Prediction of Intrinsic Cesium Desorption from Na-Smectite in Mixed Cation Solutions.
Prediction of Intrinsic Cesium Desorption from Na-Smectite in Mixed Cation Solutions.
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DOI：
10.1021/acs.est.5b01884
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发表时间：
2015-08
影响因子：
11.4
通讯作者：
K. Fukushi;Tomokazu Fukiage
中科院分区：
文献类型：
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作者：
K. Fukushi;Tomokazu Fukiage
定量了解蒙脱石中吸收放射性核素的稳定性对于评估核废料处理工程屏障的性能是必要的。我们之前的研究表明，由二价阳离子引发的蒙脱石血小板的空间组织导致蒙脱石中固有Cs的明显固定，因为一些Cs被保留在形成的附着体内。天然水通常是Na（+）和二价阳离子（Ca（2+）和Mg(2+)）的混合物。因此，本研究通过批处理实验、晶粒尺寸测量和阳离子交换模型（CEM）研究了在不同阳离子浓度的混合Na(+)-二价阳离子溶液中Na- smite中本征Cs的解吸行为。结果表明，Na（+）浓度的增加有利于Cs的脱附，因为Na（+）起到了分散剂的作用。蒙脱石中Na（+）分数的对数与可达Cs分数呈线性关系。这种关系使我们能够预测可达Cs分数作为溶液阳离子组成的函数。考虑空间组织影响的修正CEM表明，蒙脱石中固有Cs的稳定性受Na（+）浓度的控制，并且几乎与天然水中二价阳离子的浓度无关。
Quantitative understanding of the stability of sorbed radionuclides in smectite is necessary to assess the performance of engineering barriers used for nuclear waste disposal. Our previous study demonstrated that the spatial organization of the smectite platelets triggered by the divalent cations led to the apparent fixation of intrinsic Cs in smectite, because some Cs is retained inside the formed tactoids. Natural water is usually a mixture of Na(+) and divalent cations (Ca(2+) and Mg(2+)). This study therefore investigated the desorption behavior of intrinsic Cs in Na-smecite in mixed Na(+)-divalent cation solutions under widely various cation concentrations using batch experiments, grain size measurements, and cation exchange modeling (CEM). Results show that increased Na(+) concentrations facilitate Cs desorption because Na(+) serves as the dispersion agent. A linear relation was obtained between the logarithm of the Na(+) fraction and the accessible Cs fraction in smectite. That relation enables the prediction of accessible Cs fraction as a function of solution cationic compositions. The corrected CEM considering the effects of the spatial organization suggests that the stability of intrinsic Cs in the smectite is governed by the Na(+) concentration, and suggests that it is almost independent of the concentrations of divalent cations in natural water.