bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydration State of Cu2+ in Mixed Cu2+-Hexadecylpyridinium montmorillonit by Electron Spin Resonance
Authors: Dyrek K. , Kłapyta Z. , Sojka Z. 
Published: September 2006

AbstractElectron spin resonance (ESR) spectra of Cu2+-hexadecylpyridinium (HDP) montmorillonites were investigated as a function of HDP+ content and the hydration state of Cu2+ at relative humidities of p/p0 = 0.52-8 × 10-7 at 298°K. The symmetry of the Cu2+ ESR spectra and the intensity of the ESR signal increased upon dehydration of the complex. The HDP+ cation caused an increase in the hydration state of Cu2+ at a given p/p0 and an increase in the covalency of the Cu-O bond.
Rubification of Terrae Rossae in Slovakia: A Mössbauer Effect Study
Authors: Bronger A. , Ensling J. , Gütlich P. , Spiering H. 
Published: September 2006

AbstractMineralogical and 57Fe Mössbauer spectroscopic analyses were made on seven terrae rossae and two terrae fuscae samples of Pliocene to Early Pleistocene age from Slovakia and limestone residues from their parent materials. In most of the samples, no mineral weathering or clay mineral formation could be detected by optical or X-ray powder diffraction investigation, compared with their parent limestone residues; only one terra rossa showed a strong weathering of primary feldspar and phyllosilicates and a high rate of clay formation, especially kaolinite. Mössbauer measurements between 5° and 300°K showed that hematite and goethite are the dominant color pigments in the rubified terrae rossae and their corresponding limestone residues. The mean particle size of hematite and goethite was estimated from Mössbauer effects and X-ray powder diffraction data to be 95 and 250 Å, respectively. Reduced values of the hyperfine fields at 5°K of the soil iron oxides, as compared with those of the pure oxides, indicate a partial substitution of Fe(III) by Al. The hematite content correlates with the Munsell color notation of 5 of the 7 terrae rossae samples and their corresponding limestone residues. All terrae rossae samples showed higher hematite contents than their corresponding limestone residues, indicating that the rubification of such materials is independent of the degree of weathering.
Goyazite in Kaolinitic Altered Tuff Beds of Cretaceous Age Near Denver, Colorado
Authors: Triplehorn Don M. , Bohor Bruce F. 
Published: September 2006

AbstractA hydrated alumino-phosphate mineral was identified in thin, kaolinitic clay beds of the Cretaceous Dakota Group and the overlying Mowry Shale in the Dakota hogback west of Denver, Colorado. It occurs as 1–3-μm size euhedral crystals and makes up as much as 15% of the rock. Sr is by far the dominent divalent cation present, ranging from 9.4 to 13.1%, confirming the X-ray powder diffraction identification of this mineral as goyazite, the Sr member of the plumbogummite group. The characteristic pseudo-cubic, rhombohedral morphology of this mineral is plainly visible in scanning electron micrographs. On the basis of its euhedral morphology and its occurrence in volcanic ash-derived kaolin beds, the goyazite probably formed during early diagenesis, before or during the alteration of the ash, and before much compaction of the beds.
Sorption of Trace Constituents from Aqueous Solutions Onto Secondary Minerals. II. Radium
Authors: Ames L. L. , McGarrah J. E. , Walker B. A. 
Published: September 2006

AbstractRadium sorption efficiencies as a function of temperature, Ra concentration, and secondary mineral sorbate were determined in a 0.01 M NaCl solution. Radium sorption on a characterized clinoptilolite, montmorillonite, nontronite, opal, silica gel, illite, kaolinite, and glauconite under comparable experimental conditions allowed determination of Ra sorption efficiency curves for each, through use of Freundlich constants, over the same temperature and initial Ra solution concentration range. Similar sorption data for U on the same secondary minerals over the same temperatures allowed comparison of sorption efficiencies for Ra and U. Clinoptilolite, illite, and nontronite were the most efficient Ra sorbents, while opal and silica gel were the poorest Ra sorbents. Generally, Ra sorption on secondary minerals was much greater than U sorption under the same experimental conditions.
Sorption of Uranium And Radium By Biotite, Muscovite, and Phlogopite
Authors: Ames Lloyd L. , McGarrah Jeffery E. , Walker Becky A. 
Published: September 2006

AbstractThe sorption of U and Ra on finely ground biotite, muscovite, and phlogopite was adequately described by the Freundlich adsorption equation, (x/m) = KCn, at low U and Ra concentrations despite Ra precipitation at the higher temperature. Radium and U sorption-efficiency curves derived from the Freundlich constants generally showed decreased distribution coefficients in response to increasing temperature and increasing Ra or U concentrations. Temperatures investigated were 5°C, 25°C, and 65°C. Solution compositions used were 0.1 M NaCl and 0.01 M NaHCO, for U, and 0.01 M NaCl for Ra. Uranium initial solution concentrations ranged from 1.00 × 10−4 M to 4.00 × 10−7 M; the Ra initial solution concentration range was 6.80 × 10−7 M to 8.60 × 10−9 M.In 0.01 M NaHCO3 solutions, anionic uranyl carbonate complexes were prevalent, and because they are weakly sorbed relative to free uranyl ion and uranyl hydroxy complexes, the result was a relatively low U sorption efficiency on biotite and phlogopite and excellent sorption efficiency on muscovite. Uranyl carbonate complexes decreased in solubility with increasing temperature, so that U sorption efficiency on biotite increased with increasing temperature. Sorption of uranyl ion and uranyl hydroxy cations on biotite decreased with incresaing temperature.
Atom Positions in Highly Ordered Kaolinite
Authors: Suitch P. R. , Young R. A. 
Published: September 2006

AbstractThe crystal structure of kaolinite(Pl, a = 5.153(1), b = 8.941 (1), c = 7.403 (1)Å, α = 91.692(3)°, β = 104.860(3)°, γ = 89.822(3)°, specimens from Keokuk geodes) has been refined in detail and that of dickite (Cc, a = 5.1460(3), b = 8.9376(5), c = 14.4244(6) Å, β = 96.761(5)°) has been re-refined, both from powder diffraction data with the Rietveld method. Except for the hydrogen atoms, the layer structures in both clays are very similar and are much as inferred or determined previously by others. The rotation in the tetrahedral sheet is 7(1)°. The two inner hydroxyl O-H bonds in kaolinite are differently oriented; one points into an octahedral vacancy and the other somewhat away from the octahedral sheet and toward the unoccupied center of an oxygen triangle formed by the two apical oxygens and shared basal oxygen of two adjacent SiO4 tetrahedra. All six of the inner surface hydrogen atoms appear to be nearly equally involved in the hydrogen bonding between kaolinite layers in kaolinite.
Fourier Transform Infrared Studies of Aluminous Goethites and Hematites
Authors: Fysh Stuart A. , Fredericks Peter M. 
Published: September 2006

AbstractSynthetic aluminous hematites and goethites have been examined by Fourier-transform infrared spectroscopy. For aluminous hematites prepared at 950°C a linear relationship exists between Al content and the location of the band near 470 cm−1, up to 10 mole % Al substitution which is shown to be the solubility limit. The spectra of aluminous goethites prepared in two different ways are qualitatively similar to each other, but differ as to the relationship between the position of the band near 900 cm−1 and the Al content. The spectra of the two series of hematites produced by calcining the goethites at 590°C also show a strong dependence of band position and intensity on the goethite preparative method.
Alteration of Clay Minerals and Zeolites in Hydrothermal Brines
Authors: Komarneni Sridhar , Roy Della M. 
Published: September 2006

AbstractClay minerals and zeolites, candidate backfill minerals for nuclear waste repositories, were treated with saturated NaCl brine and Mg-rich (Mg-Ca-Na-K) brine at 200°C and 300°C for 4 weeks under a confining pressure of 30 MPa. The Al concentrations released in NaCl brine were lower than those in Mg-rich brine at both temperatures indicating that the Mg-rich brine is more acidic than the NaCl brine under these hydrothermal conditions. The Si concentrations in both brines were low because of the relatively acidic conditions developed during the hydrothermal treatment. As determined by X-ray powder diffraction or by specific Cs and Sr sorption measurements, no alteration could be detected in clay minerals treated with NaCl brine at 200°C. Among the zeolites tested, only phillipsite and erionite altered to analcime in NaCl brine at 200°C. Zeolites and most of the clay minerals tested did not alter in the Mg-rich brine treated at 200°C. Vermiculite altered to randomly interstratified vermiculite/K-vermiculite (mica-like) by selective K uptake from the Mg-rich brine.At 300°C, the clay minerals did not greatly alter, whereas the zeolites altered to analcime and/or albite in the presence of the NaCl brine. In the Mg-rich brine, Al-rich montmorillonite from Wyoming did not alter, whereas Al-poor montmorillonite from Texas altered to randomly interstratified montmorillonite/ illite at 300°C. Vermiculite collapsed to form K-vermiculite (~ 10.2 Å) by the selective uptake of K from the Mg-rich brine at 300°C. Most of the zeolites altered to smectites in the Mg-rich brine at 300°C because of the acidic conditions generated by the hydrolysis of Mg. The selective Cs-sorption Kd decreased from 11,700 for untreated phillipsite to 240 and 15 for the hydrothermally produced analcime/albite mixtures from the phillipsite at 200° and 300°C, respectively, in NaCl brine. These results suggest that montmorillonites and mordenites are relatively more resistant than vermiculite or other zeolites at elevated temperatures and pressures in concentrated hydrothermal brines expected in a salt repository.
Physical Arrangement of High-Alumina Clay Types in a Missouri Clay Deposit and Implications for Their Genesis
Authors: Keller W. D. , Stevens R. P. 
Published: September 2006

AbstractSedimentologic zones that are differentiated by changes in lithology, mineralogy, chemical composition, and crystal morphology observable in scanning electron micrographs occur in Missouri high-alumina clay deposits. These properties and changes suggest that the high-alumina materials originated from Pennsylvanian-age, paludal sediments deposited in depressions underlying Paleozoic carbonate rocks. Alumina was relatively enriched in zones of the deposits by leaching of silica and of alkali and alkaline earth metals from the sediments. The most intense leaching occurred on the highest parts of the Ozark Dome.Diaspore is the predominant high-alumina mineral. Boehmite, although far less abundant than diapsore, may have paragenetically preceded diaspore in some deposits. Chlorite, presumably an Al-rich variety because the content of MgO is typically <0.5%, is also present. Li, which is sporadically present, is inferred to have accumulated in the chlorite which may be a proto-variety of cookeite. Because Li+ and Al3+ are similar in size, Li is inferred to have accompanied Al as a resistate element in contrast to K and Na which were leached from parent phyllosilicates.
Smectite Interactions with Riboflavin
Authors: Mortland M. M. , Lawless J. G. 
Published: September 2006

AbstractSmectite with polyvalent cations on the exchange complex readily absorbed riboflavin from aqueous solution to a limit of about 0.5 mmole/g. The shape of the adsorption isotherms was of the Langmuir type. An exception was Na+-smectite which provided an S-shaped isotherm and smaller amounts of adsorption. Ca2+-vermiculite had no interlamellar adsorption of riboflavin, suggesting that this mineral does not swell sufficiently to permit such adsorption. Adsorption isotherms, X-ray powder diffraction data, and UV-visible spectroscopic data suggest that the mechanisms of interaction between smectite and riboflavin may involve a combination of ion-dipole, charge transfer, hydrogen bonding, and physical effects.
Comparison of Rapid Methods for Chemical Analysis of Milligram Samples of Ultrafine Clays
Authors: Rettig S. L. , Marinenko J. W. , Khoury H. N. , Jones B. F. 
Published: September 2006

AbstractTwo rapid methods for the decomposition and chemical analysis of clays were adapted for use with 20–40-mg size samples, typical amounts of ultrafine products (<0.5-μm diameter) obtained by modern separation methods for clay minerals. The results of these methods were compared with those of “classical” rock analyses. The two methods consisted of mixed lithium metaborate fusion and heated decomposition with HF in a closed vessel. The latter technique was modified to include subsequent evaporation with concentrated H2SO4 and re-solution in HCl, which reduced the interference of the fluoride ion in the determination of Al, Fe, Ca, Mg, Na, and K. Results from the two methods agree sufficiently well with those of the “classical” techniques to minimize error in the calculation of clay mineral structural formulae. Representative maximum variations, in atoms per unit formula of the smectite type based on 22 negative charges, are 0.09 for Si, 0.03 for Al, 0.015 for Fe, 0.07 for Mg, 0.03 for Na, and 0.01 for K.
Infrared Studies of 1-Hexene Adsorbed onto Cr3+-Exchanged Montmorillonite
Authors: Adams John M. , Clapp Terry V. 
Published: September 2006

AbstractWhen 1-hexene was adsorbed by Cr3+-montmorillonite at room temperature, all evidence of C=C(str) vibrations was lost. Protonation of the alkene occurred, and the secondary carbocation formed was bound at a site on the primary coordination sphere of the interlayer cation. Some of the hydrogen atoms of these primary-sphere water molecules were involved in strong hydrogen bonds to the silicate sheets, whereas others did not form such bonds, but were free and directed into the interlayer space. These latter hydrogen atoms were labile and protonated the alkene molecules.
Interlayer Structures of The Two-Layer Hydrates of Na- and Ca-Vermiculites
Authors: Slade P. G. , Stone P. A. , Radoslovich E. W. 
Published: September 2006

AbstractThe three-dimensional order shown by the two-layer hydrates of Na- and Ca-vermiculite, prepared from Mg-vermiculite from Llano, Texas, has enabled clear, two-dimensional Fourier projections of their interlayer structures to be obtained. Structure factor calculations were made in space group C2 and with unit-cell dimensions of a = 5.358 Å, b = 9.232 Å, and ß = 96.82°; for Na-vermiculite C = 14.96 Å and for Ca-vermiculite c = 15.00 Å. In Na-vermiculite the interlayer cations are octahedrally coordinated to water molecules with the sodium-water polyhedra only located between the triads of oxygen atoms forming bases to tetrahedra in adjacent silicate layers. In Ca-vermiculite the interlayer cations are in both octahedral and 8-fold (distorted cubic) coordination with water molecules. The octahedrally coordinated Ca ions are between the bases of tetrahedra in adjacent silicate layers, but the 8-fold coordinated Ca ions are between the ditrigonal cavities. In both Na- and Ca-vermiculite some water molecules are drawn from planar networks appreciably towards the ditrigonal cavities. The three-dimensional order observed for these vermiculites contrasts with the stacking disorder reported for Mg-vermiculite from Llano. The distinct crystallographic behavior of Na+, Ca2+, and Mg2+ in the hydration layers of Llano vermiculite probably depends on cation sizes and field strengths, together with the need to achieve local charge balance near the sites of tetrahedral Al-for-Si substitution.
Surface Condensation of Organophosphate Esters on Smectites
Authors: Mingelgrin U. , Tsvetkov F. 
Published: September 2006

AbstractParathion and methyl parathion adsorbed at high loads on clays and similar surfaces exhibited properties of a bulk phase, such as a well-defined solubility and a characteristic X-ray powder diffraction (XRD) pattern, different from those of the free substances. The aqueous solubility of parathion condensed at these surfaces was as low as 1.2 μg/ml as compared to 14 μg/ml for free parathion. The BET isotherm described the behavior of the investigated surface condensates even though these condensates were different from the multilayer adsorption for which the BET isotherm was originally developed. The XRD patterns of parathion and methyl parathion adsorbed on Na-bentonite exhibited reflections which were shifted towards higher angles as compared with the XRD patterns of the free compounds. This is in agreement with the lower solubility of the surface condensates. The properties of these condensates were easily controlled by the choice of adsorbent as well as by the choice of conditions under whch they were prepared. The existence of such surface-condensed phases and the manipulation of their properties can be utilized for the slow-release formulation of organophosphate esters which is important, for example, in pesticides application.
Structure Refinement of Deuterated Boehmite
Authors: Corbató Charles E. , Tettenhorst Rodney T. , Christoph Gary G. 
Published: September 2006

AbstractThe crystal structure of a deuterated synthetic boehmite powder, γ-AIOOD, has been determined by time-of-flight neutron diffraction and Rietveld profile refinement in space group Cmcm to a weighted profile R of 3.71%. Cell dimensions are a = 2.868(1), b = 12.2336(4), and C = 3.6923(1) Å. Alternate space groups for the boehmite structure suggested in the recent literature were found to be unacceptable. Atom positions, bond distances, and angles, with the exception of those involving hydrogen, were nearly identical to those determined by R. J. Hill in 1981 who studied a single crystal of boehmite by X-ray diffraction. All atoms were refined with anisotropic thermal parameters. The b value is 0.013 Å larger, and the thermal ellipsoids of oxygen are slightly more anisotropic than those reported by Hill and may reflect the different samples studied.
Development of Layer Charge and Kinetics of Experimental Smectite Alteration
Authors: Howard James J. , Roy Della M. 
Published: September 2006

AbstractSodium-saturated Wyoming bentonite was hydrothermally reacted at 150° and 250°C for 30 to 180 days to determine smectite alteration rates that might be applied to nuclear-waste repository design. Na-Ca solutions deficient in K were used to determine the role of interlayer cations in the creation of high layer-charge in the smectites. The results provide insight into the mechanism and timing of various steps in the diagenetic alteration of smectite to illite. X-ray powder diffraction (XRD) analyses of the reacted clay showed little effect on the character of the 17-Å reflection even after 180 days at 250°C. Potassium saturation of these reacted clays and re-examination by XRD indicated collapse of some smectite layers, leaving at most only 60% expandable layers. The development of layer charge sufficient to cause collapse on saturation with a low hydration energy exchange-cation does not require K in the reacting fluid. Rate constants for the illitization reactions as determined by K-saturated collapse are between 1.0 × 10−3 and 2.8 × 10−3/day with activation energies <3.5 kcal/mole. Ca in a Na-silicate-bicarbonate solution slightly reduced the illitization rate constants. These rate constants are higher than expected from extrapolation of studies of beidellite-composition glasses at higher temperatures, but lower than values obtained in studies of natural clays in artificial sea water. The release of Si, Al, and Mg in the 150°C experiments suggests congruent dissolution of the smectite. In contrast, at 250°C the release of Al was not stoichiometric with Si; as little as one half of the relative available Si was released. Rather than different mechanisms for dissolution at the two temperatures, the conclusion is that noncrystalline Al-rich phases formed at greater rates at higher temperatures. The cation-exchange capacities for several of these reacted smectites were significantly less than expected, suggesting a clogging of interlayer sites, perhaps by Al-complexes.
Cross-linked Smectites. IV. Preparation and Properties of Hydroxyaluminum-Pillared Ce- and La-Montmorillonites and Fluorinated NH4+-Montmorillonites
Authors: Tokarz M. , Shabtai J. 
Published: September 2006

AbstractReaction of hydroxy-Al oligocations with Ce3+- and La3+-exchanged montmorillonites, using 1.25, 1.60, or 2.0 mmole Al/g smectite, yielded partially pillared hydroxy-Al montmorillonite products containing a significant concentration of residual Ce3+ or La3+. After heat treatment at 250°C these products showed high surface areas (∼340–500 m2/g) and high basal X-ray powder diffraction spacings (18.0–18.6 Å). Calcination at 400°–700°C resulted in lower surface areas of ∼200–450 m2/g and basal spacings of 16.3–18.3 Å, the values showing a gradual decrease with a decrease in the Al/smectite weight ratio and/or increase in the heat-treatment temperature. A major modification and improvement in the cross-linking procedure was achieved by fast aging (6–48 hr) of the hydroxy-Al oligomeric solution at 95°–100°C, instead of conventional aging for 2–3 weeks at 25°C.Fluorinated NH4+-montmorillonites, containing 0.4 to 2.1 wt. % F, were prepared by reaction of NH4+-montmorillonite at 60°C with 1.0 to 3.0 N aqueous solutions of NH4F. Interaction of the fluorinated montmorillonites with hydroxy-Al oligocations, using a ratio of 2.0 mmole Al/g smectite, yielded a series of cross-linked fluorinated montmorillonites with basal spacings of 17.9–18.0 Å and surface areas of 180–325 m2/g after heat treatment at 250°C. Calcination at 400°–500°C resulted in lower d(001) (16.6–17.7 Å) and surface-area values (140–300 m2/g). Increase in the fluorine content caused gradual decrease in both values. Transmission electron microscopy of pillared Ce-montmorillonite showed a highly oriented network of well-separated, parallel unit layers with an interlayer distance, Δd(001), of 9–10 Å. Calculated lateral (interpillar) distances were in good agreement with the pore-size distributions determined in independent adsorption studies.
Mineralogy, Crystallinity, O18/O16, and D/H of Georgia Kaolins
Authors: Hassanipak Ali Asghar , Eslinger Eric 
Published: September 2006

AbstractMineralogy, kaolin crystallinity, Fe content, δO18, and δD were determined for late Cretaceous “soft” and early Tertiary “hard” Georgia kaolins. The crystallinity of the <0.5-, 0.5–1.0-, and 1.0–2.0- μm size fractions of soft kaolins was higher than that of equivalent size fractions of hard kaolins. δO18 and δD of the soft and hard kaolins ranged between 18.5 to 23.1‰, and −64 to −41‰, respectively, and could not be used to discriminate soft from hard kaolins. The trends of crystallinity vs. δO18 were different for kaolins collected at different localities, and, for a given sample, δO18 generally decreased with increasing crystallinity and with increasing crystallite size. These data indicate that the Tertiary kaolins could not have been simply derived from the Cretaceous kaolins by winnowing unless post-sedimentation recrystallization of one or both occurred. δD vs. δO18 systematics indicate that the late Cretaceous to early Tertiary Georgia kaolins crystallized over a temperature range of about 15°C in the presence of waters that varied little in isotopic composition.