A Tertiary mudstone from beneath worked coal among the basalts of the Faeroe Islands is mainly composed of aluminium-rich dioctahedral smectite, disordered kaolinite (amounting to about one quarter of the smectite) and probably about 13 ~ amorphous material. The texture is the result of crystallization in place. Chemical analysis suggests an ionic formula for the smectite of (Ca0.32Na0.10K0.04) (A13.88 Fe0.06+3Fe0.05+2Mg0.29) (Si6.71 A11.29) O20 (OH)4· 3·0 H20, which corresponds closely to beidellite. The total charge on the interlayer cations is 0·78 and cationexchange capacity is 52·5 meq/100g. DTA curves yielded endothermic peaks at 140°C, 220°C, and 555°C with an exothermic peak at 955°C. The nomenclature is discussed and the material considered to be a bentonitic beidellite-mudstone; the rock, which has crystallized in place has similarities with tonstein in its mode of formation.

The evolution of textural properties of Na/Ca-bentonite from Wyoming (MX-80) was studied by adsorption of nitrogen, water vapour, and ethylene glycol monoethyl ether. Clay suspensions were heated at 80 and 300ºC for up to 9 months in the absence of or in the presence of Fe and/or Fe oxides. The treatment without Fe did not change the textural properties of the samples significantly. The treatment at 80ºC in the presence of Fe resulted in a considerable increase in the external surface areas of the samples. The total and external surface areas and swelling capacities of the samples decreased following the treatment at 300ºC in the presence of Fe and Fe oxides. In the case of larger additions of Fe, the treatment at 300ºC resulted in a considerable decrease in the total and external surface areas and swelling capacity of the sample and in the formation of a network of large-size pores, in which all the pores were connected.

The adsorption mechanisms of hazardous gas molecules such as NH3, H2S and SO2 on sepiolite have not yet been elucidated. Therefore, molecular dynamics (MD) simulations were employed to investigate the adsorption behaviour of sepiolite towards NH3, H2S and SO2. A calculation model for sepiolite containing structural and zeolitic water molecules was constructed in this study. The adsorption sites and molecular configurations of the hazardous gases in the sepiolite channels were studied. The radial distribution function was employed to evaluate the interactions between the gas molecules and sepiolite. The results show that the order of adsorption capacity of sepiolite for the gases is as follows: SO2 > H2S > NH3. These three types of gas molecules absorbed in the channel nanopores of sepiolite exhibit different atomic configurations. The diffusion coefficients of the gas molecules in the channels decreased in the following order: NH3 > H2S > SO2. In addition, the diffusion coefficients were affected significantly by the ratio of the number of gas/water molecules. This study provides new perspectives for understanding the molecular processes responsible for the adsorption properties of sepiolite.

Bentonite is one of the more safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. It is used due to its favourable properties (including plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides) and its stability in relevant geological environments. However, bentonite is unstable under alkaline conditions and this has driven interest in low-alkali cements (leachate pH of 10–11). To build a robust safety case, it is important to have supporting natural analogue data to confirm understanding of the likely long-term performance of bentonite. In Cyprus, the presence of natural bentonite in close proximity to natural alkaline groundwaters permits the zones of potential bentonite/alkaline water reaction to be studied as an analogy of the potential reaction zones in the repository. Here, the results indicate minimal volumetric reaction of bentonite, with production of a palygorskite secondary phase.

A 2–20 µ fraction of phlogopite has been converted to the sodium form by use of sodium tetraphenylboron-NaCl solutions. The cation exchange capacity of the treated material increases to a maximum of about 212 m-eq/100 g, which agrees well with the K2O + Na2O content of the initial mineral. Li-, Na-, Ca-, and Mg-saturated forms have been prepared and examined by X-ray diffraction and by thernogravimetric measurements in air, in vacuo, and at progressively elevated temperatures. Hydration states corresponding to double water layers are observed for the Mg- and Ca- forms, and to single water layers for the Mg-, Ca-, Na-, and Li- forms. The numbers of water molecules per unit cell and per interlayer cation are considered for the various hydration states.

Suspensions of thirty six bentonites were equilibrated for 24 h and then adjusted to pH 3. After an hour, pH titrations up to pH 12 at varying ionic strengths were performed within 4.5 h. The titration data were recalculated into proton affinity distributions (PAD) using the condensed approximation. In spite of widely varying chemical compositions, all bentonites showed a protonation reaction between pK 4 and 5, which could be assigned to aluminol groups at the edge surfaces of the smectites. The average pK is 4.73±80.31. A second prominent peak in the PAD at pK = 10.43±80.13 could be assigned to exchangeable Mg2+ in the interlayer space. The possibility to constrain both pK values at a fixed average value will decrease the number of parameters in surface complexation modelling and thus enhance its convergence.

The smectite-bearing red bed series of the Palaeogene Ergeliin zoo Formation in Mongolia is part of an alluvial-fluvial fan prograding over prodelta/mudflat deposits. The series was investigated in the field (mapping and portable infrared (IR) spectrometry in the short wavelength (SW) range) and samples were analysed in the laboratory using thin sections, X-ray diffraction, X-ray fluorescence, cation exchange capacity and Fourier transform infrared spectrometry in the mid-IR range. Two reference sections are treated in more detail as to the environment of deposition and concentration of smectite. The deposits at Ulaan uul are representative of a distal fan section with prevalent mudflats, whereas Ulaan buur offers insight into a braided river drainage system. Metabasic rocks in the hinterland delivered mica and chlorite from which smectite originated during diagenesis under semi-arid climatic and surface-near conditions. Towards the basin edge, smectite is replaced by kaolinite. The prime area in which we were interested in the smectite is the most distal part of the alluvial-fluvial fan, which was the subject of a field-based IR survey. This exploration method is a valuable tool to obtain a quick overview of the mineral composition and reduce the number of samples in the field for follow-up analyses. Its weak and strong points are discussed.

The distribution of clay minerals in recent sediments on the continental shelf and in the Bay of Cádiz has been analysed as part of a wider study of sedimentary exchange between the continent and the continental margin. The clay minerals included in the muddy sediments consist mainly of illite, kaolinite, smectite, randomly mixed-layered illite-smectite, chlorite, vermiculite and randomly mixed-layered illite-chlorite. Distribution of the minerals indicates that inheritance from the adjacent continental areas is the most important process involved.

The relations between the clay minerals were established by Q-mode and R-mode factor analysis. The main clay mineral associations are: (1) illite-kaolinite, (2) smectite-random mixed-layered illitesmectite, and (3) kaolinite-random mixed-layered illite-smectite-vermiculite. The main sources of sediment supply to the continental shelf are the Guadalquivir and Guadiana rivers. Sediment from these rivers and from the rivers flowing into the Bay of Cádiz (mainly the Guadalete) is transported to the part of the shelf outside the bay by ebb-tide currents. The path of this outflow to the continental shelf, where the sediment is partially deposited, is influenced by the morphology of the coast and by hydrodynamic processes.

Geotechnical properties and behaviour are described of the very wet, halloysitic, residual clay found in the dense rain forest at Monasavu, Viti Levu, Fiji, where the annual rainfall can exceed 5 m. The tropical climatic conditions have caused deep weathering of sandstones and produced a highly plastic clay with low density and a natural moisture content greatly in excess of the standard compaction optimum. This clay was found to contain halloysite which was ‘amorphous’ rather than crystalline. The material was used in this natural state in an 85-m high rockfill dam at Monasavu Falls as an unusually soft core, the construction of which involved unconventionally light compaction by low-ground-pressure-tracked dozers. Its resulting behaviour in terms of three-dimensional total and effective stresses, stress paths and deformations throughout the construction, impounding and full reservoir stages was closely monitored. This behaviour is examined in the light of the clay's classification, mineralogical, compaction and engineering properties determined before and during construction. Despite its unusual properties, it is concluded that the clay is a good engineering material, behaving like others containing halloysite in the more common tubular form, and, moreover, that the high natural moisture content is of positive benefit.

Se ha estudiado la interacción de fosdrín (pesticida organofosforado) con montmorillonita mediante difracción de rayos X y espectroscopia infrarroja. Este insecticida forma con montmorillonita dos tipos de complejos, con espaciados basales 16·05 y 20·06 Å. La formación de uno u otro tipo depende del estado de hidratación y del catión interlaminar de las muestras, de la naturaleza del disolvente y de la concentración de fosdrín. En los espectros de infrarrojo de los complejos, las vibraciones de valencia P =O y C =O del fosdrín se desplazan hacia frecuencias más bajas. La magnitud del desplazamiento de estas vibraciones es función del poder polarizante del catión interlaminar. El desplazamiento de la vibración de valencia C =O depende además del tipo de complejo y de su grado de hidratación. La vibración de valencia C=C se desplaza hacia frecuencias altas en los complejos de espaciado basal 16·05 Å. Los resultados obtenidos indican que el complejo de 16·05 Å es monocapa y que las moléculas de fosdrín (forma trans) deben interaccionar con los cationes interlaminares a través de ambos grupos P =O y C =O. El complejo de 20·06 Å es de dos capas y las moléculas (forma cis) interaccionan solamente a través del grupo P =O.

The interaction between phenyl salicylate and sepiolite has been studied using drugclay systems obtained by melting and grinding. The samples have been characterized by powder Xray diffraction, differential thermal and thermogravimetric analyses, and Vis-UV and FT-IR spectroscopies. ‘Free’ water molecules are steadily substituted by the drug molecules, without any chemical change as shown by FT-IR. The systems prepared improved the protecting ability of the pure sepiolite or the pure drug against ultraviolet radiation, especially in the so-called ‘C’ range (290-190 nm).

It is argued that a wide range of engineering data and geological data is required to make confident prognoses or diagnoses of formation damage. Potential sources of data are reviewed, with comments on their limitations. It is proposed that microscopic failure can cause formation damage in macroscopically intact rock at stress concentrations around the wellbore. The significance of natural fractures is reviewed in relation to formation damage induced by diagenetic mineralization or invasion by lost circulation material. Removal of such plugging material by acid stimulation is assessed in relation to diverting agent requirements.

This study focuses on the mineralogical characterization of four raw clay samples from Dobrodo deposit, Serbia. Several analytical methods were applied to determine the chemical and mineralogical composition, morphology and physical properties (colour, plasticity, specific surface area, particle size and cation-exchange capacity) of the clay samples. Kaolinite, smectite and illite are the predominant phases in all of the samples studied that contain between 60.2 and 87.1 wt.% of clay. Quartz, feldspars, paragonite and Ti- and Fe-bearing phases were also identified. The relatively high SiO2/Al2O3 mass ratio indicates abundant quartz. The cation-exchange capacity of the samples varied between low and moderately charged clay minerals (12–52 mmol 100 g–1) with specific surface area values ranging from 94 to 410 m2 g–1. The plasticity index values (11–23%) suggest low to moderate plasticity. Preliminary results show that most of the raw clay from Dobrodo deposit might be suitable for use in ceramic applications.

This study investigated the potential of halloysite nanotubes (HNTs) to improve the sustained release properties of chitosan (CS) microparticles cross-linked ionically with tripolyphosphate (TPP). Composite CS-HNTs microparticles were obtained by a simple and eco-friendly procedure based on a coaxial extrusion technique. Prior to encapsulation, a water-soluble model drug, verapamil hydrochloride (VH), was adsorbed successfully on HNTs. The microparticles were characterized by optical microscopy, Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis/ thermogravimetric analysis (DTA/TG) and evaluated for encapsulation efficiency and drug-release properties. The composite particles had a slightly deformed spherical shape and micrometric size with average perimeters ranging from 485.4 ± 13.3 to 492.4 ± 11.9 μm. The results of FTIR spectroscopy confirmed non-covalent interactions between CS and HNTs within composite particle structures. The DTA and TG studies revealed increased thermal stability of the composite particles in comparison to the CS-TPP particles. Drug adsorption on HNTs prior to encapsulation led to an increase in encapsulation efficiency from 19.6 ± 2.9 to 84.3 ± 1.9%. In contrast to the rapid release of encapsulated model drug from CS-TPP microparticles, the composite CS-HNTs microparticles released drug in a sustained manner, showing the best fit to the Bhaskar model. The results presented here imply that HNTs could be used to improve morphology, encapsulation efficiency and sustained drug-release properties of CS microparticles cross-linked ionically with TPP.

In the northernmost Calchaquí Valley (Salta, Argentina), the Paleogene continental sediments show a transition from smectite, at the top, to R3 I-S (>90% illite) through R1 I-S (65–80% illite), in contrast to the remaining sectors, containing smectite up to the bottom. Samples at the base of the succession were characterized by high-quality step-scan X-ray diffraction (XRD), scanning electron microscopy (SEM) and analytical high-resolution transmission electron microscopy (HRTEM). Analysis by SEM demonstrated dissolution of primary phases (feldspars, micas and quartz) and crystallization of illite, I-S and kaolinite. As this alteration is not pervasive, an intermediate fluid/rock ratio could be inferred. The lattice-fringe images of the samples from upper parts of the sequence show abundant I1-rich areas, whereas in the lower parts of the sequence, illite packets and I3 I-S coexist and compositions evolve towards muscovite (tetrahedral-charge increase, principally compensated by Mgby- Al substitution in octahedral sites and by a slight decrease in Ca in interlayer sites). As burial temperatures were probably similar in all the samples, depth was not responsible for the illite formation at the bottom. The TEM textures suggest that illitization proceeded mainly by dissolution-crystallization. The active faults close to the northern Calchaquí Valley probably promoted the circulation of hot, deep fluids, favouring illitization.

Many safety functions required of the compacted bentonite buffer in the KBS-3 concept rely on processes influenced by the composition of the pore water. Important safety-relevant processes are related to the bentonite buffer, e.g. swelling, precipitation and dissolution reactions, and transport of water, colloids and ions. One of the methods used in analysing pore water in compacted bentonite is the ‘squeezing technique’. Various possible artefacts which can occur during squeezing, such as mixing of different pore-water types, dissolution of accessory minerals and cation exchange, need special attention.

The present work describes the methodology for studying the composition of the non-interlamellar pore water by combining squeezing methods, chemical analyses, microstructure measurements and geochemical modelling. Four different maximum pressures were used to squeeze the compacted bentonite pore water. The origin of the pore water was studied by analysing the bentonite microstructure both before and after squeezing using SAXS and NMR, the cation exchange and dissolution reactions were studied by chemical analyses and geochemical modelling.

The pore-water yield increased from 32 to 48 wt.% from the initial amount of porewater in the samples when the maximum squeezing pressure was increased from 60 MPa to 120 MPa. About 35 wt.% of the water collected originated from the interlamellar (IL) pores. The ratio between IL and non-IL pore waters as well as the composition of the squeezed porewater was constant in the squeezing-pressure range used. The results of microstructural measurements by SAXS were in perfect agreement with previous studies (e.g. Muurinen & Carlsson, 2013). The dissolving accessory minerals have an effect on the ratio of the cations in the squeezed solution while the migration of anions in bentonite seems to be diffusion limited. According to geochemical modelling the chloride concentration of the non-IL pore water in compacted bentonite before squeezing was 0.34 Mgreater than in the squeezed pore water due to the mixing of two main water types.

The mineralogy of the fine clay fraction (<0·2 μm) of two soil pedons (Aquic and Udic Haplustalfs) representing the wheat-sugarcane belt of the Indo-Gangetic alluvial plain was studied by X-ray diffraction, differential thermal analysis, transmission electron microscopy, and by chemical analysis. The XRD patterns are characterized by unusually high spacings which are interpreted in terms of an interstratification comprising smectite, illite and ‘chlorite’ components. The CEC data (Ca/Mg and K/NH4) also indicate the possible presence of vermiculite. A plateau bridging the 7–10 Å maxima in K-saturated specimens heated at 300°C suggests interstratification of kaolinite and smectite, although this may not be part of the above interstratification. The diffuse bands shown by Mg-glycerol-solvated Ap-horizon clays at ∼21 Å, and the increasing elimination of XRD peaks in the > 10 Å region with distance from the surface, suggests that the expanding layers have a slight tendency to segregate in Ap horizon samples and that randomization tends to increase with depth. Discrete illite and small amounts of kaolinite were also detected.

Varty & White's application of multivariate analysis to Grim & Kulbicki's measurements on montmorillonites has been re-examined and extended. Inconsistencies between their table of scored data and derived similarity table, and some unexplained errors in the similarity table, have only a small effect on their results. Similarities calculated from Grim & Kulbicki's data, using a different similarity coefficient, lead to a two dimensional representation which separates the groups of montmorillonites more clearly. The groups can be clearly separated even in a one dimensional representation, by changing the relationship between distance and similarity.