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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Determination of the Driving Force for the Hydration of the Swelling Clays from Computation of the Hydration Energy of the Interlayer Cations and the Clay Layer
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Determination of the Driving Force for the Hydration of the Swelling Clays from Computation of the Hydration Energy of the Interlayer Cations and the Clay Layer

机译：通过计算层间阳离子和粘土层的水化能确定膨胀粘土水化的驱动力

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The key feature of swelling clays such as montmorillonite,in contrast with the nonswelling clays,is their ability to adsorb water in the interlayer space.This interlayer water interacts with the interlayer cations or with the silicate layer surface inside the interlayer space,or with both.However,no direct experimental technique offers the possibility to determine separately these two contributions.In order to determine the hydration energy for interlayer alkali cations,we use a combination of electrostatic calculations of the surface energy and measurements of immersion heats in clays.The results show that Li~+and Na~+cations are characterized by a strongly exothermic hydration energy in the interlayer space,in contrast with K~+,Rb~+,and Cs~+which have a much lower hydration energy in the interlayer space.The extreme situation is that of Cs~+,for which an endothermic hydration energy value is obtained.These trends are in good agreement with results from molecular modeling calculations and consistent with the evolution observed in the water adsorption isotherms.The hydration energy of the silicate layers was also calculated,and the total driving force for hydration in swelling clays could therefore be determined.For Li~+-and Na~+-montmorillonite,the hydration of cations is clearly the main contribution to the overall driving force for the hydration of clay.On the contrary,hydration of the silicate layers plays the most important role in the hydration of montmorillonite exchanged with the larger cations such as K~+,Rb~+,and Cs~+.These results provide a physical basis for the differences observed in macroscopic swelling behavior between Li~+-and Na~+-montmorillonite,on one hand,and K~+-,Rb~+-and Cs~+-montmorillonite,on the other hand.
机译：与非膨胀粘土相反，膨润土如蒙脱土的主要特征是它们在层间空间中吸收水的能力。这种层间水与层间阳离子或层间空间内的硅酸盐层表面相互作用，或与两者相互作用但是，没有直接的实验技术可以单独确定这两个贡献。为了确定层间碱金属阳离子的水合能，我们结合使用了表面能的静电计算和粘土中浸入热的测量方法。结果表明，Li〜+和Na〜+阳离子在层间空间具有强烈的放热水化能，而K〜+，Rb〜+和Cs〜+在层间空间具有较低的水化能。极端情况是Cs〜+的情况，其获得吸热水合能值，这些趋势与分子模型计算的结果非常吻合还计算了硅酸盐层的水化能量，从而确定了膨胀黏土中水合的总驱动力。对于Li〜+和Na〜+-蒙脱土，阳离子的水合显然是对粘土水合的整体驱动力的主要贡献。相反，硅酸盐层的水合在与较大的阳离子（如K〜+）交换的蒙脱石的水合中起着最重要的作用，这些结果为一方面观察到Li〜+-和Na〜+-蒙脱石之间的宏观溶胀行为的差异以及K〜+-，Rb〜+-和Cs​​〜+的物理基础提供了物理基础。另一方面，Cs〜+-蒙脱石。

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