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Minerals
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Characterization of Rare Earth Elements and Critical Minerals in Geologic...
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Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Exploration Methods and Applications".

Deadline for manuscript submissions: closed (24 March 2023) | Viewed by 8719

Special Issue Editors

Dr. Scott N. Montross

E-Mail Website
Guest Editor
National Energy Technology Laboratory, Albany, OR 97321, USA
Interests: geochemistry; sedimentary systems; chemical weathering; critical materials; rare earth elements; coal; coal utilization byproducts; mining; energy
Dr. Bruce Folkedahl

E-Mail Website
Guest Editor
Critical Materials, EERC, University of North Dakota, Grand Forks, ND 58202, USA
Interests: combustion; gasification; electricity generation; ash deposition; fouling; conversion of biomass feedstocks to fuels; value-added products
Dr. Jonathan Yang

E-Mail Website
Guest Editor
Leidos, National Energy Technology Laboratory, Albany, OR 97321, USA
Interests: quantitative analysis; electron microscopy; separations chemistry; mineral processing; standardization

Special Issue Information

Dear Colleagues,

On behalf of Minerals, we invite you to contribute an original research article to a Special Issue on the characterization and assessment of rare earth elements and critical minerals in geologic materials, including but not limited to coal, coal byproducts, and igneous and sedimentary host rock. Currently, there is a significant gap globally in our understanding of the spatial occurrence and extent of REE and CM resources in coal, sedimentary/igneous host rocks, and waste materials. The gap is due to a lack of adequate and well-distributed characterization and quantitative assessment of the resource in domestic materials. In addition, the type of sampling and characterization performed to date has generally lacked the resolution and approach required to constrain both the geologic and geographic heterogeneities typical of subsurface mineral resources. Sedimentary basins contain valuable REE deposits, yet the limited data—especially in domestic coal-related strata—suggest that most occurrences are low “subeconomic” concentrations. Moreover, at present there is no method for systematically assessing potential REE sedimentary occurrences. The unpredictability of REE/CM resources is partly due to the lack of quantified REE/CM spatial resource trends and the exploration methods tailored to these resources. Thus, there is an immediate need for systematic characterization and assessment approaches that incorporate knowledge of the host materials, geological variations, and the occurrence of REEs and critical minerals in geologic systems.

Dr. Scott N. Montross
Dr. Bruce C. Folkedahl
Dr. Jonathan Yang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • geologic materials
  • coal byproducts
  • microstructure
  • microanalysis
  • rare earth elements
  • critical minerals
  • characterization

Published Papers (5 papers)

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Research

26 pages, 6701 KiB  
Article
Round-Robin Interlaboratory Study on Rare-Earth Elements in U.S.-Based Geologic Materials
by Bruce Folkedahl, Carolyn Nyberg, Saptashati Biswas and Xuefei Zhang
Minerals 2023, 13(7), 944; https://doi.org/10.3390/min13070944 - 14 Jul 2023
Cited by 3 | Viewed by 694
Abstract
In a study funded by the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL), the University of North Dakota (UND) Energy and Environmental Research Center (EERC) performed a first-of-its-kind round-robin interlaboratory study (RRIS) to determine lab-to-lab and method-to-method variability in analyzing [...] Read more.
In a study funded by the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL), the University of North Dakota (UND) Energy and Environmental Research Center (EERC) performed a first-of-its-kind round-robin interlaboratory study (RRIS) to determine lab-to-lab and method-to-method variability in analyzing the rare earth element (REE) content of domestic resources. Analyses of REEs on eleven different materials were accomplished by the laboratories using four different procedures: ASTM D6357 (Procedure A), ASTM D4503 (Procedure B), an alternate in-house procedure for digestion and REE analysis (Procedure C), and neutron activation analysis (NAA). The results of the RRIS suggest that NAA is the most accurate and reliable method for many of the REEs in these types of materials; however, the method is limited in that it is able to determining only ten of the sixteen REEs. Five of the seven labs reporting data for Procedure A and three of the five labs reporting for Procedure B showed excellent performance in terms of repeatability, reproducibility, agreement with NAA, and SRM recoveries based on AOAC International guidelines on method performance. This indicates that when strictly followed these methods are suitable for REE determination in most materials, although are subject to the overall capabilities and experience of individual laboratories. Full article
(This article belongs to the Special Issue Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials)
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17 pages, 2875 KiB  
Article
Rare Earth Element (REE) and Critical Mineral Fractions of Central Appalachian Coal-Related Strata Determined by 7-Step Sequential Extraction
by Sophia Bauer, Jonathan Yang, Mengling Stuckman and Circe Verba
Minerals 2022, 12(11), 1350; https://doi.org/10.3390/min12111350 - 25 Oct 2022
Cited by 3 | Viewed by 2182
Abstract
Rare earth elements (REEs) and critical minerals (CMs) are used in many modern industries, including the automotive sector, generation and storage, clean energy, and defense. The demand for REEs is increasing, and the REE supply chain is unpredictable. The US has driven to [...] Read more.
Rare earth elements (REEs) and critical minerals (CMs) are used in many modern industries, including the automotive sector, generation and storage, clean energy, and defense. The demand for REEs is increasing, and the REE supply chain is unpredictable. The US has driven to assess non-conventional sources of REE (such as coal underclay) to identify domestic resources to stabilize this uncertainty in supply. Knowledge of the minerology, distribution, and modes of occurrence of REEs is integral to the assessment of non-conventional sources. Additionally, extraction techniques can be optimized and targeted when REE distribution in different solid fractions from source material is understood. In this study, four bituminous coal-related samples associated with the Lower and Middle Kittanning coal seams in the Appalachian Basin (US) underwent a seven-step sequential extraction procedure, primarily targeting the water-soluble, exchangeable, acid soluble, mildly reducible, moderately reducible, strongly reducible, and oxidizable fractions. The REE and other elements of interest from each extraction step were analyzed, and the percentages of element extracted from raw solids were calculated. REEs extracted from the total seven steps were reported as the extractable fraction, whereas the fractions in the residual solids were reported as the non-extractable fraction. Less than 6% of REE were extracted from three samples. Twenty-one percent of REE was extracted from the fourth sample, mainly from the steps targeting oxidizable and exchangeable phases. Co-extraction of critical metals (Co, Ni, Cu, and Zn) occurred during the oxidizable, exchangeable, acid soluble, and water-soluble steps for the four samples. In the extracted fractions, the four samples all exhibited a middle and heavy REE enrichment relative to light REE. The mobility of major cation (e.g., Ca, Fe, and P) and REE is associated with exchangeable, oxidizable, and acid soluble fractions. Non-extractable REE is likely held in refractory apatitic phases, and/or primary REE-phosphates (e.g., monazite and xenotime). Full article
(This article belongs to the Special Issue Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials)
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15 pages, 3387 KiB  
Article
On a Unified Core Characterization Methodology to Support the Systematic Assessment of Rare Earth Elements and Critical Minerals Bearing Unconventional Carbon Ores and Sedimentary Strata
by Scott N. Montross, Davin Bagdonas, Thomas Paronish, Andrew Bean, Andrew Gordon, C. Gabriel Creason, Burt Thomas, Erin Phillips, James Britton, Scott Quillian and Kelly Rose
Minerals 2022, 12(9), 1159; https://doi.org/10.3390/min12091159 - 14 Sep 2022
Cited by 2 | Viewed by 2262
Abstract
A significant gap exists in our understanding and ability to predict the spatial occurrence and extent of rare earth elements (REE) and certain critical minerals (CM) in sedimentary strata. This is largely due to a lack of existing, systematic, and well-distributed REE and [...] Read more.
A significant gap exists in our understanding and ability to predict the spatial occurrence and extent of rare earth elements (REE) and certain critical minerals (CM) in sedimentary strata. This is largely due to a lack of existing, systematic, and well-distributed REE and CM samples and analyses in United States sedimentary basins. In addition, the type of sampling and characterization performed to date has generally lacked the resolution and approach required to constrain geologic and geographic heterogeneities typical of subsurface, mineral resources. Here, we describe a robust and systematic method for collecting core scale characterization data that can be applied to studies on the contextual and spatial attributes, the geologic history, and lithostratigraphy of sedimentary basins. The methods were developed using drilled cores from coal bearing sedimentary strata in the Powder River Basin, Wyoming (PRB). The goal of this effort is to create a unified core characterization methodology to guide systematic collection of key data to achieve a foundation of spatially and geologically constrained REEs and CMs. This guidance covers a range of measurement types and methods that are each useful either individually or in combination to support characterization and delineation of REE and CM occurrences. The methods herein, whether used in part or in full, establish a framework to guide consistent acquisition of geological, geochemical, and geospatial datasets that are key to assessing and validating REE and CM occurrences from geologic sources to support future exploration, assessment, and techno-economic related models and analyses. Full article
(This article belongs to the Special Issue Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials)
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14 pages, 1481 KiB  
Article
Coal Feed-Dependent Variation in Fly Ash Chemistry in a Single Pulverized-Combustion Unit
by James C. Hower, John G. Groppo, Shelley D. Hopps, Tonya D. Morgan, Heileen Hsu-Kim and Ross K. Taggart
Minerals 2022, 12(9), 1071; https://doi.org/10.3390/min12091071 - 24 Aug 2022
Cited by 3 | Viewed by 1463
Abstract
Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal [...] Read more.
Four suites of fly ash, all generated at the same power plant, were selected for the study of the distribution of rare earth elements (REE). The fly ashes represented two runs of single-seam/single-mine coals and two runs of run-of-mine coals representing several coal seams from several mines. Plots of the upper continental crust-normalized REE, other parameters derived from the normalization, and the principal components analysis of the derived REE parameters (including the sum of the lanthanides plus yttrium and the ratio of the light to heavy REE) all demonstrated that the relatively rare earth-rich Fire Clay coal-derived fly ashes have a different REE distribution, with a greater concentration of REE with a relative dominance of the heavy REE, than the other fly ashes. Particularly with the Fire Clay coal-derived fly ashes, there is a systematic partitioning of the overall amount and distribution of the REE in the passage from the mechanical fly ash collection through to the last row of the electrostatic precipitator hoppers. Full article
(This article belongs to the Special Issue Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials)
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18 pages, 13946 KiB  
Article
High-Resolution Transmission Electron Microscopy Study of a Powder River Basin Coal-Derived Fly Ash
by James C. Hower, Debora Berti, Christopher R. Winkler, Dali Qian and Nicolas J. Briot
Minerals 2022, 12(8), 975; https://doi.org/10.3390/min12080975 - 30 Jul 2022
Cited by 6 | Viewed by 1515
Abstract
Examination of a fly ash derived from the combustion of a low-S, subbituminous Powder River Basin coal by Scanning Electron Microscopy (SEM) and High-resolution Transmission Electron Microscopy (HRTEM), both supplemented by Energy-dispersive X-ray spectroscopy (EDS), showed that the fly ashes were dominated by [...] Read more.
Examination of a fly ash derived from the combustion of a low-S, subbituminous Powder River Basin coal by Scanning Electron Microscopy (SEM) and High-resolution Transmission Electron Microscopy (HRTEM), both supplemented by Energy-dispersive X-ray spectroscopy (EDS), showed that the fly ashes were dominated by amorphous phases, Ca-rich plagioclase feldspars, Mg-rich phases, complex Ca-Mg-Al-Si-Ti-Fe grains, and trace amounts of REE-rich particles. Many of the particles were rimmed by a Ca-S, possibly a sulfate. HRTEM-EDS examination of a REE-rich particle proved it to be a mix of light- and heavy-rare earth minerals mixed with amorphous phases. Full article
(This article belongs to the Special Issue Characterization of Rare Earth Elements and Critical Minerals in Geologic and Engineered Materials)
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