Diagenesis in the Cretaceous and Tertiary sediments of the Alava Block (Basque- Cantabrian basin) has been studied using the clay mineralogy (X-ray diffraction) of cuttings from three representative wells of a N—S cross-section. More than 5500 m of various lithologies (marls, mudstones and sandstones) have been drilled in the northern part of the domain, and 2100 m in the southern zone. The illitization of smectite and the disappearance of kaolinite, due to diagenesis, are the most characteristic features in the northern well. Evolution of smectite to illite has been differentiated into four zones, from top to bottom of the series, each showing specific I-S interstratified clay assemblages. The disappearance of smectite and the distribution of kaolinite in the other two wells are explained based on source-area considerations. Burial and thermal history have been reconstructed, revealing a northward increase in thermal flow until the Oligocene (Alpine orogeny paroxysm). In the northern well, the thermal model suggests temperatures of 160 and 270°C for the disappearance of smectite (R0) and illite-smectite (I-S) mixed-layer R1 clay minerals, respectively. The disappearance of kaolinite is related to a temperature of 230°C, a temperature never attained in the other two wells. Retardation of these processes, in relation to temperature values in the literature, is a consequence of the poor reactivity of marly lithologies, due to the low availability of cations. In this regard, the scarcity of reactants (K-bearing phases) and the absence of pathways (low permeability) for their access and circulation imply that illitization could have taken place in a closed system, by diffusion, on a very small scale, i.e. that of the original smectite grains.

In order to assess the influence of tetrahedral sheet charge on the hydroxyl-stretching vibration in clay minerals, a series of synthetic Na-saponites, with increasing layer charge, was studied by infrared (IR) spectroscopy. When recorded after KBr dilution either in transmission or diffuse reflectance, the IR spectra exhibit a component at ~3710 cm-1, the intensity of which increases linearly with increasing layer charge. When experiments are carried out without any dilution of the samples, this component is not observed, suggesting a Na+/K+ exchange upon mixing of the sample with KBr. The spectra obtained for K-saponite confirm this exchange. This shows that the dilution procedure can lead to serious misinterpretations of IR spectra in the OH-stretching region.

The Lembo clay deposit occurs on orthogneiss, but it also comprises clays with litho-relicts of volcanic rocks. In this study, ten samples from two sites were investigated. The mineralogical compositions consisted of kaolinite + halloysite + illite + quartz + hematite + anatase ± rutile ± orthoclase ± sanidine ± magnetite ± maghemite ± goethite ± Ba-Al-Fe-phosphates ± carbonates ± sulphates. Kaolinite-halloysite and quartz are the prevailing minerals. Some volcanicderived clays contain Fe-rich kaolinite-halloysite (9.6–14.1 wt.% Fe2O3). The chemical compositions, colours and specific surface area (SSA) measurements reveal two groups of clays: one with a positive whiteness index (IB), small SSA and small Fe content, and the other showing a large SSA, negative IB and relatively large Fe contents. The compositions of the first group are close to those of clays from the Mayouom deposit (Cameroon), and from some European commercial kaolins used in ceramics. Relatively Fe-rich clay materials may conform to most formulations of earthen bricks. As a whole, the Lembo clay deposit comprises various compositions of kaolinitic clays, which may yield the opportunity for extensive application in ceramics.

Low temperature nitrogen adsorption has been used to study the external and internal structure of a number of allophanic soil clays. The results indicate that allophane, in addition to having pores in the intermediate size range (2–10 nm radius), contains micropores of < 1 nm radius. The occurrence of hitherto unreported micropores in allophanic clays has necessitated re-evaluation of the validity of specific surface area measurements.

The sorption of ibuprofen by modified natural zeolite composites at three concentration levels (10, 20 and 30 mmol/100 g) of cationic surfactants – benzalkonium chloride and cetylpyridinium chloride, in a buffer solution (pH 7.4), was studied. Characterization of the composites before and after ibuprofen sorption was performed by drug sorption and isotherm studies, zeta potential and Fourier Transform infrared spectroscopic analysis. The biopharmaceutical performance of cationic surfactant-modified zeolites as drug formulation excipients was evaluated by in vitro dissolution experiments from the composites with medium surfactant contents. The drug sorption was influenced by the surfactant type and amount used for the zeolite modification. Prolonged drug release over a period of 8 h (up to ~40%) was achieved with both groups of samples. The kinetic analysis showed that the drug release profiles were best fitted with the Higuchi and the Bhaskar models, indicating a combination of drug diffusion and ion exchange as the predominant release mechanisms.

Water-saturated bentonite is planned to be used in many countries as an important barrier component in high-level nuclear waste (HLW) repositories. Knowledge about the microstructure of the bentonite and the distribution of water between interlayer (IL) and non-interlayer (non-IL) pores is important for modelling of long-term processes. In this work the microstructure of water-saturated samples prepared from MX-80 bentonite was studied with nuclear magnetic resonance (NMR) and small-angle X-ray scattering spectroscopy (SAXS) coupled with chloride exclusion modelling. The sample dry densities ranged between 0.7 and 1.6 g/cm3. The NMR technique was used to get information about the relative amounts of different water types. Water in smaller volume domains has a shorter relaxation time than that in larger domains due to the average closer proximity of the water to the paramagnetic Fe at the layer surfaces. The results were obtained using 1H NMR T1ρ relaxation time measurements with the short inter-pulse CPMG method. The interpretation of the NMR results was made by fitting a sum of discrete exponentials to the observed decay curves. The SAXS measurement on bentonite samples was used to get information about the size distribution of the IL distance of montmorillonite. The chloride porosity measurements and Donnan exclusion calculations were used together with the SAXS results to evaluate the bentonite microstructure. In the model, the montmorillonite layers were organized in stacks having IL water between the layers and non-IL water between the stacks. In the modelling, the number of layers in the stacks was used as fitting parameters which determined the IL and non-IL surface areas. The fitting parameters were adjusted so that the modelled chloride concentration was equal to the measured one. The NMR studies and SAXS studies coupled with the Cl porosity measurements provided very similar pictures of how the porewater is divided in two phases in bentonite.

On heating at temperatures below 600°C kaolinite reacts with salts of alkali metals according to the equation

2SiO2 · Al2O3 · 2H2O + 2nMX → 2SiO2 · Al2O3 · nM2O + 2nHX + (2−n)H2O

The reaction commences with the dehydroxylation of the clay and is favoured by high solubility of the salt and small size of the alkali ion.

It appears that on dehydroxylation the clay becomes reactive and, concurrently, the water liberated dissolves adjacent salt particles and catalyses the reaction.

Infrared spectra indicate that alkali ions are incorporated directly into the aluminosilicate structure, without the formation of metakaolinite as a detectable intermediate. The initial product is disordered, but as n approaches 1, crystalline phases tend to be formed.

Using X-ray techniques, the orientation distributions of crystal planes in laboratory prepared and naturally occurring aggregates were measured. A small specimen was mounted on the axis of a goniometer and the diffracted intensity measured as the specimen was rotated. Mo radiation was used to reduce the absorption effects. A mathematical relation between the distribution of particles and the distribution of crystal planes was derived for platy and fibrous particles in flake-like and rod-shaped specimens.

When diffracted intensities of the 001 reflection of several different kaolinites were corrected for the degree of orientation in the respective specimens, a constant value was obtained. This would enable quantitative diffraction analyses to be made without the large errors that can be introduced by orientation effects. The degree of particle orientation achieved appeared to be more dependent on particle morphology than on the method of sample preparation or formation.

The ability of montmorillonite to mitigate the toxic effect of heavy oil from the Nakhodka oil spill, by growth of hydrocarbon-degrading bacteria and enable bioremediation was studied. Montmorillonite enhanced the bacterial growth significantly (P < 0.05) in the main treatment containing heavy oil+bacteria+montmorillonite (OBM), because the specific growth rate (μ) was greater than that in the biotic control treatment containing heavy oil+bacteria (OB). Significant amounts of Si and Al (major constituents of montmorillonite) were not released in the aqueous phase over the ∽24-day experiment (P > 0.05). Transmission electron microscopic observation showed that the hydrocarbon-degrading bacterial cells were covered and encrusted with montmorillonite particles. Scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS) also showed that the surrounding of the bacterial cells was frequently rich in Si but not in Al. Fourier transform infrared (FTIR) spectroscopy indicated that the heavy oil-bacterial cell-montmorillonite particle complex retained the composition of both water and heavy oil. X-ray powder diffractrometery (XRD) analysis revealed that heavy oil and heavy oil-bacteria did not change the basal spacing of montmorillonite over a period of 24 days. The enhancement of hydrocarbon-degrading bacterial growth is attributed to montmorillonite likely serving as both bacterial growth-supporting carrier and protective outer layer against high concentrations of heavy oil that inhibit growth. These results shed light on the interactions in oil-bacteria-clay complexes and could potentially be used in marine oil spill bioremediation.

La majorité des termites sont en rapport avec le sol et utilisent l'argile de ses horizons, pour édiffer leurs termitières. Pour les termites du sol, dont la plupart sont des maçons, l'argile est avant tout le matériau de base offrant les propriétés de rétention d'eau, de plasticité et d'ahésivité, leur permettant de confectionner les mortiers et les microbétons de leurs unités de constructions. Si les termites humivores absorbent toujours une quantité relativement importante d'éléments argileux avec leurs aliments, les termites lignivores n'ingérent qu'occasionnellement une fraction minime d'argile. Leur action sur l'évolution des silicates se traduit par des néoformations de minéraux argileux au sein de leurs constructions: illite ‘artificielle’, hydrobiotite, vermiculite, halloysite, montmorillonite, et parfoils sépiolite et attapulgite. Ces néoformations résultent de l'action conjugée du travail de broyage et de trituration salivaire de minéraux encore peu altérés de la profondeur du sol, et des conditions physico-chimiques de milieu particulières aux termites.

Wyoming bentonite, exchanged with cations of high charge density, is an efficient and selective catalyst for the production of ethyl acetate, in a single step, from ethylene and acetic acid. The reaction occurs in the interlamellar space of the clay where it is proposed that strong Brönsted acid sites on the clay coupled with highly polarized intercalated reactants produce a reaction which is otherwise difficult to carry out.

Halloysite clay nanotubes are safe and biocompatible nanomaterials and their application in biomaterials is very promising. The microencapsulation of yeast cells in the shell of clay nanotubes modifying their properties was demonstrated here. Each cell was coated with a 200–300 nm-thick tube shell and this coating was not harmful for these cells’ reproduction. Synthesis of magnetic nanoparticles on the surfaces of the nanotubes allowed for magnetic-field manipulation of the coated cells, including their separation. Providing nano-designed shells for biological cells is a step forward in development of ‘cyborg’ microorganisms combining their intrinsic properties with functions added through nano-engineering.

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been used to determine the nature of acid sites present in Na+-, Ni2+- and Al3+-exchanged montmorillonite using the diagnostic base, pyridine. The pyridine additions were performed in situ at 25°C in the presence of liquid benzene or deuterated 1,4-dioxan to ascertain whether the acidity profile was influenced by the presence of either the non-polar or oxygenated solvent. Pyridine treated Ni2+-montmorillonite exhibited absorption bands characteristic of Lewis bound base in both benzene and deuterated 1,4-dioxan indicating that the Lewis acid sites were present at low temperature and were accessible in both solvents. The presence of a strong 1537 cm−1 band in pyridine-saturated Al3+-montmorillonite confirmed that this clay acted as a Brønsted acid in benzene. However, this diagnostic band was significantly reduced in the presence of deuterated 1,4-dioxan.

Volcaniclastics have not as yet been considered prime hydrocarbon exploration targets. This is because they contain a high proportion of mechanically and mineralogically unstable components which generally cause a faster deterioration in reservoir quality upon burial than is found in siliciclastics. Also, their complex mineralogical composition makes the burial-related diagenesis more difficult to understand. However, under favourable circumstances—such as devitrification at shallow depth, leaching of unstable particles, fracturing, or reworking—volcaniclastics may act as good reservoir rocks. Both favourable and unfavourable case histories are discussed.

The specific surface areas of three montmorillonite samples, both alone and in admixture with kaolinite, have been measured. The results are discussed in relation to the possible existence of montmorillonite crystals.

The effect of heating, to temperatures between 400 and 1200ºC, on the dehydroxylation of kaolin and the pozzolanic activity of the resulting amorphous material were determined by a variety of analytical techniques. Mixtures of concrete containing variable amounts of kaolin calcined at 700ºC were analysed and the results compared with those for concrete samples containing two different types of imported metakaolin. As shown in this work, Colombian kaolin can be used effectively as a raw material to obtain a highly active product (metakaolin). The optimum heating temperature for the kaolin is between 700 and 800ºC.

The transition between very low-grade and low-grade metamorphism has been studied in the Urbión and Enciso Groups of the Late Jurassic-Early Cretaceous Cameros basin (NE Spain). The ‘illite crystallinity’ (IC) values do not appear to be controlled by burial depth but rather by: (1) XRD overlap with other phases (e.g. paragonite and mixed-layered muscovite-paragonite) in the siliciclastic samples; (2) the presence of carbonates, which delay illitization, resulting in an increase in the IC values, that becomes more pronounced as the P-T conditions decrease towards the diagenesis zone; and (3) the permeability of the sediments, which controls the circulation of metamorphic fluids and therefore the distribution of ‘crystallinities’ and mineral assemblages within the basin.

The anchizone is represented by a narrow range of ‘chlorite crystallinity’ (ChC) values. Therefore, ChC is a less sensitive parameter than IC for estimating changes from diagenetic to low-grade metamorphic conditions. However, ChC can be a useful tool when there is a great heterogeneity of facies types, as it is not affected by the presence of carbonates.

Two-layered Fe(III)-M(II) hydroxy carbonates (M(II) = Ni or Mg) have been synthesized by induced hydrolysis using controlled air oxidation of an aqueous Fe(II)-M(II) mixture (M(II)/Fe(II) ratio >3) at a pH below which the hydroxide of the M(II) cation precipitates. The crystalline, homogeneous product can be a single phase consisting of very thin circular to hexagonal plates (0·2–0·8 µm diam.). For synthetic reevesite (Ni(II)-Fe(III) hydroxy carbonate), stable spherular aggregates are formed. The well crystallized products have an M(II)/Fe(III) ratio of about two. However, by varying the pH, the initial M(II)-Fe(III) ratio and the oxidation rate, the M(II)/Fe(III) ratio in the product and its crystallinity can be varied. The derived formulae are in reasonable agreement with the known composition of pyroaurite-type compounds. Possible synthesis pathways are discussed. The ability to control some physical and morphological features of the products indicates that the synthesis technique could prove advantageous in the preparation of certain catalyst precursors.

The adsorption and desorption of Hg(II) by humic acid (HA) previously adsorbed on kaolin was studied. In the range of HA concentration investigated (0.0 –26.9 mg g–1), the Hg(II) adsorption capacity of kaolin at pH 4 is enhanced by the presence of HA. For the complexes with the highest HA concentration and for low Hg(II) initial concentrations, adsorption was lower, i.e. as HA concentration on the complexes increases, Hg(II) equilibrium concentration also increases. This behaviour is due to the increasing presence of dissolved organic matter as the HA concentration on the complexes increases. The dissolved organic matter is able to form a soluble complex with Hg, thus decreasing adsorption. Hg(II) adsorption from a 2.5×10–5 MHg(II) solution was influenced by pH. For kaolin, a pHmax (pH where maximum adsorption occurs) of 4.5 was observed. At pH values >pHmax retention decreased with increasing pH. This same behaviour was observed for the kaolin- HA complex containing the lowest HA concentration (6.6 mg g –1). For the other kaolin-HA complexes there was little effect of pH on Hg(II) adsorption between pH 2.5 and pH 6.5. The presence of HA increased the adsorption of Hg(II) on kaolin all along the pH range studied. Desorption experiments showed that the amount of Hg(II) desorbed was quite low (<1%) for all the HA and Hg(II) concentration range studied, except for the kaolin at acid pH (pH 2.5) where the Hg(II) released was >50% of Hg(II) previously adsorbed. The presence of HA dramatically reduced this percentage of desorption to values of <3%, indicating reduced risk of toxicity problems in surface and subsurface waters. The addition of Cu(II) did not favour any Hg(II) desorption, even though Cu exhibits a strong affinity for organic matter.