Synthesis of an anion exchange resin for enhanced PFAS adsorption in water treatment†

Abstract

Per- and polyfluoroalkyl substances (PFASs) are a class of toxic, bioaccumulative, and persistent chemicals that pollute natural water sources and the environment, new materials and methods to remove them from water are needed. Anion exchange resins adsorb PFASs through strong electrostatic interactions with negatively charged PFAS molecules with high selectivity and removal efficiency from contaminated water. A series of cross-linked anion exchange resins in the form of polymeric beads were synthesized via inverse suspension polymerization using commercially available cationic monomers, (3-acrylamidopropyl)-trimethylammonium chloride (APTMAC) or diallyldimethylammonium chloride (DADMAC), and the crosslinker, N,N′-methylenebisacrylamide (BisAAm).The resins were evaluated for their ability to remove perfluorooctanoic acid (PFOA) from water and the DADMAC based resin (DR4) with 10 w/w% crosslinker showed the highest efficiency. DR4 exhibits high adsorption capacities of 3300 mg g⁻¹ for PFOA, coupled with rapid adsorption kinetics, achieving equilibrium within an hour. Minimum interference effects from salts, pH variations, and natural organic matter (NOM) were observed and the competitive adsorption study indicated that the presence of other PFASs had no impact on the adsorption efficiency of DR4. DR4 was washed and reused, maintaining its performance after five consecutive PFOA adsorption and desorption cycles.