In the present study, the gradual layer-charge reduction of two Li-saturated smectites, SAz-1 from Arizona, USA, and FEO-G from Troodos, Cyprus, with octahedral charge of 0.54 electrons per half unit cell (e/huc) and 0.39 e/huc, respectively, was monitored by X-ray diffraction of K-saturated, ethylene glycol-solvated samples, by thermogravimetry-differential thermogravimetry, and by mid- and near-Fourier transform infrared spectroscopy after heating at 80–300ºC. With increasing heating temperature, the layer charge and cation exchange capacity (CEC) of both smectites decreased gradually due to Li fixation. At temperatures >200ºC, ~25% residual CEC was observed, suggesting incomplete Li fixation due to kinetic constraints. Dehydration of the original Li-smectites occurred in two steps, one peaking at ~100ºC and another at 175–180ºC. The latter decreased upon progressive Li fixation and vanished from smectites treated above ~125ºC. Dehydroxylation occurred at 635–640ºC in both smectites and was not affected by Li fixation. The second derivative analysis of the infrared spectra showed that Li fixation was manifested in both smectites by the growth of two new sharp OH-stretching fundamentals at ~3640 and 3670 cm−1 and their overtones at ~7115 and 7170 cm−1. The new bands constitute pairs of fixed energy and relative intensity which grow simultaneously at the expense of the broad OH-stretching and overtone features of the original smectites. Based on this result, Li fixation is suggested to be accompanied by the simultaneous formation of two distinct trioctahedral-like structural OH species, which is compatible with Li+ occupying trans-octahedral vacancies in both smectites.

Several detailed studies have been done on the characterization of organoclays and the type of structures developed when they interact with alkylammonium molecules. Few published contributions exist, however, on the distribution of surfactant within the organoclays and the mechanism by which they are intercalated. Also, although X-ray photoelectron spectroscopy (XPS) is a suitable technique for the study of the surface characteristics of organoclays, very few such XPS studies have been carried out. With the aim of contributing to a better understanding of the intercalation process, a series of organoclays was synthesized using a montmorillonite and the cationic surfactant hexadecyltrimethylammonium bromide (HDTMABr), with an increasing surfactant load of between 0.2 and 4.0 times the cation exchange capacity of the starting clay. By means of XPS, zeta potential, and thermal analysis techniques, distinguishing the strongly interacting fraction from the weakly interacting fraction of the adsorbed surfactant molecules was possible. Adsorption isotherms of each of these processes were constructed and then adjusted using the Langmuir and Dubinin-Radusquevich adsorption models. Three types of interaction between the surfactant and the clay were identified and described qualitatively and quantitatively. Two of these interactions, strong and weak, involved the hexadecyltrimethylammonium cation (HDTMA+). The third was a weak interaction involving the ion pair HDTMA+Br−. The results of this study may be useful for the comprehensive design of organoclays with specific physicochemical properties according to the application for which they are destined.

The Upper Silurian–Lower Devonian section of the Dniester gorge in Podolia and samples from boreholes located S and N of this area were studied in order to reconstruct the thermal history of Lower Paleozoic sedimentary rocks in the Dniester segment of the Peri-Tornquist margin of the East European Craton which is the most eastern part of a major shale-gas target in Europe. X-ray diffraction data for illite-smectite from shales and carbonates indicate very advanced diagenesis and maximum paleotemperatures of ~200ºC, higher than interpreted from the ‘conodont alteration index’ (CAI) data. Diagenesis of the Devonian section is slightly less advanced than that of the underlying Silurian section, indicating that it is a regional feature and the result of burial. The regional distribution of the diagenetic grade based on illite matches well with the pattern established from the CAI data. K-Ar dating of illite-smectite from Silurian bentonites and shales gave a consistent set of dates ranging from 390 to 312 Ma. To explain such advanced levels of diagenesis and such K-Ar dates, the extension of the Carboniferous foreland basin (which today is only preserved to the NW of L’viv) toward the SE on the craton margin has to be assumed. The diagenetic zonation pattern of the Carboniferous coals supports this hypothesis. The Carboniferous cover may have been either sedimentary or partially tectonic (Variscan intracratonic duplexes) in origin and the thickness, necessary for the observed level of diagenesis, may have been reduced by an elevated heat flow along the major tectonic zone at the edge of the craton (TESZ). The presence of such cover is confirmed by completely reset Cretaceous apatite fission track (AFT) ages of the Silurian bentonites. The AFT dates also imply a Tertiary heating event in the area.

The 10 Å clay mineral present in the dolomitic part of the profile (Silurian), both in bentonites and in other rocks, is aluminoceladonite or intermediate between illite and aluminoceladonite, while in the Devonian shale section only illite was documented. Chlorite is also common in the studied rocks and is at least partially authigenic. It is non-expandable in the samples from boreholes, while often expandable to variable extents in the samples from outcrops, which also contain goethite. Such variation in chlorite is attributed to contemporary weathering.

Bentonite-bonded molding sand is one of the most common mold materials used in metal casting. The high casting temperatures cause dehydration and alteration of the molding sand, thereby degrading its reusability. Neutron radiography and neutron diffraction were applied to study these processes by using pure bentonite-quartz-water mixtures in simulation casting experiments. The aim of the experiments was to compare the dehydration behavior of raw and recycled mold material in order to assess possible causes of the limited reusability of molding sands in industrial application. Neutron radiography provided quantitative data for the local water concentrations within the mold material as a function of time and temperature. Dehydration zones, condensation zones, and areas of pristine hydrated molding sand could be established clearly. The kinematics of the zones was quantified. Within four cycles of de- and rehydration, no significant differences in water kinematics were detected. The data, therefore, suggest that the industrial handling (molding-sand additives and the presence of metal melt) may have greater effects on molding-sand reusability than the intrinsic properties of the pure bentonite–quartz–water system.

A method to characterize and map both kaolinite and dickite polytypes in sandstone thin sections using infrared microspectroscopy (IRMS) was developed. Minerals identification using IRMS can be performed using the hydroxyl-stretching band of most clay minerals (3500–4000 cm−1) in spite of infrared (IR) interferences caused by the embedding resin and glass substratum. Emphasis was placed on determining the optimum analytical conditions for IR data acquisition. The best data-acquisition parameters for Fourier-transform infrared (FTIR) measurements (i.e. spectra quality as a function of beam size and the number of scans) were obtained from a series of single spectra. Then, spatial resolution was explored as a function of the IR beam size (from 50 μm × 50 μm to 15 μm × 15 μm) and the step-scan interval (i.e. the distance between two successive analysis points). The IRMS measurements were performed on thin sections of materials characterized previously using scanning electron microscopy (SEM) and chemical analysis. Using IRMS, locations on the thin sections containing nearly pure dickite or kaolinite polytypes were identified and mapped. Most spectra collected using IRMS represented kaolin mineral aggregates rather than individual crystals, however, and mixing of kaolin polytypes was common at the spatial resolution of the IR beam size used. The spatial resolution of the IRMS was comparable to optical petrography and made possible the identification of areas on the thin section for further ‘in situ’ investigation using other methods (e.g. microprobe, Laser Ablation Inductively Coupled Plasma Mass Spectrometry — LA-ICP-MS, etc.). Also, the use of blocky crystal morphology to identify dickite was questioned, as kaolinite with blocky habit was identified. Mineral mapping using IRMS seems particularly suited for investigating petrographic relationships between kaolinite and dickite in sandstone diagenesis, but could also be used for clay minerals in other rock types or soils.

Chlorite is a layered silicate mineral group of importance in geology, agriculture, and in the processing of mineral resources. A more detailed analysis of the surface charge of chlorite minerals is important in order to improve our fundamental understanding of such particle structures and their behavior in suspension. In this study, the anisotropic surface charging of chlorite has been established using Atomic Force Microscopy surface-force measurements with a silicon nitride tip. The surface-charge densities and surface potentials at the chlorite basal-plane surfaces and edge surface were obtained by fitting force curves with the Derjaguin-Landau-Verwey-Overbeek theoretical model. The results show that at pH 5.6, 8.0, and 9.0 the chlorite mica-like face is negatively charged with the isoelectric point (IEP) less than pH 5.6. In contrast, the chlorite brucite-like face is positively charged in this pH range and the IEP is greater than pH 9.0. The surface charging of the chlorite edge surface was found to be pH-dependent with the IEP occurring at pH 8.5, which is slightly greater than the edge surfaces of talc and muscovite due to the larger content of magnesium hydroxide at the chlorite edge surface. Findings from the present research are expected to provide a fundamental foundation for the analysis of industrial requirements, e.g. collector adsorption, slime coating, and particle interactions in the area of mineral-processing technology.