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Title: Trace Uranium Partitioning in a Multiphase Nano-FeOOH System

Abstract

The characterization of trace elements in nanomaterials using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities or dopants affect the properties of the host phase. However, limitations to EXAFS interpretation complicate the analysis of trace concentrations of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio molecular dynamics (AIMD)-informed EXAFS analysis was employed to investigate the immobilization of trace uranium associated with nanophase iron (oxyhydr)oxides, a model system for the geochemical sequestration of radiotoxic contaminants. The reductive transformation of ferrihydrite (Fe(OH)3) to nano-particulate iron oxyhydroxide minerals in the presence of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (a-FeOOH) over lepidocrocite (g-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is supported by atomically resolved transmission electron microscopy. Using this model system, we demonstrate how AIMD-informed EXAFS analysis lifts the strict statistical limitations of traditional shell-by-shell EXAFS modeling, enabling the detailed analysis of the local bonding environment, charge compensation mechanisms, and oxidation states of polyvalent impurities in complex multi-phase nano-systems.

Authors:
ORCiD logo; ; ORCiD logo; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1356488
Report Number(s):
PNNL-SA-123284
Journal ID: ISSN 0013-936X; 49691; 48389; 49383; KC0302060
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 51; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
ab initio molecular dynamics; iron oxides; reductive transformation; actinide chemistry; uranium sequestration; geochemistry; Environmental Molecular Sciences Laboratory

Citation Formats

McBriarty, Martin E., Soltis, Jennifer A., Kerisit, Sebastien, Qafoku, Odeta, Bowden, Mark E., Bylaska, Eric J., De Yoreo, James J., and Ilton, Eugene S.. Trace Uranium Partitioning in a Multiphase Nano-FeOOH System. United States: N. p., 2017. Web. doi:10.1021/acs.est.7b00432.
McBriarty, Martin E., Soltis, Jennifer A., Kerisit, Sebastien, Qafoku, Odeta, Bowden, Mark E., Bylaska, Eric J., De Yoreo, James J., & Ilton, Eugene S.. Trace Uranium Partitioning in a Multiphase Nano-FeOOH System. United States. doi:10.1021/acs.est.7b00432.
McBriarty, Martin E., Soltis, Jennifer A., Kerisit, Sebastien, Qafoku, Odeta, Bowden, Mark E., Bylaska, Eric J., De Yoreo, James J., and Ilton, Eugene S.. Tue . "Trace Uranium Partitioning in a Multiphase Nano-FeOOH System". United States. doi:10.1021/acs.est.7b00432.
@article{osti_1356488,
title = {Trace Uranium Partitioning in a Multiphase Nano-FeOOH System},
author = {McBriarty, Martin E. and Soltis, Jennifer A. and Kerisit, Sebastien and Qafoku, Odeta and Bowden, Mark E. and Bylaska, Eric J. and De Yoreo, James J. and Ilton, Eugene S.},
abstractNote = {The characterization of trace elements in nanomaterials using extended X-ray absorption fine structure (EXAFS) spectroscopy constitutes a first step toward understanding how impurities or dopants affect the properties of the host phase. However, limitations to EXAFS interpretation complicate the analysis of trace concentrations of impurities that are distributed across multiple phases in a heterogeneous system. Ab initio molecular dynamics (AIMD)-informed EXAFS analysis was employed to investigate the immobilization of trace uranium associated with nanophase iron (oxyhydr)oxides, a model system for the geochemical sequestration of radiotoxic contaminants. The reductive transformation of ferrihydrite (Fe(OH)3) to nano-particulate iron oxyhydroxide minerals in the presence of uranyl (UO2)2+(aq) resulted in the preferential incorporation of U into goethite (a-FeOOH) over lepidocrocite (g-FeOOH), even though reaction conditions favored the formation of excess lepidocrocite. This unexpected result is supported by atomically resolved transmission electron microscopy. Using this model system, we demonstrate how AIMD-informed EXAFS analysis lifts the strict statistical limitations of traditional shell-by-shell EXAFS modeling, enabling the detailed analysis of the local bonding environment, charge compensation mechanisms, and oxidation states of polyvalent impurities in complex multi-phase nano-systems.},
doi = {10.1021/acs.est.7b00432},
journal = {Environmental Science and Technology},
number = 9,
volume = 51,
place = {United States},
year = {Tue Apr 11 00:00:00 EDT 2017},
month = {Tue Apr 11 00:00:00 EDT 2017}
}