Electrorefining of aluminum using ceramic fiber diaphragm permeated with chlorides

Feasibility of electrorefining was studied. 6wt% A1C13 was contained in binary chloride electrolytes chosen from NaCl, KCl, LiCl and MgCl2 with melting points from 398° to 670°C. Electrorefining was made at 700°C. The cathode current efficiency lowers with prolonged electrolyzing time and also with increasing current density. The diaphragm should be 4.5 mm in thickness to assure the current density 0.1 A/cm2 for electrorefining at the voltage 0.5V. Electric power consumption for electrorefining will be under 1,700 kWh per ton of refined aluminum excluding heating energy for bath temperature, if the cathode current efficiency is 90% or more. The cathode current efficiency is, however, not so high in this work.