Photoredox properties of ultrafine rutile TiO2 acicular powder in aqueous 4-chlorophenol, Cu-EDTA and Pb-EDTA solutions

The redox properties of a homogeneously precipitated TiO2 rutile powder with a BET surface area of similar to200 m(2)/g, consisting of acicular primary particles, were characterized using a photocatalytic reaction in aqueous 4-chlorophenol, Cu-EDTA and Pb-EDTA solutions under ultraviolet irradiation. Results were compared to those of commercial P25 TiO2 powder with spherical primary particles as well as those of home-made anatase TiO2 powder with similar to200 m(2)/g BET surface area. Here, the anatase powder also includes mainly the primary particles very similar to the acicular shapes of the rutile TiO2 powder. The rutile powder showed the fastest decomposition rate and the largest amount of product in the photoredox, compared with the anatase or P25 powder, while the anatase powder unexpectedly showed the slowest rate and the smallest amount in the same experiments regardless of having almost the same surface area. The excellent photoredox abilities of this rutile powder appear to be due to a specific powder preparation method, for example, a homogeneous precipitation leading to direct crystallization from the solution, regardless of their crystalline structures, even when the powders have the similar particle shape and surface area. (C) 2002 Elsevier Science B.V. All rights reserved.