bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clay-Organic Molecule Interactions: Oxidation of Acetaldehyde by Montmorillonite in N2 Atmosphere at Room Temperature
Authors: Eltantawy I. M. , Baverez M. 
Published: August 2006

AbstractOxidation of acetaldehyde molecules adsorbed on Na- and Mg-Wyoming montmorillonite at room temperature (20-25°C) and in N2 atmosphere has been studied by I.R. spectroscopy, A comparison between clay-acetic acid complex and that prepared from acetaldehyde is given. The influence of the nature of the saturating cation as well as the clay pretreatment on this oxidation process are discussed and reaction pathways are proposed. Acetic acid directly adsorbed on the clay surface is almost removed at 110°C, while that produced from the oxidation of the adsorbed acetaldehyde appears to be strongly held. Within a temperature range 180-230°C, the fixed acetic acid molecules dissociate to acetate form; then occurs an interaction of the acetate and the residual acid with the lattice OH of the clay at 200–300°C. This interaction involves the loss of the structural OH and deposition of carbon on the clay surfaces. The thermal decomposition of the residual complex is almost completed at 500–600°C
Kaolinite Synthesis. II. A Review and Discussion of the Factors Influencing the Rate Process
Authors: Van Oosterwyck-Gastuche M. C. , La Iglesia A. 
Published: August 2006

AbstractKaolinite is synthesized in approximately the same time in three temperature ranges: (1) from 200–250° to 350–400° (hydrothermal processes); (2) from 120 to 175° (semihydrothermal ones); (3) at ordinary temperature. It is thus evident that the rate process cannot be explained by the Arrhenius equation only, but is explained well by considering that kaolinite formation obeys the laws of crystal growth. It occurs only in slightly supersaturated solutions in which the nucleation process is possible and in which a slow and regular rate of growth has been insured. Concentrations calculated from the thermodynamical equilibria correspond to those of the experimental conditions for the low temperature processes. For the higher temperature ones, a similar relationship is delineated, at least as far as the thermodynamical treatment can be carried out.
Equilibration of Clays in Natural and Simulated Bottom-Sediment Environments
Authors: Photon F. E. , Smeck N. E. 
Published: August 2006

AbstractTo identify mineral alterations which might occur in stream environments, predominantly illitic soil clays were equilibrated in bottom sediment environments under natural and laboratory conditions for 217 and 98 days, respectively. Changes occurring after 217 days on the bottom of the Auglaize River, Ohio, consisted of a reduction in carbonate content, a decrease in particle size, and a slight loss of Al and Si; however, no significant changes in basal spacings were observed.Clays equilibrated in river water under laboratory conditions at 4° and 25°C in CO2, N2, or air atmospheres showed only an increase in oxalate-extractable iron. The concentrations of Al, Si, Fe, Mn, K, and Ca in solution above the clays varied with the atmosphere and temperature. The concentrations of Fe, Al, and Si in solution may have been influenced by the dissolution of amorphous Al-Fe-Si compounds. Therefore, the mineralogical differences between soils in the watershed and sediments in the drainage system can not be attributed to mineralogical transformations during residence in the drainage system.
Stability of Parathion on Attapulgite as Affected by Structural and Hydration Changes
Authors: Gerstl Zev , Yaron Bruno 
Published: August 2006

AbstractThe structure and hydration status of attapulgite clay after heating at elevated temperatures and the stability of parathion on these clays was studied. Using infrared spectroscopy and scanning electron microscopy it was found that the bound water was lost in two steps, at 250° and 450° with the first step being largely reversible. At 650°C the structure began to dissolve releasing significant amounts of Mg, and a decrease in aggregate porosity was noted. At 850°C an amorphous phase was formed bearing little resemblance to the original attapulgite. Parathion was stable on all of the preheated clays when kept at 25°C for 190 days. The reactions of parathion on the preheated clays was studied at 110°C Hydrolysis of parathion was found to be minimal. Isomerization was the main reaction occurring on the Ca-attapulgite, whereas on an organo-clay no isomerization was observed. A mechanism for the isomerization reaction is proposed which entails a distortion of the phosphate moiety of the pesticide by the oxygen of the ligand water resulting in the conformational changes necessary for the isomerization to take place. On the organo-clay such a conformation was not possible; hence no isomerization occurred.
Synthesis and Properties of Poorly Crystalline Hydrated Aluminous Goethites
Authors: Fey Martin Venn , Dixon Joe Boris 
Published: August 2006

AbstractAl-substituted goethites were prepared by rapid oxidation of mixed FeCl2-AlCl3 solutions at pH 6.8 in the presence of CO2 at 25°C. A combination of Al substitution and adsorption of CO2 reduced crystal size (except for an increase at small additions of Al) and produced unusual thin, porous particles. Product goethites had surface areas up to 283 m2/g and unit-cell expansions induced by hydration. Substitution of Al for Fe reduced the 111 spacing and increased infrared OH-bending vibrational frequencies. Al substitution split the goethite dehydroxylation endotherm during differential thermal analysis into a doublet and increased the temperature of all reactions. Both cold and hot alkali solutions dissolved Al from the goethite structure.After drying the product in vacuo at 110°C. X-ray powder diffraction data indicated minimal deviation from Vegard's law for the goethite-diaspore solid solution up to about 30 mole % Al substitution. Goethite prepared in the presence of 40 mole % Al had a 111 spacing of 2.403 Å corresponding to 36 mole % structural Al if Vegard's law was obeyed. Rapid oxidation of mixed FeCl2-AlCl3 solutions appears to be conducive to a higher degree of Al substitution in goethite than alkaline aging of hydroxy-Fe(III)-Al coprecipitates.
Lithium and Potassium Saturation of Illite/Smectite Clays from Interlaminated Shales and Sandstones
Authors: Howard James J. 
Published: August 2006

AbstractMixed-layer illite/smectite (I/S) clays in lower Eocene sediments of the Texas Gulf Coast decrease in expandability with depth as found in previous studies of clay diagenesis, but at the same depth the 1/S clays from sand laminae tend to be more expandable than clays from adjacent shales. The I/S clays with greater expandability from sands collapse to phases with very low expandabilities after saturation with K. This non-ideal smectite behavior indicates that many of the expandable layers in I/S clays from sand laminae possess an illite-level negative layer charge on the structure. The Greene-Kelley Li-saturation test of the I/S clays also reveals that a considerable portion of the increased layer charge deficiency is created by tetrahedral substitution. The illitization of individual smectite layers in an I/S clay is envisioned to be a two step process instead of the single step rapid transformation implied in many earlier studies. The first rate-limiting step is the creation of sufficiently large negative layer charge in the lattice, primarily by AI for Si substitution in the tetrahedral sheet. The second rate-limiting step is the supply of K to the high-charged expandable layers. The abundance of high-charged expandable layers in I/S clays from sand laminae suggests that the K supply is influenced more by competing ions in the interstitial waters than by the absolute activity of K.
Grinding of Chrysotile in Hydrocarbons, Alcohol, and Water
Authors: Papirer Eugène , Roland Patrick 
Published: August 2006

AbstractThe change of the properties of chrysotile after ball milling in organic liquids (aromatics, alcohols, silicone oils) or water was studied by gas adsorption, electron microscopy, X-ray powder diffraction, infrared spectroscopy, differential thermal analysis, zeta potential measurements, and chemical analysis. Grinding in low viscosity organic solvents leads initially to a rapid defiberization of the asbestos bundles and to a fragmentation of the isolated fibrils. Finally, amorphization and agglomeration occur causing a drastic decrease of the specific surface area of the ground material. Grinding in water brings about a defiberization, but much more slowly than in organic solvents. Moreover, prolonged grinding in water does not significantly alter the structure of chrysotile. The efficiencies of the organic solvents, considered as grinding aids that induce fracture of the fibrils, are related to the environmental stress cracking of brittle solids (Rehbinder theory). Hence, the pertinent properties of the organic liquids are their viscosity and their cohesion energy (solubility parameter). Solvents chemisorbed on the surface of the ground chrysotile reduce the surface energy of the fracture surface and prevent aggregation. Water does not react according to Rehbinder's theory, but appears to form a protective layer around the fibrils. This hypothesis was verified by dry grinding defiberized asbestos (rapid amorphization) or by disturbing the stability of the water coating by coadsorbing alcohol on the solid surface. Alternatively, the resistance of the fibrils to fracture may be explained by Westwood's theory that grinding in water is equivalent to grinding in an alkali medium, wherein the surface charge of the chrysotile becomes negligible, and the mechanical stability of the fiber reaches a maximum.
Infrared Spectroscopy of Picloram Interactions with Al(III)-, Fe(III)-, and Cu(II)-Saturated and Hydrous Oxide-Coated Montmorillonite
Authors: Aochi Y. , Farmer W. J. 
Published: August 2006

AbstractThin clay films prepared from aqueous suspensions of the potassium or sodium salt of picloram (4-amino-3,5,6-trichloropicolinic acid) with Al-, Fe-, or Cu-saturated montmorillonite or with montmorillonite coated with hydrous oxides of Al, Fe, or Cu were examined in an air-dry condition by infrared (IR) techniques to elucidate possible modes of interaction between picloram and the mineral surfaces. Deuteration was used to confirm band assignments of picloram and its salts prior to interaction with montmorillonite. Picloram interactions with Al- and Fe-saturated montmorillonite and with montmorillonite coated with hydrous oxides of Al and Fe were concentration dependent. At high picloram concentrations similarities with the IR spectrum of potassium picloram indicated that much of the picloram was present in the salt form. As the concentration of picloram was reduced below that equivalent to 1 meq/g clay, the IR spectrum indicated the presence of the monomeric acid on the mineral surface. The spectrum of picloram on montmorillonite with a coating of copper hydrous oxide was similar to that of a Cu-picloram complex indicating coordination type bonding. The spectrum of picloram with Cu-saturated montmorillonite did not correspond to any of the other spectra of picloram examined. The interaction of picloram with montmorillonite coated with a hydrous oxide coating of Cu and with Cu-saturated montmorillonite were independent of picloram concentration in the range 2.20-0.44 meq/g clay.
Dissolution of Iron Oxides and Oxyhydroxides in Hydrochloric and Perchloric Acids
Authors: Sidhu P. S. , Gilkes R. J. , Cornell R. M. , Posner A. M. , Quirk J. P. 
Published: August 2006

AbstractThe dissolution of synthetic magnetite, maghemite, hematite, goethite, lepidocrocite, and akaganeite was faster in HCl than in HClO4. In the presence of H+, the Cl− ion increased the dissolution rate, but the ClO4− ion had no effect, suggesting that the formation of Fe-Cl surface complexes assists dissolution. The effect of temperature on the initial dissolution rate can be described by the Arrhenius equation, with dissolution rates in the order: lepidocrocite > magnetite > akaganeite > maghemite > hematite > goethite. Activation energies and frequency factors for these minerals are 20.0, 19.0, 16.0, 20.3, 20.9, 22.5 kcal/mole and 5.8 × 1011, 1.8 × 1010, 7.4 × 107, 5.1 × 1010, 2.1 × 1010, 3.0 × 1011 g Fe dissolved/m2/hr, respectively. The complete dissolution of magnetite, maghemite, hematite, and goethite is well described by the cube-root law, whereas that of lepidocrocite is not.
Hydrothermal Reactions of Clay Minerals and Shales with Cesium Phases from Spent Fuel Elements
Authors: Komarneni Sridhar , White William B. 
Published: August 2006

AbstractThe immobilization of soluble Cs from spent fuel elements by ion exchange and direct chemical reaction with clay minerals or shales was investigated under hydrothermal conditions. Various clay minerals or shales were reacted with likely Cs sources and water at 300 bars pressure and 100°, 200°, and 300°C for 4, 2, and 1 months, respectively. Pollucite was the principal product, but CsAlSiO4 was also observed, along with unreacted or hydrothermally altered aluminosilicates. From Cs concentrations of the product solutions partition of Cs between liquid and solids was found to vary depending on the Cs source, the clay or shale phase, temperature, and run duration. For example, illite-Cs2MoO4 interactions resulted in 19, 32, and 95% fixation of added Cs at 100°, 200°, and 300°C respectively. Fixation of as much as 97% of the Cs in some solids was observed. In addition to Cs-aluminosilicates, Cs was fixed on cation-exchange sites by interlayer collapse in montmorillonite. Reactions with Cs2MoO4 also produced powellite because Ca was available in the reaction mixture. The U6+ from β-Cs2U2O7 was reduced to form uraninite by sulfide- and/or organic-rich shales. (Cs,Na)2(UO2)(Si2O5)3·4H2O, an analog of weeksite, was produced in reactions with β-Cs2U2O7. The reaction products pollucite and uraninite can immobilize much of the Cs and U from spent fuel elements because Cs in pollucite is extremely difficult to exchange and U in uraninite is insoluble.
Zeolite Diagenesis Below Pahute Mesa, Nevada Test Site
Authors: Moncure George K. , Surdam Ronald C. , McKague H. Lawrence 
Published: August 2006

AbstractThe Tertiary silicic volcanic rocks in the Silent Canyon Caldera beneath Pahute Mesa, of the Department of Energy's Nevada Test Site have been divided into three vertical mineralogical zones that vary in thickness and transgress stratigraphic boundaries. Zonal contacts are generally sharp. Zone 1, the uppermost zone, includes unaltered or incipiently altered rhyolitic glass. Zone 2 is characterized by a predominance of clinoptilolite and subordinate amounts of smectite, cristobalite, and mordenite. Zone 3 is a complex mineral assemblage that includes analcime, quartz, calcite, authigenic K-feldspar and albite, kaolinite, chlorite, and mixed-layer illite/smectite. The mixed-layer clay shows an increase in ordering and a decrease in expandability with depth.Shortly after deposition and after shallow burial, hydration of relatively impermeable, highly porous vitric rocks resulted in the rapid formation of the Zone 2 assemblage (except mordenite). This stage of alteration resulted in a net porosity loss and negligible mass transfer. Continued burial and rise in temperature led to a dehydration stage in which the Zone 2 assemblage was replaced by the Zone 3 minerals. The dehydration stage resulted in a porosity increase and an increase in permeability of several orders of magnitude. This process, like the earlier reactions, also conserved mass. Precipitation of mordenite followed the formation of this zonal configuration. The diagenetic zones below Pahute Mesa were caused by: (1) changing pore-water chemistry in an essentially closed hydrologic system; (2) disequilibrium or kinetic precipitation of metastable phases; and (3) a higher thermal gradient than that now present.
Electrical Conductivity and the Surface Characteristics of Kaolinitic Clays and Clay-Humic Acid Complexes
Authors: Lockhart N. C. 
Published: August 2006

AbstractThe conductivites of the Na and H ion-exchanged forms of kaolinitic clay rejects from sand-washing operations, both purified and as found naturally as a complex with soil organic matter, were examined. The two Na-clays showed linear conductivity-concentration characteristics, each having two regions with different slopes intersecting at ∼3.3% by weight of clay, which probably reflect a structural change from sol to gel. In the gel region, only the Na-counterions conducted, the reduction in conductivity with concentration being due to a smaller proportion of these ions in the Gouy layer and/or a decrease in their mobilities. In the sol, an additional, concentration-dependent conductivity arose from the electrophoretic motion of clusters of clay particles which gradually broke down on dilution. The two acid clays showed curved conductivity-concentration characteristics consistent with a weak acid dissociation equilibrium; the pKa values of 6.37 to 6.56 are close to those determined independently from titration with alkali. A stronger acid species detected in the titrations was not seen in the conductivity. The MOH2+/MOH/MO− model of the clay-surface species and one set of the predicted concentrations of each species (see preceding paper) are consistent with the observed conductivities. The MOH2+ species probably bridged the edges and faces of clay particles so that the H atoms were identical, but became different when alkali was added.
X-Ray Powder Diffraction Identification of Illitic Materials
Authors: Śrondoń Jan 
Published: August 2006

AbstractThe 10-Å clay components of sedimentary rocks (“illites”) are commonly mixtures of 100% nonexpandable illite and an ordered illite/smectite mixed-layer mineral. If the proportion of the illite/ smectite in a mixture is sufficient to produce a measurable reflection between 33–35°2θ (CuKα radiation) that is noncoincident with an illite reflection, the ratio of component layers and type of interstratification for the mixed-layer mineral can be determined. The identification technique developed in this study rests upon the following experimental findings for ordered illite/smectites of diagenetic origin: (1) the thickness of the illite layer in illite/smectites is 9.97 Å; (2) the thickness of smectite-ethylene glycol complex ranges from 16.7 to 16.9 Å; (3) illite/smectites form a continuous sequence of interstratification types—random, random/IS, IS, IS/ISII, ISII—and each type is related to a specific range of expandability.The new technique broadens the computer simulation method developed by R. C. Reynolds and J. Hower to include those sedimentary materials which are dominated by the presence of discrete illite, are low in illite/smectite, and, as such, have been described previously only by an “illite crystallinity index.”
Noncrystalline Fe-Si-Al-Oxyhydroxides
Authors: Eggleton Richard A. 
Published: August 2006

AbstractHigh-resolution transmission electron microscopy of noncrystalline Fe-Si-Al-oxyhydroxide gels shows a common structure of hollow packed spheres having external diameters ranging from 50 to 1000 Å. Some sphere walls display a concentric structure, particularly if the gel composition is close to that of a crystalline clay mineral (e.g., smectite, kaolin). The spheres probably formed by expansion of void space (bubbles) as the surrounding gel contracted 5–10% because of partial ordering of the Fe-Si-Al-oxygen network. Much of the water contained in such noncrystalline minerals is incorporated within the bubbles.
Nuclear Magnetic Resonance, Infrared, and X-ray Powder Diffraction Study of Dimethylsulfoxide and Dimethylselenoxide Intercalates with Kaolinite
Authors: Raupach M. , Barron P. F. , Thompson J. G. 
Published: August 2006

AbstractDimethylselenoxide (DMSeO) forms three structurally resolvable intercalates with kaolinite (d(001) = 10.95, 11.26, and 11.38 Å). The 11.26-Å kaolinite: DMSeO intercalate is structurally analogous to the 3-D ordered kaolinite: DMSO intercalate (d(001) = 11.22 Å). Infrared and solid-state 77Se nuclear magnetic resonance data indicate that all DMSeO molecules are equivalent in the structure and, therefore, that the 11.26-Å kaolinite: DMSeO intercalate structure is C-face centered. Structural model refinement from X-ray powder diffraction (XRD) data further support this conclusion (Pl, a = 5.195(2), b = 8.990(4), c = 11.946(5) Å, α = 91.33(2)°, β = 109.39(2)°, γ = 89.77(2)°). The kaolinite: DMSO intercalate structure was subsequently re-refined from the XRD profile in C-face centered Pl. The derived orientation of the DMSO and DMSeO molecules with respect to the basal plane of their respective intercalates is in agreement with polarized infrared measurements of the angles with ab of S=O (40.3°) and Se=O (38.8°) for the 11.26-Å intercalate. The locations of the organic molecules also agree with observed infrared band splittings and perturbations. Interatomic distances calculated from the band shifts agree with those for the XRD derived structures.The 11.38-Å kaolinite: DMSeO intercalate is closely related to the 11.26-Å intercalate, the main differences being a 2-fold disorder in the orientation of the DMSeO molecule and less penetration of the kaolinite ditrigonal cavity by that molecule. The 10.95-Å kaolinite: DMSeO intercalate, displaying disorder parallel to [110], was obtained from the 11.26- or 11.38-Å intercalates by removal of some DMSeO.
Mechanisms of Gibbsite Crystallization from Partially Neutralized Aluminum Chloride Solutions
Authors: Hsu Pa Ho 
Published: August 2006

AbstractTo interpret the erratic conditions, rates, and extent of gibbsite crystallization from partially neutralized A1C13 solution, the following hypothesis is proposed: The initial OH-A1 polymers in the freshly prepared solutions were probably unstable and transformed into either gibbsite or stable OH-A1 polymers via two different reaction paths. In the presence of nuclei, the OH-A1 polymers dissociated into monomeric ions, which then deposited onto nuclei to form gibbsite. In the absence of nuclei, the unstable polymers slowly converted to stable polymers. The erratic stability of OH-Al solutions and gibbsite crystallization are therefore attributed to the relative magnitudes of these two reaction paths which, in turn, are attributed to two key factors: (1) the distribution of unstable vs. stable OH-Al polymers; and (2) the presence or absence of nuclei. The duration of aging of the parent solution governed the distribution of unstable vs. stable polymers. The rate of neutralization resulted in varying localized high alkalinity in OH-Al solution preparation and thus varying development of nuclei.
Distribution of Ca and Na Ions in Dioctahedral Smectites and Interstratified Dioctahedral Mica/Smectites
Authors: Iwasaki Takashi , Watanabe Takashi 
Published: August 2006

AbstractThe structures of 11 smectites and 2 interstratified mica/smectites containing mainly Ca2+ and Na+ as exchangeable cations in variable ratio were studied under a relative humidity of about 40%. Observed X-ray powder diffraction patterns were compared with diagrams calculated from interstratification models containing 15.2-Å Ca-smectite layers (C), 12.4-Å Na-smectite layers (N), and 10.0-Å mica layers (M) in various combinations. The smectites appear to be a random interstratification of component layers C and N, and display a tendency towards segregation. One of the interstratified minerals studied is a regular interstratification of C and M layers; the other is a regular interstratification of C, N, and M layers, in which N and C layers are randomly distributed in equal proportion and show a tendency towards segregation.