Al-lizardite has been synthesized under hydrothermal conditions (200ºC). Morphologically, Al-lizardite consists of thin platy particles ~400 Å wide and ~150 Å thick. Structurally, the X-ray diffraction patterns indicate that the 2H2 polytype is dominant, with cell parameters: a = 5.311(0.006) Å; c = 14.333 (0.013) Å and space group P63. High-resolution transmission electron microscopy images revealed, however, the presence of other polytypes and abundant stacking disorder. Chemically, Al-lizardite consists of a single population with average tetrahedral composition Si1.74Al0.26. In contrast to previously described Al-rich serpentines (amesite and Al-lizardite), this Al-lizardite is characterized by an asymmetrical Al distribution, with VIAl ≈0.70 and IVAl ≈0.25 atoms per formula unit.

Mössbauer spectroscopy is the technique of recoil-free resonant emission and absorption of gamma rays. It has the advantage of being oblivious to all elements except the one under survey. In the case of materials formed on the earth’s surface, such as soils and clays, the only propitious element is Fe. Iron is the fourth most abundant element in the Earth’s crust, it is essential for life, and almost all environmental materials contain at least some Fe. It is also fortuitous that 57Fe Mössbauer spectroscopy is among the most straightforward to operate. 57Fe Mössbauer spectroscopy thus allows the characterization of iron speciation, and thereby of environmental conditions, over a wide range of concentrations, making it an extremely effective environmental probe.

Straightforward as it may seem, Mössbauer spectroscopy nevertheless has many pitfalls. Besides problems arising from the basic physics, complications can arise among other causes from imperfect crystallinity (small particle size), non-stoichiometry, interparticle effects and isomorphous substitutions.

In this paper a succinct review of the basic principles of Mössbauer spectroscopy is presented, followed by examples of Mössbauer spectra of minerals that are common constituents of clays and soils, and by more complex cases of soils, clays and fired clays.

In recent years, experimental and theoretical methods have provided new insights into the size, shape, reactivity, and stability of clay minerals. Although diverse and complex, the surface chemistry of all clay minerals is defined spatially on a common scale of nanometres. This review is organized around the nanoscale architecture of clay minerals examined at several different length scales. The first, and perhaps most important, is the length scale associated with Hbonding in clay minerals. Hbonding interactions define the size and shape of 1:1 phyllosilicates and dominate the surface chemistry of many clay minerals. Structural and surface OHgroups contained within and on the surface of clay minerals provide a type of ‘molecular reporter group’ and are sensitive to subtle changes in their local environment. Examples of OH-reporter group studies in clay minerals, and the spatial scales at which they provide diagnostic information, are examined. The second length scale considered here is that associated with clay–water and clay–organic interactions. Inorganic and organic solutes can be used to explore the surface chemistry of clay minerals. Similar to the use of reporter groups, molecular probes have diagnostic properties that are sensitive to changes in their molecular environment. Clay–water interactions occur at a length scale that extends from the size of the H2O molecule (~0.3 nm) to the larger scales associated with clay-swelling (>10 nm). Similarly, clay–organic interactions are also defined, in part, on the basis of their molecular size, in addition to the type of chemical bonding interactions that take place between the organic solute and the clay surface. Examples illustrating the use of clay–water and clay–organic solute interactions as molecular probes are presented. The largest scale to be considered is that of the particles themselves, with scales that approach micrometres. Recent developments in the synthesis and characterization of ultrathin hybrid films of clay minerals provide complementary information about the nature and distribution of active sites on clay minerals, as well as providing new opportunities to exploit the surface chemistry of clay minerals in the design of functional materials.

Soil solution chemistry, especially pH and the presence of multivalent ions, affects the surface charge (SC) of Fe oxides and accordingly colloidal stability and sorption properties. The SC of synthetic goethite and hematite was quantified in the presence of different electrolytes (NaCl, CaCl2, Na2SO4 and CaSO4) by combining the streaming potential with polyelectrolyte titration. The point of zero charge (PZC) for goethite was observed at pH 8.2 and the stability field around the PZC, where colloids are flocculated, is more extended (±1 pH unit) than that of hematite with a PZC at pH 7.1 (±0.5 pH unit). The SC decreases with increasing SO4 concentration, indicating adsorption of SO4 on the oxide, whereas the presence of Ca increases the SC. At pH 4, the addition of 0.1 mmol l–1 Na2SO4 induced a decrease in SC from 1.5 to 0.380 μmolc m–2 for goethite and from 0.85 to 0.42 μmolc m–2 for hematite. In a suspension with 0.1 mmol l–1 Na2SO4, the number of colloids is already reduced, and both oxides flocculate rapidly and completely at >0.5 mmol l–1 Na2SO4. While the addition of SO4 did not affect charge titrations with the cationic polyelectrolyte, the anionic polyelectrolyte formed complexes with Ca, resulting in an overestimation of positive SC. The electrolyte CaSO4 is most efficient at keeping goethite and hematite in the pH range 4–10 in the flocculated state. Besides pH, the presence of multivalent ions should also be considered when predicting colloid mediated transport and adsorption properties of anionic substances by Fe oxides in soil systems.

The chlorite-group mineral chamosite occurs in nanocrystalline form (~200 nm grain size) as a naturally occurring clay in the Quaternary marine sedimentary deposits near Kudiamozhi, Tuticorin District, Tamil Nadu, India; samples were used in this study as a reusable catalyst. The clay has the usual alternating tetrahedral-octahedral-tetrahedral silicate/aluminate/silicate layer structural arrangement (sometimes called the 2:1 silicate or talc layer structure). The interlayer and the t-o-t layer are bound together by both electrostatic and hydrogen-bonding forces. This natural clay catalyst has been well characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), temperature programmed desorption (TPD), thermal analysis and BET surface area measurements (Sreedhar et al., 2009); it has been utilized for various organic transformations such as acylation of alcohols and amines, cyclization of arylaldehydes with O-phenylenediamines and C-O bond formation reactions.

The effects of acid activation on the chemical composition, surface area and pore structure of palygorskite from Xuyi (Jiangsu, P.R. China) were investigated systematically using X-ray fluorescence (XRF) and BET techniques. The palygorskite samples were activated with HCl, H2SO4 and H3PO4 of various concentrations at 80ºC for 4 h. The influences of acid concentration and acid type on the chemical composition, adsorption-desorption isotherms at 77 K, pore-size distribution, surface area and pore volume were studied in detail. The contents of most components of palygorskite decrease with increasing acid concentration except for Si and Ti. HCl shows a greater activation activity and its effect on the dissolution of components of palygorskite is greater than that of H2SO4 and H3PO4. It was found that 3 mol l–1 H3PO4 is a more efficient activator for increasing the number of micropores in palygorskite, whereas 12 mol l–1 HCl is more suitable for use in enhancing the number of meso- and macropores. The acid concentration and acid type have a great influence on the surface area and pore volume. HCl is the most effective at enhancing the external surface area and mesopore volume of palygorskite, whereas, H3PO4 is more suitable for use in improving the micropore surface and volume.

The effects of acid and Al concentration, type of Al salt, treatment temperature and time of removal of Mg from sepiolite have been investigated, as has the use of modified sepiolite as an active fluid catalytic cracking (FCC) matrix. The samples were characterized by N2 adsorption and X-ray diffraction. Mg removal from sepiolite increased with increasing acid and Al ion concentration, treatment time and temperature. The temperature had the greatest impact on Mg removal. After acid and Al modification, 29% of the Mg was removed. When using the modified sepiolites as active matrices in FCC catalysts, the specific surface area, pore volume and mesoporous pore volume of the catalysts increased and they exhibited excellent performance in resisting the effects of heavy-metals as a result of the introduction of Mg oxide from the modified sepiolite.

A grafted polymer (P(MMA-MAh)-PEGME)) was synthesized by reacting poly(ethylene glycol) monomethyl ether (PEGME) with copolymer of poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)and end-capping the residual carboxylic acid with methanol. Natural rectorite (REC) was made organophilic by modification with the surfactant dodecyl benzyl dimethyl ammonium chloride. The organoclay was termed OREC and was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of the grafted polymer (used as a polymer matrix), propylene carbonate (PC) as a plasticizer and LiClO4 as a lithium ion producer.

The temperature dependence of the ionic conductivity of the GPEs agreed well with the VTF (Vogel-Tamman-Fulcher) relation. 5 phr doses of OREC resulted in the highest ionic conductivity. Using OREC also considerably improved the plasticizer retention levels. As a consequence of OREC occupation of the free volume space in the polymer matrix of GPEs, the bulk resistance of the GPEs was reduced and the glass transition temperature (Tg) increased. From the present research, it can be concluded that the incorporation of PEGME into the copolymer of P(MMA-MAh) produced a great improvement in ionic conductivity, plasticizer retention capability and movement of carrier charge of Li+.

Kaolin is found in deposits of economic concentration in the Jabal Al-Harad/ Batn El-Ghoul area in southern Jordan. Ten representative kaolin samples were collected from the area and investigated for their mineralogical and chemical composition. Mineral characterization was carried using X-ray powder diffraction (XRD), thermogravimetrical analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). X-ray fluorescence (XRF) studies were conducted to determine the chemical composition of the kaolin deposits. Kaolinite was the predominant mineral, followed by quartz, with traces of illite-muscovite, Fe-bearing minerals (hematite), anatase and feldspar. The average chemical composition of the kaolin samples was 58.02 wt.% SiO2, 28.00% Al2O3, 1.48% Fe2O3, 1.26% TiO2 and 0.41% K2O (ignited basis). Dehydroxylation and mullitization temperatures (from DTA) were close to the theoretical values. Hexagonal booklets and stacks of kaolinite, as well as individual platelets, were present in the Jabal Al-Harad kaolin. Based on granulometric and descriptive mineralogical analyses, the mineral assemblages and kaolinite morphology, the Jabal Al-Harad kaolin deposit is thought to have originated from greatly weathered surfaces related to the Precambrian basement rocks. The kaolin was found to be suitable for manufacturing of common bricks, medium-fired bricks and sanitary ware, although a beneficiation process would be required; it could also be used in the refractory, white cement, paper and advanced ceramic industries.

A new practical and precise method for determining soil aggregate stability is described. Four air-dry aggregate fractions (<0.25, 0.25–0.5, 0.5–1.0 and 1.0–2.0 mm) were added to thoroughly stirred water in a Mastersizer 2000 laser diffractometer. The suspension obtained was passed directly through the measuring system. The dynamics of median (equivalent diameter d50) particle-size distribution decrease (interpolated with a logarithmic function) was assumed to be the measure of soil aggregate stability. In order to show the applicability of the new method, the results obtained (for selected and diverse soils) were compared with those from the wet sieving standard method. The main conclusion is that the proposed method is convenient and can be successfully used for the estimation of soil aggregate stability. Moreover, it has wider application because standard sieving methods are restricted to aggregates >0.25 mm whereas, with the use of the laser diffraction method, smaller aggregates can be measured. The energy delivered to the aggregates in the process of aggregate disintegration is more reproducible in the method described here. The method also provides an opportunity to verify that the soil aggregates are completely destroyed (lack of the changes of the median value shows the end of soil aggregate disintegration).

Extensive drying of smectites can cause the interlayer space to break down (collapse). This can affect the properties of bentonites as geotechnical barriers of HLRW (highly radioactive waste) repositories. If and to what extent the collapse occurs depends strongly on the type of interlayer cation. In particular K is known to lead to ready dehydration, in contrast to Ca and Mg. In the present study, various bentonites and one illite/smectite clay were dried/heated at 90ºC for 1.5 a and in a different experiment at 120ºC for 4.5 a and investigated with respect to mineralogical and geochemical changes of the smectite.

Smectite alteration after extensive drying was restricted to changes of the exchangeable cations. The CEC decreased by 9% (90ºC test) and 14% (120ºC test). A slight decrease of exchangeable Na+ was observed following the 90ºC test. No significant further decrease was observed after the 120ºC test. In contrast, the larger cation exchange capacity (CEC) decrease after the 120ºC test could be explained by increased Ca/Mg fixation. A possible mechanism for the observations is presented.

The Loma Blanca mine is in one of the northwest kaolinized zones of the Los Menucos area (Patagonia, Argentina). The parent rocks are andesites and andesitic tuffs from the Vera Formation, Los Menucos Group (Lower Triassic). Hayase & Maiza (1974) proposed a concentric zonation model. From the parent rock outward, four different alteration patterns were recognized: Zone 1, with sericite, chlorite and montmorillonite; Zone 2, with kaolinite and dickite; Zone 3, with dickite, pyrophyllite and alunite; and Zone 4, with quartz, disseminated sulphides and diaspore.

The relationship between the chemical composition of major, minor and trace elements and the mineralogical alteration zonation was evaluated to confirm the genesis of the deposit. Fe2O3, CaO, Na2O and K2O contents decrease from Zone 1 to Zone 3, whereas Al2O3 and LOI increase in the kaolinite-alunite zone. In the chemical composition of alunite, Na > K. Large Ba, Sr, V and Zr contents were observed mainly in Zones 2 and 3. Co, Ni, Cu, Zn and Rb are more common in Zone 1. LREE are more abundant than HREE in Zones 2 and 3. In kaolinites, δ18O values range from 10.8% to 13.2%, and δD from –83% to –85%.

The mineral assemblage (dickite-alunite-pyrophyllite-diaspore), the alteration zonation pattern (laterally concentric), the geochemistry of trace elements, the relation between LREE and HREE and the small δ18O values suggest that the Loma Blanca deposit was formed by hydrothermal processes.

This study focuses on the main factors determining the apparent porosity of porous bioceramics prepared using small organic foam spheres as the pore-making reagent, in order to determine the best technical parameters for preparing porous bioceramics. In every experiment, only one of these factors (the time of heating, the sintering temperature, the mass ratio between small organic foam spheres and beta-tricalcium phosphate (β-TCP) powder, and the rate of the temperature rise) was changed, while the others were kept constant. In each case the apparent porosity was tested and the relation between the specific variable and apparent porosity was observed. Finally, the optimum technical parameters were deduced. The apparent porosity shows an inverse linear relation to the time of heating and the sintering temperature, and is approximately proportional to the mass ratio between the small organic foam spheres and the β-TCP powder and the rate of temperature rise. These factors have important influences on the apparent porosity. The optimum conditions were: heating time (soak time) 120 min, sintering temperature 850ºC, mass ratio 0.25, and a rate of temperature increase of 120ºC h–1.

The clay mineralogy and chemistry of a green lacustrine marl that has been pedogenically modified in the upper part was investigated in order to better understand the formation of low-temperature Fe-rich 10 Å clay. Twelve samples in a vertical sequence have been investigated using X-ray diffraction (XRD), chemical analysis, scanning electron microscopy (SEM) and laser particle size analysis. The clay assemblage has a range of overall illite-smectite (I-S) compositions (64–100%) resulting from several I-S phases that, for the sake of modelling, have been simplified to one to three I-S phases of increasing illitic content. Where the lacustrine marl has been pedogenically modified, the smectite-rich I-S is much reduced in abundance or absent and the 10 Å -rich component is both more abundant and more illitic. These assemblages are a consequence of illitization of detrital I-S in the lake and soil, and dissolution of other clays (kaolinite and chlorite) in the hypersaline lake. Interlayer K, octahedral Fe and octahedral + interlayer Mg increase with intensity of illitization (increase range 0.32–0.63, 0.68–1.67, 0.18–0.24 per O10(OH)2, respectively), first in the increasingly saline lake, and latterly as a result of wetting and drying in a gley soil. In the soil environment, reduction of Fe(III) to Fe(II) resulted in increased layer charge but, as by this stage very few smectite interlayers remained, this did not result in an equivalent increase in illite. Laser particle-size analysis, supported by SEM observation, shows the existence of a bimodal distribution of clay particle size (maxima at 0.2 and 1.5–1.8 μm) in which the finer fraction increases largely in the pedogenically affected samples, probably due to particle break-up caused by seasonal wetting and drying. This ‘dual action’ illitization, first in a hypersaline lake and latterly through wetting and drying, may be responsible for both the intensity of illitization and exceptionally high (for the Solent Group) Fe content of the authigenic illite. The chemical characteristics of the illitic I-S and the illite end-member correspond to glauconite. Hence, this is an example of onshore, non-pelletal glauconite formation.

A clayey soil from southern Tunisia has been studied in order to assess its possible use as an anti-pollution barrier. The soil has been characterized from both geotechnical and physicochemical points of view. The physicochemical characterization was carried out using X-ray diffraction, thermogravimetric and differential thermal analyses, specific surface area and cation exchange capacity measurements. Hydration tests were carried out using oedometers to determine the swelling behaviour of compacted specimens under different stress conditions. The large swelling pressure (420 kPa) is in agreement with the mainly smectitic character of the soil highlighted by the physicochemical tests. The changes in the fabric of the soil and in its porosity after the hydration tests were investigated using the same physicochemical methods, and related to the macroscopic hydro-mechanical properties. X-ray diffraction and mercury intrusion measurements show that there are changes in the interlayer spacing, particle size and inter-aggregate pore distribution. Comparing the properties of the soil with the Belgian guidelines for the construction of anti-pollution barriers showed that the material was suitable for that use.

In the oil fields in the Central Graben of the North Sea, Maastrichtian chalk is an important hydrocarbon reservoir, but oil may also be found in the Danian chalk, consisting of white chalk interbedded with clay layers. Within the chalk section, discrete intervals appear like chalk but contain large amounts of quartz (up to 100%). The aim of the present investigation is to reveal the mechanism for formation of the quartz in these intervals and to discuss their regional distribution and importance for the reservoir properties. Samples of chalk, including quartz-rich intervals, and clay layers from three wells SA-1, Rigs-1 and Rigs-2 in the South Arne Field have been investigated. Calcite-free residues obtained using a buffered dissolution of calcite were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. The main silica phase in the Upper Cretaceous–Danian chalk in the three wells is a nano-size α-quartz. This has probably formed from Si dissolved from radiolarians in the free-water phase. The 600 Å diameter α-quartz spheres precipitated in the free-water phase with subsequent flocculation of the spheres and sedimentation of the flocs. Variations in the proportion of quartz in the chalk are attributed to variations in the amount of radiolarians in combination with variations in CO2 concentrations in the water; increased CO2 causes dissolution of coccoliths and thus a relative enrichment in quartz. This formation mechanism is regional and makes it probable that the layers rich in nano-quartz may be found over large areas provided that the chalk is authigenic. Quartz-rich layers are generally of low permeability and in areas with authigenic chalk these layers may act as internal seals in chalk reservoirs.

The Aktoprak Basin, Turkey, provides important clues regarding regional palaeoclimatic changes which have not so far been elucidated. The purpose of the present study is to fill this gap using mineralogical, geochemical and isotopic characterization of cyclic sedimentation within Neogene sedimentary units. Early Miocene alluvial-fan to cyclic shallow-lacustrine sediments of the Aktoprak Basin consist of conglomerate, sandstone, mudstone, marl, limestone and palaeosol. The increasingly fine upward grain size and bed thicknesses suggest that the alluvial fan was fed by an ephemeral braided river. The cyclic sandflat–mudflat–shallow-lake succession is predominantly composed of small-scale sandstone-mudstone beds. Sandstone intervals in the sedimentary cycles are interpreted to be a result of sedimentation from shallow, ephemeral braided-river channels, the deposits having evolved under water-saturated conditions in response to climate changes. The mudstone intervals are interpreted as having been laid down via sedimentation during distal sheet floods which developed either under sub-aerial exposure or in a water-saturated environment. Palaeocurrent measurements indicate that the general transport direction in the Early Miocene was from east to west. The lacustrine sediments of the Aktoprak Basin consist of calcite + quartz + feldspar + serpentine coexisting mainly with smectite ± palygorskite ± illite ± chlorite. Illite and chlorite are either detrital, having originated from basement units, or the illite formed authigenically from smectite. Calcite and clay appear as cement-building conglomerate, sandstone and mudstone. The clay content decreases with increasing calcite and the presence of an inverse relationship between CaO and other oxides may correspond to an inverse relationship between calcite and other minerals. Furthermore, Al2O3, Fe2O3, TiO2, MgO, Ni, Co, Cu, Sr, Ba and Zr values in the smectite-bearing mudstone and sandstone are consistent with the chemical compositions of rocks in the surrounding area, mainly ophiolitic and volcanogenic associations. Micromorphologically, the development of smectite as a cement on leached feldspar, the occurrence of palygorskite fibres as bridges between crystals and rock fragments, as well as the presence of ‘edging’ smectite flakes suggest an authigenic origin. Field observations, mineralogy, geochemistry and the results of δ18O and δ13C isotopic determinations reveal that periodic palaeoclimatic changes were controlled by alternating wet and dry periods that resulted in a relative upward decrease in precipitation of authigenic smectite ± palygorskite within the sections, under the influence of geochemical and pH fluctuations in meteoric water within the shallow-lake environment.

In the western High Atlas basin, the evolution of the clay assemblage of the Upper Jurassic–Cretaceous sedimentary series is controlled by palaeogeographic changes of the basin and by burial diagenesis.The effects of burial are expressed by an increase in the proportions of illite and chlorite with depth, a decrease of expandability of smectite minerals and by a decrease in the Kübler Index.Kaolinite is preserved at greater depths than smectite, but also tends to diminish in abundance. TEM observations show that idiomorphic pseudo-hexagonal crystals of illite increase in size and abundance downwards, especially in the sandy levels.In the Agadir section, the main change in the clay mineral evolution related to late diagenesis occurs at the Mid-Albian, corresponding to a burial depth of about 1800 m; in the Essaouira section it occurs at the Lower Tithonian at a burial depth of about 2100 m.Considering the different geothermal gradient between Agadir (36ºC km–1) and Essaouira (27ºC km–1), the disappearance of smectite occurs at the same temperature in these two sites (60 to 65ºC).

The majority of investigations of soil electrical characteristics are concerned with tropical and subtropical regions and hence there is little information about soils from other regions. The present study attempts to discover the most important constituents affecting soil electrical charge characteristics in a temperate zone. The study area is located on southern coastal zones of the Caspian Sea in northern Iran (Guilan province). The soil moisture and temperature regimes of the region determined by means of Newhall software were udic and thermic, respectively. Six representative pedons developed on granite, andesite, basalt, phyllite and limestone as their parent rocks are described and their physicochemical, mineralogical and electrical properties studied. The results indicate that the point of zero charge (PZC) values are small in all samples and smaller at the surface than in subsurface horizons. There is a positive correlation between pH0 (PZC) values, organic carbon percentage and crystalline Fe (Fed) content. The points of zero net charge (ZPNC) values are <2.5 in all the pedons studied, which refers to large amounts of negative charge in these soils. The results also show that the differences in negative charge development in a pH range from 2.5 to 6 were largest for horizons rich in organic C and least for those with significant amounts of layer silicate minerals. Therefore, the most important variable charge component in all of the soils studied is organic matter which controls the negative charge at the soil surface. The permanent charge (бp) of the soils studied is also large and negative, which agrees with the amount of clay and the mineralogy of these soils.

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.