Decolourisation of reactive dyes with laccase-mediator system

What is it about?

Discharge of exhausted dyebath at the end of dyeing imposes huge waste-water load necessitating use of fresh water for further processing. Scarcity of fresh water has forced industries to decolourise drained out liquor to save environment and also to recycle and reuse the decolourised water for subsequent processing. A variety of existing methods are extensively used for decolourisation of dye with related inherent disadvantages. Decolourisation of dyes with the help of laccase has been found to be a promising technology to overcome the disadvantages of existing methods. In this work, the ability of laccase was evaluated for decolourisation of widely used reactive cold brand dyes with and without dyeing of cotton using statistical methods. A preliminary screening using several synthetic as well as natural redox mediators was performed to see their significance in decolourisation of dye. Decolourisation behaviour of few reactive cold brand dyes was assessed under optimum conditions and it was observed that decolourisation beyond 80% could be obtained with 1-hydroxybenzotriazole (HBT), veratric acid (VA) and benzotriazole (BT). Complete decolourisation is possible for few dyes in 24 h while few other dyes showed 77−89% decolourisation in 72 h of treatment. Experiments were also performed with the actual dyebath effluent and a significant decolourisation could be achieved for all the dyes too.

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