Rare earth element associations in the Kentucky State University stoker ash

The Kentucky State University heating plant stoker ash, with over 1000 μg/g Rare earth elements + yttrium (REY), was previously shown to be more resistant to acid-extraction than pulverized-coal fly ashes of similar bulk composition. In this study, the petrology and mineralogy of this stoker ash was...

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Bibliographic Details
Published in:International journal of coal geology 2018-03, Vol.189, p.75-82
Main Authors: Hower, James C., Qian, Dali, Briot, Nicolas J., Henke, Kevin R., Hood, Madison M., Taggart, Ross K., Hsu-Kim, Heileen
Format: Article
Language:English
Subjects:
Appalachian coal
Lanthanides
Nanominerals
Transmission electron microscopy
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Summary:The Kentucky State University heating plant stoker ash, with over 1000 μg/g Rare earth elements + yttrium (REY), was previously shown to be more resistant to acid-extraction than pulverized-coal fly ashes of similar bulk composition. In this study, the petrology and mineralogy of this stoker ash was examined in greater detail as a means to better understand why the REY were relatively inert towards acid extraction. The results showed that this stoker ash is dominated by mullite and quartz/cristobalite with lesser amounts of hematite and magnetite compared to the glass-dominated assemblages of pulverized-coal-combustion fly ashes with similar chemical compositions. On the nanometer to micron scale, La-Ce-Nd-bearing monazite and Ce phosphates (monazite – CePO4 and CeP3O9) are seen to be part of the mineral assemblage. Overall, the results demonstrate that despite the presence of discrete REY-bearing minerals in the sample, their encapsulation within other phases may explain their low extractability.
ISSN:0166-5162
1872-7840
DOI:10.1016/j.coal.2018.02.022