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Title: Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite

Abstract

Reduction of U(VI) to U(VI) on mineral surfaces is often considered a one-step two-electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies Indicates U(VI) can undergo a one-electron reduction to U(V) without further progression to U(VI),. We investigated reduction pathways of uranium by reducing U(VI) electrochemically on a, magnetite electrode at,pH 3.4. Cyclic voltammetry confirms the one-electron reduction of U(VI) . Formation of nanosize uranium precipitates on the magnetite surface at reducing potentials and dissolution of the solids at oxidizing potentials are observed by in situ electrochemical atomic force microscopy. XPS, analysis Of the magnetite electrodes polarized in uranium solutions at voltages - from -0.1 to -0.9 V (E-U(VI)/U(V)(0)= -0.135 V vs Ag/AgCl) show the presence of, only U(V) and U(VI). The sample with the highest U(V)/U(VI) ratio was prepared at -0.7 V, where the longest average U-O-axial distance of 2.05 + 0.01 A was evident in the same sample revealed by extended X-ray absorption fine structure analysis. The results demonstrate that the electrochemical reduction of U(VI) On magnetite only yields,U(V), even at a potential of -0.9 V, which favors the one-electron reduction mechanism, U(V) does not disproportionate but stabilizes on magnetite through precipitation Ofmore » mixed-valence state -U(V)/U(VI) solids.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1392063
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 49; Journal Issue: 10; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
Atomic force microscopy; Disproportionation; Uranium, Uranyl(V); Voltammetry; X-ray absorption spectroscopy; X-ray photoelectron spectroscopy

Citation Formats

Yuan, Ke, Ilton, Eugene S., Antonio, Mark R., Li, Zhongrui, Cook, Peter J., and Becker, Udo. Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite. United States: N. p., 2015. Web. doi:10.1021/acs.est.5b00025.
Yuan, Ke, Ilton, Eugene S., Antonio, Mark R., Li, Zhongrui, Cook, Peter J., & Becker, Udo. Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite. United States. doi:10.1021/acs.est.5b00025.
Yuan, Ke, Ilton, Eugene S., Antonio, Mark R., Li, Zhongrui, Cook, Peter J., and Becker, Udo. Tue . "Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite". United States. doi:10.1021/acs.est.5b00025.
@article{osti_1392063,
title = {Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite},
author = {Yuan, Ke and Ilton, Eugene S. and Antonio, Mark R. and Li, Zhongrui and Cook, Peter J. and Becker, Udo},
abstractNote = {Reduction of U(VI) to U(VI) on mineral surfaces is often considered a one-step two-electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies Indicates U(VI) can undergo a one-electron reduction to U(V) without further progression to U(VI),. We investigated reduction pathways of uranium by reducing U(VI) electrochemically on a, magnetite electrode at,pH 3.4. Cyclic voltammetry confirms the one-electron reduction of U(VI) . Formation of nanosize uranium precipitates on the magnetite surface at reducing potentials and dissolution of the solids at oxidizing potentials are observed by in situ electrochemical atomic force microscopy. XPS, analysis Of the magnetite electrodes polarized in uranium solutions at voltages - from -0.1 to -0.9 V (E-U(VI)/U(V)(0)= -0.135 V vs Ag/AgCl) show the presence of, only U(V) and U(VI). The sample with the highest U(V)/U(VI) ratio was prepared at -0.7 V, where the longest average U-O-axial distance of 2.05 + 0.01 A was evident in the same sample revealed by extended X-ray absorption fine structure analysis. The results demonstrate that the electrochemical reduction of U(VI) On magnetite only yields,U(V), even at a potential of -0.9 V, which favors the one-electron reduction mechanism, U(V) does not disproportionate but stabilizes on magnetite through precipitation Of mixed-valence state -U(V)/U(VI) solids.},
doi = {10.1021/acs.est.5b00025},
journal = {Environmental Science and Technology},
issn = {0013-936X},
number = 10,
volume = 49,
place = {United States},
year = {2015},
month = {5}
}