Synergistic enhancement of TiO2 photocatalysis by tourmaline for efficient tetracycline hydrochloride degradation

Abstract

BACKGROUND

The widespread discharge of antibiotic residues, particularly tetracycline hydrochloride (TCH), into aquatic environments has created an urgent need for highly active and stable photocatalysts. In this study, a tourmaline-doped TiO₂ composite (TM-Ti) was synthesized via an in-situ sol–gel method, aiming to synergistically enhance the degradation of TCH under UV irradiation.

RESULT

Under optimized conditions (0.25 g L⁻¹ catalyst, pH 7.1, 20 mg L⁻¹ TCH), the TM-Ti catalyst achieved a TCH removal efficiency of 61% within 60 min of irradiation, substantially higher than those of pure TiO₂ (48%) and pristine tourmaline (8%). After an extended reaction time of 8 h, the total TCH removal reached approximately 90%, with adsorption accounting for 20% and photocatalysis serving as the dominant removal mechanism (70%). The material retained over 80% of its initial activity after six consecutive cycles, confirming excellent reusability. Compared with pure TiO₂, the TM-Ti composite exhibited a narrowed bandgap (from 3.18 eV to 2.92 eV), suppressed charge recombination, and an approximately 95% larger specific surface area. Mechanistic investigations identified superoxide radicals (·O₂⁻) and holes (h⁺) as the primary reactive species, supporting an ‘adsorption-enriched photocatalysis’ mechanism. Degradation pathway analysis and biotoxicity tests further confirmed the conversion of TCH into low-toxicity compounds, with partial mineralization to CO₂.

CONCLUSION

This study demonstrated that the strategic introduction of tourmaline synergistically enhanced TiO₂ photocatalysis, presenting a promising and sustainable strategy for treating antibiotic-contaminated water. © 2026 Society of Chemical Industry (SCI).