Abstract

SOLIS-OBA, M. et al. Comparison of advanced techniques for the treatment of an indigo model solution: Electro incineration, chemical coagulation and enzymatic. Rev. Mex. Ing. Quím [online]. 2009, vol.8, n.3, pp.275-282. ISSN 1665-2738.

Indigo blue is one of the most important textile dyes. The wastewaters for indigo blue used are thought to be contaminated because; indigo can be oxidized to isatin, which is hydrolyzed to antranilic acid, a compound that is toxic to aquatic life. Indigo oxidation was evaluated using a model solution that simulated a textile wastewater. Three oxidation systems: electro incineration, chemical coagulation using Al₂ (SO₄)₃, and enzymatic degradation with laccase. With electro incineration, the indigo solution was completely discolored; chemical oxidation demand diminution was 98% in approximately 3 hours and indigo blue was mineralized with no sludge production. Chemical coagulation with 40 mg L^-1 sulfate aluminum removed some color though control of pH was necessary. At pH 5, the chemical oxygen demand was reduced by 76%, with sludge formation. Laccase enzyme, processing required 72 hours for complete discoloration of the indigo model solution; chemical oxidation demand diminution was nearby 50%, but laccase could not mineralize the dye. Toxicity assays indicated that the processes generated more toxic products than the control.

Keywords : electro incineration; indigo; oxidation; chemical coagulation; laccase; toxicity.