Electrochemically-induced metal–oxygen bond Cu(II)-[rad]SO5− on novel CuBi2O4 anode for efficient peroxymonosulfate activation

Abstract

Transition metal oxide catalysts had the limitation of a slow electron transfer rate in activating peroxymonosulfate (PMS) during wastewater treatment. In this work, we developed a novel copper bismuthate (CuBi2O4) anode using a catalyst drop casting method to efficiently activate PMS through electrochemically induced metal–oxygen bonds for herbicide prometon (PMT) degradation. The PMT removal rate in the EC/CuBi2O4 anode/PMS system was 74.60 %, which was much greater than the simple superposition of CuBi2O4 catalyst-activated PMS alone (4.88 %) and FTO anode electrically activated PMS (32.15 %). The CuBi2O4 fixed on the anode surface accelerated the electron transfer efficiency between the interface employing the electric field, showing stronger PMS activation performance than the equivalent three-dimensional particle electrode system. The free radical quenching experiments illustrated that the degradation of PMT mainly proceeded through the free radical oxidation pathway dominated by SO4− and OH. In the EC/CuBi2O4 anode/PMS system, the traditional Cu+/Cu2+ cycle did not dominate the activation of PMS in the CuBi2O4 anode reaction. Raman experiment and open circuit potential results proved that the introduction of an electric field caused PMS to form the metal–oxygen bond Cu(II)-SO5− at the CuBi2O4 anode interface, and converted it into activated state PMS (PMS*), accelerating the interface electron transfer. The PMS* was more readily further activated by electrons and promoted water dissociation to form OH for pollutants degradation. The EC/CuBi2O4 anode/PMS system manifested stable purification performance for COD and emerging pollutants in high-salt pesticide wastewater, coupled with its superior economic benefits, possessing broad application prospects.