A highly efficient electrolysis catalyzed ozone (ECO) process was developed for N,N-dimethylacetamide (DMAC) degradation. The pseudo-first-order rate constants (kobs) of DMAC degradation by ECO process were 1.73-19.09 times greater than those by ozonation and electrolysis processes in a wide pH range of 3.0-10.0. Interestingly, we found O2•- could be generated from ozone decomposition by a radical chain mechanism instead of monovalent reduction of O2 in ECO system at the initial pH of 3.0. Subsequently, the H2O2 derived from O2•- could participate in Fenton-like and peroxone reactions with the released Fe2+ from iron anode and the aerated O3, respectively. Therefore, the extraordinary DMAC removal efficiency was mainly caused by the more generation of •OH through the multiple reactions of homogeneous catalytic ozonation, Fenton-like and peroxone in ECO system. Importantly, the roles of involved reactions in ECO system at various initial pH were quantitatively evaluated according to a series of trapping experiments. The results reveal that the solution pH could significantly affect the contributions of various reactions and convert the reaction mechanisms of multiple reactions in ECO system. Finally, the degradation intermediates were detected to propose a possible DMAC oxidation pathway in the ECO system. This work provides a deep insight into the quantitative analysis of the role of multiple oxidation reactions mechanism and the design of efficient electrochemical advanced oxidation technology for recalcitrant organic pollutant removal.
Keywords: Electrolysis; N,N-dimethylacetamide; Ozone; Quantitative analysis; Reaction mechanism; Reactive oxygen species.
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