Two high-organic-sulfur Kentucky coals, the eastern Kentucky River Gem coal and the western Kentucky Davis coal, are examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both including elemental analysis by energy-dispersive spectroscopy (EDS). From the SEM–EDS analysis, it is observed that the western Kentucky coal had areas with Pb and Cd in addition to the expected Fe and S and the eastern Kentucky coal had individual Fe–S-rich areas with La and Ni and with Si, Al, Cr, Ni, and Ti. TEM and selected area electron diffraction (SAED) analyses demonstrate that anglesite with a rim of Pb-bearing amorphous Fe-oxide occurs in the western Kentucky coal. Melanterite, an Fe-sulfate, with minor Al, Si, and K EDS peaks, suggests that clay minerals may be in close association with the sulfate, is also detected in the coal. A polycrystalline metal in the eastern Kentucky sample with a composition similar to stainless steel is adjacent to an Al-rich shard. Euhedral pyrite grains surrounded by kaolinite and gibbsite are detected. Overall, it is noted that element associations should not be assumed to be organic just because minerals cannot be seen with optical microscopy or with standard bulk analytical techniques, such as X-ray diffraction (XRD).

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Published in ACS Omega, v. 3, issue 9, p. 12179-12187.

© 2018 American Chemical Society

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

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This work used shared facilities at the Virginia Tech National Center for Earth and Environmental Nanotechnology Infrastructure (NanoEarth), a member of the National Nanotechnology Coordinated Infrastructure (NNCI), supported by the National Science Foundation (NNCI—1542100). This work was also supported by NSF grant CBET-1510861 to the University of Kentucky.

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01632.

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