Rare Earth Minerals Mining and Beneficiation
Background
Rare earth minerals (REM) are a strategic natural resource that are essential for many modern technologies, including green energy applications and electronic device manufacturing. Access to a sustainable supply of REM is therefore increasingly important. While rem are found in a range of mineral deposits, mining and beneficiation activities are complex, costly and energy intensive.
Mining Methods
REM mining typically follows two main approaches: open-pit mining and underground mining. Open-pit mining is used for shallow deposits and requires large earth-moving equipment Usually it involves stripping overburden and then blasting ore-bearing rock. The ores produced by open pit mining are then crushed and processed to produce the rare earth concentrate.
Underground mining is used in deeper ore bodies, where it is considered desirable not to disturb overburden or vegetation. The ore is typically accessed by tunneling and advanced to the desired mining level. Drilling and blasting is used to break up and remove waste material before ore is extracted. Underground mining is typically more labor intensive than open-pit mining and, depending on the size of the deposit, may require specialized mining equipment.
Beneficiation
Rem ore beneficiation process is typically complex and often involves a series of stages, including milling, flotation, magnetic separation, leaching, separation and refining.
Milling– The ore usually requires grinding and classification to liberate the rare earths from gangue (non-ore) material. Often wet grinding is used for this purpose.
Flotation – Floatation is typically used to achieve good beneficiation of REM. In this process, air bubbles are injected into a slurry of the ore and are then floated up to the surface, where they can be collected. Depending on the ore type and the desired purity of the resulting products, further processing is sometimes required and hydro-cyclones are often utilized.
Magnetic Separation - This is a physical separation process, which exploits the differences in magnetic properties between the rare earth minerals and gangue (non-ore) material. By employing a powerful magnetic field and an appropriate separation matrix, the desired minerals can be separated from the undesired components.
Leaching – This process involves mixing the ore with a reagent, allowing it to react and then separating the desired products from the remaining material. Hydrochloric or sulfuric acid (or other agents) can be used, and depending on the metals content of the ore different leaching techniques may be required.
Separation and Refining - After the ore has been beneficiated and the desired elements have been separated, the next step is to refine them further. This can involve chemical and physical processes, such as chemical precipitation and electrochemical purification. The end result of this process is the rare earth elements (REE) in a highly purified form.
Conclusion
Mining and beneficiation of rare earth minerals is complex and costly. Initial exploration and identification of suitable deposits is the first step and is followed by ore extraction, crushing and milling. Subsequent beneficiation processes typically involve floatation, magnetic separation, leaching, and refining to produce the desired rare earth elements (REE). With the growing demand for rare earths, companies that successfully extract, beneficiate and refine REM are well positioned to benefit from this trend.
Footnote
1Rare Earth Minerals and Elements. (2018). https://rareearth.com/
