Construction of FeOOH/Bi₂SiO₅ Heterojunction for Photocatalytic Degradation of Tetracycline in Biomedical Wastewater

The recalcitrant nature of tetracycline (TC), a widely used broad-spectrum antibiotic in biomedicine, poses severe ecological and human health risks due to its persistence in aquatic environments. Here, we report a novel FeOOH/Bi₂SiO₅ heterojunction photocatalyst synthesized via a facile hydrothermal and precipitation method, featuring uniformly deposited amorphous FeOOH quantum dots (QDs) on Bi₂SiO₅ nanosheets. Structural and photoelectrochemical analyses reveal that FeOOH QDs act as efficient hole-trapping co-catalysts, narrowing the bandgap of Bi₂SiO₅ to 2.56 eV and enhancing visible-light absorption. This synergy results in a 3.9-fold higher charge separation efficiency compared to pristine Bi₂SiO₅, as confirmed by transient photocurrent and electrochemical impedance spectroscopy. Under optimized conditions (10 wt% FeOOH loading), the composite achieves 88% TC degradation within 100 min under simulated solar irradiation. Radical trapping experiments and EPR spectroscopy identify superoxide radicals (•O₂⁻) as the dominant reactive species. The catalyst demonstrates robust performance in diverse water matrices (river, lake, and biomedical wastewater) and retains >80% efficiency over four cycles. Furthermore, liquid chromatography-mass spectrometry (LC‑MS) was employed to identify the intermediate products of tetracycline degradation, allowing us to propose a possible degradation pathway. Meanwhile, the underlying photocatalytic mechanism was elucidated using electron paramagnetic resonance (EPR) and radical trapping experiments. This study provides mechanistic insights into the role of FeOOH/Bi₂SiO₅ heterojunctions in antibiotic degradation, offering a promising strategy for designing efficient, stable photocatalysts to address biomedical wastewater contamination. FeOOH/Bi₂SiO₅ photocatalyst enables efficient charge separation and 88% tetracycline degradation in 100 min with •O₂⁻ as main active species.