bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silication of Hydroxy-Al Interlayers in Smectite
Authors: Lou G. , Huang P. M. 
Published: August 2006

AbstractThe reaction of hydroxy-Al interlayers in montmorillonite with monosilicic acid was studied by chemical analysis, X-ray diffractometry (XRD), and Fourier-transform infrared (FTIR) spectroscopy. Hydroxy-Al interlayers in montmorillonite was prepared by treating Ca-montmorillonite (<2) μm) with hydroxy-Al solutions at an initial Al concentration of 0.5 mM and OH/Al molar ratios of 1.0, 2.0, and 2.5. The resultant partially interlayered montmorillonite was reacted with 0.5, 0.9, and 1.4 mM monosilicic acid solutions.A substantial amount of monosilicic acid was adsorbed by the interlayer hydroxy-Al polymers through the reaction of Si-OH groups with mainly Al-OH groups, resulting in the formation of silicated Al-interlayers with Si/Al molar ratios up to 0.19. The adsorption of silicic acid by interlayer hydroxy-Al polymers increased the basal spacings of the partially interlayered montmorillonite. This effect was most pronounced for the hydroxy-Al interlayered montmorillonite formed in the systems at an OH/Al ratio of 2.0, in which the d(001) reflections (110°C) shifted from 13.6 Å before silication to 14.1 Å with a shoulder at 17.0 Å after silication. The differential IR spectrum of the silicated hydroxy-Al interlayers in montmorillonite exhibited absorption bands at 935 and 3730 cm−1, which can be assigned to Si-O and Si-OH, respectively, of the adsorbed Si(OH)4. An interlayer structure analogous to that of “proto-imogolite” was, thus, proposed for the silicated interlayer hydroxy-Al polymers in montmorillonite. This study revealed a new mechanism through which Si enters the interlayer spaces of smectite. The silication of hydroxy-Al-interlayered clays in natural environments and the related modifications in surface properties of the clays should receive increasing attention.
The Intercalation of Kaolinite by Alkali Halides in the Solid State: A Systematic Study of the Intercalates and their Derivatives
Authors: Thompson John G. , Gabbitas Neil , Uwins Philippa J. R. 
Published: August 2006

AbstractKaolinite: alkali halide intercalates have been successfully prepared by grinding the salt with kaolinite in the absence of water. Rate of intercalation is shown to correlate negatively with melting point of the salt. The basal dimensions of the intercalates increase with increasing size of the ion. As shown recently for kaolinite: NaCl intercalate, the layered structure survives the dehydroxylation of the kaolinite at 500°–600°C, at which point the excess alkali halide can be removed by rinsing to give an XRD-amorphous material. This amorphous material, of approximate stoichiometry MAlSiO4, reacts at surprisingly low temperatures to give crystalline phases, apparently of the same stoichiometry, with structures closely related to eucryptite (M = Li), carnegieite (M = Na), kalsilite (M = K), and leucite (M = K, Rb, Cs). The relationships between the structures of the reaction products are discussed.
13C CPMAS Nuclear Magnetic Resonance Study of the Adsorption of 2-Phenethylamine on Clays
Authors: Bank Janet F. , Ofori-Okai Gabriel , Bank Shelton 
Published: August 2006

Abstract2-Phenethylamine 13C-enriched in the beta position was adsorbed on four different aluminum-exchanged clays: hectorite, Barasym, Laponite RD, and lithium taeniolite. The sites for adsorption were characterized by 13C high-resolution cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS-NMR) spectroscopy. Using differences in chemical shift values and linewidths, three different types of bound ammonium compounds and a motionally restricted bound compound were identified. Correlation with charge effects indicated that one of the clay sites was extremely acidic.The important catalytic sites for the different clays, the edge or platelet face, interlamellar and some combination of both, were probed by using the trimethylsilyl group as a clay-blocking agent. Silylation of aluminum-exchanged Laponite RD and Li taeniolite had little effect on amine adsorption. This indicates that, for these clays, amine adsorption occurred mainly at interlamellar sites. For hectorite, amine adsorption occurred at both surface and interlamellar sites, and silylation had the effect of reducing surface adsorption. Silylation of Barasym resulted in a very interesting shift of adsorption from one kind of surface site to a more acidic surface site.
40Ar/39Ar Analyses of Authigenic Muscovite, Timing of Stylolitization, and Implications for Pressure Solution Mechanisms: Jurassic Norphlet Formation, Offshore Alabama
Authors: Thomas Andrew R. , Dahl William M. , Hall Chris M. , York Derek 
Published: August 2006

AbstractThree authigenic muscovite morphologies are associated with Norphlet Formation stylolitization observed in the Texaco Mobile Area Block 872 #1 well: l)large crystals of 1M muscovite, which grew in the stylolites with their c-axes parallel to the plane of maximum compressive stress; 2) fine-grained bundles of muscovite that occur as pore-fillings near stylolites; and 3) pods of fine-grained muscovite that exist within stylolite insoluble residue and that were precipitated as pore-filling muscovite before the host sandstone pressolved.The population of large crystals of 1M muscovite grew at 51 ± 9 Ma, pore-filling muscovites precipitated at 77 ± 22 Ma, and muscovite pods have ages of 86 ± 16 Ma, as indicated by 40Ar/39Ar laser fusion. Apparent ages indicate that stylolitization was coincident with the beginning of organic maturation Zone 5 and could be the product of reservoir fluid pressure fluctuations induced by gas leakage. The lower Smackover Formation source/seal rock, acting as a pressure relief valve, could have been compromised by microfractures occurring during hydrocarbon generation and expulsion. Decreases in reservoir fluid pressure would have acted upon the sandstone framework by increasing the effective overburden pressure, thus making the rock more susceptible to pressure solution.Stylolite frequency and quartz cement volume increase in the finer grained portion of the conventional core. Quartz cement volume correlates inversely to percent sandstone porosity. Apparent muscovite ages indicate that stylolitization occurred after hydrocarbon migration. Silica mobility was limited because pressure solution mineral products were precipitated from within grain films of irreducible water within the sandstone.Stylolitization of quartz grains accounts for a minimum of 34% of the quartz cement in the upper cored section of the Norphlet Formation and minimum of 17% of the quartz cement in the lower cored Norphlet Formation. Quartz cement volumes are based on stylolite insoluble residue thickness and weight measurements of pyrobitumen within and nearby the insoluble residue seams. Stylolitization of K-feldspar and precipitation of muscovite can release additional silica which may have precipitated as quartz cement.
Modeling of H+ and Cu2+ Adsorption on Calcium-Montmorillonite
Authors: Stadler Markus , Schindler Paul W. 
Published: August 2006

AbstractThe interaction of H+- and Cu2+-ions with Ca-montmorillonite was investigated in 0.1 mol/dm3 solutions of Ca(CIO4)2 at 298.2 K by Potentiometrie titrations using both glass electrodes (for H+) and ion specific electrodes (for Cu2+ ). The experimental data were interpreted on the basis of the surface complexation model. The calculations were performed with the least-squares program FITEQL (Westall, 1982) using the constant capacitance approximation. The best fit was obtained with a set of equilibria of the general form
pH++qCu2++≡SOH⇔(H+)p(Cu2+)q(≡SOH)(p+2q)+βp,q(int)s=[HpCuq(≡SOH)(p+2q)][H+]p[Cu2+]q[≡SOH]
and the constants log β1,0(int)S = 8.16 (± 0.04), log β-1,0(int)S = −8.71 (± 0.08), log β0,1(int)S = 5.87 (± 0.06), log β−1,1(int)S = −0.57 (± 0.12), log β−2,1(int)S = −6.76 (± 0.02). An appropriate modeling of the H+ adsorption data requires the introduction of a second surface group ≡ TOH with the acidity constant
≡TOH−H+⇔≡TO−logβ−1,0(int)S=−5.77(±0.07). In addition, the ion exchange equilibria Ca2+ − Cu2+ and Ca2+ − H+ had to be taken into account. Arguments are presented to identify the groups ≡ SOH and ≡ TOH as surface aluminol groups =Al(OH)(H2O) and surface silanol groups ≡ Si-OH, respectively.
Adsorption of Water Vapor by Soils: Investigations of the Influence of Organic Matter, Iron, and Aluminum on Energetic Heterogeneity of Soil Clays
Authors: Sokołowska Z. , Jòzefaciuk G. , Sokołowski S. , Ourumova-Pesheva A. 
Published: August 2006

AbstractWater vapor adsorption isotherms were measured for samples of loessial soil clays modified by removing organic matter and Fe and Al compounds. The isotherms were analyzed by the exponential adsorption isotherm equation. The distribution functions of adsorption energy, average adsorption energies, and surface areas were evaluated simultaneously. The surface areas were the highest for samples after organic matter removal and the lowest when all considered components were removed. Values of the average adsorption energies decreased consecutively after each of the subsequent removal steps while the energy distributions became narrower, indicating in general less variety in surface adsorbing centers.
Low Temperature Experimental Investigation of the Effect of High pH Koh Solutions on the Opalinus Shale, Switzerland
Authors: Chermak J. A. 
Published: August 2006

AbstractBatch reactor experiments were performed at 150°C, 175°C, and 200°C to determine the effect of high pH KOH solutions on the mineralogy of the Opalinus shale. In these experiments, the change in solution quench pH at 25°C, solution composition, and mineralogy were monitored as a function of time for up to ≈ 50 days. Runs were performed in 50 ml titanium hydrothermal reactor vessels. Each reactor was charged with 0.5–5.0 grams of the 80–200 mesh size fraction of Opalinus shale, and 25 ml of solution (0.08 and 0.008 m KOH). Under these high pH conditions, the general sequence of reaction products observed is the formation of phillipsite, followed by K-feldspar ± K-rectorite. Phillipsite is a metastable intermediate that eventually transforms to K-feldspar. This sequence of mineral reaction products is very different from that found in the NaOH system.
Charge Heterogeneity and Nanostructure of 2:1 Layer Silicates by High-Resolution Transmission Electron Microscopy
Authors: Malla P. B. , Robert M. , Douglas L. A. , Tessier D. , Komarneni S. 
Published: August 2006

AbstractSeveral soil and reference smectites and vermiculites and one reference illite were examined by high-resolution transmission electron microscopy (HRTEM) to decipher the nanostructure and layer charge heterogeneity in these minerals. HRTEM results were compared with those obtained from powder X-ray diffraction (XRD) analysis. Samples were either exchanged with Na+ions followed by equilibration with a very dilute solution of NaCl in a pressure membrane apparatus at 316 hPa (pF = 2.5) to see the effect of hydration and applied pressure on layer organization, or exchanged with dodecylammonium ions to see the expansion behavior. Oriented samples were embedded in a low viscosity resin and cut approximately 500 Å thick perpendicular to d(001) using an ultramicrotome fitted with a diamond knife. In general, Na-saturated soil clays possessed crystallites that were thinner (c-direction) and shorter (ab-direction) as compared with reference clays. In all cases, samples treated with dodecylammonium chloride exhibited nanostructures that were more disintegrated as compared with Na-saturated samples. In a soil vermiculite, dodecylammonium ion exchange showed frayed edges indicating the initiation of mica transformation to vermiculite from edge toward core. In a reference vermiculite (Transvaal) treated with dodecylammonium ions, in addition to completely expanded crystallites, a regular interstratification between expanded vermiculite and mica (phlogopite) layers was clearly observed in some crystallites. Such nanostructural details were not detected by XRD. HRTEM of the Na-treated illite showed thick crystallites having 10 Å layer separations, whereas the dodecylammonium-exchanged illite showed three types of layers with different degrees of expansion indicating charge heterogeneity in illite: 1) unexpanded (10 Å, highest charge) crystallites; 2) expanded high-charge vermiculite-like (24 Å) crystallites; and 3) occasionally expanded high-charge vermiculite-like (24 Å) layers interspersed in the matrix of 10Å crystallites.
Synthesis and Paragenesis of Na-Beidellite as a Function of Temperature, Water Pressure, and Sodium Activity
Authors: Kloprogge J. Theo , van der Eerden A. M. J. , Jansen J. Ben H. , Geus John W. , Schuiling Roelof D. 
Published: August 2006

AbstractIn the chemical system Na2O-Al2O3-SiO2-H2O, the stability field of Na-beidellite is presented as a function of pressure, temperature, and Na- and Si-activity. Na0.7-beidellite was hydrothermally synthesized using a stoichiometric gel composition in the temperature range from 275° to 475°C and at pressures from 0.2 to 5 kbar. Below 275°C kaolinite was the only crystalline phase, and above about 500°C paragonite and quartz developed instead of beidellite. An optimum yield of 95% of the Na0.7- beidellite was obtained at 400°C and 1 kbar after 20 days. Gels with a Na-content equivalent to a layer charge lower than 0.3 per O20(OH)4 did not produce beidellite. They yielded kaolinite below 325°C and pyrophyllite above 325°C. With gels of a Na-content equivalent to a layer charge of 1.5, the Na-beidellite field shifted to a minimum between temperatures of 275° and 200°C. This procedure offers the potential to synthesize beidellite at low temperatures. Beidellite synthesized from Na1.0-gel approach a Na1.35 composition and those from Na1.5- and Na2.0-gels a Na1.8 composition.
Sampling and Analysis of KGa-1B Well-Crystallized Kaolin Source Clay
Authors: Pruett Robert J. , Webb Harold L. 
Published: August 2006

AbstractAdditional well-crystallized kaolin from Washington County, Georgia, has been supplied to the Clay Minerals Society Source Clay Repository to replace the exhausted supply of KGa-1. This kaolin is called KGa-1B and is from a geographic location and stratigraphic position close to where KGa-1 was collected. Slight mineralogical and chemical differences are observed between KGa-1 and KGa-1B. KGa-1B crude appears slightly better crystalline than KGa-1, and it has a slightly higher titania content than KGa-1. The Al2O3, SiO2, Fe2O3, alkali, and alkaline earth contents appear similar for both samples. KGa-1 has a slightly coarser particle size than KGa-1B crude. More intensive post-depositional alteration may have cleansed and crystallized the KGa-1B material to a slightly greater degree than the KGa-1 material.
Zeolites in Pyroclastic Deposits in Southeastern Tenerife (Canary Islands)
Authors: Hernandez J. E. Garcia , Notario del Pino J. S. , Gonzalez Martin M. M. , Hernan Reguera F. , Rodriguez Losada J. A. 
Published: August 2006

AbstractThe chemical and the mineralogical composition of a group of pumiceous tuffs associated with recent salic volcanic episodes from Tenerife (Canary Islands) have been studied. The investigation focused on the two main types of pyroclastic deposits of the zone: ash-flows and ash-falls. The samples can be classified chemically as trachytic and phonolitic rocks with an intermediate silica content and a high percentage of alkali cations (Na+ and K+). The mineralogical composition, determined by X-ray diffraction, scanning electron microscopy, and optical microscopy, shows the occurrence of zeolites (mainly phillipsite, with lesser chabazite and analcime), associated with the parent glass. K-feldspar (sanidine) and calcite are accessory minerals. Zeolites are significantly more abundant in the ash-flow deposits. Zeolite formation by hydrothermal weathering in closed-system conditions varies according to the nature and the origin of the pyroclastic deposits. Tenerife phillipsites differ from typical diagenetic, lacustrine, and deep-sea phillipsites, both in chemical and mineralogical features. Alkali cations exceed divalent cations in the unit-cell that, assuming a monoclinic symmetry, has the following parameters: a = 8.46–10.55 Å, b = 14.21–14.40 Å, c = 7.80–8.70 Å, and β = 105°–110°.
Potassium Halide-Treated Montmorillonite (KTM) as a Solid Phase in Liquid Chromatography
Authors: Tsvetkov Faina , Heller-Kallai Lisa , Mingelgrin Uri 
Published: August 2006

AbstractColumns for high pressure liquid chromatography were prepared from spray dried samples of montmorillonite that were heated with potassium halides (KTM) to increase both the cation density on the clay surfaces and the expandability of the interlayers. Some of the clay samples were exchanged with Cu before and/or after the potassium halide treatment.Retention of nitrobenzene and its chloro and methyl derivatives, of methyl substituted phenols and of nitrophenols on these columns was studied, using eluents ranging in polarity from hexane to isopropanol. The retention of the aromatic molecules depends on their specific interaction with active sites on the clay surfaces and on steric effects which limit access to the clay interlayers. Both penetrability and surface interaction are controlled by the composition and method of preparation of the solid phase and by the polarity of the mobile phase. Very strong adsorption of some eluates and efficient chromatographic separations between related substituted benzenes were achieved. Mixtures of the three isomers of cresol, chloronitrobenzene, nitrotoluene or nitrophenol were completely resolved by a judicious combination of solid phase and eluent.
Compositional End Members and Thermodynamic Components of Illite and Dioctahedral Aluminous Smectite Solid Solutions
Authors: Ransom Barbara , Helgeson Harold C. 
Published: August 2006

AbstractConsideration of XRD, TEM, AEM, and analytical data reported in the literature indicates that dioctahedral aluminous smectite and illite form two separate solid solutions that differ chemically from one another primarily by the extent of Al substitution for Si, the amount of interlayer K, and the presence of interlayer H2O. The data indicate that limited dioctahedral-trioctahedral and dioctahedral-vacancy compositional variations occur in both minerals. Excluding interlayer H2O and based on a half unit cell [i.e., O10(OH)2], natural dioctahedral smectite and illite solid solutions fall within the compositional limits represented by A0.3${\rm{R}}_{1.9}^{3 + }$Si4O10(OH)2-AR2+ R3+ Si4O10(OH)2-A0.25${\rm{R}}_{0.3}^{2 + }{\rm{R}}_{1.8}^{3 + }$Al0.25Si3.75O10(OH)2 for smectites and A0.8${\rm{R}}_{1.9}^{3 + }$Al0.5Si3.5O10(OH)2-A0.55${\rm{R}}_{0.45}^{2 + }{\rm{R}}_{1.55}^{3 + }$Al0.1Si3.9O10(OH)2-A0.9${\rm{R}}_{0.3}^{2 + }{\rm{R}}_{1.8}^{3 + }$Al0.9Si3.1O10(OH)2 for illites, where A represents either monovalent cations or divalent cations expressed as their monovalent equivalent (e.g., Ca2+/2); R2+ stands for the divalent cations Mg2+ and Fe2+ and R3+ refers to the trivalent cations Al3+ and Fe3+. Taking account of these compositional limits, smectite and illite solid solutions can be described in terms of nine and six thermodynamic components, respectively, all of which are consistent with both the law of definite proportions and the concept of a unit cell. Thermodynamic components that can be used to describe natural smectite solid solutions in terms of a half unit cell [i.e., O10(OH)2] can be expressed as NaAl3Si3O10(OH)2, NaAl3Si3O10(OH)2 ·4.5H2O, Al2Si4O10(OH)2, Fe2Si4O10(OH)2, Mg3Si4O10(OH)2, Fe3Si4O10(OH)2, K3AlSi4O10(OH)2, KAl3Si3O10(OH)2, and Ca0.5Al3Si3O10(OH)2. Of these, NaAl3Si3O10(OH)2 ·4.5H2O provides explicitly for the presence of interlayer H2O in the mineral. Thermodynamic components representing illite solid solutions in natural systems can be written for a half unit cell as KAl3Si3O10(OH)2, KMg3AlSi3O10(OH)2, KFe3AlSi3O10(OH)2, Al2Si4O10(OH)2, KFe2AlSi3O10(OH)2, and K3AlSi4O10(OH)2. The calculations and observations summarized below indicate that neither smectite nor illite occur in nature as stoichiometric phases and that the two minerals do not form a mutual solid solution corresponding to mixed-layered illite/smectite.
Polytype Diversity of the Hydrotalcite-Like Minerals I. Possible Polytypes and their Diffraction Features
Authors: Bookin A. S. , Drits V. A. 
Published: August 2006

AbstractAll possible polytypes of hydrotalcite-like minerals with a periodicity along the c axis of one-, two- and three-layers, as well as the simplest six-layer polytypes, were derived on the basis of the concept of closely packed brucite-like layers. Multilayer structures were found to be possible in several polytype modifications—three two-layer, nine three-layer, and a set of six-layer polytypes. The neighboring layers may be stacked in two different ways, building two kinds of interlayers: P-type where OH sheets lie one above another forming prisms and O-type where OH groups forms octahedra. Based on the kind of interlayer space, all polytypes may be separated into three groups: homogeneous interlayers of O-, or P-type, and alternating interlayers of both types. For the members of the first two groups, powder XRD patterns were calculated and criteria for distinguishing polytypes with the same number of layers per unit cell are suggested.
Stacking Order in a K/Mg Interstratified Vermiculite from Malawi
Authors: de la Calle C. , de Vidales J. L. Martin , Pons C. H. 
Published: August 2006

AbstractThe stacking order of a bi-ionic K/Mg vermiculite from Malawi (Nyasaland), has been determined from Weissenberg data. The sample corresponds to a K/Mg interstratified vermiculite containing 50% K layers (dK = 1.01 nm) and 50% Mg layers with two layers of water (dMg = 1.44 nm). The observed intensities along (0, 0), (h, 0), (0, k) and (1, k) reciprocal rods were compared to the calculated intensities given by model defect structures. It was found that: 1) The (h, 0), (0, k) and (1, k) rods reveal the interstratification phenomenon which was previously observed on the (0, 0) rod; 2) The exchange of Mg by K does not occur randomly in a single interlayer, but occurs in interlayer domains sufficiently extensive to allow the reorganisation of the layer stacking and development of the ordered K-vermiculite structure from the semi-ordered structure characteristic of magnesium vermiculites; 3) For this sample, the interlayer water of the Mg phase occurs in two coexisting configurations; one configuration has water molecules forming octahedral coordination around the Mg2+, the other has water which is not linked to the Mg2+ cation forming two planes.