Distribution of rare earth elements in coal combustion fly ash, determined by SHRIMP-RG ion microprobe

Allan Kolker; Clint Scott; James C. Hower; Jorge A. Vazquez; Christina L. Lopano; Shifeng Dai

doi:10.1016/j.coal.2017.10.002

Distribution of rare earth elements in coal combustion fly ash, determined by SHRIMP-RG ion microprobe

Allan Kolker
, Clint Scott
, James C. Hower
, Jorge A. Vazquez
, Christina L. Lopano
, Shifeng Dai

Earth and Environmental Sciences

Research output: Contribution to journal › Article › peer-review

247 Scopus citations

Abstract

During coal combustion for electric power generation, rare earth elements (REE) are strongly retained in the ash fraction leading to significant enrichment compared to the REE content of the respective feed coals. Knowing how the REE are distributed in coal ash is essential to devising effective approaches for REE extraction from this potential resource. To better understand the distribution of REE in coal ash, we used the Stanford-USGS SHRIMP-RG ion microprobe to determine grain-scale REE partitioning in a suite of 19 U.S. and international coal fly ash samples. SHRIMP-RG microanalysis used a nominal spot size of 15 μm and an oxygen negative-ion primary beam. NIST multi-element glass standards SRM 611 and SRM 613 were used for REE calibration. Prior to SHRIMP-RG analysis, samples were characterized by backscattered electron imaging and wavelength-dispersive elemental mapping to delineate constituents of interest for REE microanalysis. Results confirm the occurrence of REE in aluminosilicate glasses consistent with previous results that showed a strong positive correlation between Al and REE content in a larger group of U.S. and international coal fly ash samples. Among these glasses, aluminosilicates consisting of Al and Si and lacking other major constituents tend to have REE contents similar to, or slightly lower than the bulk sample REE content, whereas Ca- and/or Fe-enriched aluminosilicate glasses are similar to, or more REE-enriched than the bulk sample. Co-occurring quartz and/or high-silica glass is almost always the most REE depleted fly ash constituent, having much lower REE contents than the aluminosilicate glasses. Fe-oxide magnetospheres have REE content with relative proportions of light (LREE) to heavy (HREE) rare earths that are more variable than in the aluminosilicate glasses. Results suggest that extraction of REE from the aluminosilicate glass fraction in coal ash will yield a significant portion of the REE present and therefore, this fraction should be targeted in ongoing efforts to recover REE from coal fly ash.

Original language	English
Pages (from-to)	1-10
Number of pages	10
Journal	International Journal of Coal Geology
Volume	184
DOIs	https://doi.org/10.1016/j.coal.2017.10.002
State	Published - Nov 1 2017

Bibliographical note

Publisher Copyright:
© 2017

Funding

This study was funded by the USGS Energy Resources Program as part of the USGS Geochemistry of Energy Fuels project. Acquisition of SHRIMP-RG data was supported by a Technical Assistance Agreement between the USGS and the University of Kentucky, with funding from U.S. Department of Energy contract DE-FE0027167 . Samples 77 (A002), 78 (A003), 345, and 357 were provided for study by the U.S. Department of Energy, National Energy Technology Laboratory, under a Memorandum of Agreement between USGS and NETL. Collection of the Jungar ash samples and their bulk analysis was supported by a grant from the National Science Foundation of China (no. 41420104001 ). The authors thank Brett Valentine and Ryan McAleer of the USGS for their assistance with the Reston SEM and microprobe, respectively, and Matt Coble of Stanford University for helping with sample preparation and operation of the SHRIMP-RG. The comments of Mark Engle (USGS) and three Journal reviewers helped improve the manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Funders	Funder number
Michigan State University-U.S. Department of Energy (MSU-DOE) Plant Research Laboratory	DE-FE0027167
U.S. Geological Survey
University of Kentucky
National Natural Science Foundation of China (NSFC)	41420104001

ASJC Scopus subject areas

Fuel Technology
Geology
Economic Geology
Stratigraphy

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Cite this

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title = "Distribution of rare earth elements in coal combustion fly ash, determined by SHRIMP-RG ion microprobe",

abstract = "During coal combustion for electric power generation, rare earth elements (REE) are strongly retained in the ash fraction leading to significant enrichment compared to the REE content of the respective feed coals. Knowing how the REE are distributed in coal ash is essential to devising effective approaches for REE extraction from this potential resource. To better understand the distribution of REE in coal ash, we used the Stanford-USGS SHRIMP-RG ion microprobe to determine grain-scale REE partitioning in a suite of 19 U.S. and international coal fly ash samples. SHRIMP-RG microanalysis used a nominal spot size of 15 μm and an oxygen negative-ion primary beam. NIST multi-element glass standards SRM 611 and SRM 613 were used for REE calibration. Prior to SHRIMP-RG analysis, samples were characterized by backscattered electron imaging and wavelength-dispersive elemental mapping to delineate constituents of interest for REE microanalysis. Results confirm the occurrence of REE in aluminosilicate glasses consistent with previous results that showed a strong positive correlation between Al and REE content in a larger group of U.S. and international coal fly ash samples. Among these glasses, aluminosilicates consisting of Al and Si and lacking other major constituents tend to have REE contents similar to, or slightly lower than the bulk sample REE content, whereas Ca- and/or Fe-enriched aluminosilicate glasses are similar to, or more REE-enriched than the bulk sample. Co-occurring quartz and/or high-silica glass is almost always the most REE depleted fly ash constituent, having much lower REE contents than the aluminosilicate glasses. Fe-oxide magnetospheres have REE content with relative proportions of light (LREE) to heavy (HREE) rare earths that are more variable than in the aluminosilicate glasses. Results suggest that extraction of REE from the aluminosilicate glass fraction in coal ash will yield a significant portion of the REE present and therefore, this fraction should be targeted in ongoing efforts to recover REE from coal fly ash.",

author = "Allan Kolker and Clint Scott and Hower, \{James C.\} and Vazquez, \{Jorge A.\} and Lopano, \{Christina L.\} and Shifeng Dai",

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doi = "10.1016/j.coal.2017.10.002",

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AU - Kolker, Allan

AU - Scott, Clint

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AU - Vazquez, Jorge A.

AU - Lopano, Christina L.

AU - Dai, Shifeng

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AB - During coal combustion for electric power generation, rare earth elements (REE) are strongly retained in the ash fraction leading to significant enrichment compared to the REE content of the respective feed coals. Knowing how the REE are distributed in coal ash is essential to devising effective approaches for REE extraction from this potential resource. To better understand the distribution of REE in coal ash, we used the Stanford-USGS SHRIMP-RG ion microprobe to determine grain-scale REE partitioning in a suite of 19 U.S. and international coal fly ash samples. SHRIMP-RG microanalysis used a nominal spot size of 15 μm and an oxygen negative-ion primary beam. NIST multi-element glass standards SRM 611 and SRM 613 were used for REE calibration. Prior to SHRIMP-RG analysis, samples were characterized by backscattered electron imaging and wavelength-dispersive elemental mapping to delineate constituents of interest for REE microanalysis. Results confirm the occurrence of REE in aluminosilicate glasses consistent with previous results that showed a strong positive correlation between Al and REE content in a larger group of U.S. and international coal fly ash samples. Among these glasses, aluminosilicates consisting of Al and Si and lacking other major constituents tend to have REE contents similar to, or slightly lower than the bulk sample REE content, whereas Ca- and/or Fe-enriched aluminosilicate glasses are similar to, or more REE-enriched than the bulk sample. Co-occurring quartz and/or high-silica glass is almost always the most REE depleted fly ash constituent, having much lower REE contents than the aluminosilicate glasses. Fe-oxide magnetospheres have REE content with relative proportions of light (LREE) to heavy (HREE) rare earths that are more variable than in the aluminosilicate glasses. Results suggest that extraction of REE from the aluminosilicate glass fraction in coal ash will yield a significant portion of the REE present and therefore, this fraction should be targeted in ongoing efforts to recover REE from coal fly ash.

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Distribution of rare earth elements in coal combustion fly ash, determined by SHRIMP-RG ion microprobe

Abstract

Bibliographical note

Funding

ASJC Scopus subject areas

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