Highlights
- Chinese scientists improve rare earth elements recovery from xenotime ore using magnetic separation and flotation techniques.
- The combined process achieved a 51.26% grade concentrate with a 90.47% recovery rate for rare earth elements.
- Magnetic separation and flotation are commonly used to concentrate REEs, typically yielding grades of 50-70% and recovery rates of 60-90%.
Earth scientists from University of Science and Technology Beijing, Baotou Research Institute of Rare Earths and the Baotou Rare Earth R&D Center represented by corresponding author Zhengyao Li and colleagues take on the opportunities and challenges associated with rare earth elements (REE). Exhibiting distinctive spatial structures and physicochemical properties making them indispensable in various high-tech sectors, they are referred to as “vitamins of industry.” Representing a mission-critical class of raw materials for many key and advanced technological applications, Xenotime (opens in a new tab) (YPO4), a significant phosphatic mineral rich in heavy rare earth elements (HREEs), typically associated with granitic rocks, exemplified in the Wolverine rare earth deposit in Australia, largest known rare earth deposit in the Browns Range area of Western Australia. Performing composition analysis points to primary valuable minerals in the deposit are principally xenotime and minor florencite, (opens in a new tab) with quartz and illite as the main gangue (no value) minerals, showing a relatively simple mineral composition. Applying a magnetic separation pre-enrichment test, the Chinese earth scientists increased the grade of rare earth concentrate to 14.29% and the recovery reached 94.48%. Importantly the magnetic separation process by itself could not help the study’s authors deliver a high-grade rare earth concentrate. A process of flotation was introduced for additional purification of the magnetic concentrate. Flotation is a separation process including crushing and grinding the ore, mixing with water and reagents, air injection and bubble formation, separation, and dewatering.
Using both magnetic separation and flotation the authors from both the Beijing area and Inner Mongolia the authors report achieving 51.26% grade rare earth concentrate plus a 90.47% recovery rate.
What does this mean? The process introduced by the Chinese earth scientists supports the efficient recovery of xenotime and florencite leading to marked improvement in industrial potential.
The combination of magnetic separation and flotation is commonly used to concentrate REEs in ores, especially in minerals like bastnaesite, monazite, and xenotime. The grade (purity) and recovery rate (percentage of REEs extracted from the ore) achieved through this process can vary based on the ore type, mineral composition, and processing conditions, but there are some general benchmarks Rare Earth Exchanges reports below.
When looking at grades achieved, for numerous rare earth ores the combined use of magnetic separation and flotation can yield a concentrate with a REE grade of 50-70% or higher.
In cases of high-quality ores and optimized conditions, grades can reach up to 80% or more. However, this often requires additional refining steps after flotation to remove impurities.
A typical recovery rate for REEs in this combined process ranges from 60% to 90%. Importantly, recovery rates depend on ore mineralogy, particle size, and reagent choices in flotation. Some complex ores with intergrown minerals may have lower recovery rates due to incomplete liberation or insufficient separation of non-REE materials.
The approaches studied and reported on by the earth scientists include the two in the table below:
| Process | Summary |
|---|---|
| Magnetic Separation | Initially, magnetic separation is used to remove magnetic impurities and concentrate the rare earth minerals. This step is particularly useful for ores containing ferromagnetic minerals (e.g., iron oxides). |
| Flotation | Following magnetic separation, flotation is applied to further concentrate the REEs by separating them from non-magnetic impurities |
Higher-grade concentrates with greater recovery are possible through process optimization and additional steps like chemical leaching after flotation, which removes remaining impurities, potentially increasing both grade and recovery.
A combined approach of magnetic separation and flotation can typically achieve REE grades of 50-70% with recovery rates of 60-90%, depending on the ore and processing parameters.
This work was financially supported by the Natural Science Foundation (opens in a new tab) of Inner Mongolia of China and the Program of State Key Laboratory of Bayan Obo Rare Earth Resource Researches and Comprehensive Utilization.
Zhengyao Li (opens in a new tab) at University of Science and Technology Beijing, School of Civil and Resource Engineering and State Key Laboratory of High-Efficient Mining and Safety of Metal Mines of Ministry of Education, University of Science and Technology Beijing and colleagues authored this report.
Daniel
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