Effect of carbon doping on WO3/TiO2 coupled oxide and its photocatalytic activity on diclofenac degradation

The improved photocatalyst carbon-doped WO3/TiO2 mixed oxide was synthesized in this study using the sol–gel method. The catalyst was thoroughly characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy, N2 adsorption desorption analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic efficiency of the prepared materials was evaluated with respect to the degradation of sodium diclofenac (DCF) in a batch reactor irradiated under simulated solar light. The progress of the degradation process of the drug was evaluated by high-performance liquid chromatography (HPLC), whereas mineralization was monitored by total organic carbon analysis (TOC) and ion chromatography (IC). The results of the photocatalytic evaluation indicated that the modified catalyst with tungsten and carbon (TWC) exhibited higher photocatalytic activity than TiO2 (T) and WO3/TiO2 (TW) in the degradation and mineralization of diclofenac (TWC>TW>T). Complete degradation of diclofenac occurred at 250 kJ m−2 of accumulated energy, whereas 82.4% mineralization at 400 kJ m−2 was achieved using the photocatalytic system WO3/TiO2-C. The improvement in the photocatalytic activity was attributed to the synergistic effect between carbon and WO3 incorporated into the TiO2 structure.