H2O2-catalyzed defluorination of perfluorooctanesulfonate (PFOS) by oxidized vanadium carbide MXene nanosheets

Abstract

Perfluorooctanesulfonate (PFOS) is a fluorinated synthetic surfactant in consumer end products that has been heavily investigated due to its global distribution, environmental persistence, and toxicity. Reductive processes that generate highly reactive reducing species called solvated electrons in water can destroy PFOS C–F bonds. However, solvated electrons are easily scavenged, which results in slow, incomplete defluorination. Heterogeneous catalysts may amplify PFOS defluorination, but the number of suitable catalysts for this process is limited. In this study, we examined PFOS defluorination by oxidized vanadium carbide (V₂C) MXene nanosheets in the presence of hydrogen peroxide (H₂O₂) under room temperature, ambient and aerobic conditions. 96% removal of 50 μg L⁻¹ PFOS was observed within 4 h by 0.15 mg mL⁻¹ V(V)–C nanosheets and 14.7 mM H₂O₂ compared to reaction systems containing only V(V)–C (62% removal) or H₂O₂ (no removal) in batch studies. And near-complete (105 ± 23%) defluorination of PFOS after four hours in this V(V)–C–H₂O₂ system following the formation and removal of trifluoroacetic acid—a short-chain degradation product. Solvated electrons (catalyzed by H₂O₂ addition) were hypothesized to contribute to the rapid defluorination of PFOS adsorbed to the V(V)–C surface. Our findings of V(V)–C-catalyzed reductive defluorination of PFOS could be applied to the treatment of other recalcitrant trace organic compounds in impacted water sources.