Dye decolourizing potential of laccase obtained from the white rot fungus Trametes trogii was studied for two reactive dyes; namely Reactive Black 5 (diazoic) and Reactive Violet 5 (monoazoic). The presence of a redox mediator as 1-hydroxybenzotriazole (HBT) was found to be essential for the decolourization of the said two dyes. The optimization of the decolourization process using experimental design was studied with three variables: dye (25, 50, 100 mg/L), enzyme (0.1; 0.5; 1 U/mL) and redox mediator (0.1; 0.5; 1 mM) concentrations. Results of this investigation revealed that the optimum concentrations of dye, enzyme and HBT for the degradation of the Reactive Black 5 (RB5) were 25 mg/L, 1U/mL and 1 mM, respectively, for a maximum decolourization about 93%. However, the optimum concentrations for Reactive Violet 5 (RV5) were found to be 25 mg/L, 0.5 U/mL and 0.5 mM, for a total removal of the dye. The apparent capacity of this laccase to decolourize azo dyes make it a suitable candidate for further applications in biobleaching and the treatment of textile effluents.

Polymeric fibres are semicrystalline structures in which macromolecules are rarely oriented in their equilibrium state. Further instabilities are imparted when the fibres are converted into yarns and the yarns into fabrics. Heat setting is an important industrial process, as it reduces the fibre strain to an acceptable limit. Although this process provides dimensional stability to polyamide 6.6, yet it affects its dyeability. This paper investigates the effects of hot water setting treatment on the dyeing properties of grafted polyamide 6.6 microfibres dyed with a cationic dye. It reveals that the dye uptake of the hot water-set samples is inferior to those unset. A kinetic study showed a change in the build-up rate. In addition, an increase in the percentage of grafting improved the quantity of the dye fixed on both unset and hot water-set samples. Comparing the wash fastness of the unset samples, the hot water ones are found to be lower. The modelling of the adsorption isotherms using Langmuir, Freundlich and Jossen relations allows the determination of isotherm constants. The results obtained have been modelled using standard adsorption isotherms.