Copper–catalyzed activation of molecular oxygen for oxidative destruction of acetaminophen: The mechanism and superoxide-mediated cycling of copper species

In this study, the commercial zero-valent copper (ZVC) was investigated to activate the molecular oxygen (O2) for the degradation of acetaminophen (ACT). 50 mg/L ACT could be completely decomposed within 4 h in the ZVC/air system at initial pH 3.0. The H2O2, hydroxyl radical (OH) and superoxide anion radical (O2−) were identified as the main reactive oxygen species (ROSs) generated in the above reaction; however, only OH caused the decomposition and mineralization of ACT in the copper-catalyzed O2 activation process. In addition, the in-situ generated Cu+ from ZVC dissolution not only activated O2 to produce H2O2, but also initiated the decomposition of H2O2 to generate OH. Meanwhile, the H2O2 could also be partly decomposed into O2−, which served as a mediator for copper cycling by reduction of Cu2+ to Cu+ in the ZVC/air system. Therefore, OH could be continuously generated; and then ACT was effectively degraded. Additionally, the effect of solution pH and the dosage of ZVC were also investigated. As a result, this study indicated the key behavior of the O2− during Cu–catalyzed activation of O2, which further improved the understanding of O2 activation mechanism by zero-valent metals. [Display omitted] •The ZVC/air system was effective in degradation of ACT.•The Cu+ was responsible for activation of O2 to produce H2O2.•The O2− was formed via the decomposition of H2O2 in the ZVC/air system.•It was proved that the O2− mediated the copper cycling by reduction of Cu2+ to Cu+.