Photocatalytic detoxification with the thin-film fixed-bed reactor (TFFBR): Clean-up of highly polluted landfill effluents using a novel TiO 2-photocatalyst

Abstract

Two different photocatalysts, namely Hombikat UV100 (Sachtleben Chemie) and P25 (Degussa) have been used in batch experiments to compare their ability to degrade the toxic components of a biologically pretreated landfill leachate. A strong adsorption of the pollutant molecules was observed for both TiO 2-powders, with a maximum of almost 70% TOC reduction for Hombikat UV100, making it almost impossible to draw a quantitative comparison of the degradation with the two catalysts in the batch system. The photocatalytic activity of Hombikat UV100 was also tested using a thin-film fixed-bed reactor (TFFBR) configuration under artificial solar UV-irradiation. Here the catalyst was fixed onto a glass-plate to avoid separation of the catalyst and water after the treatment. The highest degradation rate was observed at pH 5, using a moderately diluted waste water. In good agreement with the degradation rate's pH dependency adsorption measurements showed a maximum adsorption of the organic pollutants onto Hombikat UV100 TiO 2 at pH 5. Photonic efficiencies (ζ) based on the amount of incident irradiation have been calculated for the experiments, ζ could be increased by a reduction of the light intensity. While the addition of H 2O 2 had an inhibiting effect (at pH 7), the presence of Na 2S 2O 8 led to a dark reaction. Studies performed under continuous recirculating conditions showed that even undiluted waste-water streams can, in principle, be degraded completely.