English
English
Metallurgical concentrates produced from mining operations need a final refining stage to produce pure metals. It is worth noting, concentrates produced consist of metal sulphide minerals, which are undesireable from a manufacturing perspective. Technology producers and manufacturers are reliant on the mining industry for a steady supply of pure refined metals. Unlike their parent sulfide minerals, metals are maleable, fusible, good conductors of electricity and non-reactive. These differences arise from the chemical state of a metal in a sulphide complex versus its pure metal form. For example, the mineral sphalerite is a zinc-sulphide (ZnS), where zinc is in the ionic form of Zn2+ and balanced by anionic sulphur S2-. Smelting of zinc concentrate is a high temperature reduction process where Zn2+ is converted to pure metallic zinc (Zn0) in a molten metal form with the loss of sulphur as the gas SO2.
The SO2 gas is collected to produce sulfuric acid, a common reactant used in the production of fertiliser and used in other chemical processes. Elements such as In, Ga, Ge, Te, Se and Cd among others can be electrolytically recovered at this stage to ensure the final metal produced is 99.99% pure. The pure molten Zn metal can now be cast into ingots or other shapes for distribution. On the one hand, the byproduct metals recovered can add significant value to a zinc ore in the case of the Energy Critical Elements (ECEs). On the other hand, elements such as cadmium, mercury, arsenic and thallium can decrease the value of an ore, resulting in penalties or fines incurred by the mining company which supplied the ore concentrate. Most of the world’s In, Ga, Ge, Te, Se and Cd are recovered as byproducts of the smelting process. Supplying the world’s future demand for these ECEs will require better identification of these elements in ores, improved recovery at smelters and discovery of new primary source enriched in ECEs.