Treatment of orange II azo-dye by electrocoagulation (EC) technique in a continuous flow cell using sacrificial iron electrodes

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This paper describes the EC treatment of orange II dye solution in a flow cell using sodium chloride as an internal electrolyte. In this technique dye solutions were passed through a flow-through EC apparatus consisting of a flow-through cell, the electrode assembly, the feed pump and the DC power supply unit. The cell contained five parallel iron electrodes, which form four parallel cells. Experiments were run at 25 °C under various electrolyte concentrations, dye concentrations, current density, flow rate of the solution, and pH at dc current range of 2–5 A. Various number of recycles of the treated dye solution were also performed at the same dc current range. Optimum conditions to get high removal efficiency were experimentally determined. It was found that 98.5% of the dye was removed from the solution under the optimum conditions. The residue from a blank run (pH=7.3) and a dye added run (pH=8.5) were collected by vacuum filtration and analyzed by XRD after drying in a vacuum desiccator. The XRD data indicated the presence of mainly maghemite (γ-Fe 2O 3) and magnetite (Fe 3O 4) in the residue. However, there is not much difference between the X-ray diffractograms of the blank sample and the dye-containing residue to warrant any conclusions therefrom with regard to the interactions between the oxides and the dye molecules.