Document Detail


Diffusion and Adsorption of Uranyl Carbonate Species in Nanosized Mineral Fractures.
MedLine Citation:
PMID:  22206276     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Atomistic simulations were performed to study the diffusion and adsorption of Ca2UO2(CO3)3 and of some of its constituent species, i.e., UO22+, CO32-, and UO2CO3, in feldspar nano-sized fractures. Feldspar is important to uranium remediation efforts at the U.S. Department of Energy Hanford site as it has been found in recent studies to host contaminants within its intragrain fractures. In addition, uranyl carbonate species are known to dominate U(VI) speciation in conditions relevant to the Hanford site. Molecular dynamics (MD) simulations showed that the presence of the feldspar surface diminishes the diffusion coefficients of all the species considered in this work and that the diffusion coefficients do not reach their bulk aqueous solution values in the center of a 2.5 nm fracture. Moreover, the MD simulations showed that the rate of decrease in the diffusion coefficients with decreasing distance from the surface is greater for larger adsorbing species. Free energy profiles of the same species adsorbing on the feldspar surface revealed a large exothermic free energy of adsorption for UO22+ and UO2CO3, which are able to adsorb to the surface with their uranium atom directly bonded to a surface hydroxyl oxygen, whereas adsorption of CO32- and Ca2UO2(CO3)3, which attach to the surface via hydrogen bonding from a surface hydroxyl group to a carbonate oxygen, was calculated to be either only slightly exothermic or endothermic.
Authors:
Sebastien Kerisit; Chongxuan Liu
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-12-29
Journal Detail:
Title:  Environmental science & technology     Volume:  -     ISSN:  1520-5851     ISO Abbreviation:  -     Publication Date:  2011 Dec 
Date Detail:
Created Date:  2011-12-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0213155     Medline TA:  Environ Sci Technol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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