Rapid capture of perfluorooctanoic acid and perfluorooctane sulfonate at environmentally relevant concentrations via the ‘mesh trap’ of triazine-based polymer network: Mechanism and photocatalytic regeneration

Per- and polyfluoroalkyl substances (PFAS) pose a serious threat to groundwater (GW) environment worldwide due to their difficulty in removal and high toxicity. In this study, the ‘mesh trap’ of triazine-based polymerization network (SNW-1) demonstrated rapid capture performance for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) at environmentally relevant concentrations (1 μg/L). The SNW-1 can remove more than 90 % of PFOA and PFOS within 300 s and still maintain superior performance under four common GW anions and different [pH]0 (3 - 10). The removal degree of PFOA and PFOS is almost undetectable without SNW-1 dosage. Theoretical calculations were used to simulate the adsorption process and interfacial reaction mechanism in SNW-1/PFOA (Eads = −1.6717 eV) and SNW-1/PFOS (Eads = −1.2695 eV) systems. The adsorption of SNW-1/PFOA is stronger than SNW-1/PFOS. The typical van der Waals weak interactions between SNW-1 and PFOA were confirmed, which is slightly stronger than SNW-1/PFOS. In addition, SNW-1 regeneration in this paper was achieved in a photocatalytic activated peroxydisulfate (PDS) system which was different with previous reports. The desorption rates of PFOA and PFOS adsorbed on the surface of SNW-1 and the defluorination rate in the photocatalytic regeneration system were also tested. The photocatalytic regeneration mechanism between SNW-1 and PDS was electron transfer. And the electron transfer can be divided into three stages: strong adsorption of SNW-1/PDS (Eads = −2.1618 eV), electron transfer from SNW-1 to PDS and PDS cleavage. This study has a broad application prospect in the field of in-situ rapid resistance control of GW in PFAS contaminated sites and provides a theoretical support for environmentally friendly adsorbent regeneration technology. [Display omitted] •SNW-1 with mesh trap is constructed to provide a large number of conjugated electrons.•SNW-1 can rapidly capture environmentally relevant concentrations of PFOA and PFOS.•The -CF2CO2- of PFOA and -CF2SO3- of PFOS are absorbed with the mesh trap of SNW-1.•SNW-1 can be green regenerated in photocatalytic activation of PDS system.•Electron transfer mechanisms of SNW-1/PDS are revealed by DFT calculations.