Kinetic Selectivity of an Electric Field-Induced Nonradical Pathway for Catalytic Oxidation of Phenolic Pollutants by Molecular Oxygen

Nonradical oxidation is a promising pathway for the selective removal of organic pollutants in complex wastewaters. However, traditional catalytic oxidation processes generally depend on free radicals to achieve favorable pollutant removal. Herein, we developed a nonradical pathway-governed catalytic oxidation process by applying an electric field to selectively activate a surface O2-complex on a MnO catalyst. On the surface of positively polarized MnO, adsorbed O2 was activated into positively charged peroxide species as the main reactive species. A Langmuir–Hinshelwood model based on irreversible bimolecular reaction between adsorbed reaction species was developed to kinetically differentiate the oxidation behaviors of twelve substituted phenolic compounds. The surface reaction rate constant was identified as the key parameter controlling the reaction kinetics. To unveil the substrate-dependent reaction rules of the nonradical pathway, quantitative structure–activity relationship (QSAR) analysis was performed to correlate the surface reaction rate constants of phenolic compounds to their molecular features. A QSAR model was constructed by synergizing IE, EHOMO, and q(C–)n together to predict the reactivity of a phenolic compound in the nonradical pathway. Guided by the QSAR model, the catalytic oxidation process was applied for safe and energy-saving treatment of triclosan-contaminated water. This work is anticipated to provide valuable information for triggering and manipulating nonradical catalytic oxidation processes as well as understanding their selective oxidation nature.