Photocatalytic degradation of methylene blue in a sparged tube reactor with TiO2 fibers prepared by a properly two-step method

The photocatalytic oxidation of methylene blue has been performed in the presence of suspended TiO2 fibers prepared by a properly two-step method in an air-sparged tube reactor. The key factors affecting the methylene blue oxidation efficiency were investigated, including the initial concentration of methylene blue, the pH value and the electric power of UV lamp. For photodegradation of methylene blue, it was observed that TiO2 fibers have a higher decomposition efficiency than the self-made TiO2 powders, as well as the commercial P25. The optimal conditions were a concentration of 9 × 10−3 mol/l at pH 6 with 40 W of illumination for the fastest rate of methylene blue photodegradation. Diffuse reflectance UV–Vis analysis showed a shift in the threshold absorption value and a corresponding increase in bandgap energy for TiO2 fibers, which is considered to be responsible for the decrease in TiO2 fibers photoactivity after 15 trials.