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Cenozoic basin sediments on the Tibetan Plateau are commonly characterized by frequent changes in sediment facies and coarse lithologies, which largely limits our understanding of the relationship between the Tibetan Plateau uplift and its environmental impacts. The monomineral index derived from those sediments can effectively eliminate the effects of grain size and sedimentary facies changes. Here, we present detailed mineralogical, spectroscopic, and micromorphological investigations of smectites collected from the Hongliugou section of the Qaidam Basin to explore the relationship between climate change and the Tibetan Plateau uplift in the early–middle Eocene. Multiple methods involving X–ray diffraction, transmission electron microscopy, 27Al nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy collectively show that the smectites in the Hongliugou section are mixtures of montmorillonites and beidellites. The origin of the beidellites was likely the weathering product of illite, as indicated by the presence of illite–beidellite mixed layers (an intermediate product of the alteration of illite to beidellite). The long–term decreasing trend of beidellite/smectite ratios from the highest values (∼1.1–82.0%, averaging 14.8%) in the Early Eocene Climate Optimum (∼52.0–49.5 Ma) to generally <2% at 49.5–43.9 Ma suggested a long–term climatic drying. This climate change history deduced from the variation of beidellite content is consistent with other climate records and supports that global climate change was the driving factor regulating regional climate change. Our study thus suggests that the monomineral index of smectite may serve as an effective method for reconstructing regional climate change, especially within complex sedimentary environments. • Both beidellite and montmorillonite were identified in the Qaidam Basin. • A continuous drying trend is shown by the beidellite content at ∼53–43.9 Ma. • Global climate change mainly regulated regional climate change during ∼53–43.9 Ma. • Smectite monomineral index reveals climate change in complex sedimentary settings. [ABSTRACT FROM AUTHOR]

Three glycoside hydrolases (α-amylase, xylanase and pullulanase) were immobilized on low-cost, environmentally friendly, easily modified clay rich in beidellite. Modifications included common procedures: Na-exchange, acid activation, pillaring, pillaring followed by acid activation, and organo-modifications with chitosan. Supports were characterized by chemical analysis, low temperature N 2 physisorption, X-ray powder diffraction (XRPD) and Fourier-transform infrared (FT-IR) spectroscopy. The point of zero charge was also determined. Specific activity of different immobilizates of selected glycoside hydrolases was notably influenced by the type of chemical modification of supports. For each enzyme optimal support was chosen and storage stability was tested. α-Amylase immobilized on acid-activated support retained up to 95% of its initial specific activity of 105.6 ± 5.1 U g−1 after a testing period of 120 days. The most suitable support for xylanase was chitosan-modified beidellite with having specific activity of 90.0 ± 1.4 U g−1 which retained >50% its value after 120 days. Specific activity of pullulanase immobilized on pillared sample that was subsequently activated by acid was 44.5 ± 0.7 U g−1. Initial activity was preserved up to 33% for the same testing period. Comparing these results to the storage stability of the free enzymes that completely lost their activity for the longest period of 40 days, it can be concluded that appropriately modified beidellite- based clays could be used as suitable supports for stabilization of glycoside hydrolases. Nevertheless, further characterization of immobilizates (pH, thermal and operational stability) is needed in order to raise the suitability for larger scale processes in food industry. [Display omitted] • α-Amylase, xylanase and pullulanase were immobilized onto modified clay rich in beidellite. • Acid-activated beidellite based support was optimal for immobilization of α-amylase. • Xylanase exhibited the best performance immobilized on chitosan-beidellite organoclay. • Optimal modification for pullulanase was Al,Fe pillared clay followed by acid activation. • The immobilization onto optimal supports significantly improved storage stability of enzymes. [ABSTRACT FROM AUTHOR]

[Display omitted] • DGE-modified clay (DGE-BDT) was prepared using a simple process. • The corrosion inhibition efficiency of 1 g/L DGE-BDT is approximately 82 % for 48 h. • DGE-BDT was incorporated into an alkyd resin (5%) to develop a modified protective coating on mild steel. • The paint system (AR-DGE-BDT) improves the anti-corrosion properties and maintains the long-term inhibiting effect. The development of eco-efficient and environmentally friendly active anticorrosion coatings for metal substrates represents a fundamental step in many engineering applications. In this work, a novel corrosion inhibitor was elaborated beidellite clay (Na-BDT) and an aqueous extract of Daphne Gnidium (DGE). The modification of the clay by DGE was monitored and characterized using cyclic voltammetry (CV), X-ray diffraction (XRD), UV/visible spectroscopy (UV/Vis), and Fourier transform infrared spectroscopy (FT-IR) techniques. The results showed that the clay modification was successfully achieved, with a DGE adsorbed amount of approximately 99 mg/g. Mild steel is effectively protected against corrosion in 0.1 M NaCl solution thanks to the progressive release of DGE, resulting in the lowest corrosion current density (7.22 µA/cm2) and the highest charge transfer resistance (7.20 kΩ.cm2) after 48 h of immersion. The calculated inhibition efficiency reaches a maximum of approximately 83 %. DGE-modified clay (DGE-BDT) was then dispersed into an alkyd resin (5 wt%) to enhance the corrosion protection of mild steel. The anti-corrosion performance was maintained over a long period of time and remains higher than that of the coating containing a commercial triphosphate aluminum (TPA) corrosion inhibitor. This study demonstrates the potential of encapsulating natural extracts as an eco-friendly corrosion inhibitor with high performance capabilities. [ABSTRACT FROM AUTHOR]

Abstract Chitosan (CS) and purified sodium beidellite (Na-Bd) were used to obtain a nanocomposite able to carry anionic pharmaceutical ingredients. Diclofenac sodium (DS) was chosen as a model drug and was loaded by intercalation solution technique. Solid state characterization of the resultant hybrids was performed, including X-ray diffraction, Fourier transformed infrared spectroscopy, Thermal analysis and high resolution transmission electron microscopy coupled with energy dispersive X-Ray analysis. Drug loading capacity and encapsulation efficiency were quantified by measuring equilibrium concentration by UV–Vis spectroscopy at 276 nm. Solid-state characterization of the samples confirmed both chemical and physical interaction of DS with the nanocomposites. High drug loading along with a modified cumulative release of the drug in simulated intestinal fluid was obtained. The developed clay/polymer hybrids can act as potential candidates for the design of modified dosage forms of anionic drugs. Highlights • Chitosan/sodium-beidellite nanocomposite was prepared. • Diclofenac sodium was successfully loaded. • A partial exfoliation of the clay has been detected. • Significant drug encapsulation efficiency was found. • The release of Diclofenac was modified in comparison with the pure drug. [ABSTRACT FROM AUTHOR]

The study aims to combine between the valorization of the adsorption ability of the clay mineral and essential oil with insecticidal effect for synthesis of a powder formulation investigated as natural insecticide. The insecticidal formulation created by the adsorption of the terpenes from Eucalyptus globulus essential oil onto the Tunisian clay classed beidellite (Bd). Furthermore, modified beidellite was investigated for increasing the amount of terpenes adsorbed. Organoclays (OC) were prepared by hexadecyltrimethyl ammonium (HDTMA) and didodecyldimethyl ammonium bromide (DDDMA) intercalation in the interlayer space of Bd. The OC was characterized by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) analysis and Textural analysis by nitrogen adsorption desorption (BET method) in order to confirm the success of organic modification. After adsorption studies, the kinetic models are examined. Results show the adsorption of terpenes onto Bd and modified Bd flows the pseudo-second-order model. Moreover, the adsorption ability of terpenes from Eucalyptus globulus oil is enhanced after organic modification, especially HDTMA. [ABSTRACT FROM AUTHOR]

The Eocene subaqueous volcanic units in NE Turkey developed as pillow, closely packed pillow, isolated pillow, pillow breccia, hyaloclastite breccia and rare peperitic facies with red micritic limestones. They are locally set on volcaniclastic sandstone and claystone alternations and gradually pass to tuffs and volcanic breccias. The pillow lava samples generally exhibit intersertal, intergranular, microlitic porphyritic, variolitic, vesicular and glomeroporphyritic and glassy textures with clinopyroxene (Wo 47-52 En 40-45 Fs 6-8 ), plagioclase (An 10 to An 96 ), olivine (Fo 79-87 ) and Fe-Ti oxides (Usp 0-0.27 ). Saponite, interlayered chlorite/saponite, rare beidellite and calcite were determined after olivine, rarely after plagioclase as well as in the glassy groundmass. Illite was restricted to plagioclase and the glassy groundmass. Na-Ca zeolites, chlorites/saponites, beidellite, dolomite and calcite occur as void infillings and in the glassy groundmass. Mineralogical, lithochemical and isotopic interpretations as well as thermometric calculations reveal a low-temperature seawater alteration in a semi-closed environment for the alteration of primary minerals and volcanic glass in addition to sealed vesicles and open systems for crosscutting veins. Due to the short exposure time intervals of seawater to rocks, the total chemistry of the rocks is not fully changed and most of the elements seem to be immobile, remaining in the system as a result of precipitation in voids and cracks. Thermometric estimations indicate that, the temperature of heated seawater is approximately 160 °C at the highest point especially in the vesicles, and decreases to approximately 85 °C due to circulation, resulting in alterations of the primary phases and volcanic glass. [ABSTRACT FROM AUTHOR]

The photoactive azobenzenes were intercalated into montmorillonite and beidellite in order to obtain a functional material responsive to UV radiation. The smectite modification involved two steps: (1) intercalation with alkylammonium salts, differing in alkyl chain length, and (2) co-intercalation with azobenzene or aminoazobenzene. The structure and chemistry of the obtained materials were thoroughly characterize with the means of XRD, FTIR, DTA/TG, UV–Vis methods and CHN elemental analysis. The mechanisms interpretation was supported with the molecular dynamics simulations. Photoresponse of the obtained materials was monitored through the observation of the basal spacing shifts upon UV radiation. The results proved that both the type of alkylammonium salt and the host mineral influenced heavily the efficiency of subsequent azobenzene intercalation as well as its photoactive behaviour. The evident and regular photoinduced basal spacing shifts were visible when the density of intercalated salts was low. This was achieved in the BId derivatives due to the low layer charge of the mineral. Also the shorter alkyl chain of the co-intercalated salt promoted larger photoresponses. [ABSTRACT FROM AUTHOR]

The presence of swelling clay minerals, such as smectites, is known to be one of the main parameters controlling the mobility of radium in natural environments due to the high adsorption capacities of these materials. However, experimental data and modeling from literature allowing to investigate the adsorption properties of radium towards smectite in a wide range of acidic conditions (2 < 7) are scarce. Moreover, the role of the smectite crystal chemistry (charge location in the layer) remains unclear. Therefore, experimental data for the adsorption of radium onto a swelling clay mineral with a tetrahedral charge (beidellite) are presented here in the 2–7 pH range. Different batch experiments were conducted in order to investigate the effects of both ionic strength (i.e., from 0.027 to 0.11 M in sodium chloride medium) and presence of competing major cations (i.e., magnesium). Experimental data were interpreted using a multi-site ion-exchange model that takes into account the adsorption of major cations (including H + ), which usually compete with trace elements for sorption onto mineral surfaces in natural environments. The ability of the proposed model to predict experimental distribution coefficient (K d ) values under various conditions of ionic strength and aqueous cation compositions was tested, and results were compared with those obtained using previously published models. The evolution of radium adsorption on beidellite with pH variation is better reproduced by using a multi-site ion-exchange model, as proposed in this study, than by using a single-site model as that reported in literature. Finally, the implication of the results obtained in this study for the mobility of radium in natural environments was discussed. The significant role of smectites in the adsorption of radium at low pH conditions (pH ≤ 6) in complex mixtures, which are representative of natural matrices, was demonstrated based on comparison with experimental data previously obtained on organic material and Fe(III)-oxy/hydroxides. The multi-site model proposed in this study for beidellite, coupled with a model from literature for organic matter, was applied in order to predict the role played by the beidellite in the adsorption properties of a virtual complex mixture containing various proportions of beidellite and organic matter. The model shows that smectite can contribute from 80 to 100% to the total adsorption of radium of the complex mixture for pH < 3. Moreover, the predicted results were in good agreement with experimental data from literature obtained with natural peat. Finally, the multi-site ion-exchange model proposed in this study for beidellite could be applied in many natural environments characterized by acidic pH, such as naturally acidic soils (pH ≤ 5) and acid mining environments (pH ≤ 1), where predicting 226 Ra exchange onto swelling clay minerals requires accounting for the effects of the major cations present in these systems. [ABSTRACT FROM AUTHOR]

Swelling pressure of dioctahedral smectites in the montmorillonite – beidellite series was investigated by molecular dynamics simulations. The pressure was found to correlate inversely with the magnitude of the layer charge in the range of −0.5 to −1.0 per unit cell. The beidellite type smectites were found to have lower swelling pressure than the montmorillonite type smectites. A clear effect of the type of interlayer cations on the swelling pressure was found. The sodium smectites sustained significant pressure even at longer interlayer distances, while in calcium smectites the pressure decreased soon after the initial swelling. The simulation results are in good agreement with experimental observations and provide a tool for predicting macroscopic swelling behavior in smectites. [ABSTRACT FROM AUTHOR]

The dissolution rate of beidellite, a dioctahedral smectite with tetrahedral charge that is a common swelling clay mineral in surface and subsurface natural environments, was studied in acidic solutions at 25 °C under far from equilibrium conditions. A <0.3 μm size fraction of SBId1 beidellite ((Si 7.148 Al 0.852 )(Al 3.624 Mg 0.18 Fe(III) 0.224 )O 20 (OH) 4 M + 0.948 ) purchased from the Clay Mineral Society was used as the starting material, and experiments were performed in stirred flow-through reactors using HCl solutions with pH values ranging from 1 to 3. Several hydrodynamic conditions were tested using different flow rates with stirred and non-stirred particles. The aqueous Al/Si ratio measured at the outlet of the reactor was followed as a function of time and compared to solid stoichiometry values to assess the mechanisms occurring at the solid/solution interface. The reversible adsorption of Al 3+ in the smectite interlayer space was evidenced for pH > 1.1, and the presence of an amorphous Si-enriched layer can be reasonably assumed in some cases from the interpretation of the aqueous concentrations and the characterization of the solid phase (X-ray diffraction and FTIR spectroscopy). Beidellite dissolution rates normalized to the sample mass (mol g −1 s −1 ) were obtained from Si and Al concentrations under steady state dissolution conditions. Calculated rates were compared with those previously reported for montmorillonite in several publications. The beidellite dissolution rates are, on average, ten times lower than those of montmorillonite. This implies that the smectite crystal chemistry (i.e., amount of Al 3+ versus Mg 2+ or Fe 3+ substitution in the structure) has a strong effect on its stability and should be considered in reactive transport models in which the dissolution properties of smectites are taken into account. [ABSTRACT FROM AUTHOR]

Five-membered cyclic organic carbonates (COC) are of interest for their ability to modify the surface properties of smectites and enhance the hydraulic resistance of bentonites to saline leachates. The mechanism of interaction of glycerol carbonate (GC) and several other hydroxyl containing cyclic organic carbonates (generally having progressively greater molecular masses) with sodium montmorillonite (Na + -Mt) was studied using powder X-ray diffraction and infrared spectroscopy. The 001 reflection for GC/Na + -Mt intercalates varied with the amount COC added, and the measured d 001 value increased from 1.29 nm to as large as 2.22 nm at equal-mass coverage of the COC to Na + -Mt. In general, when intercalated, the cyclic carbonyl (C O) stretch and the fundamental hydroxyl (O–H) stretch bands of COC derivatives were red-shifted with respect to these bands for neat COC, indicating strong ion-dipole interaction of the carbonyl group with interlayer Na + , and H-bonding of the OH group with both interlayer water and Mt surfaces. A stable and highly ordered intercalate was produced at a 1:1 mass loading with Mt in which about 6 GC molecules per unit cell (~ 7 molecules per Na + ion) replaced most of the interlayer water. [ABSTRACT FROM AUTHOR]

The adsorption technique is widely applied for the removal of pollutants from wastewater, especially for toxic or non-biodegradable wastewater. In recent years, the production of alternative adsorbents to replace costly adsorbents has been paid more attention to in literature. Polyaniline/beidellite (PAn + Bei) composite material as an absorbent, which is efficient and low cost can easily be prepared via H 2 SO 4 , KIO 3 and aniline. This paper deals with color and total organic carbon (TOC) removal of biologically treated bakery yeast wastewater (BYW) using the PAn + Bei composite material by adsorption processes. The effects of experimental variables were chosen as the initial pH (pH i ), sorbent dosage ( m s ), contact time ( t c ) and mixing speed ( s ) by a batch sorption process. It was found that by increasing the adsorbent dosage (0.025–0.400 g/50 ml of composite dosage), contact time (2–240 min) and decreasing the pH i (9–3) improved the color and TOC removal efficiencies. The optimum color and TOC removal efficiencies were obtained as 88.7% and 63.3% at 0.400 g/50 ml of adsorbent dosage, a pH i of 3, 240 rpm, and 240 min. In addition, a pseudo-second order kinetic model was proposed to correlate the experimental data. To understand the removal mechanism and characterize the surface of the PAn + Bei composite material, size exclusion chromatography (SEC), BET surface analysis, fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscope (SEM), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) were employed. As a consequence, the proposed mechanism for the removal by PAn+Bei composite material seems to be driven by an ion exchange process. [ABSTRACT FROM AUTHOR]

The fixation of the hexavalent chromium (CrVI), a toxic component in the wastewater, from the aqueous solutions into the interlayer space of beidellite (Bd) clay was studied, combining theoretical and experimental methods. The structure of intercalated CrVI anionic species to beidellite modified by tetrahexylphosphonium cation (Cr-THP-Bd) was examined using the density functional theory (DFT) calculations on representative structural models. The computed basal spacing (d 001) of the Cr-THP-Bd model (15.5 Å) showed a good agreement with the experimental value (15.3 Å) obtained by the XRD method. Calculated intercalation energy of −214.2 kJ/mol demonstrated strong stabilization of chromate anion in the THP-Bd structure. C–H⋅⋅⋅O and O–H⋅⋅⋅O hydrogen bond interactions present in the Cr-THP-Bd model significantly affected the structural stability of the whole studied system. The calculated vibrational spectra from the ab initio molecular dynamics (AIMD) helped identify the Cr–O stretching and O–Cr–O bending vibrational modes of (CrO 4)2− anion in the complex FTIR spectra. The amount of (CrO 4)2− anion determined by the experiment clearly confirmed that Bd modified by the THP surfactant significantly increased the adsorption of the chromate anion in comparison to pure Na-Bd clay. [Display omitted] • Adsorption of hexavalent chromium anion onto organically-modified beidellite clay. • Quantum chemical calculations helped to explain origin of (CrO 4)2− adsorption. • Electrostatic and hydrogen bond interactions are responsible for adsorption. • FTIR spectrum of (CrO 4)2− anion was interpreted by vibrational density of states. • Clay modification by organic cation enhanced adsorption of (CrO 4)2−. [ABSTRACT FROM AUTHOR]

We report an FPMD (first-principles molecular dynamics) study of the interfacial structures and acidity constants of the edge surfaces of ferruginous smectites. To understand the effects of Fe oxidation states on the interfacial properties, we investigated both the oxidized and reduced states of the (0 1 0)-type edges of two clay models with different Fe contents. The coordination states of edge Fe atoms are determined from the free energy curves for the desorption of the H 2 O ligands. The results of both clay models show that for Fe(III), only the 6-coordinate states are stable, whereas for Fe(II), both the 6- and 5-coordinate states are stable. Using the FPMD-based vertical energy gap technique, the p K a values of the edge sites are evaluated for both oxidation states. The results indicate that for both clay models, both the octahedral and tetrahedral sites become much less acidic upon Fe reduction. Therefore, the comparison reveals that the interfacial structures and protonation states are strongly dependent on the Fe oxidation states. Using the calculated results, we have derived the pH-dependent surface complexing mechanisms of ferruginous smectites. [ABSTRACT FROM AUTHOR]

This study aims at determining suitable conditions for the preparation of the best organobeidellite starting material used for the development of efficient mesoporous TiO 2 supported beidellite (Bd) photocatalysts. For this purpose, organo-modifications of natural Bd from Agadir Basin (Morocco) were achieved. The influence of (i) the length of alkyl chains C n (n = 8, 12, 14 and 16) of n-alkyl ammonium surfactants CH 3 (CH 2 ) n-1 NH 3 + and (ii) the amount of C 16 surfactant ranging from 1 to 5 times the smectite (Sm) cation exchange capacity (CEC) on the structure of organo- Bd was studied. XRD, TEM, TG-DTA and FTIR results are consistent with the intercalation of cationic surfactants species in Bd interlayer spaces according to different conformations yielding to their expansion. The interlayer expansion magnitude increased both with the length of alkyl chain and the amount of C 16 surfactant. Organomodification with increasing surfactant load beyond 1CEC besides yielded to the adsorption of increasing excess on external surfaces of Bd particles. These controlled structural modifications will be used further in the functionalization of this Bd by TiO 2 nanoparticles to produce efficient supported TiO 2 -Bd photocatalysts. [ABSTRACT FROM AUTHOR]

This work deals with the study of the effect of the amount of cethyltrimethylammonium bromide (CTAB) surfactant, used in the preparation of starting organobeidellites, on physico-chemical properties and photocatalytic activity of TiO 2 supported beidellite (Bd) nanocomposites against the removal of Orange G (OG) dye from aqueous media. A structural study of organobeidellites used as starting materials was reported in a companion paper. Here, physico-chemical characterizations of the nanocomposite photocatalysts show that TiO 2 supported on Bd beforehand organomodified with an amount of CTAB equivalent to 3 CEC of smectite (3CTA + –Bd) exhibits thin fine grained (≈ 10 nm) features which remarkably remained stable in the form of photoactive anatase up to 750 °C. Comparatively, the TiO 2 coating grown on Bd previously rendered organophilic by using an amount of CTAB equivalent to 5 CEC of Clay mineral (5CTA + –Bd) appears thicker and more porous with larger nanoparticles (≈ 25 nm) which is prone to be readily converted into less photoactive rutile as observed near 700 °C. This is likely due to its development mainly outside Bd interlayer spaces promoted by outer organophilic environment created by the adsorption of CTA + excess. In both cases, anatase is still present as minor phase up to 900 °C. As a result of these differences a significant improvement of the photocatalytic activity of TiO 2 supported Bd nanocomposite prepared starting from 3CTA + –Bd is observed compared to that from 5CTA + –Bd. For instance, the total elimination of the pollutant from the aqueous solution occurs within about 45 min when using the 3CTA + –Bd–TiO 2 photocatalyst instead of 90 min using the 5CTA + –Bd–TiO 2 sample. Furthermore, the best TiO 2 –Bd supported photocatalyst is also found more efficient than a pure TiO 2 xerogel sample. [ABSTRACT FROM AUTHOR]

To our knowledge, no thermodynamic database is available in the literature concerning ion-exchange reactions occurring in low-charge smectite with tetrahedral charge (beidellite). The lack of this information makes it difficult to predict the mobility of contaminants in environments where beidellite and major cations, which act as competitors with contaminants for sorption on the clay phase, are present. The present study proposes a multi-site ion exchange model able to describe experimental data obtained for H + and the four major cations (Na + , Ca 2+ , Mg 2+ and K + ) found in natural waters interacting with a <0.3 μm size fraction of Na-beidellite. The nature of the sites involved in the sorption processes is assessed using qualitative structural data. Moreover, the effect of the charge location in the smectite on the selectivity coefficient values is discussed by comparison with the results reported in the literature for smectite characterized by octahedral charge (montmorillonite). The new thermodynamic database proposed in this study is based on the same total sorption site density and distribution of sites regardless of the cations investigated. This database is valid for a large range of physico-chemical conditions: a [1–7] pH range, a total normality higher than 5 × 10 −3 mol/L corresponding to a flocculated state for water/clay systems, and when sorption of ions pairs can be neglected. Note that this study provides evidence that a thermodynamic database describing ion exchange reactions between H + and the four major cations of natural water for smectite cannot be valid irrespective of the total normality of the aqueous phase because smectite can form different phases (e.g., floc, gel) when immersed in aqueous system. The model proposed can be easily included in reactive transport software and is applied in the present study to predict the evolution of beidellite surface composition toward major inorganic cations in the context of mining site remediation. Finally, the new thermodynamic database proposed could be used for a better understanding of ion-exchange reactions occurring in many environments where beidellite is present, from soils to smectite-bearing sedimentary formations. [ABSTRACT FROM AUTHOR]

The relationships between clay minerals and associated iron and arsenic-rich phases are a main scientific issue in reactive mine waste-dumps. Therefore, this paper documents the composition and morphology of the fine fraction (< 2 μm), including the nano-sized Fe and As precipitates, associated with clay minerals in three distinctive sulfide-rich waste-dumps: Cerdeirinha , Lapa Grande , and Penedono (Northern Portugal). The obtained results indicated that the study sites have similar relative proportions of the detrital materials. However, major differences were observed in the remainder phases, which is in accordance with the mineralogy that was inherited from the respective ore deposits. In general, the clay mineral assemblage is dominated by the presence of illite, halloysite(7 Å), and beidellite. There are also associated minerals, such as jarosite and goethite, as well as amorphous As-rich nanoprecipitates with specific morphologies. Moreover, the results suggested that AMD conditions control the physical–chemical transformations, namely constraining the stability of the secondary phases formed by weathering in the waste dumps. Acidity is responsible for the degradation of the clay minerals, which is reflected in their crystalochemistry, structural order–disorder, and morphology. On the contrary, jarosite is more stable, being a dominant mineral in such environmental conditions. The stability of amorphous ferric arsenates or its evolution to a more crystalline phase is dependent on the Fe:As ratio, which is lower in Penedono . The study of the secondary products, especially the nanoparticles, puts in evidence their ability to control the mobility of trace elements, suggesting potential applications in environmental technology, including remediation of reactive mine waste-dumps. [ABSTRACT FROM AUTHOR]

This paper describes the petrographic properties and the clay mineralogy of Eocene sandy sediments of the Chu-Saryssu basin (South-Central Kazakhstan), in which dioctahedral smectite formed during shallow burial diagenesis (eogenesis). Evidence from petrography and clay mineralogy supports the successive occurrence of kaolinite and dioctahedral smectite during the eogenetic processes, which may have resulted from a change from wet and humid to semi-arid or arid climatic conditions. An original result of this study is the predominantly beidellitic nature of the authigenic smectite, which was determined via X-ray diffraction (XRD, using the Hofmann–Klemen test) and Fourier transform infrared spectroscopy (FTIR) investigations and chemical microanalysis. The crystal-chemical investigations indicate a rather homogeneous chemical composition of the smectite at the regional scale, and the following unit formula is proposed: (Si 4 + 3.65 Al 3 + 0.35 )(Al 3 + 1.65 Fe 3 + 0.21 Mg 2 + 0.14 )O 10 (OH) 2 Na + 0.10 Mg 2 + 0.11 Ca 2 + 0.04 K + 0.07 . This type of smectite has been interpreted as representative of mixed layers of montmorillonite and beidellite. The fact that the smectite that formed primarily in the unconsolidated sandy sediments is close to beidellite, rather than montmorillonite, may have a major impact on the rate of further illitization in the Chu-Saryssu basin. Indeed, the crystal chemistry of beidellite is more favorable to illitization, and the presence of this mineral provides new insights concerning the different rates of illitization between sandstones and shale formations observed worldwide. [ABSTRACT FROM AUTHOR]

The surfaces of natural beidellite were modified with cationic surfactant octadecyl trimethylammonium bromide at different concentrations. The organo-beidellite adsorbent materials were then used for the removal of atrazine with the goal of investigating the mechanism for the adsorption of organic triazine herbicide from contaminated water. Changes on the surfaces and structure of beidellite were characterised by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and BET surface analysis. Kinetics of the adsorption studies were also carried out which show that the adsorption capacity of the organoclays increases with increasing surfactant concentration up until 1.0 CEC surfactant loading, after which the adsorption capacity greatly decreases. TG analysis reveals that although the 2.0 CEC sample has the greatest percentage of surfactant by mass, most of it is present on external sites. The 0.5 CEC sample has the highest proportion of surfactant exchanged into the internal active sites and the 1.0 CEC sample accounts for the highest adsorption capacity. The goodness of fit of the pseudo-second order kinetic confirms that chemical adsorption, rather than physical adsorption, controls the adsorption rate of atrazine. [ABSTRACT FROM AUTHOR]

The preparation of antibacterial UV powder coatings dedicated to wood based panels is described in the present study. Two experimental methods were investigated: the generation of silver nanoparticles during the polymerization of UV powders and the introduction of a silver modified beidellite within UV powder formulations. While the first method leads to some nanoparticle aggregation, this phenomenon was avoided with the second approach. Antibacterial activity was thus ensured by the presence of beidellite modified with silver cations. XRD, X-ray fluorescence, SEM/EDX and TEM analyses allowed a complete characterization of the Ag-beidellite before its incorporation within UV powder formulations. Real-time-FTIR spectroscopy fitted with an environmental cell was used to monitor the reactivity of UV powder formulations under UV light and temperature control. Resulting coatings were finally characterized by UV spectroscopy, DMA in tension mode, XRD, TEM and antimicrobial analyses. It was shown that the fully cured and homogeneous coatings exhibit high thermomechanical properties and antibacterial activity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of eco-friendly corrosion inhibitor based on Ca2+-exchanged beidellite. [•] Improvement of corrosion inhibition by progressive release of Ca2+ from host mineral. [•] Role of beidellite in trapping aggressive corrosion species such as Cl−, Na+ and H+. [•] Valorization of natural Moroccan clay mineral. [•] Ca2+-BDT modified the physicochemical properties of electrolyte near zinc surface. [ABSTRACT FROM AUTHOR]

Abstract: Composites films were prepared by the casting method using native cassava starch plasticized with glycerol and 3D or 2D synthetic fillers i.e. Beta zeolite and Na-beidellite type 2:1 phyllosilicate. Special attention was paid to the effect of the filler contents and type on the mechanical and barrier properties. It was shown that films reinforced with lyophilized Beta zeolite presented both high water solubility (WS) and water vapor permeability (WVP) values than the pristine starch whereas an improvement on the WVP was found for composites prepared from Na-beidellite or from non lyophilized Beta zeolite. For the two types of fillers, a drastic increase of the mechanical properties (especially in the Young’s modulus) was observed. [Copyright &y& Elsevier]

Abstract: Pillared clays (PILCs) based on bentonite clay from “Bogovina” (Serbia) were obtained using Al3+ and Fe3+ pillaring cations in different ratios. Thorough characterization of the starting material and PILCs was performed for better understanding of the catalytic activity that they had exibited in the catalytic wet peroxide oxidation (CWPO) of organic pollutants in water. The characterization consisted of the following techniques: XRD, XRD of oriented samples (swelling test), Greene-Kelley test (smectite type determination), TGA/DTA followed by XRD analysis of samples heated at characteristic temperatures, elemental analysis using ICP-OES and microwave digestion, FTIR, DR UV–Vis, Mössbauer spectroscopy, nitrogen physisorption at −196°C and SEM imaging. Smectite in admixture with quartz was identified, together with impurities like feldspar, illite, chlorite and X-ray amorphous matter. Smectite mineral was dominantly of the beidellite type. Pillaring led to changes in the d 001 smectite basal spacing and stabilization of the smectite structure. Increasing Fe3+ content of the pillaring solutions resulted in the increased incorporation of iron into the PILCs as isolated octahedrally coordinated Fe3+ cations, smaller and bigger oligonuclear octahedrally coordinated Fe3+ species and octahedrally coordinated Fe3+ particles. The structure of incorporated pillars was similar to that of naturally occurring minerals akageneite and lepidocrocite. Micro- and mesoporosity were improved due to pillaring and the layered smectite structure was retained. [Copyright &y& Elsevier]

Abstract: This study deals with the development of a novel inhibitor based on heptanoate anions encapsulated within chitosan-modified beidellite. Included in coating, this inhibitor ensured efficient protection of metals against wet corrosion via permanent controllable release of the heptanoate inhibitor. The interlayer Na+ ions of beidellite from Agadir basin (Morocco) were exchanged with chitosan cations. The modified beidellite was studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermogravimetry (TG) analysis coupled to mass spectrometry (MS) and, X-ray diffraction (XRD) analysis. The expansion of the interlayer space of beidellite by ≈1.16nm, evidenced by XRD, was consistent with the arrangement of chitosan bilayer. Exceeding positively charged sites of the biopolymer were compensated by heptanoate anions. Electrochemical impedance spectroscopy (EIS) measurements were carried out on galvanized steel immersed in a 3mass% NaCl solution. The measurements revealed improvement of corrosion inhibition by chitosan-heptanoate modified beidellite in comparison with commercially available triphosphate aluminium (TPA) anti corrosion pigments. The improved corrosion inhibition was due to the continuous leaching of hepatanoate anions as inhibitors. However, the barrier properties of coatings containing chitosan-heptanoate modified beidellite were not as high as those of TPA-based coatings, probably due to insufficient dispersion of the modified beidellite particles within the polymeric matrix. [Copyright &y& Elsevier]

Abstract: Ab initio Molecular dynamics have been performed to study the free energy of adsorption of alkali atoms onto smectite clay surfaces and to identify the most favourable region in the interlayer for the cations. This is achieved by potential of mean force calculations using a constraint method to determine the lowest free energy configurations of lithium, potassium and sodium beidellite and sodium montmorillonite clays with a monolayer and bilayer of water present in the interlayer region. The constraint method has allowed us to examine the changes in the lowest free energy configuration for each ion with increasing hydration. From this, we can interpret the likelihood of clay swelling from the monolayer to bilayer coverage and compare with experimental observations. We find, that with a bilayer of water present, both lithium beidellite and sodium montmorillonite have their free energy minimum in the centre of the interlayer. For monolayer coverage, the free energy minimum for lithium, sodium and potassium beidellite is approximately the mid-point of the interlayer. Na-beidellite has a lowest free energy region at 6.1Å from the centre of the clay layer for both mono- and bi-layer coverage, while for the potassium counter-ion, commonly used as swelling inhibitor, the free energy profile for K-beidellite shows peaks close to both surfaces at approximately 6.2 and 8.6Å. We find that for systems where the free energy minimum remains in the middle of the interlayer when the hydration levels increase from monolayer to bilayer, it is known experimentally that these systems will swell in contact with water. The move to the middle of the interlayer with increasing hydration is associated with the full hydration sphere of the ion being composed purely of water oxygen atoms, and no clay surface oxygen atoms. [Copyright &y& Elsevier]

Abstract: The thermodynamic properties of three aluminous 2:1 clay minerals were acquired at 1.013 bars and at temperatures between 5 and 500K using various calorimetric methods. Calorimetric measurements were performed on hydrated and dehydrated <2μm clay fractions of smectite MX-80 (Wyoming), illite IMt-2 (Silver Hill) and beidellite SBId-1 (Black Jack Mine). After purification, the mineralogical analyses gave the following structural formulae: and for smectite MX-80, illite IMt-2 and beidellite SBId-1, respectively. Heat capacities were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 5 to 500K. Standard enthalpies of formation were obtained from solution–reaction calorimetry at 298.15K. The standard Gibbs free energies of formation of the clay minerals were also calculated, together with the equilibrium constants at 25°C, for anhydrous and hydrated minerals. A comparison between these experimental data and estimated values obtained from prediction models available in the literature, enabled the calculation method that appears to be the most relevant to be selected, at least for aluminous 2:1 clay minerals. [Copyright &y& Elsevier]

Abstract: Clay adsorbents were prepared via two-step method to remove nonionic alachlor and anionic imazaquin herbicides from water. Firstly, layered beidellite clay, a member of smectite family, was treated with acid in hydrothermal process; secondly, common silane coupling agents, 3-chloro-propyl trimethoxysilane or triethoxy silane, were grafted on the acid treated samples to prepare adsorbent materials. The organically modified clay samples were characterized by powder X-ray diffraction, N2 gas adsorption, and FTIR spectroscopy. It was found that the selective modification of clay samples displayed higher adsorption capacity for herbicides compared with acid activated clay. And the amount of adsorption is increased with increasing the grafting amount of silane groups. Clay grafted with 3-chloro-propyl trimethoxysilane is an excellent adsorbent for both alachlor and imazaquin but triethoxy (octyl) silane grafted clay is more efficient only for alachlor removal. [Copyright &y& Elsevier]

Abstract: Natural gas and coal are converted to fuels by the Fischer–Tropsch reaction, i.e., by reacting CO with H2, the currently accepted mechanism involving surface carbide formation. We have monitored the adsorbed species and their evolution during Fischer–Tropsch reaction on the commercial catalyst Pt,Co/γ-Al2O3 (as a standard), on Co/alumina-pillared montmorillonite (Co,Al-EFW) and its beidellite analogue (both are tri-octahedral smectite clays, but beidellite possesses tetrahedrally coordinated Al in the sheets) via optical diffuse reflectance (DRS 1 [1] Optical diffuse reflectance spectroscopy. ) and variable temperature in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS 2 [2] Diffuse reflectance infrared Fourier transformation spectroscopy. ). We show that in this case over Pt/Co-γ-Al2O3, under model conditions, H2 reacts with CO forming H–C over [Co-μO2-Co] units; this transition state moiety also involves adjacent matrix Al–O–CO units. Subsequent stages provide differing oxygenate species via concerted acid–base reactions. The early stages of the Fischer–Tropsch synthesis thus do not involve surface carbide species and surface oxygenates are generated via concerted reaction of support surface Al-OH with the above HCO-bridging binuclear Co2+ unit. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on acid activated beidellite and its adsorption ability for the herbicide simazine. After acid activation, the non-silicon atoms, such as Al, Mg, and Fe, which are located in the octahedral sheet, and sodium ions between the clay mineral layers were leached from the parent clay mineral. The basal spacing increased after acid activation. The acid activated beidellites were used to remove simazine from water. The simazine molecules can enter into the destroyed alumino silicate interlayer spaces and can be adsorbed from contaminated water. [Copyright &y& Elsevier]

Abstract: The hydrothermal synthesis of smectites in the Al–Fe3+ chemical series was investigated at various pHs and temperatures using stoichiometric coprecipitated hydrogels. For the first time, Al–Fe3+ smectites within a wide compositional range were successfully synthesized. The windows of experimental conditions to crystallize such smectites are narrow. Temperatures up to 150°C and high pH (around 12) are suitable for the formation of the Fe3+-rich smectitic end-member (nontronite), while higher temperatures (200°C) and lower pH (down to 7) are suitable for the more Al-rich smectites (Fe3+-beidellites). For intermediary compositions, the pH and temperature of synthesis leading to pure smectite crystallization should be concomitantly adjusted. Outside these windows, admixtures or other phases are obtained. This is probably the reason why smectites of the beidellite–nontronite series were not extensively synthesized previously. [Copyright &y& Elsevier]

Abstract: Mineralogical changes in the bentonite-based barrier of the laboratory Mock-Up-CZ experiment were evaluated by X-ray diffraction. The material of the barrier is a mixture of non-activated bentonite (containing Fe-montmorillonite with Ca2+ exchangeable cation) (85vol.%), quartz sand (10vol.%) and graphite (5vol.%). The barrier has been subjected to thermal stress (up to 90°C) and synthetic “granitic” water for 45months. From 70 analysed samples taken at different depth levels and distances from the source of the heat and/or water, 10 show measurable transformation of original smectites to either mixed illite/smectite structure (3 samples) or to beidellite (7 samples). Formation of mixed illite/smectite structure was restricted to the low temperature field (40–50°C) whilst beidellite occurs in zones affected by higher temperature (50–80°C). The low extent of smectite transformation (1–2wt.%) is due both to the relatively short time of the experiment in contrast to the duration of similar processes in nature and also to a limited supply of potassium cations from synthetic water used for hydration. Along with the above mentioned changes, newly formed gypsum bordered by illite aureol was detected in the upper part of the experimental set-up, i.e. in the zone in direct contact to the source of the water. Gypsum formation is interpreted as due to the oxidation of pyrite, a phase available either from the original bentonite where it is a common accessory or from the graphite used in the system due to heat transfer. In contrast to the non-transformed mixture the several mm wide illitic aureol of gypsum clusters shows a significantly lower ion exchange ability. [Copyright &y& Elsevier]

Abstract: Fe-rich kaolins in soils of a terrace chronosequence in the moist tropics of Costa Rica are derived from the transformation of smectite via interstratified kaolin–smectite (K–S). The smectite is ferruginous smectite (10.1±3.7% Fe2O3) that forms early during pedogenesis from basaltic–andesitic parent material and is the dominant mineral in <5 ka soils. Interstratified K–S with 60–90% kaolin layers is the dominant mineral in 10 ka soils, while 125 ka soils contain a physical mixture of Fe–kaolin (6.0±1.9% Fe2O3) and K–S with >80% kaolin layers. K–S is indicated by X-ray diffraction (XRD) data that reveal asymmetric 001 peaks between 17.5 and 17.8 Å (ethylene glycol-solvated) and irrational 00l peaks that exhibit Méring-like behaviour, and by transmission electron microscopy–analytical electron microscopy (TEM–AEM) data that document single crystals of K–S with compositions intermediate to those of end-member crystals of smectite and kaolin. Lattice fringe images from high resolution TEM (HRTEM) show lateral transitions from smectite layers to kaolin layers via a cell-preserved, layer-by-layer transformation mechanism, and changes in the compositions of tetrahedral and octahedral sheets, notably decreases in octahedral Fe and Mg and tetrahedral Al, indicate that the reaction is accompanied by localized dissolution of smectite 2:1 layers that proceeds laterally. Fourier transform infrared (FTIR) and XRD data indicate that kaolin layers are a mixture of kaolinite and halloysite, and differential thermal analysis–thermogravimetry (DTA–TG) combined with data from XRD and TEM–AEM indicate the development of Al-hydroxy-interlayers in K–S with time. The soil-forming factors that appear to control formation of K–S are (1) basaltic–andesitic parent that produces high concentrations of base cations and Si in young (<5 ka) soils, and (2) moist tropical climate (3085 mm MAP, 27.3 °C MAT) with a short dry season that fosters formation of smectite in <5 ka soils. By 125 ka, soils are dominated by Fe–kaolin and K–S, helping to constrain reaction rate. The relatively high cation exchange capacity (CEC) of the Fe-rich kaolins (18±12 cmolc/kg) relative to many tropical kaolinites is attributed to small amounts of octahedral Mg and tetrahedral Al inherited from precursor ferruginous smectite layers. Accordingly, the origin (from smectite) and relatively high CEC of the K–S and Fe–kaolin has potentially important implications related to clay mineral reactions and elemental cycling in moist tropical soils. [Copyright &y& Elsevier]

Abstract: Amine-terminated hyperbranched poly(amine-ester)(HBP) dendrimer synthesized in our laboratory was used as a complex agent of the lanthanum(La3+) particles, and montmorillonite (MMT) as a stabilizer to gain HBP/La/MMT ternary nanocomposites. The results of TEM showed that HBP/La composites were deposited on the surface of the MMT layers within nanoscales. The sizes of clusters become larger and larger with the increase of MMT content. The information of DSC indicated that the T g of HBP/La/MMT nanocomposites with 5–30 wt.% MMT were increased significantly. [Copyright &y& Elsevier]

Abstract: Nanocomposites of polyaniline (PANI) with organophilic montmorillonite (O-MMT) and hydrophilic montmorillonite (Na-MMT) were prepared. The nanocomposites were characterized using FT-IR, D.C. electrical conductivity measurement and cyclic voltammetry techniques. It was found that PANI/Na-MMT nanocomposite has lower (5.8%) and PANI/O-MMT nanocomposite has higher (29.4%) conductivity compared to pure polyaniline. Cyclic voltammetry experiments showed that both nanocomposites are electroactive. The anticorrosive properties of a 100μm thickness coating of nanocomposites on iron coupons were evaluated and compared with pure polyaniline coating. According to the results PANI/MMT nanocomposites have enhanced corrosion protection effect in comparison to pure polyaniline coating. Results showed also that the PANI/Na-MMT and PANI/O-MMT nanocomposites have considerably different corrosion protection efficiencies in various corrosive environments. [Copyright &y& Elsevier]

Abstract: Synthetic beidellite clays with variable Si/Al ratio in the tetrahedral layers were prepared by hydrothermal crystallization in an acid fluoride medium. The clay materials were characterized by powder-XRD, MAS NMR, BET specific area surfaces and chemical analysis. These samples were used as support for the immobilization of lipase B from Candida antarctica and lipase from Burkholderia cepacia by adsorption. The amount of lipase immobilized on the clay surface increased with decreasing level of aluminium substitution in the tetrahedral layer. The immobilization percentage was significantly higher for CALB (even for three times in the case of high siliceous clays) than those of BCL, when a sample of clay with the same composition is used as support. The catalytic properties of supported enzymes were investigated using the transesterification of vinyl acetate with 1-octanol as test reaction. The specific activity of the immobilized lipases depends on both the clay composition – the samples with low content of aluminum exhibited the highest specific activity-, and the amount of adsorbed enzyme – it increases as the amount of enzyme decreases. Also, the catalytic activity of lipase deposited on H+-beidellite is higher than those of enzyme deposited on the Na+ form. [Copyright &y& Elsevier]

Abstract: In the current work, a sensitive, rapid and convenient electrochemical method was developed for the determination of Sudan I utilizing the excellent properties of montmorillonite calcium (MMT-Ca). Compared with the unmodified carbon paste electrode (CPE), MMT-Ca modified CPE not only significantly enhances the oxidation peak current of Sudan I but also lowers the oxidation overpotential, suggesting that the MMT-Ca modified CPE can remarkably improve the determining sensitivity of Sudan I. The experimental conditions such as determining medium, the content of MMT-Ca and accumulation time were optimized for the determination of Sudan I. The oxidation peak current is proportional to the concentration of Sudan I over the range from 0.05mgL−1 (2.01×10−7 mol L−1) to 1.0mgL−1 (4.03×10−6 mol L−1), and the limit of detection is 0.02 mg L−1 (8.06×10−8 mol L−1) for 2-min accumulation. Finally this newly-proposed sensing method was successfully employed to detect Sudan I in practical samples and good recovery was achieved. [Copyright &y& Elsevier]

Abstract: Tri-octahedral Li–Mg smectites (hectorites) were synthesized at temperatures ranging from 25 to 250°C, in the presence of solutions highly enriched in lithium. After removing all the exchangeable lithium from the synthesized clays, Li isotope fractionation (Δ7Liclay-solution) was determined. This fractionation was linked to Li incorporation into the structural octahedral site, substituting for Mg2+. As predicted, experimental Δ7Liclay-solution inversely correlates with temperature, and ranges from −1.6‰±1.3‰ at 250°C to −10.0‰±1.3‰ at 90°C, and then stays relatively constant down to 25°C. The relatively constant isotope fractionation factor below 90°C may be due to high concentrations of edge octahedra in low crystallinity smectites. The isotopic fractionation factor (α), for a given temperature, does not depend on the solution matrix, nor on the amount of structural Li incorporated into the clay. Empirical linear laws for α as a function of 1/T (K) were inferred. Smectite Li contents and smectite-solution distribution coefficients (D Li/Mg) increase with temperature, as expected for a substitution process. The fractions of dissolved Li incorporated into the smectite octahedral sites are small and do not depend on the duration of the experiment. In a seawater-like matrix solution, less Li is incorporated into the smectites, probably as a result of competition with dissolved Mg2+ ions for incorporation into the octahedral sites. The high Li contents observed in marine smectites are therefore best explained either by a significant contribution from basalts, by adsorption processes, or by the influence of seawater chemical composition on distribution coefficients. We also calculate, using present-day estimates of hydrothermal water and river fluxes, that a steady-state ocean would require a relatively large global clay-water Li isotope fractionation (−12‰ to −21‰). This study demonstrates the ability of laboratory experiments to quantify the impact of secondary phases on the Li geochemical cycle and associated isotope fractionations. [Copyright &y& Elsevier]

Abstract: Toluene isopropylation is carried out over modified montmorillonite clays. Effect of ion exchange and pillaring on the catalytic activity and selectivity is noted. Elemental analysis results give the extent of metal incorporated. Enhanced porosity is evident from X-ray diffraction as well as surface area – pore volume measurements. 29Si NMR shows the resonance for T (3Si, 1Al) units which shifts proportional to the amount of pillar metal present. Among the different modifications mixed metal oxide pillaring is found to be most effective in catalytic activity, p-cymene selectivity and lowering deactivation. [Copyright &y& Elsevier]

Abstract: Platinum sub colloids (nm range) were synthesized in the presence of a surfactant (CTAB) by micellar technique in which the metal particles ensured long-term stability in the aqueous dispersion and were prevented from agglomeration. When this surfactant stabilized Pt hydrosol was allowed to react with aqueous suspension of Na+ montmorillonite or Li+ hectorite, the cationic exchange reaction between Na+/Li+ and organic cation (CTA+) took place with simultaneous incorporation of the reduced Pt particles into the organoclay host. Finely divided and well-dispersed Pt particles (nm range) were generated by this method in the interlamellar space of the montmorillonite and hectorite. The catalyst samples with different metal loadings were synthesized and characterized with UV–Vis spectroscopy, XRD, TEM and AAS techniques. From the TEM micrographs it was confirmed that the diameter of the Pt particles intercalated was in the nanometer range. The catalytic activity of the synthesized catalysts was studied towards the selective hydrogenation of C cinnamaldehyde using a batch type high pressure reactor at different temperatures and hydrogen pressures. The catalytic activity of the catalysts and their selectivity towards cinnamyl alcohol were discussed in detail. The activity and selectivity of 1wt.% Pt loaded montmorillonite catalyst was found to be appreciable. [Copyright &y& Elsevier]

Abstract: Natural and synthetic clay minerals have been transformed into Si-pillared mesoporous structures and then grafted with SH functions, for heavy metal ion trapping in polluted soils. The techniques and the limits encountered were detailed, with assessments of transformations by FTIR spectrometry and X-ray diffraction analyses. Adsorption isotherms of Cd2+ and Pb2+ were measured after 1 day shaking in calcium nitrate suspensions. Tests of Cd and Pb plant uptake were pursued by ray-grass cultivation on polluted soil amended or not with a functionalized synthetic beidellite during 3 months. Natural beidellite, hectorite and vermiculite were transformed into SH-grafted pillared clays but difficulties were encountered to keep a regular and significant interlayer distance until the last step. The well crystalline high-charge vermiculite of Santa Olalla (Spain), after Li-saturation, exchange with alkyl-ammonium cations, formation and grafting of interlayer Si-pillars, showed the highest capacity of Cd2+ and Pb2+ fixation among the 3 functionalized tested clay minerals. The cadmium uptake by ray-grass grown on polluted soil has been quite depressed by amendments with 0.17 or 0.5% of functionalized synthetic beidellite, but these amendments were inefficient for lead. [Copyright &y& Elsevier]

Abstract: Two montmorillonites, an inorganic sodium montmorillonite (NaMMT) and an organo-modified montmorillonite (OMMT), were used for the preparation of montmorillonite/polypyrrole (MMT/PPy) composites. MMT particles were modified by the in situ polymerization of pyrrole in water, in aqueous solution of dodecylbenzenesulfonic acid (DBSA) used as anionic surfactant, and in water/methanol. Ferric chloride was used as oxidant in each case. Wide angle X-ray scattering (WAXS) measurements proved the intercalation of PPy into the galleries of NaMMT regardless the reaction media. In contrast, for OMMT/PPy composites, the increase of interlayer spacing depends on the preparation conditions, the highest increase in interlayer spacing was achieved in water/DBSA solution. The WAXS patterns of OMMT/PPy composites synthesized in methanol/water showed no change in interlayer spacing and the electrical conductivity of these composites was low, similar to that of NaMMT/PPy composites prepared under the same conditions. Conductivity about 1.1Scm−1 was reached for OMMT/PPy composites containing 13.3wt% PPy prepared in the presence of DBSA. The NaMMT/PPy composite containing 15.6wt% PPy and prepared under the same conditions showed a conductivity of 0.26Scm−1. X-ray photoelectron spectroscopy (XPS) proved that the surface of NaMMT/PPy composites is rich in MMT, whereas more PPy was found on the surface of OMMT/PPy composites. The conductivity of composites correlated with the N/Si atomic ratio determined from XPS results, which was taken as a semi-quantitative measure of the PPy surface fraction. [Copyright &y& Elsevier]

Abstract: The thermal stability of seven organically modified montmorillonites (‘organoclays’) has been investigated using differential thermal analysis, differential scanning calorimetry, and thermogravimetry in conjunction with X-ray diffractometry. Six organoclays were synthesised by replacing the interlayer inorganic cations, initially present, with quaternary phosphonium and ammonium surfactant cations. The samples modified with tetrabutylphosphonium (TBP), and butyltriphenylphosphonium (BTPP) ions have an appreciably higher thermal stability than the octadecyltrimethylammonium (ODTMA)-modified clays. Thus, in the case of TBP- and BTPP-modified montmorillonites, the onset temperature of decomposition is close to 300 °C. Samples modified with hexadecyltributylphosphonium (HDTBP) ions have a lower onset temperature of decomposition of 225 °C. In comparison, the onset temperature for ODTMA-montmorillonites (obtained at different concentrations of ODTMA-bromide) ranges from 158 to 222 °C, being highest where the concentration of intercalated surfactant is lowest. The onset temperature for a commercial alkylsilane-treated quaternary ammonium-modified organoclay (S-BEN N-400FP) is 207 °C. The basal spacing of the TBP- and BTPP-modified clays is 1.7–1.8 nm, indicating a monolayer arrangement of quaternary phosphonium ions in the interlayer space, while the value of 2.5 nm for HDTBP-montmorillonite indicates a more open structure. The ODTMA-modified samples have basal spacings ranging from 1.9 to 2.1 nm, indicative of a bilayer to pseudo-trilayer arrangement. The exceptionally high basal spacing of 3.4 nm for the S-BEN N-400FP organoclay might be due to interlayer penetration of organosilane hydrolysis products during synthesis. The thermal properties of organoclays are apparently related to the nature of the surfactants and their arrangement in the interlayer space of montmorillonite. [Copyright &y& Elsevier]

Abstract: Poly(vinyl alcohol)-based mixed matrix membranes loaded with 5 and 10wt.% of sodium montmorillonite (Na+MMT) clay particles, i.e. (PVA/Na+MMT-5 and PVA/Na+MMT-10), were fabricated by solvent casting method. The uncrosslinked membranes were used in pervaporation (PV) dehydration of aqueous solutions of isopropanol and 1,4-dioxane at 30°C. Membrane morphology was characterized by scanning electron microscopy. Differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical thermal analysis were used to understand thermal properties. Universal testing machine was used to study mechanical strength properties. Separation factor to water has increased from 1116 to 2241 for PVA/Na+MMT-5 and PVA/Na+MMT-10 mixed matrix membranes when tested for 10wt.% water-containing isopropanol feed, but the corresponding flux values of 0.051 and 0.075kg/m2 h were somewhat lower than those observed for pristine PVA membrane. On the other hand, for water+1,4-dioxane feed mixtures, separation factors were quite lower and ranged from 216 to 369 with the corresponding flux values of 0.076 and 0.093kg/m2 h, respectively, for PVA/Na+MMT-5 and PVA/Na+MMT-10 membranes at 10wt.% water in the feed. Membranes of this study could extract up to 99.20 and 99.60wt.% water on the permeate side from water–isopropanol mixture, while from water–1,4-dioxane mixture, only 96.0 and 97.62wt.% of water were removed for 10wt.% water-containing feed. The membranes were further tested for PV at 40, 50 and 60°C for 10wt.% of water-containing feeds of aqueous isopropanol and 1,4-dioxane solutions to confirm their stability at higher temperatures. Plots of ln J p versus 1/T are linear in the studied range of 30–60°C for both the feed mixtures, indicating that flux follows an Arrhenius trend. PV results are discussed in terms of water flux, separation factor, permeation separation index, enrichment factor and activation energy of permeation. Sorption and PV experiments were carried out for the thermally crosslinked and glutaraldehyde crosslinked PVA/Na+MMT mixed matrix membranes for 10wt.% water-containing feed mixtures at 30°C. A small increase in separation factor with a slight sacrifice in flux was observed without showing any great difference as compared to uncrosslinked mixed matrix membranes. The hydrophilic nature of Na+MMT clay and the formation of PVA/Na+MMT mixed matrix membranes are responsible to offer such increased separation to water over the organic components of the feed mixtures. [Copyright &y& Elsevier]

Abstract: This paper represents an overview of the spectroscopic studies of both synthetic and naturally occurring beidellites performed as part of my research over the past 16 years. It shows that detailed information on the local structure of beidellite and changes in this local structure upon heating can be obtained by combining a range of spectroscopic techniques such as mid-infrared, near-infrared, infrared emission, Raman, nuclear magnetic resonance and X-ray photoelectron spectroscopy. [Copyright &y& Elsevier]

The effect of exchanging transition metal ions in the alumina-pillared beidellite/montmorillonite FAZA on the conversion of methanol, ethanol, n-propanol and iso-propanol has been investigated. It is concluded that dehydration/dehydrogenation throughout the series of materials occurs preferentially at the oxidic pillar rather than at the aluminosilicate sheet. The basal structure of the smectite, i.e. whether protons lie inside (montmorillonitic) or outside (beidellitic) the aluminosilicate layers, little influences the reactions. By way of contrast, cation exchange (both single and double) greatly influences both product ratio outcomes and conversions, e.g. Ni-FAZA (FAZA=a Fe2+/Fe3+/alumina-pillared mixed beidellite/montmorillonite) has very acidic centres suppressing MeOH dehydration completely. [Copyright &y& Elsevier]

The silver–gold ore deposits of the De Lamar mine, the mines in Florida Mountain and the mines in War Eagle Mountain occur in conjunction with large seams of clay minerals, which consist mainly of mixed-layer illite–beidellite. When saturated with groundwater, these clay seams have caused slope failures during mining and processing of ore. The illite–beidellite clays have effective internal friction values, Øe, as low as 4° and cementation C values of about 1.0 kg f/cm2. The Fe-beidellite used for the clay core of the mill pond dam has an average Øe value of 8.3° and C value of 0.79 kg f/cm2, with an average permeability (K-value) of 5.6×10−7 cm/s.The fundamental OH spectra of beidellite, illite and muscovite are similar with beidellite having bands near 3635, 3654 and 3653 cm−1. Montmorillonite has one Al–OH libration band near 915 cm−1, whereas beidellite has a second band near 942 cm−1. In like manner, illites and muscovites have bands from 928 to 933 cm−1, as well as the Al–OH libration bands from 912 to 917 cm−1. The OH libration bands vary both in position and intensity with particle orientation and heating.Combination bands for Fe-bearing muscovite show moderate bands at 4451 cm−1 for ferrous muscovite and at 4471 cm−1 for ferric muscovite. These bands also are present for illites. The dominant Al–OH combination band wave numbers of muscovites form a linear relationship with the Al2O3 muscovite contents, but not so precisely for illites. Chemical analysis of illites indicates that the compositions are a continuum into muscovites. Illites from the Miller–Walters mine contain a rather large amount of certain trace elements, whereas the adjacent beidellites do not. [Copyright &y& Elsevier]

New intercalated clay materials based on the combination of four systematically selected alkylphosphonium organocations and beidellite (Bd) were prepared. Particularly, tetraethyl-, tetrabutyl-, tetrahexyl- and tetraoctyl- phosphonium cations were used in the synthesis. The samples were characterized by X-ray diffraction, thermal analysis, infrared spectroscopy and elemental carbon analysis. Further, calculations based on density functional theory method including dispersion corrections (DFT-D3) were carried out in a prediction of stability and detailed characterization of the structure and interactions of the beidellite intercalated models corresponding to four tetraalkylphosphonium cations used in experiment (4PX-Bd; X = 2, 4, 6, 8 / ethyl-, butyl-, hexyl-, octyl-). Calculated interlayer distances (d 001) for all four models agreed well with experimental data continuously growing with a length of the alkyl chains of the 4PX cations. The structural stability of 4PX-Bd intercalates also increased with the size of the 4PX cations. Calculated vibrational spectra obtained from ab initio molecular dynamics were in a good agreement with experimental IR spectra. Further, a sorption capacity of synthetized organobeidellites was probed by loading sulfamethoxazole drug and quantified by liquid chromatography method. Adsorption of sulfamethoxazole was the most effective using tetraoctylphosphonium-modified beidellite. [Display omitted] • Intercalation of four tetraalkyphosphonium cations into beidellite • Adsorption of antibiotic sulfamethoxazole • Using molecular simulation explained the changes of interlayer space & IR • Structural stability of organobeidellites grows with alkyl chain of cations [ABSTRACT FROM AUTHOR]

Smectites affecting water and soil exchangeable cations, especially potassium and ammonium related to plants, are common swelling clay minerals in sediments and paleosols that can record paleoenvironmental and paleoclimatic information. Paleoenvironmental and paleoclimatic interpretations are potentially ambiguous, because smectite minerals may have either detrital or pedogenic origins. This study analyzes smectites in Lower Eocene paleosols of the Qaidam Basin, China, with the goal of determining their origin and paleoclimatic significance. Twelve smectite-rich vertisol samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) in the Dahonggou (DHG) section of the Lulehe Formation. The samples from DHG section contained predominant dioctahedral smectites (60–65%) in the <2 μm clay fractions. Minor dioctahedral illites, dioctahedral interstratified illite-smectite (I-Sm), kaolinite, and traces of dioctahedral chlorites and palygorskites were present. The chemical data and FTIR spectra revealed both tetrahedral substitutions (i.e., Al for Si) and octahedral substitutions (i.e., Mg and minor Fe for Al) in the dioctahedral smectites. Montmorillonite comprised the dominance of the fine-clay fractions (< 0.2 μm) with minor contributions of beidellite, as determined by the Greene-Kelly test (GK-test), geochemical and FTIR analyses. SEM observations revealed two morphological types of dioctahedral smectites, the less abundant one with typical 'honeycomb' structure, interpreted as neoformed, and the other occurring as thin, well-defined plates and irregular masses considered to be detrital. DSC revealed two dehydroxylation temperatures (500–550 °C and 600–700 °C), indicating the presence of trans- vacant (t v) and cis- vacant (cv) layers, respectively. The cv layers were attributed to montmorillonite originating as catchment-delivered detritus, as the study Lulehe Formation exhibited no evidence of volcanic ash layers or diagenesis that would have promoted formation of montmorillonite with high dehydroxylation temperatures. The tv layers represented pedogenic beidellite formed via solution crystallization in a floodplain pedogenic environment. The accumulation of abundant inherited montmorillonite and neoformed beidellite in paleosols of the Lulehe Formation was probably promoted by a relatively warm climate with alternating wet-dry seasons during the Early Eocene. Admixture of detrital montmorillonite makes paleoclimatic reconstructions based on bulk-smectites concentrations and isotopic compositions unreliable, showing that integrated clay mineralogical analyses of the type undertaken in this study are necessary to identify the provenance and paleoclimatic significance of smectites in sediments. • Two subtypes of smectite, montmorillonite and beidellite, occur in Lulehe palesosols. • Predominant montmorillonite with high thermal ability has a detrital origin. • Minor beidellite with low dehydroxylation temperatures has a pedogenic origin. • Smectite accumulation/formation increased during EECO due to seasonal wet and dry. • Smectites in soils can be of multiple origin making their paleoenvironmental interpretation complex. [ABSTRACT FROM AUTHOR]

• Swelling pressure trend of smectites with alkaline-earth interlayer cations was studied. • Variables used are interlayer cation, d-spacing, dry density, total charge and location. • Swelling pressure increased as the interlayer cation progressed up the group. • Swelling behavior of Mg-smectite was different from other cation-smectites. Interlayer swelling pressure of smectite minerals was investigated at atomic level using molecular dynamics simulation method. Four different alkaline-earth cations were used as interlayer cations for simulated montmorillonite and beidellite minerals. The swelling pressures of the smectite minerals were obtained as function of interlayer cation, layer charge, charge location, dry density and d-spacing. The swelling pressure of the homoionic smectites follows the trend Mg2+ > Ca2+ > Sr2+ > Ba2+. Layer charge and charge location have also a notable effect on swelling pressure. Octahedrally substituted smectites show higher swelling pressure than tetrahedrally substituted, while lower layer charge lead to higher pressure than higher layer charge. The results have practical implications in the selection and predicted behaviour of backfilling clay materials for geodisposal of high-level radioactive waste. [ABSTRACT FROM AUTHOR]