Abstract
In this work the decolourization of Direct Blue 2 dye (DB2) using an industrial soybean waste as a source of peroxidases was studied. Temperature, pH, amount of H2O2 and concentration of dye were evaluated to determine the maximum catalytic activity of the enzyme during the dye degradation process. It was observed that a temperature of 40°C, a pH of 5 and a concentration of 40 mg/L for the dye in aqueous phase, play a significant role in the overall enzyme-mediated reaction. The maximum decolourization efficiency achieved under optimal conditions was 70% ± 4%. HPLC studies were carried out to confirm dye degradation and analyse the intermediate metabolites. The oxidation products quantified during the reaction were benzidine and 4 aminobiphenyl. Also, an increase in toxicity, determined by Vibrio fisheri, was observed after the enzymatic oxidation of the dye. Results suggest that the oxidation of DB2 with peroxidases can be recommended as a pretreatment step before a conventional treatment process.
Highlights
The textile industry is one of the major sources of water pollution due to the volume and composition of effluents produced, which are typically characterized as having a high temperature, pH and colour (Srinivasan and Viraraghavan, 2010; Kumar et al, 2007)
We present results obtained from a partially purified extract from an industrial soybean waste and its application in the decolourization of the Direct Blue 2 dye (DB2), widely used in the textile industry for dyeing denim
Experimental data from this study showed that when partial purification by chromatography using a column of DEAE53-cellulose is applied, the peroxidase activity can be increased to 15 ± 5 U/mL
Summary
The textile industry is one of the major sources of water pollution due to the volume and composition of effluents produced, which are typically characterized as having a high temperature, pH and colour (Srinivasan and Viraraghavan, 2010; Kumar et al, 2007). The environmental impact caused by this industrial sector is varied, but colour is the first sign of contamination observed in effluents, with concentrations as high as 1 g/L (Kaushik and Malik, 2009). Azo dyes constitute the most important family of industrial dyes. They are recalcitrant and xenobiotic compounds characterized by the presence of one or more azo groups (–N=N–), that make them extremely difficult to eliminate by biodegradative processes (Melgoza and Buitrón, 2004). It is well known that the amount of dye wasted in the effluents depends on the application type used, varying from 2% to 50%, which is discharged (in the absence of adequate previous treatment) into water bodies (Dos Santos et al, 2007)
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