A Comparative Study on the Photocatalytic Efficiency of ZnO, TiO ₂ Nanoparticles and ZnO-TiO ₂ Nanocomposites in Degrading Pharmaceutical Pollutants.

Pharmaceutical drugs are now well established as persistent pollutants in aquatic ecosystems with ecological and human health hazards even at trace levels. Current treatments like biodegradation, adsorption and membrane filtration exhibit poor performance and high expense. Here, this approach provides a sustainable and efficient alternative by employing nanoparticle-based photocatalysts for degrading pharmaceuticals. Photocatalytic activities of ZnO and TiO ₂ nanoparticles (NPs) purchased commercially, and the ZnO-TiO ₂ nanocomposite prepared using the chemical precipitation method, were tested for their effectiveness against some chosen pharmaceutical contaminants like oxazolidinone antibiotics (Linezolid), Non-steroidal anti-inflammatory drug (NSAID) (Aspirin), and Paracetamol (Crocin). The prepared composite was studied to determine its structural and morphological characteristics. Experiments were performed under different pH, temperature, reaction time and agitation conditions for achieving optimal degradation efficiency. Reactive oxygen species (ROS) produced during the photocatalytic reaction were confirmed as major agents responsible for the oxidative degradation of the compounds. The process was found to perform best at pH 5, 30°C and 60°C (for Visible light and UV respectively) and 120 RPM and reached up to 75 - 80% degradation in 90 minutes. UV light markedly enhanced photocatalytic performance, particularly for Aspirin and Linezolid, with maximum degradation reaching 84.09% for Aspirin (ZnO) and 81.99% for Linezolid (TiO₂) under optimized conditions. Successful degradation was further validated by FTIR analysis of treated and untreated sample. All three nanomaterials exhibited good photocatalytic activity, with varying effectiveness depending on the compound and experimental conditions. ZnO was superior in some instances: TiO ₂ or the ZnO-TiO ₂ composite was superior in others. The results indicate compound-specific optimization. Nanoparticle based photocatalysis offers a green, adaptable approach to degrade pharmaceuticals.