Investigation of electrocoagulation on the removal of nickel in waste water from an electroplating bath using aluminium and iron electrodes

Abstract

The electrocoagulation (EC) has proven its effectiveness in the treatment of industrial effluents by the elimination of pollutants, especially metallic pollutants. The electrochemical processes that occur at the electrodes (aluminum or iron) give an excellent performance. In this work, EC tests were conducted on an industrial effluent from an electroplating bath. The goal is to eliminate the Nickel and reuse the purified water for other needs within the company. For this purpose, we proceeded to the optimization of the operating parameters acting on the efficiency of EC such as electric voltage, material of the electrode, stirring speed and interelectrode distance. We also evaluated these parameters’ effect on pH, conductivity, turbidity and nickel concentration. The tests were carried out in a perfectly stirred reactor on an industrial solution rich on nickel. The concentration of the effluent is 100 mg Ni 2+ /L. The nickel removal efficiency is approximately 78% for the following operating conditions: aluminum electrodes, regulated voltage of 6 volts, optimum stirring speed of 24 rpm and interelectrode distance of 2 cm. Resulting sludges from EC were characterized by X-ray diffractometry, infrared spectroscopy (IR) and scanning electron microscopy (SEM). We have identified a compound formed during the EC with Fe/Fe electrodes (Fe 2 Ni 2 (CO 3 ) (OH) 8 .2H 2 O (Nickel Iron Carbonate Hydroxide Hydrate) which is a corrosion inhibitor.