Two major deactivation mechanisms in carbon-based advanced oxidation processes (AOPs) dominated by electron-transfer pathway (ETP)

Carbon-based advanced oxidation processes through electron-transfer pathway are regarded as a green technology for efficient and selective oxidation of the emerging pollutants in complex water matrixes. Despite achievements in the superior activity and selectivity for organic degradation of carbocatalysts, their stabilities remain unsatisfactory, primarily because of the underexplored deactivation mechanisms. This study identifies two distinct deactivation mechanisms. The first is Oxidant Deactivation, due to overoxidation by the oxidant and predominantly affected by the concentration of oxidant. The other is Organic Deactivation, primarily caused by attachment of organic byproducts on catalyst surface, which reduces the overall oxidation potential of carbon/persulfate complex, instead of covering the surface “active sites”. Furthermore, the deactivation mechanisms mainly depend on intrinsic catalytic pathways: Oxidant Deactivation originates from the adjacent transfer pathway and Organic Deactivation from the electron shuttle pathway. Finally, the relationship between the deactivation mechanisms and carbon configuration (sp 2 /sp 3 ) is revealed, and a catalyst with optimal activity and stability can be achieved through properly regulating the sp 2 /sp 3 ratio. Results indicate that different protective strategies and application scenarios should be adopted for different systems to extend their lifespan in real wastewater treatment. This work sheds light on rational catalyst design toward advanced water purification systems with high efficiency and stability.