ELECTROREFINING OF ALUMINUM SCRAP FROM CHLORIDE MELTS

The production of aluminium of primary quality from scrap by electrorefining may become an option of strategic importance. Two important requirements are: (i) substantial energy savings compared to electrowinning, and (ii) easy recycling of alloying elements and molten electrolyte without ecological hazards. The use of molten chloride instead of fluoride electrolytes is preferred as emissions are low, purification of contaminated salts in aqueous solution is easy and oxide ceramic materials for cells and diaphragms can be used. The measurement of formal potentials of most important alloying elements shows that only manganese should be expected to cause trouble in electrorefining of aluminium scrap from alkali chloride melts. Preparative batch refining experiments show that all these alloying metals can be easily separated; manganese is very likely because its activity in aluminium is decreased by alloying or compound formation in aluminium. Results with cells divided by alumina diaphragms show that energy consumptions can be kept below 5 kWh (kg Al)-1.