Photocatalytic degradation of methyl orange in a sparged tube reactor with TiO 2-coated activated carbon composites

Abstract

The photocatalytic oxidation of methyl orange has been performed in the presence of suspended TiO 2-coated activated carbon (TiO 2/AC) prepared by a properly controlled sol–gel method in an air sparged tube reactor. The key factors affecting the methyl orange oxidation efficiency were investigated, including the initial concentration of methyl orange, the pH value and the electric power of UV lamp. For photodegradation of methyl orange, it was observed that TiO 2/AC has a higher decomposition efficiency than pure TiO 2 particles, as well as a mixture of TiO 2 powder with activated carbon. The optimal conditions were a concentration of 12 × 10 −3 mol/l at pH 6 with 40 W of illumination for the fastest rate of methyl orange photodegradation. Diffuse reflectance UV–Vis analysis showed a shift in the threshold absorption value and a corresponding increase in bandgap energy for TiO 2/AC, which is considered to be responsible for the decrease in TiO 2/AC photoactivity after 20 trials.