期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 44, 期 3, 页码 928-934出版社
AMER CHEMICAL SOC
DOI: 10.1021/es902194x
关键词
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资金
- Office of Science, Office of Biological and Environmental Research, Environmental Remediation Sciences Program, of the U.S. Department of Energy [DE-AC02-05CH11231]
- OBER-ERSP [ER63609-1021814]
- Stanford NSF Environmental Molecular Science Institute [NSF-CHE-0431425]
- National Science Foundation Chemistry and Earth Sciences Divisions
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 UO22+ 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 (similar to 5) and limited dissolved calcium are optimal for uranium adsorption.
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