Ternary TiO₂ Nanocomposite for Enhanced Photocatalytic Degradation of Metronidazole in Pharmaceutical Wastewater

Pharmaceutical residues in aquatic environments pose significant environmental and public health risks due to their persistence and contribution to antimicrobial resistance. In this work, a ternary TiO₂/ZnO/SnO₂ nanocomposite was synthesized via a facile and scalable two-step co-precipitation method using commercially available P25 TiO₂ nanoparticles. The structural, morphological, and surface properties of the synthesized nanocomposite were characterized using XRD, SEM, TEM, and XPS analyses, confirming the successful formation of a well-integrated heterojunction. The photocatalytic performance of the TiO₂/ZnO/SnO₂ nanocomposite was evaluated for the degradation of metronidazole (MNZ) under UV irradiation. The effects of operational parameters including catalyst dosage, initial MNZ concentration, solution pH, and irradiation time were systematically investigated. Under optimized conditions (MNZ concentration 20 µg/mL, catalyst loading 0.5 mg/mL, pH 7.0, irradiation time 120 min), the nanocomposite achieved up to 90% degradation efficiency, outperforming commercial TiO₂ nanoparticles under identical conditions. Application to real pharmaceutical wastewater resulted in 76% MNZ removal, demonstrating the practical applicability of the developed system. The enhanced photocatalytic performance is attributed to improved charge separation within the ternary heterojunction, reducing electron–hole recombination. The use of commercially available TiO₂ and a simple synthesis route highlights the potential of this approach for cost-effective and scalable pharmaceutical wastewater treatment.