Photocatalytic Degradation of Tetracyclin Using Chlorine-Doped BiOBr

The Cl-doped BiOBr photocatalysts were used to degrade tetracyclin, which was usually difficult to degrade in wastewater, to reduce secondary pollution to the environment. In this paper, Cl-doped BiOBr composites were prepared by a hydrothermal method using bismuth nitrate as the bismuth source, potassium bromide as the bromine source, potassium chloride as the chlorine source, and deionized water as the solvent. The physical structure, chemical composition, surface morphology, optical properties, and charge transport of the Cl-doped BiOBr composites were characterized and analyzed by XRD, XPS, TEM, UV–vis DRS, photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and Brunauer–Emmett–Teller (BET). The successful preparation of BiOBr and Cl-doped BiOBr with a tetragonal crystal system was confirmed by XRD characterization. SEM and TEM images confirmed that the samples have a lamellar stacking structure. PL, photocurrent, and EIS studies on the samples showed that the Cl-doped BiOBr composites had good charge separation efficiency. The catalytic performance of the Cl-doped BiOBr composites was investigated using tetracyclin (TC) as the target contaminant, and the results showed that the C₂─BiOBr composites exhibited a strong photodegradation of TC, with a degradation efficiency of 76.2%. The excellent performance of the Cl-doped BiOBr was attributed to the formation of doped energy levels with improved visible light absorption and efficient charge transfer/separation. Free radical scavenger studies showed that ∙OH and h⁺ generated by the photocatalyst were responsible for the efficient degradation of TC. Two possible degradation pathways of TC were proposed based on HPLC-MS/MS detection and their intermediate products tended to be less toxic. Finally, the good stability and reproducibility of the catalyst were confirmed by degradation cycling experiments. This study provides a reference for photocatalysts in practical applications.