Clay-water systems

Plasticity in clay—water systems is caused by a bonding force between the particles and water which acts as a lubricant and permits some movement between the particles under the apphcation of a deforming force. The bonding force is in part a result of the charges on the particles (see Clays, survey). 

Our approach has been to study a very simple clay-water system in which the majority of the water present is adsorbed on the clay surfaces. By appropriate chemical treatment, the clay mineral kao-linite will expand and incorporate water molecules between the layers, yielding an effective surface area of approximately 1000 m2 g . Synthetic kaolinite hydrates have several advantages compared to the expanding clays, the smectites and vermiculites they have very few impurity ions in their structure, few, if any, interlayer cations, the structure of the surfaces is reasonably well known, and the majority of the water present is directly adsorbed on the kaolinite surfaces. 

Van Bladel, R., Gavine, G., and Laudelout, H., "A Comparison of the Thermodynamics Double Layer Theory, and Empirical Studies of the Na-Ca Exchange Equilibria in Clay Water Systems," Proc. Inter. Clay. Conf., Madrid, Spain, (1972), 385. 

Van der Waals interactions are noncovalent and nonelectrostatic forces that result from three separate phenomena permanent dipole-dipole (orientation) interactions, dipole-induced dipole (induction) interactions, and induced dipole-induced dipole (dispersion) interactions [46]. The dispersive interactions are universal, occurring between individual atoms and predominant in clay-water systems [23]. The dispersive van der Waals interactions between individual molecules were extended to macroscopic bodies by Hamaker [46]. Hamaker s work showed that the dispersive (or London) van der Waals forces were significant over larger separation distances for macroscopic bodies than they were for singled molecules. Through a pairwise summation of interacting molecules it can be shown that the potential energy of interaction between flat plates is [7, 23]... 

Van Bladel, R., G. Gavira, and H. Laudelout. 1972. A comparison of the thermodynamic, double-layer theory and empirical studies of the Na-Ca exchange equilibria in clay water systems. Proc, Int. Clay Conf. 385-398. 

Even dynamic measurements have been made on mixtures of carbon black with decane and liquid paraffin [22], carbon black suspensions in ethylene vinylacetate copolymers [23], or on clay/water systems [24,25]. The corresponding results show that the storage modulus decreases with dynamic amplitude in a manner similar to that of conventional rubber (e.g., NR/carbon blacks). This demonstrates the existence and properties of physical carbon black structures in the absence of rubber. Further, these results indicate that structure effects of the filler determine the Payne-effect primarily. The elastomer seems to act merely as a dispersing medium that influences the magnitude of agglomeration and distribution of filler, but does not have visible influence on the overall characteristics of three-dimensional filler networks or filler clusters, respectively. The elastomer matrix allows the filler structure to reform after breakdown with increasing strain amplitude. 

Presence of structural charges and their effects on the electric potential at both the basal and edge surfaces. This is the main difference between a clay-water system and a metal oxide-water system, which in principle contains no structural charges. 

Thompson, H. A., Parks, G. A., and Brown, G. E., Jr., (1999b). Dynamic interactions of dissolution, surface adsorption, and precipitation in an aging cobalt(II)-clay-water system. Geochim. Cosmochim. Acta 63, 1767-1779. 

The simple models of cation exchange presented here have not yet considered as a competing cation, even though it is always present in clay-water systems. cations are produced by water dissociation or, more importantly (because carbonic acid is more acidic than water), by the dissociation of carbonic acid formed from the dissolution of CO2 in water ... 

It can be inferred from the osmotic model of clay swelling (discussed in the previous section) that any influence on the clay-water system that lowers the free energy of water in the aqueous phase will reduce clay swelling. As seen earlier, high salt... 

A variety of other plausible electrode reactions could be invoked (some perhaps arising from trace impurities in the clay/water system or corrosion reactions at the electrodes) to account for the existence of EOD at low applied voltages, (e.g., 1 V). 

The Donnan equilibrium theory implies that dilution of a clay/water system containing monovalent and divalent cations displaces the equilibrium in such a manner that the absorption of divalent ions increases, whereas the absorption of monovalent ions decreases. The ionic charge is not the only determining factor in the absorption effect. Factors such as temperature, pH, and specific ions also play important roles. Hydration energy, which appears to be one of the most important factors for the absorption and fixation of cations, displaces the ionic equilibria in a manner opposing the Donnan equilibrium theory. According to Sawhney (1972), "cations with low hydration energy such as Ca, Mg and Sr, produce expanded interlayers and are not fixed". 

Cations to Diffusion in Clay-Water Systems, Soil Sci. Soc. Am. Proc. (1966) 30, 17-22. 

In an NPT (constant mass, pressure and temperature) ensemble of clay-water systems the Gibbs free energy, G, is related to the partition function, Q, by the formula ... 

In our current work, expectation values of exp(-AV/ 7) are calculated by performing MD simulations (50 ps with a 0.5 fs time step) at individual steps defined by A. = i(AX). It was determined that in order to establish an ensemble of clay/water systems at each step, it was sufficient to select several hundred ( 400) instantaneous molecular configurations at random from the second half of each MD run. The collection of molecular configurations in each ensemble was then used to compute, according to Eq. [16], AG for each subinterval (X + 5A or A - 8A,) along the mutation path. 

Deflocculation. Soluble silicates suppress the formation of ordered structures within clay slurries, thus increasing the solids which can be incorporated into a clay water system. This interesting surface phenomenon finds practical expression in the manufacture of bricks and cement. 

Hydrolysis mechanisms in clay-water systems also can be dependent on the nature of the exchangeable cation. For example, Pusino et al. (1988) studied the catalytic hydrolysis of quinalphos on homoionic bentonite clays. On the Na- and K-clays, deethylation occurred, resulting in the formation of O-ethyl O-quinoxalin-2-yl thiophosphoric acid, whereas 2-hydroxyquinoxaline is the main reaction product on the Cu-, Fe- and Al-clays. 

Karickhoff, S. W., and G. W. Bailey. 1976. Protonation of organic bases in clay-water systems. Clays and Clay Minerals, 24 170-176. 

Suspensions in general, and particularly those of clay, do not behave like true liquids, and the laws governing their flow are quite different. The laws of viscous flow are dealt with elsewhere and we shall only introduce some elementary ideas here, sufficient to understand the technology of casting slips and other clay-water systems. 

F. Franks. Water A Comprehensive Treatise, Plenum Press, New York, 1972-1981. The seven volumes of this encyclopedic reference work that have appeared thus far contain discussions of all aspects of the chemistry and physics of liquid water and aqueous solutions. Of special interest are the chapters on bulk liquid water (Vol. 1), on water in electrolyte solutions (Vols. 3 and 6), and on clay-water systems, (Vol. 5). 

Most of the best pickings in recent years could be found in English-language literature, e.g., in works on plasticity by N.F. Astbury or H.H. Macey, in the empirical works of F.J. Goodson [14] and, above all, in the educational film that H.R. Hodgkinson made for the British Ceramic Society in 1963 - a genuine classic [15]. I also consider Plasticity of Clay Water Systems [16] very useful as written by W.G. Lawrence for New York s Alfred University. 

Thanks to the plasticity of the clay-water system, a key characteristic of ceramic is that it can be cold-formed. This simple concept allows us to classify the different shaping techniques. There are three main forming processes, which are largely defined by the quantify of water in the ceramic bodies. These are ... 

White WA, Pichler E (1959) Water Sorption Properties of Clay Minerals. In III. State Geol Surv Circ No. 266, Champaign, 111 Johnson AL, Norton FH (1941) Fundamental Study of Clay n. Mechanism of Deflocculation in the Clay-Water System. J Amer Ceram Soc 24 189-203... 

Lawrence WG (1961) Clay-Water Systems. The Ceranuc Association of New York, Alfred University, New York... 

Handle F (1978) Contribution to the subject of plasticity in clay-water systems. J ZI Ziegelindustrie Internahonal vol 9 pp 472-476... 

Cohn, M. I.,Reducing particle size of clay and rheology control of clay-water systems, U.S. patent 3,348,778, Oct. 24, 1967, Appl. Mar. 4, 1966, to Mineral Industries Corp. 

The plasticity characteristics of a sediment is characterized by its consistency. Atterberg limits and related indexes are a function of many parameters drying (Casagrands, 1932), temperature, molding and grain size (White and Walton, 1937), surface area (Farrar and Coleman, 1967), and clay mineral composition (Seed et al., 1964). The main factors are those tied to the physicochemical properties of the clay-water system (Mourn and Rosenquvist, 1961 Soderblom, 1969). 

Compressibility and Permeability of Fine-Grained Marine Sediments 8.4.1 Sedimentation of a Clay-Water System... 

Miller, R.H., Overman, A.R., and Peverly, J.H. 1969. The absence of threshold gradients in clay-water systems. Soil Science Society of America Proceedings, 33(2) 183-187. 

FIGURE 35.2 The electrochemical effect on a fine particle in clay-water system. 

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