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

In the present study, the decolorization and degradation of reactive black 5 (rb5) azo dye was investigated bybiological, photocatalytic (uv/tio2) and combined processes. application of candida tropicalis jks2 in treatment ofthe synthetic medium containing rb5 indicated complete decolorization of the dye with 200 mg/l in less than 24h. degradation of the aromatic rings, resulting from the destruction of the dye, did not occur during the biologicaltreatment. mineralization of 50 mg/l rb5 solution was obtained after 80 min by photocatalytic process (in presenceof 0.2 g/l tio2). cod (chemical oxygen demand) was not detectable after complete decolorization of 50 mg/l rb5solution. however, photocatalytic process was not effective in the removal of the dye at high concentrations (?200mg/l). with 200 mg/l concentration, 74.9% of decolorization was achieved after 4 h illumination underphotocatalytic process and the absorbance peak in uv region (attributed to aromatic rings) was not completelyremoved. a two-step treatment process, namely, biological treatment by yeast followed by photocatalyticdegradation, was also assessed. in the combined process (with 200 mg/l rb5), absorbance peak in uv regionsignificantly disappeared after 2 h illumination and about 60% cod removal was achieved in the biological step. itis suggested that the combined process is more effective than the biological and photocatalytic treatments in theremediation of aromatic rings.