Kaolinites of all kinds (fine, ‘fireclay,’ ‘type IV,’ etc.), some of which do not expand or expand incompletely with the usual intercalation methods used for comparison, are expanded completely by treatment of dry (110°C) clay with dry CsCl salt, followed by contact with hydrazine for 1 day at 65°C and then with DMSO overnight at 90°C. Comparison treatments were grinding in KOAc, soaking in hydrazine, and Li-DMSO, as well as combination of these. Following the Cs-hydrazine-DMSO treatment, the 7.2 Å spacing of 1:1 dioctahedral layer silicates shifts to 11.2 Å and the 11.2 Å/(7.2 + 11.2 Å) ratio ≃1.0. The trioctahedral 1:1 layer silicates and chlorite are not expanded by the Cs-hydrazine-DMSO procedure.

Structural Fe2+ in montmorillonite is readily oxidized by contact with water, salt solutions or on mild heating. This is shown clearly by the Mössbauer spectra and is associated with a sharpening of the infrared absorption near 880 cm−1. It was inferred that this band comprises the Fe2+—OH—Al and Fe3+—OH—Al deformations. The rate at which oxidation occurs depends on the exchangeable cations. High acidity of the interlayers is conducive to oxidation, as is contact with Cu2+-containing solutions or concentrated H2O2 solutions.

The results show clearly that any chemical treatment of montmorillonite causes changes in the oxidation state of structural iron.

A unique vanadium-titanium-bearing mixed-layered clay is currently being mined as an ore of vanadium at Potash Sulphur Springs, AR. The clay contains 80% expandable portion and has both a 14.22 and 18.24 Å hydration state in addition to the 9.49 Å dehydrated state; ethylene glycol expands this material to 16.69 Å. The 060 reflection for all hydration states is between 1.50 and 1.51 Å indicating the material is dioctahedral. The “mean chemical formula” calculates as(Ca0.08 K0.02 Na0.03)0.13 (Al0.11 V0.90 Ti0.19 Fe0.64 Mg0.14)1.98 (Si3.79 Al0.21)4 O10 (OH)2·nH2O.

The adsorption of Cu2+ on kaolinite was studied at different ionic strengths following various treatments of the mineral surface in order to evaluate the conditions influencing adsorption. The data indicate a strong preference of the Na+ exchange form of kaolinite for Cu2+ but a weak affinity of the natural kaolinite for Cu2+. Protons are generated by Cu2+ adsorption, a result of the exchange of surface protons, and possibly the enhancement of Cu2+ hydrolysis at the kaolinite surfaces. The exchange of Na+ by Cu2+ on the kaolinite is not described by the mass-action equation, but can be interpreted in terms of permanent charge sites on the surfaces when the additional factors of Na+-H3O+ exchange and blockage of sites by Al ions are considered.

A stable porous system consisting of montmorillonite cross-linked by Al-hydroxide oligomers was synthesized by reacting at room temperature an aqueous solution of such oligomers with a unit-layer dispersion of montmorillonite. The resulting cross-linked montmorillonite (Al-CLM) is a nonswelling material, showing basal spacings of 14.4 to 18.8 Å after air drying and between 14.2 to 18.0 Å after treatment at 110°C. The basal spacing is found to depend on the age and OH/Al ratio of the Al-hydroxide solution, as well as on the relative amounts of the two reactants. A specific surface area of 160 m2/g and a diffraction pattern with a dominant basal spacing of 17.5 Å is obtained by using Al-hydroxide with OH/Al = 1.85, aged for at least 5 days, and by applying an Al/montmorillonite ratio greater than 1.5 in the cross-linking process. The basal spacing of Al-CLM remains essentially unchanged after heating at 220°C, while the specific surface area is not affected by heat treatment up to 480°C.

Two possible configurations of Al-hydroxide oligomers, homogeneously distributed between parallel montmorillonite unit-layers, were considered in order to account for the basal spacing of 17.5–18.8 Å, viz. (a) stacking of two oligomeric ring units in parallel orientation relative to the clay lamellae and (b) perpendicular orientation of individual oligomeric units.

Cross-linking of Li-montmorillonite by hydroxy-aluminum oligomers was performed in a specially constructed mixing apparatus. Observations on flocculation and solution composition were carried out during and after the cross-linking reaction; the dry product was studied by scanning electron microscopy.

Flocculation was most pronounced at Al/montmorillonite ratios between 0.98 and 2.45 mM/g; below and above this range, flocculation was much less intensive. These observations can be explained by heterocoagulation and protecting colloid action. A complete neutralization of the montmorillonite charge was estimated at 1.9 mM adsorbed Al per g clay, and in order to account for the electrical charge of the hydroxy-Al, polymers with an average charge of 0.5 per Al atom must be assumed on the montmorillonite surface. Assuming that the hydroxy-aluminum form in the unreacted solution is Al6(OH)3+12, the adsorbed polymer will be Al24(OH)12+60. Alternatively, assuming Al6(OH)3+15 in the unreacted solution, this form will remain unchanged upon adsorption onto the montmorillonite surface.

Differences in the microfabric of dry Al-CLM as a function of Al/montmorillonite ratio can be explained along the lines of the interpretation of the flocculation studies.

X-ray superlattice reflections, infrared spectroscopy, and chemical analyses have established that cetylpyridinium bromide (CPB) is highly ordered when adsorbed on vermiculite. The molecules, which stand at about 57° to the silicate surface, form close-packed arrays. Full surface coverage is achieved only for the most highly charged vermiculites. The packing within the arrays accounted for the superlattice observed and each adsorbed molecule had an area of 18.4 Å2 at the surface. The implications of these findings for the CPB method used in soil surface area studies are discussed.

The dispersion of clays is of great importance in determining various soil properties such as hydraulic conductivity. A procedure which involves fixing followed by embedding of clay particles in an epoxy resin is described. This procedure enables the observation of cross sections of clay tactoids under a transmittance electron microscope, and the determination of the number of plates per tactoid. The use of the procedure for the determination of the relation between the exchangeable sodium percentage (ESP) and tactoid size in suspensions of a Na/Ca bentonite system is presented. It was demonstrated that even at ESP 5 significant dispersion already occurs, the average number of plates per tactoid being 6.6 as compared to 16.1 at ESP 0.

Infrared spectra of two minerals; Urkut quartz (Hungary) and a Swedish feldspar, of different origin with different physical characteristics and crystallinity were studied. Samples were taken after appropriate grinding, and infrared spectra, X-ray powder diffraction and water vapor absorption measurements were made along with electronmicrographs. Quantitative conclusions were drawn from changes of particle size and the ratio of bands of the Si—O groups and also the degree of crystallinity and changes of the particle size, respectively.

Several new salt intercalation complexes of halloysite have been prepared and characterized using X-ray powder diffraction techniques taking into account both the position and the shape of the d001 peaks. The amount of intercalated ion in some fully complexed halloysites has been directly determined using conventional analytical techniques. The results show that less than half of the theoretical amount of salt is intercalated into the clay; the amount of salt depending on its nature and, where hydrolyzable ions are present, on the pH. Infrared spectra taken of some complexes give an indication of the nature of the interaction within interlayer space and elsewhere. The interactions are weak and are either dipolar attractions or hydrogen bonds. The ions which show the greatest tendency to intercalate with halloysite are water structure-breaking cations or hydrogen-bonding anions.

The influence of the activity of water on the phase composition of aluminum hydroxides obtained by reaction of amalgamated aluminum with water has been studied. The reaction was carried out in solutions of water and dioxane, and in sodium chloride solutions of different concentrations; amorphous aluminum hydroxide was precipitated initially. The aging of this primary product to bayerite, pseudoboehmite, or an amorphous gel was controlled by the water content of the system. The pseudoboehmite has shown a significant reactivity when used as a source of alumina in the hydrothermal syntheses of kaolinite at relatively low temperature and pressure.

Scanning electron microscopic (SEM) examination of the quartz isolated from chert of Transvaal and Swaziland, of 2000 and 3400 million year (MY) ages, respectively, in southern Africa revealed marked differences in quartz morphology. Well-defined individual euhedral quartz crystals, with polyhedral triple-point faces, were clearly evident on freshly fractured Transvaal chert surfaces as well as with the quartz isolates from the chert. The morphology and coarseness suggest crystal growth with little, if any, metamorphism; however, the δ18O values of 23.8–24.1‰ suggest crystallization temperatures of perhaps 40–45°C. In contrast, fracture surfaces of the older, strongly metamorphosed Swaziland cherts revealed a high degree of grain intergrowth which inhibited fracture between quartz grains. Quartz isolates from these showed strongly interlocked quartz crystal clusters and elongated chips of quartz with poorly defined irregular faces. Intercalation of mineral veins in the cherts on a mm scale and the intergrown character of the quartz grain boundaries provide evidence that the latter cherts have been strongly metamorphosed and recrystallized, in keeping with 14.6–15.1‰ δ18O values, corresponding to 80°C fractionation with water. The SEM micrographs of the fine quartz (1–10 µm) isolated from the Otavi dolomite formation of the 700-MY Damara System and from the 2000-MY Transvaal Dolomite Series revealed well-defined subhedral and euhedral quartz crystals of small size which, together with the 26.9–27.8‰ and 23.8‰ δ18O values, respectively, indicate that these dolomites have been affected little, if any, by post-depositional metamorphism; their crystallization temperatures fall in the range of 25–30 and 40–45°C, respectively.

The thermal decomposition of the kaolinite: N-methylformamide intercalate [Al2Si2O5(OH)4·HCONHCH3] has been studied by differential scanning calorimetry (DSC). The decomposition starts at 355 K, finishes at 450 K and follows Avrami-Erofeev kinetics for α = 0.04–0.96. ΔH for the loss of organic is 19 ± 2 kJ mol−1; the activation energy for the reaction is 30 ± 3 kJ mol−1.