Abstract
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.
Highlights
The contamination of potable water by 1,4-dioxane, a synthetic cy clic ether, is of growing concern due to its adverse impact on human health [1,2,3]
These findings indicate that the photocatalytic degradation of 1,4-dioxane is dominated by W loading and a high-stability TiO2 anatase crystalline phase, rather than by the adsorptive surface properties of the pure or W-TiO2 photo catalysts as the dark experiments showed less than 3% of 1,4-dioxane adsorption
The mechanism based on the production of methox yacetaldehyde may be considered negligible [1,2]. This comprehensive study shows that the addition of W to TiO2 successfully increased both the anatase to rutile phase transition temperature and photocatalytic activity
Summary
The contamination of potable water by 1,4-dioxane, a synthetic cy clic ether, is of growing concern due to its adverse impact on human health [1,2,3]. TiO2, a naturally abundant semiconductor has been the centre of heterogeneous photocatalytic studies for several decades due to the material’s chemical stability, intrinsic photoactivity, low-cost and mature synthesis methods [16,17,18,19] This widely used metal oxide with a wide energy band gap The findings of this work suggest that higher W loading calcined at temperatures in excess of 500 ◦C causes enhanced TiO2 photocatalytic performance Despite these numerous studies into the effects of various W loadings on TiO2, sur prisingly few reports detail the efficiency of W-TiO2 composite photo catalysts for the degradation of 1,4-dioxane. % W-TiO2) and calcina tion temperature (500− 1000 ◦C), with the aim of identifying the opti mum transition temperature from its anatase phase (the most photocatalytic active one) to rutile to improve the processability and material functionality of the W-TiO2 composite photocatalysts. The analysis of the 1,4dioxane degradation process and mechanism is highlighted
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