bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fixing Cation Interaction with Blister-Like Osmotic Swelling on Vermiculite Cleavages
Authors: Sridhar K. , Jackson M. L. 
Published: September 2006

AbstractThe shrinkage of osmotically swollen natural and artificial blisters on vermiculite cleavages by exchange saturation with fixing cations such as Cs+, Rb+, NH4+, and K+ was investigated by replica electron microscopy. Incomplete collapse of either the natural or artificially produced blisters occurred with Cs+, Rb+, and NH4+ saturation, while K+ saturation completely collapsed the artificially produced blisters but not the natural blisters. The reason for incomplete collapse with Cs+, Rb+ and NH4+ was the incomplete replacement (trapping in the flakes) of interlayer hydrated cations such as Na+ shown by electron probe microanalysis. Much less trapping occurred with K+ saturation. Na+ entrapment increased with increasing size and decreasing hydration of cations, i.e. Cs+ >Rb+ >NH4+ >K+.Semiquantitative determination of Na+, by electron probe microanalysis, in vermiculite flakes near the edge revealed that 1 N CsCl entrapped as much as 45·6 per cent while 1 N KCl entrapped only 7·5 per cent. In general, more Na+ was entrapped by 1 N solutions than by dilute solutions. With 0·01 N KCl solution, the Na+ entrapment was only 4·4 per cent. The amount of Na+ at the center of the macroflakes was less than at the edge, apparently as a result of more CEC at frayed edges and (or) because of incomplete diffusion of Na+ to the center. Shrinkage of artificial blisters by K+ could thus be attributed to its more effective removal of the interlayer hydrated cations, whereas the other fixing cations were less effective. Natural blisters on vermiculite from Libby, Montana were not completely collapsed even by K+, apparently because the layer charge density was too low in the blister areas.
Properties of the Zeolite, Faujasite, Substitutional Series: A Review with New Data
Authors: Stamires Dennis N. 
Published: September 2006

AbstractNew information is presented relating to the hydrothermal stability, lattice parameters, and adsorptive, electrical, and catalytic properties of synthetic and natural faujasite. Present concepts concerning the nature and relationship of synthetic and natural faujasite are restated to be consistent with the experimental evidence and the developed physical model. The major structural and physicochemical properties reflect the close similarities and smooth gradations expected of substitutional members of a continuous series. The existing division of the range (2–6) of SiO2/Al2O3 mole ratios (S/A) at 3 into two compositional subranges is shown to be unjustifiable and rather misleading. Individual compositions from these two subranges do not represent distinctly different zeolite species; instead, it is demonstrated that they are members of a continuous series with smoothly changing properties over the studied range of SiO2/Al3O3. Some of the properties of the natural mineral faujasite are found to be very similar to those of the synthetic analogs with the same SiO2/Al2O3 mole ratio.Finally, a plea is made for a uniform nomenclature which will serve to identify specific (single) compositions (instead of ranges of compositions); reflect the continuity, close similarities and interrelationships in their main structural and physicochemical properties; and also identify the characteristics of the faujasite group.
Particle Size-Shape Relationships in Georgia Sedimentary Kaolins—II
Authors: Olivier J. P. , Sennett Paul 
Published: September 2006

AbstractCrude sedimentary kaolin clay from central Georgia, U.S.A., which had a wide distribution of particle size, was divided into several size fractions by repeated sedimentation in water. The resulting fractions had approximately a 2:1 ratio in dia. between their upper and lower limits. Each fraction was then studied by transmission and scanning electron microscopy and characterized in terms of surface area (both geometric and by gas adsorption), particle shape and impurity analysis.Particle diameter determined from measurements made on electron micrographs showed considerable deviation from the diameter obtained by Stokes sedimentation. This deviation was especially large for the coarser particles and could be explained by the microscopically observed porosity of the kaolinite booklets. Imperfect stacking of the crystallites within a kaolinite booklet leads to a moderately regular array of slit-like voids. Effective particle densities as low as about 1·6 have been observed. The pore structure was also investigated by use of mercury intrusion porosimetry.
Elementary Layers in the Interstratified Clay Minerals as Revealed by Electron Microscopy
Authors: Yoshida Tsunoru 
Published: September 2006

AbstractInterstratified layer structures were studied by electron microscopy and electron diffraction. In order to distinguish between expansible and non-expansible layers, Interstratified mica-smectite was treated with laurylamine hydrochloride solution. Electron micrographs of the layers at the curled edges of the crystals show expanded basal spacings of 24 Å and unexpanded spacings of 10 Å. It was observed that adjacent pairs of expanded and unexpanded layers in the micrographs form non-expansible units. Arrangement of the expanded and unexpanded layers shows that the layers expanded by sorption of laurylammonium ions have expansible and non-expansible surface characteristics on opposite sides of the layer. The relationships between the ratio of component layers and basal spacings in two component systems are discussed.
On the Mechanism of the Adsorption of Trace Copper by Bentonite
Authors: Steger H. F. 
Published: September 2006

AbstractThe adsorption of trace quantities of Cu (3·89 × 10−6 to 3·00 × 10−4 M) by a bentonite clay from calcium acetate solution was studied over the range of pH 4·27–5·87. The data were fitted to an existing adsorption equation and the ‘best’ values of the adsorption parameters were calculated. The proton, cupric ion and mono (hydroxy) cupric complex were found to be the adsorbed species. The adsorption sites are of two types. It has been postulated that the majority of sites are lattice hydroxyl groups located at crystal defects and edges. The remainder arise from organic matter adsorbed by the clay and are the more important in the adsorption of Cu at very low metal concentration and at pH <5·4. The implication of the results on the potential use of bentonite clay to remove trace amounts of Cu from mine waste waters is considered briefly.
Magnetic Behavior of Some Biotite Samples from West Thrace, N.E. Greece
Authors: Anagnostopoulos T. , Calamiotou M. , Sideris C. 
Published: September 2006

AbstractThe magnetic behavior of some biotite samples, from volcanic rocks of W. Thrace area, N.E. Greece, was studied in the temperature range from 85 to 270°K and compared with the chemical composition. The magnetization of the samples depends linearly on the applied field, and the magnetic susceptibility obeys the Curie law, showing a typical paramagnetic behavior which is due to Fe2+, Fe3+ and Mn2+ The effective magnetic moment was calculated from the structural formulas of the samples and deviation from the experimental values is discussed.
The Crystal Structure of the Dioctahedral Mica 2M2 Determined by High Voltage Electron Diffraction
Authors: Zhoukhlistov A. P. , Zvyagin B. B. , Soboleva S. V. , Fedotov A. F. 
Published: September 2006

AbstractThe structure of a dioctahedral 2M2 mica was defined by high voltage electron diffraction. The cell parameters are: a = 8·965, b = 5·175, c = 20·31 Å, β = 100° 40′, Z = 4, space group C2/c. Despite the peculiar character of the layer disposition (σ4 σ5 σ4 σ5), the oxygens of the layers are packed according to the cubic law. Consequently, the interlayer cations K have a trigonal prismatic coordination. The angle of tetrahedral twist is 11° 20′. The interatomic distances T-O indicate ordered replacements of Al for Si.
Argillization by Descending Acid at Steamboat Springs, Nevada
Authors: Schoen Robert , White Donald E. , Hemley J. J. 
Published: September 2006

AbstractSteamboat Springs, Nevada, an area of present-day hot springs, clearly illustrates the genetic dependence of some kaolin deposits on hot-spring activity. Andesite, granodiorite and arkosic sediments are locally altered at the land surface to siliceous residues consisting of primary quartz and anatase, plus opal from primary silicates. These siliceous residues commonly exhibit the textural and structural features of their unaltered equivalents. Beneath the siliceous residues, kaolin and alunite replace primary silicates and fill open spaces, forming a blanketlike deposit. Beneath the kaolin-alunite zone, montmorillonite, commonly accompanied by pyrite, replaces the primary silicates. On the ground surface, the same alteration mineral zones can be traced outward from the siliceous residue; however, hematite rather than pyrite accompanies montmorillonite.Chemical analysis indicates that sulfuric acid is the active altering agent. The acid forms from hydrogen sulfide that exsolves from deep thermal water, rises above the water table and is oxidized by sulfur-oxidizing bacteria living near the ground surface. This acid dissolves in precipitation or condensed water vapor and percolates downward destroying most of the primary minerals producing a siliceous residue. Coincidence of the water table with the downward transition from siliceous residue to kaolin-alunite signifies decreasing hydrogen metasomatism because of dilution of descending acid by ground water.In hot-spring areas, beds of siliceous sinter deposited at the surface by hypogene thermal water look, superficially, like areas of surficial acid alteration. Features diagnostic of a surficial alteration are the relict rock structures of a siliceous residue and a kaolin-alunite zone immediately beneath.
Interlamellar Adsorption of Carbon Dioxide by Smectites
Authors: Fripiat J. J. , Cruz M. I. , Bohor B. F. , Thomas Josephus 
Published: September 2006

AbstractThe adsorption of CO2 at low temperature (~ -70°C) on thin films of homoionic smectites was studied by X-ray diffraction and by i.r. absorption. An increase in the d001 spacings of these clay films upon adsorption of CO2 was observed. In addition, a dichroic effect was readily discernible by comparing the i.r. spectra at two different orientations of the smectite films; i.e. with the film normal and tilted 35° with respect to the i.r. beam. The CO2 stretching vibration at 2350 cm-1 was used for the i.r. study. These observations conclusively show that CO2 intercalates the smectite structure rather than being adsorbed only in pores between clay tactoids—the limiting process proposed by other investigators.Adsorption isotherm data from earlier surface area studies are re-examined here through application of the Dubinin equation. Again, intercalation is demonstrated by convergence of the plotted experimental data for smectites containing large monovalent interlayer cations toward a pore volume that is near the calculated theoretical value for a monolayer of intercalated CO2.Scanning electron photomicrographs of Li- and Cs- smectites provide additional evidence that aggregation differences are not responsible for the large observed difference in BET surface areas obtained for these smectites with CO2 as the adsorbate. At low magnification, visual differences in macro-aggregates are apparent, but at high magnification no significant differences are observed in the micro-structure of individual aggregates where the major amount of gas adsorption really occurs.
The Interaction of Water with Goethite (α-FeOOH) and Amorphous Hydrated Ferric Oxide Surfaces
Authors: Gast Robert G. , Landa Edward R. , Meyer Gordon W. 
Published: September 2006

AbstractThe interaction of water with synthetically prepared goethite (α-FeOOH) and amorphous hyd-rated ferric oxide surfaces was studied using i.r. absorption and water vapor adsorption measurements. I.R. results show that the last traces of physically adsorbed water are removed from the amorphous material by outgassing at 25°C. In contrast, goethite retains approximately a monolayer of physically adsorbed water with similar outgassing. This monolayer of water on goethite, which is presumably hydrogen-bonded at least in part with structural hydroxyls, is readily exchangeable with D2O.Integral entropies of adsorption were evaluated from water vapor adsorption isotherms at 15, 25 and 35°C and compared with values for mobile and immobile layers calculated through application of statistical mechanics (McCafferty and Zettlemoyer, 1970). Entropy values for both the first physically adsorbed monolayer of water on the amorphous material and the second monolayer on goethite were about the same as or greater than those calculated for an immobile layer, indicating strong hydrogen bonding of water by both surfaces. The larger deviation between the entropy values for goethite and those calculated for the immobile layer may be associated with changes in the structure of the first as well as the second physically adsorbed water layers. Surface areas, calculated using the BET method, were 320 and 32 m2 g-1 for the amorphous material and goethite respectively. Since the unit surface activity is probably about the same for the two materials, it follows that as the amorphous material crystallizes to form goethite, there would be a reduction in total surface activity in proportion to the reduction in surface area.
Potassium Selectivity of Clays as Affected by the State of Oxidation of Their Crystal Structure Iron
Authors: Kishk Fawzy M. , El-Sheemy H. M. 
Published: September 2006

AbstractThe Ca-K exchange isotherms were determined at two temperatures for two highly montmorillonitic iron-rich soil clays in their oxidized and reduced states. The thermodynamic parameters K, ΔG0, ΔH0 and ΔS0 were calculated for the exchange reactions.It was found that the formation of K-clay from Ca-clay in both the oxidized and reduced state was accompanied by negative free energy, enthalpy and entropy changes. The results indicate that K is more strongly bound than Ca by the clay and the Ca-preference shown by the isotherms may be due to entropy changes in solution.The oxidation of crystal structure iron resulted in an increase in K selectivity of the clay and a decrease in the free energy, enthalpy and entropy changes of the Ca-K exchange reaction. It was concluded that K is more strongly held by the oxidized clay than the reduced one, which is possibly due to a more nearly dioctahedral character in the oxidized than in the reduced state.
Similarities of Rehydration and Rehydroxylation Properties of Rectorite and 2M Clay Micas
Authors: Tomita Katsutoshi 
Published: September 2006

AbstractVarious dehydroxylated micas and rectorites were acid-treated. Rectorite-type mixed-layer mineral was formed from 2M1 and 2M2 mica and random mixed-layer mineral from 1M and 1Md mica. Rectorite was formed again from dehydroxylated rectorite. The rehydration and rehydroxylation properties of dehydroxylated rectorite and 2M sericites were found to be similar.
Infrared Absorption and X-Ray Diffraction Study of Butylammonium Complexes of Phyllosilicates
Authors: Martin-Rubi J. A. , Rausell-Colom J. A. , Serratosa J. M. 
Published: September 2006

AbstractI.R. absorption and X-ray diffraction data on butylammonium complexes of vermiculites show, when compared with the Wyoming montmorillonite complex, that the tetrahedral location of charge determines the keying of the -NH+3 groups into the ditrigonal cavities and that these groups have their C3 axes perpendicular to the layers. The aliphatic chains adopt different conformations depending on the area available per exchange position; they will either: (a) adopt an ’all-trans’ conformation with their axes inclined 55° to the silicate planes, when the area available is small; (b) rotate 120° around the C1-C2 bond to adopt a flat disposition relative to the layers, when the area available is larger than the area covered by the organic ion.
A Structural Investigation of a Vermiculite-Piperidine Complex
Authors: Iglesias J. E. , Steinfink H. 
Published: September 2006

AbstractA vermiculite-piperidine complex was investigated by a single crystal three dimensional X-ray diffraction procedure. The complex was prepared by ion exchange of a Na-vermiculite at pH 8. A total of 453 reflections was observed and used in the least squares refinement of the structure. The complex is monoclinic, C2/m, a = 5.346(2) Å, b = 9.256(3) Å, c = 17.57(1) Å, ß = 96.29(9)°. The final R value was 0.17 using anisotropic temperature factors for the silicate atoms and isotropic temperature factors for the carbon atoms. The occupancy factors of the C atoms were considered as variable parameters. The diffraction data were of poor quality because of stacking faults. The results show that the molecules are randomly distributed over the crystallographic sites in the interlayer space and the peaks appearing in the electron density maps can be interpreted as being due to 2 piperidine molecules and two H2O molecules. The orientation of the organic molecules is ambiguous. The electron density peaks fit a model in which the molecules are vertical and their planes form a small dihedral angle, and also fit a model in which the plane of the molecules is parallel to (001). It is quite possible that both types of orientations are present.
Further Investigations on Fulvic Acid-Cu2+-Montmorillonite Interactions
Authors: Kodama H. , Schnitzer M. 
Published: September 2006

AbstractThe major mechanism by which fulvic acid removed Cu2+ from Cu2+-montmorillonite was complexation, most likely chelation. This was confirmed by the use of a specific cupric ion electrode which showed that whereas the total Cu2 + concentration in the supernatant solutions increased with rise in pH, about 7 per cent of the total Cu2+ solubilized by fulvic acid occurred in the ‘free’ or ‘uncomplexed’ form at pH 2.5, only 0.6 per cent was similarly distributed at pH 4.5 and 0.0009 per cent at pH 6.5. External surface area measurements by a dynamic BET method showed the following surface areas: 2.5 m2g-1 for the fulvic acid, 8.0 m2 g-1 for the Cu2+-montmorillonite but 16.1 m2 g-1 for the FA-Cu2+-montmor-illonite complex. Electron micrographs of the FA-clay complex confirmed that fulvic acid was adsorbed in interlamellar spaces and on external surfaces of the Cu2+-montmorillonite.
Internal and External Morphology of Tubular and Spheroidal Halloysite Particles
Authors: Dixon J. B. , Mckee T. R. 
Published: September 2006

AbstractTubular halloysite from Wagon Wheel Gap, Colorado and spheroidal halloysite from Redwood County, Minnesota were examined by transmission electron microscopy. Clay samples were prepared by the following techniques: drop-mounted suspension on carbon support films; thin sections of clay in Araldite epoxy resin; and carbon-platinum-palladium single-stage replicas.Both types of dehydrated halloysite have interlayer separations between packets of layers. Halloysite tubes are composed of packets as thin as five layers which sometimes reveal a rolled interior configuration in cross-sectional view. Thicker tubes are composed of many layers per packet. Some large tubes appear in cross section as folded packets of layers. The interior morphology of spheroidal halloysite particles is more irregular and the layer structure is more discontinuous than in most tubes. The spheroidal halloysite of this study is characterized by external tangential plates with hexagonal shape suggestive of kaolinite.
Gas Sorption in Clay Mineral Systems
Authors: Aylmore L. A. G. 
Published: September 2006

AbstractSorption isotherms for four gases (N2, A, Kr and CO2), commonly used in specific surface area and pore structure measurements, have been accurately determined on a number of clay mineral and oxide systems.Specific surface areas obtained by application of the BET theory to these isotherms illustrate the extent to which the apparent cross-sectional areas for these sorbed gases vary with surface structure, exchangeable cation and microporosity.V-n plots for nitrogen adsorption on these materials using nitrogen adsorption on crystalline materials of large crystal size as a standard isotherm provide appreciable ranges of linearity in each case. The specific surface areas obtained from these straight line plots agree well with the corresponding BET values. The linearity of these plots for illite clays indicates the absence of capillary condensation and that adsorption in slit-shaped pores takes place largely by the formation of physically adsorbed layers on the surfaces.Much larger BET specific surface areas were obtained from carbon dioxide sorption at 196 K on goethite, hematite and gibbsite than from nitrogen, argon and krypton sorption at 78°K. It is suggested that enhanced sorption of CO2 into microporous regions of the oxides, inaccessible to the other gases. occurs in a similar fashion to that frequently observed for coal and charcoal materials. V-n plots for CO2 sorption in these materials using that for an illite clay as a standard isotherm, support this conclusion.Considerably lower BET specific surface areas were obtained for CO2 sorption on kaolinite than were obtained for nitrogen, argon and krypton sorption. The shape of the V-n plots for CO2 sorption on kaolinite compared with illite suggest that an initial specific adsorption of CO2 on the kaolinite is followed by a change in state with the completion of this layer, allowing normal multilayer formation to proceed.
A Preparative Technique for Electron Microscopic Examination of Colloid Particles
Authors: Greene R. S. B. , Murphy P. J. , Posner A. M. , Quirk J. P. 
Published: September 2006

AbstractAdsorption of clay particles from very dilute aqueous suspensions onto positively charged films (Cytochrome C) on carbon coated support grids has been used to obtain well dispersed samples of the particles suitable for detailed electron microscopic examination. The natural negative charge of the carbon coated grid was used for ferric polycations and precipitates.
Hydrothermal Origin of the Clays from the Upper Slopes of Mauna Kea, Hawaii
Authors: Ugolini F. C. 
Published: September 2006

AbstractThe soils of the summit region of Mauna Kea are similar to the soils of the high mountain deserts and to the soils of cold deserts. Dramatic differences, however, exist between the soils of the summit and other neighboring cones and the soils of the glaciated terrain. The soils of some of the cones of the summit area are clay rich and contain phyllosilicate minerals; the soils of the glaciated terrain are sandy and contain X-ray amorphous clay. Montmorillonite and a Mg-rich trioctahedral mineral identified as saponite are the clay minerals of the summit. Because the summit area of Mauna Kea supported an ice cap at the time of the formation of the cones, the origin of the smectite minerals could have resulted from the alteration of the tephra by steam and water released in the melting of the ice. Hypogene fluids are, however, more likely to be responsible for the genesis of the phyllosilicate minerals.