Application of nanostructured mesoporous silica/ bismuth vanadate composite catalysts for the degradation of methylene blue and brilliant green

Abstract

Ultrasonication method was used in the incorporation of mesoporous silica (mSiO2) on BiVO4 nanoparticles. The average crystallite size of the BiVO4 nanoparticles was controlled at around 2.4–5.1 nm on mesoporous silica surface. The composites were systematically evaluated as photocatalysts for the degradation of methylene blue (MB) and brilliant green (BG) dyes as a function of mesoporous SiO2 content. A marked compositional dependence of the photocatalytic activity was evidenced for MB and BG degradation under visible light. Compared with the corresponding bare bismuth vanadate nano species, the mSiO2-involved nanocomposites display enhanced photocatalytic activities. The enhancement of photocatalytic activity of BiVO4 nanoparticles with mesoporous silica was attributed to the synergistic effect between mesoporous silica and BiVO4 which improved the separation of photogenerated electrons and holes. Structures and morphologies of the samples were examined by TEM, SEM, XRD, EDS, FT-IR and UV–visible spectroscopy. The effects of operational parameters like dye concentration, mSiO2 content, calcination temperature and reaction time have been analyzed. The results showed that the photocatalytic activity of mSiO2/BiVO4 nanocomposites increases with the modification of BiVO4 by changing the content from 1.0 to 15.0 wt % mesoporous SiO2, the sample of 10.0 wt. % mesoporous SiO2 loaded on BiVO4 showed the higher photocatalytic activity. As the silica in the composites has a very good contact with the BiVO4 nanoparticles it enhances the photo-electron conversion of BiVO4 by reducing the recombination of photo-generated electron–hole pairs based on the band structures of BiVO4. The catalyst is found to be reusable.

Keywords

• Photocatalysis
• Mesoporous SiO2
• BiVO4
• Visible light
• Methylene blue
• Brilliant green