Polystyrene-based fluorinated ionic receptor for selective removal of perfluoroalkyl contaminants from water

Abstract

Even at very low concentrations, per- and polyfluoroalkyl substances (PFAS) pose a serious threat to human and animal health. Significant efforts have been made to develop water remediation technology for removing PFAS from the environment and groundwater, while also minimizing their discharge into the environment owing to their ubiquitous presence in consumer goods worldwide. In the context of developing selective ion-exchange polymers for PFAS remediation, this work reports the design of polystyrene-based fluorinated anion-exchange polymer bearing quaternary tetraaryl phosphonium cation moieties. The polymer was intended for high-performance and highly selective removal of commonly found PFAS contamination, such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and hexafluoropropylene oxide-dimer acid (HFPO-DA, trade name GenX for the corresponding ammonium salt), at environmentally relevant concentrations from deionized water, drinking water and lake water (Lake Martin, Louisiana). Rapid removal of PFAS from different water matrices with more than 90 % efficiency at 1 ppb starting concentration was observed. The ionic fluoropolymer designed herein favors PFOA, PFOS, and GenX anions over other competing inorganic anions or organic species in solution via irreversible anion exchange which was assisted by strong hydrophobic interactions with the fluorophilic polymer's backbone. The synthesis of the polymer, its structural characterization, and its function in the removal of PFAS in real water matrices were discussed. The findings of this study are significant for developing water purification systems that aim to selectively and rapidly separate perfluoroalkyl compounds from waters at environmental concentrations and beyond.