Progress in science is not a linear function of time but resembles more closely a sigmoidal process in which new trends depend on the nucleation of new ideas and the re-activation of older studies. New and improved instruments, particularly electron microscopes and microprobes, infrared spectrometers and atomic absorption analysers have been the nucleating agents for many new lines of investigation. The interdisciplinary nature of clay mineralogy makes communication between different areas of study very important and the clay mineral societies have an important part to play in this respect.

In the future, renewed efforts to obtain a convenient and reliable method of quantitative mineral analysis are likely to be made. Crystal structure analysis will be directed increasingly towards the study of order and disorder in cation distributions, layer charges, and layer stacking arrangements. Studies of domain structures in layer silicates will continue, and further refinements in mixed-layer structure analysis can be expected. Infrared spectroscopic analysis will increasingly become a major tool. The study of clay mineral synthesis and alteration in nature and in the laboratory shows signs of important re-activation. Clay-organic studies are developing in many directions.

A basic lead carbonate-montmorillonitec omplexw as prepared by treating a natural montmorillonite hydrothermally for 120 h at 250°C with lead powder, dry ice and lead nitrate solution. The product is a non-swelling material showing well-outlined, hexagonal, thin plates <1 µm in size; the symmetry is pseudo-orthorhombic, a = 5·141(7) Å, b = 9·005(5) Å, c = 17·420(4) Å, and Z = 2. The X-ray powder pattern is characterized by a 17·4 Å reflection and an integral series to the 14th order. The TG-DTA curves of this 17 Å-mineral showed one endotherm around 400°C accompanied by weight loss and two exthotherms at about 680 and 780°C By applying hightemperature X-ray diffractometry (XRD) and infrared (IR) spectroscopy, it was found that the endotherm is due to decomposition of carbonate hydroxide in the interlayer, while the two exthotherms are caused by crystallization of a hexagonal phase of PbAl2Si2O8 and by the conversion of this phase into lead feldspar, respectively. The crystal structure of the 17 Å-mineral was determined and refined as a 2:1 dioctahedral smectite interlayered with a hydrocerussite-like layer by a one-dimensional Fourier synthesis method.

This study reports on the effects of dielectric barrier discharge-like (DBD-like) plasma jet treatment at atmospheric pressure on Ag cation-exchanged clinoptilolite. In the plasma treatment process, argon plasma was applied to the surface of pellet samples prepared with Ag-clinoptilolite. After DBD-like plasma jet treatment for 30 and 60 min, remarkable colour changes were observed in the pellet samples. These changes indicate that the DBD-like plasma jet application led to the successful reduction of Ag+ to its metallic forms, which was further confirmed by the results of ultraviolet–visible diffuse reflectance spectroscopy. The structural, composition and morphological properties of the DBD-like plasma jet-treated samples were characterized using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray analyses, and they were compared to the untreated Ag-clinoptilolite. The DBD-like plasma jet treatment caused no detectable structural changes in clinoptilolite within the analytical limitations of the methods used. The FTIR spectra show that the plasma treatment causes discharge-induced functional changes in the hydroxyl stretching region. The peaks appearing in the XRD patterns confirmed the reduction of Ag+ to Ag0 after exposure to the plasma. The present study indicates that the reduction of Ag+ cations to their metallic forms can be performed successfully using the proposed method without collapsing the crystal structure of the Ag-clinoptilolite.

Toxic pharmaceutical pollutants, such as nicotine, represent a significant threat to natural water sources due to their continuous discharge. To address this issue, clay minerals and their composites have demonstrated exceptional adsorptive and remedial capabilities for wastewater purification. This research focused on developing green clay-polymeric adsorbents for the efficient removal of pharmaceutical pollutants from industrial wastewater. The synthesis involves creating halloysite nanotube–polythiophene nanocomposites through a green and cost-effective method using vapour polymerization and a solvent-free, ball-milled technique for the adsorptive removal of nicotine from wastewater. The investigation evaluates the impacts of preparation, modification and environmental conditions on the adsorptive performance of these clay-based nanocomposites compared to pure polythiophene. The polymerization process was evaluated by varying the vapour polymerization holding time for a fixed amount of oxidant (FeCl3) and halloysite nanotube (HNT) to investigate the impacts of monomer vapour exposure time on the polymerization of nanocomposites. Following the characterization of the synthesized adsorbents using various methods, the study investigated the impacts of various parameters (e.g. adsorbent dosage, pH and contact time) on the adsorption capabilities of the materials on a laboratory scale. The results revealed that the incorporation of HNT improved the adsorbing performance of nanocomposites. The pH, absorbent concentration and contact time directly affect nicotine adsorption. Significantly, halloysite–polythiophene 3 with a 2 h polymerization duration demonstrated the maximum adsorption efficacy of 78.94% at pH 10 after a 24 h contact time. The environmentally friendly halloysite-based nanocomposite shows promising potential as an effective adsorbent for pharmaceutical pollutant (nicotine) removal from aquatic environments.

Among early observers of the origin and occurrence of clay minerals were those geologists who described the hyarothermal alteration of felspar in granite to kaolinite and of some basic igneous rocks to fuller's earth. There were speculations into the origin of bauxite and laterite and of the effect of weathering on various rocks and minerals in different climates. Little progressr however, was made until clay minerals could be identified by X-ray diffraction and other methods.

Modern studies (Grim 1953) of the formation of clay minerals begin with Noll's hydrothermal synthesis of montmorillonite (1930), pyrophyllite, kaolinite, and mica (1936); since then, most of the clay minerals have been synthesised from their oxides, though attapulgite and hydrated halloysite have not yet been made in the laboratory. Even to-day not enough experimental observations have been made to allow really convincing phase-rule diagrams of these hydrated systems to be made.

The charge transfer process that occurs in two samples of Wyoming montmorillonite of different grain size pillared with Zr by interaction with perylene (Pe) and tetracyanoethylene (TCNE) has been studied. These smectites are strongly affected by the exchange of Zr and appear to be strong electron acceptors and weak donors. The ESR results show that their ability to form charge transfer radicals is related to the details of preparation, which most probably control the accessibility of Pe and TCNE to the internal surface.

For some time research workers have directed their attention to the study of ferriferous minerals. Researches on iron ores have led us to take up this problem. We shall give here the results of our observations on some minerals considered to be pure, belonging to the collection of the Museum National d'Histoire Naturelle, and on samples extracted by sedimentation from various ores.

This shows that the different samples belong to three types, with 10Å, 14Å and 7Å spacing. We will consider only the last two.

1. 14Å type (chlorite).—This includes the Chamoson chamosite, the bavalite from Bas-Vallon, metachlorite from Radauthal, and the chlorites extracted from ores from Soumont (Calvados), Auboue, Angevilliers, Andun-le-Tiche, Godbrańge (Lorraine).

The structures of vermiculite and montmorillonite are very similar in that they consist of talc-like or pyrophyllite-like layers interleaved with layers of water molecules, the latter carrying exchangeable cations. In vermiculite, the exchange positions are normally filled by Mg ions, and the water layers consist of double sheets of water molecules with the exchangeable Mg ions presumably centrally placed. The water layers in natural Mg-saturated vermiculite are 5.1 Å high and it seems probable that this distance is fixed by the size of the hydration shells surrounding the exchangeable Mg ions as one of us (G.F.W.) has previously suggested.

Although vermiculite is found in particles of clay size, it also occurs as large flakes produced by the hydrothermal alteration of mica. This seemed a good reason for making a Fourier curve of the mineral in the c-direction with the object of examining the organization of the water layers. It was hoped that greater detail might be obtained from single crystals of vermiculite than would be possible in the case of montmorillonite, where oriented aggregates consisting of large numbers of very small crystals must of necessity be used.

Well crystallized chlorite has been detected in a Typic Hapludult developed on quartz porphyry at Ulsan, Korea, after treatment of the <0.2 µm fraction with a high-gradient magnetic separation (HGMS) technique. The X-ray diffraction (XRD) characteristics of the chlorite suggest that it is an Fe-rich variety and this was confirmed by energy dispersive spectroscopy (EDS) analysis. The chlorite could not be detected with certainty in the <0.2 µm fraction but is clearly present throughout the soil profile in the <0.2 µm fraction. It is suggested that this chlorite is residual inherited chlorite, the rest of which has dissolved in the acidic environment (pH 4—5).

An Illite/Montmorillonite mineral found in a porphyritic rock of Alpe di Siusi has an I/M ratio of 80:20. Introducing proper chemical parameters in a Q-Mode program of sixty-six Illites and Illite/Montmorillonite from the literature suggests the possibility of distinguishing Illites from Illite/Montmorillonite.

The influence of Zn on the adsorption and desorption of Cry1Ab toxin from Bacillus thuringiensis (Bt) on palygorskite and montmorillonite was studied. The adsorption of the toxin gradually increased with increasing Zn concentration from 0 to 1.0 mmol L–1, and then decreased with further increase in Zn concentration. The adsorption isotherms of the toxin in the absence and presence of Zn were well described by the Langmuir equation (R2 > 0.9810–0.9991). The separation factor (RL) decreased with increase of Zn concentration, suggesting that the irreversibility of the adsorption increases. The XRD results showed that the treatment by Tris buffer or Zn(NO3)2 solution caused an expansion of the interlayer space of montmorillonite but did not affect palygorskite. The IR spectra suggest that Zn was likely to be combined with amino groups on the surface of the toxin. The presence of Zn during the adsorption of the toxin decreased desorption, suggesting that the residual risk of toxin would be exacerbated if soil is polluted by zinc.

The Linkuo terrace, situated to the west of the Taipei Basin in NW Taiwan, has thick red soils that have been little studied. This paper aims to interpret the development of these soils through chemical and micromorphological investigations, and relate the soils to their palaeo-environments. The soil samples were air dried, crushed and passed through a 2 mm sieve, and then subjected to conventional soil chemical and physical analyses, together with clay mineralogical and morphological characterization. Pedons I and II were clay with low base saturation (BS), cation-exchange capacity (CEC), and exchangeable cations. The pH of pedons I and II ranged from 3.80 to 5.26. The low magnetic susceptibility of these soils indicates that no magnetite (Fe3O4) or maghemite (γ-Fe2O3) are present. X-ray diffraction patterns of the magnetic clay fraction showed lepidocrocite, goethite and hematite, the amounts of which may relate to water fluctuation in the soil environments. Illite, kaolinite and quartz are major clay minerals in the red soil clay fractions. The micromorphology of all horizons showed a great accumulation of Fe-oxides. The upper horizon showed darkened isotropic Fe-oxide materials, and lower horizon showed a black to reddish dense plasma with soil matrix. The groundmass of the oxic horizon is generally characterized by a homogeneous distribution of the different coarse and fine constituents. The thick (4 m depth) and homogeneous red soils of the Linkuo terrace were developed from fine sediments after the gradual subsidence of the Taipei Basin. Alarge amount of gravel was flushed from the Xindian River before the Taipei Basin subsided. The Linkuo red soils can be classified as mesic, Typic Kandiudox. From the chemical compositions of clay fractions and the red soil features, these red soils can be considered as lateritic red earths or red earths that do not reach the criteria for laterite.

Two types of mineral fillers, talc and mica, were compounded into polypropylene (PP) via a twin-screw extruder. The morphologies and mechanical properties of the resultant composites were investigated. The dispersion of minerals in PP was observed using Focused Ion Beam (FIB) techniques. The particle size distribution (PSD) and aspect ratio (AR) of particles in the polymer phase were obtained from FIB image analysis. It was found that FIB imaging displays directly the micron to mesoscale level dispersion of particles in polymeric composites. The technique has significant potential for characterizing such materials, having some advantages over ‘traditional’ scanning and transmission electron microscopy in terms of generating representative data in a realistic timescale. The PSD and AR distribution and degree of dispersion in the composites give insights into the modification of mechanical properties of the composites studied.

The objective of the DOPAS international project is to design a sealing-plug system for deep geological repository (DGR) use, to provide detailed plans for the design of such plugs, to test the characteristics of the materials to be used and the construction technology and to install four experimental in situ plugs. The Czech experimental pressure and sealing-plug (EPSP) experiment is being conducted in a rock environment consisting of granitoids at the Josef Regional Underground Research Centre. The concept of the experiment is based primarily on the use of materials and technology available in the Czech Republic and the principal aim is to demonstrate the technical viability and functioning of a pressure-resistant plug located in a future DGR. The completion of the EPSP experiment will contribute towards both the demonstration of how sealing-plug systems behave under real underground conditions and the long-term safety of a future DGR in the Czech Republic.

Several generations of chamosite, including a red variety, occur in the Ordovician hydrothermalized oolitic ironstone from Saint-Aubin-des-Châteaux (Armorican Massif, France). Their chemical re-examination indicates a low Mg content (0.925 < Fe/(Fe + Mg) < 0.954), but a significant variation in IVAl. Minor vanadium is present at up to 1.1 wt.% oxide. Variations in IVAl, the vanadium content and the colour of chamosite are related to the hydrothermal reworking of the ironstone. Taking into account other published data, the ideal composition of chamosite is (Fe5–xAl1+x)(Si3–xAl1+x)O10(OH)8, with 0.2 < x < 0.8 (0.2: equilibrium with quartz; 0.8: SiO2 deficit). The red chamosite (IIb polytype) has a mean composition of (Fe3.87Mg0.23Mn0.01□0.07Al1.74V0.07)(Si2.33Al1.67)O10(OH)8. This chamosite is strongly pleochroic, from pale yellow (E || (001)) to deep orange red (E ⊥ (001)). Visible–near-infrared absorbance spectra show a specific absorption band centred at ~550 nm for E ⊥ (001), due to a proposed new variety of Fe/V intervalence charge-transfer mechanism in the octahedral sheet, possibly Fe2+ – V4+ → Fe3+ – V3+. While the formation of green chamosite varieties is controlled by reducing conditions due to the presence of organic matter as a buffer, that of red chamosite would indicate locally a weak increase of fO2 related to oxidizing hydrothermal solutions.

Uniaxial and isothermal compression tests of kaolinite were carried out using molecular dynamics simulations. Five different temperatures (300, 400, 500, 600 and 700 K) and pressures ranging from 0.0001 to 50 GPa were selected to study the temperature and pressure effects on the mechanical properties of kaolinite. As kaolinite may undergo a phase transition at ~1572 K, a highest temperature of 700 K was chosen to avoid such structural change. The Young's modulus, strength and elastic constants of kaolinite under various temperatures were calculated, and the relative change of the elastic constant C33 with temperature was found to be almost 12 times greater than the relative change of the interlayer constant C11. The microstructures under various compressive strains were tracked and they exhibited various failure modes in three directions. The temperature and pressure effects on the mechanical properties of three crystal directions were analysed. The results showed that the Young's modulus of the z-direction is the most affected by temperature; however, the influence of temperature on the strengths of the three crystal directions was the same. In addition, the structure of the z-direction was the most sensitive to temperature under the same hydrostatic pressure due to the weak interactions between layers.

The development and application of Fe-rich palygorskite clay has been restricted significantly by its red colour and low grade. Moreover, the nano-structured properties of palygorskite and the relatively large Fe content of Fe-rich palygorskite clay have received insufficient attention. The present study involved the synthesis of Ni-based catalysts via a coprecipitation method using Fe-rich palygorskite clay as the support. The catalysts were then evaluated for their performance for catalytic steam reforming of toluene (CSRT). The experimental findings revealed that the Fe in Fe-rich palygorskite clay interacted strongly with Ni and formed Fe-Ni alloys. The catalyst with a Ni/Fe mass ratio of 14 (Ni14/FePal) calcined in air at 600°C exhibited superior performance for CSRT under the reaction temperature 700°C and S/C molar ratio of 1.0. According to the kinetics study, Ni14/FePal exhibited the lowest apparent activation energy (33.99 kJ mol−1) among the catalysts, which further confirmed the superior catalytic activity in CSRT. The characterizations of the catalysts used demonstrated that the excellent stability and resistance to coke formation of Ni14/FePal were attributable to the presence of a sufficient amount of highly dispersed Fe-Ni alloys on its surface.