Rinnert Emmanuel, Carteret Cedric, Humbert Bernard, Fragneto-Cusani Giovanna, Ramsay John D F, Delville Alfred, Robert Jean-Louis, Bihannic Isabelle, Pelletier Manuel, Michot Laurent J
Agence Nationale pour la gestion des Déchets RAdiocatifs, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Chatenay Malabry CEDEX, France.
J Phys Chem B. 2005 Dec 15;109(49):23745-59. doi: 10.1021/jp050957u.
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.
研究了水与层电荷为每晶胞1个（0.165 C m⁻²）的合成皂石粘土样品之间的相互作用，通过跟踪相对压力范围从10⁻⁶至0.99内的水吸附和解吸过程来进行研究：（i）采用重量法和近红外技术测定吸附量；（ii）在可控水压下，通过X射线和中子衍射测定层间水分子的基面间距和排列；（iii）在可控水压下，通过近红外（NIR）和拉曼光谱测定吸附水分子的分子结构和相互作用。将由此获得的结果与巨正则蒙特卡罗（GC/MC）模拟结果进行对比。采用这种方法，可以区分出各种明显不同的水化范围。在最初的两个范围内，在低水相对压力下，吸附仅发生在外表面，无膨胀现象。下一个范围对应于水分子在层间阳离子周围的吸附，而阳离子并未从其位于四面体层三角双锥腔顶部的位置移开，且伴有有限的膨胀。在接下来的范围内，阳离子向层间中部区域移动。由此达到约12.3 Å的层间间距，这对应于经典意义上所谓的“单层水合物”，而层间区域不存在水层状况。下一个水化范围对应于层间以近乎恒定的间距填充。这导致形成一个组织良好的层间水分子网络，与粘土层有显著相互作用。如此形成的结构导致D₂O中子衍射图谱中的d₀₀₁线完全消失，通过直接使用GC/MC得出的分子构型可对其进行正确模拟。下一个范围（0.50 < P/P₀ < 0.80）对应于结构的最终膨胀，以达到15.2 Å的d间距值（通常称为“双层水合物”）。这与比体相水结构更有序的类液态水分子网络的发展相关。高相对压力下的最终水化范围主要对应于粘土颗粒间孔隙的填充。
