Team from Center for Advanced Separation Technologies Show Improved Methods to Extract and Process Rare Earths

Highlights

• CAST at Virginia Tech researches advanced mineral separation processes, particularly for rare earth elements (REEs) from coal and byproducts.
• Recent study explores extracting heavy rare earth elements (HREEs) from domestic clayey materials, including ion-adsorption clays.
• Researchers demonstrate blunging as a more efficient method than grinding for liberating rare earth minerals from coal.

The Center for Advanced Separation Technologies (opens in a new tab) (CAST) at Virginia Tech is a research hub that collaborates with other universities and industry partners to advance mineral separation processes, particularly for applications in energy and environmental sustainability. Initially funded in part by the Department of Energy (DOE), CAST aims to improve the extraction and processing of minerals, including rare earth elements (REEs), which are critical for technologies like electronics, renewable energy, and defense systems.

One of CAST's key focuses is on recycling rare earth elements from coal and coal byproducts, leveraging innovative processes like hydrophobic-hydrophilic separation (HHS). This approach enables the extraction of REEs from materials often discarded as coal waste. CAST’s projects also explore the use of coal byproducts to generate other high-value materials, such as graphite, which is essential for battery technologies. By developing these advanced separation techniques, CAST supports efforts to reduce U.S. dependence on foreign sources.

The Latest Study

A team of researchers at CAST recently issued a report, uploading to ResearchGate (opens in a new tab), on ways to extract REE from nonconventional sources

Pointing out that out of15 rare earth elements, heavy rare earth elements (HREEs) are of lower concentrations in nature, thereby making them more difficult to extract, and, by the way, also raising their prices.

Today approximately >80% of HREEs are extracted from the ion-adsorption clays (opens in a new tab) (IACs) mined in South China. However, in America Foley et al. (2014) discovered small IAC deposits along the Appalachian Mountains.  Meanwhile investigation into “USGS coal database led to a conclusion that REEs in coal are partitioned mostly to clayey materials (Bryan et al., 2015).”

The researchers from Virginia Tech’s CAST, based on the output of these reports, have developed methods of extracting HREEs from clayey materials from domestic resources with promising results.

For example, in figure 8 in the paper the authors delineate liberation of rare earth minerals by blunging rather than by ultrafine grinding; and in part b) they show a proposed flowsheet for REM recovery by liberation by blunging, two-liquid flotation to obtain REM concentrate and a low-ash dry coal byproduct, followed by activated IEX +Y leaching.

Also shown in the figure for comparison are the liberation results obtained by grinding. The authors demonstrate that blunging was much more efficient than grinding.  Work is continuing to further improve the method of liberating REMs and passivated IACs from coal.