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US-12623927-B2 - Functionalized layered double hydroxides for treatment of contaminated water

US12623927B2US 12623927 B2US12623927 B2US 12623927B2US-12623927-B2

Abstract

The present invention is directed at functionalized layered double hydroxides, including methods of their preparation, that are suitable for treatment of water contaminated with per- and polyfluoroalkyl substances.

Inventors

  • Shangping Xu
  • Yin Wang
  • Jingwan Huo

Assignees

  • UWM RESEARCH FOUNDATION, INC.

Dates

Publication Date
20260512
Application Date
20230629

Claims (20)

  1. 1 . A functionalized layered double hydroxide having the following formula: 3[M 2+ 1-x N 3+ x (OH)(A n− ) x/n -O]—Si(CH 2 ) a —(CF 2 ) b R′ wherein M 2+ and N 3+ are metal cations; A n− is an exchangeable anion, n is an integer of 1 or greater; 0<x<1; R′ represents an aromatic, CH 2 ═CH—, —CH 3 or —CF 3 group; if b=0, then a≥5; and if b>0, then a≥0.
  2. 2 . The functionalized layered double hydroxide of claim 1 wherein M 2+ is selected from the group consisting of Mg 2+ , Ca 2+ , Zn 2+ , Mn 2+ , and Fe 2+ .
  3. 3 . The functionalized layered double hydroxide of claim 1 wherein N 3+ is selected from the group consisting of Al 3+ and Fe 3+ .
  4. 4 . The functionalized layered double hydroxide of claim 1 wherein A n− is selected from the group consisting of NO 3 − and Cl − .
  5. 5 . The functionalized layered double hydroxide of claim 1 wherein when b=0 then a=5-19.
  6. 6 . The functionalized layered double hydroxide of claim 1 wherein when b=1-11, a=0-15.
  7. 7 . The functionalized layered double hydroxide of claim 1 wherein M=Zn, N=Al, A is NO 3 − , a=7 and R′ is —CH 3 .
  8. 8 . The functionalized layered double hydroxide of claim 1 wherein M=Zn, N=Al, A is NO 3 − , a=2, b=5 and R′ is —CF 3 .
  9. 9 . A method of preparation of a functionalized layered double hydroxide comprising: a. supplying an organofunctional silicon having the following formula: R′(CF 2 ) b (CH 2 ) a Si(OR) 3 wherein R′ represents an aromatic, CH 2 ═CH—, —CH 3 or —CF 3 group and (OR) represents an alkoxy group; if b=0, then a≥5 or if b>0 then a≥0; b. supplying a layered double hydroxide having the following formula: [M 2+ 1-x N 3+ x (OH 2 )] x+ (A n− ) x/n wherein M 2+ and N 3+ are metal cations and A n− is an exchangeable anion, n is an integer of 1 or greater, 0<x<1; c. combining said organofunctional silicon with said layered double hydroxide and forming a functionalized layered double hydroxide having the following formula: 3[M 2+ 1-x N 3+ x (OH)(A n− ) x/n -O]—Si(CH 2 ) n —(CF 2 ) b R′ wherein M 2+ and N 3+ are the metal cations; A n− is the exchangeable anion, n is the integer of 1 or greater; 0<x<1; R′ represents the aromatic, CH 2 ═CH—, —CH 3 or —CF 3 group; if b=0, then a≥5; and if b>0, then a≥0.
  10. 10 . The method of claim 9 wherein M 2+ is selected from the group consisting of Mg 2+ , Ca 2+ , Zn 2+ , Mn 2+ , and Fe 2+ .
  11. 11 . The method of claim 9 wherein N 3+ is selected from the group consisting of Al 3+ and Fe 3+ .
  12. 12 . The method of claim 9 wherein A n− is selected from the group consisting of NO 3 − and Cl − .
  13. 13 . The method of claim 9 wherein when b=0 then a=5-19.
  14. 14 . The method of claim 9 wherein when b=1-11, a=0-15.
  15. 15 . The method of claim 9 wherein M=Zn, N=Al, A is NO 3 − , a=7 and R′ is —CH 3 .
  16. 16 . The method of claim 9 wherein M=Zn, N=Al, A is NO 3 − , a=2, b=5 and R′ is —CF 3 .
  17. 17 . A method of removing per- and polyfluoroalkyl substances from contaminated water comprising: a. supplying a functionalized layered double hydroxide having the following formula: 3[M 2+ 1-x N 3+ x (OH)(A n− ) x/n -O]—Si(CH 2 ) n —(CF 2 ) b R′ wherein M 2+ and N 3+ are metal cations; A n− is an exchangeable anion, n is an integer of 1 or greater; 0<x<1; R′ represents an aromatic, CH 2 ═CH—, —CH 3 or —CF 3 group; if b=0, then a≥5; if b>0, then a≥0; b. treating said contaminated water with said functionalized layered double hydroxide and removing said per- and polyfluoroalkyl substances.
  18. 18 . The method of claim 17 wherein M 2+ is selected from the group consisting of Mg 2+ , Ca 2+ , Zn 2+ , Mn 2+ , and Fe 2+ .
  19. 19 . The method of claim 17 wherein N 3+ is selected from the group consisting of Al 3+ and Fe 3+ .
  20. 20 . The method of claim 17 wherein A n− is selected from the group consisting of NO 3 − and Cl − .

Description

CROSS-REFERENCE TO PRIOR APPLICATION This application claims priority to and the benefit of U.S. Provisional Application No. 63/356,677 filed Jun. 29, 2022 the entirety of which is incorporated by reference. GOVERNMENT SUPPORT CLAUSE This invention was made with government support under grant 1540032 awarded by the National Science Foundation. The government has certain rights in the invention. FIELD The present invention is directed at functionalized layered double hydroxides and methods of their preparation that are suitable for treatment of water contaminated with per- and polyfluoroalkyl substances. Background Per- and polyfluoroalkyl substances (PFAS) represent a class of synthetic chemicals containing a hydrophobic fluorinated carbon chain and various types of hydrophilic end/head functional groups such as alcohol, carboxylate, sulfonamide, sulfonate, and phosphonate. Because of their unique amphiphilic properties as well as their high chemical and thermal stability, PFAS have been used since the 1940s in a wide range of consumer, commercial, and industrial applications such as electronic manufacturing, industrial surfactants, paper and textile water proofing, metal plating and etching, surface treatment and protection, and firefighting foams. Many PFAS, such as perfluoroalkyl acids (PFAAs) and perfluoropolyether carboxylic acids (PFECAs), are remarkably persistent in nature, negatively charged under ambient pH conditions, and highly soluble in aquatic environment. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the two most examined PFAS within both scientific and regulation communities, and they have been detected in soil, groundwater and surface water. PFOS, PFOA, as well as their precursors, are currently listed under the Stockholm Convention on Persistent Organic Pollutants. The United States Environmental Protection Agency (USEPA) has proposed the National Drinking Water Regulation for six PFAS including PFOS and PFOA. The USEPA's fifth Unregulated Contaminant Monitoring Rule (UCMR5) further required the public water systems in the United States to monitor 29 PFAS between 2023 and 2025. Layered double hydroxides (LDHs), also known as anionic clays, are a family of layered minerals with a typical formula of [M2+1-xN3+x(OH)2]x+(An−)x/n·mH2O. The M2+ and N3+ are metal cations occupying the octahedral centers of the positively charged brucite-like structural layers, and An− is an exchangeable anion within the interlayers. Because of the high positive charge of the structural layer, LDHs generally exhibit positive surface charges over a range of environmentally relevant pH conditions, making them suitable for the adsorptive removal of anionic pollutants. However, LDHs are generally hydrophilic and the electrostatic interactions between LDHs and PFAS were considered the primary adsorption mechanism. Accordingly, a need remains to provide new and relatively more efficient LDHs to enhance their affinity with targeted PFAS compounds present in the environment and to provide a relatively more efficient LDH for treatment of water contaminated with PFAS substances. SUMMARY A functionalized layered double hydroxide having the following formula: 3[M2+1-xN3+x(OH)(An−)x/n-O]—Si(CH2)a—(CF2)bR′ wherein M2+ and N3+ are metal cations;An− is an exchangeable anion, n is an integer of 1 or greater;0<x<1;R′ represents an aromatic, CH2═CH—, —CH3 or —CF3 group;if b=0, then a≥5; andif b>0, then a≥0. A method of preparation of a functionalized layered double hydroxide comprising: a. supplying an organofunctional silicon having the following formula: R′(CF2)b(CH2)aSi(OR)3 wherein R′ represents an aromatic, CH2═CH—, —CH3 or —CF3 group and (OR) represents an alkoxy group; if b=0, then a≥5 or if b>0 then a≥0;b. supplying a layered double hydroxide having the following formula: [M2+1-xN3+x(OH2)]x+(An−)x/n wherein M2+ and N3+ are metal cations and An− is an exchangeable anion, n is an integer of 1 or greater, 0<x<1;c. combining said organofunctional silicon with said layered double hydroxide and forming a functionalized layered double hydroxide having the following formula: 3[M2+1-xN3+x(OH)(An−)x/n-O]—Si(CH2)a—(CF2)bR′ wherein M2+ and N3+ are metal cations;An− is an exchangeable anion, n is an integer of 1 or greater;0<x<1;R′ represents an aromatic, CH2═CH—, —CH3 or —CF3 group;if b=0, then a≥5; andif b>0, then a≥0. A method of removing per- and polyfluoroalkyl substances from contaminated water comprising: a. supplying a functionalized layered double hydroxide having the following formulae: 3[M2+1-xN3+x(OH)(An−)x/n-O]—Si(CH2)a—(CF2)bR′ wherein M2+ and N3+ are metal cations;An− is an exchangeable anion, n is an integer of 1 or greater;0<x<1;R′ represents an aromatic, CH2═CH—, —CH3 or —CF3 group;if b=0, then a≥5; if b>0, then a≥0; b. treating water with said contaminated water with said functionalized layered double hydroxide and removing said per- and polyfluoroalkyl substances. BRIEF