Role of Surface Alteration in Determining the Mobility of U(VI) in the Presence of Citrate: Implications for Extraction of U(VI) from Soils

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• 作者：Brian A. Logue ; Robert W. Smith ; and John C. Westall
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：July 1, 2004
• 年：2004
• 卷：38
• 期：13
• 页码：3752 - 3759
• 全文大小：150K
• 年卷期：v.38,no.13(July 1, 2004)
• ISSN：1520-5851

文摘

In the present study, the adsorption of U(VI) by a naturaliron-rich sand in the presence of citrate was studied overa range of citrate concentrations and pH values. Adsorptionof U(VI) on the iron-rich sand decreased in the presence ofincreasing concentrations of citrate. Adsorption ofcitrate to the sand was weak under most conditionsstudied. Several explanations for the adsorption behaviorof U(VI) and citrate were investigated, including aqueouscomplexation of U(VI) by citrate, competition of U(VI) andcitrate for adsorption sites, and extraction of Fe and Alfrom the sorbent surface by citrate (surface alteration).Although aqueous complexation of U(VI) by citrate may stillplay a significant role, both competitive adsorption andaqueous complexation proved to be inadequate explanationsof the adsorption behavior. Both physical surface alteration(i.e., loss of surface area) and chemical surface alteration(i.e., change in the chemical composition of the sand surface)were investigated, with chemical surface alterationcontrolling the bulk of U(VI) adsorption. Considering theseresults, remediation schemes that involve organiccomplexing agents should address the possibility ofsurface alteration affecting radionuclide adsorption andmobility.