A series of polyaniline/TiO2 (PANI/TiO2) Composites has been prepared from aniline and TiO2 under various polymerization conditions. Among these conditions are the concentrations of aniline, ammonium persulfate, HCl, sodium dodecyl sulfate, and the amount of TiO2, More composites were obtained by replacing HCl with H2SO4, H3PO4, and HNO3 as dopant acids. Scanning electron microscopy, UV/vis-diffuse reflectance spectroscopy, FTIR and TGA were used to characterize some of these composites. The rate of degradation of dyes with these composites followed first-order kinetics in the dye concentration. The activity of the composite towards the degradation process differs according to the experimental polymerization conditions. The activity increased with the increase in the concentration of aniline monomer and persulfate, but decreased with increasing the concentration of HCl, sodium dodecyl sulfate, and the amount of TiO2. The activity of composites formed in the presence of different acids followed the order H2SO4 > H3PO4 > HCl > HNO3. The rate of composite/dye interaction was enhanced with the UV-irradiation, increasing load of composite, and temperature. It was retarded with the increase in initial dye concentration and pH. The activation parameters were determined and a plausible mechanism was proposed. (C) 2009 Elsevier B.V. All rights reserved.