Photocatalytic treatment of the emerging narcotic contaminant codeine in water using a synergistic WO₃–TiO₂ catalyst

Photocatalytic degradation, an enhanced oxidation technique, has been reported for treating water containing pharmaceutical medicines. In this study, a pioneering method employing ultrasonic-assisted hydrothermal synthesis was used to produce a Tungsten Trioxide (WO₃)-Titanium Dioxide (TiO₂) nanocomposite. Various analyses, including FE-EDX/SEM, HRTEM, BET surface area analysis, XRD, UV-DRS, and XPS, were conducted to investigate the structural and optical properties of the synthesized material. The estimated TiO₂ band gap reduced from 3.0 to 2.62 eV. The mixed phases of TiO₂ nanocomposites improved photocatalytic efficiency. The impact of oxidant function, pH, and catalyst dose on the photocatalytic degradation of codeine was investigated. Maximum degradation of 95.70 ± 2.01% in 50 ppm codeine under UV light was observed at a catalyst dose of pH 9.5, 0.4 g/L, and an H₂O₂ dose of 1 mm. With oxygen purging at 100 ml/L, 98.21 ± 0.32% degradation was achieved in 30 min, compared to 72.3 ± 2.68% under ambient conditions. The rate constant increased threefold when oxygen gas was purged into the reaction mixture. The stability and reusability of the recycled nanocomposite remained high even after four consecutive cycles. The role of oxidants and the application of WO₃–TiO₂ nanocomposite for codeine degradation have not been previously assessed. The results provide a novel synthetic route for fabricating a stable, highly efficient, and reusable narrow-bandgap photocatalyst.