Platinum is one of the six Platinum Group Metals (PGMs), elements that share similar physical and chemical characteristics. This metal is significantly rarer than gold, making its extraction a complex and high-value endeavor. Platinum’s unique properties, including resistance to chemical attack and high temperatures, are necessary for numerous industrial applications. Extracting this metal from the earth and purifying it requires a long, multi-staged process involving sophisticated engineering and chemistry.
Where Platinum is Found and Mined
Platinum deposits are found almost exclusively within specific geological structures known as mafic and ultramafic igneous rocks. The world’s supply is heavily concentrated in a few locations, primarily within the Bushveld Igneous Complex in South Africa, which holds the vast majority of global reserves. This single location accounts for approximately 70% of the world’s annual production.
Additional production comes from the Norilsk region in Russia, where platinum is recovered as a byproduct of large-scale nickel and copper mining operations. Smaller deposits are also mined in the Great Dyke of Zimbabwe and the Stillwater Complex in Montana, United States.
The platinum-bearing ore layers often lie deep beneath the surface. Mining operations involve deep underground shaft systems that extend for kilometers to reach the valuable material. This depth adds considerable difficulty and expense to the initial extraction phase.
Initial Separation and Concentration
Once the platinum-bearing ore is brought to the surface, the first step is mechanical separation, known as comminution. The rocks are crushed and ground in large mills until they are reduced to a fine powder, which frees the PGM particles from the surrounding host rock.
The primary technique for initial concentration is froth flotation, which relies on the surface chemistry of the minerals. The fine powder is mixed with water and a blend of chemical reagents, including collector chemicals and frothers.
Air is then pumped into the mixture, creating a dense froth. The reagents cause the valuable PGM particles to adhere selectively to the air bubbles, lifting them to the surface. The waste rock, called gangue, remains submerged in the water.
This platinum-rich froth is skimmed off and dried, creating a mineral concentrate. While this concentrate is significantly richer in PGMs—sometimes over 50 times the original ore grade—it still contains base metals and impurities that must be removed later.
High-Purity Refining Processes
The refining process begins with pyrometallurgy, which involves using intense heat to further concentrate the metals. The dried concentrate is fed into a furnace and heated to temperatures exceeding 1,500°C in a process called smelting. This melts the material, forming a molten sulfide mixture known as a matte, which separates from the lighter slag layer.
After the initial smelting, the matte is subjected to further thermal processing, including converting, where air is blown through the material to remove unwanted elements like iron and sulfur. Subsequently, the matte is treated with strong acids in a process called leaching to dissolve and remove the remaining base metals, such as copper and nickel. This prepares the material for the delicate separation of the PGMs themselves.
The most intricate phase is hydrometallurgy, the chemical separation of platinum from its sister PGMs (palladium, rhodium, osmium, iridium, and ruthenium). The remaining material is dissolved in a powerful chemical agent, most often aqua regia. This dissolution step converts the metals into an aqueous solution of metal salts.
Specialized chemical techniques, including solvent extraction and selective precipitation, are then employed to isolate the individual PGMs based on their unique solubility properties. For platinum, the solution’s chemistry is carefully adjusted, often by adding ammonium chloride. This causes the platinum to precipitate out of the solution as a solid salt, ammonium hexachloroplatinate.
This purified platinum salt is filtered from the solution and is then subjected to high-temperature heating, a process called calcination. This thermal treatment drives off the chemical components, leaving behind a highly pure platinum metal powder or sponge. Following a final melt and casting, the product achieves a purity of 99.95% or greater, ready for commercial application.
Platinum Recovery Through Recycling
Modern platinum production is supplemented by secondary sources, which helps meet global demand. Recycling provides approximately 25% of the total annual platinum supply, making it an established part of the industry.
The largest source for recycled platinum is spent automotive catalytic converters. These devices contain recoverable amounts of PGMs. Other sources of secondary platinum include discarded jewelry and various forms of electronic waste.
The recovery process for this scrap material utilizes adapted versions of the same chemical and thermal techniques used for primary ore. High recovery rates, often exceeding 90% from catalytic converters, ensure that the metal is kept in circulation. This circular supply stream is growing in importance due to the metal’s scarcity and its necessity in new technologies, such as hydrogen fuel cells.