Transition-metal-based catalysts for persulfate activation toward per- and polyfluoroalkyl substance degradation: mechanisms, performance, and perspectives

Per- and polyfluoroalkyl substances (PFAS) are extensively used as synthetic organic chemicals in various industrial productions that pose several harmful effects on human health and environment. In recent years, considerable research has focused on developing more efficient technologies for treating wastewater containing emerging contaminants. Sulfate-radical based advanced oxidation processes (SR-AOPs) have been given more attention because of their high oxidation potential and effectiveness in degrading emerging contaminants. This review examines persulfate (PS) activation mechanisms and evaluates the degradation of PFOA and PFOS in PS-based systems. These systems involve chemical activation based on transition-metal (TM) and transition-metal oxide (TMO) materials of monometallic and polymetallic compounds, layered double hydroxides (LDHs), co-catalysts, and various supported metal catalysts, including metal oxide support, carbon material support, metal–organic framework (MOF) support, natural mineral support, MXene, and others. Key operating parameters governing PFAS degradation and fluoride release are systematically assessed, and the proposed transformation pathways and reaction mechanisms are summarized. Furthermore, this review identifies current drawbacks and suggests scenarios for improving the PFAS removal in both laboratory and environmentally relevant real-world water treatment conditions.