Coal and coal byproducts: A large and developable unconventional resource for critical materials – Rare earth elements

Abstract

Rare earth elements (REEs) are critical materials and provide significant values to national security, energy production, environmental protection and economic growth. The supply of REEs in U.S. solely relies on import as domestic production of REEs was ceased because of the environmental concerns during mining and lack of competitiveness. Nonetheless, unconventional REEs-containing resources, including produced water, acid mine drainage, and coal and coal byproducts (C&CBs) contain significant amounts of REEs. However, the concentrations of REEs in these resources are several orders of magnitude lower than that of REEs ores. Thus, extraction of REEs from these materials is challenging. Here we report REEs extraction with environmentally friendly method that successfully concentrated REEs from 312 ppm in fly ash to 99.4% in the final product. Especially, the five critically important REEs (Dy, Eu, Nd, Tb, and Y) account for up to ∼63% of the total weight of all REEs in the final 99.4%-purity product. Coal fly ash is one of the major solid coal utilization byproducts, representing great potential resources for REEs extraction. Extraction of REEs from these unconventional resources could be the way to secure domestic supply of these critical materials.