Hydroxyl radical and carbonate radical facilitate chlortetracycline degradation in the bio-photoelectrochemical system with a bioanode and a Bi2O3/CuO photocathode using bicarbonate buffer

The single-chamber bio-photoelectrochemical system (BPES) with a bioanode and a Bi2O3/CuO photocathode is developed for chlortetracycline (CTC) degradation under simulated solar irradiation, using phosphate buffer solution (PBS) or NaHCO3 as buffer solution. The optimized Bi2O3/CuO photocathode possesses rich vacancies, great photoresponse capability, and exhibits great photocatalytic activity toward CTC degradation due to its Z-scheme structure. Electron spin-resonance spectroscopy (ESR) and reactive species trapping experiments reveal that superoxide radicals/hydroxyl radicals are both the main radicals contributing to CTC degradation. Moreover, carbonate radical plays a more effective role toward CTC degradation, resulting in 40% improvement for CTC degradation in the BPES within 2 h. Higher current density (maximum of 137.6 A m-2) and more negative cathode potential are obtained from the illuminated BPES with NaHCO3 buffer. Possible mechanism and pathways of CTC degradation are proposed. This study contributes to the development of BPESs for antibiotics degradation.