US may look to coal for rare earth

New mineral processing techniques in the US could see it challenge the current Chinese hold on global rare earth minerals.

Research by scientists at Penn State and the US Department of Energy has reportedly uncovered a new method to extract rare earths from coal byproducts.

"We have known for many decades that rare-earth elements are found in coal seams and near other mineral veins," Sarma Pisupati, professor of energy and mineral engineering at Penn State, said. 

"However, it was costly to extract the materials and there was relatively low demand until recently. Today, we rely on rare-earth elements for the production of many necessary and also luxury items, including computers, smart phones, rechargeable batteries, electric vehicles, magnets and chemical catalysts. We wanted to take a fresh look at the feasibility of extracting REEs from coal because it is so abundant in the U.S."

The new research comes as new studies predict a growth of 14 per cent for the rare earths market over the next five years.

The Penn State team investigated a process called ion exchange that could remove REEs in a safer manner compared to previous processes such as roasting, which required harsh concentrated acids.

Ion exchange involves the washing of the coal with a solution that releases REEs bound to coal.

"Essentially, REEs are sticking to the surface of molecules found in coal, and we use a special solution to pluck them out," he said.

"We experimented with many solvents to find one that is both inexpensive and environmentally friendly."

To date ammonium sulphate has been used as part of the solution.

"We were able to very easily extract 0.5 per cent of REEs in this preliminary study using a basic ion exchange method in the lab," Pisupati said.

“We are confident that we can increase that to 2 per cent through advanced ion exchange methods."

The researchers used discarded or uneconomical coal in their studies, providing a potential new revenue stream for coal miners.

“Often the highest concentration [of rare earth elements] is found in the poorest quality coal,” Pisupati explained.

“You find some REEs in the coal itself, but the highest concentration is in what we call the coal shale, or the top layer of a coal seam. Knowing this, we can further target our operations to be more efficient," he said.

The researchers are now working with a number of US coal miners to explore the commercial viability of REE extraction on site.


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