Commercial Production of Indium

CIM Bulletin, 1959

B. G. HUNT ; C. E. T. WHITE ; R. A. KING

This paper reviews the history, occurrence, properties, and uses of indium, and describes the commercial production and fabrication of that metal by The Consolidated Mining and Smelting Company of Canada, Limited (Cominco), at Trail, B.C'. Indium is produced commercially at Trail from dross re-treatment furnace D.R.F.) slag, a complex byproduct of the lead smelting operations. Furnace feed prepared from this slag is smelted with coke and limerock in an electric furnace. The e1ectric furnace bullion is parted electrolytically, producing a marketable lead-tin alloy containing about 8 per cent tin, and leaving the indium in the anode slime. Recovery of indium from the anode slime involves roasting the slime with sulphuric acid, followed by leaching with water, purifying the leach solution, recovering the indium by sponging with zinc or aluminum, and refining electrolytically. This process yields standard grade (99.97+ per cent) indium which is either sold or refined to high purity ( 99.999 per cent) indium for special uses requiring higher purity metal.
Keywords: Alloys, ALLOYS Indium, electrolyte, standard grade, sulphuric acid, zinc, Furnaces, Lead, metals, Slag, Slags, Slimes, tin