The ability to produce humic-like polymeric compounds, with D-glucose and L-tyrosine as starting materials, was evaluated in different mineral systems: (1) Ca-, Al- and Cu(II)-saturated montmorillonite; (2) Ca-, Al- and Cu(II)-saturated kaolinite; (3) quartz in the presence of two different amounts of the same cations (according to the cation exchange capacity of the clays); and (4) untreated quartz (as control). All systems proved to be effective in the formation of humic-like compounds, particularly quartz, in the presence of cations. The effectiveness in promoting humification reactions was strictly related to the amounts of added cations. In the reaction conditions considered, the humification appears to be due more to the cations than to the type of clay minerals. The clayey systems synthesized more complex (aromatic) substances than the quartz ones.

Anaerobic bacteria were identified in live drilling muds and cores from nine different North Sea and Irish Basin oilfields, varying in depth from 3500 to 15000 ft, and at temperatures up to 150°C. The anaerobic bacteria may be introduced into the reservoir during drilling operations or injection of water, but in many cases the bacteria are indigenous to the oilfield reservoirs. Confirmation of the indigenous anaerobic bacteria was made using molecular biology techniques (16S rDNA sequence analysis), comparing microbial populations present in the blank drilling mud as supplied to wellsite, in the live drilling mud taken during coring, and in the live core. The role of anaerobic bacteria in oilfield diagenesis is not fully understood, though pyrite precipitation, and exopolymer and H2S gas production were noted in this study, up to temperatures of 95°C.

A mineralogical and microstructural study of bentonites from 'Cerro del Aguila' located in the Tagus Basin (Toledo, Spain) was carried out using XRD, SEM and TEM observations and chemical data obtained by TEM-EDX. The bentonites are mainly composed of trioctahedral smectite with a unit-cell formula (Si3.76Al0.24)(Al0.44Fe3+0.26Mg1.81)Ca0.05K0.19O10(OH)2 and small amounts of illite. The relationships between illite and smectite particles observed by SEM and TEM allowed the study of the weathering process of illite to form smectite through possible intermediate stages. The transformation begins as an exfoliation normal to the stacking direction and develops by opening of the interlayer spacing, the replacement of K+ by hydrated interlayer cations and slight reorganization of the 2:1 layer structure. The so-called solid-state transformation process then proceeds by further dissolution and the formation of a colloidal phase acting as raw material in the growth of new phyllosilicates such as smectite.

The numerous kaolin deposits located in Patagonia, Argentina, have been formed by hypogene or supergene processes. The primary origin has been established from O18 and D isotopic composition of the main minerals, kaolinite and/or dickite, and from the behaviour of certain elements during the alteration. The aim of this paper was to find if there is a tool, other than oxygen-deuterium data, to establish the origin of the Patagonian kaolin deposits. To handle the large number of variables per sample, a statistical multivariate study was used. The Principal Component method defines, on one hand the variables that better characterize each deposit and, on the other hand, the correlation between them. Fifty seven elements were considered and those that were not explained using these two components (which represent 75% of the total variance of the model) were discarded. As a result, the contents of Fe2O3, P2O5, LOI, Sr, Y, Zr, V, Pb, Hf, Rb, S and REE were used and the results show that the two components separate the deposits into two fields that are consistent with the process of formation. The first component indicates that Fe2O3, Y, Rb, U and HREE are more abundant in the supergene deposits, whereas, Sr, Pb, S and V are more abundant in the hypogene deposits. The second component shows that S, P2O5 and the LREE are enriched in the hydrothermal deposits, whereas Zr is more abundant in those formed under weathering conditions.

A method of infrared (IR) analysis for quantitative determination of tubular halloysite in mixtures with kaolinite was investigated for drill hole samples collected during an assessment of paper-coating kaolin resources at the Mount Hope Kaolin Deposit, Eyre Peninsula, South Australia. Tubular, dehydrated halloysite from the deposit does not readily intercalate formamide, and the proportion of tubes in <2 μm size-fractions was determined initially from scanning electron micrographs. For samples showing a range of tube contents, a strong correlation between IR spectral response and counts of halloysite tubes was established using partial leastsquares analysis. This provided a rapid technique suitable for routine determination of tubular halloysite in samples from the Mount Hope deposit. Although the universality of the method remains to be tested, it offers an alternative approach to other analytical techniques for assessment of kaolin deposits where the presence of halloysite is suspected.

A layered composite of Fe2O3-pillared bentonite (Fe-P-Bet), used as a catalyst in a Fenton-like process, was prepared and then its mechanical activation was studied in detail. The optimum conditions for preparation of Fe-P-Bet and the effects of mechanical activation on the catalytic activity of Fe-P-Bet were investigated systematically. The impact of the mechanical activation on the catalytic activity was affected by the filling ratio of the grinding medium, by the combination of different sized milling balls, by the rotation speed of the planet carrier, by the milling time and by the powder-to-ball ratio. Compared with the removal ratio of orange II of 14.5%, catalysed by Fe-P-Bet, the removal ratio catalysed by activated Fe2O3-pillared bentonite (A-Fe-P-Bet) was as high as 93.6%, and A-Fe-P-Bet had the merit of good stability and only a small amount of Fe leaching during the Fenton-like process. The catalysts prepared were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and by the BET method; A-Fe-P-Bet has a small particle size and a rough surface. The lattice distortion and decrease in the crystal size of α-Fe2O3, as well as damage to the layer structure of smectite in the bentonite, were the main reasons for the increase in the catalytic activity of A-Fe-P-Bet. The results indicated that mechanical activation was an easy and effective method for improving the catalytic activity of this bentonite-based layered composite and that A-Fe-P-Bet was a safe, ‘green’, catalyst material for use in Fenton-like oxidation during treatment of wastewater.

Comme la plupart des vermiculites, l'hydrate à une couche de la vermiculite-Na (d001 = 11·85 Å) présente une structure semi-ordonnée, avec des défauts d'empilement (glissements selon l'axe b). Le plan (h0l)* du réseau réciproque est entièrement discret, tandis que les rangées n'appartenant pas à ce plan sont plus ou moins diffuses dans la direction c*. La projection x0z est obtenue par une classique analyse de Fourier bidimensionelle. Dans les plans (0kl)* et (1kl)*, certaines rangées semblent presque discrètes: ceci permet d'essayer de déterminer la translation selon l'axe 0y entre deux feuillets adjacents. Le calcul des intensités des diffusions le long des rangées des plans (0kl)* et (1kl)* conduit à ne retenir qu'un seul modèle. Le désordre résulte d'une distribution aléatoire de trois translations parallèles à l'axe Oy: l'une est nulle et les deux autres sont de +0·307b et −0·307b. Le principal intérêt de ce travail est de présenter une nouvelle méthode d'approche pour l'étude des structures semi-ordonnées.

Highly weathered soils of the tropics and subtropics commonly have kaolinitedominated clay fractions. Under acidic conditions prevailing in these soils kaolinite dissolution occurs, contributing to the high levels of soluble Al in these soils. This study evaluates the dissolution behaviour of kaolinites from subsurface horizons of highly weathered soils from Thailand, along with a soil kaolinite from Western Australia (WA kaolinite) and Georgia kaolinite (KGa-2). Kaolinite-dominated clay fractions were isolated from soils by sedimentation and chemically treated to remove iron oxides. The dissolution rate of kaolinites was measured in 0.01 M NaCl as a function of pH (1–4; HCl) at 25±1°C using non-stirred flow-through reactors. Kaolinite dissolution rates were calculated from the release of Al and Si at the steady state. In most of the experiments and at all pH values, the release of both Si and Al underwent a distinct transition from an initial period of rapid release to significantly slower release at the steady state. Aluminium and Si concentrations at the steady state were higher for soil kaolinites than the reference sample (KGa-2). At the steady state the dissolution of all kaolinites was stoichiometric except for the soil kaolinites from Thailand at pH 4, where the Al/Si ratio was well below the stoichiometric ratio. Log dissolution rate (RSi) of soil kaolinites ranged from –13.75 to –12.51, with the dissolution rate increasing significantly with decreasing solution pH. However, the dissolution rate was similar or pH independent between pH 2 and 3, which is the pH range of the point of zero net charge (PZNC) for both soil and reference kaolinites. The dissolution rate of soil kaolinite was significantly higher than the KGa-2 sample at pH < 3. The results obtained on kaolinite samples from highly weathered soils show that in highly acidic systems kaolinite is a source of soluble Al. Soil kaolinites with poorly ordered small crystals dissolve faster than better crystalline reference kaolinite (KGa-2) with larger crystals.

Rhyolitic obsidian was reacted with natural waters to study the effect of water chemistry and biological activity on the composition and formation mechanisms of clay. Two sets of experiments (18 months, 6 years) used fresh, hypersaline water (Mg-Na-SO4-Cl- and NaCl-rich) and seawater. The 6-year experiments produced the transformation of obsidian into quartz, apparently by in situ re-crystallization (Cuadros et al., 2012). The most abundant neoformed clay was dioctahedral (typically montmorillonite), indicating chemical control by the glass (where Al > Mg). Altered glass morphology and chemistry in the 18-months experiments indicated in situ transformation to clay. Magnesium-rich (saponite) clay formed under water-chemistry control in the bulk and within biofilms with elevated Mg concentration (Cuadros et al., 2013). The contact between microbial structures and glass was very intimate. Glass transformation into quartz may be due to some characteristic of the obsidian and/or alteration conditions. Such combination needs not to be uncommon in nature and opens new possibilities of quartz origin.

In this study, the reaction between humus acids (humic acid and β-humus fulvic acid fraction) and bentonite and illite was studied at a variety of pH values. The degree of reaction was determined from the specific surface area and molar energy of adsorption. Characteristic parameters of adsorption isotherms for the formation of a mono-layer of the adsorbent, such as the constant C from the BET equation, mono-layer capacity (Nm), and standard error square (R2), were also included in the study. After the addition of humus acids, the specific surface area of illite and bentonite decreased at all pH values, reaching a minimum at pH 4. This indicates different degrees of reaction of humus acids with the clays and, probably, partial hydrophobization of the materials. The degree of reaction of humus acids with the minerals depended on the pH and, for certain combinations, it was highest at pH 4. This value is relatively close to that at which the humus acid fractions in question precipitate from solution.

Four methods of extracting clays from calcite-rich samples were compared: (i) sodium acetate buffer solution; (ii) lithium acetate buffer solution; (iii) hydrochloric acid; (iv) liquid cation-exchange acid. The methods were tested on mixtures consisting of 80% calcite, 10% quartz and 10% hectorite. Potassium had previously been exchanged on to the interlayer sites of the clay. XRD traces of the extracted clays appeared identical with those of the original clays except for a sharpening of the 001 reflection. The bulk chemistry of the clay was unchanged except by the HCl extraction, which appeared to cause a stripping of the octahedral cations. With all of the methods the exchangeable cation content was altered; the sodium acetate method, for example, retained only 17% of the original exchangeable K+, the other methods all retaining <10%.

The ability to produce humic-like polymeric compounds, with L-tyrosine as the starting material, was evaluated using different mineral systems, e.g. on Ca-, A1- and Cu(II)-saturated montmorillonite, nontronite and kaolinite, and on quartz. Clay minerals proved to be effective in the formation of these compounds, but not quartz, except in the presence of Cu(II). The newly formed compounds were fractionated by alkaline extraction. With clay systems, the amounts of substances produced appear to be related more to the interlayer cation than to the clay type. Copper cations appear to be more effective when not associated with the clay structure.

X-ray diffraction and electron microscopy show that halloysite occurs widely in soils derived from a variety of parent rocks (granite, gabbro, schist and slate) in north-east Scotland. Both tubular and non-tubular forms are observed, the latter being characterized by electron diffraction patterns with 001 reflection either absent or very weak and diffuse. Clay fractions from a poorly drained profile separated without prior drying of the soil samples contain essentially dehydrated halloysite at the surface, this becoming progressively more hydrated with depth. Since halloysite occurs extensively in soils of widely varying drainage class the mineral is probably not the result of recent soilforming processes but may have originated during Tertiary or interglacial weathering.

Pecoraite and nepouite, Ni-serpentines, occur in the serpentinized ultramafic rocks in the Kwangcheon area, Korea, where the parent rock is classified as harzburgite and/or lherzolite. Pecoraite was precipitated twice from the solution; the early-formed pecoraite coexists with magnetite, millerite, and polydymite both in the Buk- and Nam-sites, while the late-formed pecoraite appears as well-grown colloform and opaque-free phase only in the Buk-site. The typical colloform texture of the late-formed pecoraite strongly indicates that it was precipitated from the solution in supergene conditions. Pecoraite is characterized by its extremely high Ni content and the difference in Fe content between the early- and late-formed pecoraite. Nepouite is distinguished from pecoraite by its prismatic morphology and the large degree of isomorphous substitution between Ni and Mg. The phase relations among coexisting magnetite-millerite-polydymite assemblage with the early-formed pecoraite suggest that the pecoraite might have precipitated in the extremely limited fO2 and fs2 environment from the highly Ni-concentrated solutions and is stable at 25°C and 1 bar.

Knowledge of mineral composition is helpful in the interpretation of well-logging data, where the hydrocarbon saturation is expected as the final result.It is calculated from the electric resistivity, cation exchange capacity (CEC) and porosity.Porosity is calculated from the bulk density, which is measured directly in the well, and the matrix (mineralogical, grain) density, which can be calculated precisely only when the mineral composition is known.

In the shale-sand formations, which are the subject of this study, the rock matrix can conduct electric current.The Waxman–Smits formula is applied to calculate the water saturation of such rocks.This formula combines rock porosity, water saturation, water resistivity and the CEC with the total rock resistivity measured in the well.CEC is introduced to this formula as the parameter determining the shale ability to conduct electricity.Typically, CEC is controlled by the smectite content of the rock.

In order to evaluate the input data needed in the log interpretation the extended mineralogical (quantitative mineral composition, CEC) and chemical (major, trace and REE) analyses were made for over 200 core samples obtained from four gas fields in the Miocene formation of the Carpathian Foredeep.The most important clay component: the sum of mixed-layer illite-smectite and discrete illite has been quantified.The detailed recognition of clay minerals allowed for constraining the density-neutron cross-plot, which is a well log data interpretation technique for the determination of both porosity and shale content in shale-sand formations.

The statistical multivariate analysis of all data helped to set up a comprehensive petrophysical model.A reliable correlation (r2 = 0.96) of the thermal neutron absorption cross-section (Σama) and the total natural radioactivity (GR) with CEC was established.Such good correlation allows for a continuous on-line CEC determination and therefore a reliable application of the Waxman-Smits water saturation model.Experimental equations with similar level of correlation were established for quartz, clay and carbonate contents, allowing the calculation of matrix density, required in the porosity calculation.

The high correlation of Σama with CEC reflects the presence of boron in the illite-smectite clays.

Zn-Al layered double hydroxides (LDH), before and after calcination, were tested for the removal of indigo carmine (IC) dye from solution. These LDH photocatalysts were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry/differential thermogravimetry (TG/DTG), nitrogen physisorption at −196°C, scanning electron microscopy (SEM) and diffuse reflectance spectrophotometry (DRS). The different photocatalysts were supported on polyacrylonitrile (PAN) nanofibres, so that filtration was unnecessary.

The PXRD and FTIR analyses showed that the IC adsorption on c-Zn-Al-3-500 (LDH calcined at 500°C) was enhanced by construction of the hydrotalcite matrix intercalated with the dye. The intercalation was clearly evidenced by the appearance of a peak at low °2θ values. All of the materials prepared exhibited photocatalytic activity, which for the c-Zn-Al-3-500 was comparable to that of commercial PAN-supported ZnO nanoparticles (100% degradation after 180 min). Kinetic studies showed that the degradation of the IC followed a pseudo-first order rate. The high activity and the ease of both synthesis and separation processes rendered this photocatalyst a promising candidate for environmental remediation.

Eleven shales and fourteen turbidite sandstones from the Mam Tor Beds were analysed chemically and by XRD. The ratio of kaolinite to illite plus mixed-layer clay was higher in the sandstones than in the shales, size fractions demonstrating that this ratio decreased as the grain size decreased. Shales more basinal in character than those of the Mam Tor Beds contain more illite and mixed-layer clay and less kaolinite and it is suggested that there was a lateral variation in clay mineralogy with distance from the shore line due to particle size sorting and that the character of the clay mineral fraction was retained as the turbidity current transported sediment from a nearshore environment deeper into the basin. Support for this model was obtained from the geochemistry which showed that the sandstone matrix differed compositionally from the shales. Systematic variations occurred in the turbidite sandstones but not in the shales which are therefore considered to be non-turbiditic. Only minor mineralogical changes appear to have occurred during diagenesis.

The chemical and structural stability of a Spanish sepiolite from Vallecas, Spain, was studied in 0.04 n NaOH (pH = 12.6), a saturated solution of Ca(OH)2 (pH = 12.6) and deionized/distilled water (pH = 7). The chemical stability was evaluated by determining the concentrations of Mg, Si and Ca in the solid residues during the kinetic test. The structural stability was studied by determining the changes in specific surface area and ‘crystallite’ size. The specific surface was determined by the BET method and the ‘crystallite’ size by the profile of the X-ray diffraction line. The main conclusion was that sepiolite is a material with high chemical stability in neutral and alkaline media, with no significant structural changes. However, in alkaline media, greater dissolution of silica was observed than in neutral media, the silica being derived from the most external tetrahedra attached to the OH− groups.

Discrepancies between clay mineral and organic indicators of very low-grade metamorphism have been observed from the Southern Uplands of Scotland. In the Southern Belt, I-S expandability ranges from 18–5% and chitinozoan reflectance from 0·8–2·1% R0 mean; a clear correlation exists between I-S expandability and organic maturity. At Dob's Linn in the Central Belt, I-S expandabilities range from 18–10%, and chitinozoan reflectance from 3·6–4·8% R0 mean. The results from Dob's Linn show anomalously high I-S expandabilities with respect to maturity, both in comparison with the Southern Belt and with previous work from other regions. K-feldspar is present in variable amounts in the Southern Belt, but is not detectable by XRD at Dob's Linn. Low K+ activity is believed to have resulted in a slower reaction rate at Dob's Linn, and a consequent “lag” in I-S expandability with respect to the Southern Belt.

Adsorption of Cs on two samples of marl with different calcite, quartz and clay contents and surface areas of ∼10 m2/g was followed using the batch sorption technique. The experiments were carried out in an atmosphere of N2/1% CO2 using a synthetic groundwater of pH 7·3 and an ionic strength of 0·1 m. The initial Cs concentration ranged from 10−8 to 10−4m. Sorption of Cs was non-linear, fast and reversible. At equilibrium Cs concentrations <10−8m, an isotope exchange mechanism appeared to operate, whereas at higher concentrations, sorption involved ion exchange. The distribution coefficients ranged from 23–995 ml/g. They varied markedly with rock/water ratio; this variation could be explained in terms of the non-linear isotherm displayed by Cs. Although the two samples of marl differed in composition, uptake of Cs on both samples was very similar because the content of the principal sorbing component (illite) was the same in both samples.