Redox abilities of rutile TiO₂ ultrafine powder in aqueous solutions

Abstract

Redox abilities of rutile TiO₂ powder with an acicular primary particle, having about a 200 m²/g BET surface area obtained by a homogeneous precipitation process in aqueous TiOCl₂ solution at 50°C for 4 hrs, were investigated using a photocatalytic reaction in aqueous 4-chlorophenol, Cu- and Pb-EDTA solutions. Its abilities were then compared with those of commercial P-25 powder, together with investigating those of anatase TiO₂ powder obtained from the aqueous TiOCl₂ solution, having a similar surface area and primary particle shape as those of the rutile powder. The powder was more effective than the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest decomposition rate and the smallest amount in the same experiments in spite of similar particle shapes and surface area. From the results, it is found that the excellent photo redox abilities of the powder is likely to be caused by the specific powder preparation method regardless of crystalline structures even when having similar particle shapes and values in the surface area. Also, many OH⁻ attached to the surface of the TiO₂ particle appeared to interfere with the adsorption of decomposing target materials to the TiO₂ surface in the solution during the photocatalytic reaction, resulting in a delay in the reaction.