Electrochemical Degradation of Perfluoroalkyl Sulfonates via Sulfonate to Carboxylate Conversion

Efficient, scalable, and well-understood methods for degrading per- and polyfluoroalkyl substances (PFAS) are essential for limiting their numerous negative human health and environmental effects. Electrochemical methods are promising for PFAS degradation but are currently not yet well developed for use in non-aqueous conditions relevant for PFAS sorbent regeneration without resorting to specialized electrode materials. Herein, we report the mediated electrochemical conversion of perfluoroalkyl sulfonates to carboxylates using commercial Pt electrodes in acetonitrile. Perfluorooctane sulfonate (PFOS) was converted primarily to perfluorooctanoic acid (PFOA) alongside several shorter-chain carboxylates through a proposed radical desulfonation and hydroxide coupling process explored in a detailed mechanistic study. Following the near-complete conversion of PFOS to perfluoroalkyl carboxylates, all species are mineralized to fluoride and non-fluorinated carbon byproducts using established low-temperature DMSO/NaOH conditions. HPLC-MS, ion chromatography, and quantitative nuclear magnetic resonance (NMR) methods determined a significant loss in fluorine and carbon balance after electrochemistry, which we attribute to the production of volatile byproducts. This degradation approach provides new insights into PFAS degradation mechanisms under highly oxidative, non-aqueous conditions and highlights the potential for organic electrochemistry to address environmental challenges by promoting controlled and selective destruction pathways for common organic pollutants.