Design of Continuous Fixed Plate Photo-Fenton Reactor Based on Fe₃O₄/TiO₂@Al₂SiO₅ Fiber Board Photocatalyst and Application in Tetracycline Hydrochloride Degradation

To address the limitations of traditional photo-Fenton reactions in antibiotic wastewater treatment, this study designed a continuous flat-plate photo-Fenton reactor based on the Fe₃O₄/TiO₂@Al₂SiO₅ fiberboard photocatalyst and applied it to the degradation of tetracycline HCl (TCH). The supported catalyst Fe₃O₄/TiO₂@Al₂SiO₅ was prepared via a calcination method, using the Al₂SiO₅ fiberboard as the carrier. This not only effectively addresses the issue of catalyst recovery but also enhances the dispersion and stability of the Fe₃O₄/TiO₂ catalyst as a support. Moreover, the catalyst mainly exhibited an amorphous structure. TiO₂ and Fe₃O₄ were successfully loaded onto the surface of the carrier. The operating parameters of the reactor were systematically optimized, and the optimal conditions were determined as follows: TCH influent concentration of 50 mg/L, hydraulic retention time (HRT) of 120 min, initial pH of 4.5, H₂O₂ dosage of 10 mmol/L, and ultraviolet (UV) light intensity of 2.36 kW/m³. Under these conditions, the TCH removal efficiency could reach over 90%. Active species trapping experiments indicated that hydroxyl radicals (•OH) were the main active substances responsible for TCH degradation. With the assistance of HPLC-MS/MS and GC-MS analyses, 19 types of degradation intermediates were identified. It was proposed that the TCH degradation pathway mainly included •OH-mediated hydroxylation addition reactions and demethylation reactions initiated by •OH and h⁺. The toxicity assessment showed that the toxicity of the degradation intermediates gradually decreased with the progress of the reaction. This reactor features high efficiency, stability, and easy operation, providing a feasible solution for the large-scale treatment of antibiotic wastewater.