Microstructure and photocatalytic property of SiO₂-TiO ₂ under various process condition

Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol-gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO₂-TiO₂ prepared by sol-gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO₂ grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol-gel derived SiO ₂-TiO₂ powder prepared at 750°C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO ₂-TiO₂ samples prepared by hydrothermal processing at 250°C showed a slightly lower decomposition rate than P25.