抄録
Crystalline titania particles were prepared by hydrothermal treatment of aqueous solutions of inoganic salts. Rutile and anatase particles were obtained from chlorides (TiCl_3, TiCl_4,) and oxysulfate (TiOSO_4), respectively. Rutile particles were composed of needle-like particles and higher specific surface area (SSA) of 120m^2/g, while anatase have lower SSA of 30m^2/g. There were not a particular effect of ultrasound upon the hydrolysis reaction so far. On the other hand, iron oxide particles of 〜10nm can be prepared by oxidizing a diluted suspension of Fe(OH)_2 in alkaline solution when a suitable sonication is provided. This novel method was applied to surface modification of titanium dioxide. Transmission electron microscopy showed a successful deposition of iron oxide nanoparticle onto titania. Bleaching of methylene blue (MB) was tested for the titanialiron oxide composite particles and other reference materials. It was found that the composite particles have a dractic bleaching effect in the absence of neither UV nor visible light. This is due not to photocatalysis but to anormal absorption of MB to the composite particles. The MB bleaching of anatase-based composite was found to be higher than that of rutile-based one in spite of lower SSA. It is inferred that strong acidic points were produced around the chemical bonds of Ti-O-Fe.
