Photocatalytic degradation of methyl orange in a sparged tube reactor with TiO2-coated activated carbon composites

The photocatalytic oxidation of methyl orange has been performed in the presence of suspended TiO2-coated activated carbon (TiO2/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 TiO2/AC has a higher decomposition efficiency than pure TiO2 particles, as well as a mixture of TiO2 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 TiO2/AC, which is considered to be responsible for the decrease in TiO2/AC photoactivity after 20 trials.