Chapter 29 - Extraction of Cobalt from Nickel Laterite and Sulfide Ores

Abstract

This chapter describes the processes by which cobalt is made and its recovery. Primarily, cobalt is extracted as a by-product from leaching of nickel laterite ores and smelting of nickel sulfide ores. Both these processes produce an intermediate sulfide that is refined by hydrometallurgical techniques. Cobalt is produced as a by-product from leaching of the limonite layer of the laterite ore. Most of the cobalt and nickel is first precipitated as a mixed sulfide that is then refined to metallic nickel and cobalt. High-purity cobalt is then obtained from mixed sulfide precipitates through refining, which involves leaching using chlorine in hydrochloric acid, solvent extraction for separation of cobalt and nickel, solution purification and electrowinning or hydrogen reduction for recovery of cobalt metal. Cobalt occurs in all nickel sulfide ores, mostly in pentlandite. It is recovered by first producing a flotation concentrate, then smelting and converting it to molten nickel-copper-cobalt sulfide matte. This is then solidified and leached using chlorine in hydrochloric acid, or using air in ammonia solutions, or using oxygen in sulfuric acid and producing cobalt metal by electrowinning or hydrogen reduction from purified leach solutions. The industrial recoveries of cobalt from sulfide ores are least in the smelter, indicating that companies processing sulfide ores need to improve the recovery of cobalt in the smelter for greater benefits.