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Title: Investigation of the Transformation of Uranium under Iron-Reducing Conditions: Reduction of UVI by Biogenic FeII/FeIII Hydroxide (Green Rust)

Abstract

The research we are proposing addresses fundamental aspects of the effects of coupled biotic and abiotic processes on U speciation in subsurface environments where Fe redox cycling is significant. The long-term objective of this research is to evaluate whether reduction of U{sup VI} by biogenic GRs is a significant immobilization mechanism in subsurface environments. Our preliminary experiments have shown that biogenic GRs can reduce U{sup VI} to U{sup IV}; however, little is known about how biogeochemical conditions (such as pH, U concentration, carbonate concentration, and the presence of cocontaminants) and GR composition affect the rate and products of U{sup VI} reduction by GRs. It is also unclear which biogeochemical conditions favor formation of GR over other non-reactive Fe-bearing biomineralization products from the reduction of Fe{sup III} by DIRB. To address these issues, the following objectives are proposed: (1) Identify the geochemical conditions that favor the formation of biogenic GRs from the reduction of Fe{sup III} oxyhydroxides by DIRB (e.g., Shewanella and Geobacter species). (2) Characterize the chemical composition of biogenic GRs (e.g., Fe{sup II}:Fe{sup III} ratios and interlayer anions) and the effects of compositional variability on the rate and extent of U{sup VI} reduction. (3) Evaluate the effects of variationsmore » in geochemical conditions--particularly pH, U concentration, carbonate concentration, the presence of organic ligands, and the presence of reducible co-contaminants--both on the kinetics of U{sup VI} reduction by biogenic GR and on the composition of U-bearing mineral phases. Particular attention will be given to examining geochemical conditions relevant to conditions at DOE field sites. (4) Determine the potential for coupling the reduction of Fe{sup III} by DIRB to the reduction of U{sup VI} via biogenic Fe{sup II} species (including biogenic GRs). The objectives outlined above will be achieved by testing the following hypotheses: (1) The formation of GRs by dissimilatory Fe{sup III} reduction is controlled by Fe{sup III} speciation, solution composition, and microbial physiology. (2) The chemical composition and structural properties of biogenic GRs are variable and depend on the conditions under which they were formed. (3) The rate of U{sup VI} reduction by biogenic GRs varies depending on their chemical composition and structure, particularly with respect to the Fe{sup II}/Fe{sup III} ratio and the nature of the interlayer anions. (4) The rate of U{sup VI} reduction by a given biogenic GR is affected by the solution composition (e.g., pH, uranium concentration, the concentration of carbonate and other ligands, and the presence of other potential oxidants). Moreover, the solution composition affects both the speciation of U{sup VI} and U{sup IV} and the stability of the GR. (5) The reduction of UVI to UIV can be coupled to dissimilatory FeIII reduction under conditions that promote the formation of biogenic GR and other reactive Fe{sup II} species. The results of this research will increase our understanding of the coupling of biotic and abiotic processes with respect to the speciation of U in Fe{sup III}-reducing environments. This information has direct applications to understanding contaminant transport and the development of in situ bioremediation technologies for treatment of subsurface U contamination.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Iowa, Iowa City, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
895477
Report Number(s):
CONF-NABIR2004-42
TRN: US0700461
Resource Type:
Conference
Resource Relation:
Conference: Annual NABIR PI Meeting, March 15-17, 2004, Warrenton, VA
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; ANIONS; BIOREMEDIATION; CARBONATES; CHEMICAL COMPOSITION; CONTAMINATION; HYDROXIDES; KINETICS; OXIDIZERS; PHYSIOLOGY; STABILITY; TESTING; TRANSFORMATIONS; TRANSPORT; URANIUM

Citation Formats

O’Loughlin, Edward, Scherer, Michelle, Kemner, Kenneth, and Kelly, Shelly. Investigation of the Transformation of Uranium under Iron-Reducing Conditions: Reduction of UVI by Biogenic FeII/FeIII Hydroxide (Green Rust). United States: N. p., 2004. Web.
O’Loughlin, Edward, Scherer, Michelle, Kemner, Kenneth, & Kelly, Shelly. Investigation of the Transformation of Uranium under Iron-Reducing Conditions: Reduction of UVI by Biogenic FeII/FeIII Hydroxide (Green Rust). United States.
O’Loughlin, Edward, Scherer, Michelle, Kemner, Kenneth, and Kelly, Shelly. 2004. "Investigation of the Transformation of Uranium under Iron-Reducing Conditions: Reduction of UVI by Biogenic FeII/FeIII Hydroxide (Green Rust)". United States. https://www.osti.gov/servlets/purl/895477.
@article{osti_895477,
title = {Investigation of the Transformation of Uranium under Iron-Reducing Conditions: Reduction of UVI by Biogenic FeII/FeIII Hydroxide (Green Rust)},
author = {O’Loughlin, Edward and Scherer, Michelle and Kemner, Kenneth and Kelly, Shelly},
abstractNote = {The research we are proposing addresses fundamental aspects of the effects of coupled biotic and abiotic processes on U speciation in subsurface environments where Fe redox cycling is significant. The long-term objective of this research is to evaluate whether reduction of U{sup VI} by biogenic GRs is a significant immobilization mechanism in subsurface environments. Our preliminary experiments have shown that biogenic GRs can reduce U{sup VI} to U{sup IV}; however, little is known about how biogeochemical conditions (such as pH, U concentration, carbonate concentration, and the presence of cocontaminants) and GR composition affect the rate and products of U{sup VI} reduction by GRs. It is also unclear which biogeochemical conditions favor formation of GR over other non-reactive Fe-bearing biomineralization products from the reduction of Fe{sup III} by DIRB. To address these issues, the following objectives are proposed: (1) Identify the geochemical conditions that favor the formation of biogenic GRs from the reduction of Fe{sup III} oxyhydroxides by DIRB (e.g., Shewanella and Geobacter species). (2) Characterize the chemical composition of biogenic GRs (e.g., Fe{sup II}:Fe{sup III} ratios and interlayer anions) and the effects of compositional variability on the rate and extent of U{sup VI} reduction. (3) Evaluate the effects of variations in geochemical conditions--particularly pH, U concentration, carbonate concentration, the presence of organic ligands, and the presence of reducible co-contaminants--both on the kinetics of U{sup VI} reduction by biogenic GR and on the composition of U-bearing mineral phases. Particular attention will be given to examining geochemical conditions relevant to conditions at DOE field sites. (4) Determine the potential for coupling the reduction of Fe{sup III} by DIRB to the reduction of U{sup VI} via biogenic Fe{sup II} species (including biogenic GRs). The objectives outlined above will be achieved by testing the following hypotheses: (1) The formation of GRs by dissimilatory Fe{sup III} reduction is controlled by Fe{sup III} speciation, solution composition, and microbial physiology. (2) The chemical composition and structural properties of biogenic GRs are variable and depend on the conditions under which they were formed. (3) The rate of U{sup VI} reduction by biogenic GRs varies depending on their chemical composition and structure, particularly with respect to the Fe{sup II}/Fe{sup III} ratio and the nature of the interlayer anions. (4) The rate of U{sup VI} reduction by a given biogenic GR is affected by the solution composition (e.g., pH, uranium concentration, the concentration of carbonate and other ligands, and the presence of other potential oxidants). Moreover, the solution composition affects both the speciation of U{sup VI} and U{sup IV} and the stability of the GR. (5) The reduction of UVI to UIV can be coupled to dissimilatory FeIII reduction under conditions that promote the formation of biogenic GR and other reactive Fe{sup II} species. The results of this research will increase our understanding of the coupling of biotic and abiotic processes with respect to the speciation of U in Fe{sup III}-reducing environments. This information has direct applications to understanding contaminant transport and the development of in situ bioremediation technologies for treatment of subsurface U contamination.},
doi = {},
url = {https://www.osti.gov/biblio/895477}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 17 00:00:00 EST 2004},
month = {Wed Mar 17 00:00:00 EST 2004}
}

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