The formation conditions and stability fields of Fe-serpentines are still poorly understood in both terrestrial (natural or anthropic) and extraterrestrial environments. Knowledge of the effects of physical-chemical parameters on compositional and structural features of Fe-serpentines is lacking, and only a few thermodynamic parameters of these minerals are available in the literature. To fill these gaps, the synthesis of these minerals, while controlling all the physicochemical experimental parameters, was undertaken. Two hydrothermal syntheses were carried out at 90°C to investigate the effect of two different starting mineralogical mixtures on the nature of Fe-serpentines. The run products were identified by several analytical techniques (powder X-ray diffraction, transmission, and scanning electron microscopy). Berthierine crystals were synthesized from a starting mixture of kaolinite and metal iron. The berthierines synthesized show different morphologies and iron contents (~3–38 at.%). From a starting mineralogical mixture composed of quartz and metal iron, cronstedtite crystallizes. Most of the crystals are 1M polytypes. Magnetite is always associated with both berthierine and cronstedtite. Lepidocrocite was observed only in the experiment with kaolinite. These experimental results demonstrated that Fe enrichment in serpentines depends on the silicate precursor (kaolinite or quartz) of the starting mixture. The results are also in agreement with the geochemical equilibrium predicted by thermodynamic modeling, i.e. the formation of berthierine and cronstedtite in association with magnetite at the expense of metal iron and silicates.

A better understanding of the thermodynamics of radioactive cesium uptake at the surfaces of phyllosilicate minerals is needed to understand the mechanisms of selective adsorption and help guide the development of practical and inexpensive decontamination techniques. In this work, molecular dynamics simulations were carried out to determine the thermodynamics of Cs+ adsorption at the basal surface of six 2:1 phyllosilicate minerals, namely pyrophyllite, illite, muscovite, phlogopite, celadonite, and margarite. These minerals were selected to isolate the effects of the magnitude of the permanent layer charge (⩽2), its location (tetrahedral vs. octahedral sheet), and the octahedral sheet structure (dioctahedral vs. trioctahedral). Good agreement was obtained with the experiments in terms of the hydration free energy of Cs+ and the structure and thermodynamics of Cs+ adsorption at the muscovite basal surface, for which published data were available for comparison. With the exception of pyrophyllite, which did not exhibit an inner-sphere free energy minimum, all phyllosilicate minerals showed similar behavior with respect to Cs+ adsorption; notably, Cs+ adsorption was predominantly inner-sphere, whereas outer-sphere adsorption was very weak with the simulations predicting the formation of an extended outer-sphere complex. For a given location of the layer charge, the free energy of adsorption as an inner-sphere complex varied linearly with the magnitude of the layer charge. For a given layer charge location and magnitude, adsorption at phlogopite (trioctahedral sheet structure) was much less favorable than at muscovite (dioctahedral sheet structure) due to electrostatic repulsion between adsorbed Cs+ and the H atom of the OH- ion directly below the six-membered siloxane ring cavity. For a given layer charge magnitude and octahedral sheet structure, adsorption to celadonite (octahedral sheet layer charge) was favored over adsorption to muscovite (tetrahedral sheet layer charge) due to the increased distance to the surface K+ ions and the decreased distance to the O atom of the OH- ion directly below the surface cavity.

The tropical weathering of sedimentary kaolin deposits from the plateaux surrounding Manaus (Alter do Chao formation, Amazon basin, Brazil) leads to the in situ formation of thick kaolinitic soils. The structural changes of kaolinite have been investigated quantitatively by infrared spectroscopy and electron paramagnetic resonance. Both techniques consistently show that each sample contains two types of kaolinite in various proportions. The progressive decrease in kaolinite order from the bottom to the top of the profile results from the gradual replacement of an old population of well-ordered kaolinite, typical of the underlying sedimentary kaolin, by a more recent generation of poorly ordered soil kaolinite. The vertical pattern of kaolinite replacement differs from that of the transformation of Fe oxides and oxyhydroxides previously observed in the same profile. The inherited fraction of well-ordered kaolinite ranges from 60% at a depth of 9 m to 30% in the upper levels of the soil. The persistence of sedimentary kaolinite in the upper horizons suggests that the rate of kaolinite transformation is relatively slow at the time scale of lateritic soil formation. Kaolinite inheritance unlocks the lateritic record of past weathering conditions.

The isotope dilution technique using Na and Cs as index cations was used to determine the cation exchange capacity (CEC) of illite du Puy as a function of background electrolyte composition. The work showed, in accord with previous studies, that the CEC values were in the order Cs-CEC > Na-CEC. Sodium is commonly chosen as the index cation in CEC determinations using the isotope dilution method. The experimentally measured Na-CEC values for Na-illite increased from ∼75 to ∼200 meq kg−1 for NaClO4 concentrations in the range 5.6 × 10−4 to 1.25 × 10−2 M. Cesium CEC determinations showed a much less pronounced trend over a CsNO3 concentration range from 10−3 to 10−2 M. A reference Cs-CEC value of 225 meq kg−1 was chosen. Careful chemical analyses of the supernatant solutions revealed that Ca and Mg at the (sub)μmolar level were present in all the determinations, despite the extensive conditioning procedures used. Competition between (Ca + Mg) and Na for the exchange sites was put forward as an explanation for the variation of Na-CEC values. This hypothesis was confirmed in a series of single (45Ca) and double (45Ca plus 22Na) labeling experiments. Calcium-sodium selectivity coefficients (${(}_{\text{Na}}^{\text{Ca}}{\text{K}}_{\text{c}})$) were calculated from the experimental data for NaClO4 concentrations from 5.6 × 10−4 to 0.1 M and exhibited a variation from 1.6 to 14.3. A two-site cation exchange model was developed with site capacities and ${}_{\text{Na}}^{\text{Ca}}{\text{K}}_{\text{c}}$ values for each site: planar site capacity =180 meq kg−1, ${}_{\text{Na}}^{\text{Ca}}{\text{K}}_{\text{c}}^{\text{PS}}=2$; type II site capacity = 45 meq kg−1, ${}_{\text{Na}}^{\text{Ca}}{\text{K}}_{\text{c}}^{\text{II}}=80$. The model was able to predict the Na and Ca occupancies in the Na-CEC experiments over the whole range of NaClO4 concentrations. It is recommended that Cs should be used instead of Na as the index cation for determining the CEC of illite.

Bentonite, biotite, illite, kaolin, muscovite, vermiculite and zeolite were acidified or alkalized with HCl orNaOH of concentrations 0.0, 0.1, 1.0 and 5.0 mole dm−3 at room temperature for 2 weeks and converted into Ca homoionic forms. Low-temperature nitrogen and room-temperature water-vapor adsorption-desorption isotherms were used to characterize the mineral pores of radii between 1 and 30 nm. Nanopore volumes, size distributions, average radii and fractal dimensions were calculated. Values calculated from the nitrogen isotherms differed from those derived from water-vapor data. With an increase of the acid-treatment concentration, the pore volumes measured using both adsorption techniques increased markedly for all minerals. The pore radii measured from nitrogen isotherms appeared to decrease for all minerals except zeolite, while the pore radius calculated from water-vapor data increased in most cases. The fractal dimension measured from water vapor isotherms decreased in all cases indicating smoothing of the mineral surfaces and decrease in pore complexity. No well defined trends in any of the pore parameters listed above were noted under alkaline treatment. In the reaction of each mineral with acid and alkali treatments, the individual character of the mineral and the presence of impurities seems important.

The adsorption properties of clay minerals (e.g. montmorillonite and palygorskite) have been improved through chemical treatment methods. However, the addition of extra chemicals is often not friendly to the environment and powdered clay-mineral adsorbents are inconvenient for some applications. To overcome these drawbacks in the present study, granular montmorillonite-palygorskite adsorbents (GMPA) were successfully prepared using Na-alginate and thermal treatments to improve heavy metal removal from water. The properties of GMPA samples under different calcination temperatures were examined using thermogravimetric (TG) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area (BET). The results indicated that loss of mass by GMPA relative to the untreated montmorillonite-palygorskite was due to the loss of water, adsorbed Na-alginate, and mineral decomposition during thermal treatment. Changes in the morphology and crystallinity were significant at calcination temperatures from 500°C to 1000°C. The layered morphology totally disappeared after calcination at 1000°C, while transformation of the montmorillonite and palygorskite to a non-crystalline material was almost complete at 800°C and new crystalline phases appeared. Calcination temperature had a significant influence on the specific surface areas and pore volumes of GMPA. Both the changes in texture and chemical structure affected Pb2+ and Cu2+ removal. The GMPA sample produced at a 600°C calcination temperature was the most promising adsorbent for heavy metal removal from water.

Citrate is distributed widely in the Earth’s surface environments as a biological product released by microbes and plants. Citrate is also often used as a chelating agent for the selective dissolution of iron coatings and free iron oxides in soils. Adsorption experiments of Cs+ and IO3− before and after the complexation of citrate with the pseudoboehmite surface were conducted to evaluate the effects of citrate on the adsorption of these ions on the surface of pseudoboehmite. Additional adsorption experiments of Cs+ and IO3− after the decomposition of citrate adsorbed on the pseudoboehmite surface were also performed to confirm the recovery of the original surface properties. Citrate decomposition was carried out by means of 10% H2O2 treatments at 75°C and pH 5, 7, and 9. The results indicated that citrate complexation decreased remarkably the adsorption of both Cs+ and IO3− in the pH range 3–10, which was due to a decrease in the number of active charged sites available for adsorption of these ions. Decomposition of citrate adsorbed on the pseudoboehmite surface was found to be complete after three rounds of treatment with 10% H2O2 at 75°C and pH > 7. After the decomposition of citrate adsorbed on the pseudoboehmite surface, the adsorption of both Cs+ and IO3− was restored completely to the initial amounts before citrate complexation, and the inhibition effect of citrate on the adsorption of these ions disappeared under all pH conditions.

Of all the known pillared layered clays (PILC), Al-PILC is the most studied. In spite of that, its use on a commercial scale is not yet possible due to the large amount of water required for its synthesis. The aim of the present work was to take advantage of the beneficial effects of ultrasound radiation for reducing intercalation time, and to optimize the synthesis parameters in order to find a viable industrial means of preparing Al-PILC.

A comprehensive study of the effect of ultrasonic radiation on the parameters which have a direct effect on the amount of water used in the synthesis was conducted, specifically on the effects of: (1) mmol of Al/g of clay ratio (R) by decreasing the volume of A1 solution and keeping the amount of clay constant, (2) the concentration of clay in the initial suspension (or not suspending the clay at all), and (3) the concentration of the A1 precursor solution. The use of ultrasonic radiation produced the expected reduction in exchange time which was attributed to a decrease of the clay-particle size. This decrease of particle size gave rise to an improvement in the diffusion of the A1 precursor towards the core of the clay grain leading to solids with increased surface areas, basal spacing and X-ray diffraction peak definition. By optimizing the synthesis parameters directly involved in the consumption of water, it was possible to decrease the amount used by >60%.

The aim of the work was to study the effect of organo-montmorillonite (OMt) on the properties of hydrogenated nitrile rubber (HNBR)/OMt nanocomposites. The nanocomposites were prepared by a melt intercalation method. The structure of the composites was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The behavior of stress-strain, aging resistance, solvent resistance, and the dynamic mechanical properties of HNBR/OMt nanocomposites were investigated. The TEM and XRD results showed that the OMt layers were dispersed homogeneously in the HNBR matrix. The HNBR/OMt nanocomposites showed excellent mechanical properties which were attributed to the nanometer scale dispersion and strong interaction between the HNBR and OMt. The composites possessed excellent aging resistance and oil resistance, which improved with OMt content. Dynamic mechanical analysis showed that the glass-transition temperature, Tg, of the HNBR/OMt nanocomposites was increased and the nanocomposites had a good rolling resistance in comparison to pure HNBR. The composites displayed better dynamic mechanical properties.

Kaolinite is often a cause of deformation in soft-rock tunnel engineering, leading to safety problems. In order to gain a better predictive understanding of the governing principles associated with this phenomenon, the physical and chemical properties of kaolinite were investigated using an efficient, firstprinciples scheme for studying isomorphic substitution of Al ions in kaolinite by two kinds of other elements (namely, the dual defect). Elements that are relatively common in natural kaolinite were chosen from groups II (Be, Mg, Ca, and Sr) and III (Fe and Sc) of the Periodic Table as dual-defect ions to substitute for Al ions in kaolinite. By systematically calculating the impurity-formation energies (which characterize the difference in the total crystal energy before and after the defect arises) and transitionenergy levels, which characterize the energy cost for the transformation between two different charge states, the (Be + Sc)Al (i.e. the replacement of two specific Al ions in kaolinite by external Be and Sc ions), (Ca + Sc)Al, (Mg + Sc)Al, and (Sr + Sc)Al ion pairs were determined to have low formation energies, suggesting that these combinations of ions can easily substitute for Al ions in kaolinite. The (Be + Fe)Al, (Ca + Fe)Al, (Mg + Fe)Al, and (Sr + Fe)Al ion pairs have relatively high formation energies which make isomorphic substitution (or doping) in kaolinite difficult. Moreover, these combinations of elements from groups II and III were found to have relatively low transition-energy levels compared with other element pairs. Among them, (Sr + Sc)Al have the lowest transition-energy level at 0.06 eV above the valence band maximum. When compared with single external substitutional defects in kaolinite, remarkably, the dual defects have relatively low formation energies and transition-energy levels. The results are helpful in understanding the chemical and physical properties of natural kaolinite.

When clay minerals, notably smectites, intercalate organic cations, their interlayer surfaces change from hydrophilic to hydrophobic. The resultant intercalates, known as organo-clays (OCs), have a large affinity for hydrophobic organic contaminants (HOCs). Organo-clays are used as sorbents of HOCs in wastewater treatment and as sorptive barriers in landfill liners. The structural and sorptive characteristics of OCs with respect to HOCs have been studied extensively, and a large volume of literature has accumulated over the past few decades. The interactions of OCs with HOCs and the various approaches to improving the sorption capacity of OCs are reviewed here, with particular reference to the application of novel analytical techniques, such as molecular modeling, to characterizing the OC—HOC interaction.

Policy responses to the inflation crisis in Belgium and the Netherlands show great similarities but also significant differences. In both countries responses were quick and substantial. Measures covered prices more than household incomes while universal, not earmarked measures exceeded selective interventions. However, there were also major differences between the two countries. Because Belgium, unlike the Netherlands, could fall back on the mechanism of automatic indexation of wages and social benefits; it relied more on existing universal policy instruments while in the Netherlands more targeted ad hoc measures were taken which also allowed for innovation in policy making. These different policy paths have their origins in the 1980s when policy models began to diverge and different legacies emerged.

In order to elucidate the process of mineralization of clay minerals in fault gouge and its spatial-temporal relationship with fault-zone evolution and hydrothermal alteration, X-ray diffraction (XRD) analysis and K-Ar dating were performed on clay samples from the Kojaku Granite of central Japan, including fault gouge along an active fault. The area studied is suitable for understanding thermal constraints on clay mineralization because the wall rock is homogeneous and its thermal history well defined. The results from XRD indicated that the clay minerals in the gouge samples are dioctahedral smectite, kaolinite, and 1Md illite, whereas clay fillings in fractures and joints in the intact granite (clay vein) include 2M1 illite in addition to dioctahedral smectite and 1Md illite. The evolution of clay mineralization is reconstructed as follows: (1) high-temperature hydrothermal alteration of feldspar and biotite produced 2M1 illite in clay veins; and (2) alteration accompanied by shearing at a lower temperature resulted in the formation of 1Md illite in the gouges. This scenario is consistent with the cooling history of the granite constrained by fission-track, U-Pb, and K-Ar dating methods. K-Ar dating of the clay samples separated into multiple particle-size fractions indicated that the low-temperature alteration leading to the production of 1Md illite was dated to ~40 Ma. Based on the cooling history of the granite, the 1Md illite formed at temperatures of 60–120°C. This temperature range was at the lower limit of the range reported in previous studies for faults. The spatial and geometrical relation of the faults studied and their K-Ar ages infer evolution which can be described as extensive development of small-scale faults at ~40 Ma followed by coalescence of the small-scale faults to form a larger, recently reactivated, active fault. The K-Ar ages have not been reset by the recent near-surface fault activity.

Because of the anisotropy in bonding, layered hydroxides crystallize with extensive structural disorder due to the incorporation of stacking faults. In contrast, the loss of crystallinity in Br−-ion intercalated layered double hydroxides (LDHs) arises due to the positional disorder of Br− in the interlayer. The structure of the interlayer in other LDHs is poorly understood due to the low X-ray scattering power of the commonly found anions such as Cl− and ${\text{NO}}_3^{-}$\$\end{document} relative to that of the metal hydroxide layers. On heating to 175°C, the Br− ion migrates from positions of lesser site degeneracy to those of greater site degeneracy as dehydration of the interlayer opens up access to positions hitherto occupied by intercalated water molecules. The new (18h) site is situated closer to the proton of the metal hydroxide layer (1.809 Å) compared to the 6c site (2.402 Å). This shows a pre-association of the bromide ion with the proton of the hydroxide layer leading to the release of HBr upon decomposition of the bromide-containing LDHs. The fact that Cl−-containing LDHs also decompose with the evolution of HCl shows that such a redistribution of the atoms in the interlayer is more common than is generally recognized.

The potential for structural failure of consolidated clay materials, which is of great importance in many applications, typically are assessed by measuring the localized strain bands that develop under anisotropic load stress. Most methods are precluded from providing a full understanding of the strain anisotropy because they only give two-dimensional information about the stressed clay blocks. The purpose of the present study was to investigate three-dimensional strain localization in a kaolinite matrix, caused by strain anisotropy due to a biaxial plane-strain test, using a relatively new method known as Anisotropy of Magnetic Susceptibility (AMS). This method involves induction of magnetism in an oriented sample in different directions and measurement of the induced magnetization in each direction. The AMS analyses were performed on core samples from different parts of the deformed kaolinite matrix. The degree of magnetic anisotropy (P′), which is a measure of the intensity of magnetic fabric and a gauge of strain intensity, was shown to be greater in cores containing shear bands than in those containing none. A threshold value for P′ for the deformed kaolinite matrix was identified, above which shear bands may develop. The comparison of the shape parameter (T), obtained from undeformed and deformed samples, illustrated a superimposition of prolate strain over the original oblate fabric of the kaolinite matrix. The orientation of the principal strain axis revealed that reorientation or rotation of the principal axis occurred along the shear bands.