Photocatalytic titanium dioxide was synthesized by an acid-catalyzed sol-gel process with titanium n-butoxide as the precursor. Several factors including adsorption, wavelength, aniline concentration, and pH were examined to measure their impact on the photocatalytic activity of synthetic TiO2, using aniline as the target compound under visible light irradiation by light-emitting diodes. Under blue-light illumination, the as-synthesized TiO2 exhibited photocatalytic activity of whereas commercial TiO2 (Degussa P-25) displayed no photoreaction under the same conditions. This photoactivity was more pronounced under blue, green, yellow, and red light, and that corresponded very well with the adsorption spectrum of as-synthesized TiO2. As the initial aniline concentration increased from 0.047 to 0.80 mM, the degradation efficiency of aniline decreased from 72% to 18% after irradiation for 4 h with 1 g/L TiO2. The reaction followed the Langmuir-Hinshelwood kinetic model with the adsorption equilibrium and rate constant having values of 15.89 1/mM and 9.96 x 10(-4)/(mM min), respectively. For the photocatalysis of aniline by this visible-light-activated TiO2, the optimum pH was 7 in the range 4-10. (C) 2011 Elsevier B.V. All rights reserved.