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 (O-2) 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 (center dot OH) and superoxide anion radical (center dot O-2(-)) were identified as the main reactive oxygen species (ROSs) generated in the above reaction; however, only center dot OH caused the decomposition and mineralization of ACT in the copper-catalyzed O-2 activation process. In addition, the in-situ generated Cu+ from ZVC dissolution not only activated O-2 to produce H2O2, but also initiated the decomposition of H2O2 to generate center dot OH. Meanwhile, the H2O2 could also be partly decomposed into center dot O-2(-), which served as a mediator for copper cycling by reduction of Cu2+ to Cu+ in the ZVC/air system. Therefore, center dot 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 center dot O-2(-) during Cu-catalyzed activation of O-2, which further improved the understanding of O-2 activation mechanism by zero-valent metals. (C) 2016 Elsevier Ltd. All rights reserved.