Electron-transfer pathways insights into contaminants oxidized by [tbnd]Cu-OOSO3- intermediate: Effects of oxidation states of Cu and solution pH values

Abstract

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 (CuOx) catalysts with different Cu oxidation states were synthesized by a simple precipitation method by controlling the reaction temperature from 0 to 45 °C. CuOx displayed a strong catalytic dependence on the Cu oxidation state, and CuOx-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, CuOx-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 CuOx-inducing PMS activation and vital supplementary to the properties of the Cu-OOSO3- intermediate.