Photooxidation: A Decolorization Procedure and a Pre-Treatment Step for Biodegradation of Reactive Azo Dye
N. Genç, E. Can-Dogan
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University of Kocaeli, Department of Environmental Engineering, 41040 Kocaeli, Turkey
Pol. J. Environ. Stud. 2006;15(1):73–79
In this study, by using a different variety of TiO2 catalyst, photocatalytic oxidation of reactive azo dye used in textile industry and an improvement in the biodegradability of the dye by photocatalytic oxidation are investigated. It was found that the addition of TiO2 in the photooxidation of dye increased color removal by 30.84 %, the addition of H2O2 in the presence of TiO2 also increased color removal by 33.98 %. The study also examined the effect of TiO2 obtained from different companies in color removal and it was found that TiO2 obtained from Merck and Degussa displayed similar effectiveness in color removal. It was further found that, depending on the chemical composition of dye used, the ions, SO42-, Cl- and NH4+ emerged and that NH4+ was oxidized to NO2-. As a result of the 42 h long photocatalytic oxidation, a COD removal of about 85.3 % was achieved. In this study, Langmuir-Hinshelwood kinetic constants were examined and it was found that k=0.971 mg/L min and K=0.176 L/mg. By analyzing respirometric measures of raw and photocatalyzed dyes, it was determined that photocatalyzed dye had higher biodegradability than raw dye. Improvement in biodegradation was proven by the rise of BOD5/COD ratio from 0.06 to 0.29.