Removal of acetaminophen from water by simulated solar light photodegradation with ZnO and TiO₂ nanoparticles: Catalytic efficiency assessment for future prospects

This study aims to comparatively assess TiO₂ and ZnO catalysts in photodegradation of aqueous acetaminophen solution. Commercial TiO₂ (anatase and rutile phases), synthetic TiO₂ (rutile) commercial ZnO (wurtzite), and synthetic ZnO (wurtzite) are all described; the synthetic ZnO and TiO₂ were synthesized by thermal precipitation method. XRD, SEM, UVvis spectroscopy, and BET/BJH were used for catalysts characterization. The photocatalytic experiments have been carried out using solar simulated radiation (0.0146 W/cm2). A 50 mL solution of an appropriate acetaminophen concentration was studied. The ZnO systems showed higher catalytic efficiency than the TiO₂ counterparts. Among the TiO₂ systems, the commercial anatase showed highest activity, followed by the synthetic system (rutile). Among the ZnO systems, the synthetic catalyst shows higher efficiency than the commercial counterpart. Based on its superior efficiency, the synthetic ZnO has been singled out for further investigation to find optimal working conditions. The pH plays a main role in photdegradation process, the synthetic ZnO photodegraded ∼97 % of acetaminophen at pH = 9 in 1 h of irradiation. The acetaminophen photodegradation in basic to neutral condition is better than acidic solutions. The synthetic ZnO particles completely mineralized acetaminophen within 120 min at pH = 7. This is confirmed by electronic absorption spectrophotometry, high-performance liquid chromatography and total organic carbon measurements. The photodegradation rate was increased with increasing the amount of loaded ZnO up to a steady-state limit of 0.1 g. Effects of different reaction parameters, on synthetic ZnO catalyst efficiency in acetaminophen photodegradation, are studied to find out the optimal conditions.