Modeling the discoloration of a mixture of reactive textile dyes by commercial laccase.

Degradation of a mixture of three reactive textile dyes (Reactive Black 5, Reactive Yellow 15 and Reactive Red 239), simulating a real textile effluent, by commercial laccase, was investigated in a batch reactor. The discoloration was appraised as a percentage of the absorbance reduction at the wavelength of maximum absorbance for each dye and as total color removal based in all visible spectrum. A significantly high discoloration was achieved in both cases, indicating the applicability of this method for textile wastewater treatment. Mathematical models were developed to simulate the kinetics of laccase catalyzed degradation of reactive dyes in mixtures. Like in single dye degradation, some of the reactions present an unusual kinetic behavior, corresponding to the activation of the laccase-mediator system. The kinetic constants of the models were estimated by minimizing the difference between the predicted and the experimental time courses. Although not perfect, the ability of the models in representing the experimental results suggests that they could be used in design and simulation applications.