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 H 2 O 2 , hydroxyl radical ( OH) and superoxide anion radical ( O 2 − ) 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 O 2 activation process. In addition, the in-situ generated Cu + from ZVC dissolution not only activated O 2 to produce H 2 O 2 , but also initiated the decomposition of H 2 O 2 to generate OH. Meanwhile, the H 2 O 2 could also be partly decomposed into O 2 − , which served as a mediator for copper cycling by reduction of Cu 2+ 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 O 2 − during Cu–catalyzed activation of O 2 , which further improved the understanding of O 2 activation mechanism by zero-valent metals.