Enhanced degradation of GenX in wastewater via iodide-assisted UV/sulfite system

Abstract

Widespread PFAS contamination raises global concerns due to their persistence and ecological risks. Advanced reductive processes (ARPs) have emerged as a promising PFAS remediation strategy. In this study, we investigated GenX degradation, a next-generation alternative to PFOA, using an alkaline UV/sulfite/iodide (UV/S+I) system. In this process, hydrated electrons create a strongly reductive environment that enables contaminant decomposition. The addition of iodide to sulfite significantly enhanced GenX decay, following the trend UV/S+I > UV/S > UV/I. Under optimal conditions (2 mM I⁻, 10 mM SO₃²⁻), 99 % GenX removal was achieved within 30 min in pure water, with a rate constant of 0.152 min⁻¹ and the highest energy efficiency (EE/O = 126 kWh m⁻³). Degradation was most effective at pH 12 and independent of initial GenX concentration. PFOA degraded 2.3 times faster than GenX under similar conditions. Transformation products included trifluoroacetic acid, pentafluoropropanoic acid, and six other compounds. Application to real wastewater showed GenX removal rates of 0–57 % and PFOA removal of 31–98 %, with better performance in treated wastewater. In model solutions, 100 % total defluorination was achieved. Overall, the optimized UV/S+I system demonstrates strong potential for removing both emerging and legacy PFAS from wastewater with elevated pH, supporting the development of sustainable environmental remediation technologies.