Photocatalytic oxidation of a reactive azo dye and evaluation of the biodegradability of photocatalytically treated and untreated dye

Abstract

The purpose of this study was to investigate the photocatalytic oxidation of a reactive azo dye and determine the improvement in the biodegradability when photocatalytic oxidation was used as a pretreatment step prior to biological treatment. The results obtained from the experiments adding H 2O2/TiO2 show that the highest decolorisation rate is provided by the combination of (UV+TiO2+H2O2). The decolorisation efficiencies were 18%, 22%, 34% and 52% in the runs UV, UV+H 2O2, UV+TiO2 and (UV+TiO2+H2O2) after approximately 100 min illumination periods, respectively. The decolorisation rate was increased significantly by initially increasing the concentration of TiO2 in the dye solution; however, it was decreased due to the reduced light transmission when the concentration of TiO2 was in excess. The decolorisation rate constant was 0.018 ± 0.002·min-1 in the presence of 1 g·l-1 TiO2 while it was 0.004 ± 0.001·min-1 in the presence of 0.125 g·l-1 TiO2.

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