Effect of additional Fe salt on electrocoagulation process for the degradation of methyl orange dye: An optimization and kinetic study.

The wastewater generated from textile industries is highly colored and contains dyes including azo dyes, which are toxic to human and water-living organisms. The treatment of these azo dyes using conventional treatment techniques is challenging due to their recalcitrant properties. In the current study, the effect of additional Fe on electrocoagulation (EC) using Fe electrodes has been studied for the removal of methyl orange (MO) azo dye. pH between 4-5 was found to be optimum for EC and treatment efficiency decreased with increasing dye concentrations. With the addition of Fe salt, dye removal for a certain concentration was increased with the increase of current density and Fe up to a certain limit and after that, the removal efficiency decreased. The COD, color and dye removals were 88.5%, 93.1% and 100%, respectively, for EC of 200 mg.L dye solution using only 0.20 mmol.L Fe for 0.40 mA cm current density, whereas for EC, the respective removal efficiencies were 76.7%, 63.4% and 82.4% for 32 min. The respective operating cost for EC was $768 kg removed dye ($0.342 m), whereas, for EC with additional Fe salt, it was $350 kg removed dye ($0.189 m). The kinetic results revealed that the first-order kinetic model was fitted best for EC, whereas the second-order kinetic model was best fitted for Fe added EC. For real textile wastewater, 57.6% COD removal was obtained for 0.15 mmol.L Fe added EC compared to 27.8% COD removal for EC for 32 min. Based on the study we can conclude that Fe assisted EC can be used for effective treatment of textile wastewater containing toxic compounds like azo dyes.