bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Calcium and Sodium Concentration on the Microstructure of Bentonite and Kaolin
Authors: Stawiński Janusz , Wierzchoś Jacek , Garoa-Gonzalez Maria Teresa 
Published: August 2006

AbstractThe influence of added sodium and calcium nitrate electrolyte on the particle aggregates in the colloid fraction of natural bentonite and kaolin was studied. Clays were flocculated in distilled water and various electrolyte concentrations. Aggregate size was studied by sedimentation analysis; the mean radius of the aggregates was plotted against the concentrations of Na+ and Ca2+. For bentonite, the mean radii decreased with an increase of Na+ and Ca2+ concentration, reaching a minimum; and further increases in concentration led to an increase of the mean radii of the aggregates. For kaolin, an increase in Na+ and Ca2+ concentration gave rise to an increase in the mean radii of aggregates.Scanning electron micrographs showed different types of aggregates, depending on the physico-chemical conditions of a sedimentation process. In bentonite and kaolin sediments formed from a distilled water slurry, the dominant aggregate was an edge-face type. The small addition of salts to a bentonite slurry led to the formation of edge-edge-type aggregates; for kaolin edge-face-type aggregates formed, although within the microaggregate face-face associations were observed. The highest concentrations of electrolytes for sediments of both clays led to formation of compact, face-face-type aggregates.
High-Resolution Transmission Electron Microscopy Study of Mn-Oxyhydroxide Transformations and Accompanying Phases in a Lateritic Profile of Moanda, Gabon
Authors: Amouric M. , Parc S. , Nahon D. 
Published: August 2006

AbstractUnheated natural mixtures of manganite and secondary pyrolusite, from the same lateritic manganiferous sequence, were studied in different orientations by high-resolution transmission electron microscopy (HRTEM), electron diffraction, and energy-dispersive X-ray analysis (EDX) to determine the fine structure of these phases, their possible crystallographic relations, and the genetic processes that led to the formation of the pyrolusite. Typical palisadic texture was observed for both minerals. Characteristic cracks parallel t. (010) of the pyrolusite structure and in particular <210> microfissures in manganite were noted as signs of structural accommodation accompanying the transformation phenomenon between these two minerals. A previously unreported manganese oxide of the spinel-type (γ-Mn2O3 or Mn3O4) was also identified in the original mixture. This oxide gave pure microdomains as intergrowths with pyrolusite adjacent to manganite. This is the first report of a natural occurrence of γ-Mn2O3. The manganite-pyrolusite transformation process and an unsuspected γ-Mn2O3 (Mn3O4)-pyrolusite transition were directly illustrated in detail for the first time. Interfaces between the concerned phases were not sharp or smooth, but exhibited strong strain contrasts and interferential periodicities. Lattice images and microdiffraction patterns proved that both transformations were oriented, suggestive of topotactic relations. In addition, the principal minerals in the matrix (illite, kaolinite, and goethite) were examined for a better understanding of their role in Mn-oxyhydroxides transformations.
Assignment of the Far-Infrared Absorption Bands of K in Micas
Authors: Laperche V. , Prost R. 
Published: August 2006

AbstractTo identify the far-infrared (FIR) absorption bands related to K cations in micas, spectra of muscovite, phlogopite, and biotite were compared with the spectra of pyrophyllite and talc, which have no compensating cations, and to the spectra of micas in which K is substituted by mono- and divalent cations. Dichroic experiments using single crystals of these micas showed that some of the bands or components related to K have a strong in-plane and out-of-plane dichroic character. These experimental data led to the assignment of the FIR bands at 110, 91, and 83 cm−1 for muscovite, phlogopite, and biotite, respectively, which have no in-plane and out-of-plane dichroic character, to the vibration of the double ring of oxygen atoms that constitutes the cage in which K is located (mode III).Bands at 146, 136, and 152 cm−1 for muscovite, phlogopite, and biotite, respectively, which have a strong out-of-plane dichroic character, were assigned to the out-of-plane vibrations of K atoms (mode IV). Some of the components at 190, 158–153, and 145–124 cm−1 for muscovite, phlogopite, and biotite, respectively, which have a strong in-plane dichroic character, are possibly related to the in-plane vibrations of K atoms (modes I and II). The 165-cm−1 band of muscovite is a lattice mode of vibration. Frequencies of modes III and IV of the compensating cations of micas in which K was substituted by mono- and divalent cations exchanged as a function of Z/m where Z is the charge and m the mass of the cation. Modes III and IV were well resolved and very sensitive to the crystallochemical properties of the structure (di- or trioctahedral character, Fe content, etc.). FIR spectroscopy may therefore be an important tool that uses compensating cations as probes to study the interactions between the cations and the structure of mica minerals.
The Effect of Heat Treatments on the Total Charge and Exchangeable Cations of Ca-, Na-, and Li-Saturated Kaolinite
Authors: Pennell Kurt D. , Rhue R. Dean , Harris Willie G. 
Published: August 2006

AbstractThe effect of heat treatments on the total charge and water adsorption by Ca-, Na- and Li-saturated kaolinite was studied using extraction techniques and thermal gravimetric analysis, respectively. Measurements of cation exchange capacity indicated that the total charge of Li-kaolinite was reduced by approximately 50% after heating to 110 or 130°C. In contrast, the total charge of Ca-kaolinite remained essentially constant while that of Na-kaolinite decreased slightly. Water adsorption and desorption on Ca- and Li-kaolinite following heat treatments at 150°C were consistent with the total charge of the respective kaolinites. Ion extraction of Li-kaolinite using NH4C1 revealed that only 6% of the Li remained exchangeable after heating, while Al and H were released. Thus, non-exchangeable Li ions not only reduced the total charge of the kaolinite but also displaced Al and H from the kaolinite structure. Infrared spectroscopy also indicated that Li migrated into the kaolinite structure and replaced a portion of the Al from the octahedral sheet. The results presented here indicate that Li-kaolinite represents a surface of reduced charge rather than a surface free of cation-hydration effects. Therefore, Li-kaolinite is not recommended as a reference for the study of vapor-phase adsorption, and conclusions based on such a reference material should be reevaluated.
The Structure and Thermal Transformations of Allophanes Studied by 29Si and 27Al High Resolution Solid-State NMR
Authors: MacKenzie K. J. D. , Bowden M. E. , Meinhold R. H. 
Published: August 2006

AbstractExamination of two volcanic and two precipitated allophanes by solid-state NMR, thermal analysis and X-ray powder diffraction shows three of the samples to contain structural features similar to both tubular imogolite and defect layer-lattice aluminosilicates such as kaolinite. The fourth allophane, a precipitated sample from New Zealand, had no imogolite-like features and contained tetrahedral as well as octahedral aluminum. The imogolite-like units in allophane are less stable thermally than tubular imogolite. The NMR spectra and their changes on heating can be accounted for by a structural model in which a two-sheet, kaolinite-like structure containing defects (holes in the tetrahedral sheet) is curved into a sphere in which imogolite-like orthosilicate units are anchored into the octahedral sheet and fit into the tetrahedral defects. Computer simulation shows that the model is crystallographically sound, and accounts for all the known facts, including the spherical morphology, the solid-state NMR spectra and the thermal dehydroxylation behavior of all except the New Zealand allophane, which is of a different structural type.
Porosimetry Measurement of Shale Fabric and Its Relationship to Illite/Smectite Diagenesis
Authors: Howard James J. 
Published: August 2006

AbstractThe extent of illite/smectite (I/S) reactions is linked with quantitative measurements of shale fabric in a suite of samples from a lower Frio Formation well. Greater illitization of the I/S clays is found in laminated shales that possess a larger pore surface area/pore volume (SA/V) of 3.21 × 106 cm−1 than the adjacent massive shale lithofacies with a SA/V of 1.97 × 106 cm−1. Mean pore diameter in both shale lithologies is 0.0145 micrometers, though in the laminated shale distributions are skewed towards more smaller-sized pores. While no direct permeability measurements were made, estimates of permeability that are based on simple physical models using SA/V suggest that lower permeabilities are associated with laminated shales. The trend of greater illitization at higher SA/V values is contrary to expectations that reaction extent is enhanced by greater permeabilities, such as created by silt laminations in shale. The limitations of estimated permeabilities emphasize that porosimetry measurements of shale fabric are useful for estimating the access of material to all reaction sites, and do not just describe the effect of a few large pores that dominate permeability. Greater reaction extent in the laminated shales is associated with the accessibility of fluids to more pore space than in the massive shales.
Adsorption of Citric Acid by Synthetic Pseudoboehmite
Authors: Cambier P. , Sposito Garrison 
Published: August 2006

AbstractThe adsorption of citrate, at 10 4−10−3 M initial concentration, by pseudoboehmite suspended in 0.02 M NaC1O4 was investigated at varying pH. Citrate shows a strong affinity for the pseudoboehmite surface, as seen in the adsorption isotherm at pH 6. Adsorption envelopes of adsorbed citrate vs. pH for a given initial citrate concentration are characteristic for the adsorption of a polyprotic acid by a variable-charge mineral. The envelope data were fit well by the Constant Capacitance Model assuming a ligand-exchange adsorption mechanism, three monodentate surface species of citrate, and a reactive surface OH density of 0.4 mol kg−1. Aqueous speciation calculations suggest that solubility equilibrium with pseudoboehmite was attained at pH > 9 and that particulate or polymeric Al may have existed at 6 < pH < 9. Dissolved Al appeared to reduce the adsorption of citrate at pH < 5.5 via solution complexation reactions.
Synthesis of 1:1 And 2:1 Iron Phyllosilicates and Characterization of Their Iron State by Mössbauer Spectroscopy
Authors: Mizutani Tadashi , Fukushima Yoshiaki , Okada Akane , Kamigaito Osami , Kobayashi Takayuki 
Published: August 2006

AbstractIron phyllosilicates with 1:1 and 2:1 layer structures were prepared from silicic acid, ferrous sulfate and sodium hydroxide. Hydrothermal treatment at 100–200°C of a reaction mixture with an initial Fe/Si ratio of 1.5 gave the 2:1 iron phyllosilicate, whereas a Fe/Si ratio of 2.25 gave the 1:1 phyllosilicate. The 57Fe Mössbauer spectroscopy showed that 60% of the iron in the 1:1 phyllosilicate is ferrous, versus only 3% in the 2:1 phyllosilicate. The values of quadrupole coupling showed that the iron-oxygen tetrahedra and octahedra in the 2:1 phyllosilicate were more deformed than those in the 1:1 phyllosilicate.
Ammonium Substitution in Illite During Maturation of Organic Matter
Authors: Williams Lynda B. , Ferrell Ray E. 
Published: August 2006

AbstractPierre shale samples from a thin stratigraphic zone within the contact aureole of the lamprophyric Waisen dike record changes due to thermal effects that are not influenced by detrital differences. Analyses of fixed-NH4, mineralogy, and Rock-Eval pyrolysis indicators of organic matter maturity provide new insights on the fixation process. Fixed-NH4increases with the quantity of authigenic illite formed from illite/smectite, but the maximum fixation per unit of illite formed occurs within the “oil window” where thermal breakdown of organic matter is rapid. Extrapolation of these results to the burial diagenetic regime supports the potential use of fixed-NH4as an indicator of organic maturity and hydrocarbon migration pathways.
Chemiographic Analysis of Trioctahedral Smectite-to-Chlorite Conversion Series from the Ohyu Caldera, Japan
Authors: Meunier A. , Inoue A. , Beaufort D. 
Published: August 2006

AbstractThe chemical compositions of chlorite-smectite mixed-layered minerals (C/S) from the Ohyu caldera (Inoue, 1985) are analyzed using M+-4Si-3R2+ diagrams. The assumed original saponite has the following composition: Si3.54Al0.46O10Al0.173Fe2+1.385Mg1.295Mn0.02(OH)2M+0.56. Random C/S minerals (100 to 80% expandable layers) are interpreted as an interstratification of the starting 2:1 smectite layer with a A1XR2+3−x interlayer. The 2:1 smectite layer charge remains constant but Ca, Na, K cations are replaced by a Al-R2+ complex ion. The brucitic layer (produced by the polymerization of the complex ions) and the 2:1 smectite layer form a 14 Å non-expandable phase having a composition different from a true chlorite.The true chlorite layers first appear in the ordered (corrensite) phase composed of a high charge saponite: Si3.35A10.65O10R2+3(OH)2M+0.65 and an octahedral vacancy-free chlorite Si2.90A11.10O10Al1.10R2+4.90(OH)8. The recrystallization of the original trioctahedral smectite into a high-charge saponite decreases the b-dimension difference with the chlorite component.From these data, it is suggested that the trioctahedral smectite-to-chlorite conversion is controlled by three reactions: 1. fixation and polymerization of Al-R2+ complex ions in the interlayer region of the original smectite producing a 14 Å non-expandable phase (the interlayering of this phase with the original smectite gives the randomly interstratified C/S mineral. 2. dissolution of these random mixed-layered minerals and precipitation of corrensite. 3. dissolution of corrensite and growth of Fe-rich chlorite.
Transformation of 1-Aminonapththalene at the Surface of Smectite Clays
Authors: Ainsworth Calvin C. , McVeety Bruce D. , Smith Steven C. , Zachara John M. 
Published: August 2006

AbstractOne-aminonaphthalene is sorbed onto the Na-saturated smectite clays, montmorillonite and hectorite, by cation exchange. In the presence of Fe3+, either in the clay structure or on the clay surface, sorption is followed by the formation of a blue-colored complex, with the continuous disappearance of aminonaphthalene from solution and the clay surface. The rate of aminonaphthalene disappearance decreases as pH increases. With time, four major products that appear to be structural isomers of N(4-aminonaphthyl)-l-naphthylamine are produced. A simplified model of this transformation is suggested to be the oxidation by Fe3+of sorbed aminonaphthalene forming a radical cation-clay complex. A subsequent reaction between the radical-cation and a neutral aminonaphthalene molecule takes place, with the products being strongly sorbed to the clay surface.
57Fe Mössbauer Spectroscopic Study of Structural Changes during Dehydration of Nontronite: Effect of Different Exchangeable Cations
Authors: Luca Vittorio 
Published: August 2006

AbstractDehydration-induced migration of different exchangeable cations toward the layers of nontronite has been studied by Mössbauer spectroscopy. As interlayer water is removed exchangeable cations migrate toward Fe3+ sites in the tetrahedral sheets of the nontronite (IvFe3+) causing them to distort. The amount of distortion is linearly related to the ionic potential (IP) of the exchangeable cations and is greatest for cations with highest IP. Octahedral Fe3+ sites (VIFe3+) are also affected by migration of cations into the pseudohexagonal cavities. As exchangeable cations move into the pseudohexagonal cavities, interaction with VIFe3+ sites increases. The intensity of the outer VIFe3+ Mössbauer doublet increases with respect to the inner VIFe3+ doublet as the IP of the exchangeable cation increases. It appears that the exchangeable cations play a significant role in determining the thermal stability of nontronite.
Chemical Characterization, Structural Features, and Thermal Behavior of Sodium and Hydrogen Octosilicate
Authors: Borbély G. , Beyer H. K. , Karge H. G. , Schwieger W. , Brandt A. , Bergk K.-H. 
Published: August 2006

AbstractThe chemical composition and the thermal behavior of sodium and hydrogen octosilicate was studied by chemical and thermal analysis, infrared (IR), magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and X-ray diffractometry. Both compounds are layer silicates with basal spacings of 11.10 and 7.38 Å, respectively. In both forms the ratio of Q4 silicon (connected via oxygen bridges with four silicon atoms) to Q3 silicon (connected with only three other Si atoms) is 1. At least a small part of the Q4 silicon can be substituted by aluminum. Elimination of water coordinated to the cations in sodium octosilicate results in a concomitant structural collapse. Replacement of the sodium ions by protons affects the atomic arrangement in the sheets only to a minor degree, but results in a decrease of the periodicity along the crystallographic c axis. Upon heat treatment an endothermal structural rearrangement occurs at about 360 K as revealed by significant changes of the IR and 29Si MAS-NMR spectra. Reexchange with Na ions largely, but not completely, restores the structure of the parent octosilicate.The X-ray diffraction pattern of sodium octosilicate was indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 11.25 Å and β = 99.3°. Based on conclusions drawn from the results of the present study, the X-ray pattern of hydrogen octosilicate was tentatively indexed in the monoclinic system with a = 7.345 Å, b = 12.74 Å, c = 8.51 Å and β = 119.8°.
Extraction of Iron Oxides from Sediments Using Reductive Dissolution by Titanium(III)
Authors: Ryan Joseph N. , Gschwend Philip M. 
Published: August 2006

AbstractA new iron oxide dissolution method designed to measure the abundance of “free” Fe oxide phases and associated elements in soils and sediments has been tested. The method employs a ternary complex of Ti(III), citrate, and ethylenediaminetetraacetate (EDTA) as a reductant and bicarbonate as a proton acceptor. The Ti(III)-citrate-EDTA-HCO3method dissolved more synthetic amorphous ferric oxide and goethite, but less synthetic hematite, than the dithionite-citrate-HCO3method of Mehra and Jackson. The production of acidity by the dissolution indicated that Ti(IV) is hydrolyzed to TiO2during the extractions. The heated dithionite method dissolved 3–6 times more Al from kaolinite and nontronite standard clays than room temperature dithionite, and 4–6 times more Al than the Ti(III)-citrate-EDTA-HCO3method. Furthermore, the release of Fe from the clay mineral samples consistently and rapidly reached a plateau during multiple extractions by the Ti(III)-citrate-EDTA-HCO3method, indicating that a well-defined Fe oxide fraction was removed. Fe released by the dithionite method continued to increase with each extraction, suggesting that some release of structural Fe occurred. Tests on two natural sediments and one heavy mineral fraction from the Miocene Cohansey Sand in the New Jersey Coastal Plain suggested that the Ti(III)-citrate-EDTA-HCO3method removed Fe oxides more effectively and more selectively than the dithionite method. The selectivity of the Ti(III)-citrate-EDTA-HCO3method is enhanced by rapid extractions at room temperature and low free ligand concentrations.
Transmission Electron Microscope Observations of Illite Polytypism
Authors: Baxter Grubb Susan M. , Peacor Donald R. , Jiang Wei-Teh 
Published: August 2006

AbstractTransmission electron microscopy (TEM), including selected area electron diffraction (SAED), has been used to identify polytypes in illite, phengite and muscovite from samples representing a wide range of diagenesis and low-temperature metamorphism. Samples include Gulf Coast sediments, sediments from the Salton Sea region, California, the Martinsburg Formation at Lehigh Gap, Pennsylvania, the Kalkberg Formation at Catskill, New York, Otago Schists from southern New Zealand, pelites from the Gaspé Peninsula in Quebec, Canada, shales and slates from Wales, sediments from the Barbados accretionary complex, and synthetic hydrothermal illite.Samples from rocks of lowest grades, including those representing a range of sedimentary diagenesis, invariably give SAED patterns with few, complex non-00l reflections which are diffuse and ill-defined and that represent largely disordered stacking sequences. Corresponding XRD patterns are consistent with 1Md polytypism. The term 1Md is therefore retained for this material. Higher grade samples, including those in which slaty cleavage is developed, and detrital grains in low-grade sediments invariably give diffraction patterns of well-ordered 2- or 3-layer polytypes. Of all samples and localities studied, only one diffraction pattern, from a sample in the Gaspé sequence, was found to be predominantly 1M. In none of the other sequences included in this study were any 1M or predominantly 1M electron diffraction patterns obtained for illite grains.Where illite is in its original state of formation, it is consistently 1Md, whether it originates as a result of direct crystallization from solution or as a replacement of smectite. Where illite has apparently undergone subsequent change, presumably through dissolution and crystallization representing an Ostwald-step-rule-like change, it occurs as a well-ordered 2-layer (inferred to be 2M1) or, less commonly, a 3T polytype. On the basis of this limited survey, the state of polytypism appears to directly identify illite as either being in, or changed from, its initial state of formation.
Chlorite Vermiculitization and Pyroxene Etching in an Aeolian Periglacial Sand Dune, Allen County, Indiana
Authors: Argast Scott 
Published: August 2006

AbstractWeathering has etched and deeply-denticulated the constituent orthopyroxenes, and chlorite has been transformed to vermiculite in the upper 3 m of an aeolian, periglacial sand dune formed in northeastern Indiana about 13,000 b.p. Pyroxene weathering begins with the development of cleavage-parallel etch pits on {010} and {100} surfaces. These pits coalesce and eventually crop out on basal surfaces as denticulations. The mean denticulation size increases logarithmically toward the surface, and the denticulation size of the orthopyroxenes is a quantifiable feature of the weathering process. Ferruginous pendants, microboxworks of iron oxides, and other indications of iron redeposition within the ortho-pyroxene microenvironments were not observed.Chlorite in the dune has been weathered to vermiculite. The parent chlorite is a high-Fe variety, and the transformation to vermiculate does not involve the development of a chlorite/vermiculite intermediary phase. Fe2+ is oxidized as part of the transformation process and this iron is retained in the sediment as discrete goethite and as crystalline and noncrystalline coatings on the dune grains. The vermiculite from depths shallower than 64 cm is only partly expandable and is completely collapsed by K-saturation or heat treatment. This is a hydroxy-Al vermiculite and its formation is typical of intense weathering under the acid conditions prevalent at the dune surface.