Surface Properties of Photocatalytic Nano-Crystalline Titania Films and Reactor for Photocatalytic Degradation of Chloroform

In this work two immobilizations techniques of TiO₂ onto glass were investigated; deposition of previously made titania powder (PMTP) and a sol-gel method. The titania powder used in this work was Degussa P25, Hombikat UV100 and a powder prepared in our laboratory SC134. The prepared TiO₂ films were characterized using XRD, XPS, AFM, UV-Vis spectroscopy and the photocatalytic activity was assessed using stearic acid as a model compound.

Investigation of the prepared films showed that the films prepared from Degussa P25 was the most active, followed by the Hombikat UV100 film, Sol-gel film, and SC134 film. The activity of the films is assumed to be related to the crystallinity of the TiO₂ as no major differences were found between the films using XPS analysis. Based on XPS investigation of the films before and after UV irradiation it was suggested that the photocatalytic destruction of stearic acid proceeds partly through formation of hydroxyl radicals which are formed from adsorbed hydroxyl groups. 

The investigation also showed that the rate of degradation increases linearly with the concentration of TiO₂ in the films, these findings suggests that the amount of TiO₂ in the film is the limiting condition for the rate of reaction.

Also a new type of continuous photoreactor was developed in which the TiO₂ catalyst made from Sol-gel film was immobilized on the surface of quartz tubes surrounding the UV lamps and on the internal surface of the reactor walls. The study showed that an initial concentration chloroform of 7 mg/l was degraded in a period of 500 hour. The kinetics of the degradation of chloroform in the flow reactor was found to obey Langmuir-Hinshelwood kinetics.

The investigation also showed that the reactor design has a significant influence on the rate of degradation, as it was observed that the position of the coated lamp in the reactor yield different degradation rates.