Enhanced photocatalytic degradation of acetaminophen from wastewater using WO₃/TiO₂/SiO₂ composite under UV–VIS irradiation

This study investigates the photocatalytic degradation of acetaminophen (Ace) from synthetic wastewater by individual TiO₂, TiO₂/SiO₂ and/or WO₃/TiO₂/SiO₂ composite under UV–VIS illumination. To characterize changes in their morphology and crystal structures before and after treatment, Χ-ray diffraction (ΧRD), Fourier transform infrared spectroscopy (FTIR), DRS UV–VIS absorption spectra, Brunaer-Emmer-Teller (BET) and scanning electron microscopy (SEM) techniques were used. The effects of varying loading ratios of the WO₃ on the TiO₂/SiO₂ composite for Ace degradation were studied. Operating parameters such as initial concentration, reaction time, dose of photocatalyst and pH were tested. Degradation by-products were also presented. It is found that the photodegradation performance of the WO₃/TiO₂/SiO₂ composite as a photocatalyst in this study could be enhanced by optimizing the loading ratio of the WO₃. About 3% (w/w) of WO₃/TiO₂/SiO₂ was found to improve the degradation of Ace from 33% to 95% at the same initial concentration of 5 mg/L. The resulting oxidation by-products included hydroquinone and 1,4-benzoquinone. Under the same conditions, the result of photocatalytic degradation by the 3% (w/w) of WO₃/TiO₂/SiO₂ composite was significantly higher (95%) than that by the individual TiO₂/SiO₂ (42%) and/or by the TiO₂ alone (33%). Under optimized conditions (1.5 g/L; 3% (w/w) of WO₃/TiO₂/SiO₂ composite; pH 9; 4 h of reaction time), 95% of Ace removal with an initial concentration of 5 mg/L could be attained. However, the treated effluents still could not meet the discharge standard of < 0.2 mg/L set by China's and US legislation. This indicates that further subsequent treatment like biological processes is still necessary for completing the removal of target pollutant from the wastewater samples.