Ion-adsorption clays (IACs) mined in South China are probably the most important rare earth resource in the world, as they account for &gt;80% of the global supply of heavy rare earth elements (HREEs) that are critical for high-tech manufacturing industries. Recent studies conducted by USGS showed that both the climate and geological conditions in the Central Appalachian Mountains were conducive to forming regolith-hosted ion-adsorption clays, which raised the prospect of extracting REEs from the clayey mineral matter discarded after extracting coal. It happens that ~80% of the mineral matter consists of kaolinite and/or clay-based sedimentary rocks. Many investigators found, however, that the extraction was not as easy as with the IACs mined in China. Based on our investigation, the difficulties may arise from the passivation of the lanthanide ions adsorbed on clay surfaces by the PO43- and Fe3+ ions during coal formation and the significant presence of the residual accessory minerals, e.g., monazite. In this presentation, spectroscopic evidence for the passivation and novel methods of overcoming the problems in environmentally sustainable ways will be discussed.

Extraction of rare earth elements from the clayey materials discarded in the U.S. coal industry

ACS Spring 2022

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