Rotenberg Benjamin, Marry Virginie, Dufrêche Jean-François, Giffaut Eric, Turq Pierre
Université Pierre et Marie Curie-Paris 6, Laboratoire Liquides Ioniques et Interfaces Chargées, UMR CNRS 7612, 4 pl. Jussieu, Paris cedex F-75005, France.
J Colloid Interface Sci. 2007 May 15;309(2):289-95. doi: 10.1016/j.jcis.2007.01.090. Epub 2007 Mar 8.
The mobility of particles is generally lowered by the presence of a confining medium, both because of geometrical effects, and because of the interactions with the confining surfaces, especially when the latter are charged. The water/mineral interface plays a central role in the dynamics of ions. The ionic mobility in clays is often understood as an interplay between the diffusion of mobile ions and their possible trapping at the mineral surfaces. We describe how to build a two-state diffusion-reaction scheme from the microscopic dynamics of ions, controlled by their interaction with a mineral surface. The starting point is an atomic description of the clay interlayer using molecular simulations. These provide a complete description of the ionic dynamics on short time and length scales. Using the results of these simulations, we then build a robust mesoscopic (Fokker-Planck) description. In turn, this mesoscopic description is used to determine the mobility of the ions in the interlayer. These results can then be cast into a diffusion-reaction scheme, introducing in particular the fraction of mobile ions, or equivalently the distribution coefficient Kd. This coefficient is of great importance in characterizing electrokinetic phenomena in porous materials.
由于几何效应以及与限制表面的相互作用，尤其是当限制表面带电时，限制介质的存在通常会降低粒子的迁移率。水/矿物界面在离子动力学中起着核心作用。粘土中的离子迁移率通常被理解为可移动离子的扩散与其在矿物表面可能被捕获之间的相互作用。我们描述了如何从离子的微观动力学构建一个双态扩散 - 反应方案，该动力学由离子与矿物表面的相互作用控制。起点是使用分子模拟对粘土夹层进行原子描述。这些描述了短时间和长度尺度上离子动力学的完整情况。利用这些模拟结果，我们接着构建一个稳健的介观（福克 - 普朗克）描述。反过来，这个介观描述用于确定夹层中离子的迁移率。然后可以将这些结果转化为一个扩散 - 反应方案，特别引入可移动离子的分数，或等效地引入分配系数Kd。该系数在表征多孔材料中的电动现象时非常重要。
