Enhanced visible-light-driven degradation of tetracycline via photocatalysis and photo-Fenton processes using B-TiO₂/Fe₃O₄ composites

The persistence of antibiotic pollutants in aquatic environments poses a significant threat to public health and ecosystems, driving the need for effective solar-driven water treatment technologies. This study synthesized and evaluated a series of black titanium oxide (B-TiO₂) and B-TiO₂/Fe₃O₄ composites for the visible-light-driven degradation of tetracycline, via photocatalysis and photo-Fenton processes. B-TiO₂ was prepared through NaBH4-assisted reduction, introducing Ti³⁺ species and oxygen vacancies that narrowed the bandgap and enhanced visible-light absorption. Fe₃O₄ was incorporated via co-precipitation in varying proportions (12.5–50 wt%), generating heterostructures that improved charge separation and Fenton reaction. Comprehensive characterization by Transmission Electron Microscopy, X-ray Diffraction, Ultraviolet–Visible Diffuse Reflectance Spectroscopy and X-ray Photoelectron Spectroscopy confirmed the structural, optical, and surface chemical features responsible for enhanced photocatalytic activity. Photocatalytic degradation tests revealed that the composite sample B-TiO₂ with 12.5 % of Fe₃O₄ (BT-Fe12.5) exhibited the highest activity under visible light, attributed to improved light harvesting and heterojunction-assisted charge transfer. However, under photo-Fenton conditions, performance increased with Fe₃O₄ content, the composite sample B-TiO₂ with 50 % of Fe₃O₄ (BT-Fe50) achieving the highest rate constant (k = 0.02867 min⁻¹) and shortest half-life (~24 min), due to enhanced hydroxyl radical generation. This work demonstrates the synergistic mechanism and tunability of B-TiO₂/Fe₃O₄ composites, highlighting their dual functionality and potential for cost-effective, sunlight-driven antibiotic removal from water.