LAUSR

With growing environmental concerns, the removal of toxic industrial dyes from wastewater has become a critical global issue. In this study, TiO2–CuSe composites were synthesized using a cost-effective and simple chemical method to determine the optimal concentration of CuSe for the efficient degradation of methylene blue (MB) under visible light. The TiO2 samples exhibited a mix of rutile and anatase phases, while CuSe formed in a hexagonal phase. Both TiO2 and CuSe were observed to have agglomerated particles with indistinct boundaries. The optical bandgap shifted towards the visible region from 3.25 eV (pure TiO2) to 2.91 eV with increasing the amount of CuSe in the composites. The photocatalytic activity of TiO2, CuSe, and TiO2–CuSe composites was evaluated by monitoring MB degradation, with the composites outperforming the individual components under visible light. Notably, the TiO2–20% CuSe composite (AK-4) demonstrated superior efficiency, removing 98% of MB in just 70 minutes. The photocatalysts also exhibited enhanced antibacterial properties, effectively reducing E. coli colonies from 1.71 × 1012 CFU mL−1 (pure TiO2) to 1 × 1010 CFU mL−1 for the AK-4 composite. This study suggests that visible light-activated TiO2–CuSe composites could be effective for both water purification and bacterial infection control.