O2-Involved Electro-activation of Persulfate on Oxidized Carbon Black for Effective Sulfamethoxazole Degradation: Key Role of Side-Reactive Oxygen Reduction

The oxygen reduction reaction (ORR)was an unavoidableside reactionin the electro-activating persulfate (PS) process, especially on theORR-active carbon materials, which has usually been ignored in previousreports. In this work, the O-2/N-2-involved electro-activationof the PS system was constructed to confirm the role of side-reactiveORR on oxidized carbon black (OCB) for sulfamethoxazole (SMX) degradation.With O-2 involvement, 820.8 & mu;M (OH)-O-& BULL; was produced by PDS electro-activation, over 7 times more than115.8 & mu;M under N-2 aeration, leading to a high SMXremoval of 90.6% (only 67.8% under N-2 aeration). Such ahuge difference in (OH)-O-& BULL; yield and SMX removal performancewas mainly attributed to side-reactive 2e(-) ORR,in which as-generated H2O2 was electro-activatedto produce abundant (OH)-O-& BULL; and form an advanced homogeneous (OH)-O-& BULL;/SO4 (& BULL;-) oxidationsystem via mutual transformation with gradual acidification. Meanwhile,the introduction of oxygen functional groups and defects on the surfaceof carbon black calcined at 600 & DEG;C (CB600) also contributed tothe improvement of SMX removal performance, attributing to their enhancingeffects on SMX electro-adsorption, PDS electro-activation, and O-2 electro-reduction. Thus, side-reactive oxygen reduction playedthe spontaneous and synergistic oxidation roles in the O-2-involved electro-activating PS process, helping to design highlyeffective advanced oxidation systems in the future.