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Degradation of a textile reactive azo dye by a combined biological-photocatalytic process: Candida tropicalis Jks2 -Tio2/Uv

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Author(s): Narjes Jafari | Rouha Kasra-Kermanshahi | Mohammad Reza Soudi | Amir Hossein Mahvi | Sara Gharavi

Journal: Iranian Journal of Environmental Health Science & Engineering
ISSN 1735-1979

Volume: 9;
Issue: December;
Start page: 1;
Date: 2012;
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Keywords: Azo dyes | Candida tropicalis | Combined wastewater treatment

ABSTRACT
In the present study, the decolorization and degradation of Reactive Black 5 (RB5) azo dye was investigated by biological, photocatalytic (UV/TiO2) and combined processes.Application of Candida tropicalis JKS2 in treatment of the synthetic medium containing RB5 indicated complete decolorization of the dye with 200 mg/L in less than 24 h. Degradation ofthe aromatic rings, resulting from the destruction of the dye, did not occur during the biological treatment. Mineralization of 50 mg/L RB5 solution was obtained after 80 min by photocatalytic process (in presence of 0.2 g/L TiO2). COD (chemical oxygen demand) wasnot detectable after complete decolorization of 50 mg/L RB5 solution. However,photocatalytic process was not effective in the removal of the dye at high concentrations (≥200 mg/L). With 200 mg/L concentration, 74.9% of decolorization was achieved after 4 hillumination under photocatalytic process and the absorbance peak in UV region (attributed to aromatic rings) was not completely removed. A two-step treatment process, namely,biological treatment by yeast followed by photocatalytic degradation, was also assessed. In the combined process (with 200 mg/L RB5), absorbance peak in UV region significantly disappeared after 2 h illumination and about 60 % COD removal was achieved in the biological step. It is suggested that the combined process is more effective than the biological and photocatalytic treatments in the remediation of aromatic rings.

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