bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation of 1,2- and 1,4-Dihydroxybenzene by Birnessite in Acidic Aqueous Suspension
Authors: McBride M. B. 
Published: August 2006

AbstractThe rate and extent of oxidation of dihydroxybenzenes (DHB) to quinones in acetate-buffered suspensions of synthetic birnessite were studied using Mn dissolution to monitor reaction progress. Concentration of free Mn2+ in the aqueous phase was continuously monitored by electron spin resonance, and ultraviolet-visible (UV-VIS) spectroscopy was utilized to quantify dihydroxybenzene and quinone concentrations. Although dissolution of the oxide and release of Mn2+ to solution generally accompanied phenol oxidation, a threshold oxidation level had to be exceeded before Mn2+ appeared in solution. Once this threshold was surpassed, the mole quantity of Mn2+ dissolved equaled the mole quantity of organic oxidized for 1,4-DHB, but exceeded the quantity of organic oxidized for 1,2-DHB. Thus, the latter phenol was more efficient in dissolving the oxide. Soluble phosphate suppressed Mn2+ release without influencing the degree of organic oxidation, suggesting that phosphate chemically interacted with reduced Mn to hinder its dissolution. UV spectra provided tentative evidence for the transitory existence of Mn3+-1,4-DHB complexes in the solution phase.Infrared spectra of the birnessite after reaction with 1,4-DHB indicated some new features, which may have been a result of the reduction of surface Mn atoms to the 3+ oxidation state. These features were not present after reaction with 1,2-DHB, confirming that the latter phenol efficiently dissolved the oxide to release Mn2+. Although the initial Mn dissolution was very rapid and was attributed to a surface reaction, further slow Mn release accompanied by more complete oxidation of the phenols suggests a process limited by the rate of dissolution of the solid.
Illite/Smectite from Gulf Coast Shales: A Reappraisal of Transmission Electron Microscope Images
Authors: Ahn Jung Ho , Peacor Donald R. 
Published: August 2006

AbstractTransmission electron microscope (TEM) images of mixed-layer illite/smectite (I/S) from Gulf Coast shales obtained earlier by the authors have been reexamined by comparing them with the calculated images of G. D. Guthrie and D. R. Veblen. Ordered two-layer periodicity was not detected in the 1750- and 2450-m depth samples, for which X-ray powder diffraction (XRD) showed 20% and 40% illite randomly interstratified in I/S, respectively. Two-layer periodicities that occur in images of the 5500-m depth sample were inferred to reflect ordered I/S. XRD data for the same sample imply the presence of 80% illite in RI-ordered I/S. The two-layer periodicities were observed in slightly overfocused images, consistent with the image calculations of Guthrie and Veblen, with strong dark fringes inferred to correspond to smectite interlayers. Two-layer periodicities were observed only in small domains of a few of the images, consistent with the requirement of special orientation of layers, which varies continuously over a wide range. The lack of more frequent observations of ordered periodicities in TEM images may reflect the lack of the special observation conditions and chemical heterogeneity of illite and smectite layers. Ordered mixed-layering may exist in those specimens for which XRD indicates such ordering, in contrast to the previous interpretation of the authors.
Electronic State of Iron Complexes in the Interlayer of Hydrotalcite-Like Materials
Authors: Idemura Satoshi , Suzuki Eiichi , Ono Yoshio 
Published: August 2006

AbstractInfrared and Mössbauer spectroscopic studies were made on hydrotalcite-like materials, Mg6Al2(OH)16(NO3)2·4H2O, anion exchanged in aqueous solution of K3Fe(CN)6, K4Fe(CN)6·3H2O, or Na2Fe(CN)5NO·2H2O. The material anion-exchanged in aqueous solution of K3Fe(CN)6 gave infrared (IR) absorption bands at 2120 and 2040 cm-1 in the C≡N stretching region, suggesting that part of the ferrate(III) complex was reduced to ferrate(II) complex on the intercalation chiefly because pure K3Fe(III)(CN)6 and K4Fe(II)(CN)6·3H2O gives bands at 2120 and 2040 cm-1, respectively. On the intercalation of Fe(CN)64-, no change in the oxidation state of iron was observed. These features were confirmed by Mössbauer spectroscopy. In the IR spectra of material anion-exchanged in aqueous solution of Na2Fe(CN)5NO·2H2O, the intensity of bands due to N≡O (1940 cm-1) and C≡N stretching was much less than that observed for Na2Fe(CN)5NO·2H2O, indicating that most of N≡O ligand was eliminated during the intercalation. Four bands were observed in the C≡N stretching region: a band at 2143 cm-1 was assigned to C≡N groups in Fe(CN)5NO2-; a band at 2120 cm-1 was tentatively assigned to Fe(CN)5H2O2-; bands at 2040–2050 cm-1 were assigned to Fe(CN)5H2O3-.
High-Resolution Transmission Electron Microscopy and Electron Diffraction of Mixed-Layer Illite/Smectite: Experimental Results
Authors: Veblen David R. , Guthrie George D. , Livi Kenneth J. T. , Reynolds Robert C. 
Published: August 2006

AbstractHigh-resolution transmission electron microscopy (HRTEM) and electron diffraction experiments have been performed on R1 and R> 1 illite/smectite (I/S) samples that from X-ray powder diffraction (XRD) experiments appear to contain well-ordered layer sequences. The HRTEM images confirmed earlier computer image simulations, which suggested that periodicities due to I/S ordering can be imaged in TEM instruments of moderate resolution. The experiments also confirmed that in instruments of this sort, the strongest contrast arising from the compositional difference between I and S layers occurs under rather unusual imaging conditions of strong overfocus. Some selected-area electron diffraction (SAD) patterns showed additional diffraction spots consistent with R1 and R3 ordering. SAD patterns and cross-fringes arising in HRTEM images from non-00lreciprocal lattice rows indicated that the stacking vectors of most adjacent 2:1 layers were not randomly oriented with respect to each other. Thus, the I/S was not fully turbostratic, but instead consisted of very thin, coherently stacked crystallites that extended across the fundamental particles postulated by Nadeau and coworkers.S/(I + S) ratios were determined for about seventy HRTEM images obtained and interpreted by three different TEM operators. These ratios were consistent with those obtained from standard XRD procedures, suggesting that results obtained by XRD can be used to infer the initial structural state of mixed-layer I/S prior to treatment of samples for XRD experiments. The HRTEM experiments thus demonstrated that the two specimens examined consisted of ordered I/S existing as small crystals, most of which contained more layers than the fundamental particles of Nadeau and coworkers. The non-turbostratic stacking suggests an energetic interaction between the individual fundamental particles, leading to at least two alternative thermodynamic descriptions of these materials. Although the I/S crystals in the present experiments probably were disaggregated into fundamental particles during sample preparation for XRD, the I/S crystals appear to have separated only along the smectite interlayers. If the term “fundamental particle” is to be used for primary, untreated I/S, its original definition should be modified to include not only free particles, but also those that occur as layers within small crystals. It further should be recognized that these particles can interact thermodynamically and crystallographically with their neighbors.
Morphological, Chemical, and Isotopic Evidence for an Early Diagenetic Evolution of Detrital Smectite in Marine Sediments
Authors: Clauer Norbert , O'Neil James R. , Bonnot-Courtois Chantal , Holtzapffel Thierry 
Published: August 2006

AbstractMineralogical (XRD), morphological (transmission electron microscopy), chemical (major, rare-earth elements, and scanning-transmission electron microscopy), and isotope (Sr, O, H) measurements were made of marine detrital smectite from shales to study their reactions during early diagenesis. Albian, Aptian, and Palaeogene smectite samples were selected from Deep Sea Drilling Project drill cores taken in the Atlantic Ocean and from outcrops and drill cores from Belgium and northern France. Detrital, fake-like smectite particles seem to have adapted to their depositional environment by isochemical dissolution and subsequent crystallization of authigenic, lath-like particles. The major-element and rare-earth element compositions of both types of particles are similar. The Sr isotope chemistry suggests that the dissolution-crystallization process occurred soon after deposition in an almost closed chemical system. Except for slight changes in the amount of Fe and the oxygen isotope composition, the reaction took place without noticeable chemical exchange with the interstitial or marine environment. Such closed-system recrystallization of clay minerals may be a common diagenetic process if the water/rock ratio is small, as in shales.
Influence of Dodecylamine Chloride on the Surface Free Energy of Kaolinite
Authors: Jańczuk Bronisław , Chibowski Emil , Białopiotrowicz Tomasz , Hołysz Lucyna , Kliszcz Anna 
Published: August 2006

AbstractContact angles of glycerol and diiodomethane drops were measured on the surface of kaolin pellets covered with different amounts of dodecylamine chloride (DDACl) to as much as one monolayer. For a glycerol drop, the contact angle changed from 25.7° (bare surface) to 45.4° for the surface precoated with 0.125 monolayer of DDACl, but remained nearly constant above this level up to one monolayer. For a diiodomethane drop, the contact angle changed from 28.6° (bare surface) to 58.1° for one DDACl monolayer precoating. Using these contact angles and a modified Young equation, the dispersive and nondispersive components of the surface free energy of DDACl-covered kaolin were calculated. These data showed that in the extreme case (one monolayer) the dispersive component was reduced by the DDACl from ∼36 mJ/m2 (bare surface) to 25.4 mJ/m2, i.e., the value characteristic for paraffin (25.5 mJ/m2); however, the nondispersive component was not reduced to zero. A minimum value (15.83 mJ/m2) was determined for the sample covered with 0.125 DDACl monolayer (calculated), and a slight increase in the nondispersive component was observed for greater coverages. Such a change of the nondispersive component suggests that, at higher coverages, some adsorbed DDACl molecules were oriented with their polar ends off the surface. Based on the values of the γsfd and γsfn, the work of water spreading was calculated. This work was positive for the bare surface (32.8 mJ/m2) and methanol-treated (36.5 mJ/m2) kaolin surface, but negative for 0.125 DDACl monolayer precoating (-31.1 mJ/m2). It remained essentially unchanged for higher coverages. These data mean that bare and methanol-treated kaolinite surfaces were hydrophilic and that DDACl-treated surfaces were hydrophobic.
Characterization of Illitization of Smectite in Bentonite Beds at Kinnekulle, Sweden
Authors: Inoue Atsuyuki , Watanabe Takashi , Kohyama Norihiko , Brusewitz Ann Marie 
Published: August 2006

AbstractStructure, morphology, and chemical composition of illite/smectite (I/S) containing 30–50% smectite layers (% S) from Kinnekulle bentonites, Sweden, of diagenetic origin were examined using X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Interlayer arrangements of I/S changed from random interstratification to short-range ordered at about 40% S. The transition from random to ordered structure proceeded continuously as reflected by the gradual decrease in probability of two smectite neighbors (Pss) towards zero. TEM observations of water-dispersed samples that had not been cation-exchanged showed that the I/S consisted dominantly of flakes coexisting with laths having a length/width ratio of about 4, regardless of % S. The thickness of the I/S particles ranged from 30 to 100 Å, and no systematic variation in thickness was detected with decreasing % S. The chemical composition of the I/S also changed continuously with decreasing % S. These observations suggest no dissolution of smectite layers and no recrystallization of illite layers during the formation of the I/S in these bentonites; rather, cationic substitutions occurred within a smectite precursor (termed a solid-state transformation mechanism). A comparison of interlayer order, particle texture, and chemistry of the I/S from various types of rocks suggests that the mechanism of smectite-to-illite conversion in the range 100% S-30% S was related to the porosity and permeability of original rocks. The solid-state transformation mechanism appears to have predominated in rocks of low porosity and permeability.
Role of Water in the Smectite-to-Illite Reaction
Authors: Whitney Gene 
Published: August 2006

AbstractA series of hydrothermal experiments was performed to determine the effect of fluid abundance on the reaction of smectite to illite. Experiments were conducted on K-saturated montmorillonite (<0.1-µm fraction) in a closed system at 250° to 400°C using run times of 1, 7, 14, 30, and 60 days at 100 MPa (1 kbar) pressure. In fluid-deficient systems (pore spaces not saturated), the rate and extent of illitization was significantly inhibited. A rock: water ratio of 20:1 (mass: mass) produced an R0 illite/smectite (I/S) having 82% smectite layers after 60 days at 250°C, whereas a rock: water ratio of 1:1 produced an I/S having 57% smectite layers under the same conditions. The effect became less pronounced at higher temperatures, with the 20:1 and the 1:1 experimental products differing by only 11% expandability at 400°C after 60 days. In addition, the low-fluid experiments produced fewer crystalline byproducts (quartz, cristobalite, chlorite) than did the fluid-rich runs, and the I/S was more difficult to disperse and orient in the fluid-deficient samples, suggesting enhanced cementation at grain contacts or the production of particle morphologies that did not lend themselves to orientation. The difference in reactivity of the smectite and I/S as a function of water content appears to be attributable to the reduced capacity for low volumes of water to mediate the dissolution, solute transport, and precipitation reactions that make up the series of reactions collectively termed illitization. Of these variables, solute transport is likely to be affected most by reduction of fluid.
Synthesis of Highly Microporous and Hydrophilic Alumina-Pillared Montmorillonite: Water-Sorption Properties
Authors: Malla P. B. , Komarneni S. 
Published: August 2006

AbstractA montmorillonite exchanged with large hydroxy-Al cations was thermally treated to convert the hydroxy cations to oxide pillars and to generate permanent microporosity in the interlayers. The pillared clay products were characterized by X-ray powder diffraction (XRD) and water-sorption measurements to delineate the effect of aging of the pillaring solutions, the methods of drying and concentration of clay-water suspensions, and the temperatures of calcination on micropore volumes. Although samples prepared at different conditions gave d(001) reflections of 17–17.5 Å, at least to 500°C, the concentrations of clay-water suspensions and the temperatures of calcination significantly changed the pore-size distribution and the volume of micropores present in the sample, as calculated from the water-sorption isotherms. A narrow pore-size distribution having little or no macroporosity or external surface condensation was observed in samples prepared by the addition of the pillaring solution directly to the clay (solid) without first making a clay-water suspension and calcining the sample at ≥400°C. About 87% of the total volume was found to be micropores of ≤14–17 Å in the sample calcined at 600°C. Aging the pillaring solution, however, did not influence either the water-sorption isotherms or the XRD patterns significantly under the conditions specified. Essentially the same results were obtained for samples prepared from both hydroxy-Al polymer (OH/Al = 2) and aluminum chlorohydrol (ACH) solutions.Although alumina-pillared clays exhibited an extreme type-I isotherm (Langmuir type) for nitrogen adsorption, the sorption of water vapor gave an isotherm of unusual shape that fit neither a BET nor a Langmuir equation. This latter behavior has previously been attributed to a unique pore size and hydrophobicity and is apparently common to all pillared montmorillonite materials. The hydrophobicity of the pillared clay apparently developed on calcination by the migration of protons from the interlayers to the octahedral sheets, in which sites of cationic substitution (negative charge) were located. Protons migrated back to the interlayers by treatment with NH3, which subsequently converted to NH4+ in the interlayers. The exchange of the NH4+ by Ca2+ introduced hydrophilicity to the alumina-pillared clay, which was reflected both in the shape of the water isotherm (close to moderate Brunauer type I), the heat of sorption, and the total sorption capacity.
Occurrence of Spherical Halloysite in Bituminous Coals of the Sydney Basin, Australia
Authors: Ward Colin R. , Roberts F. Ivor 
Published: August 2006

AbstractSpherical halloysite aggregates have been identified for the first time in mineral matter isolated from bituminous coals. The spherules, found in Permian coals of the Sydney basin, New South Wales, range from 0.4 to 0.6 µm in diameter and have a delicate ring-like structure that helps to confirm the halloysite identification. They appear from their location to be related to influxes of pyroclastic debris, either directly or from nearby soils, into the original peat accumulation. Analytical electron microscopy indicates higher proportions of Si and Fe than coexisting particles of hexagonal platy kaolinite, and electron diffraction reveals a typical disordered halloysite structure. The aggregates are larger than those normally reported in soils, and comparison to growth rates in soils suggests development over a significantly longer time than that expected for accumulation of the host coal seams. The buckled structure in the ring-like pattern and the related crude polyhedral outlines probably reflect shrinkage with dehydration during the coalification process, but it may also be due to the different sample preparation techniques.
Secondary Phase Formation During Nuclear Waste-Glass Dissolution
Authors: Abrajano T. A. , Bates J. K. , Woodland A. B. , Bradley J. P. , Bourcier W. L. 
Published: August 2006

AbstractSecondary minerals formed during simulated weathering of nuclear waste glasses have been identified by analytical electron microscopy. A complete description of the reacted glass, from the outermost surface in direct contact with the leachant solution to the reacting front that migrates into the bulk glass, was obtained. Manganese and iron oxyhydroxide phases and saponite were found to have precipitated onto the residual glass surface from the leachant solution. Iron-bearing smectite, serpentine, and manganese and uranium-titanium oxyhydroxides formed in situ in the glass in several distinct bands at different depths beneath the original surface. This sequential development of secondary phases displays a clear trend toward more order and crystallinity in the phases farthest from the reaction front and indicates that complete restructuring of the glass into crystalline phases did not occur at the interface with fresh glass. Additionally, the formation of a discrete uranium-bearing phase, as opposed to uranium uptake by precipitated phases, suggests that stable actinide phase formation rather than ion exchange may be a possible mechanism for retarding radionuclide release to the environment.
Effect of Negative Surface-Charge Densities of Smectite Clays on the Adsorption Isotherms of Racemic and Enantiomeric Tris(2,2′-Bipyridyl)Ruthenium(II) Chloride
Authors: Villemure Gilles 
Published: August 2006

AbstractThe level of adsorption of enantiomeric tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) by seven different smectite samples was found to be controlled by the total surface area of the clay. The level corresponded to one monolayer. The adsorption of the racemic mixture was lower for all samples, being limited to saturation of the clay's cation-exchange capacity. The addition of NaCl increased the adsorption of the racemic Ru(bpy)32+ to the same level as the enantiomers. The dependence on the clay's surface charge density, expected on the basis of the limited face-to-face aggregation model, was not found. The sharp decrease in adsorption of the enantiomers by low charge-density clays and the corresponding sharp increase in adsorption of the racemate by high charge density clays were not observed. These results do not necessarily invalidate the model. The range of negative charges examined may not have been wide enough. Also, charge distribution in smectite is generally not uniform.
Metastability in Near-Surface Rocks of Minerals in The System Al2O3-SiO2-H2O
Authors: Anovitz Lawrence M. , Perkins Dexter , Essene Eric J. 
Published: August 2006

AbstractGibbs free energies for phases in the system Al2O3-SiO2-H2O have been calculated from reversed experiments in order to correct earlier values and to calculate a phase diagram consistent with more recent experiments. An internally consistent diagram could not be calculated that agreed with all published experiments, and choices of preferred data were made. The following Gibbs free energies, relative to the elements at STP (298.15 K, 1 bar), have been derivedThe above values were calculated assuming literature values for corundum, quartz, and H2O (v).Examination of available thermodynamic, experimental, and observational data on the aluminum hydroxides gibbsite, boehmite, bayerite, and nordstrandite suggests that these minerals are metastable with respect to diaspore + water at STP and at higher temperatures. Similarly, halloysite and dickite are metastable with respect to kaolinite at these conditions. The occurrence of these minerals in soils must therefore be ascribed to nonequilibrium processes, and the use of equilibrium phase diagrams to explain their occurrence is inappropriate.
Crystalline Swelling of Smectite Samples in Concentrated NaCl Solutions in Relation to Layer Charge
Authors: Slade P. G. , Quirk J. P. , Norrish K. 
Published: August 2006

AbstractThe basal spacing of a set of smectites, with layer charges between 0.74 and 1.14 electrons per unit cell, have been measured while the smectites were in equilibrium with NaCl solutions having concentrations of 0.25 to 2.5 molal. Except for the most highly charged smectites, an expansion from ~15.5 to ~18.5 Å occurred as the NaCl concentrations were reduced. This expansion (or “crystalline swelling”) corresponds to the transition from two to three sheets of water between the silicate layers. A random interstratification of 15.5 and 18.5 Å structure units was present during the change and gave rise to broad diffraction peaks for the 001 reflections. A balance between cation hydration forces, interlamellar electrostatic forces, and van der Waals forces was apparently the basis of the relationship between surface charge and swelling. The results can be expressed in terms of the relative vapor pressures at which the transitions were half complete; these pressures increased with surface density of charge, and over the range of surface charge studied, the P/P0 values ranged from 0.943 to 0.974.