Oxidation of aniline by titanium dioxide activated with visible light

Abstract 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 TiO 2 , using aniline as the target compound under visible light irradiation by light-emitting diodes. Under blue-light illumination, the as-synthesized TiO 2 exhibited photocatalytic activity of whereas commercial TiO 2 (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 TiO 2 . 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 TiO 2 . 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 × 10 −4 /(mM min), respectively. For the photocatalysis of aniline by this visible-light-activated TiO 2 , the optimum pH was 7 in the range 4–10.