Solar photocatalysis for detoxification and disinfection of water: Different types of suspended and fixed TiO2 catalysts study

Photocatalysis by titanium dioxide (TiO₂), operational in the UV-A domain with a potential use of solar radiation, could be an alternative to conventional water detoxification and disinfection technologies. However, employing the photocatalyst as a suspension or slurry makes the scaling-up of the process difficult, as the TiO₂ has to be removed from the decontaminated water to be reused several times. In this work the photocatalytic activity of different types of TiO₂ catalyst (Degussa P-25, Millennium PC-100 and PC-500, Tayca AMT-100 and AMT-600) in suspension or coated on fibrous web were studied in both decontamination and disinfection experiments at laboratory scale. Gallic acid was chosen as the model pollutant for detoxification experiments and Escherichia coli as the model microorganism for disinfection experiments. The influence of the surface area and other characteristics of TiO₂ are discussed concerning the photocatalytic properties of TiO₂. The role of adsorption is suggested, indicating that the reaction occurs at the TiO₂ surface and not in the solution. Gallic acid degradation kinetics were found to be of the same extent for both TiO₂ suspended and fixed, whereas for the bacterial inactivation efficiency was significantly less important with coated than with suspended TiO₂.