Dispersion clays

Other interesting Langmuir monolayer systems include spread thermotropic liquid crystals where a foam structure forms on expansion from a collapsed state [23]. Spread monolayers of clay dispersions form a layer of overlapping clay platelets that can be subsequently deposited onto solid substrates [24]. 

Prepared saltwater completion fluids are made of fresh surface water, with sufficient salts added to produce the proper salt concentration. Usually, the addition of 5 to 10% NaCl, 2% CaClj, or 2% KCl is considered satisfactory for clay inhibition in most formations. Sodium chloride solutions have been extensively used for many years as completion fluids these brines have densities up to 10 Ib/gal. Calcium chloride solutions may have densities up to 11.7 lb/ gal. The limitations of CaClj solutions are (1) flocculation of certain clays, causing permeability reduction, and (2) high pH (10 to 10.5) that may accelerate formation clays dispersion. In such cases, CaC12-based completion fluids should be replaced with potassium chloride solutions. Other clear brines can be formulated using various salts over wide range of densities, as shown in Figure 4-123 [28]. 

Soils properties are very sensitive to the type of exchangeable ions. Calcium imparts favorable physical properties to the soil, while adsorbed sodium causes clay dispersion and swelling. It is generally recognized that an exchangeable sodium percentage of 10 is sufficient to cause soil dispersion, reduction of soil permeability and impaired growth of some crop plants. On the other hand, excess salt concentration prevents the dispersive effect of adsorbed sodium. 

Carbon black is reinforced in polymer and mbber engineering as filler since many decades. Automotive and tmck tires are the best examples of exploitation of carbon black in mbber components. Wu and Wang [28] studied that the interaction between carbon black and mbber macromolecules is better than that of nanoclay and mbber macromolecules, the bound mbber content of SBR-clay nanocompound with 30 phr is still of high interest. This could be ascribed to the huge surface area of clay dispersed at nanometer level and the largest aspect ratio of silicate layers, which result in the increased silicate layer networking [29-32]. 

The properties of filtrate reducers contribute to their different molecular structures. Nonionic filtrate reducers work by completely blocking the filter-cake pore, and anionic ones work by increasing the negative-charge density of filter-cakes and decreasing pore size. Anionic species cause further clay dispersion, but nonionic species do not, and both of them are beneficial to colloid stability [1890]. 

Clogging of aquifers by the growth of biomass is an operational problem. The permeability of an aquifer could be reduced due to the precipitation of biomass sludges and chemicals, or due to clay dispersion. 

Blending vegetable oils Blending gasoline Clay dispersion Fermentation (pharmaceutical) Suspension polymerization Emulsion polymerization Solution polymerization... 

Gray, D.H. Rex, R.W. "Formation Damage in Sandstones Caused by Clay Dispersion and Migration", 1966 Fourteenth National Conference on Clays and Clay Minerals, 355-366. 

Soil-pH may influence both the concentrations of ions in the soil solution and the charge characteristics of the clay. Dispersion of clays is thus, to some extent, a pH-dependent process. At soil-pH(H2o,i i) values below 5, the aluminum concentration of the soil solution is normally sufficiently high to keep clay flocculated (Al3+ is preferentially adsorbed over divalent and monovalent ions in the soil solution). Between pH 5.5 and 7.0, the content of exchangeable aluminum is low . If concentrations of divalent ions are low, clay can disperse. At still higher pH values, divalent bases will normally keep the clay flocculated unless there is a strong dominance ofNa+-ions in the soil solution. 

The presence of biosurfactants in that bioliqour appear to render favorable results in terms of decreasing the amount of wastes and conditions employed in conventional processes, such as caustic soda treatment. In comparison, lower temperatures and no need of caustic soda are clear advantages, and consequently the present invention is said to avoid the production of clay dispersion sludges. 

The non-linear response of plastic materials is more challenging in many respects than pseudoplastic materials. While some yield phenomena, such as that seen in clay dispersions of montmorillonite, can be catastrophic in nature and recover very rapidly, others such as polymer particle blends can yield slowly. Not all clay structures catastrophically thin. Clay platelets forming an elastic structure can be deformed by a finite strain such that they align with the deforming field. When the strain... 

Another possibility is that adsorption of a monovalent cation, in this case K+, causes some clay dispersion and some movement of clay (especially those particles with K selective sites) down the profile (35). 

Evaluation of the Copolymers The polymer solutions were evaluated for their deposit control and dispersant activities. The tests included calcium phosphate inhibition, calcium carbonate inhibition, iron oxide dispersion, and clay dispersion. The procedures for these tests have been previously reported (12). A commercially available polyacrylic acid was also tested for comparison. The results are shown in Tables II to V. 

Dispersant Activity Tests were conducted utilizing iron oxide and clay suspensions in order to establish the efficacy of the copolymers as dispersants for suspended particulate matter. Kaolin clay was used for the clay dispersion study. According to the procedure, separate 0.1% iron oxides and 0.1% clay suspensions in... 

The amount of adsorbed chemical is controlled by both properties of the chemical and of the clay material. The clay saturating cation is a major factor affecting the adsorption of the organophosphorus pesticide. The adsorption isotherm of parathion from an aqueous solution onto montmorillonite saturated with various cations (Fig. 8.32), shows that the sorption sequence (Al > Na > Ca ) is not in agreement with any of the ionic series based on ionic properties. This shows that, in parathion-montmoriUonite interactions in aqueous suspension, such factors as clay dispersion, steric effects, and hydration shells are dominant in the sorption process. In general, organophosphorus adsorption on clays is described by the Freundhch equation, and the values for parathion sorption are 3 for Ca +-kaoUnite, 125 for Ca -montmorillonite, and 145 for Ca -attapulgite. 

Lima, J.M., Anderson, S.J. Curi, N. (2000) Phosphate-induced clay dispersion as related to aggregate size and composition in haplu-doxs. Soil Sci. Soc. Am.J. 64 892-897... 

C. additional superfine particles in the cement paste. These are materials consisting of acrylic emulsions and aqueous clay dispersions. 

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

NMR measurements is performed by numerical simulations with a multi-scale modelling [11] of the structure of the clay dispersions and the diffusion of the water molecules or the sodium counterions, by using Brownian Dynamics in order to bridge the gap between the time scale accessible by Molecular Dynamics (typically a few ps) and that explored by the NMR measurements (from ns to ms). 

The correlation between the structure of the clay dispersions and the water mobility is investigated by the use of the self-diffusion propagator Ps(fA f, 0), i.e. the probability density of finding at time A and position f a diffusing probe initially located at a position r ... 

Porion, P., Faugere, M.P., Lecolier, E., Gherardi, B. and Delville, A. (1998) 23Na Nuclear Quadrupolar Relaxation as a Probe of the Microstructure and Dynamics of Aqueous Clay Dispersions An Application to Laponite Gels. The Journal of Physical Chemistry B 102, 3477-3485... 

In modem practice the terms lyophilic and lyophobic (especially hydrophilic and hydrophobic) are often used to characterize surfaces, in addition to colloidal dispersions. This sometimes leads to confusing usage. For example, a clay dispersion in water could be classified as a lyophobic colloid with hydrophilic surfaces. 

Figure 1.3. The microstructure of clay dispersed in the polymer matrix (a) conventional composite (b) extended polymer chains intercalated between the silicate layers, resulting in a well-ordered multilayer with alternation polymer/inorganic layers, and (c) silicate layers (1 nm thickness) exfoliated and dispersed in a continuous polymer matrix.

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