Abstract:TiO₂-coated activated carbon surface (TAs) composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow (AY) was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO₂ content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO₂ particles as well as the mixture of TiO₂ powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO₂ content in TAs on the degradation rate.

Key words: photocatalysis; TiO₂-coated activated carbon; acid yellow; composite catalyst