Clay coatings

It seems that clay translocation (argilluviation) from the upper into lower horizons takes place only to a limited extent in arid zone soils. B] horizons are only rarely identified. That limited argilluviation may indeed have taken place in some profiles is also indicated by the clay coatings (argillans) that were observed in subsurface horizons of some soils. Clay migration might possibly have been facilitated by the strong dispersion... 

The morphology of weathered feldspar surfaces, and the nature of the clay products, contradicts the protective-surface-layer hypothesis. The presence of etch pits implies a surface-controlled reaction, rather than a diffusion (transport) controlled reaction. Furthermore, the clay coating could not be "protective" in the sense of limiting diffusion. Finally, Holdren and Berner (11) demonstrated that so-called "parabolic kinetics" of feldspar dissolution were largely due to enhanced dissolution of fine particles. None of these findings, however, addressed the question of the apparent non-stoichiometric release of alkalis, alkaline earths, silica, and aluminum. This question has been approached both directly (e.g., XPS) and indirectly (e.g., material balance from solution data). 

Studies of the sorption of natural radionuclides from groundwater have established that minor minerals, such as clays coating the fractures in crystalline rock and Fe- and Mn-oxyhydroxides, are important sinks for radionuclides. For example, investigations carried out at the Aspo facility (Smellie Karlsson 1999) showed qualitatively that rare earth elements (REEs), Sc, Th, U, Ra, and Ba have been scavenged by Fe-oxyhydroxide and calcite precipitates,... 

CA 57, 2490(1962) [An expl prepd from clay-coated fertilizer-grade AN by heating and agitating it. with a combustible material which... 

Ammonium nitrate is hygroscopic clay coatings and moisture-proof bags are used to preclude spoilage in storage and transportation. 

Boxboard General term designating the paperboard used for fabricating boxes. It may be made of wood pulp or paper stocks or any combinations of these and may be plain, lined, or clay coated. Terminology used to classify boxboard grades is normally based... 

Figure 9.9 Thin-section micrograph (PPL) of a pore in the 72-80-cm depth horizon from Bagnoli soil completely covered by dark clay coatings and potentially toxic metals (PTMs j quantification (mg kg ) in the coatings as determined by the wavelength dispersive spectroscopy (WDS) (average of 40 points around the pore) (from Adamo et al., 2002a).

Figure 4. Photomicrograph (7200X) of 28 clay coated paper surface. Longer of two lines represents lp.

Sample 7 - packaging for crispbread Clay coated paper... 

Inequality 11 was substituted into Equation 8, together with reasonable values of other parameters and 0.1 cm < a < 0.2 cm as a was found to be in this study. This leads to the conclusion that, for systems in which r is less than 0.1 cm, the local equilibrium assumption is applicable (i.e., q is sufficiently small) when D is nearly equal to as observed in the experiments. In soils in which the exchanging particles are not spherical, r would represent approximately the mean diffusion path within clay aggregates or within clay coatings on coarse particles. 

The difficulties imposed by clay coatings on quartz nucleation probably explain why there are few reports of quartz cementation in shales. The oxygen in quartz silt is isotopically heavy (8 0 = 19%o) compared to sand-size quartz (5 0 = 14%o) (Blatt, 1987) suggesting that a substantial component of relatively low-temperature quartz resides in shales. The application of cathodoluminescence microscopy to shales has been quite limited. In Frio Formation shales of south Texas no convincing quartz cement is observed across a range of depths in which quartz cementation becomes important in associated... 

Komori and Nonaka [499] reported the first example of an electrochemical enantiomer-differentiating reaction When racemic 2,2-dimethyl-1-phenyl-1-propanol was oxidized at a poly(L-valine)-coated anode, 43% optically pure (S)-(—)-2,2-dimethy 1-1-phenyl-1-propanol was recovered as an unreacted part. Yamagishi and Aramata [500] also found electrooxidative optical resolution of a racemic Co(l,10-phenathroline)3 complex by a chiral clay-coated anode, and Yoshinaga and coworkers [501] electrore-ductively resolved racemic Co(acetylacetonato)3 by using optically active supporting electrolytes. 

Today, clay adsorption or hydrogen treating (catalytic hydrogenation) are used to accomplish decolorization [35]. Passage of oil through a clay coating on a continuous filter is quite effective and is suitable for small refineries. 

LDPE coating to polyester film, clay-coated liner board, and aluminum foil was improved by an addition of calcium carbonate. Adhesion increases as the amount of calcium carbonate is increased and at a 30% level it is doubled. The adhesion of SBR to a polyurethane adhesive was substantially improved (400%) by the addition of silica but only when the surface was roughened. The amount of silica did not affect adhesion of unroughened SBR. The use of MgO with silane coupling increased adhesion of bromobutyl liner by a factor of four. Generally, in the reported data, surface roughening of the filled composite contributes to a better adhesion to other substrates joined by adhesives. 

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