The novel double-working-electrode electrochemical system with air diffusion cathode (ADC) and Ti/SnO2-Sb anode (TSSA) has shown higher efficiency and lower energy consumption for the degradation of organic pollutant from high-salinity wastewater, compared to the traditional single anode system. To further investigate and improve this system, in this work, firstly the effect of vital factors of the double-working-electrode electrochemical system including initial methyl orange (MO) concentration, NaCl concentration and initial pH value of organic solution were investigated, using MO as the targeted organic pollutant, carbon black ADC (CBAC) as cathode and stainless steel mesh electrode (SSME) as control. Besides, for the further improvement of removal performance, a novel home-made activated carbon-ADC (ACAC) was studied as cathode with the same investigation process. The results showed that, in the experiments studying the effect of both initial MO and NaCl concentrations, the removal performance was in the order of TSSA-ACAC > TSSA-CBAC > TSSA-SSME in all conditions of initial MO and NaCl concentrations. However, with the pH value reduced from 6.0 to 3.0, the performances of three systems turned to be much closer to each other. Besides, ACAC played a synergistic role in MO removal by greatly improving the MO removal performance and enhancing its adaptability to the reactor parametric variation. ACAC created a weak acidic environment for accelerating the indirect electro-oxidation of MO on TSSA. The MO degradation pathways in the three systems were the same but the TSSA-ACAC system gave a higher degradation kinetics order.
Keywords: Electrochemical treatment; activated carbon; air diffusion cathode; high-salinity organic wastewater; synergistic mechanism.