The technique of scanning force microscopy (SFM) was used to study the nanometer-scale structure of Cu(II)-exchanged hectorite thin films. Supporting data were also obtained from Electron Spin Resonance (ESR) and X-ray diffraction (XRD) techniques. The surfaces studied included pure Cu(II)-exchanged hectorite, Cu(II)-exchanged hectorite exposed to benzene and Cu(II)-exchanged hectorite exposed to aniline. SFM images of the unexposed Cu(II)-exchanged hectorite surface revealed a smooth surface composed of interlocking platelets. The lateral dimension of these platelets ranged from a few nm to about 1 μm. After exposure to refluxing benzene, the SFM showed that the platelets underwent vertical shifts in position. This is believed to have occurred from intercalated benzene that polymerized in the interlayer region. No SFM evidence was obtained for benzene polymerization on the surface of the hectorite. Hectorite films exposed to aniline at room temperature revealed a post-polymerization structure on the hectorite surface consisting of small polymer bundles. The diameter of these bundles was measured to be 300–3000 Å, similar to the structure seen on electropolymerized polyaniline films. Aniline polymerized on the surface of hectorite films at 180 °C revealed a structure similar to undoped n-methyl-pyrrolidinone (NMP) cast polyaniline films. In this case, the polymer bundles are only 300 Å in dimension on average. XRD and ESR data also indicated interlayer aniline polymerization in Cu(II) exchanged hectorite. Mechanistic considerations affecting these polymerization reactions are presented.

Three different models have been reported previously to describe the kinetics of the transformation of smectite to illite (Pytte 1982; Velde and Vasseur 1992; Huang et al. 1993). In order to evaluate the general utility of these models to calculate the timing and extent of this transformation, each model was applied to four different geologic settings (Denver Basin, Gulf Coast, the Salton Sea Geothermal System, and Paris Basin) in which the ages, geothermal gradients and potassium ion activities vary markedly. The model results are compared to the measured percentages of illite in illite/smectite (I/S) and the K/Ar ages of I/S (if available) to test the utility of a given model to a particular basin.

Although individual models can be applied to study this transformation within a specific setting, none of these models was successful in simulating the transformation for all four basins. The Salton Sea was simulated best using the model by Huang et al. (1993), which incorporated an increased geothermal gradient during the last 20,000 years. These results indicate that a large fraction of illite formed due to this increased geothermal gradient, and underscores that temperature is a dominant kinetic factor in forming illite. The Denver Basin was simulated well by the models of Velde and Vasseur (1992) and Pytte (1982). The Gulf Coast was simulated very well by the model of Huang et al. (1993) using a term that terminates the transformation at 75% illite. For the Paris Basin, the results are mixed. The models can be refined by comparing the calculated and measured ages of illite such as the K/Ar ages of I/S to understand the thermal history of a particular basin. The calculated ages of illitization derived from these refined models can be used to indicate the time at which source rocks became thermally mature to form oil and gas.

Ce/Al- and La/Al-pillared smectites were prepared by cation exchange of bentonite, saponite and laponite with hydrothermally treated (130–160 °C for 16–136 h) solutions containing mixtures of aluminumchlorohydrate (ACH) and Ce3+-/and La3+-salts. After calcination at 500 °C, the pillared products are characterized by basal spacings between 24.8 and 25.7 Å and surface areas of approximately 430 m2 g−1. The products are hydrothermally stable at 500 °C after 2 h in steam. The large basal spacings are due to the formation of a large Ce/La-bearing Al-polyoxocation, whose formation is favored by initially high Al concentrations ≥3.7 M and an OH/Al molar ratio of approximately 2.5. The Ce/Al or La/Al molar ratios can be as low as 1/30. 27Al nuclear magnetic resonance (NMR) spectroscopy has shown that the polyoxocation has a higher Altetrahedral/Aloctahedral ratio than the Keggin structure Al13, which may partly explain the higher stability compared to normal Al-pillared clays. Hydroconversion of n-heptane indicated that the activity of the Pt-loaded pillared products is higher than that of a conventional Pt-loaded amorphous silica-alumina catalyst. Selectivity is strongly dependent on the type of starting clay and its acidity. In industrial hydrocracking of normal feedstock, a Ni/W-loaded Ce/Al-pillared bentonite catalyst showed rapid deactivation due to coke-formation reducing the surface area and the pore volume. Additionally, coke-formation is facilitated by the relatively high iron content of the pillared bentonite (3.43 wt% Fe2O3).

Approximately 20 wt.% of the bauxite from Andoom in northern Queensland, Australia is composed of material that cannot be accounted for by identifiable well-crystallized phases. This poorly-diffracting material (PDM), found within the core of bauxitic pisoliths, has similar characteristics to that of eta-alumina (η-Al2O3); a cubic form of alumina. A differential XRD pattern of the PDM displayed a series of broad diffraction maxima attributed to eta-alumina with a mean crystal size of 9 nm. Unit cell refinement, on the basis of a cubic cell, gave a lattice parameter of a = 7.98 Å for Andoom eta-alumina. TEM and selected-area electron diffraction revealed the PDM to be composed of minute (10 nm wide), randomly oriented crystals of eta-alumina in close association with Al-hematite. Chemical analysis using a nanoprobe showed Andoom eta-alumina to be almost pure alumina with <2 M% Fe, <1 M% Si and <1 M% Ti. The closely associated Al-hematite may contain as much as 22 M% Al, however a value closer to the theoretical limit of 17 M% is more likely. A broad absorption band at 3450 cm−1 and 1630 cm−1 in the infra-red spectrum of the PDM indicates the presence of a substantial quantity of H2O, strongly adsorbed onto the surface of the crystals. This is presumably due to η-Al2O3's large surface area of approximately 2200 m2/g. The natural occurrence of η-Al2O3 in bauxite may be the result of low H2O activities within the micro-environment of pores at the time of crystallization. The epigenetic replacement of kaolinite with η-Al2O3 and Al-hematite is put forward as an explanation for the formation of bauxitic pisoliths at Andoom.

The effect of acid type and concentration on the reaction rate and products of dissolution of hectorite in inorganic acids was investigated. The dissolution of hectorite in hydrochloric (HCl), nitric (HNO3) and sulphuric (H2SO4) acids was characterized using quantitative chemical analysis, infrared (IR) and multinuclear MAS NMR spectroscopies. The rate of dissolution increased with acid concentration and decreased in the order HCl ≥ HNO3 = H2SO4 at the same molar concentration. No differences were found in the reaction products of hectorite treated with the three acids. The rate of Li dissolution was slightly greater than that of Mg at lesser acid concentrations (0.25 M), indicating that protons preferentially attack Li octahedra. The gradual changes in the Si-O IR bands reflects the extent of hectorite dissolution. The analysis of 29Si MAS NMR spectra relative peak intensities with dissolution time and acid concentration provided direct dissolution rates for tetrahedral (Q3) Si. After acid dissolution, most Si was bound in a three dimensional framework site (Q4), but a substantial part also occurred in the Si(OSi)3OH (Q31OH) and Si(OSi)2(OH)2 (Q220H) environments. These three sites probably occur in a hydrous amorphous silica phase. Both AlJV and AlVt rapidly disappeared from 27Al MAS NMR spectra of the dissolution products with acid treatment. The changes in IR and MAS NMR spectra of hectorite due to acid dissolution are similar to those of montmorillonite.

Trimethylammonium ions (TMA+) with formula CH3(CH2)n-1N+(CH3)3, with n = 4, 8, 12, 16, 18 and 22 were intercalated into synthetic Li-fluorotaeniolite (Li-FTN) and Li-fluorohectorite (Li-FHT) by cation exchange. The products were analyzed by thermogravimetric (TGA) and X-ray powder diffraction (XRD). XRD patterns exhibited variable (001) spacings of the TMA+/mica complexes depending upon the exchange ratio of TMA+/Li+ and the carbon number of TMA+. Detailed inspection of these XRD patterns clarified the structures of the complexes and also the intercalation mechanism, as follows: The fundamental structure of the complexes is the commonly known intercalation structure where the “paraffin-type bilayers” of TMA+ are in the mica interlayer and their long chains incline at approximately 30° to the silicate sheet. This structure appeared at the final stage of the intercalation reaction. During the intermediate stage of the reaction, units of this structure and those of hydrated mica formed randomly and regularly interstratified structures. Variable (001) spacings in XRD patterns showed the structural change of the complex with an increasing number of TMA+-intercalated units.

Conversion of tertiary butylacetate to isobutylene and acetic acid and cracking of n-octane were used as model reactions to monitor the catalytic activity of a condensate and aqueous extract derived from a sample of montmorillonite. The condensate was obtained by condensing the vapor phase evolved on heating the clay and the extract was derived from the clay by prolonged water extraction. Both condensate and extract were colloidal systems, which were separated into solid and liquid fractions by distillation. Reactions carried out in a dynamic system established that the solid components acted as true acid catalysts, whereas the liquid fractions were inactive under the experimental conditions adopted. The catalytic activity per weight of the condensate exceeded that of either the parent clay or the extract.

The present results confirm that colloidal size catalysts of high activity can be generated from clays. Such materials, mobilized and transported alone or with formation fluids, may act as catalysts in places removed in space and time from their source. This finding refutes objections previously raised to the operation of bulk clays as catalysts for reactions with particulate organics and supports the concept that acid catalysts derived from clays may participate in organic geochemical reactions in an aqueous medium.

Montmorillonites saturated with small quaternary alkylammonium ions such as tetramethyl-ammonium (TMA) or trimethylphenylammonium (TMPA) are excellent sorbents for aromatic pollutants. In some cases, water inhibits arene sorption, but the inhibition mechanism is not understood completely. The objectives of this study were to determine whether arenes interact with adsorbed TMA and TMPA ions and/or with siloxane surfaces, and how water affects these interactions. We reacted benzene and ethylbenzene vapors with normal- and reduced-charge TMA- and TMPA-montmorillonite films at several relative humidities, and obtained infrared spectra of the resulting sorbate-clay complexes. Arene sorption caused the methyl asymmetric deformation vibrations adsorbed TMA and TMPA to shift to lower wave-number, whereas water sorption caused shifts to higher wavenumber. In the absence of water, benzene and ethylbenzene adsorbed on the siloxane surface as well as interacted directly with TMA and TMPA ions. The proportion of TMA and TMPA ions that interacted with benzene and ethylbenzene was greater for reduced-charge than normal-charge montmorillonite. Comparison of the HOH deformation and cation methyl asymmetric deformation vibrations indicated that both benzene and ethylbenzene inhibited water sorption substantially, and that water more readily displaced benzene and ethylbenzene from TMA and TMPA ions than from siloxane surfaces. Water inhibited arene sorption mainly by hydrating exchangeable cations, thereby obscuring siloxane surfaces adjacent to adsorbed TMA and TMPA ions and decreasing the average pore dimensions. These results indicate that in the presence of bulk water, arene adsorption likely occurs primarily on the siloxane surface.

Synthetic hectorite clay minerals were hydrothermally crystallized with direct incorporation of a series of five water-soluble polyvinyl alcohols (PVA) of molecular weights from 9000-146,000. The molecular weight of PVA had little effect on the success of hydrothermal hectorite synthesis, d-spacing or the amount of polymer incorporated. The basal spacings range from 19.5 Å to 20.8 Å and the amount of polymer incorporated ranges from 20 wt.% to 23 wt.%. Incorporation of PVA within the clay inter-layers, along with Li(I) ions to compensate the lattice charge, is indicated. Thermal gravimetric analysis and small angle neutron scattering were used to further examine the polymer-clay systems. Small PVA-clay crystallites that are coated with excess PVA are indicated. Removal of the polymer does not alter the extended synthetic clay network, and the nitrogen BET surface area increases from <5 m2/g to >200 m2/g.

The effect of heat treatments on the swelling, dispersion, particle charge and particle aggregation of Li-, Na-, K-, Mg-, Ca- and Al-Wyoming bentonite was investigated. Before thermal treatment, unheated (25 °C) Li-, Na- and K-clays showed increased d001 spacing on glycerol solvation and dispersed spontaneously in water. Mg-, Ca- and Al-clays did not disperse spontaneously in water, but the d001 spacing increased upon glycerol solvation. After heating at 300 °C or above, none of these clays dispersed spontaneously. However, swelling varied with the type of cation and the temperature of heating.

The results generally suggested that swelling and dispersion of homoionic Wyoming bentonite after heating at various temperatures depended upon the nature of bonding between clay particles and the cations. Enhanced swelling and dispersion of clays indicated the more ionic character of the cationic bonding than cases where heating resulted only in swelling, with polar covalent bonding of cations to clay surfaces allowing limited hydration. It is also suggested that, when both swelling and dispersion as a result of thermal treatment are absent, a covalent bond is formed between cation and clay surface.

Thermal treatment apparently affects the bonding in different ways. It appears that the smaller cations (ionic radius <0.7 Å) Li, Mg and Al migrate to octahedral vacant sites and form covalent bonds after heating at 400 °C; this drastically reduces the negative charge. This process for Li-clays occurred even at 200 °C. The larger cations (ionic radius > 0.9 Å) Na, K and Ca apparently did not migrate into the lattice sites after heating to 400 °C; a high proportion of them were exchangeable. The data for exchangeable cation, particle charge and clay particle size were consistent with the postulated effect of the nature of cationic bonding upon swelling and dispersion properties.

Fundamental particle thickness measurements of Dolná Ves hydrothermal illite/smectite (I/S) samples confirmed earlier findings regarding the content of fixed cations in illite interlayers (ca. 0.9/O10(OH)2). The distributions of fundamental particles and mixed-layer crystals of a given sample are internally consistent. In samples dominated by bilayer fundamental particles, mixed-layer crystals most often contain even numbers of layers. The expandabilities measured by XRD are much higher than so-called minimum expandabilities obtained from HRTEM measurements. This discrepancy is explained by assuming that the coherent scattering domains of Dolná Ves clays do not correspond to natural mixedlayer crystals but are thicker, probably due to parallel association of crystals on the oriented XRD slide. This tendency to produce intercrystal contacts is probably related to the unusually large ab dimensions of crystals of Dolná Ves clays.

Helvetic sediments from the northern margin of the Alps in eastern Switzerland were studied by clay mineralogical methods. Based on illite “crystallinity” (Kübier index), the study area is divided into diagenetic zone, anchizone and epizone. Data on the regional distribution of the following index minerals are presented: smectite, kaolinite/smectite mixed-layer phase, kaolinite, pyrophyllite, paragonite, chloritoid, glauconite and stilpnomelane. Isograds for kaolinite/pyrophyllite and glauconite/stilpnomelane are consistent with illite “crystallinity” zones. Using the ordering of mixed-layer illite/smectite, the diagenetic zone is subdivided into three zones. The illite domain size distribution was analyzed using the Warren-Averbach technique. The average illite domain size does not change much within the diagenetic zone, but shows a large increase within the anchizone and epizone. The average illite b0 value indicates conditions of an intermediate-pressure facies series.

The Helvetic nappes show a general increase in diagenetic/metamorphic grade from north to south, and within the Helvetic nappe pile, grade increases from tectonically higher to lower units. However, a discontinuous inverse diagenetic/metamorphic zonation was observed along the Glarus thrust, indicating 5–10 km of offset after metamorphism. In the study area, incipient metamorphism was a late syn- to post-nappe-forming event.

The lithium form of taeniolite served as the molecular template for carbon nanocomposites. It was intercalated with hydroxy aluminum and hydroxy aluminum-zirconium cations. Aliquots of the inorganic matrices were saturated by furfuryl alcohol followed by its interlayer polymerization. The structures were heated at 973 K in nitrogen to carbonize the polymeric precursor. Additional materials were mixed with polypropylene glycol which was then carbonized within the mineral layers. The surface properties of the nanocomposites were studied by X-ray diffraction (XRD), DTA, SEM and sorption experiments (sorption of nitrogen). The results showed that structural properties of the derived materials depend on the inorganic matrix and organic precursor. The carbon-taeniolite nanocomposites derived from polyfurfuryl alcohol as a precursor were characterized by high carbon content and a high percentage of its surface area in micropores. A broad spectrum of surface characteristics of the final products were found, depending on the history of the sample.

The cleavage of two single-crystal chlorites (a clinochlore and a penninite) has been studied using angle-resolved X-ray photoelectron spectroscopy (XPS). Both minerals cleaved in regions not typical of the bulk; the composition of the clinochlore was found to be especially non-uniform. The brucitic interlayer divided evenly between the pair of new surfaces exposed for two cleaves in the clinochlore, but was partitioned unequally in two cleaves in the penninite. The differences in apparent composition between the complementary pairs of surfaces are interpreted to show a marked preference of octahedral Al for the brucitic layer, in agreement with X-ray bulk structure refinements. For both chlorites, the layer charge was reduced in regions of easy cleavage, which also had a higher proportion of Si and less tetrahedral Al than the bulk chlorite. The percentages of tetrahedral aluminium deduced from the XPS surface analyses agreed satisfactorily with the percentages independently determined by consideration of the magnitude of anisotropy in the X-ray photoelectron diffraction (XPD) patterns. The XPD patterns from the clinochlore for rotation about axes parallel and antiparallel to the crystallographic a-axis were identical, showing that tetrahedral ordering was absent.

The weathering of chlorite, one of the major minerals of the host rock in the uranium ore deposit at Koongarra, Australia, was examined by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron microprobe analysis, and transmission electron microscopy (TEM). The conversion sequence of chlorite weathering is: (1) chlorite; (2) chlorite/vermiculite intergrade (showing XRD responses to various treatments intermediate between those of chlorite and vermiculite); (3) interstratified chlorite and vermiculite; (4) vermiculite; and (5) kaolinite. This sequence may be more simply expressed as chlorite ⤒ vermiculite ⤒ kaolinite. The weathering finally changed chlorite into sub-micrometer to micrometer sized Fe minerals and kaolinite. The transformation of chlorite to vermiculite is chemically characterized by an Fe and Mg loss with a slight decrease in the Al/Si ratio. Mg continues to be released throughout the weathering. Fe minerals formed through chlorite weathering are located between chlorite and vermiculite domains (a few μm in size) at first, and then accumulated between grain boundaries, occasionally forming veins. The distribution of Fe minerals is suggestive of preferential pathways of water movement. The time-dependent nature of mineral alteration demonstrated in the present study must be taken into account for the quantitative estimation of radionuclide migration.

Hydrothermal treatment of a mixture of silicic acid, cobalt chloride, sodium dithionite and sodium hydroxide at 250 °C under 500 psi of argon produced a pink solid. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction data showed the product to be a well-crystallized smectite. SEM/EDX analysis gave a unit cell formula of [(Si8.05)(Co5.58)O20(OH)4]Na066. Heating the same mixture at 150 °C without argon gave a less well ordered smectite of composition [(Si7.93)(CO5.92)O20(OH)4]Na0.42. Two peaks were observed in the cyclic voltammograms of electrodes modified with films of these two clays recorded for the blank electrolytes in the absence of any adsorbed electroactive species. The first peak was attributed to the oxidation of a small fraction of the Co2+ sites within the clay lattices to Co3+. The second peak was assigned to further oxidation of these Co3+ to Co4+.

Weathering products formed on the surface of K-feldspar in Yakushima Island, Japan were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). XRD confirmed that the weathering products were composed mainly of gibbsite and halloysite. SEM, TEM and EDX clearly showed formation of amorphous aluminum hydroxide exhibiting 2 distinct habits: 1) curled fibrous or circular forms less than 0.02 μm in diameter; and 2) a spherical habit less than 1.0 μm in diameter. The fibrous aluminum hydroxide exhibited curled fibrous forms or circular forms less than 0.02 μm in diameter and gave a diffuse electron diffraction halo. EDX indicated that the material consisted mainly of Al and very small amounts of Si and Fe. The spherical aluminum hydroxide also gave similar EDX and electron diffraction characteristics to the fibrous material. These fibrous and spherical aluminum hydroxides must be formed as a metastable phase in the earliest weathering stages, and transformed into a stable phase of gibbsite and halloysite as the reaction proceeded.

Hydrogen- (δD = −106 to −97‰) and oxygen-(δ18O = +14.0 to +16.6‰) isotope compositions of kaolinite from late Cretaceous and Oligocene deposits at Iwaizumi, northeastern Japan, indicate that these clays formed by weathering of volcanic parent rocks, rather than during hydrothermal (>100 °C) alteration. The Iwaizumi kaolinites also are depleted of D and 18O relative to kaolinite formed during modern, tropical weathering, suggesting that the kaolinite developed under cool or cool-temperate conditions. The oxygen-isotope compositions of the kaolinite increase slightly upward through the deposits, perhaps implying a modest increase in temperature from late Cretaceous to Oligocene time. The δD and δ18O results for kaolinite from the Oligocene deposits closely follow the kaolinite weathering line. However, a small but systematic deviation from this line for the Cretaceous kaolinites is most simply explained by post-formational, hydrogen-isotope exchange between these clays and downward percolating meteoric water.

We studied the influence of time ageing (up to 120 d at 50°C or 30d at 95°C) on the mineralogical and chemical composition of hydrolytic species of mixed aluminum and iron samples formed at pH 5.0 and initial Fe/Al molar ratio (Ri) ranging from 0.1 to 10. The partitioning distribution of Fe and Al in soluble or solid phases of different sizes (<0.01, 0.2–0.01, >0.2 μm) depended on Ri and time. The ratio of Fe to Al of the <0.2 μm Fe-Al species of the samples at Ri ≤ 4 slowly increased with time. Usually the higher Ri the higher the amount of Fe + Al present in soluble or very fine solids (<0.2 μm). With time, high percentages of Fe were found mainly in the <0.01 μm while the Al increase in the >0.2 μm sizes. Gibbsite, without the presence of well-crystallized Fe-oxides was formed in the samples at Ri ≤ 0.5 after 7–120 d at 50°C. In the samples at Ri ≥ 1 low-crystalline ferrihydrite was observed after ≥60 d. Only after 120 d did gibbsite or hematite start to form in the samples at Ri = 1–10. However, even after prolonged ageing at 95°C, low-crystalline ferrihydrite was still present at Ri ≤ 4.

The Fe-Al samples at Ri ≥ 1 aged 32 d at 50°C dissolved almost completely by acid ammonium-oxalate (82–93%), but the samples at Ri ≤ 0.5 were only partially solubilized (13–60%). After further 30 d at 95°C, the percentages of Fe + Al solubilized by oxalate from the samples at R ≥ 0.5 was still relatively high (22–39%).

Fine clays (<0.1 μm) extracted from an acid soil developed in a granite saprolite from the Massif Central, France, were characterized by X-ray diffraction (XRD) using a curve decomposition program, and high-resolution transmission electron microscopy (HRTEM) associated with a method of impregnation of moist samples. Direct measurement of d-spacings were performed on HRTEM photographs. Decomposition of XRD patterns indicated 5 to 6 different clay phases including chlorite (and/or hydroxy-interlayered vermiculite), vermiculite/smectite, illite/vermiculite and illite/smectite mixed layers. Expandable phases with decreasing layer charge (vermiculite, high- and low-charge smectite) were shown in the clay assemblage. When performed on K-saturated samples subjected to wetting and drying cycles, HRTEM observations were consistent with the XRD results. The major clay mineral phases identified by the decomposition of XRD patterns were also found by direct measurement of d-spacings on HRTEM images. Vermiculite and high-charge smectite appeared to be impregnated with preservation of their initial hydration state, whereas low-charge smectite interlayers were penetrated by the resin molecules during the impregnation procedure. It was concluded that the decomposition of XRD patterns gave a realistic analysis of the clay phases present in a complex soil clay sample, as well as the direct measurement of a limited number (50) of clay crystals on HRTEM images.