In situ formation and activation of high-volume H2O2 in micro-nano dendritic ZVC/air system for enhanced Fenton-like degradation of metronidazole

Fenton-like technology based on in situ formation of H2O2 by activated molecular oxygen has a promising application prospect in the degradation of organic pollutants, which can reduce the environmental and security problems caused by excessive use of H2O2 in traditional Fenton technology. We constructed a micro-nano dendritic zero-valent copper catalyst (mnZVC) by the simple electrochemical reduction, and studied the performance, mechanism and degradation pathway of mnZVC-activated molecular oxygen for the degradation of metronidazole (MNZ). In mnZVC/air system, metronidazole (MNZ) removal efficiency reaches 92.39% within 120 min under pH 3, much higher than that of commercial micron zero-valent copper. In addition, mnZVC has versatility to degrade phenol, methyl orange (MO), rhodamine B (RhB) and tetracycline hydrochloride (TCH). The continuous high-volume generation of H2O2 is the main reason for the high efficient removal of MNZ, which is attributed to the micro-sized dispersibility and nano-sized activity of the mnZVC. Besides, •OH and •O2− are proved to be the main active species directly causing MNZ degradation by free radical scavenging experiments and other analysis. Based on the results of LC-MS, the primary degradation intermediates of metronidazole were identified, and three possible degradation pathways were proposed. This work provides a new idea for the design of catalyst with in situ generated H2O2 for degradation of organic contaminants.