Hydration of a synthetic clay with tetrahedral charges: a multidisciplinary experimental and numerical study.
Hydration of a synthetic clay with tetrahedral charges: a multidisciplinary experimental and numerical study.
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DOI：
10.1021/jp050957u
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发表时间：
2005-12
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影响因子：
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通讯作者：
E. Rinnert;C. Carteret;B. Humbert;G. Fragneto-Cusani;J. Ramsay;A. Delville;J. Robert;I. Bihannic;M. Pelletier;L. Michot
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文献类型：
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作者：
E. Rinnert;C. Carteret;B. Humbert;G. Fragneto-Cusani;J. Ramsay;A. Delville;J. Robert;I. Bihannic;M. Pelletier;L. Michot
在相对压力为10-6~0.99的范围内，对层电荷为0.165 Cm(-2)的合成皂石粘土样品与水的相互作用进行了跟踪研究：(1)用重量法和近红外法测定了水的吸附量；(2)用X-射线和中子衍射法研究了层间水分子在受控水压作用下的基本距离和排列；(3)用近红外和拉曼光谱研究了受控水压作用下吸附的水分子的分子结构和相互作用。所得结果与大正则蒙特卡罗(GC/MC)模拟结果吻合较好。利用这种方法，可以区分各种不同的水化范围。在前两个范围内，在较低的水相对压力下，吸附只发生在外表面，没有相关的膨胀。下一个范围对应于层间阳离子周围的水分子的吸附，而不是将其从四面体层的双三角空腔顶部的位置移除，并且与有限的膨胀有关。在以下范围内，阳离子向中间层间区移动。这样达到的片层间距约为12.3A，对应于经典所说的“单层水合物”，而在层间区域不存在水层。下一个水化范围对应于以几乎恒定的间距填充夹层。这导致形成了一个组织良好的层间水分子网络，与粘土层有显著的相互作用。这样形成的结构导致D2O中子衍射图中的D001谱线完全消失，而D2O中子衍射图是直接用GC/MC得到的分子组态正确模拟的。下一个范围(0.50<；P/P0<；0.80)对应于结构的最终膨胀，达到15.2A的d间隔值(通常被称为“两层水合物”)。它与比散装水更有结构的液态水分子网络的发展有关。高相对压力下的最终水化范围主要对应于粘土颗粒之间的孔隙填充。
The interaction of water with a synthetic saponite clay sample, with a layer charge of 1 per unit cell (0.165 C m(-2)), was investigated by following along water adsorption and desorption in the relative pressure range from 10(-6) to 0.99 (i) the adsorbed amount by gravimetric and near-infrared techniques, (ii) the basal distance and arrangement of water molecules in the interlayer by X-ray and neutron diffraction under controlled water pressure, and (iii) the molecular structure and interaction of adsorbed water molecules by near-infrared (NIR) and Raman spectroscopy under controlled water pressure. The results thus obtained were confronted with Grand Canonical Monte Carlo (GC/MC) simulations. Using such an approach, various well-distinct hydration ranges can be distinguished. In the two first ranges, at low water relative pressure, adsorption occurs on external surfaces only, with no swelling associated. The next range corresponds to the adsorption of water molecules around the interlayer cation without removing it from its position on top of the ditrigonal cavity of the tetrahedral layer and is associated with limited swelling. In the following range, the cation is displaced toward the mid-interlayer region. The interlamellar spacing thus reached, around 12.3 A, corresponds to what is classically referred to as a "one-layer hydrate," whereas no water layer is present in the interlayer region. The next hydration range corresponds to the filling of the interlayer at nearly constant spacing. This leads to the formation of a well-organized network of interlayer water molecules with significant interactions with the clay layer. The structure thus formed leads to a complete extinction of the d001 line in D2O neutron diffraction patterns that are correctly simulated by directly using the molecular configurations derived by GC/MC. The next range (0.50 < P/P0 < 0.80) corresponds to the final swelling of the structure to reach d spacing values of 15.2 A (usually referred to the "two-layer hydrate"). It is associated with the development of a network of liquidlike water molecules more structured than in bulk water. The final hydration range at high relative pressure mainly corresponds to the filling of pores between clay particles.