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Title: The coordination chemistry of Cm III, Am III, and Ac III in nitrate solutions: an actinide L 3-edge EXAFS study

Understanding actinide(III) (An III = Cm III, Am III, Ac III) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, An III speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect – in large part – is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Here in this paper, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized Cm III, Am III, and Ac III using An III L 3-edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO 3) concentration. Our results revealed that actinide aquo ions, An(H 2O) x 3+ (x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for Cm III, Am III, and Ac III), were the dominant species in dilute HNO 3 (0.05 M). In concentrated HNO 3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO 3) 4.1±0.7(H 2O) 5.7±1.3( 1.1±0.2)more » -, Am(NO 3) 3.4±0.7(H 2O) 5.4±0.5( 0.4±0.1) -, and Ac(NO 3) 2.3±1.7(H 2O) 8.3±5.2( 0.7±0.5) + were observed. Data obtained at the intermediate HNO 3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. Here, for all three metals, the intermediate models showed larger contributions from the 0.05 M HNO 3 spectra than from the 16 M HNO 3 spectra. Additionally, these efforts enabled the Cm–NO 3 and Ac–NO 3 distances to be measured for the first time. Moreover, the An III L 3-edge EXAFS results, contribute to the growing body of knowledge associated with Cm III, Am III, and Ac III coordination chemistry, in particular toward advancing understanding of An III solution phase speciation.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [1] ;  [3] ;  [1] ;  [4]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Washington, Seattle, WA (United States). Dept. of Physics
  3. Stanford Univ., CA (United States)
  4. Univ. of Washington, Seattle, WA (United States). Dept. of Physics
Publication Date:
Report Number(s):
LA-UR-18-22688
Journal ID: ISSN 2041-6520
Grant/Contract Number:
AC52-06NA25396; AC02-76SF00515; 20180005DR
Type:
Published Article
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 9; Journal Issue: 35; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1462444
Alternate Identifier(s):
OSTI ID: 1463561

Ferrier, Maryline G., Stein, Benjamin W., Bone, Sharon E., Cary, Samantha K., Ditter, Alexander S., Kozimor, Stosh A., Lezama Pacheco, Juan S., Mocko, Veronika, and Seidler, Gerald T.. The coordination chemistry of CmIII, AmIII, and AcIII in nitrate solutions: an actinide L3-edge EXAFS study. United States: N. p., Web. doi:10.1039/C8SC02270D.
Ferrier, Maryline G., Stein, Benjamin W., Bone, Sharon E., Cary, Samantha K., Ditter, Alexander S., Kozimor, Stosh A., Lezama Pacheco, Juan S., Mocko, Veronika, & Seidler, Gerald T.. The coordination chemistry of CmIII, AmIII, and AcIII in nitrate solutions: an actinide L3-edge EXAFS study. United States. doi:10.1039/C8SC02270D.
Ferrier, Maryline G., Stein, Benjamin W., Bone, Sharon E., Cary, Samantha K., Ditter, Alexander S., Kozimor, Stosh A., Lezama Pacheco, Juan S., Mocko, Veronika, and Seidler, Gerald T.. 2018. "The coordination chemistry of CmIII, AmIII, and AcIII in nitrate solutions: an actinide L3-edge EXAFS study". United States. doi:10.1039/C8SC02270D.
@article{osti_1462444,
title = {The coordination chemistry of CmIII, AmIII, and AcIII in nitrate solutions: an actinide L3-edge EXAFS study},
author = {Ferrier, Maryline G. and Stein, Benjamin W. and Bone, Sharon E. and Cary, Samantha K. and Ditter, Alexander S. and Kozimor, Stosh A. and Lezama Pacheco, Juan S. and Mocko, Veronika and Seidler, Gerald T.},
abstractNote = {Understanding actinide(III) (AnIII = CmIII, AmIII, AcIII) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, AnIII speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect – in large part – is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Here in this paper, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized CmIII, AmIII, and AcIII using AnIII L3-edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO3) concentration. Our results revealed that actinide aquo ions, An(H2O)x3+ (x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for CmIII, AmIII, and AcIII), were the dominant species in dilute HNO3 (0.05 M). In concentrated HNO3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO3)4.1±0.7(H2O)5.7±1.3(1.1±0.2)-, Am(NO3)3.4±0.7(H2O)5.4±0.5(0.4±0.1)-, and Ac(NO3)2.3±1.7(H2O)8.3±5.2(0.7±0.5)+ were observed. Data obtained at the intermediate HNO3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. Here, for all three metals, the intermediate models showed larger contributions from the 0.05 M HNO3 spectra than from the 16 M HNO3 spectra. Additionally, these efforts enabled the Cm–NO3 and Ac–NO3 distances to be measured for the first time. Moreover, the AnIII L3-edge EXAFS results, contribute to the growing body of knowledge associated with CmIII, AmIII, and AcIII coordination chemistry, in particular toward advancing understanding of AnIII solution phase speciation.},
doi = {10.1039/C8SC02270D},
journal = {Chemical Science},
number = 35,
volume = 9,
place = {United States},
year = {2018},
month = {8}
}

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