Photocatalytic Degradation of Tetracycline Hydrochloride by Mn/g-C[sub.3]N[sub.4]/BiPO[sub.4] and Ti/g-C[sub.3]N[sub.4]/BiPO[sub.4] Composites: Reactivity and Mechanism

The environmental pollution caused by antibiotics is becoming more serious. In this study, the Mn/BiPO[sub.4]/g-C[sub.3]N[sub.4] composite (Mn-BPC) and the Ti/g-C[sub.3]N[sub.4]/BiPO[sub.4] composite (Ti-BPC) were prepared by hydrothermal reaction method and solvent method, respectively, and applied to the degradation of tetracycline (TC) in an aqueous environment. The XRD and HRTEM results showed that these materials had the crystalline rod-like structure of BiPO[sub.4] and abundant carbon, nitrogen and carbon–oxygen surface functional groups. The degradation of TC by Ti-BPC and Mn-BPC were nearly 92% and 79%, respectively. The degradation processes of TC were well consistent with the pseudo-second-order kinetics model and R[sup.2] values were closer to 1. The trapping experiment showed that electron holes (h[sup.+]) were the main reactive species for the degradation of tetracycline, OH· and O[sub.2] [sup.−] also have certain effects. Also, the possible photocatalytic degradation mechanism of Ti-BPC and Mn-BPC composites was thereby proposed. TC was firstly adsorbed on the surface of catalysts, and subsequently degraded by reactive species such as h[sup.+], OH· and O[sub.2] [sup.−] generated under visible light excitation. This study shows that the Ti-BPC and Mn-BPC photocatalysts have great potential in antibiotic degradation and can provide new ideas for antibiotic removal in aqueous environments.