Cobalt is one of the three naturally occurring magnetic metals in addition to iron and nickel. Cobalt has the highest curie point of all metals at 1,121°C (the temperature above which a ferromagnetic material loses its ferromagnetism).
The main source of cobalt accounting for approximately 85% of annual production globally, is as a byproduct of nickel mining (about 48%) and copper mining (about 37%). Some 15% of cobalt is produced primarily from various metallic-lustered ores, for example cobaltite, erythrite and skutterudite. Cobalt is predominantly used in the preparation of magnetic, corrosion and wear-resistant high-performance alloys. Diverse industries including alloys, battery manufacturers, manufacturers of cobalt acetate and other cobalt compounds used as catalysts in chemical reactions, radioisotopes and electroplating among others are key target markets.
The main ores of cobalt are cobaltite, erythrite, glaucodot and skutterudite (see above), but most cobalt is obtained by reducing the cobalt by-products of nickel and copper mining and smelting.
Since cobalt is generally produced as a by-product, the supply of cobalt depends to a great extent on the economic feasibility of copper and nickel mining in a given market. Demand for cobalt was projected to grow 6% in 2017.
Primary cobalt deposits are rare, such as those occurring in hydrothermal deposits, associated with ultramafic rocks, typified by the Bou-Azzer district of Morocco. At such locations, cobalt ores are mined exclusively, albeit at a lower concentration, and thus require more downstream processing for cobalt extraction.
Several methods exist to separate cobalt from copper and nickel, depending on the concentration of cobalt and the exact composition of the used ore. One method is froth flotation, in which surfactants bind to ore components, leading to an enrichment of cobalt ores. Subsequent roasting converts the ores to cobalt sulfate, and the copper and the iron are oxidized to the oxide. Leaching with water extracts the sulfate together with the arsenates. The residues are further leached with sulfuric acid, yielding a solution of copper sulfate. Cobalt can also be leached from the slag of copper smelting.
The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to metal by the aluminothermic reaction or reduction with carbon in a blast furnace.