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NETL-Supported Collaboration Develops Flexible Rare Earth Element Extraction Method From Low-Rank Coal Ash
Low rank coal ash after rapid expansion by sCO2 in an attempt to alter surface area.

With support from NETL, researchers from the University of North Dakota (UND) and Pacific Northwest National Laboratory (PNNL) identified unique pathways and pretreatments to extract rare earth elements (REEs) from low-rank coal (LRC) ash in a more economical and environmentally sustainable manner that can be adjusted to meet variable conditions.

LRCs, such as lignites, are one of the most abundant fossil fuel sources in the world.  NETL-supported project with UND and PNNL researchers has shown that the ash from LRCs can be a potentially viable source of REEs.

The research team conducted an extensive characterization effort to understand the form, associations and partitioning of the REEs along with other relevant elements and minerals in the fly ash samples, as well as the ash chemistry, mineralogy and morphology. Understanding these intricacies was a vital step in developing the method for extraction and recovery of the contained LCR REEs.

Using ash samples collected from a combination of full-scale power generation stations and pilot-scale combustion systems employed at UND, the researchers achieved the goal of producing a mixed REE concentrate greater than 2% by weight, a step forward on the road to securing a financially viable domestic market for these vital materials used to manufacture of computer components, cell phones, satellites, defense applications, and renewable energy technologies, among others.

The LRC ash-based method developed by the UND and PNNL offers an advantage in flexibility. The process can be adjusted to adapt to the differing ash chemical and physical properties characteristic of the LRC ash. This is an important trait considering that all ash materials can be different and require specific extraction processes. This research development means different characteristics in varying ashes can be accommodated in REE extraction operations. 

“NETL supports several research projects throughout the nation with the goal of finding affordable ways to obtain the rare earth elements we need to keep our economy going,” said Anthony Zinn, NETL project manager. “The extraction method developed at UND offers a degree of flexibility which may make it attractive for potential users in the future, allowing the economy to grow while also disposing of fly ash from our existing coal-based power plant fleet.”

Furthermore, the researchers determined that if higher levels of REEs were in the initial LRC ash, the process can be economically viable even without further optimization so long as additional high-value metals or critical minerals are recovered as well. They also discovered that a simple water wash pretreatment on the samples can reduce the required amounts of acid for initial REE extraction from lignite ash. Reduced acid use has the bonus of reducing costs and the environmental impact while also improving work site safety.

This development came as part of an NETL-funded cooperative agreement intended to develop a domestic supply chain for REEs, which are vital to the manufacturing of personal electronics, energy infrastructure and defense technologies, among many other high-tech applications.

NETL is a U.S. Department of Energy national laboratory that produces technological solutions for America’s energy challenges. From developing creative innovations and efficient energy systems that make coal more competitive, to advancing technologies that enhance oil and natural gas extraction and transmission processes, 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.