Electron-transfer pathways insights into contaminants oxidized by Cu-OOSO₃^- intermediate: Effects of oxidation states...

The copper-peroxy complex (Cu-OOSO₃^-) metastable intermediate has been confirmed to oxidize contaminants via a single-electron-transfer pathway or an oxygen-atom-transfer pathway. And the effects of Cu oxidation states and reaction pH conditions on the intermediate properties have not been explored in depth. Here, copper oxide (CuO_x) catalysts with different Cu oxidation states were synthesized by a simple precipitation method by controlling the reaction temperature from 0 to 45 °C. CuO_x displayed a strong catalytic dependence on the Cu oxidation state, and CuO_x-30 with Cu average valence on the catalyst surface of 1.61 was more reactive for catalytic degradation of bisphenol A with peroxymonosulfate (PMS). Notably, CuO_x-30, with the best electron-accepting ability, was easier to bonding with PMS to form the Cu-OOSO₃^- reactive complex, and the generated intermediate exhibited the strongest capacity to obtain electrons from contaminants. Moreover, the electron-transfer pathways were closely related to the average valence of Cu, and the contribution of the oxygen-atom-transfer pathway changed volcanic with increasing Cu valence. Meanwhile, the reaction predominantly involved the oxygen-atom-transfer pathway under acidic conditions (pH=3), while the contribution of the single-electron-transfer pathway raised with increasing pH values. Hence, this work was devoted to providing new insights into the CuO_x-inducing PMS activation and vital supplementary to the properties of the Cu-OOSO₃^- intermediate.