Lattice kaolinite

Clay Minerals. The clay minerals in coal all contain water bound within their lattices. Kaolinite contains 13.96%, illite 4.5%, and mont-morillonite 5% bound water. In addition, the montmorillonite in the mixed-layer clays also contains interlayer or adsorbed water. All of the water is lost during the high-temperature ashing. 

Of special interest to intercalation studies are complex non-stoichiometric systems, such as the so-called misfit layer chalcogenides that were first synthesized in the 1960s [45]. Typically, the misfit compounds present an asymmetry along the c-axis, evidencing an inclination of the unit cell in this direction, due to lattice mismatch in, say, the -axis therefore these solids prefer to fold and/or adopt a hollow-fiber structure, crystallizing in either platelet form or as hollow whiskers. One of the first studied examples of such a misfit compound has been the kaolinite mineral. 

Smectite is the first secondary mineral to form upon rock weathering in the semi-arid to sub-humid tropics. Smectite clay retains most of the ions, notably Ca2+ and Mg2+, released from weathering primary silicates. Iron, present as Fe2+ in primary minerals, is preserved in the smectite crystal lattice as Fe3+. The smectites become unstable as weathering proceeds and basic cations and silica are removed by leaching. Fe3+-compounds however remain in the soil, lending it a reddish color aluminum is retained in kaolinite and A1-oxides. Leached soil components accumulate at poorly drained, lower terrain positions where they precipitate and form new smectitic clays that remain stable as long as the pH is above neutral. Additional circumstances for the dominance of clays are ... 

In the structures cited in Table 12.3, except for pure silicon dioxide, metal ions are required for overall electrical neutrality. These metal ions are positioned in tetrahedral, octahedral, etc. positions in the silicate-like lattice. Sometimes they replace the silicon atom. Kaolinite asbestos has aluminum substituted for silicon in the Gibbosite sheet. Further, sites for additional anions, such as the hydroxyl anion, are available. In ring, chain, and sheet structures neighboring rings. 

Zeolite Type Zeolite Lattice Zeolite Content % Int./Na Y Internal Std. Nitrogen Method Kaolinite... 

Fig. 16.8 Electron micrographs of soil hema- fringes of ca. 1.4 nm, corresponding to thee tites. a) Irregular crystals from a laterite, Nigeria, edge length on the lower left side (courtesy J. after NaOH treatment to remove kaolinite (see Torrent) c) Grainy crystal from an Ultisol, South Torrent et at, 1994 with permission), b) same Brazil (KampfS. Schwertmann, 1983 with per-as a) crystals on a silicate flake. See lattice mission).

Fig. 16.9 Electron micrographs of soil lepidocro-cite. a) Large multidomainic lath-like crystal viewed perpendicularto [001] with laminar pores from a re-doximorphic soil, Natal, South Africa, b) Poorly crystalline grassy lepidocrocite crystals mixed with tiny ferrihydrite particles and pseudo-hexagonal kaolinite platelets. Origin as before (a. b courtesy P. Self), c) Small lepidocrocite crystal from a hydromorphic soil (with ferrihydrite) viewed perpendicularto [001] and showing (020) lattice fringes (see also Schwert-mann. Taylor, 1989,with permission).

Experimental lattice parameters for bulk kaolinite, together with those calculated in the static limit, are listed in Table 1. A difference in the length of parameter b of 2.9% is the largest discrepancy, which is reasonable since our calculation relates to an idealised clay structure. 

Table 1 Calculated and experimental lattice parameters for kaolinite...

Gibbsite and the "neutral lattice" minerals, 1 1 or 2 1 represent the extremes of chemical variat.on in the clay minerals. Gibbsite is a hydrated form of alumina. Kaolinite and pyrophyllite can be considered to be strictly aluminum-silicates, i.e., no ions other than Al, Si, 0, H are present in appreciable quantities in these minerals. This is not as... 

For various reasons, gibbsite and kaolinite are really the only minerals of the "neutral lattice" type which occur with any frequency in non-metamorphic rocks. These minerals are formed in soils, most noticeably from granitic rocks but are also commonly found forming from basic rocks during the weathering process (Millot, 1964 Tardy, 1969). The... 

Fig. I. Diagrammatic representation of the succession of layers in some layer lattice silicutes (12) where O is oxygen a. hydroxyl . silicon Si-AI 0. aluminum t>, Al—Mg. O. potassium 0, Na—Ca Sample layers are designated as 0. octahedral T. tetrahedral and B/G, brucite- or gihbsitelike. The distance depicted hy arrows between repealing layers in nut are 0 72. kaolinite 1.01. halloysite (10 A) 1,00. mica ca 1.5. montmorillonite and 1.41. chlorite...

In conclusion thermal degradation studies on Nautilus pompilius indicate that mineralizing matrix and aragonite shell represent a true structural entity. By the sharing of oxygens in protein and mineral lattices we will generate phase boundaries of the type that are present, for instance, in the common clay mineral kaolinite. Here, aluminum octahedra and silica tetrahedra incorporate the same oxygens and hydroxyls, and layers composed of octahedra and tetrahedra arise (Fig. 13). 

Raman spectra of hydrazine (a) and of the kaolinite-hydrazine (KH) intercalate (b) suspended in liquid hydrazine are shown in Fig. 1. In contrast to the strong IR-active absorption bands characteristic of clay minerals below 1200 cm-1, the corresponding Raman bands of kaolinite are relatively weak. Nonetheless, both the kaolinite and the hydrazine bands can clearly be resolved (Fig. lb). Hydrazine bands occur at 903,1111,1680, 3200,3280, and 3340 cm-1, whereas the kaolinite bands are found at 140 (not shown), 336, 400, 436, 467, 514, 636, 739, 794, and 3620 cm-1. Observation of lower-frequency adsorbate modes below 1200 cm-1 are often obfuscated in IR absorption spectra because of the strong lattice- framework vibrational modes. As the Raman spectrum of the KH complex shown in Fig. la indicate, the lower-frequency modes of hydrazine below 1200 cm-1 can readily be resolved. The positions of die hydrazine bands in the KH spectrum (Fig. lb) are similar to those of liquid hydrazine (Fig. la) and agree well with published vibrational data for hydrazine (22.23.29-31). The observed band positions for the KH complex, for hydrazine, and for kaolinite are listed in Table 1. 

Obviously, the dissolution of the elements leads to change in the crystal lattice and the mineral composition. This can well be seen during the acidic treatment of montmorillonite or bentonite for catalytic purposes (Section 2.1). The treatment is done using concentrated hydrochloric, sulfuric, or phosphoric acid. X-ray diffraction studies show that a commercially available montmorillonite has low montmorillonite content (53%). The other constituents are illite 10%, kaolinite 6%, quartz 10%, plagioclase 5%, gypsum 1%, anhydrite 4%, and amorphous 7%. 

Clay Colloids. Three clay minerals are important components of the clay colloid fraction of soils, namely, montmorillonite, illite, and kaolinite (Adams, 1973). Mont-morillonite consists of one layer of aluminum oxide between two layers of silicon oxide (Figure 11.2). An important feature of this mineral is its multilayer arrangement, which permits smaller molecules such as pesticides to penetrate between them. This is referred to as an "expanding lattice" clay. Illite is also a three-layer clay but it does not form multilayers. Kaolinite is a two-layer mineral of aluminum oxide and silicon oxide. 

Because several spatial stacking arrangements are possible there are several kaolin minerals, each with the same chemical composition, namely Al2Si205(0H)4, but with different properties. Nacrite, dickite, kaolinite, halloysite, and livesite are well recognized species. No positive evidence has so far been published linking other trivalent cations with a single layer lattice structure, but it has been suggested that iron(iii) can replace aluminium in part in the kaolin lattice. 

The ideal constitution of the kaolin layer represents an electrically neutral unit, with rarely any isomorphous substitution of cations of different charges within the lattice. Consequently, kaolinite and related minerals would not be expected to show a large cation exchange capacity, and indeed this is usually the case. That a small but varying exchange capacity does occur may be attributed to two principal causes. 

The product from the Duolite columns will be evaporated to form 2M Na2C03-0.002M CS2CO3. Barrer (2) has found that alkaline solutions of sodium carbonate react with kaolinite to form sodalite containing tightly bound sodium carbonate. We have experiments in progress to determine whether cesium is also bound in the sodalite lattice. 

Mineral composition, as determined by X-ray diffraction, shows a dominance of clay minerals, although quartz and opaline silica are persistent as sub-dominant and locally dominant or co-dominant (Table II). Of the clays, expandable lattice clay minerals, predominantly montmorillonite, occur in all the deposits with kaolinite or illite appearing as accessory or subdominant components. A marked contrast in the dominant clay species occurs between the brown oil shale unit and the two units below it at Condor. In these lower units, kaolinite is in greater abundance than other clays as well as quartz, an aspect already alluded to in the variations in Table I. (Loughnan (8) also noted that the structure of the kaolinite changes from ordered in the lower units to disordered in the brown oil shale unit). 

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