O<sub>2</sub>-Involved Electro-activation of Persulfate on Oxidized Carbon Black for Effective Sulfamethoxazole Degradation: Key Role of Side-Reactive Oxygen Reduction
Xiyang Zou, Haichuan Zhang, Jianxin Geng, Shanshan Ye, Xinyu Hu, Zhenghao Zhang, Ji Li
Abstract
The oxygen reduction reaction (ORR) was an unavoidable side reaction in the electro-activating persulfate (PS) process, especially on the ORR-active carbon materials, which has usually been ignored in previous reports. In this work, the O 2 /N 2 -involved electro-activation of the PS system was constructed to confirm the role of side-reactive ORR on oxidized carbon black (OCB) for sulfamethoxazole (SMX) degradation. With O 2 involvement, 820.8 μM • OH was produced by PDS electro-activation, over 7 times more than 115.8 μM under N 2 aeration, leading to a high SMX removal of 90.6% (only 67.8% under N 2 aeration). Such a huge difference in • OH yield and SMX removal performance was mainly attributed to side-reactive 2e – ORR, in which as-generated H 2 O 2 was electro-activated to produce abundant • OH and form an advanced homogeneous • OH/SO 4 •– oxidation system via mutual transformation with gradual acidification. Meanwhile, the introduction of oxygen functional groups and defects on the surface of carbon black calcined at 600 °C (CB600) also contributed to the improvement of SMX removal performance, attributing to their enhancing effects on SMX electro-adsorption, PDS electro-activation, and O 2 electro-reduction. Thus, side-reactive oxygen reduction played the spontaneous and synergistic oxidation roles in the O 2 -involved electro-activating PS process, helping to design highly effective advanced oxidation systems in the future.