Interfacial electron modulation and molecular passivation: Suppression mechanisms of microplastics on dual oxidation...

The widespread coexistence of microplastics (MPs) and organic pollutants in water presents the challenges for advanced oxidation processes. Although the O₃/H₂O₂ system demonstrated efficient degradation of various pollutants, its effectiveness with the background of microplastics (MPs), particularly those subjected to environmental aging, remains poorly understood and inadequately quantified. This work systematically investigated the inhibitory effects of pristine and aged MPs on the O₃/H₂O₂ system and elucidated the underlying mechanisms through experimental and theoretical analyses. The findings revealed pollutant-specific dual oxidation pathways: electron-rich compounds underwent concurrent •OH-mediated oxidation and direct O₃ molecular oxidation, whereas electron-deficient pollutants were degraded exclusively via •OH attack. Pristine MPs mainly suppressed degradation through physical adsorption. In contrast, aged MPs with oxygen-rich surfaces induced stronger inhibition by stabilizing O₃, altering interfacial electron transfer and promoting inefficient surface consumption. Crucially, the O₃/H₂O₂ system maintained high pollutant removal efficiency in real water matrices despite MPs-induced inhibition, and also exhibited no ecotoxicity in plant growth assays and yielded favorable life cycle outcomes. This study establishes a mechanistic foundation for optimizing advanced oxidation in microplastic-coexisted environments and demonstrated the practical feasibility of the O₃/H₂O₂ system for such applications.