Removal of short- and long-chain PFAS from aquatic systems using electrostatic attraction of polyethylenimine-polyvinyl chloride electrospun nanofiber adsorbent

The presence of perand polyfluoroalkyl substances (PFAS) in the water environment raises serious concerns due to their persistence and toxicity that links to adverse health consequences. Short-chain PFAS are more challenging to remove from water by adsorption than long-chain PFAS due to the weaker hydrophobic interaction, and conventional adsorbents usually demonstrated poor PFAS adsorption capacities near neutral pH. We have examined a novel polyethylenimine-polyvinyl chloride electrospun nanofiber (PEI-PVC NF) adsorbent to improve the adsorption capacity of both short-[perfluorobutanoic acid (PFBA) and perfluorobutanesulfonic acid (PFBS)] and long-chain [perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)] PFAS by maximizing electrostatic attraction using a PEI functional group with nanopore structure. At pH 7, PEI-PVC NF demonstrated adsorption capacities of 84.26 mg/g for PFBA and 214.37 mg/g for PFBS (short-chain PFAS), and 213.76 mg/g for PFOA and 326.39 mg/g for PFOS (long-chain PFAS). These adsorption capacities were only 20.1-61.3% lower than those obtained under acidic conditions. Excellent adsorption capacities by PEI-PVC NF are likely due to the strong electrostatic attraction with PEI under acidic to neutral pHs as well as pore-mediated adsorption driven by nanopore structure. The isotherm adsorption data were well fitted with the Langmuir model, which supports dominant monolayer adsorption driven by electrostatic attraction. Maximum adsorption capacities (qmax, 98.70 mg/g for PFBA, 222.36 mg/g for PFBS, 234.85 mg/g for PFOA, and 319.82 mg/g for PFOS) were superior to adsorbents that were previously reported at pH 7. Adsorption kinetic tests demonstrated remarkable PFAS adsorption rates (reached equilibrium in 300 min) by PEI-PVC NF likely driven by electrostatic and intraparticle diffusion into nanopores.