Process optimization and mechanism study of acid red G degradation by electro-Fenton-Feox process as an in situ generation of HO.

Dye-contaminated wastewaters are industrial wastewaters that are difficult to treat using traditional biochemical and physicochemical methods. In the present work, the acid red G was removed as a model pollutant by the electro-Fenton process for the first time. The anode and cathode used by the electro-Fenton process were iron plate and graphite felt, respectively. It was concluded that under the optimal conditions of current density = 20 mA cm, pH = 3 and initial NaSO concentration = 0.2 M, the removal rate of acid red G (ARG) with an initial concentration of 300 mg L could reach 94.05% after 80 min of electrolysis. This reveals that the electro-Fenton-Feox process used in this work has an excellent removal efficiency on acid red G. The required reagents (Fe and HO) were generated by the electrode reaction, while the optimal generation conditions and mechanism of •OH, HO, and Fe were investigated. By testing •OH, HO, and Fe agents at different pH and current densities, it was revealed that the electro-Fenton reaction was most efficient when the current density was 20 mA cm, and the pH was 3. Moreover, the removal rate of ARG is consistent with first-order reaction kinetics.