Effect of dye auxiliaries on color and COD removal from simulated reactive dyebath effluent by electrocoagulation

In this paper, application of electrocoagulation using common electrode materials (aluminum and stainless steel) to a simulated reactive dyebath effluent was investigated. A mixture of dyes and auxiliary chemicals rather than a single dyestuff was employed to reflect actual reactive dyeing conditions. The experimental study focused on the effect of individual reactive dyebath components on color and COD removal rates and efficiencies by electrocoagulation. Electrocoagulation using stainless steel electrodes was found to be more effective particularly for color abatement. Na₂CO₃ significantly reduced the process efficiency both in terms of color and COD removals. An adverse effect on COD removal efficiency was also observed for the sequestering agent. On the other hand, increasing the NaCl concentration not only enhanced color and COD removal efficiencies but also compensated the adverse effects of Na₂CO₃ and sequestering agent on the electrocoagulation process. The dominant mechanism of color and COD removals from reactive dyebath effluent by electrocoagulation seemed to be coagulation and adsorption at pH values above 11.