Synergistic hydroxyl and chlorine radicals in contact-electro-catalysis for sustainable PFAS remediation

AbstractContact-electro-catalysis (CEC) provides a promising route for per- and polyfluoroalkyl substances (PFAS) remediation, yet the mechanistic role of chloride ions (Cl−) in real water matrices remains unclear. Here, we demonstrate that Cl− markedly enhances removal of perfluorooctanoic acid, perfluorooctanesulfonic acid, hexafluoropropylene oxide dimer acid, perfluorononyloxybenzene sulfonate, and 6:2 fluorotelomer sulfonate, achieving 97.04 −99.99% degradation and 96.90 −99.98% defluorination within 120 min at 200 mM Cl−. These rates were 1.43–2.29-fold higher than Cl−-free systems. Mechanistic analyses reveal that hydroxyl radicals (•OH) oxidizes Cl− to generate chlorine radicals (Cl•), which selectively attack the carboxylate group of PFAS, enabling thermodynamically favorable decarboxylation followed by mineralization. Unlike conventional electrochemical methods, the Cl•-mediated pathway avoids oxychlorine and chlorinated byproducts. Zebrafish embryo assays further confirmed negligible toxicity of treated solutions. These results establish a sustainable paradigm that achieves high defluorination efficiency and operational safety, offering strong potential for PFAS remediation in saline and industrial waters.