Abstract
Response surface methodology (RSM) was applied to optimize the decolourization of 3 dyes belonging to 3 dye families such as reactive black 5 (diazoic), indigo carmine (indigoid) and aniline blue (anthraquinonic). Crude laccase from Trametes trogii and the laccase-mediator 1-hydroxybenzotriazole (HBT) were used in this study. Box–Behnken design using RSM with six variables namely pH, temperature, enzyme concentration, HBT concentration, dye concentration and incubation time was used in this study to optimize significant correlation between the effects of these variables on the decolourization of reactive black 5 (RB5), indigo carmine (IC) and aniline blue (AB).
The optimum of pH, temperature, laccase, HBT, RB5 and reaction time were 4.5, 0.5 U ml-1, 0.5 mM, 100 mg ml-1 and 150 min respectively, for a maximum decolourization of RB5 (about 92.92% ± 7.21). Whereas, the optimum decolourization conditions of both IC (99.76% ± 7.75) and AB (98.44% ± 10) were: pH 4.5, temperature of 45 °C, enzyme concentration of 0.1 U ml-1 and 0.5 U ml-1, HBT concentration of 0.9 mM and 0.5 mM, dye concentration of 60 mg l-1 and reaction time of 150 and 90 min, respectively.
The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R2) being 0.864, 0.663 and 0.776 for RB5, IC and AB, respectively. In addition, when the kinetic parameters for the three dyes decolourization were calculated according to Hannes–Wolf plot, the following values were obtained: Km of 268.4, 47.94 and 44.64 mg l-1 then Vmax of 35.58, 10.43 and 9.23 mg l-1 min for the RB5, IC and AB decolourizations by laccase, respectively.
The optimum of pH, temperature, laccase, HBT, RB5 and reaction time were 4.5, 0.5 U ml-1, 0.5 mM, 100 mg ml-1 and 150 min respectively, for a maximum decolourization of RB5 (about 92.92% ± 7.21). Whereas, the optimum decolourization conditions of both IC (99.76% ± 7.75) and AB (98.44% ± 10) were: pH 4.5, temperature of 45 °C, enzyme concentration of 0.1 U ml-1 and 0.5 U ml-1, HBT concentration of 0.9 mM and 0.5 mM, dye concentration of 60 mg l-1 and reaction time of 150 and 90 min, respectively.
The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R2) being 0.864, 0.663 and 0.776 for RB5, IC and AB, respectively. In addition, when the kinetic parameters for the three dyes decolourization were calculated according to Hannes–Wolf plot, the following values were obtained: Km of 268.4, 47.94 and 44.64 mg l-1 then Vmax of 35.58, 10.43 and 9.23 mg l-1 min for the RB5, IC and AB decolourizations by laccase, respectively.
| Original language | English |
|---|---|
| Pages (from-to) | 84-91 |
| Number of pages | 8 |
| Journal | Journal of Environmental Management |
| Volume | 108 |
| Early online date | 1 Jun 2012 |
| DOIs | |
| Publication status | Published - 15 Oct 2012 |
Keywords
- optimization
- laccase
- synthetic dyes
- box-behnken
- decolourization