Intrinsic Electric Field Triggers Phenol Oxidative Degradation at Microbubble Interfaces

Phenol, recognized for its environmental persistence and toxicity, typically necessitates high-energy or costly catalytic methods for its removal from industrial wastewater. In this study, we demonstrate the oxidative degradation of phenol at air–water interfaces (AWIs) by microbubbling air through water. High-resolution mass spectrometry revealed the transformation of phenol into progressively oxidized intermediates and ultimately into acetic acid, with a degradation rate of over 96% after 3 h for a 2 mM phenol solution. Complementary vortex experiments constructed a detailed degradation pathway involving sequential hydroxylation, dehydrogenation, and ring-cleavage processes. Radical scavenger experiments and DFT calculations indicate that the mechanism may follow an interfacial electric field-induced excitation pathway via radical reactions. The oxidation trend of para-halogenated phenols (F < Cl < Br < (H) < I) aligns with each radical’s HOMO–LUMO gap, supporting the interfacial field-induced molecular activation mechanism. Compared to conventional advanced oxidation processes, our method offers reagent-free operation, reduced secondary pollution, and high efficiency under mild conditions. These findings highlight the AWI-mediated oxidation as a sustainable strategy for degrading phenolic pollutants in water.