Stumpf T, Curtius H, Walther C, Dardenne K, Ufer K, Fanghänelt T
Forschungszentrum Karlsruhe GmbH, Institut für Nukleare Entsorgung, P.O. Box 3640, D-76021 Karlsruhe, Germany.
Environ Sci Technol. 2007 May 1;41(9):3186-91. doi: 10.1021/es0624873.
The behavior of radionuclides in the environment (geo-, hydro-, and biosphere) is determined by interface reactions like adsorption, ion exchange, and incorporation processes. Presently, operational gross parameters for the distribution between solution and minerals are available. For predictive modeling of the radionuclide mobility in such systems, however, individual reactions and processes need to be localized, characterized, and quantified. A prerequisite for localization and clarification of the concerned processes is the use of modern advanced analytical and speciation methods, especially spectroscopy. In this study, Eu(III) was chosen as an analogue for trivalent actinides to identify the different species that occur by the Ln(III)/hydrotalcite interaction. Therefore, Eu(III) doped Mg-Al-Cl-hydrotalcite was synthesized and investigated by TRLFS, EXAFS, and XRD measurements. Two different Eu/hydrotalcite species were obtained. The minor part of the lanthanide is found to be inner-sphere sorbed onto the mineral surface, while the dominating Eu/hydrotalcite species consists of Eu(III) that is incorporated into the hydrotalcite lattice. Both Eu/hydrotalcite species have been characterized by their fluorescence emission spectra and lifetimes. Structural parameters of the incorporated Eu(III) species determined by EXAFS indicate a coordination number of 6.6 +/- 1.3 and distances of 2.41 +/- 0.02 A for the first Eu-OH shell.
放射性核素在环境（地质圈、水圈和生物圈）中的行为由诸如吸附、离子交换和掺入过程等界面反应决定。目前，已有溶液与矿物质之间分布的操作总参数。然而，为了对这类系统中放射性核素的迁移率进行预测建模，需要对各个反应和过程进行定位、表征和量化。对相关过程进行定位和阐明的一个前提是使用现代先进的分析和形态分析方法，尤其是光谱学方法。在本研究中，选择铕（III）作为三价锕系元素的类似物，以识别由镧系元素（III）/水滑石相互作用产生的不同物种。因此，合成了掺铕（III）的镁铝氯水滑石，并通过时间分辨激光荧光光谱（TRLFS）、扩展X射线吸收精细结构（EXAFS）和X射线衍射（XRD）测量进行了研究。获得了两种不同的铕/水滑石物种。发现镧系元素的一小部分以内层吸附的形式存在于矿物表面，而占主导地位的铕/水滑石物种由掺入水滑石晶格的铕（III）组成。两种铕/水滑石物种均通过其荧光发射光谱和寿命进行了表征。由EXAFS确定的掺入铕（III）物种的结构参数表明，第一铕-氧壳层的配位数为6.6±1.3，距离为2.41±0.02埃。
