Solar light assisted photocatalytic degradation of 1,4-dioxane using high temperature stable anatase W-TiO₂ nanocomposites

This work outlines a systematic and detailed study of the modification of anatase TiO₂ with tungsten (W). The impact this coupling has on the temperature of the anatase to rutile phase transition and the photocatalytic degradation of 1,4-dioxane, a highly toxic compound that is increasingly present in water bodies is also studied. TiO₂ composite photocatalysts with 2, 4, 8 and 16 mol. % W, respectively, were produced using a sol-gel process and then calcined between 500−1000 °C. The crystallinity and phase composition of pure and W-TiO₂ photocatalysts were examined using X-ray Diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All W-TiO₂ composite photocatalysts demonstrated 100 % anatase crystalline phase at calcination temperatures as high as 800 °C. Due to the retention of 26 % anatase after calcination at 950 °C, 8 mol. % W was established as the optimum W loading for the development of high temperature stable anatase W-TiO₂ composite photocatalysts. The % anatase content also significantly impacts the photocatalytic activity of the W-TiO₂ composite photocatalysts. In the presence of solar light, 100 % of 1,4-dioxane was successfully degraded by 2-W-TiO₂, 4-W-TiO₂ and 8-W-TiO₂ composite photocatalysts, respectively, calcined at 800 °C. However, as the calcination temperature increases and the % anatase content decreases, only 70 % of 1,4-dioxane was degraded when using 4-W-TiO₂ and 8-W-TiO₂ calcined at 900 °C. The highest % removal of 1,4-dioxane was also achieved using 8-W-TiO₂ calcined at both 800 and 900 °C. 8-W-TiO₂ is therefore considered the optimum sample for both photocatalysis and phase transition temperature.