Enhancement of H₂O₂ yield and TOC removal in electro-peroxone process by electrochemically modified graphite felt:...

Electro-peroxone (EP) is an emerging advanced oxidation process which combines electro-generation H₂O₂ and ozone for removing organic contaminants. In this paper, a platinum plate as anode, a method of electrochemical oxidation is adopted to modify graphite felt (GF) cathode to promote H₂O₂ yield and TOC removal from oxalic acid solution in EP process, its performance, mechanism and stability were discussed. Compared with original GF cathode, 2.6 times H₂O₂ yield can be achieved by the 5 min electrochemically modified GF (GF-5). The high electrochemical activity of the modified GF can be ascribed to introducing numerous surface oxygen-containing functional groups (OGs), which not only decreased the impedance, but also increased the amount of active site of O₂ reduction. The production of H₂O₂ with GF-5 cathode improved with the increased initial pH, cathodic potential and O₂ flow rate, while this promoting effect was not observed in GF cathode. Compared with GF cathode, TOC removal rate was improved by 21.5% with GF-5 cathode due to higher H₂O₂ yield in EP process. The primary pathway of TOC removal is electrochemically-driven peroxone process, and hydroxyl radical (·OH) is the dominant reactive species. Furthermore, GF-5 cathode had a good stability due to the protection of H₂O₂ and free electrons injected. The results indicate that the electrochemically modified GF severed as the cathode of EP processes has significant efficiency and stability in the removal of ozone-refractory organic contaminants.