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Coal production byproducts aid rare earth element recovery

Ohio State University researchers continue to find ways to sustainably reclaim abandoned coal mine lands, this time recovering rare earth elements considered to be critical components in the production of renewable energy hardware, electric vehicles, health care and military equipment, and consumer electronic products.

Demand for these rare earth elements, including scandium, yttrium and a group of 15 lanthanides, is projected to grow more than 5 percent annually in the next 25 years, but China’s dominance of their production and restricted exports causes instability for the global market.

Ohio State researchers are developing a process using coal production byproducts called stabilized flue gas desulfurization (sFGD) material to recover these rare earths from acid mine drainage at coal mines.

“When surface water or groundwater come in contact with land containing sulfide minerals exposed by coal mining, the presence of ferric iron and/or oxygen can accelerate the oxidation of those sulfide minerals and produce sulfuric acid,” Tarunjit Butalia, research associate professor of civil, environmental and geodetic engineering. “The process promotes the weathering of rare earth element-bearing rocks and minerals. The concentrations of these rare earth elements can be orders of magnitude higher in acid mine drainage compared to that in average river water and seawater.”

The researchers will develop an integrated process that first uses sFGD material as a sorbent to separate rare earth elements from acid mine drainage and then applies a sequential extraction procedure to concentrate the rare earth-enriched material to produce a rare earth feedstock that can be further economically refined. (Photo: bench study)

In this project, the research team will validate the effectiveness and feasibility of the integrated rare earth recovery/concentrating process. The interactions between rare earth elements and the active constituents in the sFGD material will be investigated using advance analytical techniques, including synchrotron-based X-ray method, to maximize the production of rare earth feedstock. In addition, the associated economic and environmental benefits will be quantified. In addition to laboratory works, the research team will also carry out field investigation to identify potential acid mine drainage discharge for next phase pilot-scale study.

CEGE researchers Chin-Min Cheng (top left), Tarunjit Butalia (top right), Jeffrey Bielicki (bottom left) and John Lenhart (bottom right)The recovery and concentration process can be integrated with abandoned mine land reclamation to create an approach that can add economic incentives for reclamation; remediate acid mine drainage discharge; provide a long-term, high-volume beneficial use for coal combustion by-products, which otherwise are disposed of in landfills; and eliminate public safety hazards and environmental and ecological threats posed by abandoned mine lands.

The principal investigators of this project are Chin-Min Cheng, Tarunjit Butalia, Jeffrey Bielicki and John Lenhart, all of the Department of Civil, Environmental and Geodetic Engineering.

American Electric Power, Ohio Department of Natural Resources, and Baker Enviro Service Technology are partners in the research, which has received nearly $400,000 in funding from the U.S. Department of Energy.

The research builds upon other work Butalia has done to find ways to use coal combustion products to reclaim mined lands.