Development of a Continuous Fluidic Reactor for the Photocatalytic Treatment of Liquid Effluents

The present study aims at developing a photocatalytic mesofluidic reactor for the continuous treatment of liquid effluents. The main idea to reach this objective is to deposit TiO2 thin films onto the inner walls of the fluidic reactor by using a sol-gel process. Glass and PFA (perfluoroalkoxy alkane polymer) are selected as construction materials for the fluidic reactor prototypes. In a first time, the operational conditions leading to a sufficient photocatalytic activity for methylene blue degradation are determined for TiO2 thin films deposited onto glass substrates through dip coating. The best photocatalytic activity is obtained for glass samples coated according to a procedure involving a withdrawing speed of the dipcoater of 60 mm min-1, a calcination temperature of 500 °C and a sol doped with 10 wt% of commercial TiO2 (Evonik P25). Next, to transpose this method to PFA substrates, it is slightly altered to take the specific TiO2-PFA adhesion requirements and the maximum temperature for PFA into account. Photocatalytic activity of the films is studied for the degradation of methylene blue in a batch reactor, as well as in a mesofluidic falling-film reactor. The deposition method onto PFA flat substrates is finally adapted to PFA capillaries. ESEM analysis reveals the presence of TiO2 on the inner walls of the capillaries and the methylene blue degradation tests shows their good photocatalytic activity. Thus the feasibility of deposing a photo-active TiO2-film on the inner PFA walls of a mesofluidic capillary reactor by the sol-gel process for the degradation of methylene blue is proved.