Novel insights into Co synergy and electron-transfer pathways during the oxidation of contaminants by Cu-OOSO3- in CuCo2Ox/peroxymonosulfate system

Recently, the Cu-OOSO3- metastable intermediate have been proposed to be the main active substance of contaminant oxidation, which could degrade organics through oxygen-atom-transfer and single-electron-transfer pathways. Herein, a series of copper cobalt oxides was synthesized to further explore its active species and electron-transfer pathways in the PMS activation system. The CuCo2Ox precipitated a smaller nano-needle structure, more weak acid sites, and more Cu2+ and Co2+ contents on its surface. Notably, it exhibited excellent PMS activation performance due to the synergistic effect between Cu and Co. The single-electron-transfer pathway with radicals and singlet oxygen as active species participated in the oxidation reaction, and the oxygen-atom-transfer pathway also played an important role in the degradation of pollutants. Cu2+ was speculated to be the main active site for binding with PMS to form the Cu-OOSO3- active substances due to its strong complex ability. And the electron transfer of the Cu-O-Co bridge bond promoted an oxidation reaction between Cu-OOSO3- and the contaminant. Hence, this work provided new insights into the synergistic effect between Cu and Co sites and electron-transfer pathways of contaminants oxidation in the CuCo2Ox/PMS oxidation system.