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Title: Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation

Abstract

Here, Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10 –15–10 –5 M at pH 8. Experiments with initial Pu concentrations of 10 –15 – 10 –8 M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of the initial Pu oxidation state. At initial concentrations >10 –8 M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10 –8 – 10 –6 M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10 –6 M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu 4O 7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxialmore » distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1343022
Report Number(s):
LLNL-JRNL-680462
Journal ID: ISSN 0013-936X
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 50; Journal Issue: 13; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES

Citation Formats

Zhao, Pihong, Begg, James D., Zavarin, Mavrik, Tumey, Scott J., Williams, Ross, Dai, Zurong R., Kips, Ruth, and Kersting, Annie B. Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation. United States: N. p., 2016. Web. doi:10.1021/acs.est.6b00605.
Zhao, Pihong, Begg, James D., Zavarin, Mavrik, Tumey, Scott J., Williams, Ross, Dai, Zurong R., Kips, Ruth, & Kersting, Annie B. Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation. United States. doi:10.1021/acs.est.6b00605.
Zhao, Pihong, Begg, James D., Zavarin, Mavrik, Tumey, Scott J., Williams, Ross, Dai, Zurong R., Kips, Ruth, and Kersting, Annie B. Mon . "Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation". United States. doi:10.1021/acs.est.6b00605. https://www.osti.gov/servlets/purl/1343022.
@article{osti_1343022,
title = {Plutonium(IV) and (V) sorption to goethite at sub-femtomolar to micromolar concentrations: Redox transformations and surface precipitation},
author = {Zhao, Pihong and Begg, James D. and Zavarin, Mavrik and Tumey, Scott J. and Williams, Ross and Dai, Zurong R. and Kips, Ruth and Kersting, Annie B.},
abstractNote = {Here, Pu(IV) and Pu(V) sorption to goethite was investigated over a concentration range of 10–15–10–5 M at pH 8. Experiments with initial Pu concentrations of 10–15 – 10–8 M produced linear Pu sorption isotherms, demonstrating that Pu sorption to goethite is not concentration-dependent across this concentration range. Equivalent Pu(IV) and Pu(V) sorption Kd values obtained at 1 and 2-week sampling time points indicated that Pu(V) is rapidly reduced to Pu(IV) on the goethite surface. Further, it suggested that Pu surface redox transformations are sufficiently rapid to achieve an equilibrium state within 1 week, regardless of the initial Pu oxidation state. At initial concentrations >10–8 M, both Pu oxidation states exhibited deviations from linear sorption behavior and less Pu was adsorbed than at lower concentrations. NanoSIMS and HRTEM analysis of samples with initial Pu concentrations of 10–8 – 10–6 M indicated that Pu surface and/or bulk precipitation was likely responsible for this deviation. In 10–6 M Pu(IV) and Pu(V) samples, HRTEM analysis showed the formation of a body centered cubic (bcc) Pu4O7 structure on the goethite surface, confirming that reduction of Pu(V) had occurred on the mineral surface and that epitaxial distortion previously observed for Pu(IV) sorption occurs with Pu(V) as well.},
doi = {10.1021/acs.est.6b00605},
journal = {Environmental Science and Technology},
number = 13,
volume = 50,
place = {United States},
year = {Mon Jun 06 00:00:00 EDT 2016},
month = {Mon Jun 06 00:00:00 EDT 2016}
}

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