Photocatalytic degradation of azo dyes in aqueous solution by using highly ordered titania nanotube films

The heterogeneous process of photocatalytic degradation of azorubine in aqueous medium on coatings of highly ordered TiO2 nanotube (NT) matrix was studied. The photoactive coatings consist of TiO2 NTs with an inner diameter of 115 +/- 10 nm, a wall thickness of 10 +/- 2 nm, and a length of 17.2 +/- 1.1 mu m. Using X-ray diffraction, it was shown that the studied TiO2 coatings have a nanosized polycrystalline anatase structure. It was found that the saturation of the nanotube coating with substrate played the key role in determining the rate of the photocatalytic process. The degree of saturation itself can be determined either by the intensity of mass transfer or by the surface area of the photocatalyst. Using electron spectroscopy, it was shown that the process of photocatalytic oxidation of azorubine on the surface of TiO2 NTs occurs without desorption of intermediate organic compounds into the reaction volume. Based on the obtained results, recommendations for the water purification application of TiO2 NT films as photoactive coatings in microchannel systems were formulated.