Highly selective and ultimate removal of typical PFAS from drinking water using anion exchange resins with long alkyl chains

Anion exchange resin (AER) adsorption is an effective technology for removing per- and polyfluoroalkyl substances (PFAS) from drinking water. However, conventional AERs exhibit poor adsorption selectivity, and the adsorption differences among different amine functional groups for low-concentration PFAS in drinking water remain unclear. In this study, multiple AERs with different amine groups were synthesized, and the structure-selectivity relationship of AERs for PFAS adsorption was revealed through competitive adsorption experiments. It was found that AERs with hydrophobic long alkyl chains, strong-base quaternary amine groups, and gel-type pore structures demonstrated higher adsorption selectivity for PFAS. Furthermore, the removal efficiency of low-concentration PFAS in drinking water by AERs was highly correlated with adsorption selectivity. Based on these findings, a synthesized gel-type strong-base AER with long alkyl chains (Gel(12-1-1)) was selected as the optimal AER, and its adsorption performance for PFAS in drinking water was evaluated through rapid small-scale column tests (RSSCTs). During the treatment of 180,000 bed volumes (BV), the effluent concentrations of PFBS, PFHxS, PFOS, PFOA, PFNA and GenX consistently remained below 10 ng/L. If targeting the U.S. drinking water regulatory limit of 4 ng/L for PFOS and PFOA, the commercial resin PFA694E could only treat 42,000 BV of water, whereas Gel(12-1-1) could treat 97,000 BV, demonstrating a significant advantage. This study not only provides an efficient and practical material for PFAS adsorption from drinking water, but also establishes a theoretical basis for the selective and ultimate removal of low-concentration PFAS.