Effect of the nature of the supporting electrolyte on the treatment of soluble oils by electrocoagulation

Electrochemical wastewater treatment technologies have to be applied to wastes of a sufficient conductivity. In case of too low conductivity of the wastewater salts have to be added to increase it. Therefore it is important to know at least qualitatively the effect of both cations and anions on the overall electrochemical operation. The present investigation was aimed at observing the influence of the electrolyte nature, by considering chloride, sulfate and nitrate anions with sodium, potassium or ammonium cations on the treatment of dilute suspensions of soluble cutting oils, and using Al or Fe electrodes. Aluminium electrodes can be dissolved with a high current efficiency in all cases, whereas dissolution of iron is little efficient with nitrate salts and potassium sulfate. In addition, the cell voltage required with Fe electrodes to allow the same current density can be 2 V higher than with Al plates. The specific energy required for the electrochemical process with a 3 mm gap cell was estimated to range from 0.75 kWh m− 3 with Al electrodes in sodium chloride media to approx. 5 kWh m− 3 with Fe electrodes immersed in sulfate solutions.