Composite catalysts made of nanocrystalline TiO2 and carbon were prepared by a modified sol-gel method over activated carbon (AC). The composite catalysts were characterized by N-2 adsorption-desorption isotherm, TG, diffuse reflectance UV-vis spectroscopy, XRD and SEM. The photocatalytic activity was tested on the degradation of Chromotrope 2R (M) in aqueous medium under UV radiation. The composite catalysts exhibited higher activities than commercial Degussa P25 alone and the photocatalytic process was more efficient than the pure photolytic degradation. A modified Langmuir-Hinshelwood approach was used to study the kinetics and to determine the adsorption equilibrium constant and the reaction rate constant. Two different mechanisms are proposed and discussed in order to explain the observed synergy. (c) 2006 Published by Elsevier B.V.