Enhanced tetracycline degradation and power generation in a solar-illuminated bio-photoelectrochemical system

In this study, a bio-photoelectrochemical system (BPES) is constructed by coupling a reduced graphene oxide/TiO2/Ag (RGO/TiO2/Ag) photocathode with a bioanode. The BPES integrated advantages of both photocatalyis process and bioelectrochemial system, and high efficiency of tetracycline (TC) degradation and simultaneous electricity generation were achieved. Under the conditions of 10 mg L−1 TC and 200 Ω external resistance, 95.21% of TC in wastewater can be removed within 8 h. The BPES with the RGO/TiO2/Ag photocathode shows higher columbic efficiency (CE) and mineralized current efficiency (MCE) than the system with a pristine TiO2, RGO/TiO2 or TiO2/Ag photocathode. The maximum power density is 133 mW m−2 under light illumination and 101 mW m−2 in the dark. The radical trapping experiments and fluorescence spectra analysis indicate superoxy group (·O2−) is the primary active oxidant. In addition, the underlying mechanism for the boosted TC degradation in the BPES are proposed. Our results suggest that BPES can be served as an efficient approach for the remediation of antibiotic-contaminated wastewater.