Gas–Liquid Interface Enhanced Selective Adsorption of Long-Chain PFAS by Novel Floating Macroporous Resins

Abstract Long-chain per- and polyfluoroalkyl substances (PFAS) in industrial wastewater are a significant source of PFAS contamination. Anion exchange resin (AER) adsorption is an advantageous technology for PFAS removal, but existing AERs suffer from limited selectivity. In this study, our synthesized novel macroporous AERs with asymmetric long-chain amine groups, MP-(12–1–1) and MP-(16–1–1), exhibited a unique floating behavior on the water surface after drying and achieved significantly enhanced PFAS removal from chromium-plating wastewater, with the gas–liquid interface playing a critical role. Molecular dynamics simulations revealed that the rough surfaces and hydrophobic functional groups of the dry MP-(12–1–1) and MP-(16–1–1) enable them to maintain the Cassie wetting state in water without transitioning to the Wenzel state, thereby forming a stable gas–liquid interface. The gas–liquid interface exhibited adsorption free energies reaching −7.6 to −9.5 kcal/mol for long-chain PFAS, increasing the selectivity of the floating macroporous AERs for various long-chain PFAS by 6–81 times. This provides a new approach for the efficient removal of long-chain PFAS and offers new insights for the design of selective adsorbents based on the gas–liquid interface.