Position of Shear Plane at the Clay–Water Interface: Strong Polarization Effects of Counterions
Position of Shear Plane at the Clay–Water Interface: Strong Polarization Effects of Counterions
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DOI：
10.2136/sssaj2016.08.0261
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发表时间：
2017-03
影响因子：
2.9
通讯作者：
Xinmin Liu;Wuquan Ding;R. Tian;Wei Du;Hang Li
中科院分区：
文献类型：
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作者：
Xinmin Liu;Wuquan Ding;R. Tian;Wei Du;Hang Li
剪切面处的ζ电位是固 - 液界面的一个重要电化学参数。然而，由于忽略了一个相当重要的效应——双电层中的强离子极化，很难准确确定剪切面的位置。在本研究中，基于修正的泊松 - 玻尔兹曼方程建立了一个考虑离子极化的剪切面位置估算模型，并通过离子交换平衡实验量化了恒电荷表面的极化强度。在蒙脱石 - 水界面，极化效应使Na⁺的有效离子电荷从1增加到1.082，K⁺的有效离子电荷从1增加到1.498，这导致滑动层厚度减小。膨胀压力的理论预测与实验测量结果高度吻合。该理论观点也为物理化学中最古老的谜题之一——特异性离子效应提供了新的思路。
The zeta potential at the shear plane is an important electrochemical parameter at solid–liquid interfaces. However, it is difficult to accurately determine the position of the shear plane because a rather important effect— strong ion polarization in the electrical double layer—is neglected. In the present study, a model for estimation of the shear plane position considering ion polarization was developed based on the modified Poisson–Boltzmann equation, and the intensity of polarization on a constantly charged surface was quantified through an ion exchange equilibrium experiment. The polarization effects increased the effective ionic charges of Na⁺ from 1 to 1.082 and that of K⁺ from 1 to 1.498 at the montmorillonite–water interface, which resulted in decreasing the thickness of the slipping layer. The theoretical prediction of the swelling pressure was in excellent agreement with the experimental measurements. The theoretical standpoint also sheds new light on one of the oldest puzzles in physical chemistry—specific ion effects.