Enhanced degradation and defluorination of perfluorooctane sulfonate (PFOS) in tap water using gas-dispersed cold atmospheric plasma

Per- and polyfluoroalkyl substances (PFAS) are extremely persistent contaminants owing to the exceptional chemical stability of carbon–fluorine (C–F) bonds. Consequently, conventional wastewater treatments are largely ineffective, as they capture but fail to destroy PFAS, leading to the accumulation of concentrated wastes. In this study, we demonstrate that gas‑dispersion-assisted cold atmospheric plasma (CAP) enables rapid degradation and defluorination of perfluorooctane sulfonate (PFOS) in tap water. Operating under ambient conditions, CAP generates both oxidative and reductive reactive species, such as solvated electrons and hydroxyl radicals, which promote C–F bond cleavage. The introduction of air gas dispersion induces strong hydrodynamic mixing and enriches PFOS at the plasma–liquid interface, enhancing interfacial reactions and the availability of reactive species. At an initial PFOS concentration of 5 mg/L, gas‑dispersion–assisted CAP achieved 99.99% removal and 35% defluorination, following apparent first‑order kinetics with a rate constant of 0.42 1/min and a half‑life of 1.6 min. Transformation product (TP) analysis revealed stepwise degradation pathways of PFOS, and fluorine mass balance recoveries ranged from 31% to 106%. The lowest electrical energy per order ( EEO ) was achieved down to 39 kWh/m³/order. These results demonstrate that CAP can breakdown PFOS and represents a chemical‑free, and energy‑efficient approach for PFAS remediation in water systems.