Aluminum Reduction by Impulse Electrolysis in Molten Electrolyte KF-AlF3-Al2O3

Abstract Pulsed electrodeposition of aluminum from KF-AlF3-Al2O3 melt at 1023 K was studied. Aluminum was deposited by pulse electrolysis with a cathode pulse current density of 22.81 A⋅cm-2 (average current density 5,7 A⋅cm-2) on liquid aluminium cathode. Weight balance of aluminium in the process of pulse electrolysis in the KF–AlF3–Al2O3 melt are described. The equation describing the dependence of the average cathode current density on the pulse current density is given. The KF-AlF3-Al2O3 melt can provide conditions for pulsed production of aluminum with high-amplitude currents. The higher the current density the more aluminum can be produced by pulse electrolysis than by galvanostatic electrolysis. The pulse electrolysis of aluminum is effective. Actual current efficiency was 49%. It was found that under pulsed electrolysis conditions a black salt crust formed on the anode. The following phases were detected in the salt crust: KAlF4, K3AlF6, Al2O3. It was experimentally proved that the pulse electrolysis can be a new direction for the development of the aluminum reduction process. The pulse electrolysis of molten salts provides the opportunity to increase the specific amount of electricity compared to galvanostatic electrolysis and thus to increase the productivity of the electrochemical cell.