STUDIES ON LOW-TEMPERATURE AL ELECTROLYSIS USING COMPOSITE ANODES IN NAF-KCL BATH ELECTROLYTE

Liquidus behavior, alumina solubility, electrical conductivity, and decomposition potential of Al2O3 in Various compositions of molten fluoride-chloride salt mixture, NaF-KCl, have been studied to find out the suitability of the system as a candidate bath electrolyte for an alternative process of low temperature aluminum electrolysis using composite anodes. Composite anodes, consisting of a mixture of Al2O3 and carbon, of different compositions were prepared and characterized by determining their properties such as apparent density, porosity, and resistivity. A laboratory scale experimental cell of about 30 A capacity was run with the composite anodes and 50:50 mole percent (m/o) mixture of NaF and KCl as the bath electrolyte at similar to 750 degrees C. The composite anodes with 50 w/o Al2O3 were consumed readily during electrolysis, and aluminum metal was obtained. Material and charge balances of the electrolysis experiment show 99.7% anodic and 64.5% cathodic efficiencies.