Static and continuous flow photoelectrocatalytic treatment of antibiotic wastewater over mesh of TiO2 nanotubes implanted with g-C3N4 nanosheets

Photoelectrocatalytic (PEC) especially continuous flow PEC process for organic wastewater treatment greatly depends on both catalytic capacity and practical availability of electrode materials. In this study, g-C3N4 nanosheets are implanted into TiO2 nanotube arrays mesh (TCNs) through direct calcination of TiO2 nanotube array mesh loading melamine precursor. The TCNs photoelectrodes exhibit excellent PEC activity in organic pollutant degradation. Typically, almost 100% of tetracycline (TC, an emerging refractory antibiotic pollutant) is removed in 2 h and TOC removal reaches to 93% in 3 h under simulated solar irradiation at 1 V vs. Ag/AgCl. Theoretical calculations are performed to predict the primary reactive sites for radical species attack and the intermediates are identified. Meanwhile, the ecotoxicity of TC-containing wastewater greatly decrease after PEC treatment. Impressively, because of the mesh screen effect and high catalytic capacity of the photoelectrode, continuous flow PEC process keeps 80% removal efficiency of TC in real wastewater in the absence of additional background electrolyte. After prolonging 20 h, the level of treatment is highly stable. This work would set an example for potential large-scale treatment of organic wastewater using PEC process.