A novel method to perform small-scale laboratory experiments that reproduce concrete–bentonite and concrete–groundwater interactions has been developed. Such interfaces will prevail in engineered barrier systems used for isolation of nuclear waste. With the goal of optimizing the experimental method, this work has analysed the geochemical interaction of distilled water, low-pH cement mortar and FEBEX-bentonite for 75 days. Limited but evident reactivity between the materials was observed, mainly decalcification in cement mortar, carbonation at the interface with bentonite and Mg enrichment in bentonite. These results are consistent with the state-of-the-art literature and were used to validate this small-scale pilot laboratory experiment to establish the basis for further studies comparing the behaviour of different buffer and cement materials.

The use of organoclays as adsorbents in the remediation of polluted water has been the subject of many recent studies. In the present work, a Tunisian smectite modified with two cationic surfactants was used as an adsorbent to examine the adsorption kinetics, isotherms and thermodynamic parameters of fluoride ions from aqueous solution. Various pH values, initial concentrations and temperatures have been tested. Two simplified kinetic models, first-order and pseudo-second-order, were used to predict the adsorption rate constants. It was found that the adsorption kinetics of fluoride onto modified smectites at different operating conditions can best be described by the pseudo-second-order model. Adsorption isotherms and equilibrium adsorption capacities were determined by the fitting of the experimental data to well known isotherm models including those of Langmuir and Freundlich. The results showed that the Langmuir model appears to fit the adsorption better than the Freundlich adsorption model for the adsorption of fluoride ions onto modified smectites. The equilibrium constants were used to calculate thermodynamic parameters, such as the change of free energy, enthalpy and entropy. Results of this study demonstrated the effectiveness and feasibility of organoclays for the removal of fluoride ions from aqueous solution.

Conflicting evidence has been published concerning the occurrence of an oxidation exothermic peak on differential thermal curves for NH4-saturated clay minerals. The present experiments show that this peak is affected by (a) the clay mineral concerned and (b) the nature of the thermocouple, Pt/PtRh thermocouples apparently acting as good catalysts for oxidation of released ammonia.

A lithium mica extracted magnetically from china stone is compared chemically and by X-ray methods with known lithium micas. This comparison shows a strong resemblance between the Cornish mica and zinnwaldite from the Zinnwald.

The use of thermal and acid treatments, prior to X-ray diffraction examination, for the identification of kaolinite and chlorite in mixture is discussed. Thermal treatment, although useful in confirming the presence of chlorite, cannot give definite information on the presence of kaolinite, but acid treatment is conclusive in this respect.

In this study, a new procedure for the synthesis of pillared clays is proposed. Ageing processes and intercalation reactions were carried out using microwave irradiation in order to decrease the consumption of three industrially-important parameters; time, water consumption and energy. The effects of microwave irradiation, the amount of Al and the Al3+/clay ratio on the physicochemical properties of Al-pillared montmorillonites were investigated. The structural changes, depending on the intercalation and microwave irradiation, were characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM) analyses and by measuring the specific surface area and pore-size distribution. Additionally, simultaneous thermal analyses (STA) and zeta potential measurements were carried out to determine physicochemical properties. According to the XRD measurements, the d001 value of microwave-irradiated samples is not affected by the amount of Al and the Al3+/clay ratio; microwave irradiation causes a 0.20 nm contraction in the d001 value in comparison to that of a conventionally pillared sample. The results of FTIR analyses reveal that the intensity of peaks assigned to Keggin-OH and Keggin-H2O stretches is diminished in the case of microwave-irradiated samples. The STA analyses indicate that the amount of water released during dehydroxylation is decreased in the case of microwave-irradiated samples. By considering the contraction in d001 values and the decreases in Keggin-stretching bands and also in the amount of dehydroxylation water, it was concluded that microwave irradiation has a calcination effect.

A pillared smectite clay has been formed by treating Na-montmorillonite with a hydroxy-aluminium solution with an OH/Al ratio of two. Heating the pillared clay for four h at 500°C reduces the interlayer spacing, measured at ambient humidity, from ∼ 9·4 to 8·0 Å. Hydrated VO2+ (and Mg2+) ions have been introduced into the region between the pillars by immersing the pillared clay in VOSO4-MgCl2 solutions and EPR measurements show that in general both immobile and mobile VO2+ ions are present. The immobile ion is probably VO2+(OH)x(H2O)5·x where x = 2–4, and is adsorbed on the pillars with a concentration that saturates at about 1 per 8 Al13 pillars in the unfired clay, and 1 per 4·3 pillars in the fired clay. The mobile species is VO2+(H2O)5 and for both fired and unfired clay in the wet state at room temperature it has a rotational correlation time of (9 ± 1) × 10−11s rad−1.

A detailed study of the mineralogy of the Jurassic detrital sediments of the Betic Cordillera (SE Spain) was needed to resolve problems relating to the environment of deposition. The choice of the marly limestone and marl facies for such a study was appropriate, because these are well represented throughout the Cordillera and consist of the earliest materials deposited after the break-down of the Liassic carbonate platform. Quantitative mineralogical analyses and crystallochemical studies enabled the source area to be defined, as well as indicating the likely erosion and weathering processes undergone by the minerals during transport and deposition, and the degree of diagenesis. Four mineral associations were distinguished, permitting a temporal and spatial analysis of the environment of deposition, and the relationship between its mineralogy and the different lithological facies.

L'analyse semi-quantitative, avec une microsonde électronique CAMEBAX, met en évidence des variations chimiques significatives dans des assemblages simples de minéraux argileux. La méthode est décrite et deux applications sont présentées et interprétées en termes de genèse et de paléoenvironnement. La microgéochimie d'illites et de chlorites du Crétacé inférieur (Marge du Maroc) évolue vers le haut de la série (diminution du magnésium) et semble influencée par une diagenèse salifère transformant des argiles détritiques. Des chlorites hypermagnésiennes apparaissent dans les sédiments les plus profonds, et autorisent l'hypothèse d'une authigenèse en milieu confiné. Les différentes smectites étudiées a la limite basalte-sédiment des sites 105 et 384 du DSDP (NW Atlantique) peuvent aisément être distinguées par leur microgéochimie avec Mg, Na, K, Al, Fe, Ti. Elles reflètent diverses sources volcaniques et leurs caractères sont très différents de ceux des smectites terrigènes communes.

An experimental pedology research project, based on a “process-system” pedogenetic model, was initiated to investigate the weathering of Phlegraean Yellow Tuff (PYT) – the yellow facies of the Campanian Ignimbrite with phillipsite > chabazite – as representative of the parent rock material as the soil-forming factor. PYT was weathered by water (W) and tannic acid solutions (TA) at concentrations ranging from 3 × 101 to 3 × 104 μmol l–1. The most concentrated TA solution (3 × 104 μmol l–1) showed the greatest extracting efficiency. Na and K were continually solubilized by W; Al, Ca and Mg contributed to the ionic composition of all the TA supernatants. A significant dissolution of the amorphous component and an associated decrease of the zeolite content, especially phillipsite, were noted. The features of PYT weathered outcomes fitted the “process-system” model very well. PYT showed a pedogenic potential, in being prone to weathering, as well as in releasing elements of importance for plant settlement and development, such as K, Ca, Mg and Fe.

Three clayey materials named MY3, KK and KG originating from the Foumban region (west Cameroon) were analysed to determine their granulometry, plasticity, major-element chemistry and mineralogy. Dilatometric and ceramic behaviour were also investigated. Clays were shaped by uniaxial pressing in a steel mould. Shaped samples were heated at 1300, 1400 and 1500°C. The end products were characterized in terms of their density, porosity and compressive strength. Raw materials differ in terms of their mineralogical composition, grain-size distribution, Al2O3 content and the nature and abundance of impurities inducing specific thermal behaviour during dilatometric analysis and sintering tests. The final material properties may be related to the main features of the raw materials used.

In order to improve the dispersibility of halloysite nanotubes (HNTs) in polytetrafluoroethylene (PTFE), the modification of HNT surfaces was studied with three types of modifiers (polymethyl methacrylate [PMMA], sodium dodecyl sulfate [SDS] and carboxylic acid). The modified HNTs were characterized by Fourier-transform infrared (FTIR) spectrometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and contact angle measurements. The HNTs were used to reinforce the mechanical properties of PTFE. The mechanical results indicated that the tensile strength of the modified HNT-filled PTFE nanocomposites (F-HNT/PTFE) improved to an acceptable degree and Young's modulus increased significantly. The tribological results showed that the wear rate of F-HNT/PTFE decreased by 21–82 and 9–40 times compared to pure PTFE and the pristine F-HNT/PTFE, respectively.

It has been previously reported that late diagenetic fibrous illite, separated out from oilfield sandstones for dating by the K-Ar method, has systematically shown an increasing K-content with burial depth in the UK northern and central North Sea. This is surprising as fibrous illite is believed to form rapidly, in response to a geological event such as oil charging, and to retain its composition during subsequent burial. If the composition of the illite is related to present-day conditions, rather than the conditions of initial formation, then argon loss may have occurred, making K-Ar ages of questionable validity. Variations in crystal chemistry of the illite and their fundamental particle size and shape (length/width) distribution suggest alteration of the illite from the time of formation. The extent to which K-Ar ages of illite might need to be re-interpreted as a result of this post-formation alteration is not quantifiable at present; however there is evidence to suggest that the ages may be interpreted in terms of burial models involving both crystal nucleation and growth, and that a high proportion of Ar within the crystals may be retained during post-growth recrystallization.

Amines are strongly adsorbed by the crystalline silica H4Si20O42·4H2O and are intercalated into the interlayer spaces. The adsorption of butyl-, hexyl-, octyl-, and decylamine from alcoholic solutions (ethanol, butanol…decanol) is competitive as both types of molecules, amines and alcohols, are adsorbed in the interlamellar space. The adsorption isotherms are presented as composite isotherms showing the specific reduced surface excess of amine, n°(n)/m, as a function of the molar fraction of amine in the equilibrium solution. These isotherms increase to a plateau-like section (n°(n)/m≈1·4 mmol/g) when the interlamellar adsorption is restricted to formation of monolayers of flat-lying molecules (in water, ethanol and butanol). In the presence of longer chain alcohols, the isotherms increase stepwise to a second "plateau" (at n1°(n)/m = 2·2-2·7 mmol/g) which corresponds to paraffin-type bilayers of amine and alcohol molecules. The composition of the adsorption phase is estimated from the specific reduced surface excess of amine on the basis of the interlamellar structure derived from basal spacing measurements.

The use of HF digestion to concentrate minerals of the plumbogummite group is discussed. Prolonged treatment is shown to result in solution of plumbogummite minerals, and in precipitation of HCl-insoluble, complex fluorides. These yield X-ray diffraction spacings that may be confused with those of plumbogummite minerals. The presence of fluorides in digestion residues is confirmed by X-ray diffraction, DTA and by identifying the products formed when such residues are heated to 600°C.

The inference of Gruner that unsatisfactory powder photographs of vermiculite resulted from distortion of the structural planes by grinding has not been substantiated. The unit cell parameters of a true vermiculite were found to be ao = 5·24± 0·02Å, bo = 9·17 ± 0·02Å, co = 28·60±0·05Å, β = 94° 36′ ± 24′, while the structural formula worked out as (Mg2·37, Fe3+0·37 X0·26) (Al1·28, Si2·72)O9 (OH)3·4H2O, where X represents the remaining octahedral cations. The determined density of the thin flakes was 2·28 g/cm3 and taking this value along with the volume of the unit cell (1370Å3) and the “molecular weight” calculated from the above formula, the number of formula units per unit cell worked out as Z=4·03. Some ‘vermiculite’ samples contain small groups of mica layers, but the non-basal mica reflections are not observable. The structures of these interstratifications and also of interstratifications containing chlorite are considered. Electron micrographs of vermiculite and the interstratified minerals are presented.

Stable isotopic and petrographic data have been used to interpret conditions for the formation of authigenic kaolinite within Lower Palaeocene sands, Central North Sea. Two wells within the Witch Ground Graben were sampled (1975 m to 2795 m). Texturally early calcite concretions have isotopic compositions (δ18O = 18.3–21.6‰ SMOW) which indicate that they were precipitated in predominantly meteoric waters. The isotopic composition of later vermiform kaolinite (δ18O = 14.8–17.7‰ SMOW and δD = −53 to −71‰ SMOW) indicates that kaolinite precipitated at around 45–70°C, from a mixed meteoric-marine pore-water (δ18O = −5 to −3‰ SMOW). These modelled precipitation temperatures are consistent with the paragenetic sequence and consequently post-precipitation hydrogen isotope exchange between kaolinite and the pore-waters is presumed not to have occurred. It is inferred that the original depositional marine pore-waters were flushed out during the late Palaeocene (54.8 Ma) by a head of meteoric water from the East Shetland Platform. The Lower Palaeocene aquifer became closed to meteoric influx after marine transgression during the late Palaeocene (54.0 Ma). The remaining meteoric pore-waters in the sandstones became mixed with water from compacting marine muds surrounding the hydrostatically pressured sandstones.

The different rates of smectite illitization have been investigated in interbedded sandstone and mudstone samples from the Neogene to Lower Pleistocene stratigraphy of the Niigata sedimentary basin. For samples of approximately the same age and under the same temperature and pressure conditions, the analytical results of XRD and EDS show that differences in the transformation from R = 1 I-S to R≥3 I-S at a temperature of ~30–40°C and 1000 m in depth are determined by the initial smectite composition and the relative ion concentration of pore-fluid in the sedimentary rock system. The ordered I-S and illite in the mudstone have inherited compositional characteristics from the initial detrital smectite and illite. In the sandstone, the I-S composition was changed by interaction with pore-fluids and by precipitation and crystal growth during diagenesis.