Montmorillonite particles

As indicated earlier, the isotherms in Figure 11.5 could be termed pseudo Type II isotherms, but we prefer the designation Type lib (see Figure 13.1). Such isotherms are given by either slit-shaped pores or, as in the present case, assemblages of platy particles. The fact that the montmorillonite particles are thin and flexible may be responsible for the closer proximity of the basal faces than in uncompacted kaolinite. 

The SEM picture shows two types of particles (1) lead enrichments without montmorillonite, and (2) montmorillonite particles with lead enrichment on it. The montmorillonite particles are much larger, their size can reach 10 pm, and their elemental SEM maps show even distributions of Al, Si, Mg, Fe, Ca, and O only the distribution of Pb shows spots with higher concentration (white spots in Figure 2.29). 

An vigorous CO2 hydrate dissociation was observed in frozen hydrate saturated samples after the pressure release in the pressure chamber. The hydrate coefficient decreased 1.5-3.0 fold in 30 minutes after a pressure drop to atmospheric values. The maximum decrease was observed in the sand sample with 14% of kaolinite particles, the minimum decrease in the sand sample with 7% montmorillonite particles with 17% of initial water content. In the course of time the intensity of CO2 hydrate dissociation in frozen samples dropped sharply with even a complete stop of the dissociation process as a consequence of gas the hydrates self-preservation effect at sub-zero temperatures A... 

Pore ice plays a particular role for the self-preservation effect in frozen soils Initial hydrate preservation apparently is helped by frozen pore water (not transformed into hydrate). Additional ice formation in the form of a film on the surface of gas-hydrate forming due to hydrate surface dissociation is expected to take place upon gas pressure release. Thus in the sample with 7% of montmorillonite particles (Win=17%), pore hydrate showed a higher stability after pressure release as a consequence of the greater ice content due to the freezing of remaining pore water (Figure 4).Our results clearly indicate that the hydrate content decreases on the expense of an increases of ice (Figure 5). 

The mineral composition of the soil will also influence the kinetics of gas hydrates dissociation in frozen soils. Our results show, that gas hydrate formations in pore space of samples with montmorillonite particles dissociate less markedly as compared to the samples with kaolinite admixture. This influence may be explained by microstructural specificities of pore hydrate saturated samples but undoubtedly requires additional micro-morphological studies for a full understanding. 

Figure 5.18 shows a schematic representation of montmorillonite particles in dispersions. This diagram helps us to distinguish between different types of flocculation. Figure 5.18a depicts internal mutual flocculation which is described in Figure 5.15. As a result of electrostatic and van der Waals forces between the edges and...

Figure 5.18, A schematic representation of montmorillonite particles in dispersion. [Adapted, by permission, from Miano F, Rabaioli M R, Coll. Surfaces, 84, Nos.2/3, 1994, 229-37.]...

Explain why soil feldspar particles tend to be larger than soil kaolinite particles and why both tend to be larger thau montmorillonite particles ... 

P. Bar-On, I. Shainberg, and I. Michaeli, Electrophoretic mobility of montmorillonite particles saturated with Na/Ca ions, J. Colloid Interface Sci. 33 471 (1970). R. D. Harter and G. Stotzky, X-ray diffraction, electron microscopy, electrophoretic mobility, and pH of some stable smectite-protein complexes. Sod Sci. Soc. Am. J. 37 116 (1973). S. L. Swartzen-Allen and E. Matijevi6, Colloid and surface properties of clay suspensions. II Electrophoresis and cation adsorption of montmorillonite, /. Colloid Interface Sci. 50 143 (1975). 

QUASICRYSTAL FORMATION. The mixing together of Na- and Ca-montmorillonite suspensions to produce an overall charge fraction of Na" on the clay particles below 0.1 results in a very rapid (less than 1 min) formation of quasicrystals from conversion of the Na-montmorillonite particles.This rapid conversion is necessarily mediated by a redistribu- tion of the exchangeable cations such that Na ions are relocated, as required, to the external surfaces of already-formed quasicrystals that contain Ca ions on their internal surfaces. The relocation probably involves replacement by Na of Ca " already on external surfaces since the latter ions are likely to have a higher mobility than Ca " adsorbed inside a quasicrystal. 

I. Shainberg and H. Otoh, Size and shape of montmorillonite particles saturated with Na/Ca ions (inferred from viscosity and optical measurements), Israel]. Chem. 6 251 (1968). L. L. Schramm and J.C.T. Kwak, Influence of exchangeable cation composition on the size and shape of montmorillonite particles in dilute suspension, Clays and Clay Minerals 30 40 (1982). 

In modern organisms, the continuous victimization of nucleobases is a well-known problem that is counteracted by sophisticated repair systems [167]. At the earliest steps of evolution, repair systems were absent, so the photodestruction of nucleobases could have hindered the selection of the first replicators. The photodestruction of nucleobases could be, however, prevented by radiation-absorbing templates. Many minerals can take up radiation energy from the adsorbed photoactive compounds. For example, montmorillonite particles have been shown to protect catalytic RNA molecules (hairpin ribozyme 1) from UV-induced damage ... 

Fire retardants used in polystyrene (PS) include montmorillonite clay, polytetrafluoro-ethylene (PTFE) [8], bromine-based flame retardants such as brominated bisphenol A [9], brominated phenyl oxide or tetrabromophthalic anhydride, or magnesium hydroxide [10,11]. Sanchez-Olivares and co-workers [12], in their study of the effect of montmorillonite clay on the burning rate of PS and PS-polyethylene terephthalate blends, showed that increased combustion rate accompanied the incorporation of montmorillonite particles in high-impact polystyrene (FlIPS) formulations. 

NCH Nylon-Clay Hybrid polyamide-6 with montmorillonite particles 0.1-0.2 run diameter nanometer composite developed by Toyota Research Corp. Ube Industries, LuL... 

As can be seen from Table II.5, in an aqueous medium with particles and surface with identical hydrophilicity (quartz particles on quartz surface, or kaolinite or montmorillonite particles, on No. 23 chemical glass), or with identical hydrophobicity (graphite particles on paraffin wax surface), the adhesion number reaches its highest values. The adhesion of hydrophobic surfaces in water, however, (graphite-paraffin wax) is stiU greater than that of hydrophilic surfaces (quartz-quartz). 

Figure 3.3 Schematic of curved montmorillonite particles (reproduced from Ref [8]).

At the same time, stabilization of illite and, especially, montmorillonite particles decreases with the change-over from the Na+ cation to those of K-i-and Ca.2+ because of the decrease in the height of the ion-electrostatic barrier. This results in the enlargement of micro aggregates in illite sediment (Fig. 5) and in montmorillonite tending to form a honeycomb micro structure (Fig. 6). 

In contrast to kaolinite, increasing electrolyte concentration sharply reduces the stability of illite and montmorillonite particles, which leads to their active coagulation even in a 1% suspension of these minerals. As a result, a continuous structural network is formed with medium-sized cells in illite (Fig. 7b) and large-sized ones in montmorillonite (Fig. 7c). 

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