Stable and rapid degradation of tetracycline using a photoelectrochemical system comprising a Ag/N–TiO2 photoanode and P–Pd cathode

Herein, a highly stable and efficient photoelectrocatalytic system was developed for the rapid degradation of tetracycline. The photoelectrocatalytic system comprised two Ag/N-doped TiO2 nanotube photoanodes, a bipolar membrane, and a P–Pd cathode. The Ag/N-doped TiO2 nanotube photoanodes were coupled with a P–Pd cathode to enhance the hydroxyl free radical (·OH) generation at the cathode surface. The bipolar membrane can separate tetracycline pollutants and degradation products from the photoanodes, which can minimize the contamination of the photocatalyst by tetracycline or products, thereby enhancing the repeatability and stability of the photoelectrocatalytic system. photoelectrocatalytic uses ultraviolet–visible light as the input energy for the effective removal of tetracycline and total organic carbon. The initial pH in the cathode and photoanode chambers was 7.0. The Na2SO4 concentration in the photoanode chamber and the addition amount of H2O2 were 0.2 M and 4% (v/v), respectively. Under these conditions, 100 mL of 100 mg/L tetracycline was completely degraded within 60 min, and 82.3% total organic carbon was removed within 5 h. The pseudo-first-order reaction rate constant of the Ag/N-doped TiO2 nanotube with 0.15 M Ag was 0.0637 min-1, which was 12 times higher than that of N-doped TiO2 nanotube. The mechanisms underlying·OH generation and the tetracycline degradation pathway were also elucidated. The photoelectrocatalytic system, which is an eco-friendly and low-energy system, exhibits excellent stability and reliability toward tetracycline and total organic carbon degradation and significantly aids the development of wastewater remediation.