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Review

A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials

1
Department of Mining and Minerals Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
2
Department of Mining Engineering, University of Kentucky, Lexington, KY 40506, USA
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(5), 451; https://doi.org/10.3390/min10050451
Received: 22 April 2020 / Revised: 13 May 2020 / Accepted: 14 May 2020 / Published: 17 May 2020
(This article belongs to the Special Issue Leaching of Rare Earth Elements from Various Sources)
Many studies have been published in recent years focusing on the recovery of rare earth elements (REEs) from coal-related materials, including coal, coal refuse, coal mine drainage, and coal combustion byproducts particularly fly ash. The scientific basis and technology development have been supported by coal geologists and extractive metallurgists, and through these efforts, the concept has progressed from feasibility assessment to pilot-scale production over the last five years. Physical beneficiation, acid leaching, ion-exchange leaching, bio-leaching, thermal treatment, alkali treatment, solvent extraction, and other recovery technologies have been evaluated with varying degrees of success depending on the feedstock properties. In general, physical beneficiation can be a suitable low-cost option for preliminary upgrading; however, most studies showed exceedingly low recovery values unless ultrafine grinding was first performed. This finding is largely attributed to the combination of small RE-bearing mineral particle size and complex REE mineralogy in coal-based resources. Alternatively, direct chemical extraction by acid was able to produce moderate recovery values, and the inclusion of leaching additives, alkaline pretreatment, and/or thermal pretreatment considerably improved the process performance. The studies reviewed in this article revealed two major pilot plants where these processes have been successfully deployed along with suitable solution purification technologies to continuously produce high-grade mixed rare earth products (as high as +95%) from coal-based resources. This article presents a systematic review of the recovery methods, testing outcomes, and separation mechanisms that are involved in REE extraction from coal-related materials. The most recent findings regarding the modes of occurrence of REEs in coal-related materials are also included. View Full-Text
Keywords: rare earth elements; recovery; coal; acid mine drainage; coal combustion byproducts rare earth elements; recovery; coal; acid mine drainage; coal combustion byproducts
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MDPI and ACS Style

Zhang, W.; Noble, A.; Yang, X.; Honaker, R. A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials. Minerals 2020, 10, 451. https://doi.org/10.3390/min10050451

AMA Style

Zhang W, Noble A, Yang X, Honaker R. A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials. Minerals. 2020; 10(5):451. https://doi.org/10.3390/min10050451

Chicago/Turabian Style

Zhang, Wencai, Aaron Noble, Xinbo Yang, and Rick Honaker. 2020. "A Comprehensive Review of Rare Earth Elements Recovery from Coal-Related Materials" Minerals 10, no. 5: 451. https://doi.org/10.3390/min10050451

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