Photocatalytic detoxification with the thin-film fixed-bed reactor (TFFBR): Clean-up of highly polluted landfill effluents using a novel TiO2-photocatalyst

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 TiO2-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 TiO2 at pH 5. Photonic efficiencies (zeta) based on the amount of incident irradiation have been calculated for the experiments, zeta could be increased by a reduction of the light intensity. While the addition of H2O2 had an inhibiting effect (at pH 7), the presence of Na2S2O8 led to a dark reaction. Studies performed under continuous recirculating conditions showed that even undiluted waste-water streams can, in principle, be degraded completely. Copyright (C) 1996 Elsevier Science Ltd.