Document Detail


Impact of uranyl-calcium-carbonato complexes on uranium(VI) adsorption to synthetic and natural sediments.
MedLine Citation:
PMID:  20058915     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Adsorption on soil and sediment solids may decrease aqueous uranium concentrations and limit its propensity for migration in natural and contaminated settings. Uranium adsorption will be controlled in large part by its aqueous speciation, with a particular dependence on the presence of dissolved calcium and carbonate. Here we quantify the impact of uranyl speciation on adsorption to both goethite and sediments from the Hanford Clastic Dike and Oak Ridge Melton Branch Ridgetop formations. Hanford sediments were preconditioned with sodium acetate and acetic acid to remove carbonate grains, and Ca and carbonate were reintroduced at defined levels to provide a range of aqueous uranyl species. U(VI) adsorption is directly linked to UO(2)(2+) speciation, with the extent of retention decreasing with formation of ternary uranyl-calcium-carbonato species. Adsorption isotherms under the conditions studied are linear, and K(d) values decrease from 48 to 17 L kg(-1) for goethite, from 64 to 29 L kg (-1) for Hanford sediments, and from 95 to 51 L kg(-1) for Melton Branch sediments as the Ca concentration increases from 0 to 1 mM at pH 7. Our observations reveal that, in carbonate-bearing waters, neutral to slightly acidic pH values ( approximately 5) and limited dissolved calcium are optimal for uranium adsorption.
Authors:
Brandy D Stewart; Melanie A Mayes; Scott Fendorf
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Environmental science & technology     Volume:  44     ISSN:  0013-936X     ISO Abbreviation:  Environ. Sci. Technol.     Publication Date:  2010 Feb 
Date Detail:
Created Date:  2010-01-28     Completed Date:  2010-04-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0213155     Medline TA:  Environ Sci Technol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  928-34     Citation Subset:  IM    
Affiliation:
Environmental & Earth System Science, Stanford University, Stanford, CA 94305, USA.
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MeSH Terms
Descriptor/Qualifier:
Adsorption
Calcium Carbonate / chemistry*
Environmental Monitoring
Geologic Sediments / chemistry*
Hydrogen-Ion Concentration
Silicon Dioxide / chemistry
Uranium Compounds / chemistry*
Water Pollutants, Radioactive / chemistry*
Chemical
Reg. No./Substance:
0/Uranium Compounds; 0/Water Pollutants, Radioactive; 471-34-1/Calcium Carbonate; 7631-86-9/Silicon Dioxide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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