Photocatalytic activity of N-TiO2/O-doped N vacancy g-C3N4 and the intermediates toxicity evaluation under tetracycline hydrochloride and Cr(VI) coexistence environment

In this study, N-TiO2/O-doped N vacancy g-C3N4 was synthesized by the solvothermal method. The optimized photocatalyst N-TiO2/CNONV-2 has excellent photocatalytic activity, and it can reach about 3 times of tetracycline hydrochloride (TC−HCl) degradation rate and 41 times of Cr(VI) reduction rate comparing with N vacancy g-C3N4. Meanwhile, N-TiO2/CNONV-2 exhibited excellent photocatalytic activity and chemical stability under TC−HCl and Cr(VI) coexistence environment. The enhancement photocatalytic activity mechanism of N-TiO2/CNONV-2 is that Z-scheme heterojunctions accelerate the separation of electrons and holes, while mainly O2– and h+ attack TC−HCl and e– reduces Cr(VI) under TC−HCl and Cr(VI) coexistence environment. The influence of environmental factors (pH, organic matter, and inorganic salt) on the photocatalytic activity of N-TiO2/CNONV-2 under TC−HCl and Cr(VI) coexistence environment was studied. Furthermore, the toxicity of the intermediates was evaluated by quantitative structure-activity relationship (QSAR) prediction. The results demonstrated that the toxicity of TC intermediates can be degraded into low level over N-TiO2/CNONV-2.