SBIR Phase I: Sustainable Rare Earth Element Production from Coal Combustion Byproducts

The broader impact/commercial potential of this Phase I Small Business Innovation Research (SBIR) project is to enable rare earth element (REE) production without mining, by harvesting REEs from coal combustion byproducts, namely coal fly ash. The U.S. produces over 100 million metric tons of coal fly ash each year through burning coal for power and has more than two billion metric tons in storage ponds across the country, estimated to contain up to 100 years’ worth of U.S. demand of REEs. What is missing is a sustainable, scalable, and economic method of separation. REEs play critical roles in many different technologies, ranging from national defense applications to manufacturing and consumer electronics, to healthcare treatments, and much more. One particularly important industry is clean tech, where REEs are used in high-performance wind turbines and electric vehicles. Currently, the U.S. lacks a stable domestic supply of REEs and is reliant on mining efforts in foreign nations that lack similar labor and environmental protections. This dependence is a strategic vulnerability. Harvesting REEs from coal ash would build a sustainable, diverse, and resilient supply chain of materials needed to support the clean energy transition, as well as create new jobs and provide utilities with an economic pathway to better utilize ash and empty existing ash ponds. This SBIR Phase I project will optimize a novel ionic-liquid-based recovery process to harvest rare earth elements (REEs) from coal fly ash. The ionic liquid in question has a high binding affinity for REEs and additionally displays unique thermomorphic behavior: upon heating, water and the ionic liquid form a single liquid phase, and REEs are leached from coal fly ash via a proton-exchange mechanism. Upon cooling, the water and IL separate, and leached elements partition between the two phases. The recovery strategy exploits this behavior in a new method that represents a breakthrough technology: the ionic liquid can extract the REEs directly from the solid ash without the need for digestion and separate the REEs from bulk elements. This dramatically lowers chemical consumption and waste generation and simplifies costly downstream processing. In Phase I of the project, efforts are focused on improving REE concentration in the IL phase, developing new processes for purifying REEs from ionic liquid concentrate, and validating the process for a variety of coal ash samples. The output of this project is expected to be comprehensively tested and validated recovery process ready for scaling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.