Platinum group metals (PGM), comprising mainly platinum, palladium, rhodium, iridium, osmium and ruthenium, are of great interest to the mineral industry, due to their unique physical and chemical properties and wide range of applications. These metals are non-ferrous and have a very high melting point. They are often found as alloys with other metals, including gold, silver, copper, tin and lead.
Platinum group metals are primarily extracted from ore deposits and are then purified, concentrated and processed into finished products for use. The most common method for their extraction involves using specific separation and concentration technologies such as gravity and flotation.
The first step in the process of recovering platinum group metals is mineral identification and ore characterization. Mineral identification is a process in which samples of ore are assessed to determine their mineral content and potential for recovery. Ore characterization is then performed to determine the chemical, physical and metallurgical properties of the ore deposit. This data is used in the subsequent stages of mineral extraction.
Once the ore has been properly identified and characterized, it is then necessary to prepare it for subsequent stages of recovery while preserving the metal content at an acceptable level. This can be done through a process known as milling. During the milling process, ore particles are broken down into smaller sizes and the metal content is released. This process can also involve crushing and grinding the ore.
The following stage is gravity concentration. This process makes use of differences in specific gravity between the ore particles and the metals of interest. During this process, the denser particles containing the metal of interest are separated from the lighter particles and the gravity concentrate or “concentrate” is collected.
The next step is flotation. This process involves the use of chemicals, such as anionic or cationic surfactants, which help to separate the metal of interest from the waste minerals. The flotation process usually involves aeration and mixing of the ore in a flotation cell, which is then subjected to an electro-chemical field. This results in the desired compounds being attracted to the surface of the bubble or froth formed by the aeration, and the air bubbles themselves carrying them up to the surface.
The final step in the process of extracting platinum group metals is smelting and refining. Smelting involves melting the concentrate in a furnace and then separating the metals from the slag, which is composed of remaining silicates. Refining is then used to remove any remaining impurities.
These methods can be used to extract most metals found in nature. However, the process of recovering platinum group metals is more complicated, due to the fact that they are often found in very small concentrations. As such, it is often necessary to use more sophisticated methods such as electrochemical, chemical and biological processes. In some cases, it is also necessary to separate the metals using sophisticated spectroscopy techniques.
Overall, the process for extracting platinum group metals involves the combination of several techniques, such as mineral identification and ore characterization, milling, gravity concentration, flotation and smelting and refining. Depending on the ore deposit and the characteristics of the minerals, the process can vary from simple to complex. In addition, the final quality of the refined product is often very dependent on the purity of the concentrate.
