Biodegradation of reactive yellow EXF dye: optimization of physiochemical parameters and analysis of degradation products

Abstract

Biological decolourization of textile dyes is getting more attention as a cost-effective and environmentally friendly technique. Bacterial strain Proteus mirabilis has been identified as an effective decolourizer of Reactive Yellow EXF dye. Laboratory-scale experiments were carried out to study effects of physicochemical parameters (pH, temperature, concentration of dye, agitation and sources of carbon) for the maximum decolourization, and the structural changes caused in the dye due to biological treatments were investigated. Maximum decolourization of the dye was observed at 40 °C and pH 7–8. The highest percentage colour removal of more than 95% at 48 h of incubation was observed in the medium containing 5 g/l yeast extract as the carbon source. Further, this bacterial strain could tolerate high concentrations of dye and decolourize dye solutions of 500 mg/l. Ultraviolet–visible spectra and high-performance liquid chromatography analyses clearly indicated changes in dye structures due to treatment. Compounds formed due to degradation of the dye under static and shaking conditions were analysed using gas chromatography–mass spectrophotometry and found to be non-toxic and benign.