Photocatalytic Degradation of Tetracycline by La-Fe Co-Doped SrTiO₃/TiO₂ Composites: Performance and Mechanism Study

Human health, as well as the ecosystem’s natural equilibrium, may be jeopardized by the discharge of tetracycline into the aquatic environment. In order to effectively photocatalyzed the degradation of tetracycline in aqueous solution under visible light, this study used a two-step hydrothermal approach to produce composites of SrTiO3/TiO2 doped with two metal elements, lanthanum (La) and iron (Fe). The crystal structure, morphology, electronic structure, particle size, specific surface area and photocatalytic properties of the catalysts were assessed using a variety of methods, such as fluorescence spectroscopy, UV-Vis diffuse reflectance, X-ray diffraction, scanning electron microscopy, BET and particle size analysis. After 120 min of exposure to visible light, the co-doped catalyst showed a degradation rate of 99.1%, which was nine times greater than that of SrTiO3/TiO2 at catalyst dosing of 1.6 g/L and tetracycline concentration of 20 mg/L. The synthesized photocatalyst exhibited good tolerance to changes in pH, with the degradation efficiency of tetracycline remaining stable within the pH range of 4–10. The La-Sr (Ti-Fe) O3/TiO2 catalyst also demonstrated excellent photostability after recycling. The mechanism of tetracycline degradation is primarily attributed to the active oxidation by photogenerated holes and •O2−. Furthermore, tetracycline degradation pathways were analyzed via HPLC-MS to identify intermediates.