A non-radical activation of peroxydisulfate by CuO to selectively oxidize aminobenzenes to nitrobenzenes

Abstract

Activation of persulfate by transition metal oxides (TMOs) has been widely studied to solve environmental pollution. Notwithstanding the strong oxidability and the high purification efficiency, the radical oxidation route of activated persulfate suffers the low utilization rate of oxidant and the non-selective oxidation to produce hazardous secondary pollutants, as well as the effect of pH value in reaction system. In this study, we used CuO catalyst to activate peroxydisulfate (PDS) to selectively oxidize aromatic amino compounds (AACs) to aromatic nitro compounds (ANCs) through a non-radical pathway, not only effectively eliminating the harmful pollutants in wastewater, but also achieving high value-added products. By using p-chloroaniline (p-CAN) as a model pollutant, we studied the effect of catalyst morphology, concentrations of p-CAN and PDS, the pH value, and the presence of anion on the p-CAN conversion and the p-chloronitrobenzene (p-CNB) yield. Furthermore, the catalytic durability and the universality for other aniline derivatives were investigated. The results indicate that the CuO-activated PDS under the optimized conditions is an efficient strategy to selectively convert AACs to ANCs with high catalytic stability and good universality. Through characterizing the used catalyst with different technology and radical measurements, it was confirmed that the non-radical mechanism was the main oxidation route of p-CAN. Additionally, the intermediate products were detected and the possible reaction pathways were proposed.