Effects of WO3 Amount and Treatment Temperature on TiO2-ZrO2-WO3 Photocatalysts Used in the Solar Photocatalytic Oxidation of Sildenafil

TiO2 shows improved photocatalytic properties when combined with other oxides, such as ZrO2. Unfortunately, this material does not exhibit a spectral response in the visible range, but this can be improved by adding WO3. Here, the effect of the amount of WO3 and the treatment temperature on TiO2-ZrO2-WO3 materials applied in the solar photocatalytic oxidation of sildenafil was evaluated. The materials were synthesized using the sol–gel method and were characterized by N2, XRD, UV-Vis RDS, SEM, PL, and XPS. Photocatalytic activity was determined by the degradation and mineralization of sildenafil. The most active photocatalysts were selected for stability testing and to determine the oxidizing species that dominate the reaction mechanism. The optimal amount of WO3 that improves solar photocatalytic activity at both treatment temperatures was found to be 1% with a reaction mechanism based on OH· and h+. WO3 reduces electron–hole pair recombination. At 500 °C, the crystallinity of the anatase phase is improved, while at 800 °C, the transformation to rutile is suppressed at low WO3 concentrations. XPS observed the reduction in Ti4+ to Ti3+ and W6+ to W5+ in TiO2–ZrO2–WO3 materials, which were found to be photoactive under sunlight with potential for use in industrial-scale reaction systems.