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Title: Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems

Abstract

This study investigated the influences of pH, bicarbonate, and calcium on U(VI) adsorption and reduction by synthetic nanosize zero valent iron (nano Fe0) particles under an anoxic condition. The results showed that about 87.1%, 82.7% and 78.3% of U(VI) could be reduced within 96 hours in the presence of 10 mM bicarbonate at pHs 6.92, 8.03 and 9.03, respectively. The rates of U(VI) reduction and adsorption by nano Fe0, however, varied significantly with increasing pH and concentrations of bicarbonate and/or calcium. Solid phase analysis by X-ray photoelectron spectroscopy confirmed the formation of UO2 and iron (hydr)oxides as a result of the redox interactions between adsorbed U(VI) and nano Fe0. This study highlights the potential important role of groundwater chemical composition in controlling the rates of U(VI) reductive immobilization using nano Fe0 in subsurface environments.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
993664
Report Number(s):
PNNL-SA-68628
Journal ID: ISSN 0013-936X; ESTHAG; 31295; KP1501040; TRN: US1008104
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science & Technology, 44(20):7783-7789; Journal Volume: 44; Journal Issue: 20
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ACID CARBONATES; ADSORPTION; CALCIUM; CHEMICAL COMPOSITION; IRON; X-RAY PHOTOELECTRON SPECTROSCOPY; zero valent iron, Uranium, adsorption, reduction, immobilization, nanoparticles; Environmental Molecular Sciences Laboratory

Citation Formats

Yan, Sen, Hua, Bin, Bao, Zhengyu, Yang, John, Liu, Chongxuan, and Deng, Baolin. Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems. United States: N. p., 2010. Web. doi:10.1021/es9036308.
Yan, Sen, Hua, Bin, Bao, Zhengyu, Yang, John, Liu, Chongxuan, & Deng, Baolin. Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems. United States. doi:10.1021/es9036308.
Yan, Sen, Hua, Bin, Bao, Zhengyu, Yang, John, Liu, Chongxuan, and Deng, Baolin. 2010. "Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems". United States. doi:10.1021/es9036308.
@article{osti_993664,
title = {Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems},
author = {Yan, Sen and Hua, Bin and Bao, Zhengyu and Yang, John and Liu, Chongxuan and Deng, Baolin},
abstractNote = {This study investigated the influences of pH, bicarbonate, and calcium on U(VI) adsorption and reduction by synthetic nanosize zero valent iron (nano Fe0) particles under an anoxic condition. The results showed that about 87.1%, 82.7% and 78.3% of U(VI) could be reduced within 96 hours in the presence of 10 mM bicarbonate at pHs 6.92, 8.03 and 9.03, respectively. The rates of U(VI) reduction and adsorption by nano Fe0, however, varied significantly with increasing pH and concentrations of bicarbonate and/or calcium. Solid phase analysis by X-ray photoelectron spectroscopy confirmed the formation of UO2 and iron (hydr)oxides as a result of the redox interactions between adsorbed U(VI) and nano Fe0. This study highlights the potential important role of groundwater chemical composition in controlling the rates of U(VI) reductive immobilization using nano Fe0 in subsurface environments.},
doi = {10.1021/es9036308},
journal = {Environmental Science & Technology, 44(20):7783-7789},
number = 20,
volume = 44,
place = {United States},
year = 2010,
month =
}
  • The role of Fe(II) and Fe(III) on U(VI) reduction by nanoscale zerovalent iron (nanoFe0) was investigated using two iron chelators 1,10-phenanthroline and triethanolamine (TEA) under a CO2-free anoxic condition. The results showed U(VI) reduction was strongly inhibited by 1,10-phenanthroline and TEA in a pH range from 6.92 to 9.03. For instance, at pH 6.92 the observed U(VI) reduction rates decreased by 80.7% and 82.3% in the presence of 1,10-phenanthroline and TEA, respectively. The inhibition was attributed to the formation of stable complexes between 1,10-phenanthroline and Fe(II) or TEA and Fe(III). In the absence of iron chelators, U(VI) reduction can bemore » enhanced by surface-bound Fe(II) on nanoFe0. Our results suggested that Fe(III) and Fe(II) probably acted as an electron shuttle to mediate the transfer of electrons from nanoFe0 to U(VI), therefore a combined system with Fe(II), Fe(III) and nanoFe0 can facilitate the U(VI) reductive immobilization in the contaminated groundwater.« less
  • The reaction of hexavalent chromium (Cr(VI)) with zerovalent iron (Fe{sup 0}) during soil and groundwater remediation is an important environmental process. This study used several techniques including X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy to investigate nanometer scale Fe{sup 0} particles (nano Fe{sup 0}) treated with Cr(III) and Cr(VI). X-ray diffraction and XPS analyses of oxidized nano Fe{sup 0} showed the crystalline Fe(III) phase is composed of lepidocrocite ({gamma}-FeOOH). Results of XPS Cr 2p data and Cr K-edge X-ray absorption near edge spectroscopy (XANES) provided evidence that Cr(VI) was entirely reduced to Cr(III) by nano Fe{sup 0} with nomore » residual Cr(VI) after reaction. In addition, XPS and XANES results of Cr(III) precipitated as Cr(OH){sub 3} in the presence of corroding nano Fe{sup 0} were nearly identical to the Cr(VI)-nano Fe{sup 0} reaction product. Detailed analysis of XPS O 1s line spectra revealed that both Cr(III)- and Cr(VI)-treated nano Fe{sup 0} yielded a predominantly hydroxylated Cr(OH){sub 3} and/or a mixed phase Cr{sub x}Fe{sub 1-x}(OH){sub 3} product. The structure of the Cr(III)- and Cr(VI)-treated nano Fe{sup 0} determined using extended X-ray absorption fine structure spectroscopy (EXAFS) revealed octahedral Cr(III) with Cr-O interatomic distances between 1.97 and 1.98 {angstrom} for both Cr(III) and Cr(VI) treatments and a pronounced Cr-Cr second interatomic shell at 3.01 {angstrom}. Our results suggest that the reaction product of Cr(VI)-treated nano Fe{sup 0} is either a poorly ordered Cr(OH){sub 3} precipitate or possibly a mixed phase Cr{sub x}Fe{sub 1-x}(OH){sub 3} product, both of which are highly insoluble under environmental conditions.« less