Indirect oxidation mechanism governing in P-rGO/Ti anode with C2-PO2/rGO configuration for efficient 2-Methyl-4-Isothiazolin-3-one electrooxidation

Abstract

A stable phosphorus-doped reduced graphene (P-rGO/Ti) anode applied in electrochemical oxidation was prepared for the degradation of 2-Methyl-4-Isothiazolin-3-one (MIT), a broad-spectrum biocide with high concentration and toxicity widely exists in reverse osmosis concentrates. The P-rGO/Ti anode had high oxygen evolution potential (2.434 V), which inhibited side reactions and accelerated the mineralization of MIT. The •OH quenching tests verified that the indirect oxidation on MIT degradation was up to 84.17 %, and the mechanism of indirect oxidation was proposed about the C2-PO2/rGO configuration of P-rGO was more conducive to adsorb H2O and supply electron, resulting in the elongated OH bond and then easily cleaved to produce more •OH via density functional theory calculations. Furthermore, an empirical kinetic model was established to predict MIT removal trend. The P-rGO/Ti electrode maintained favorable MIT removal efficiency and structural stability with a long-term operation experiment in 1200 min. Moreover, the degradation pathways of MIT were proposed based on UPLC-Q-TOF-MS analysis. This study profoundly reveals the indirect oxidation mechanism of different P-rGO configurations on inducing the generation of •OH, and provides a new perspective for the design of stable and efficient carbon materials in electrochemical oxidation for wastewater purification.