrations were additionally measured in the water prior to treatment. The results are shown in Table 27 and in FIG. 7.

[0176]

Table 27

[0177] Cited References 1. American Water Works Association Research Foundation; Ed. group Joel Mallevialle (1996). “Water treatment membrane processes.” New York [u.a.]: McGraw Hill 2. Tamime, A. Y. “Membrane Processing Dairy and Beverage Applications”. Chicester: Wiley. 3. Rizvi, Anil Kumar; Pabby, Ana Maria; Sastre, Syed S.H., eds. (2007). “Han dbook of membrane separations : chemical, pharmaceutical, and biotechnological applications.” Boca Raton, Fla.: CRC Press. 4. Clever, M.; Jordt, F.; Knauf, R.; Rabiger, N.; Rudebusch, M.; Hilker-Scheibel, R. (1 December 2000). "Process water production from river water by ultrafiltration and reverse osmosis". Desalination. 131 (1-3): 325-336. 5. Tamime, A. Y. “Membrane Processing Dairy and Beverage Applications.” Chicester: Wiley 6.Kaustubha Mohanty, Mihir K. Purkait; “Membrane technologies and applications” 2012, CRC Press 7.Kandori, K., Schechter, R.S.; “Selection of surfactants for micellar- enhanced ultrafiltration”, Separation Science and Technology (1990), 25(1-2), 83-108 8.Ponisseril Somasundaran, Shaohua Lu; ”REMOVAL OF CONTAMINANTS FROM WATER USING SUGAR BASED SURFACTANT ENHANCED ULTRAFILTRATION”, US Patent no 8,002,988 9.Puasa S.W., Ruzitah M.S and Sharifah A.S.A.K; “An Oerview of Micellar - Enhanced Ultrafiltration in Wastewater Treatment Process”, IPCBEE vol.12 (2011) 10.Lehmler, HJ (2005). "Synthesis of environmentally relevant fluorinated surfactants-a review". Chemosphere. 58(11): 1471-96. 11.Renner R (2006). "The long and the short of perfluorinated replacements". Environ. Sci. Technol. 40 (1): 12-3. 12.Calafat AM, Wong LY, Kuklenyik Z, Reidy JA, Needham LL (2007). "Polyfluoroalkyl chemicals in the U.S. population: data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and comparisons with NHANES 1999-2000". Environ. Health Perspect. 115 (11): 1596-602 13.Berger, U., Glynn, A., Holmstrom, K.E., Berglund, M., Ankarberg, H.E., Tornkvist, A.; ” Fish consumption as a source of human exposure to perfluorinated alkyl substances in Sweden - Analysis of edible fish from Lake Vattern and the Baltic Sea”, Chemosphere, Volume 76, Issue 6, August 2009, Pages 799-804 14.McCleaf, P., Englund, S., Ostlund, A., Lindegren, K., Wiberg, K., Ahrens, L.; ” Removal efficiency of multiple poly- and perfluoroalkyl substances (PFASs) in drinking water using granular activated carbon (GAC) and anion exchange (AE) column tests”, Water research, Volume 120, 1 September 2017, Pages 77-87 15.Busch, J., Ahrens, L., Sturm, R., Ebinghaus, R.; ”Polyfluoroalkyl compounds in landfill leachates”, Environmental pollution, Volume 158, Issue 5, May 2010, Pages 1467-1471

Claims

1. 1. A method for removing PFAS from a PFAS-containing aqueous phase, comprising: (i) adding to said aqueous phase a surfactant composition comprising at least one cationic surfactant and allowing said surfactant to form micelles in said aqueous phase; (ii) contacting the micelle-containing aqueous phase with an ultrafiltration membrane under pressure to obtain a permeate stream aqueous phase having a reduced concentration of PFAS; The method includes:

2. The method of claim 1, wherein the surfactant comprises a C4 to C20 aliphatic group as the hydrophobic portion.

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

4. The PFAS may be perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluorobutanesulfonic acid, perfluorohexanesulfonic acid, perfluorooctane sulfonic acid, 6:2 fluorotelomer sulfonate, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentanesulfonic acid, perfluoroheptanesulfonic acid, perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 4:2 fluorotelomer 4. The method of any one of claims 1 to 3, comprising one or more of the following: sulfonate, 8:2 fluorotelomer 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.

5. 5. The method of claim 1, wherein the ultrafiltration membrane has a molecular weight cutoff of 100,000 Daltons or less.

6. 6. The method of any one of claims 1 to 5, wherein the ultrafiltration membrane has a molecular weight cut-off in the range of 1,000 to 30,000 Daltons.

7. The method of claim 1 , wherein the surfactant composition comprises at least one nonionic surfactant.

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

1.

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

1.

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

1.

11. 11. The method of claim 1, comprising repeating (i) and (ii) at least once.

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

13. 13. The method of claim 1, further comprising the steps of: (iii) determining a concentration of one or more PFAS in the permeate stream aqueous phase having a reduced concentration of PFAS, and repeating (i) and (ii) if the determined concentration is above a predetermined threshold.

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

15. 15. The method of any one of claims 1 to 14, wherein the aqueous phase contains PFAS at an initial concentration in the range of 0.1 μg / L to 10 g / L.

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