Application of immobilized horseradish peroxidase for removal and detoxification of azo dye from aqueous solution

The development and application of an immobilized horseradish peroxidase (HRP) on calcium alginate gel beads are reported for the successful and effective decolorization textile industrial effluent. The optimal condition for the immobilization of HRP on calcium alginate gel beads which leads to a specific activity of 15 U/g calcium alginate was identified. Upon immobilization, considering enzyme encapsulation efficiency, retention activity and enzyme leakage of the capsules, the best gelation condition was found to be 2 % w/v of sodium alginate solution and 2 % w/v of calcium chloride hexahydrate. Upon immobilization, pH profile of enzyme activity changes as it shows higher value at basic and acidic solution. The capsules were reusable up to ten cycles but decreased in their efficiency. The ratio of hydrogen peroxide/dye at which highest dye removal occurs is 1.25. Optimum conditions for removal of AO-7 and AB-25 were: 90 min, reaction time; 0.8 units/g, enzyme concentration for 500 ADMI colore, ratio of H2O2 /dye, 1.25/1; temperature, 25-50°C that cause 75% and 84% removal in AO-7 and AB-25 solution respectively. There was a significant reduction in toxicity of dye solution after the enzymatic treatment.