Photocatalytic Degradation of Tetracycline and Copper Complex by Bi2MoO6/Bi2S3 Heterojunction

Abstract

Bi2MoO6/Bi2S3 heterojunctions were synthesized by the solvothermal method. The morphology, chemical composition, and photoelectric properties of the heterojunction materials were characterized by XRD, TEM, UV-Vis, XPS, and I-T. Tetracycline (TC) and tetracycline-copper (TC-Cu) composites were degraded by the as-prepared heterojunctions under visible light. The effects of pH, initial concentration of TC, and molar ratio of TC to Cu2+ on the degradation deficiency of TC were investigated. Additionally, the main active radicals, intermediates, and mechanisms were ascertained by in situ capture experiments and the identification of intermediates. The toxicities of TC and TC-Cu before and after degradation were evaluated by chlorella growth inhibition experiments. The results showed that the prepared Bi2MoO6/Bi2S3 heterojunction was a uniform nanosheet and its band gap was 1.76 eV. Bi2MoO6 and Bi2S3 with a mass ratio of 3:1 (MS-0.3) exhibited a composite ratio of TC and Cu2+ was 2:1 and had the best photocatalytic performance. When the concentration of TC was 10 mg·L-1 with neutral solutions, after reacting for 60 min, the degradation rate of TC and mineralization rate of the solution for TC-Cu were 85.63% and 52.94%, respectively. The results of active group capture experiments showed that the main active group of the heterojunction was the·O2- radical in visible light. In addition, the results of growth inhibition experiments showed that the presence of Cu2+ reduces the toxicity of TC photocatalytic degradation products in the TC-Cu complex, and the antibiotics can be effectively removed in the TC-Cu complex by photocatalytic oxidation.