Separation of Oil from Oil–Water Emulsions by Electrocoagulation in an Electrochemical Reactor with a Fixed-Bed Anode

Abstract

In separation of oil from oil–water emulsion by electrocoagulation in an electrolytic cell with a fixed-bed anode which is made of randomly packed aluminum cylinders in a perforated plastic basket, the cathode was a horizontal aluminum plate placed below the bed anode at the cell bottom. The effects of different variables such as current density, bed height, cylinder diameter, NaCl concentration on the rate of oil removal, and electrical energy consumption were studied. Under optimum conditions, the separation efficiency reached 85 % after 5 min and a maximum of 99 % after 35 min. The rate of oil removal and oil separation efficiency increased with increasing the current density and NaCl concentration. Increasing bed height was found to increase the rate of oil removal and separation efficiency. It was also found that there was an optimum (cylinder diameter) at which the rate of oil removal and separation efficiency were higher than those at other diameters. Electrical energy consumption, which ranged from 0.35 to 27.5 kW h/kg of oil removed, was found to increase with increasing the current density, bed height and decreasing NaCl concentration. Energy consumption was found to decrease at optimum cylinder diameter. For 99 % oil removal, Al consumption under the present range of conditions ranged from 0.017 to 0.34 g/L of emulsion and the amount of sludge ranged from 0.55 to 1.48 g/L depending on the operating conditions. Comparison of the performance of the present cell with traditional cells shows that the present cell is superior to traditional cells such as the vertical parallel plate cell.