Advanced photocatalytic oxidation processes for micropollutant elimination in municipal and industrial water

Abstract

Since pollutants that cannot be degraded by conventional wastewater treatment techniques are a problem of increasing importance nowadays, a lot of research is focused on finding solutions to resolve this problem. A promising technology in this field is TiO2 photocatalysis, which is studied more in detail in this work. TiO2-based photocatalysts, in which silver is used as a dopant, were synthesized by the sol-gel technique. Then, thin films of these sols were deposited onto microscope slides by dip-coating and crystallization of these films was achieved in the subsequent calcination step. For these photocatalysts, the effects of different silver fractions, different fractions of the commercial photocatalyst Evonik P25, different calcination parameters, and different supports (glass or steel) were compared. For this purpose, the photocatalysts were characterized by profilometry, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and nitrogen adsorption-desorption. In addition to these characterizations, the efficiency of the photocatalysts was compared by ozonation-photocatalysis combined degradation tests, performed on solutions containing 10 model pollutants. It was found that some of these model pollutants, which could not be degraded by ozonation only, could be degraded by combined ozonation-photocatalysis treatment. The best degradation results were obtained for photocatalyst films consisting of TiO2 doped with 2 wt.% of silver and 20 wt.% of the commercial photocatalyst Evonik P25.