Illite with kaolinite, 187 surface

Interpretation of the mechanisms of the hydrocarbon desorption reactions mentioned above was considered (31,291) with due regard for the possible role of clay dehydration. While this water evolution process is not regarded as a heterogeneous catalytic reaction, it is at least possible that water loss occurs at an interface (293) so that estimations of preexponential factors per unit area can be made. On this assumption, Arrhenius parameters (in the units used throughout the present review) were calculated from the available observations in the literature and it was found (Fig. 9, Table V, S) that compensation trends were present in the kinetic data for the dehydration reactions of illite (+) (294), kaolinite ( ) (293,295 298), montmorillonite (x) (294) and muscovite (O) (299). If these surface reactions are at least partially reversible,... 

E. Surfaces that exhibit weaker acid behavior (high pKJ show a stronger preference for heavy metals than hard metals in comparison to surfaces with stronger acid behavior (low pKa). For example, illite or kaolinite show a stronger preference for Cu2+ or Cd2+ than montmorillonite. 

The second example concerns the surface heterogeneity of clay minerals. Important problems, such as limited yield of oil recovery arising during oil exploitation, involve interaction of pore filling fluids with the minerals that form the reservoir walls. The clay minerals, due to their relatively high specific surface area and electrical charge density, are the most active for the retention of oil. Illites and kaolinites are the clay minerals that are most frequently found and their wettability properties are believed to be in relation to the heavy oil ends retention process. 

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY Nuclear magnetic resonance (NMR) spectroscopy can be applied to aqueous samples and can distinguish between inner- and outer-sphere ion surface complexes. The adsorption behavior of the cations Cs+ and Na" " was studied on the surfaces of silica, boehmite, kaolinite, and illite (Kim and Kirkpatrick, 1997). Cesium was adsorbed both as inner-and outer-sphere surface complexes and in the diffuse layer, while Na was adsorbed only as outer-sphere surface complexes and in the diffuse layer. The adsorbed Na ions were fully hydrated, while the Cs ions had direct contact with the surface oxygen atoms. 

The specific immersion wetting enthalpies of kaolinite, illite, and their organo-philic derivatives were investigated in methanol and benzene in our earlier publications [35,37,38]. These data reveal that the heat of immersion in methanol is the highest in the case of the dialyzed hydrophilic mineral, and with increasing surface modification its value decreases. The comparison of immersion wetting enthalpies relative to unit mass of the adsorbent is justified only when the specific surface area of the adsorbent is constant. It is also known, on the other hand, that the value of liquid sorption capacity, is a function of surface modification 02 = where 2flm,2 is the hydrophobic surface area and a is the total... 

The feldspar minerals have similar physical properties and often occur as prismatic or tabular crystals in igneous rocks, or as more anhedral grains in metamorphic and sedimentary rocks. They are colourless when fresh but are more commonly white due to incipient alteration impurities or inclusions result in coloured varieties, with green-brown alkali feldspars found in some metamorphic rocks, and orthoclase commonly found as pink. The surfaces of feldspar crystals are often iridescent due to twinning on a microscopic scale, with labradorite characterised by blue surface iridescence. Feldspars readily alter under hydrothermal action or chemical weathering to form members of the clay minerals group (. v.). Sodium-rich feldspars commonly decompose to form montmorillonite, in the presence of limited water, or to kaolinite with excess water alkali feldspars typically form illite or kaolinite sub-group (qq.v.) clay minerals (Deer et al, 1992 Rutley, 1988). 

Specific surface measurements suggest the presence of both vermiculitic and mont-morillonitic components. Illite also is present in large quantity, so the likelihood is that this is a complex interstratification of at least three components. Some diffraction peaks at lower angles coincide with higher-order peaks of illite or kaolinite, but there are also nonintegral peaks. 

The major minerals in coal are clays. Kaolinite is usually present in coal, but its identification by Moessbauer spectroscopy is very difficult due to the small amount of iron present and to surface contamination of the clay grains with iron oxides, mainly goethite. The other clay minerals present in coal are il-lite, chlorite and mixed clays. Their identification is not always easy. We have used a simple method, carrying out Moessbauer measurements at low temperatures and applying an external magnetic field to resolve the spectra and distinguish, for example, between illite and chlorite (11). 

In their study of the Canadian uranium deposit at Cigar Lake, Cramer and Smellie (1994) have plotted data for K, Na+, Ca +, and Mg +, in site waters on log([M"]/[H+]") versus log[H4Si04] diagrams. In Fig. 9.15, the illite phase field is contoured to show the stabilities of different illite fractions in I/S. The plot describes the evolution of water chemistry from atmospheric precipitation and surface-waters (lakes and streams) to infiltrating soil water and groundwater above, and then in contact with, the orebody. In the soil, kaolinite and illite (the dominant clay), quartz, and feldspars are... 

The cation exchange capacity of clays results from lattice imperfections or defects, isomorphous substitutions, and/or broken bonds on clay particle surfaces. Explain how the CEC s of kaolinite, the smectites, and illite, and their variation with pH, reflect these sources of their surface charge. 

Therefore, distribution functions indicate that the surfaces of the illites, as indicated by more intensive peaks at high energy, are more heterogeneous than those of kaolinites. This difference will perhaps explain the highest hydrophilicity of illites, evidenced by the determination of water adsorption isotherms, comparing with that of kaxrlinites. 

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