A series of organo-montmorillonites and organo-hectorites was prepared by complete ion-exchange from the pure sodium form of the parent smectites. The organic cations were tetramethylammonium, trimethylated quaternary ammonium derivatives of the lysine and of the ornithine methyl esters, quaternarized polyammonium cations, or tetraphenylphosphonium (TPP). These organo-smectites were used as packing material for gas chromatography columns. Mixtures of light hydrocarbons (methane to n-butane; “C1” to “C4”) could be separated. The degree of separation depends on the presence of micropores or of organophilic mesopores. The BET surface area, the micropore and mesopore volumes, as well as the size distribution of micropores and mesopores were measured for several systems. As a general trend, the retention times of the light hydrocarbons decrease with an increase of the micropore volume. In the case of TPP-montmorillonite, characterized by a large mesopore volume but for which no microporosity could be detected, separation of longer linear hydrocarbons (n-pentane to n-octane) could also be achieved.

Structural Fe3+ in kaolinites and dickites covering a broad range of disorder was investigated using electron paramagnetic resonance (EPR) spectroscopy at both the X and Q-band frequencies. A procedure based on a numerical diagonalization of the spin Hamiltonian was used to accurately determine the second and fourth-order fine-structure parameters. A least-squares fitting method was also developed to model the EPR spectra of Fe3+ ions in disordered local environments, including multimodal site-to-site distributions. Satisfactory fits between calculated and observed X and Q-band spectra were obtained regardless of the stacking order of the samples.

In well-ordered kaolinite, Fe3+ ions are equally substituted in sites of axial symmetry (Fe(II)sites, namely Fe(II)a and Fe(II)b) which were determined to be the two non-equivalent Al1 and Al2 sites of the kaolinite structure. In dickite, Fe3+ ions were also found to be equally substituted for Al3+ in the two non-equivalent Al sites of the dickite structure. In poorly ordered kaolinites, the distribution of the fine-structure parameters indicates that Fe3+ ions are distributed between Fe(II) sites and other sites with the symmetry of the dickite sites.

Hence, when stacking disorder prevails over local perturbations of the structure, the near isotropic resonance owing to Fe3+ ions in rhombically distorted sites (Fe(I) sites) is a diagnostic feature for the occurrence of C-layers in the kaolinite structure, where C refers to a specific distribution of vacant octahedral sites in successive layers.

A series of natural clays, including 1:1 layer silicates (serpentines, kaolin minerals), smectites, vermiculite, micas, talc, pyrophyllite, sepiolite, and palygorskite, were studied by 19F magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 19F chemical shift in these layer silicates is characteristic of the structure, in particular, to the local octahedral cation occupancy. Fluoride ions bonded to three Mg octahedral cations have a chemical shift of about −177 ppm and those bonded to two Al cations and a vacancy have a chemical shift of about −134 parts per million (ppm). The shift at −182.8 ppm in hectorite is apparently associated with fluoride bonded to two Al cations and a Li cation. Surprisingly, the difference in chemical shift of the interlayer and inner fluoride in 1:1 layer silicates is insufficient to distinguish these sites. Based on trends in chemical shift, it appears that fluoride substitution for inner hydroxyls in clays with octahedral substitution is not random. Fluoride is apparently preferentially associated with Mg rather than Al in the octahedral sheet as no resonance due to a fluoride bonded to two Al cations and a vacancy is observed in clays such as SAz-1.

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.

Intercalation complexes of a Hungarian kaolinite were prepared with hydrazine and potassium acetate. The thermal behavior and decomposition of the kaolinite-potassium acetate complex was studied by simultaneous TA-EGA, XRD, and FTIR methods. The intercalation complex is stable up to 300°C, and decomposition takes place in two stages after melting of potassium acetate intercalated in the interlayer spaces. Dehydroxylation occurred, in the presence of a molten phase, at a lower temperature than for the pure kaolinite. FTIR studies revealed that there is a sequence of dehydroxylation for the various OH groups of intercalated kaolinite. The reaction mechanism was followed up to 1000°C via identification of the gaseous and solid decomposition products formed: H2O, CO2, CO, C3H6O, intercalated phases with basal spacings of 14.1 Å, 11.5 Å, and 8.5 Å as well as elemental carbon, K4H2(CO3)3 · 1.5H2O, K2CO3 · 1.5H2O, and KAlSiO4.

The basal spacings of complexes of saponite with five cationic dyes, 1,1′-diethyl-2,2′-cyanine, crystal violet, methylene blue, 1,1′-diethyl-2,2′-carbocyanine, and 1,1′-diethyl-2,2′-dicarbocyanine, varied with degree of saturation of each dye. At low loading of dye to saponite, each cationic dye showed nearly the same absorption spectrum in the UV-visible region as that of its dilute aqueous solution, whereas the spectrum changed distinctly at high loading. With increasing degree of dye loading, the absorption band shifted to longer wavelength for 1,1′-diethyl-2,2′-cyanine (J band) and to shorter wavelength for the others (D, H bands). On the basis of the basal spacing of each respective dye-clay complex, the orientation of the intercalated dye molecules is proposed as follows: the major plane of the cationic dye lies horizontal to the 2:1 layer surface at low loading. With increasing loading, the dye molecules interact with adjacent dye molecules and orient vertically to the 2:1 layer at high loading near the cation-exchange capacity.

Kaolinite was converted into illitic clays in a 2.58 m KOH solution in gold capsules using cold-seal pressure vessels at 225°, 250°, 300°, and 350°C and 500 bars. The XRD shows that the major reaction products are illitic clays with no interlayer expandability. The TEM shows that the illitic clays appear mainly platelet-like with a K/Si ratio close to that of muscovite/illite. The extent of the conversion was monitored by measuring the XRD peak ratio of muscovite (illite) and kaolinite in quenched run products. The results reveal that kaolinite converts to muscovite/illite in the KOH solution at an initial rate two to three orders of magnitude faster than that of similar reactions at near-neutral conditions.

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.

The clay fraction of a Spodosol and its parent rock in the Apennine mountains of central Italy were studied by powder X-raydiffraction (XRD) and infrared (IR) spectroscopy, to evaluate the possibility of transformation of chlorite into low-charge expandable minerals. Results indicated that the main phyllosilicate in the rock was a slightly weathered trioctahedral chlorite, rich in both Mg and Fe, together with dioctahedral mica and minor amounts of kaolinite. In the BC horizon, chlorite has undergone partial transformation into 2 vermiculitic components, in 1 of which the interlayer could be removed by hot Na-citrate treatment; the presence of a regular interstratified mineral (high-charge corrensite) was also observed. Further changes in the structure of chlorite were detected in the Bsl horizon, becoming more evident towards the soil surface. The first stage of weathering of chlorite involved Fe oxidation and partial expulsion of Mg from the hydroxide sheet, followed by deposition of Al in the interlayer space. Iron is also removed from the interlayer sheet, possibly remaining, in the oxidized state, in the 2:1 octahedral sheet, and so contributing to the lowering of layer charge and transformation to a dioctahedral structure. When approaching the surface, Al removal from the interlayers is enhanced by complexing agents, and further charge reduction leads to the formation of 2:1 minerals with a smectite nature. Illite, because of its low content in the soil clay fraction, contributes marginally to this weathering sequence, forming the high charged expandable component observed in the Bhs horizon. At the soil surface, arandomly interstratified vermiculite/illite was detected, which probably originated from K fixation by the higher-charged expandable minerals. This study of weathering in a natural soil strongly supports the hypothesis, previously ascertained by laboratory experiments, that chlorite can transform into a low-charge expandable mineral.

Terra rossa samples were taken from the B horizons of soil profiles and from cracks within limestone in Italy. The average annual temperature (AAT) of the sites ranged from 8.4 to 20.3°C and the average annual precipitation (AAP) from 511 to 3113 mm, with either a 5–6 month water deficit or a large water surplus. Goethite and hematite were identified in all the samples. Under a moist (> 1700 mm AAP) and cool (13°C AAT) climate, a xeric, hematitic pedoenvironment was preserved by the well-litified carbonate rock. Hematite occurred in trace amounts, even with an AAT of 8.4°C and an AAP of 3300 mm, confirming the specific role of the hard limestone on the pedoclimate of terra rossa. The lowest mean crystallite dimension of goethite and hematite was found in the samples from the wettest sites, and in these samples hematite was nearly free of Al substitution. Rubification in terra rossa appeared to be due to the specific pedoenvironment. The hematite cannot be considered a relict phase formed under another climate. Illite and kaolinite were the main clay minerals in samples from xeric sites whereas more weathered clays, such as Al-interlayered vermiculite, occurred in cool, moist sites. We postulate that the processes of rubification and vermiculitization could have taken place at the same time.

Sediments from depths to 670 m in the Barbados accretionary complex and transecting the décollement zone have been studied by transmission and analytical electron microscopy (TEM/AEM). The sediments consist of claystone and mudstone intercalated with layers of volcanic ash. Smectite comprises the bulk of the noncalcareous sediments and forms a continuous matrix enveloping sparse, irregular, large grains of illite, chlorite, kaolinite and mixed-layer illite/chlorite of detrital origin at all depths. The detrital origin of illite is implied by illite-smectite textural relations, well-ordered 2M polytypism, and a muscovite-like composition. K is the dominant interlayer cation in smectite at all depths, in contrast to the Na and Ca that are normally present in similar rocks.

Deeper samples associated with the décollement zone contain small (up to 100 Å thick) illite packets included within still-dominant subparallel layers of contiguous smectite. AEM analyses of these packets imply illite-like compositions. Selected area electron diffraction (SAED) patterns show that this illite is the 1Md polytype. Packets display step-like terminations like those seen in illite of hydrothermal origin. The data collectively demonstrate that smectite transforms progressively to illite via a dissolution-recrystallization process within a depleting matrix of smectite, and not by a mechanism of layer replacement. This illite seems to form at depths as shallow as 500 m and temperatures of 20°-30°C, which is in marked contrast to the much higher temperature conditions normally assumed for this transformation. This implies that the high water/rock ratios associated with the décollement zone are significant in promoting reaction.

The hydrolysis of 2-(2-trichlorosilylethyl)pyridine (TCSEP) or 3-aminopropyltrimethoxysilane (APTMS) yields a complex mixture of oligomers, the composition of which is a function of time. 29Si NMR measurements show that the same oligosilsesquioxanes can be obtained from both compounds after prolonged hydrolysis. Ion exchange by montmorillonite with the pillaring solution obtained from TCSEP results in partial intercalation, with a noticeable fraction of the clay exchange sites occupied by protons not by the Si cationic species. Calcination of this pillared clay results in a mixture of phases showing 1.86 or 1.56 nm basal spacings. Pillaring of the same montmorillonite by the solution obtained by partial hydrolysis of APTMS results in a homogeneous solid with a basal spacing of 2 nm, which reduces to 1.65 nm upon calcination above 773 K. The microporous volume (pores < 1 nm) of these Si-clays, determined after calcination at 773 K, 0.15 ml/g for the PILC obtained from TCSEP, and 0.186 ml/g for the PILC obtained from APTMS is comparable to that measured for Al or Zr pillared clays. A better thermal stability is observed for the clay pillared by APTMS, which retains a large microporosity (0.167 ml/g) up to 973 K in air. These Si-pillared clays show a small number of weakly acidic sites and some strongly acidic sites retaining ammonia up to 723 K, which are most likely localized on the clay layers.

Greigites from a gley and a Tertiary sediment were investigated by X-ray diffraction and Mössbauer spectroscopy. The cell-edge length a of 9.8639 Å ± 0.0003 Å for the soil greigite was significantly smaller than that of the sedimentary greigite (9.8737 Å ± 0.0004 Å), but both cell-edge lengths were smaller than the value given on JCPDS card #16-713 (9.876 Å). Both greigites had 440 as strongest peak rather than 311 (as indicated on JCPDS card #16-713), but the other relative intensities did not deviate from the values given on this card within experimental error. Mean X-ray diffraction coherence lengths of 23 ± 2 nm for the soil greigite and of 60 ± 5 nm for the sedimentary greigite suggest superparamagnetic behavior. Mössbauer spectra nevertheless comprised two sextets with hyperfine fields of about 31.2 T (tetrahedral sites) and 30.7 T (octahedral sites), which resemble published values. It is postulated that aggregation may play an important role in determining the magnetic properties of the described samples.

Clay mineralogical studies by X-ray diffraction performed on extracted <2-µm fractions do not always represent all clay mineral constituents present in the soil. In this work, transmission X-ray diffraction (TXRD) was applied to undisturbed microsamples of optically homogeneous mineral soil fabrics and features. These microsamples were isolated by microdrilling their periphery in soil thin sections, then removing them, and transferring them to glass capillaries for TXRD analysis. The usefulness of this technique for supplying in situ mineralogical information on identification, structure, and natural orientation of soil constituents was tested on mineral microfabrics and features of primary and secondary phyllosilicates. The study demonstrated that TXRD allowed detailed, representative interpretations of undisturbed mineral features and fabrics. In particular, this technique allowed us (1) to compare mineralogical compositions at selected microlocalities, (2) to study natural preferred orientations, and (3) to detect small amounts of minor mineral interstratification phases. In addition, complementary information on crystallography and crystal chemistry may be obtained by performing analytical transmission electron microscopy on the same microsample.

Oxygen isotope composition of three types of unique nodules which consist of amorphous silica-apatite, cristobalite-apatite and tridymite-apatite associations interspersed amidst basaltic pyroclastics from the Har Peres volcano, Golan Heights, Israel is reported. Unusual isotopic temperature (75°C estimated from oxygen isotope fractionation between cristobalite (δ18O = +25.5‰)-apatite (δ18O = +12.9‰) pair suggests that the nodule was not formed by present-day pedogenesis as has been previously proposed, but was a xenolith incorporated probably from the underlying siliceous phosphorites at a higher temperature. An observed negative oxygen isotopic fractionation (δ18O = −5.1‰) between tridymite (δ18O = +9.9‰) and associated apatite (δ18O = +15.0‰) is indicative of the nodular formation under disequilibrium conditions. A plausible mechanism of formation of the apatite (and calcite) associated with tridymite is an epitaxial overgrowth on template tridymite of magmatic origin under the current weathering regime. Oxygen isotopic evidence indicates a complicated origin for the nodules.

The sorption capacity of hydrotalcite (HT) and its calcined product (CHT) was evaluated for 131I− sorption from water solution and it was determined as a function of the calcining temperature. The radionuclide content was determined by γ-spectrometry. Solids were characterized by thermal analysis, X-ray diffraction (XRD), electron microscopy and Brunauer-Emmett-Teller (BET) analysis. For 0.1 M Na I solution, labeled with 131I−, sorption capacity was found to be 0.24 meq g−1 (7.2% of the anion exchange capacity, AEC). But, if the sample was previously calcined at 773 K and the HT structure destroyed, the sorption of I− increased considerably, up to 2.08 meq g−1 (63% of the AEC) and the HT structure was reconstructed. The 131I− sorption at very low concentrations (10−14M) was 0.04 × 10−14 meq of 131I− g−1 in the noncalcined HT, but for calcined samples at 773 K, the sorption increased to circa 0.97 × 10−14 meq g−1. Calcination temperature determines the surface area of the resulting mixed oxides, and that property seems to be the most important factor controlling the I− sorption. If the calcination temperature was increased to 873 K, the specific surface area of the oxide mixture increased and I− sorption increased as well, whereas calcination of HT at 973–1073 K resulted in a low surface area and a low I− retention.

The objectives of the study were to determine the chemical composition and layer charge of smectite found in calcareous till of the Interior Plains region of western Canada and to examine the effects of acidification on alteration of the smectite. Samples of acidified and non-acidified (calcareous) late-Wisconsin till were obtained from four soil pits located immediately adjacent to an elemental sulfur block located in southern Alberta. Samples of the surface material (0–10 cm depth) had been subjected to extreme acidity for 25 years due to the oxidation of elemental sulfur and displayed pH values of about 2.0. Samples of the till obtained at depth (65–75 cm) remained calcareous with pH values between 7.3 and 7.6. A combination of analytical methods was used to determine the chemical composition of the smectite found in the samples. The layer charge of the smectite was determined independently using X-ray diffraction data for n-alkylammoniurn saturated specimens. Smectite found in the non-acidified calcareous material was characteristic of montmorillonite with a low content of Fe and very little substitution of Al for Si in the tetrahedral sheet. The smectite had a structural formula of M+0.40(Si3.96Al0.04)(Al1.56Fe3+0.10Mg0.33)O10(OH)2, which compared well with a mean value for layer charge of 0.399 mol(−)/O10(OH)2 determined using X-ray diffraction data for n-alkylammonium treated specimens. Smectite remaining in the till material subjected to extreme acidity underwent incongruent dissolution with a net loss of layer charge and preferential loss of octahedral Mg.

A new chemical, Peldri II, is evaluated as a compound for drying soft clay materials. Peldri II, a fluorocarbon (1,1-difluorotetrachloroethane), is a solid at room temperature and is a liquid above 25°C. Clay gels are embedded in Peldri II by immersing them in the liquid and allowing it to solidify. Once solidified, Peldri II will sublime, with or without vacuum, to a dry specimen, probably without introducing surface tension. Wyoming montmorillonite saturated in 10−3 M NaCl and 1 M CaCl2 solutions has been examined to compare preservation of its initial structure after Peldri II, critical point, and freeze drying techniques. Transmission electron microscopy of ultrathin sections, scanning electron microscopy, and mercury intrusion porosimetry techniques were used. No differences were detected between Peldri II and critical point drying methods. Peldri II appears to be a significant improvement as an alternative drying agent for clay materials in studies of their structural properties. It is also very convenient for drying large numbers of samples.

Muscovite-kaolinite intergrowths found in Albian sandstones of the Basque Cantabrian basin (northern Spain) were studied by optical, scanning and electron microscopy and electron microprobe analysis. Kaolinitization begins at grain edges, forming the characteristic fanned-out textures, and propagates toward the interior along the cleavages of muscovite. Kaolinite and muscovite occur as thick packets, being free of interlayering. Phase boundaries between both minerals show bidimensional crystallographic continuity, and no intermediate phases have been identified. The data obtained suggest that muscovite only supplied a template suitable for the epitactic crystallization of kaolinite, while Al was available in sufficient amounts due to the dissolution of detrital K-feldspar. Very small packets of magnetite or maghemite showing a coherent orientation with the kaolinite crystals have been recognized, and could be responsible for the small Fe contents usually detected in electron microprobe analyses of kaolinite.

Textural relationships between authigenic kaolinite and deformation microstructures in the intergrowths, combined with previous information about burial conditions, show that alteration proceeded during a late stage of the diagenetic history, related to the uplift of the studied materials as a result of the Alpine orogeny.