The influence of clay preparation procedure on sorption and hydrolysis of carbaryl (1-naphthyl, A-methyl carbamate) by the reference smectite SWy-2 was examined. For research purposes, reference clays are sometimes used without purification, or more commonly, the <2 μm size fraction is obtained by gravity sedimentation or low-speed centrifugation. We determined that these common methods did not remove all the inorganic carbonate impurities present in SWy-2, and that these impurities caused alkaline conditions in aqueous clay suspensions leading to the alkaline hydrolysis of carbaryl to 1-naphthol. The hydrolytic activity of homoionic K-SWy-2 disappeared once carbonates were eliminated. Two methods were evaluated for preparing K-SWy-2 devoid of inorganic carbonates. In Method A, inorganic carbonates were first removed by incremental additions of a 0.5 M sodium acetate buffer (pH 5.0) until the clay suspension reached pH 6.8, followed by low-speed centrifugation to obtain the <2 μm size fraction; in Method B, the order of these steps was reversed. Carbaryl hydrolysis was used as a probe to determine the effectiveness of the two methods in terms of the removal of carbonate accessory minerals. Homoionic K-SWy-2 obtained by Methods A and B produced near neutral pH when suspended in water and hydrolysis of carbaryl in these suspensions was not evident. In this regard, both clay preparation methods were acceptable. However, there were procedural advantages with Method B, which is therefore recommended for the partial purification of reference clays, as detailed in this paper.

Pyrophyllite is the precursor to other smectite-group minerals which exhibit swelling. The mineral structure of pyrophyllite can lead to other minerals in the smectite group, including montmorillonite, through appropriate isomorphous substitutions. In this work, an atomic model of the pyrophyllite interlayer was constructed. The response of the interlayer was evaluated using steered molecular dynamics simulations. In steered molecular dynamics, external forces were applied to individual atoms to study the response of the model to applied forces. In this work, forces are applied to the surface clay atoms to evaluate the displacement vs. applied stress in the interlayer between clay layers. This paper describes the construction of the model, the simulation procedure, and the results of the simulations which show that under the applied loading, deformation occurs mainly in the interlayer. The clay layers show relatively little deformation. The results show that the relationship between applied stress and displacement of the interlayer is linear. The stress-deformation relationship for the interlayer is presented.

The thermal stability of surfactant-modified clays plays a key role in the synthesis and processing of organoclay-based nanocomposites. Differential thermal analysis (DTA), thermogravimetric measurement and differential scanning calorimetry (DSC) were used in this study to characterize the thermal stability of hexadecyltrimethylammonium bromide-modified montmorillonites prepared at different surfactant concentrations. Analysis by DSC shows that the molecular environment of the surfactant within the montmorillonite galleries is different from that in the bulk state. The endothermic peak at 70–100°C in the DTA curves of the modified montmorillonites is attributed to both the surfactant phase transformation and the loss of free and interlayer water. With an increase of surfactant-packing density, the amount of water residing in the modified montmorillonite decreases gradually, reflecting the improvement of the hydrophobic property for the organoclay. However, the increase in the surfactant packing density within the galleries leads to a decrease in the thermal stability of the organoclays.

With an increase of initial surfactant concentration for the preparation of organoclays, the surfactant- packing density increases gradually to a ‘saturated’ state. It was found that the cationic surfactant was introduced into the montmorillonite interlayer not only by cation exchange but also by physical adsorption.

The crystal chemistry of Ti-rich trioctahedral micas of plutonic origin, cropping out at Black Hill (South Australia) has been investigated by combining electron microprobe analysis, single crystal X-ray diffraction, Mössbauer spectroscopy and X-ray photoelectron spectroscopy. Chemical analyses have shown the samples taken to be quite homogeneous and Ti-rich (TiO2 ≈ 7 wt.%). Mössbauer investigation yielded Fe2+/Fe3+ ≈ 30. X-ray photoelectron spectroscopy analysis seems to suggest the occurrence of three Ti species: octahedral Tr4+(60%), octahedral Ti3+(26%), and tetrahedral Ti4+(14%). The analyzed sample belongs to the 1M polytype and the relevant crystal data from structure analysis are: a = 5.347(1) Å, b = 9.261(2) Å, c = 10.195(2) Å, β = 100.29°(1). Anisotropic structure refinement was performed in space group C2/m, and converged at R = 2.62, Rw = 2.80. Structural details (the c cell parameter, the off-center shift of the M2 cation towards 04, the bond-length distortions of the cis-M2 octahedron, the interlayer sheet thickness, the projection of K−O4 distance along c*, the difference <K−O>outer-<K−O>inner) support the occurrence of the Ti-oxy substitution (VIR2+ + 2(OH)− ⇌ Ti4+ + 202− + H2) in the sample. Analysis of structural distortions as a function of the Ti content revealed that the positions of the oxygens 03 and 04 are displaced in opposite senses along [100]. This produces an enlargement of the M1 site with respect to the M2 site and a shortening of the interlayer distance. This trend seems to be in common with other Ti-rich 1M micas of plutonic origin.

Carbonate-intercalated layered double hydroxides of Co(II) and Ni(II) with Fe(III) and Al(III) were precipitated under different conditions (pH = 8–12; T= 25–80°C). All the samples are replete with stacking faults which are not eliminated by post-precipitation hydrothermal treatment (80–180°C, 18 h). DIFFaX simulations show that the layer stacking sequence of the disordered samples can be generated by a mixture of motifs corresponding to the 3R1 and 2H1 polytypes. These specific sequences are selected in preference to others because of the need for hydrogen bonding between the intercalated carbonates and hydroxide sheets. Thermodynamic considerations show that faulted crystals have greater stability than ordered crystals. Stacking faults arising from a mixture of 3R1 and 2H1 motifs, while having the same enthalpy as that of the ordered crystal, nevertheless contribute to thermodynamic stability by enhancing disorder.

Seven sedimentary bentonite deposits were investigated in the Miocene series of the Pannonian Basin. The following stratigraphic and genetic characteristics were significant: (1) all deposits were formed within a transgressive series of a given Miocene sequence; and (2) it is possible that the source material of the bentonites is rhyolitic, confirmed by radiometric data proving simultaneous rhyolite tuff volcanism.

A detailed investigation on three lithologically different bentonite horizons within the same transgressive series was made at Sajoábaábony to determine the source material and to determine the causes of the differences. X-ray diffraction, differential thermal analysis and geochemical data of the different lithological types show that they all have rhyolitic source material, although in the case of the lowermost horizon the existence of reworked material from an underlying andesite tuff series is also presumed. The main difference is the degree of weathering. Considering the ratio between the amorphous phase and the montmorillonite, the amorphous volcanic glass can be regarded as the main source of the montmorillonite formation. The differences in the degree of alteration can be related to the changing characteristics of the tuff accumulation and the sedimentation. Transgression decreases the sedimentation rate allowing the optimal alteration of the amorphous phase. The increasing intensity of the tuff accumulation can also limit the bentonite formation because rapid deposition and burial present too little time for the optimal alteration of the amorphous phase.

Summarizing the results from the stratigraphic interpretation of the bentonite deposits and from the comparative analyses of the different bentonite horizons within the same transgressive systems tract, we can state that the relationship of the tectonic-related tuff accumulation and the eustasy-related sedimentation rate can affect both the possibility of bentonite formation in macro-scale and the degree of bentonitization in micro-scale.

Iron-pillared clays (Fe-PILCs) were synthesized from hydrolyzed FeCl3 solutions added to NaOH solutions using different synthesis conditions. X-ray diffraction, N2 adsorption-desorption, chemical analysis, thermogravimetric analysis, differential thermal analysis, temperature-programmed desorption of ammonia and temperature-programmed reduction were used to characterize the resulting Fe-pillared clays (Fe-PILCs). A higher degree of pillaring was obtained when the Fe content was adjusted to 60 mmoles of Fe/g of clay. It was observed that higher values of this ratio led to worse acidity and textural characteristics, a consequence of the probable formation of Fe oxides that could not only deposit on the surface but also block the pores formed during the pillaring process. Likewise, it was found that the amount of Fe that can be introduced depended on the OH/Fe ratios. Total surface and micropore area decreased and Fe content increased with increasing pillaring solution concentrations. Finally, all pillared samples prepared here were thermally stable at temperatures up to 400°C.

To clarify the weathering process of volcanic glass to allophane, solid-state 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) signals of four Japanese volcanic glasses and two (Al- and Si-rich) allophanes were assigned. The volcanic glasses showed a broad 29Si NMR signal between −80 and −120 ppm with the peak centered at ~ −104 ppm, indicating that they were rich in Si-O-Si bridging structure (silica gel-like polymer Si). Aluminum was present in tetrahedral form in the four volcanic glass samples. In both Al- and Si-rich allophanes, octahedral Al (3 ppm by 27Al NMR) and imogolite-like Si (Q33VIAl, −78 ppm by 29Si NMR) were the major components. In a Si-rich allophane, NMR signals centered at around −85 ppm for 29Si and 55 ppm for 27Al were also observed, although it is possible that those signals were derived from impurities. Impurities could have originated from the soils and/or been unexpectedly synthesized during the purification procedures, e.g. during hot 2% Na2CO3 treatments. Based on the NMR spectra of size-fractionated soil samples, the weathering process of volcanic glass to allophane was proposed as follows: (1) dissolution of Al from volcanic glass accompanied by the transformation of IVAl to VIAl; (2) formation of a gibbsite-like sheet resulting from the hydrolysis of the dissolved Al; (3) dissolution of silica gel-like polymer Si in volcanic glass resulting in the formation of monosilicic acid; and (4) formation of Si(OH)(OVI,Al)3 structure (Q33VIAl) as a result of the reaction between the gibbsite-like sheet and the monosilicic acid. These formation reactions of allophane could occur in solution as well as on the surface of volcanic glass.

The island of Lipari (Italy) is characterized by calc-alkaline to potassic volcanism and a Mediterranean-type climate. The mineralogical and chemical features of two different soil profiles with ages of 92,000 and 10,000–40,000 y, respectively, have been investigated. There were no Andisols, but Vitric and Vertic Cambisols have developed at both sites. Although the morphology of the soils was similar, remarkable differences in the clay mineralogy between the two sites were observed. The site with the Vitric Cambisol was associated with the weathering sequence: glass → halloysite → kaolinite or interstratified kaolinite-2:1 clay minerals. Both sites had smectite in the clay fraction and, to a large extent, this smectite had a low charge and could be characterized as a dioctahedral montmorillonite. At the site with a Vertic Cambisol, smectite was the predominant mineral phase in the clay fraction. The smectites (predominantly montmorillonite) found in this soil were probably not of pedogenetic origin and are, therefore, inherited from the parent material. Their formation is due to hydrothermal alteration of glass particles during or immediately after the emplacement of the pyroclastic flow. The octahedral character of the smectites did not change from the C to the A horizon indicating that they are resistant to weathering processes. A high-charge expandable mineral was detected in small concentrations in the Vertic Cambisol and had a dioctahedral structure. In this case also, no signs of significant weathering or transformation could be detected in the soil profile. In contrast to many other investigations, no active smectite formation within the soil profiles could be measured. The subtropical and rather dry climate in Lipari might, therefore, favor the persistence of dioctahedral low-charge montmorillonites that are associated with a small amount of a high-charge expandable mineral in the soil.

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 transformation process between palygorskite and smectite was studied by examining the morphological and structural relationships between these two minerals in an assemblage from the Meigs Member of the Hawthorne Formation, southern Georgia. Studied samples were related to an alteration horizon with a tan clay unit above and a blue clay unit below. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to study the mechanism of transformation.

From AFM data, both clay units contain euhedral palygorskite fibers. Many fibers are found as parallel intergrowths joined along the [010] direction to form ‘raft-like’ bundles. Degraded fibers, which are common in the tan clay, have a distinctly segmented morphology, suggesting a dissolution texture. Many of the altered palygorskite fibers in the tan clay exhibit an oriented overgrowth of another mineral phase, presumably smectite, displaying a platy morphology. This latter mineral forms along the length of the palygorskite crystals with an interface parallel to {010} of the palygorskite. The resulting grain structures have an elongate ‘wing-like’ morphology.

Imaging by TEM of tan clay material shows smectite lattice-fringe lines intergrown with 2:1 layer ribbon modules (polysomes) of the palygorskite. These features indicate an epitaxial overgrowth of smectite on palygorskite and illustrate the structural relationship between platy overgrowths on fibers observed in AFM data. The epitaxial relationship is described as {010} [001] palygorskite ‖ {010} [001] smectite.

Energy dispersive spectroscopy indicates that the smectite is ferrian montmorillonite. Polysomes of palygorskite fibers involved in these textures commonly vary and polysome widths are consistent with double tetrahedral chains (10.4 Å), triple tetrahedral chains (14.8 Å), quadruple tetrahedral chains (21.7 Å) and quintuple tetrahedral chains (24.5 Å).

The transformation of palygorskite to smectite and the resulting intergrowths will cause variations in bulk physical properties of palygorskite-rich clays. The observation of this transformation in natural samples suggests that this transformation mechanism may be responsible for the lower abundance of palygorskite in Mesozoic and older sediments.

MgO-clay nanocomposites were prepared from a synthetic smectite-type clay, TS, using three different non-ionic surfactants (Igepal CA-720, Brij 30 and Brij 56) and the resulting clay nanocomposites were impregnated with Ni for the methane reforming reaction with carbon dioxide to synthesis gas. A Ni/TS catalyst was also prepared for comparison. The prepared supports and catalysts were characterized by X-ray diffraction, X-ray fluorescence, thermogravimetric analysis and N2 adsorption/desorption isotherms. The thermal stability, pore structure and the surface area strongly influence the catalytic behavior of the catalysts. The methane conversions (at 700°C for 4 h) were 91, 95 and 97% for Ni/TSIGE, Ni/TSBR30 and Ni/TSBR56, respectively, indicating that the surface properties and the catalytic performance of the resulting solids slightly improved as the polyethylene oxide number of the surfactant increased. A reduced conversion (10%) and a rapid deactivation was observed in the Ni/TS catalyst, attributed to its Na content and low thermal stability, which led to sintering and coke deposition.

Reaction of a Mg-Al carbonate layered double hydroxide (LDH) with boric acid leads to a borate-pillared LDH with the stoichiometry [Mg0.65Al0.35(OH)2][B3O5]0.35.0.65H2O and an interlayer spacing of 1.07 nm. Infrared and 11B magic angle spinning nuclear magnetic resonance data are consistent with the presence of polymeric triborate anions of the type [B3O4(OH)2]nn- in the interlayer galleries so that the material can be formulated as [Mg0.65Al0.35(OH)2][B3O4(OH)2]0.35.0.30H2O. The flame-retardant properties of the borate-pillared material and the carbonate precursor in composites with ethylene vinyl acetate copolymer were compared. Introduction of the borate anion leads to a significant enhancement in smoke suppression during combustion without compromising the flammability of the material. This is related to the synergistic effect between the host layers of the LDH and the borate anions uniformly distributed in the interlayer region.

The structure of dioctahedral true micas such as muscovite and celadonitic muscovite (2M1 polytype, space group C2/c) is mostly affected by variations of the octahedral Al (VIAl) content. Crystals with greater Mg, Fe substitutions (i.e. celadonitic muscovite) reduce the dimensional difference between the larger trans-oriented M1 site and smaller cis-oriented M2 octahedral site. The octahedral anionic position O4 is displaced from the center of the hexagon, defined by 031 and 032 oxygen atoms (i.e. ‘octahedral hexagon’), both on and off the (001) plane. The distance between interlayer cation A and O4 is smaller in more substituted species, thus providing different orientations of the O4−H vector, as a function of VIAl. Octahedral distances (<M2−O3> and <M2−O4> are expressed as a function of cell parameters and VIA1 content, thus allowing an approximate estimate of site dimensions. These approximations are useful when a detailed structural refinement is not available. In celadonitic muscovite, the octahedral hexagon mean edge (<O31−O32>Hex) is not significantly affected by VIA1 content. The VIA1 increase produces both a decrease in cell lateral dimensions and a distorted ‘octahedral hexagon’. The decrease in a and b is consistent with a decrease of <O31−O32>Hex, whereas the distortion of the’ octahedral hexagon’ is consistent with an increase of (<031–032>Hex), because an irregular hexagon produces a longer mean edge than a regular hexagon of equal area.

The tetrahedral mean basal edge (VI<O−O>bassal) is reduced as celadonitic substitution progresses. The tetrahedral rotation angle, α was thus found to increase from celadonite to muscovite. However, in muscovite with VIAl content between 1.8 and 2.0 atoms per formula unit (a.p.f.u.), α approaches a saturation value, thus showing a proportional increase of tetrahedral and octahedral sheet lateral dimensions. Furthermore, α variation allows a coarse approximation of the threshold VIAl content, below which celadonitic substitution may not progress.

Calcium-sodium exchange on Wyoming bentonite in methanol, ethanol and acetone-water systems were investigated at 0.03 N Cl and at room temperature. Calcium-sodium exchange isotherms were plotted at cosolvent concentrations ranging from 0 to 70% wt./wt. using Ca and Na ionic activities before and after correction for CaCl+ formation. In both cases and in all treatments, a greater selectivity of bentonite surfaces for Ca ions was observed. When compared to water, different trends were observed among and within cosolvents. These trends varied depending on whether or not CaCl+ formation was accounted for. Ignoring the formation of CaCl+, the preference of bentonite for Ca increased in methanolwater systems with increased percent methanol at low equivalent Ca fraction (<0.2). At higher Ca fractions, this preference matched that of water. In ethanol-water, no increased preference of the surface for Ca was observed. In acetone-water, increasing cosolvent concentration decreased the preference of the surface for Ca. The magnitude of this decrease was larger at low equivalent Ca fraction (<0.2). After correction for CaCl+, both in solution and on the surface, the preference of bentonite for Ca2+ was larger in methanol- and ethanol-water systems. In acetone-water, increased surface preference for Ca was only apparent at low acetone fractions (<50%). At higher acetone fractions, there was evidence of increased Na loading but no increase in Ca2+ selectivity. Clearly, ion-pair formation and its effects on Ca-Na exchange reactions cannot be ignored in mixtures of aqueous-organic solvents. After accounting for this effect, Ca-Na exchange in the studied solvents appears to be more of a surface- than a solution-controlled phenomenon that involves both electrostatic and specific solvent-surface types of interactions that have not been elucidated.

A pseudomorphous aggregate after titanite composed of smectite, anatase and residual titanite of composition (Ca0.98,Mn0.02)(Ti0.65,Al0.35)[SiO4](O0.65,OH0.35), from a depth of 450 m in the Broken Hill South Mine, New South Wales, Australia, was investigated by electron microscopy and microanalysis to characterize the alteration products and the mobility of Ti. Examination of the pseudomorph showed randomly oriented anatase crystals dispersed throughout a matrix of beidellite, with 9% porosity. Around the periphery and along the (110) cleavage plane of titanite, alteration was most developed. The range of Ti mobility was found to be limited to ~500 nm, and the ratio between the average diameter of anatase crystals and the average distance between them is ≈1.3. This ratio is consistent with an alteration process in which Ti is conserved and the anatase crystals grow from the Ti available immediately around them. It is unlikely that Ti migrated beyond the titanite pseudomorph.

In this study a robust design method is developed for extracting Li from boron (B) clays with the aim of minimizing cost and maximizing productivity. Lithium is commercially extracted from brines and certain minerals. Its extraction from clays has previously been found to be expensive, a major part of the extraction cost being attributed to the raw materials used. In this study, raw materials from lower-cost resources are used without applying any standardization to them and this might increase variation in the results. To minimize the variation, and achieve high extraction levels, robust design, statistical design and analysis of experiments, and response surface methodologies are utilized. As a result, consistently higher extraction levels have been achieved compared to previous studies. The experiments were conducted using the Bigadiç boron clay fields in Turkey. However, the method is generally applicable to other cases also.

Study of the transformation of smectite to illite, chlorite or vermiculite via interstratified clay minerals needs precise qualitative and quantitative determinations of the different layers in the mixed-layer clays and is generally based on X-ray diffraction (XRD) patterns after specific treatments of the clay samples. Saturation with K or Mg followed by ethylene glycol (EG) solvation are classical methods used to identify high-charge smectite and vermiculite. These procedures have been applied to two experimental clays, one composed of smectite layers and the second, a mixture of vermiculite and smectite layers. Different methods of glycolation (EG vapor or liquid EG) produce significant differences in the XRD patterns. Comparison with literature data indicates that K-saturated, high-charge smectite (≈0.8 < total charge <1/unit-cell) and Mg-vermiculite (whatever its charge) do not expand in ethylene glycol vapor (d values ≈14–15 Å). Expansion to 17 Å in liquid ethylene glycol occurs for Mg-vermiculite with a total charge of <~1.2/unit-cell and for K-saturated, high-charge smectite, when the tetrahedral charge is <≈0.7/unit-cell. This study shows that: (1) glycolation procedures need to be standardized; (2) the use of saturation protocols using both liquid ethylene glycol and ethylene glycol vapor yields useful additional information about the distribution of charges in clay minerals.