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Securing a domestic source of rare earth elements (REEs) remains a priority for the U.S. Department of Energy (DOE). Thanks to our Nation’s abundant coal resources, a potential opportunity to obtain these elements is within reach.

With support from DOE’s National Energy Technology Laboratory (NETL), the Research Triangle Institute (RTI) is exploring methods to extract, separate, and recover REEs from coal-based resources. As part of an NETL-funded cooperative agreement, the RTI team is testing the efficacy of various approaches to REE recovery and enrichment with a targeted concentrated goal of 2 wt. percent mixed REE from acid mine drainage (AMD) samples.

This means that coal could provide a potential source of vital REEs without the investment required to open a new mine specifically dedicated to their extraction. Existing coal mines could provide domestic supplies of REEs if the extraction methods are refined and the desired purities are reached.

The RTI team assessed several technologies for REE concentration and recovery. Among them was nanofiltration, which uses polymer and ceramic membranes inserted in a tubular structure to filter and extract the valuable elements from AMD effluent streams. In RTI’s experiments, membranes were used to concentrate desirable elements—lanthanum and praseodymium, among others—and remove the bulk of the low-value ions such as sodium, potassium, heavy metals, and divalent metal salts. This filtration enhanced the performance of the final downstream recovery process, achieving maximum recovery retrieval of valuable REEs.

The assessment of nanofiltration showed the technology may be more appropriate for REE recovery in non-iron rich streams. Furthermore, when combined with electrodeposition, membrane nanofiltration showed potential for recovering scandium and cerium, used in aerospace industry components, self-cleaning ovens, and other products.

“Considering the importance of REEs in products ranging from computers to defense applications, it’s imperative to pursue as many opportunities as possible to find stable, domestic sources that can insulate against market volatilities in the global supply chain,” said NETL Project Manager Omer Bakshi. “NETL is committed to exploring a variety of options put forward from our partner organizations, including RTI, as we search for the most feasible solutions.”

As a DOE National Laboratory, NETL produces technological solutions for America’s energy challenges. NETL research is providing breakthroughs and discoveries that support domestic energy initiatives, stimulate a growing economy, and improve the health, safety, and security of all Americans. Highly skilled men and women at NETL’s sites in Albany, Oregon; Anchorage, Alaska; Houston, Texas; Morgantown, West Virginia; and Pittsburgh, Pennsylvania conduct a broad range of research activities that support DOE’s mission to advance the national, economic, and energy security of the United States.