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Title: Iron Vacancies Accommodate Uranyl Incorporation into Hematite

Abstract

Radiotoxic uranium contamination in natural systems and nuclear waste containment can be sequestered by incorporation into naturally abundant iron (oxyhydr)oxides such as hematite (-Fe2O3) during mineral growth. The stability and properties of the resulting uranium-doped material depend on the local coordination environment of incorporated uranium. While measurements of uranium coordination have been attempted using extended X-ray absorption fine structure (EXAFS) analysis, traditional shell-by-shell EXAFS fitting yields ambiguous results. We used hybrid functional ab initio molecular dynamics (AIMD) simulations for various defect configurations to generate EXAFS spectra which were fitted to experimental U L3-edge EXAFS for U6+-doped hematite. We discovered that the hematite lattice accommodates a trans-dioxo uranyl-like configuration for U6+ that substitutes for structural Fe3+, which requires two partially protonated Fe vacancies situated at opposing corner-sharing lattice sites. Surprisingly, the best match to experiment included significant proportions of vacancy configurations other than the minimum-energy configuration, pointing to the importance of incorporation mechanisms and kinetics over thermodynamics in determining the state of an impurity incorporated in a host phase under hydrothermal conditions.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1];  [2];  [3];  [1]
  1. BATTELLE (PACIFIC NW LAB)
  2. UNIVERSITY OF MANCHESTER
  3. University of Manchester
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1575417
Report Number(s):
PNNL-SA-131768
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Environmental Science & Technology
Additional Journal Information:
Journal Volume: 52; Journal Issue: 11
Country of Publication:
United States
Language:
English

Citation Formats

McBriarty, Martin E., Kerisit, Sebastien N., Bylaska, Eric J., Shaw, Samuel, Morris, Katherine, and Ilton, Eugene S. Iron Vacancies Accommodate Uranyl Incorporation into Hematite. United States: N. p., 2018. Web. doi:10.1021/acs.est.8b00297.
McBriarty, Martin E., Kerisit, Sebastien N., Bylaska, Eric J., Shaw, Samuel, Morris, Katherine, & Ilton, Eugene S. Iron Vacancies Accommodate Uranyl Incorporation into Hematite. United States. https://doi.org/10.1021/acs.est.8b00297
McBriarty, Martin E., Kerisit, Sebastien N., Bylaska, Eric J., Shaw, Samuel, Morris, Katherine, and Ilton, Eugene S. 2018. "Iron Vacancies Accommodate Uranyl Incorporation into Hematite". United States. https://doi.org/10.1021/acs.est.8b00297.
@article{osti_1575417,
title = {Iron Vacancies Accommodate Uranyl Incorporation into Hematite},
author = {McBriarty, Martin E. and Kerisit, Sebastien N. and Bylaska, Eric J. and Shaw, Samuel and Morris, Katherine and Ilton, Eugene S.},
abstractNote = {Radiotoxic uranium contamination in natural systems and nuclear waste containment can be sequestered by incorporation into naturally abundant iron (oxyhydr)oxides such as hematite (-Fe2O3) during mineral growth. The stability and properties of the resulting uranium-doped material depend on the local coordination environment of incorporated uranium. While measurements of uranium coordination have been attempted using extended X-ray absorption fine structure (EXAFS) analysis, traditional shell-by-shell EXAFS fitting yields ambiguous results. We used hybrid functional ab initio molecular dynamics (AIMD) simulations for various defect configurations to generate EXAFS spectra which were fitted to experimental U L3-edge EXAFS for U6+-doped hematite. We discovered that the hematite lattice accommodates a trans-dioxo uranyl-like configuration for U6+ that substitutes for structural Fe3+, which requires two partially protonated Fe vacancies situated at opposing corner-sharing lattice sites. Surprisingly, the best match to experiment included significant proportions of vacancy configurations other than the minimum-energy configuration, pointing to the importance of incorporation mechanisms and kinetics over thermodynamics in determining the state of an impurity incorporated in a host phase under hydrothermal conditions.},
doi = {10.1021/acs.est.8b00297},
url = {https://www.osti.gov/biblio/1575417}, journal = {Environmental Science & Technology},
number = 11,
volume = 52,
place = {United States},
year = {2018},
month = {6}
}

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Works referencing / citing this record:

Can mineral growth by oriented attachment lead to incorporation of uranium( vi ) into the structure of goethite?
journal, January 2019


Crystal Phase Distribution and Ferroelectricity in Ultrathin HfO 2 –ZrO 2 Bilayers
journal, September 2019


Crystal Phase Distribution and Ferroelectricity in Ultrathin HfO 2 –ZrO 2 Bilayers
journal, September 2019