EUROPIUM RETENTION ONTO CLAY MINERALS FROM 25 TO 150°C: EXPERIMENTAL MEASUREMENTS, SPECTROSCOPIC FEATURES AND SORPTION MODELLING.
EUROPIUM RETENTION ONTO CLAY MINERALS FROM 25 TO 150°C: EXPERIMENTAL MEASUREMENTS, SPECTROSCOPIC FEATURES AND SORPTION MODELLING.
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DOI：
10.1016/j.gca.2006.06.1568
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发表时间：
2006-09
影响因子：
5
通讯作者：
E. Tertre;G. Berger;É. Simoni;S. Castet;E. Giffaut;M. Loubet;H. Catalette
中科院分区：
文献类型：
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作者：
E. Tertre;G. Berger;É. Simoni;S. Castet;E. Giffaut;M. Loubet;H. Catalette
在150°C下研究了Eu（III）在高岭石和蒙脱石上的吸附。粘土是纯化的样品，在蒙脱石的情况下用Na饱和。在25 ° C、40 ° C、80 ° C和150°C下，在0.5M NaClO 4溶液中进行批实验，以测量作为微量元素（<10− 6 mol/L）的Eu在溶液和高岭石之间的分配系数（Kd）。对于Na-蒙脱石，我们使用来自先前研究[Tertre，E.，Berger，G.，Castet，S.，Loubet，M.，Giffaut，E.，2005.钠基蒙脱石对Ni ~（2+）、Cs ~（3+）和Ln ~（3+）的吸附实验研究Geochim Cosmochim Acta 69，4937-4948]在完全相同的条件下获得。在特定的实验中，在相同的温度范围内的时间分辨激光荧光光谱（TRLFS）的Eu物种吸附到粘土矿物的数量和性质进行了研究。我们确定了一个独特的内层复杂的连接到两个粘土中的aluminol网站，假设是AlOEu 2+在颗粒的边缘，和第二个可交换的外层复杂的蒙脱石，可能在层间位置。Kd值用于将表面络合模型（DLM：扩散层模型）的参数从25 ° C调整至150°C。Eu配合物的数量和反应的化学计量比受到TRLFS的限制。两性铝醇位点的酸度常数取自另一项研究[Tertre，E.，Castet，S.，Berger，G.，Loubet，M.，Giffaut，E.高岭石和钠蒙脱石在25和60°C下的酸/碱表面化学：实验研究和建模。Geochim Cosmochim Acta，出版中]，其整合了粘土的负结构电荷对边缘位点的酸/碱性质的影响作为温度和离子强度的函数。建模的结果表明，所观察到的位移的吸附边缘向低pH值随着温度的升高，结果完全从AlOEu 2+边缘络合物的贡献。最后，我们成功地测试了我们的模型的性能，面对的预测与实验Kd数据。我们使用我们自己在较低离子强度（先前的研究）或较高悬浮密度和较高起始浓度（TRLFS运行，本研究）下获得的数据，以及来自其他实验研究的公开数据[Bradbury，M.H.，Baeyens，B.，2002. Eu在钠钙蒙脱石上的吸附：阳离子交换和表面络合的实验研究和模拟。Geochim Cosmochim Acta 66，2325-2334; Kowal-Fouchard，A.，2002.粘土上U（IV）和Eu（III）离子滞留机制研究：硅酸盐的影响。博士论文，法国巴黎南大学，330页]。
The sorption of Eu(III) onto kaolinite and montmorillonite was investigated up to 150°C. The clays were purified samples, saturated with Na in the case of montmorillonite. Batch experiments were conducted at 25, 40, 80 and 150°C in 0.5M NaClO4solutions to measure the distribution coefficients (Kd) of Eu as a trace element (<10−6mol/L) between the solution and kaolinite. For the Na-montmorillonite, we used Kd results from a previous study [Tertre, E., Berger, G., Castet, S., Loubet, M., Giffaut, E., 2005. Experimental study of adsorption of Ni2+, Cs+and Ln3+onto Na-montmorillonite up to 150°C. Geochim. Cosmochim. Acta69, 4937–4948] obtained under exactly the same conditions. The number and nature of the Eu species sorbed onto both clay minerals were investigated by time resolved laser fluorescence spectroscopy (TRLFS) in specific experiments in the same temperature range. We identified a unique inner-sphere complex linked to the aluminol sites in both clays, assumed to be AlOEu2+at the edge of the particles, and a second exchangeable outer-sphere complex for montmorillonite, probably in an interlayer position. The Kd values were used to adjust the parameters of a surface complexation model (DLM: diffuse layer model) from 25 to 150°C. The number of Eu complexes and the stoichiometry of reactions were constrained by TRLFS. The acidity constants of the amphoteric aluminol sites were taken from another study [Tertre, E., Castet, S., Berger, G., Loubet, M., Giffaut, E. Acid/base surface chemistry of kaolinite and Na-montmorillonite at 25 and 60°C: experimental study and modelling. Geochim. Cosmochim. Acta, in press], which integrates the influence of the negative structural charge of clays on the acid/base properties of edge sites as a function of temperature and ionic strength. The results of the modelling show that the observed shift of the sorption edge towards low pH with increasing temperature results solely from the contribution of the AlOEu2+edge complexes. Finally, we successfully tested the performance of our model by confronting the predictions with experimental Kd data. We used our own data obtained at lower ionic strength (previous study) or higher suspension density and higher starting concentration (TRLFS runs, this study), as well as published data from other experimental studies [Bradbury, M.H., Baeyens, B., 2002. Sorption of Eu on Na and Ca-montmorillonite: experimental investigations and modeling with cation exchange and surface complexation. Geochim. Cosmochim. Acta66, 2325–2334; Kowal-Fouchard, A., 2002. Etude des mécanismes de rétention des ions U(IV) et Eu(III) sur les argiles: influence des silicates. Ph.D. Thesis, Université Paris Sud, France, 330p].