Oil removal from oil-water emulsion by electrocoagulation in a cell with rotating cylinder anode

Abstract

The performance of a batch electrocoagulation cell (rotating cylinder electrochemical reactor) in the demulsification of crude oil emulsions was investigated. The cell used a rotating Al cylinder as anode and a stationary cylindrical screen of aluminum as cathode. Parameters studied are the current density, the NaCl concentration, initial pH, the anode rotation speed, initial oil concentration and the nature of the supporting electrolyte. Increasing the current density led to increasing the rate of de-emulsification; a current density of 11.4mA/cm2 allowed complete separation in 10 minutes while a current density of 17.1mA/cm2 allowed complete separation in 6 minutes. The optimum pH range for the electrocoagulation is 7-11, acidic media (pH 3-5) retarded the electrocoagulation. The increase in the concentration of the NaCl led to an increase in the rate of oil removal. Higher electrolyte conductivity of the emulsion increased the rate of oil removal. Anode rotation was found to have a strong effect in improving oil removal efficiency. The higher the initial concentration of the emulsion, the higher the rate of oil removal. NaOH was found to be the best electrolyte, followed by NaCl, then KCl and finally NH4Cl.