1. Mining: Iridium is found in certain types of copper-nickel sulfide ores. These ores are mined from open-pit or underground mines.
2. Concentration: The mined ore undergoes concentration processes, such as froth flotation, to separate the valuable metal-rich minerals from the waste materials.
3. Smelting: The concentrated ore is smelted to produce a molten mixture containing various metals, such as copper, nickel, iron, and precious metals including iridium.
4. Matte Conversion: The molten mixture from the smelting process undergoes further processing to form a copper-nickel matte. This matte contains a higher concentration of the valuable metals.
5. Refining: The copper-nickel matte is refined through a series of steps, including:
- Roasting: The matte is heated in the presence of oxygen to remove sulfur and produce a solid material known as calcine.
- Leaching: The calcine is leached with sulfuric acid or other solvents to dissolve the valuable metals, such as copper and nickel.
- Precipitation: The dissolved metals are precipitated out of the solution as hydroxides or sulfides.
- Electrorefining: This is a process where the precipitated metal compounds undergo electrolytic refining to obtain pure metals like copper, nickel, and precious metals including iridium.
6. Recovery of Iridium:
- The anode slimes, a by-product of the electrolytic refining process, contain various precious metals including iridium.
- These anode slimes undergo a series of chemical and metallurgical treatments to separate and extract iridium.
The extraction of iridium requires careful refining and separation processes due to its relatively low abundance and its presence in combination with other metals in ores.
