Highly Efficient and Mild Electrochemical Incineration: Mechanism and Kinetic Process of Refractory Aromatic Hydrocarbon Pollutants on Superhydrophobic PbO2 Anode

Aqueous aromatic hydrocarbons are chemically stable, high toxic refractory pollutants that can only be oxidized to phenols and quinone on either Pt or traditional PbO2 electrodes. In this study, a novel method for the electrochemical incineration of benzene homologues on superhydrophobic PbO2 electrode (hydrophobic-PbO2) was proposed under mild conditions. Hydrophobic-PbO2 can achieve the complete mineralization of aromatic hydrocarbons and exhibit high removal effect, rapid oxidation rate, and low energy consumption. The kinetics of the electrochemical incineration was also investigated, and the results revealed that the cleavage of the benzene ring is a key factor affecting the incineration efficiency. Moreover, on hydrophobic-PbO2, the decay of intermediates was rapid, and low concentrations of aromatics were accumulated during the reaction. The removal of the initial pollutants and the effects of oxidative cleavage were related to the number of methyl groups on the benzene ring. Specifically, the results of physical experiments and quantum calculations revealed that the charge density of carbon atoms increases with an increase in the number of methyl groups, which promotes the electrophilic attack of center dot OH.