Environ. Sci. Technol. 2003, 37, 153-157
Design of a Photocatalyst for Bromate Decomposition: Surface Modification of TiO2 by Pseudo-boehmite H I R O S H I N O G U C H I , * ,†,‡ AKIRA NAKAJIMA,† TOSHIYA WATANABE,† AND K A Z U H I T O H A S H I M O T O †,§ Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8904, Japan, R&D Center, Meidensha Corporation, 2-1-17, Ohsaki, Shinagawa-ku, Tokyo 141-8565, Japan, and Kanagawa Academy of Science and Technology, 32-1, Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan
The rate of BrO3- reduction by a commercial TiO2 photocatalyst under UV illumination in an aqueous solution was increased by lowering the pH from 7 to 5. The effect is attributable to an enhancement of the electrical interaction between BrO3- and the positively charged surfaces of the TiO2 photocatalyst. The surface charge can be controlled by a surface modification of the TiO2 photocatalyst without controlling the pH of the water. In fact, the isoelectric point of surface-modified TiO2 was higher than that of the unloaded TiO2 photocatalyst, resulting in an increase in the rate of the photocatalytic reduction of BrO3at a neutral pH. This increase is explained by an increase in the amount of adsorbed BrO3- on the photocatalyst surface.
Introduction Ozonation is gradually becoming a common method for the treatment of drinking water since it provides various benefits, such as the inactivation of microbial contaminants, the oxidation of taste and odor compounds, and the reduction of chlorinated byproducts. However, it is known that the bromate ion (BrO3-), which is a possible carcinogen to humans, is produced during the ozonation of water containing bromide ions (1). The World Health Organization (WHO) has proposed a maximum level for BrO3- of 25 µg/L, and in the United States and the EU, the maximum acceptable contaminant level of BrO3- is 10 µg/L. It has been reported that BrO3- is generated in the range of
