ADSORBED WATER ON CLAY: A REVIEW
ADSORBED WATER ON CLAY: A REVIEW
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DOI：
10.1346/ccmn.1960.0090104
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发表时间：
1960-02
影响因子：
2.2
通讯作者：
R. T. Martin
中科院分区：
文献类型：
--
作者：
R. T. Martin
摘要目前对粘土矿物学的认识和粘土行为概念的改变，建议重新审查有关吸附水的实验数据。对1935年至1959年发表的数据进行了研究和评价。在某些情况下，这需要对数据进行重新解释，这可能会导致原作者无意的推论或结论。重新评估数据的目的是澄清对吸附水性质的理解，并为未来的研究提出富有成效的途径。虽然没有包括所有关于这一主题的文献，但已经做出了协调一致的努力，包括来自所有观点和实验方法的代表性数据。数据审查来根据以下标题：X射线和电子衍射，密度，介电和磁性，热力学，扩散和流体流动，冻结，和刚性水膜。利用现有的晶体和粘土表面化学的知识，导致以下结论：（a）吸附水分子的氧原子的位置已经建立了由X射线衍射的蛭石。这些位置排除了冰结构和Hendricks-Jefferson网结构，即使在修改以容纳可交换离子之后也是如此。（B）在0.7 g H2O/g粘土的水含量（近似塑性极限）下，吸附在Na蒙脱石上的水的密度具有约0.97 g/cm 3的最小值。对于小于0.7的水含量，密度迅速上升到约1.4，而对于大于0.7的水含量，密度逐渐上升，直到约6.5g H2O/g粘土，吸附水的密度等于正常液态水的密度。(c)高岭石上吸附的水的微分熵有一个近似于冰的最小值;然而，（1）这个最小值出现在约0.7的单分子层处，（2）积分熵大于正常液态水的积分熵，直到至少两个分子层。蒙脱石粘土上吸附水的明显矛盾熵尚未得到解决，但被认为至少部分与粘土膨胀有关。(d)扩散和流体流动现象被证明是非常敏感的粘土织物，因此，这是笔者的意见，扩散和流体流动数据松散压实粘土是没有什么帮助，在确定结构的吸附水相。(e)被吸附的水很容易过冷，并且在冰一旦形成之后，相当大一部分被吸附的水保持不冻结。这两个主要假说表明，吸附水的性质是：（1）固体状物质，或（2）二维流体。笔者认为，这两种假说都不能充分解释的唯一数据是高岭石的积分熵数据。积分熵数据支持二维流体假设;然而，数据的缺乏要求这是一个非常试探性的结论。在重新检查数据的审查中遇到的主要困难是，一个相当不明确的粘土表面是由不同的研究人员。如果要在解开水-粘土复合体方面取得进展，就必须在非常仔细定义和控制的粘土表面上进行实验。从水-粘土系统的物理化学数据中解释的吸附水的性质并不比粘土表面的纯度好，无论测量的准确性和精密度如何。
ABSTRACT Current knowledge of clay mineralogy and changing concepts of clay behavior have suggested a re-examination of the experimental data concerning adsorbed water. Data published between 1935 and 1959 have been studied and evaluated. In some instances this requires a reinterpretation of data that may lead to inferences or conclusions not intended by the original author. The intention of the re-evalution of data is to clarify understanding of the nature of adsorbed water and to suggest fruitful avenues for future research. While all literature on the subject has not been included, a concerted effort has been made to include representative data from all viewpoints and experimental methods. Data reviewed come under the following headings: X-ray and electron diffraction, density, dielectric and magnetic, thermodynamic, diffusion and fluid flow, freezing, and rigid water films. Utilizing present knowledge of crystal and surface chemistry of clay leads to the following conclusions: (a) Positions of the oxygen atoms of the adsorbed water molecules have been established by X-ray diffraction of vermiculite. These positions preclude both the ice structure and the Hendricks-Jefferson net structure even after modification to accommodate the exchangeable ions, (b) Density of water sorbed on Na montmorillonite has a minimum value of about 0.97 g/cm3 at a water content of 0.7 g H2O/g clay (approximately the plastic limit). For water contents less than 0.7 the density rapidly rises to about 1.4, and for water contents greater than 0.7 the density gradually rises until at about 6.5 g H2O/g clay the density of the adsorbed water equals that of normal liquid water. (c) The differential entropy of water adsorbed on kaolinite has a minimum value approximately that of ice; however, (1) this minimum occurs at about 0.7 of a monolayer, and (2) the integral entropy is greater than that for normal liquid water up to at least two molecular layers. The apparently contradictory entropy of sorbed water on montmorillonitic clay has not been resolved but is believed to be at least partially associated with clay swelling. (d) Diffusion and fluid flow phenomena are shown to be extremely sensitive to clay fabric; therefore, it is the writer's opinion that diffusion and fluid flow data on loosely compacted clay are of little help in ascertaining the structure of the adsorbed water phase. (e) Adsorbed water is easily supercooled and an appreciable fraction of the adsorbed water remains unfrozen after ice has once formed. The two major hypotheses indicate that the nature of the adsorbed water is: (1) a solidlike substance, or (2) a two-dimensional fluid. In the writer's opinion the only data that cannot be adequately explained by both of the hypotheses are the integral entropy data on kaolinite. The integral entropy data favor the two-dimensional fluid hypothesis; however, the paucity of data requires that this be a very tentative conclusion. The major difficulty encountered in the re-examination of data for this review was that a, rather poorly defined clay surface was employed by various investigators. If progress is to be made in unraveling the water-clay complex, it is deemed absolutely essential that experiments be carried out on very carefully defined and controlled clay surfaces. The nature of adsorbed water as interpreted from physico-chemical data on water-clay systems is no better than the purity of the clay surface regardless of the accuracy and precision of the measurements.