Construction of NH₂-MIL-101(Fe) /TiO₂ Heterojunction to Enhance the Charge Transfer in Photocatalytic Degradation of Antibiotics

As an indispensable medicine, antibiotics are widely used in daily life, but following the substantial discharge of various wastewater, which result in antibiotic resistance of microbial pathogens and jeopardizes the health of ecosystems. There is an urgent need to tackle drug residues. After decades of intensive research, photocatalysis technology has been developed into an efficient technology for wastewater treatment due to its economic and environmental-friendly properties. Here, the photocatalyst NH₂-MIL-101(Fe)/TiO₂ composite was fabricated to degrade the antibiotics: tetracycline hydrochloride (TC), doxycycline hydrochloride (DC), and levofloxacin hydrochloride (LEV). The NH₂-MIL-101(Fe)/TiO₂ photocatalysts exhibited excellent visible light harvesting performance with a narrow band gap (2.19 eV), low recombination ratio of photoinduced carriers, good photoelectric response, low resistance and long charging life. NH₂-MIL-101(Fe)/TiO₂ (MT0.50 molar ratio Fe:Ti = 1:1) showed the highest degradation effect, with the degradation rates of 91.52%, 80.11%, and 88.13% for TC, DC, and LEV in 6 h, with kinetic constants of 0.00510 min⁻¹, 0.00344 min⁻¹ and 0.00503 min⁻¹, respectively. The catalysts exhibited significantly increased photocatalytic activity and excellent stability compared to NH₂-MIL-101 (Fe) and TiO₂. In addition, MT0.50 still showed good photodegradation effect under simulated different pH and ionic strength, indicating that MT0.50 has good adaptability and practical application. The study of photocatalytic mechanism showed that ·OH was the main active substance in the degradation process, which played an important role in degrading antibiotics. In addition, three possible degradation pathways for antibiotics were proposed based on the intermediates detected by LC–MS, and the photocatalysts also showed great stability and excellent antimicrobial effects. Therefore, the present study provides a new strategy and enriches the mechanisms involved in the wastewater treatment of NH₂-MIL-101(Fe)/TiO₂ photodegradation of various antibiotics.