Abstract: The photocatalytic degradation of dichloroacetic acid in the aqueous solution was studied using pure TiO₂ and TiO₂ supported on active carbon as photocatalysts. It was found that the photocatalytic reaction rate of TiO₂ was increased by the presence of active carbon support, but the TiO₂/AC prepared by adding active carbon during the formation of TiO₂ sol exhibited much higher photocatalytic activity than TiO₂+AC formed by mechanical mixture of TiO₂ particles and active carbon in the suspension. The apparent rate constants, KCl^- for Cl^- production were 6.72×10^-3,3.72×10^-3 and 3.45×10^-3 min^-1 for TiO₂/AC, TiO₂+AC and TiO₂ respectively. The photocatalytic activity of TiO₂/AC having various AC content was also compared. With AC mass fraction of 5%-20% the KCl^- for TiO₂/AC was obviously larger than that for TiO₂, but the result was contrary to this for higher AC mass fraction(≥30%). The present results have clearly demonstrated that because as TiO₂ was supported on active carbon, the effective surface area of the photocatalysts and their adsorbability for organic molecules can be increased, providing high concentration environments of organic molecules around TiO₂ particles and resulting to the enhancement of photocatalytic activity of TiO₂.

Key words: photocatalytic degradation, TiO₂, active carbon, Cl₂CHCOOH