Method for removing pfas with various chain lengths in a single system

Patent metadata

Field	Value
Publication number	US-2026070818-A1
Application number	US-202519323653-A
Country	US
Kind code	A1
Filing date	Sep 9, 2025
Priority date	Sep 9, 2024
Publication date	Mar 12, 2026
Grant date	—

Abstract

A method for removing PFAS from a feed solution includes: flowing a feed solution comprising PFAS of varying chain lengths through a feed channel; applying a voltage to a first electrode and a second electrode in a redox channel separated from the feed channel by a first SEM, the first electrode becoming positively charged and the second electrode becoming negatively charged, wherein the PFAS in the feed solution transfer through the first SEM into the redox channel toward the first electrode; and separating PFAS based on chain length, wherein long-chain PFAS adhere to the first electrode through hydrophobic and electrostatic interactions, and short-chain to ultra-short chain PFAS migrate toward the second electrode in the redox channel and pass through a second SEM into an accumulating channel, thereby creating a PFAS-concentrated solution in the accumulating channel.

First claim

1 . A method for removing per-and polyfluoroalkyl substances (PFAS) from a feed solution, the method comprising:
flowing a feed solution comprising PFAS of varying chain lengths through a feed channel; applying a voltage to a first electrode and a second electrode in a redox channel separated from the feed channel by a first size exclusion membrane (SEM), the first electrode becoming positively charged and the second electrode becoming negatively charged, wherein the PFAS in the feed solution transfer through the first SEM into the redox channel toward the first electrode; and separating PFAS based on chain length, wherein
long-chain PFAS adhere to the first electrode through hydrophobic and electrostatic interactions, and
short-chain to ultra-short chain PFAS migrate toward the second electrode in the redox channel and pass through a second SEM into an accumulating channel, thereby creating a PFAS-concentrated solution in the accumulating channel.

2 . The method of claim 1 , wherein the SEM comprises a nanofiltration (NF) membrane.

3 . The method of claim 2 , wherein the SEM comprises a NF membrane with a molecular weight cut-off of greater than about 800 Da.

4 . The method of claim 1 , wherein
the ultra-short-chain PFAS comprises trifluoroacetic acid (TFA) or perfluoropropanoic acid (PFPrA); the short-chain PFAS comprises perfluorobutanoic acid (PFBA); and the long-chain PFAS comprises perfluorohexanoic acid (PFHxA) or perfluorooctanoic acid (PFOA).

5 . The method of claim 1 , further comprising:
flowing the PFAS-concentrated solution into an electrochemical oxidation system comprising two electrodes that are oppositely charged during operation.

6 . The method of claim 1 , further comprising:
obtaining, after separating PFAS based on chain length, the first electrode with adhered PFAS; placing the first electrode with adhered PFAS into an electrochemical oxidation system; and applying a negative voltage to the first electrode to facilitate release of the adhered PFAS.

7 . The method of claim 1 , further comprising:
flowing the PFAS-concentrated solution from the accumulating channel into an electrochemical oxidation system comprising the first electrode with adhered PFAS and another electrode, wherein the adhered PFAS comprises the long-chain PFAS; and applying a negative voltage to the first electrode and a positive voltage to the other electrode, wherein the adhered PFAS is released from the first electrode, and the long-chain and short-chain to ultra-short chain PFAS in the solution are defluorinated.

8 . The method of claim 5 , wherein the electrode that is positively charged during operation is boron-doped diamond (BDD) electrode.

9 . The method of claim 1 , wherein a water-soluble redox polymer circulates through the redox channel during application of the voltage, repetitively oxidizing near the first electrode and reducing near the second electrode; and
the water-soluble redox polymer comprises a redox-active moiety and a water-soluble moiety.

10 . The method of claim 9 , wherein the redox-active moiety comprises 2,2,6,6-tetramethyl-1-piperidinyloxymethacrylate (TMA).

11 . The method of claim 9 , wherein a molar ratio of a redox-active moiety within the water-soluble redox polymer is greater than about 20%.

12 . The method of claim 6 , wherein the water-soluble redox polymer comprises a terpolymer.

13 . The method of claim 10 , wherein the terpolymer is poly(2,2,6,6-tetramethyl-1-piperidinyloxymethacrylate-co-2,2,6,6-tetramethyl-1-piperidylmethacrylate-co-[2-(methacryloyloxy)ethyl]trimethyl-ammonium chloride) P(TMA-co-TMPMA-co-METAC).

14 . The method of claim 6 , wherein an average molecular weight (Mn) of the redox polymer is in a range from about 1,000 g/mol to about 5,000 g/mol.

15 . The method of claim 1 , wherein the first electrode and the second electrode in the redox channel comprise activated carbon cloth electrodes.

16 . The method of claim 1 , the method further comprising:
desalinating the feed solution to a potable water level during PFAS removal process.

17 . The method of claim 1 , wherein the method eliminates greater than about 80% of PFAS from the feed solution.

18 . A redox-polymer ED system for removing PFAS from a feed solution, the system comprising:
a first electrode;
a second electrode positioned in opposition to the first electrode;
a first SEM and a second SEM positioned between the first and second electrodes;
a cation exchange membrane (CEM) positioned between the first and second SEMs, the CEM defining a feed channel and an accumulating channel between the SEMs; and
a redox channel containing the first and second electrodes and being separated from feed and/or accumulating channels by the pair of SEMs,
wherein the feed channel is configured for flow of the feed solution comprising PFAS of varying chain lengths, wherein the redox channel is configured for flow of a redox solution comprising a redox polymer, wherein the first electrode is configured for electrosorption of long-chain FPAS upon application of a positive voltage, and wherein the accumulating channel is configured to collect and concentrate short-chain to ultra-short chain PFAS removed from the feed solution.

19 . The redox-polymer ED system of claim 18 , wherein the redox polymer comprises P(TMA-co-TMPMA-co-METAC).

20 . A system for defluorination of PFAS, comprising:
the redox-polymer ED system of claim 18 ; and an electrochemical oxidation system configured to receive a concentrated solution of short-chain to ultra-short chain PFAS in the accumulating channel of the redox-polymer ED system, wherein the electrochemical oxidation system comprises two electrodes, one of the two electrodes being the first electrode from the redox-polymer ED system obtained after electrosorption of the long-chain PFAS.

Assignees

• Univ Illinois

Inventors

• Su Xiao
• Kim Nayeong
• Elbert Johannes

Classifications

• B01D61/422

  Electrodialysis · CPC title

• B01D61/027

  Nanofiltration · CPC title

• C02F1/46109

  Electrodes · CPC title

• C02F2101/36

  containing halogen · CPC title

• C02F2101/34

  containing oxygen · CPC title