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Title: Differences in bulk and microscale yttrium speciation in coal combustion fly ash

Abstract

Coal combustion ash is a promising alternative source of rare earth elements (REE; herein defined as the 14 stable lanthanides, yttrium, and scandium). Efforts to extract REE from coal ash will depend heavily on the location and speciation of these elements in the ash. This study sought to identify the major chemical forms of yttrium (Y), as a representative REE in coal fly ash samples selected from major coal sources in the United States. Y speciation was evaluated using both bulk scale analyses (sequential extractions, Y K-edge X-ray absorption near-edge spectroscopy – XANES) and complementary analyses at the micron scale (micro-focus X-ray fluorescence and micro-XANES). Sequential selective extractions revealed that the REE were primarily in the residual (unextracted fraction) of coal fly ash samples. Extraction patterns for yttrium resembled those of the lanthanides, indicating that these elements were collectively dispersed throughout the aluminosilicate glass in fly ash. Bulk XANES analysis indicated that Y coordination states resembled a combination of Y-oxides, Y-carbonate, and Y-doped glass, regardless of ash origin. However, in the microprobe analysis, we observed “hotspots” of Y (~10–50 μm) in some samples that included different Y forms (e.g., Y-phosphate) not observed in bulk measurements. Overall, this study demonstrated thatmore » yttrium (and potentially other REEs) are entrained in the glass phase of fly ash and that microscale investigations of individual high-REE regions in fly ash samples do not necessarily capture the dominant speciation.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Duke Univ., Durham, NC (United States). Department of Civil and Environmental Engineering
  2. Aix Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence (France)
  3. Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research
Publication Date:
Research Org.:
Duke Univ., Durham, NC (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1474753
Alternate Identifier(s):
OSTI ID: 1483484
Grant/Contract Number:  
FE0026952
Resource Type:
Published Article
Journal Name:
Environmental Science: Processes & Impacts
Additional Journal Information:
Journal Volume: 20; Journal Issue: 10; Journal ID: ISSN 2050-7887
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Taggart, Ross K., Rivera, Nelson A., Levard, Clément, Ambrosi, Jean-Paul, Borschneck, Daniel, Hower, James C., and Hsu-Kim, Heileen. Differences in bulk and microscale yttrium speciation in coal combustion fly ash. United States: N. p., 2018. Web. doi:10.1039/c8em00264a.
Taggart, Ross K., Rivera, Nelson A., Levard, Clément, Ambrosi, Jean-Paul, Borschneck, Daniel, Hower, James C., & Hsu-Kim, Heileen. Differences in bulk and microscale yttrium speciation in coal combustion fly ash. United States. doi:10.1039/c8em00264a.
Taggart, Ross K., Rivera, Nelson A., Levard, Clément, Ambrosi, Jean-Paul, Borschneck, Daniel, Hower, James C., and Hsu-Kim, Heileen. Fri . "Differences in bulk and microscale yttrium speciation in coal combustion fly ash". United States. doi:10.1039/c8em00264a.
@article{osti_1474753,
title = {Differences in bulk and microscale yttrium speciation in coal combustion fly ash},
author = {Taggart, Ross K. and Rivera, Nelson A. and Levard, Clément and Ambrosi, Jean-Paul and Borschneck, Daniel and Hower, James C. and Hsu-Kim, Heileen},
abstractNote = {Coal combustion ash is a promising alternative source of rare earth elements (REE; herein defined as the 14 stable lanthanides, yttrium, and scandium). Efforts to extract REE from coal ash will depend heavily on the location and speciation of these elements in the ash. This study sought to identify the major chemical forms of yttrium (Y), as a representative REE in coal fly ash samples selected from major coal sources in the United States. Y speciation was evaluated using both bulk scale analyses (sequential extractions, Y K-edge X-ray absorption near-edge spectroscopy – XANES) and complementary analyses at the micron scale (micro-focus X-ray fluorescence and micro-XANES). Sequential selective extractions revealed that the REE were primarily in the residual (unextracted fraction) of coal fly ash samples. Extraction patterns for yttrium resembled those of the lanthanides, indicating that these elements were collectively dispersed throughout the aluminosilicate glass in fly ash. Bulk XANES analysis indicated that Y coordination states resembled a combination of Y-oxides, Y-carbonate, and Y-doped glass, regardless of ash origin. However, in the microprobe analysis, we observed “hotspots” of Y (~10–50 μm) in some samples that included different Y forms (e.g., Y-phosphate) not observed in bulk measurements. Overall, this study demonstrated that yttrium (and potentially other REEs) are entrained in the glass phase of fly ash and that microscale investigations of individual high-REE regions in fly ash samples do not necessarily capture the dominant speciation.},
doi = {10.1039/c8em00264a},
journal = {Environmental Science: Processes & Impacts},
number = 10,
volume = 20,
place = {United States},
year = {2018},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1039/c8em00264a

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