Water Structure and Dynamics in Smectites: X-ray Diffraction and 2H NMR Spectroscopy of Mg–, Ca–, Sr–, Na–, Cs–, and Pb–Hectorite

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• 作者：U. Venkateswara Reddy ; Geoffrey M. Bowers ; Narasimhan Loganathan ; Mark Bowden ; A. Ozgur Yazaydin ; R. James Kirkpatrick
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 28, 2016
• 年：2016
• 卷：120
• 期：16
• 页码：8863-8876
• 全文大小：585K
• 年卷期：0
• ISSN：1932-7455

文摘

Variable-temperature X-ray diffraction and ²H NMR spectroscopy of the smectite mineral, hectorite, containing interlayer Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Pb²⁺ equilibrated at 43% relative humidity (RH) and mixed with ²H₂O to form a paste provide a comprehensive picture of the structural environments and dynamics of interlayer ²H₂O and the relationships of these properties to interlayer hydration state, the hydration energy and polarizability of the cation, temperature, and the formation of ice-1h in the interparticle pores. The variation in basal spacing shown by the XRD data correlates well with the ²H NMR behavior, and the XRD data show for the first time in hectorites that crystallization of interparticle ice-1h causes a decrease in the interlayer spacing, likely due to removal of interlayer ²H₂O. The variation of the ²H NMR behavior of all the samples with decreasing temperature reflects decreasing frequencies of motion for the rotation of the ²H₂O molecules around their dipoles, reorientation of the ²H₂O molecules, and exchange of the ²H₂O molecules between interlayer sites coordinated to and not coordinated to the cations.