High activation of apatite-coated titanium dioxide using heat treatment

The purpose of this study was to improve the photocatalytic activity of TiO 2. A composite material in which apatite crystals were precipitated on the surface of TiO 2 was synthesized by immersing TiO 2 powder in pseudo-body solution. The composite material was heated in an attempt to improve the crystallization without inducing the anatase to rutile phase transformation of TiO 2 or reducing the specific surface area. In contrast to using TiO 2 alone, apatite-coated TiO 2 had a higher anatase-to-rutile transition temperature and lower specific surface area. In the methylene blue decolorization test, the decolorization rate of apatite-coated TiO 2 gradually increased with an increase in the heating temperature from 100 °C to 500 °C, and rapidly increased from 700 °C to 900 °C. The apatite-coated TiO 2 heated at 800 °C had the highest decolorization speed, which was approximately three times faster than that of apatite-coated TiO 2 without heating. It is assumed that the crystallinity of the anatase part is enhanced by heating, and the photocatalytic activity is improved.