Nitrogen influx was identified in the Harghita Bãi area, where the mechanism of NH4+-fixation in illitic clays is relevant for the N-input budget estimation. The nanotextural features of K-illite (K-I), NH4,K-I and NH4-illite-smectite (NH4-I-S) mixed layers observed in argillic-altered andesitic rocks from the hydrothermal area of Harghita Bãi (East Carpathians) were studied by X-ray diffraction, infrared spectroscopy and transmission and analytical electron microscopy (TEM-AEM). The texture of undisturbed argillic-altered andesite rocks exhibits chaotic intergrowths of randomly oriented and curved illitic packets with abundant pore spaces and high porosity between packets. The TEM images of K-I and NH4,K-I intergrowths show subparallel packets with clear contacts, exhibiting a diffuse contrast across layers. The thicknesses of K-I and NH4,K-I packets range from 150 to 500 Å, and 1Md and 1M polytypes were identified by selected area electron diffraction patterns. Crystal chemistry of K-I, NH4,K-I and NH4-I-S was carried out by AEM. A third interlayer cation Na+ beside K+ was detected in several NH4,K-I packets. The NH4,Na,K-I packets interleaved with NH4,K-I or NH4-I-S (12% smectite layers) packets were also identified by TEM. The thicknesses of NH4,Na,K-I packets range from 300 to 1200 Å, with abundant lenses and lenticular layer separation along the boundaries between them. The 1Md polytype dominates the NH4,Na,K-I packets. Straight and parallel packets, continuous 00l layers and collapsed swelling layers at the boundary of individual NH4-I (5% smectite layers) packets with thicknesses ranging from 20 to 95 Å were observed. The nanotextural observations indicate direct crystallization of NH4-I crystals within a NH4-I-S series from a pore fluid, where NH4-I packets occupy void spaces previously occupied by fluids.

Various approaches have been used for the preparation of heterostructured materials based on clay minerals, with numerous potential applications offered by the resulting functional materials. In this study, a fibrous clay mineral (palygorskite) and a tetraethyl orthosilicate reagent were used to obtain silica–palygorskite heterostructures. The aim was to highlight the influence of two factors during the preparation process: the effect of acid activation pre-treatment of the palygorskite with HCl and the effect of varying the length of the amine chains used – dodecylamine and butylamine – on the formation and development of silica nanoparticles on the surface of the palygorskite fibres. The silica–palygorskite heterostructures were obtained after the removal of the organic templates by calcination at 500°C. The textural and structural properties of the silica–palygorskite heterostructured samples were determined using various experimental characterization techniques, such as X-ray diffraction, transmission electron microscopy, gas adsorption and Fourier-transform infrared spectroscopy. The experimental variables targeted in this study appeared to have a significant effect on the textural properties of the silica–palygorskite heterostructure obtained. The great specific surface area and the mesoporous, microporous and ultramicroporous volumes as determined using nitrogen and/or carbon dioxide gas adsorption confirm the benefit of combining the acid activation pre-treatment of the fibrous clay mineral with the use of a long-chain amine co-surfactant (dodecylamine). The resulting silica–palygorskite heterostucture has a great specific surface area (628 m2 g–1) and a well-developed total pore network (VN2 = 0.24 cm3 g–1; Vultra (CO2) = 0.18 cm3 g–1). This material will be tested for the removal of volatile organic compounds at low concentrations.

Clays are used in the general production of earthen tiles. In this study, the production and characterization of earthen tiles from schist, a clayey rock formed by metamorphism of mudstone or shale, was investigated. The impact of tiles on atmospheric temperature through their absorption of the visible, near-infrared and far-infrared wavelength regions is evaluated. In particular, the absorption of ultraviolet and infrared radiation by the tiles was evaluated, as this could have beneficial applications for human health and the environment. UV-A radiation (320–400 nm) is not absorbed by the atmosphere, but schist materials absorb UV-A, which can contribute to melanoma formation (i.e. cancer). Field-emission scanning electron microscopy, X-ray fluorescence spectrometry and X-ray diffraction were used for the analysis of the schist materials. The tile-production stages of schist materials (drying, firing, water absorption rate, etc.) were tested at Hatipoglu Gunes Tile and Brick Industry, Inc. (Turkey). The tiles fired at 950°C and 1000°C comply with the industry standard compressive strength values for fired tiles (when converted to industry production conditions) and were 156.15 and 123.20 kg cm–2, respectively.

Nitrate contamination of surface waters and groundwater is one of the main problems associated with agricultural activities worldwide, and there is an urgent need to develop effective materials and processes to remove efficiently excess nitrate from aquatic environments. Bittern is a seawater resource that contains large amounts of Mg2+ and Ca2+, and its utilization has received much recent attention. In this study, an Fe-type layered double hydroxide (Fe-LDH) product was prepared from bittern with the addition of an inexpensive agent (FeCl3) for nitrate removal. The greatest nitrate removal was obtained for synthesis conditions of pH 8.5–9.5 at 50°C for 0.5 h. The equilibrium adsorption capacity of the product for nitrate was measured and fitted with the Langmuir and Freundlich isotherm models. The experimental data better fit the Langmuir model than the Freundlich model. The calculated maximum adsorption capacity for nitrate was 0.40 mmol g–1, which was greater than those of other reported nitrate adsorbents. The product removed nitrate ions from a highly saline solution. The order of interference of anion species for nitrate removal was CO32– > SO42– > Br– > NO2– > Cl– > F–. The pH of the solution and removal of nitrate increased with increasing solution temperature because of ion exchange between the Cl– in Fe-LDH and the NO3– in the solution. Nitrate ions were repeatedly adsorbed and desorbed. The prepared Fe-LDH is expected to be a new inorganic anion exchanger for the removal and recovery of nitrate ions from aquatic environments.

Dans ce travail, nous avons determine les caractéristiques des états d'équilibre de la montmorillonite calcique placée dans la phase vapeur délivrée par des solutions aqueuses d'éthane 1·2 diol, de propane 1·2 diol, de propane 1·3 diol, de butane 1·3 diol, de butane 1·4 diol et de butane 2-3 diol.

Les diagrammes de sélectivité, calculés à partir des isothermes d'adsorption, la diffraction des rayons X et la spectroscopic infrarouge mettent en evidence l'existence de deux phases adsorbées ayant des caractéristiques très différentes.

1. (1) Une phase interagrégat dont la composition est égale à celle de la solution d'équilibre.

2. (2) Une phase interfoliaire dont les caractéristiques sont étroitement liées à la stéréochimie de la molécule organique.

Les différents états stables mis en evidence s'expliquent par les energies mises en jeu par les interactions cations dipoles et les liaisons hydrogène intermoléculaires.

Temperature programmed desorption (TPD) and IR spectroscopy were used to examine the desorption of pyridine, 2-methyl-, 4-methyl- and 2,6-dimethylpyridine from Al3+- and Cr3+-montmorillonite. Pyridine desorbed from Lewis sites at 150°C and from Bronsted sites at 340°C. 4-methylpyridine desorbed from Lewis and Bronsted centres at 210°C and 410°C respectively, some 60°C higher than pyridine due to its higher basicity. Conversely, the 2-methyl- and 2,6-dimethylpyridine, which are sterically hampered with respect to their coordination to Lewis centres, desorbed from these sites near 100°C, but due to their greater basicity desorbed from Bronsted sites at higher temperatures. These interpretations were confirmed by IR spectroscopy.

Dodecyl dimethyl benzyl ammonium (DDBA) is a novel cation surfactant used to modify clay minerals. DDBA-intercalated montmorillonite is formed by the ion exchange between DDBA cations in the solution and cations in the montmorillonite interlayers. By using molecular dynamics simulations, we investigated the basal spacings, interlayer structures and dynamics of DDBA-montmorillonites. The results showed that the calculated basal spacings agreed well with experimental values and that the layering behaviours of DDBA had been revealed. The ammonium groups of DDBA ions preferred staying close to the centre of Si–O six-member rings. The benzyl group and lauryl group were oriented in parallel in the monolayer state, whereas they were tilted in other states. DDBA ions have very low mobility in the interlayer region, indicating that the negatively charged montmorillonite surfaces can effectively fix this positively charged surfactant. The microscopic structures and dynamics obtained in the present study provide atomic-scale insights into the properties of DDBA-intercalated clay minerals.

This research aims to characterize the mineralogical and crystal-chemical purity of two samples of natural talc (BTT6, BTT7) from the occurrence ‘Ecole1’ in the deposit of Minzanzala, southwest Gabon. X-ray diffraction and modal-composition calculations demonstrated the presence of quartz and Al–Fe-bearing phases (kaolinite and/or chlorite and/or Al–Fe oxyhydroxides) as accessory minerals in both ores. In contrast, the chemical and spectroscopic characterization of the talc component revealed remarkable chemical purity expressed by very low Fe contents. According to these results, the talc of Minzanzala might be used as a filler in a wide range of industrial applications, such as in cosmetics, paints, polymers or ceramics.

This paper presents systematic molecular dynamics modelling of Na-montmorillonite subjected to uniaxial compression and unidirectional shearing. An initial 3D model of a single-cell Na-montmorillonite structure is established using the Build Crystal module. The space group is C2/m, and COMPASS force fields are applied. Hydration analysis of Na-montmorillonite has been performed to validate the simulation procedures, where the number of absorbed water molecules varied with respect to the various lattice parameters. A series of uniaxial compression stress σzz and unidirectional shear stress τxy values are applied to the Na-montmorillonite structure. It is shown that the lattice parameter and hydration degree exhibit significant influence on the stress–strain relationship of Na-montmorillonite. The ultimate strain increases with increases in the lattice parameter but decreases in the number of water molecules. For saturated Na-montmorillonite, more water molecules result in a stiffer clay mineral under uniaxial compression and unidirectional shearing.

A sericite from Unnan Mine, Shimane Prefecture, Japan, has a three-layer structure, perhaps similar to three-layer phlogopite and lepidolite, but with various degrees of disorder in inter-layer stacking, in different samples. A classification of polymorphic and disordered forms, showing their relationship, is proposed.

Because chlorite represents the highest order of mineral having a montmorillonite-illite like structure, it has been studied by the d.t.a. technique in water vapour atmospheres at pressures (absolute) in the range 0·001 mm of Hg to 2300 mm of Hg. The range of water vapour pressure makes profound changes in the thermograms, showing the very complex nature of the breakdown of the brucite-like layer which was not anticipated by other tests. The chlorite exotherm at 870°C can be completely suppressed by high pressure water vapour or can be greatly intensified by running in vacuum. The great differences in thermograms cannot be explained by chemical analyses or optical properties.

Le Grès à Voltzia des Vosges du Nord est formé de bancs gréseux et de lentilles argileuses. Les illites extraites des bancs gréseux montrent au microscope électronique des formes en lattes alors que celles des lentilles argileuses ont des contours pseudohexagonaux. Lorsqu'on broie une muscovite dans de l'eau désionisée avec du sable de Fontainebleau on retrouve ces deux formes, en lattes et pseudohexagonales. Les deux formes de particules peuvent donc être engendrées par un mème materiel initial.

Une hypothèse a été faite quant à la formation des illites en lattes. Elles seraient le résultat d'une dissection de particules micacées le long des rangées de substitution [10], [11] et [1] du silicium tétraédrique par de l'aluminium avec perte d'une partie de cet aluminium. Des analyses chimiques et des observations au microscope électronique ont été faites sur des particules de muscovite broyée. Les résultats obtenus vont dans le sens de l'hypothèse émise mais ne sont pas suffisants pour la démontrer pleinement.

Water released by dehydroxylation was trapped in clay compacts during reactive hot pressing. The dynamic conditions of water pressure and temperature produced in the compacts modified the high temperature reactions of kaolinite. Kaolinite was converted to pyrophyllite or mullite in the temperature range 600-700°C depending on the applied pressure. Oriented aggregates of clay were used to determine orientational relationships between kaolinite and the high temperature phases. Structural continuity was observed in the reactions through the basal planes of kaolinite and pyrophyllite to the (130) plane of mullite.

Mineralogical examination of a strongly chloritized amphibole-schist indicated that it had been subjected to two alteration episodes of different origin. Structural and petrographic evidence showed that the alteration processes operated per descensum from the bedrock surface down to shallow depth, thus eliminating any hydrothermal episode due to fluid ascension through deep fractures. The rock was first altered into interstratified chlorite-vermiculite minerals with potassic interlayers. These potassic clay minerals occur in an originally K-deficient rock and seem to have been generated by a marine alteration episode; this episode appears to be contemporaneous with the Cenomanian transgression which covered the amphibole-schist with sandy-clayey deposits. The potassic clay minerals were replaced during a later meteoric alteration episode by kaolinites, iron oxides, and smectites with Mg, Ca interlayer cations.

The hydrothermal reaction of kaolinite in the system Na2O-K2O-MgO-Al2O3-SiO2- H2O-HCl, at near-neutral pH conditions, has been investigated at 200ºC, for times from 12 h to 180 days. X-ray diffraction (XRD) study of the solid products indicates that the phases formed from 15 days’ reaction time are randomly ordered mixed-layer chlorite-smectite, dioctahedral on average, with a chlorite:smectite ratio of ∼1:2. No structural evolution was observed with increasing reaction time. Investigation by transmission electron microscopy revealed, on the contrary, that very thin packets with basal spacing of either 10 Å (smectite) or 14 Å (chlorite) are dominant. In addition, packets with periodicities of 12 –13 Å are also observed. Only rarely, randomly to ordered sequences of 10 and 14 Å are observed in the packets. These observations indicate that the mixture of these phases behaves in XRD as randomly ordered mixed-layer chlorite-smectite. Chemical analysis of the solutions suggests that the neo-formed phases are metastable and would evolve, at longer reaction times, toward ordered mixed-layer chlorite-smectite or to clinochlore.

The mineralogical composition of the clay, silt and sand fractions from soil profiles representative of four of Ceylon's major soil groups have been determined using X-ray, differential thermal, optical and chemical methods. The results show that the mineral assemblages in these fractions can be correlated with the pedogenesis and the degree of maturity of the profile.

General techniques for specimen preparation are described, including formation of supporting films and surface replicas, and methods for dispersion of clays.