Process optimization of ozone-resistant compounds degradation in electro-peroxone process: From removal performance to mechanism investigation

Electro-peroxone (EP) as an innovative advanced oxidation process exhibits substantial potential for the degradation of ozone-resistant compounds (ORCs). In this work, an electrochemically modified graphite felt (GF) served as the cathode of EP process, facilitating the rapid degradation of multiple ORCs including oxalic acid (OA), formic acid, acetic acid and pyruvic acid. Hydroxyl radical ( · OH) as the major reactive species was derived from three pathways, i.e., the conversion of O 3 , one-electron reduction of O 3 (1e − O 3 reduction) and the electro-driven peroxone (EDP) reaction. pH, current density and gas O 3 concentration profoundly impacted · OH formation via these three pathways. · OH tended to be generated with the increase of pH and current density, but there was also a risk of being quenched by carbonate and hydrogen peroxide. The excellent removal rate of OA (about 80 %) was obtained at pH of 5–9 and current density of 1–2 mA cm −2 . The formation pathway of · OH shifted from 1e − O 3 reduction to EDP reaction with the increase of gas O 3 concentration. Cathodic behaviors of the EP process showed that reducing current density and increasing of pH and gas O 3 concentration could inhibit the occurrence of undesired reactions (e.g., H 2 O 2 reduction and H 2 O reduction), and improve the competitiveness of EDP reaction. The new insights into the mechanism of · OH formation emphasized the crucial role of maximizing the EDP reaction for effective removal of ORCs.