Hydrated smectite

Laird DA, Barriuso E, Dowdy RH, Koskinen WC (1992) Adsorption of atrazine on smectites. Soil Sci Soc Am J 56 62-67 Laird DA, Fleming PD (1999) Mechanisms for adsorption of organic bases on hydrated smectite surfaces. Environ Toxicol Chem 18 1668-1672 Lambert SM (1967) Functional relationship between sorption in soil and chemical structure. J Agric Food Chem 15 572-576 Lambert SM (1968) Omega, a useful index of soil sorption equilibria. J Agric Food Chem 16 340-343... 

For the relatively rapid anisotropic motion (tc < 3 x 10" s) of spin probes observed on fully hydrated smectites such as montmoril-lonite, hectorite, and beidellite, an external fixed axis system (x1, y, z ) can be defined in addition to the molecule-fixed axes (x, y, z). The angle, 0, between the z and z axes is given by ... 

Figure 21.5 Possible interactions between hydrated smectite surfaces and a chlom-.v-triazine. (See Color Plate Section.)...

Laird, D.A. and P.D. Fleming (1999). Mechanisms for adsorption of organic bases on hydrated smectite surfaces. Environ. Tox. Chem., 18 1668-1672. 

Plate 6 Possible interactions between hydrated smectite surfaces and a chloro-s-triazine. 

MC and MD studies of hydrated smectites with monovalent counterions Li+, Na+, K+, Cs+ were also performed [62, 63, 69, 70, 72, 77-80], An increase of the simulation cell size of 2 1 Na-saturated clay or alternation of its shape from rectangular did not have a significant effect on the calculated interlayer properties [70]. It has been revealed that the mechanism of swelling and hydration depends upon the interlayer ion charge. Also the greater role of the clay mineral surface in organizing interlayer water in the case of K-montmorillonite with a weakly solvating counterion was concluded [64, 68]. 

Saturated bentonite consists of hydrated smectite minerals, mainly montmorillonite, and quartz particles, called the macro-grain. See a schematic diagram of the microstructure given in Figure 1. 

Figure 6. Microscale unit cell for hydrated smectite (corresporuling to the microscale problem I in Figure 5).

SMECTITE GROUP MINERALS. The structuTe of Water adsorbed by smectite group minerals has been studied extensively in both its static (D structure) and dynamic aspects. As with water molecules on vermiculite, the behavior of water on smectite surfaces is conditioned sensitively on the type of exchangeable cation and on the location of isomorphic cation substitutions in the layer structure. In many respects, a discussion of the configuration of water molecules hydrating smectites is parallel to that for vermiculite. 

Degradation of Tetraphenylboron at Hydrated Smectite Surfaces Studied by Time Resolved IR and X-ray Absorption Spectroscopies... 

Polyvinyl butyral Potassium polyacrylate Potassium silicate Potato (Solanum tuberosum) starch, Quaternium-18 bentonite Quaternium- 18/benzalkonium bentonite Quaternium-18 hectorite Rhodapon CAV Shellac, Silica, amorphous hydrated. Silica dimethyl sllylate Silica, hydrated Smectite Sodium chloride Sodium hydrosulfite Sodium magnesium fluorosilicate Sodium polyacrylate Sodium polymelhacrylate Sodium polystyrene sulfonate Sodium slllcoaluminate Sodium stearate Sodium sulfate Stannic oxide Stearalkonlum bentonite Stearalkonium hectorite Stearamide, Stearamide MEA-stearate Stearyl alcohol, Stearyl stearate, Synthetic wax, Tallamide DEA, Tetradecylelcosanol Tetrasodium etidronate Tridecyl alcohol Tridecyl stearate Trihydroxystearin, Trilinoleicacid, Tristearin, Urea-formaldehyde resin. Wheat (Triticum vulgare) starch Xanthan gum. Zinc laurate... 

Fig. 2. Polycation not hydrated smectite clays and hydrated with sodium.

Transferable potential development for hydrated smectite, interlayer structure of water and cations... 

There is a great interest in the nature of the interface between water and silicate minerals (see for example Davis and Hayes (1986)). Much of the chemical activity in soils, sediments and porous rocks occurs at such an interface. Experimentally, it is very difficult to examine this interface because it is such a small part of the liquid-solid system. Hydrated smectites and vermiculites have water between all of the silicate layers and therefore the percentage of the sample which is interface is enormously larger than the interface between, for example, a grsin of quartz in contact with liquid water. Another way to look at this is that the surface are of a quartz sand is probably much less than 1 m gram while a typical smectite has a surface area of as much as 800 m /gram. For these, and other reasons, intercalated clays have been extensively studied. 

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