Treatment of textile dyes effluents by laccase mediator system
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: Laccase, Dyes, Textile industry, decolourisation, Mediator
In textile industry, colour is applied to finished products through dyeing, resulting in the generation of different wastewaters. Textile industries release during the process large quantities (about 10% of total wastewater) of intensely coloured and toxic effluents, which cause serious environmental pollution. A number of biotechnological approaches have been suggested with potential interest in combating this pollution source in an eco-efficient manner. It is known that lignolitic enzymes (laccase) can be used to decolorize dyes. The range of laccase substrates can be extended to nonphenolic compounds by inclusion of a specific compound called mediator.
In this study decolourisation experiments were carried out with three industrial textile dyes supplied by DyStar (Portugal): Reactive Black 5, Reactive Blue 114 and Reactive Yellow 15. The commercial laccase (Denilite Base) was produced from genetically modified Aspergillus and was supplied by Novozymes. Five redox mediator 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS); violuric acid (VA); N-hydroxyacetanilide (NHA); 1-hydroxybenzotriazole (HBT) and 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) were employed in order to evaluate the laccase mediator system (LMS). The experiments were carried out in a 25 mL Erlenmeyer flask at different temperatures and pH values. Dye decolourization was determined by monitoring the decrease in the absorbance peak at their maximum wavelength of each dye.
The mediator screening showed that ABTS is a more effective mediator for the oxidative degradation of the reactive textile dyes. The decolourization by LMS is very sensitive with the temperature and pH, depending on the kind of dye. At lower temperatures (20-35ºC) no decolourization was observed as well as at pH above 3.0. However the optimum temperature and pH for dye degradation was 40ºC and pH 5.0 respectively, with 80% of maximum decolourization for Reactive Blue 114.
These results suggest that LMS is a suitable alternative for the removal of reactive dyes from wastewater streams. The commercial laccase (Denilite Base) is a promising enzyme for degradation of reactive textile dyes.
See the full pdf manuscript of the abstract.
Presented Monday 17, 13:30 to 15:00, in session Environmental Engineering & Management (T1-3P).
