NETL researchers developed a new process for extracting economically and strategically vital rare earth elements (REE) and critical minerals (CM) from America’s coal fly ash at high quantities and offers several advantages over other available technologies.

Examples of REE include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium. These elements are used in defense technologies, medical equipment, consumer electronics, energy components, vehicle parts and a host of other products that make modern life possible.

However, as China currently controls the supply and prices of almost all the world’s REEs, developing a domestic supply of these resources is critical for economic and national security.

NETL’s patent, “Step-Leaching Process of Rare Earth Elements from Ash Materials Using Mild Inorganic Acids at Ambient Conditions,” was filed in February. The invention details methods to extract REE from select coal combustion fly ashes using mild inorganic acids at ambient temperatures via a three-step mild acid extraction process that results in high levels of extraction, ranging from 80-100%.

“Not only does this invention enable us to meet a critical need for our economy, but it can also incentivize the use of coal ash, thereby transforming today’s waste product into tomorrow’s commodity,” explained NETL research scientist Mengling Stuckman, one of the developers of the patent. “As a bonus, this process can also lead to new employment opportunities in America’s mining communities that were left behind by the natural gas boom, allowing them to once again become valuable players in the global economy by supplying America’s REE needs.”

With the U.S. still generating much of its electricity via coal combustion, there is plenty of ash material from which to draw for REE extraction. For example, about 113 million metric tons of coal combustion products are generated annually, which includes 38 million tons of fly ash and 9 million tons of bottom ash. With median REE concentrations reported in U.S. ash as 481 milligrams per kilogram, it is estimated that a total of 8,910 tons as rare earth oxides (REO) can be generated from all unused fly ash reserve annually in the United States. The annual REO production from fly ash along with bottom ash, if 100% recovered, will have the potential to satisfy 94% of U.S. annual demand.

Furthermore, NETL’s invention operates at ambient temperatures and pressures, reducing operator costs and the environmental footprint, especially when compared to alternative methods of acquiring REE and CM.

NETL is a U.S. Department of Energy (DOE) national laboratory dedicated to advancing the nation's energy future by creating innovative solutions that strengthen the security, affordability and reliability of energy systems and natural resources. With laboratories in Albany, Oregon; Morgantown, West Virginia; and Pittsburgh, Pennsylvania, NETL creates advanced energy technologies that support DOE’s mission while fostering collaborations that will lead to a resilient and abundant energy future for the nation.