Stainless-Steel Felt-Based Cathodic Electro-Fenton-Like Reaction toward Organic Pollutant Degradation with Electrochemical pH Regulation

The electro-Fenton (EF) process has emerged as a promising technology for wastewater treatment, but its industrial application is still limited by massive uses of acid, alkaline, and iron reagents, resulting in the increase of water salinity and the production of iron sludge. In this study, a green, efficient, and robust stainless-steel felt-based cathodic electro-Fenton-like reaction coupled with an electrochemical pH-regulation unit was developed for the p-nitrophenol (p-NP) degradation, which could acidify the original solution to ∼3.0. The p-NP degradation performance was associated with the cathode materials, and the stainless-steel felt had a superior activity toward the activation of H2O2 into •OH than those of titanium mesh and stainless-steel mesh. It was found that under the cathode potential of −1.2 V/SHE, approximately 100% of p-NP and 71% of COD could be removed at a H2O2 concentration of 150 mg L–1 within 2 h. Based on the radical quenching experiments and electrochemical analysis, the conversion of H2O2 to •OH was probably initiated by H* at the stainless-steel felt cathode. After electro-Fenton-like treatment, the electrochemically produced alkaline solution could partially neutralize the treated solution, reducing the consumption of alkali reagents, and the total salt before and after degradation is basically unchanged. This system demonstrated high stability, no iron reagent addition, and no salinity increase, in which the total energy consumption was approximately 2.45 kW h m–3. This work pioneers a method of pollution control rendered by the “electrocatalysis rather than chemical reagent” philosophy of low carbon and green chemistry, providing technical support for feasible industrial application.