Platinum is a rare metal. The colour of the metal appears silver-white. Besides the making of jewellery, platinum serves various purposes like medical and chemical applications. This suitability for varied industrial applications is because of its unique physical and chemical properties. Platinum shows features such as corrosion resistance, malleability, ductility, conductivity, etc.
Platinum grains can exist in their pure forms. The metal also exists as an alloy, with the other metals such as iron, gold, nickel, and PGMs. The main ore minerals of platinum are pyrrhotite, pentlandite, cubanite, etc. The process of extracting platinum from its ore involves various techniques. The main steps involved in the process are:
Comminution: This process involves crushing and grinding large ore particles of PGM into fine particles. After rubbing, the jewellers apply the gravity separation method that separates particles by the weight.
Flotation: Flotation helps to separate particles that float from the particles that sink. Jewellery manufacturers use Xanthate and dithiophosphate as reagents for flotation. A PGM concentrate containing sulfide will remain in the flotation.
Smelting: Smelting separates the sulfides from the valueless minerals like silicates in the ore (gangue minerals). The application of thermal energy helps in separating them. The operating temperature can reach up to 900° Celsius. Molten gangue minerals and PGMs with sulfides form different layers. The former appears to be a slag layer, and the latter creates a matte layer. The jewellers feed this matte layer to the converters.
Converting: Converting removes iron and sulfur content in the layer. The process converts sulfur to sulfur dioxide and iron to ferrous oxide using oxygen. After cooling the converter matte, the next process is supplying the same to the base metals refinery.
Purification (Refining): The various techniques used for purification are dissolution-precipitation, solvent extraction, ion exchange, and molecular recognition technology. The dissolution-precipitation process involves pressure oxidation leach that filters the base metals and leaves behind the PGM residue. Then the PGM remains will be sent to the precious metal refinery, from where it is possible to separate the individual metals by using the various precipitation methods.