The ‘Fischschiefer formation’ has been identified as the likely source rock for petroleum in the western Molasse Basin of Austria. The investigated cores originate from different depths (1242 m to 4294 m) of the Fischschiefer horizon. The illitization observed in the <0.2 μm fraction proceeds slowly, probably because of the low geothermal gradient (3°C/100 m) in the Molasse Basin. The illite content in illite-smectite ranges from 30% (randomly ordered) for the shallowest sample to 65% (R0+R1 ordering) for the deepest sample. The oxygen index (OI) vs. hydrogen index (HI) plot implies type I to II kerogen for the organic matter. Vitrinite reflectance and Rock Eval parameters indicate an immature stage in the diagenesis of kerogen. Only the deepest sample (4294 m, 0.6% Rr) reaches the early oil window. There is a good correlation of the illitization trend of the mixed-layer mineral I-S and the organic maturity parameters.

The effect of a Mg- and Al-containing layered double hydroxide (LDH), used as an additive or as a matrix, on the dissolution and solubility of two non-steroidal anti-inflammatory drugs (NSAIDs), namely, mefenamic and meclofenamic acids, is reported. The use of MgAl-LDH enhances the solubility of mefenamic acid at the three pH values tested, and the value is larger when the acid is intercalated as opposed to simply being mixed with the layered material. For pure mefenamic acid, the most unfavourable pH is 1.2, while for the physical mixture and the sample with the intercalated drug, the most unfavourable pH is 4.5, for which the minimum increase in the amount of dissolved acid is recorded. The (dissolution) release-rate for both drugs when they are intercalated between the layers is much slower than for the physical mixture or for the dissolution of the pure drug.

The conductivity of La-montmorillonite was measured in the domain of water relative pressures (p/p0) of <1, and compared with the conductivites of Li- and Na-montmorillonite. La-montmorillonite shows smaller conductivity over the whole range of p/p0 studied. To explain this, theoretical considerations of the polarizing power and of the local stacking order induced by the exchangeable cation were addressed.

L'argile blanche en provenance du sol ferrallitique dérivé de matériaux pyroclastiques de Vaté (Vanuatu) possède un rapport moléculaire SiO2/(Al2O3 + Fe2O3) proche de 2, est riche en fer (∼7% Fe2O3) et se présente sous forme de fines lamelles irrégulières et parfois froissées. Sous l'effet de tout traitement de déshydratation, l'espacement basal de cette argile passe progressivement de 10 Å vers 7 Å. Toutes ces caractéristiques permettraient son identification comme halloysite (10 Å) ferrifère hydratée. Cependant, les spectres de diffraction des rayons X de cette argile déshydratée puis déshydroxylée ne correspondent pas à ceux que l'on obtient pour une halloysite ‘normale’. Ils révèlent plutôt la présence d'un édifice interstratifié 1:1/2:1 où le minéral 2:1, présent à raison de 20% environ, est dioctaédrique. En outre, la CEC de ce matériau (∼44 mEq/100 g à pH 4) est anormalement élevée pour un minéral 1:1. Par spectroscopie Mössbauer, on établit que la quasi-totalité du fer présent dans cet échantillon doit être localisée en position octaédrique au sein d'un phyllosilicate. Comme ce fer est ferrique, son inclusion dans la couche octaédrique d'un minéral 1:1 ne pourrait justifier l'importante charge négative permanente que porte cette argile. En réalité, toutes les propriétés reconnues pour ce matériau justifient son identification comme minéral interstratififé de 80% environ d'halloysite et de 20% de smectite ferrifère. Certaines particularités des spectres d'infrarouge, notamment l'absence des bandes à 3560 et 820 cm−1 caractéristiques des vibrations d'élongation et de déformation des hydroxyles de la nontronite, suggèrent que la smectite ferrifère inclue dans l'édifice interstratifié pourrait être une hisingérite dioctaédrique.

The chemical and sorption properties of clay minerals from the Mako area, Senegal, were investigated using FTIR spectroscopy, X-ray diffraction, scanning electron microscopy equipped with an X-ray energy dispersion spectrometer, thermal analysis and chemical analysis. The clay sample is essentially dominated by kaolinite and quartz as also shown by treatment with ethylene glycol and dimethylsulfoxide (DMSO). The clay fraction of this natural clay was organically modified by grafting with 3-aminopropyltriethoxysilane (APTES) in order to improve significantly its retention ability of heavy metals. The silane groups of the APTES reagent were partly grafted on the surface of platy kaolinite particles and the remaining ethoxy groups could be hydrolysed by aqueous treatment. The natural clay, its clay fraction and the organo-functionalized clay (with APTES) were investigated as adsorbents for the removal of Pb(II) from aqueous solutions. Evidence for an organic grafting has been demonstrated by comparing the spectroscopic characteristics of the natural clay and those of its chemically modified derivatives. The effects of different parameters (i.e. initial Pb(II) concentration and contact time) on the adsorption efficiency were studied. For an initial concentration of 10 mg L−1 Pb(II), the adsorption was maximized after 30 min contact time both for the raw material and its clay fraction and after 90 min for the APTES grafted clay. Although the maximum of sorption for the APTES grafted clay is reached with slower kinetics, this maximum amount of Pb(II) uptake at room temperature (Xmax) is significantly higher since it is 0.99 mg g−1 for the raw clay, 1.46 mg g−1 for its clay fraction and 3.02 mg g−1 for the organically modified clay, i.e. three times greater than the raw clay.

The adsorption of the metachromic dye acridine orange (AO) by Na-beidellite was investigated by visible spectroscopy. Different types of clay-AO association were identified from the appearance and location of absorption bands α or β. The colloidal properties were determined from curves of the absorbance vs. the degree of saturation. Three regions were identified in the absorbance curve. In the first region beidellite is peptized with small amounts of AO and the dye penetrates into the interlayer space where it undergoes metachromasy due to π interactions between the aromatic entity and the oxygen plane of the clay. With larger amounts of AO (second region), the clay flocculates due to the aggregation of the dye cations in the interparticle space of the flocs. In excess AO (third region), beidellite is gradually peptized, forming small tactoids with monomeric AO in the interlayer space and at the same time adsorbing dimeric and polymeric AO cationic species at the solid-liquid interface. Compared with the other smectites, AO shows the greatest tendency to undergo metachromasy in the presence of beidellite.

The Carrión lacustrine basin (≈10 km2), central Spain, is filled with Neogene-Quaternary sediments (20–25 m thick) rich in palygorskite. Two clay units of ∼15 m thick are of particular interest in the basin. The lower one contains over 75% phyllosilicates (palygorskite up to 90%, smectites and illite) in marginal areas (facies A), and it is laterally bound by a distal facies (B) also rich in clay minerals (smectites and illite, and some palygorskite) and gypsum, and includes dolomitic marl intercalations. The composition at the top is primarily marly, with some gypsum (C). The upper clay unit, mainly clay-size material, (D) is rich in smectites, palygorskite and sepiolite, and contains carbonate intercalations near the top. A statistical treatment of the mineralogical and chemical composition data from 120 samples, using principal factor analysis, suggests that: (a) illite and smectite are detrital in origin; (b) palygorskite was formed by transformation of illite and smectite involving reaction with Mg; and (c) sepiolite was a neoformation product favoured by evaporation of silica- and Mg-bearing waters.

Mössbauer spectra have been obtained at room temperature on a series of phlogopites and biotites which have also been characterized by chemical analyses, I.R. and N.M.R. The distribution of the Fe2+ ions on the two possible octahedral sites is on the average nearly random. A clear example of tetrahedrally coordinated Fe3+ ions in a natural phlogopite is given. This phlogopite has a very high vermiculitization ability. The Fe3+ content of the samples has been determined by two different chemical methods and it is shown that even when precautions are taken to minimize oxidation, the agreement with Mössbauer spectra is poor.

Short-chain alkylammonium derivatives of montmorillonite (< 8 or 10 C atoms in the alkyl chain) adsorb alcohols in the micropores between the alkylammonium ions. The external surface area and the micropore volume are derived from comparison plots of ethanol and butanol adsorption isotherms. The micropore volume varies between ∼0 (decylammonium derivative) and 100µl/g (methylammonium derivative); the external surface area determined by ethanol and butanol gas adsorption is about 50 m2/g, and is almost independent of the alkyl chain length. In contact with the alcohols, the alkylammonium ions in the interlayer space remain in h1 or h2 arrangement (monolayers or bilayers of flat-lying alkylammonium ions); on the external surface they move into an upward position. The heat of immersion decreases strongly with increasing alkyl chain length to a minimum for decylammonium ions, the variation being very similar for ethanol, butanol, hexanol, octanol and decanol. Immersion in ethanol increases the external surface area at the expense of the internal surface area. In butanol and longer alcohols this area remains unchanged. The increase of the external surface is related mainly to changes in the less ordered regions around the core of the crystals which consists of coherent silicate layers. The heat of wetting is ∼ 110 mJ/m2 (external and internal surfaces). The integral enthalpy of adsorption of butanol, 40–50 kJ/mol, is independent of the alkyl chain length (nc ≤ 8).

The present study, which was carried out on a deep weathering profile of quartz diorite in the San'in district, Japan, along with two lateritic samples from India and Sri Lanka, provides convincing evidence supporting the dissolution and recrystallization mechanism for the halloysite-to-kaolinite transformation during weathering of crystalline rocks. In all the samples studied, tubular halloysite formed prior to kaolinite via the dissolution of feldspars and precipitation from solution. The crystal size distribution of tubular halloysite formed early was characterized by a lognormal curve having a positive asymmetry. When the activity of water decreased in the weathering profile, halloysite as well as goethite began to dehydrate, which acted as a trigger for dissolving halloysite. The heterogeneous nucleation of kaolinite took place on the edges and in the shrinkage pores of dehydrated halloysite tubes. The topotactic relationship of b*halloysite//b*kaolinite was kept between the substrate halloysite and the product kaolinite in the incipient growing stages of kaolinite. As a consequence, early formed halloysite transforms to kaolinite in a cannibalistic manner over a long period of time, owing to the intermittent supply of solution undersaturated with respect to halloysite in natural open systems.

Differential thermal analysis curves were obtained for a series of diamine and glycol complexes with natural and copper substituted montmorillonite, in air and in an inert atmosphere. Thermobalance curves of the diamine-clay systems were also determined. The exothermic peaks observed in air are characteristic for any particular system and reflect the nature and binding of the interlamellar material; no direct correlation was, however, observed with pyrolysis and oxidation processes in the clay. Organic matter is frequently liberated from the clay before oxidation, which then occurs within the reaction cell but outside the clay phase. The extent to which oxidation is completed at any particular temperature depends upon the supply of oxygen and the amount of organic material present.

Dans ce travail on a étudié l'influence des conditions expérimentales du traitement acide d'une sépiolite sur la vitesse d'extraction des ions Mg et la variation des propriétés texturales des produits résultants. On a élaboré un modèle cinétique pour l'attaque acide de la sépiolite ce qui nous a permis de calculer les paramètres cinétiques et, en dernier lieu d'obtenir des valeurs pour l'energie d'activation du processus.

An X-ray diffraction study of over 600 specimens has shown that the Tertiary sediments of the Hampshire Basin are divided into two clay mineral provinces. The western province is characterized by kaolin from the West Country granites whilst the highly montmorillonitic sediments of the eastern province were partially derived from the dissolution of Chalk by tropical weathering.

Glauconite and Ca phosphate peloids occur in Jurassic and Cretaceous bioclastic carbonate rocks from pelagic swell sequences of the Algayat-Crevillente Unit (Subbetic Zone). The size and morphology of the peloids are controlled by the bioclasts. The glauconite in both stratigraphic positions is K rich (>0.69 atoms p.f.u.) and shows well-defined 10 Å. lattice fringes. Poorly crystalline areas with a composition of Fe-smectite are found within the peloids, indicating the nature of the glauconitic precursor. This precursor would be formed in the shielded microenvironments of the bioclast and later transformed to glauconite by equilibration of peloids with sea water that culminated with the crystallization of a phosphatic phase. The greater presence of smectite areas in the Jurassic peloids and the lower K contents (0.69-0.81) of these glauconites, compared with the Cretaceous glauconites (0.81-0.89) can be explained by the calcitic early diagenetic cementation which stopped the process of glauconitization.

Variegated palaeosols, which formed from weathering of clays, silts and brackish to freshwater limestones, are present in the Late Eocene–Early Oligocene Solent Group of the Hampshire Basin, southern UK. The composition and origin of the clay in three segments of the lower part of the Solent Group have been investigated by X-ray diffraction, microprobe analysis, inductively coupled plasma-mas spectrometry, K/Ar dating, high resolution scanning electron microscopy, analytical transmission electron microscopy and wet chemistry. The detrital clay mineral suite is dominated by illite and smectite with minor kaolinite and chlorite. Seasonal wetting and drying in gley soils has resulted in replacement of smectite by Fe-rich, or illite-rich illitesmectite. Illite has also formed with gypsum and calcite in ephemeral hypersaline alkaline lakes that periodically dried out. This illite may have precipitated directly from solution. X-ray diffraction data and probe analyses indicate that the neoformed illite is Fe-rich. The K and Fe for the illitization are thought to be derived from weathered glauconite reworked from the underlying Bracklesham Group and Barton Beds.

A series of Cu-substituted goethites, single and co-substituted with Cr, Zn, Cd and/or Pb was prepared, having molar ratios equal to 2.00, 3.33 and 5.00 mol%. All the samples contained only goethite, except Cu-, (Cu,Zn)- and (Cu,Pb)-samples synthesized at 5.00 mol% where hematite was also formed. The presence of Cr/Cd suppressed the hematite-forming effects of Cu. The general sequence of metal entry into the single-metal-substituted goethites was Zn = Cr > Cd > Cu > Pb and in di- (5.00 mol%) and tri- (3.33 mol%) metal-substituted goethites was Cu > Zn > Cd > Cr >> Pb. Cu incorporation increased all the unit-cell parameters in single-metal-substituted goethite, and these parameters increased in combination with other metals as follows: Cd > Zn > Cr > Pb in the multimetal-substituted goethites. The Cu-substituted goethite dissolved faster than pure goethite. Co substitutions of Cr/Pb reduced the dissolution rate (kFe), while substitutions of Cd/Zn increased kFe.

A nearly monomineralic 1.5 m thick bentonite bed sampled in Melo (Uruguay) appears to be a pure high-charge montmorillonite: [Si3.94Al0.06](Al1.40Fe3+0.11Ti0.02Mg0.49Mn0.01)O10 (OH)2Na0.01K0.08Ca0.18. However, contrasting swelling behaviours have been demonstrated by fitting the experimental X-ray diffraction patterns which were recorded on oriented preparations of the same sample in different saturation states. According to the expandability of the layers in the Ca-, K- and K-Ca-saturated (i.e. saturated first with K+ and subsequently with Ca2+) states, three ‘layer types’ were defined. Low-, intermediate-, and high-charge layers are fully, partly, and not expandable, respectively, after K-saturation. Collapse of high-charge layers is not reversible after subsequent Ca-saturation, probably because of tetrahedral substitutions. These three different layer types are segregated in two distinct randomly interstratified mixed-layer phases. Total surface area and cation exchange capacity are shown to depend on the interlayer cation composition.

Six smectites of different tetrahedral and octahedral compositions (SAz-1, Chambers, Belle Fourche, two subsamples of nontronite 33B and SWy-1) were Cs-exchanged and submitted to 70 wetting-and-drying cycles. X-ray diffraction (XRD) of oriented and glycolated mounts of the resultant material showed non-expandable layer proportions ranging from 15 to 60%. They were also analysed by powder XRD at 200°C in vacuum. These patterns showed that 15 – 40% of the layers were not rotated relative to each other and the rest were randomly rotated (no rotations of the 60° and 120° types). All layers had a d-spacing of 11 Å, corresponding to collapsed layers with Cs in the cavities created by the hexagonal rings of the tetrahedral sheets. Analysis of the number of cavities available in relation to the layer rotation shows that the rotation angle must be close to 30° or its multiples 90, 150, 210, 270 and 330°. X-ray diffraction and thermal analysis detected the same proportion of cis-and trans-vacant sites in the smectites. The ideal bdimensions of the tetrahedral and octahedral sheets (the sheets are considered independently, without deformation) were calculated for the samples used in this work and for others from the literature, using the tetrahedral and octahedral compositions. These ideal bdimensions have a strong positive correlation. The cis/transvacant character of the smectites is related to the relative lateral dimensions of the ideal tetrahedral and octahedral sheets. A possible explanation of this fact is offered, in which the different configurations of hydroxyls and oxide ions in cis- and trans-vacant structures can affect octahedralsheet dimension.

Four bands occur in the Mössbauer spectra of pelletal glauconites ranging in age from Cambrian to Oligocene. Components due to Fe3+ in the cis M(2) positions are visible in all the spectra but their shapes depend on the expanding layer content. In the spectrum of the Oligocene glauconite a very well-developed shoulder due to Fe2+ in the trans M(1) positions is observed. In the younger glauconites (15–20% expanding layers) the conventional assignments of the spectra indicate that Fe2+ occupies the trans M(1) positions, the cis M(2) positions being vacant. Conversely, in the Palaeozoic samples (~5% expanding layers) the cis occupancy significantly prevails over trans occupancy.