Influence of anions on Reactive Red 43 removal in electrochemical coagulation process

The electrochemical coagulation technique (EC) and potentiodynamic polarization tests were used to evaluate the influence of some anions as chloride, sulfate and nitrate on the removal of Reactive Red 43 (RR43) as a model pollutant using aluminum and iron anodes. Higher removal efficiency was obtained using aluminum anodes in the presence of chloride ions. Potentiodynamic polarization tests and determination of total Al3+ concentration showed that sulfate ions inhibit the release of Al3+ from the anode while in the existences of chloride and nitrate current efficiency was higher than 100%. Dye removal efficiency was considerably decreased by increasing the anion concentration and adding sulfate and nitrate to the solution containing chloride. In EC using iron anodes, the higher removal efficiency was achieved in the presence of chloride and sulfate ions. Potentiodynamic polarization tests revealed that the passive layer formation on the iron surface in the solution containing nitrate caused a considerable decrease in the current and removal efficiency. This passive layer was destroyed by adding chloride ions and in this condition, the removal efficiency and quantity of Fe2+ ions increased remarkably. According to the results, iron anode was more efficient than aluminum in the removal of RR43.