bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incorporation of Radioactive Contaminants into Pyroaurite-Like Phases by Electrochemical Synthesis
Authors: Roh Y. , Lee S. Y. , Elless M. P. , Foss J. E. 
Published: August 2006

AbstractDuring electrochemical remediation of radionuclide, 235U, 238U, and 99Tc-contaminated aqueous solutions, pyroaurite-like phases, ideally [M(II)M(III)(OH)16CO3·4H2O] where M = Fe, were synthesized following coprecipitation with iron from metal iron electrodes. The effect of radionuclides on the transformation of amorphous precipitates to crystalline pyroaurite-like phases was investigated using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray analysis, Fourier-transform infrared (FTIR) spectroscopy, and fluorescence spectroscopy. The synthetic iron carbonate hydroxide phases showed primary XRD peaks at 0.7 and 0.35 nm and FTIR spectra that indicated the presence of a brucite-like sheet structure with carbonate anions occupying the interlayer. Divalent and trivalent iron, eroded from the electrode, occupies the octahedral sites of the brucite-like sheets. The carbonate anions in the interlayer balance the excess positive charge from isomorphous substitution of the Fe2+ or Fe3+ by reduced uranium (U4+) and technetium (Tc4+). Because of the lower solubility associated with crystalline phases than amorphous phases, incorporation of radioactive contaminants into pyroaurite-like phases by electrochemical syntheses represents a more effective approach for removing U and Tc from contaminated aqueous solutions than traditional technologies.
Reduction and Sorption of Chromium by Fe(II)-Bearing Phyllosilicates: Chemical Treatments and X-Ray Absorption Spectroscopy (XAS) Studies
Authors: Brigatti Maria Franca , Lugli Cristina , Cibin Giannantonio , Marcelli Augusto , Giuli Gabriele , Paris Eleonora , Mottana Annibale , Wu Ziyu 
Published: August 2006

AbstractThe reduction of hexavalent chromium species in aqueous solutions by interaction with Fe(II)-bearing solid surfaces was studied using a 0.96 × l0−3 M Cr(VI) solution and iron-rich clays with different Fe(II)/Fe(III) ratios, layer charge, and exchange properties, i.e., chlorite, corrensite, and montmorillonite. Experimental studies demonstrated that Fe(II)-bearing phyllosilicates reduce aqueous Cr(VI) ions at acidic pH. Chlorite and corrensite, owing to the high Fe(II)/Fe(III) ratio, are electrochemically reactive, as rapid Cr(VI) reduction indicated. In contrast, montmorillonite showed minimum to nil reactivity towards Cr(VI). Furthermore, corrensite, which is high in both Fe(II)/Fe(III) ratio and exchange capacity, adsorbs the greatest amount of chromium.X-ray absorption spectroscopy at Al, Mg, Fe, and Cr K-edges was used to investigate the adsorbed chromium species. The montmorillonite sample, unaffected by treatment with Cr(VI) solution, displays no change at any investigated edge. Edge shape and energy also do not change for the Mg and Al spectra in corrensite, and changes are minor in chlorite. By contrast, the Fe K-edge changes both in chlorite and corrensite, and indicates an increase of Fe(III) in treated samples at the expense of pre-existing Fe(II). Cr K-edge spectra show that chlorite and corrensite sorb Cr(III), which implies its reduction from Cr(VI) in the interacting solution.
Mixed Layering of Illite-Smectite: Results from High-Resolution Transmission Electron Microscopy and Lattice-Energy Calculations
Authors: Olives Juan , Amouric Marc , Perbost Régis 
Published: August 2006

AbstractMixed layering of illite-smectite was studied both experimentally, by using high-resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM), and theoretically, by using lattice-energy calculations.Samples from a hydrothermal origin show the transformation of smectite to illite with different ordering types in the illite-smectite layer sequences. Ordering ranges from complete disordered (Reichweite, R = 0 type) in the less transformed samples to increased local order, with IS and IIS sequences (R = 1 and R = 2, respectively; I = illite, S = smectite) in more illitized samples.Lattice-energy calculations are used to determine the structure of the illite-smectite sequence, which corresponds to the minimum energy. The unit layers are: O0.5TI′TO0.5 (O, T, and I′, respectively, denote the octahedral and tetrahedral sheets, and the interlayer. The 0.5 signifies half of the octahedral cations.) For example, the arrangements of the perfectly ordered … ISIS … and … IISIIS … sequences are respectively … OM(TI′T)IOM(TI′T)S … and … OM(TI′T)IOI(TI′T)1OM(TI′T)S … (the subscripts I, S, and M, respectively, refer to compositions of illite, smectite, and midway between at 0.5). Such arrangements produce a polar model for TOT layers, which display a TIOMTS structure in the case of IS adjacent layers. Furthermore, the lattice energies of … ISIS … and … IISIIS … are found to be nearly equal to the corresponding sums of the lattice energies of illite and smectite. This result indicates that interstratified illite-smectite and the two-phase assemblage of illite + smectite have similar stabilities.On the basis of the above model, the solid-state transformation of one smectite layer to one illite layer, which produces mixed-layer sequences, involves the transformation of an O0.5TI′TO0.5 unit of smectite into the same corresponding unit of illite.
Authigenic Illite and Organic Matter: The Principal Hosts of Vanadium in the Mecca Quarry Shale at Velpen, Indiana
Authors: Peacor Donald R. , Coveney Raymond M. , Zhao Gengmei 
Published: August 2006

AbstractThe Mecca Quarry Shale Member from Velpen, Indiana contains abundant vanadium which occurs in solid solution within illite-rich illite-smectite (I-S) having an average content of 1.65 wt. % V, and an overall composition of K0.8(Al2.8Mg0.5Fe0.4V0.3)(Si7.2Al0.8 g)O20(OH)4, analogous to the V-rich dioctahedral mica, roscoelite. The illite contains more than twice as much V as the associated kerogen. Detrital mica has a composition typical of 2M1, muscovite and contains no vanadium. The V-rich illite has a structure and composition typical of formation during normal prograde diagenesis and probably is widespread in the Mecca Quarry Shale because the bed is enriched in V throughout the Midwest. The smectite-to-illite reaction can not be a result of passive burial metamorphism because the host strata were buried no deeper than ~0.5 km at Velpen. The formation of illite occurred in unlithified sediments at shallow depths under the influence of pervasive 80–110°C basinal brines, possibly the same fluids that were responsible for the Mississippi Valley-type lead-zinc mineralization common in the Midwest. The presence of two types of K-rich phyllosilicates may be part of the reason for the lack of correlation between bulk V concentrations and the intensities of X-ray diffraction peaks of illite reported by others.
Authigenesis of Trioctahedral Smectite in Magnesium-Rich Carbonate Speleothems in Carlsbad Cavern and other Caves of the Guadalupe Mountains, New Mexico
Authors: Polyak Victor James , Güven Necip 
Published: August 2006

AbstractTrioctahedral smectite is a constituent of Mg-rich carbonate crusts and moonmilks (pasty deposits) in caves of the Guadalupe Mountains of southeastern New Mexico. Energy dispersive X-ray microanalysis of individual crystallites and their aggregates along with the X-ray diffraction analysis indicates that the smectite is probably stevensite. Saponite is likely present in some samples also. The smectite is intimately associated with dolomite crusts and huntite moonmilks in Carlsbad Cavern, Lechu-guilla Cave, and other dolostone caves. Clay particles appear as fibers and films, with aggregates comprising decimicron-sized filamentous masses that envelop crystals of dolomite, huntite, and magnesite. The occurrence of smectite is related to the genesis of the Mg-rich carbonate minerals. In water films, progressive evaporation and carbon dioxide loss results in the sequential precipitation of Mg-rich calcite, aragonite, dolomite, huntite, and magnesite. This sequence of carbonate precipitation removes Ca and greatly increases the Mg/Ca ratio in the solutions. Silica is commonly available probably because of high pH conditions, and consequently, smectite forms in the Mg-rich alkaline environment. Along with the Mg-rich carbonate minerals, opal, quartz, and uranyl vanadates may precipitate with the smectite.
Iron-Oxide Mineralogy of a Mollisol from Argentina: A Study By Selective-Dissolution Techniques, X-Ray Diffraction, and Mössbauer Spectroscopy
Authors: Acebal Silvia G. , Mijovilovich Ana , Rueda Elsa H. , Aguirre María E. , Saragovi Celia 
Published: August 2006

AbstractSelective-dissolution techniques by ammonium oxalate (OX), dithionite-citrate-bicarbonate (DCB), and dithionite-ethylenediaminetetraacetic acid (D-EDTA), and X-ray diffraction and Mössbauer spectroscopy were used to identify and characterize iron oxides and oxyhydroxides in the <2-mm, <50-μm, and <2-μm size fractions of a Mollisol from Bahia Bianca, Argentina. Iron compounds are present at low concentrations in mixtures with quartz, Na-rich feldspar, illite, interstratified illite-montmorillonite, and traces of kaolinite. Total Fe and Al content increases as soil particle size decreases, from 4.3 and 13.3 wt. % in the <2-mm size fraction to 8.5 and 22.8 wt. % in the clay fraction (<2 μm), respectively. No more than 25–30% of the total Fe is associated with the crystalline and the amorphous Fe oxides. Weakly ferromagnetic hematite and goethite were identified in the different fractions. These phases have small particle sizes and/or low crystallinity. They may also have Al for Fe substitutions. Crystalline magnetite or maghemite is rare. These Fe-rich phases are probably coating coarser particles.The efficiency of Fe removal is highest for the D-EDTA treatment and least efficient for the OX method, for all fractions. The opposite is true for Al removal. Poorly crystalline hematite and goethite, which are soluble in oxalate, are only present in the coarser fractions. Poorly crystalline and crystalline hematite and goethite, which are soluble in DCB and EDTA, are present in coarser fractions, but do not occur in the clay fraction. DCB treatment probably dissolves Al in the 2:1 type phyllosilicates occurring in this soil, whereas D-EDTA dissolves Fe in the hydroxy interlayers of the smectite minerals or in the silicate phases.
Refinement of the Crystal Structure of Cronstedtite-1T
Authors: Hybler Jiří , Petříček Václav , Ďurovič Slavomil , Smrčok Ĺubomír 
Published: August 2006

AbstractThe crystal structure of cronstedfite-1T was refined in space group P31m, using two crystals: a triangular tabular crystal from Herja, Romania and a conical crystal from Lostwithiel, Cornwall, England. The Herja sample has the composition of (Fe2+2.20Fe3+0.80)(Si1.20Fe3+0.78Al0.02)O5(OH)4 and the Lostwithiel sample has the composition of (Fe2+2.32Fe3+0.68)(Si1.32Fe3+0.66Al0.02)O5(OH)4. The results of refinements are as follows: a = 5.512(1) Å, c = 7.106(1) A, R = 3.07%, and 342 independent reflections; and a = 5.503(1), c = 7.104(1) Å, R = 2.24%, and 335 independent reflections for the Herja and Lostwithiel samples, respectively. The structure consists of one tetrahedral and one octahedral sheet. There is one octahedral site, M1, occupied by Fe only, and one tetrahedral site, T1, occupied by Si and Fe in the ratio of 0.617(8):0.383 (Herja) and 0.699(6):0.301 (Lostwithiel). Positions of two hydrogen atoms were determined from a difference map for the Lostwithiel data. The ditrigonalization angle of the tetrahedral sheet is α = −11.5° (Herja) and α = −11.1° (Lostwithiel), and the structures have a Franzini-layer type of B. The crystals studied are affected by ± b/3 stacking faults which produced slight streaking of h - k ≠ 3n reflections.
Electron Microscopy Study of Volcanic Tuff Alteration to Illite-Smectite Under Hydrothermal Conditions
Authors: de la Fuente S. , Cuadros J. , Fiore S. , Linares J. 
Published: August 2006

AbstractExperimental alteration of volcanic tuff from Almeria, southeastern Spain, was performed in solutions with different Na/K ratios (0.01, 1, 10, and 100), different total salt concentrations (0.01, 0.1, 0.2, 0.33, and 1 M), and in deionized water, at 60, 80, 120, and 160°C, for periods of 60, 90, 180, and 360 d. Two particle size fractions of volcanic tuff were used: 10–200 and 20–60 μm. Alteration products were examined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), laser-particle size analysis, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (SEM-EDS), image computer analysis, and transmission electron microscopy with microanalysis (TEM-AEM). XRD detected neoformed phases only in the products from experiments of 180–360 d at high temperatures (120–160°C), and with Na/K ratios above unity and in deionized water. The synthesized phase is a random mixed-layer illite-smectite (I-S) with 75% smectite. The quantity of newly formed I-S, determined by FTIR, ranged between 3–30%. There was no apparent change in grain size and shape of the grains after the experiments as compared to before.SEM-EDS and TEM-AEM revealed the following alteration sequence: 1) intense etching on glass-grain surfaces; 2) formation of hemispherical morphologies on grain surfaces; 3) precipitation of very thin, individual flakes of illite-smectite on glass-grain surfaces; 4) development of I-S at the edges of glass grains; and 5) development of I-S honeycomb structures either covering large areas of the glass grains or resulting from the complete alteration of glass grains. A direct transformation of glass to I-S seems to be the major reaction mechanism, although there also is evidence of glass dissolution and subsequent I-S precipitation.
Clay-Mineral Authigenesis in the Late Permian Coal Measures, Bowen Basin, Queensland, Australia
Authors: Uysal I. Tonguç , Golding Suzanne D. , Audsley Frank 
Published: August 2006

AbstractMineralogical studies were performed on authigenic clay minerals of mudrocks, sandstones, and bentonites from 38 boreholes in the Late Permian coal measures of the Bowen Basin. Clay-mineral separations of samples from the northern Bowen Basin consist mainly of (Reichweite, R) R = 1 and R ≥ 3 interstratified illite-smectite (I-S), chlorite, and kaolinite. In the southern Bowen Basin, samples from higher stratigraphie sections are characterized by randomly ordered (R = 0) I-S mixed layers, and kaolinite and chlorite in smaller amounts. Samples from the lower sections consist of (R ≥ 3) I-S, chlorite, chlorite-rich chlorite-smectite (C-S), and laumontite.Examination of the mineralogy and distribution of authigenic clay minerals from the Late Permian coal measures in the northern part of the Bowen Basin indicated that the presence of clay minerals is not systematically related to depth and clay occurrences do not occur regularly. These mineralogical variations of clay in volcaniclastic sediments are incompatible with thermal control. Variations in the rate of fluid flow and potassium supply owing to permeability exert major influences on clay-mineral paragenesis and the reaction of illitization. In more permeable zones (possibly faults or fracture zones), highly illitic clays with lath-shaped morphologies may have precipitated directly from potassium-rich fluids migrating from deeper parts of the basin. In addition, abundant chlorite precipitated contemporaneously with illitic clays, which may have resulted from sufficient magnesium and iron occurring in the fluids as a result of dissolution of intermediate or mafic-rock fragments. At the same time, clay paragenesis with less illitic I-S, kaolinite, and minor chlorite occurs outside the channelized zones of high fluid flow, where a diffusive-flow regime may have predominated with lower ratios of the activities of K+ and H+ (i.e., αK+/αH+) in the solutions.In the southern Bowen Basin, depth-related changes in the distribution of clay minerals are evident and may be indicative of thermal control on clay-mineral reactions. Zeolites are present locally in the Late Permian volcaniclastic rocks in the southern Bowen Basin, but not in the north. This is attributed to a low ratio of αCO2/αH2O (where α = activity) and/or more saline and alkaline solutions.
Mg-Rich Smectite “precursor” Phase in the Tagus Basin, Spain
Authors: de Santiago Buey Cristina , Suárez Barrios Mercedes , García Romero Emilia , Doval Montoya Mercedes 
Published: August 2006

AbstractThe pink clays from the Tagus basin, Spain, were characterized by X-ray difraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Chemical data were obtained by plasma emission spectroscopy and analytical electron microscopy (AEM), and specific surface and cation-exchange capacity were measured also. The data indicate that these pink clays are primarily stevensite. This Mg-rich smectite is characterized by poor crystallinity, a high degree of structural disorder, trioctahedral character (pure magnesian), a very low cation-exchange capacity, a very small crystal size (which generates an abnormally high specific surface area), and a deficiency of octahedral cations. On the basis of the very small crystal size, a large number of edge dislocations, the lack of periodicity (turbostratic) in the structure, and a cellular (spherical) texture observed by TEM, we consider this occurrence to be an early stage of crystallization. Unlike other precursor clay materials described in the literature, this clay is not an alteration of volcanic ash, but it was generated by precipitation from a Si- and Mg-saturated medium.
Heats of Adsorption of N-Hexane by Thermal Gravimetry with Differential Scanning Calorimetry (Tg-DSC): A Tool for Textural Characterization of Pillared Clays
Authors: Pires J. , de Cavalho M. Brotas , Carvalho A. P. , Guil J. M. , Perdigón-Melón J. A. 
Published: August 2006

AbstractMicroporous materials, (materials with pore sizes with widths <2 nm) were prepared by pillaring of smectites obtained from different soil deposits. The materials were prepared by intercalation with oligomeric cations of aluminum, which were transformed to aluminum-oxide pillars by calcination. The adsorption of n-hexane in the pillared clays was studied by the determination of heats of adsorption. Heats of adsorption were measured using either a static microcalorimeter or differential scanning calorim-etry coupled with thermogravimetry (TG-DSC). In this latter case, two different procedures were used that differ on the introduction of the (n-hexane) molecules that are to be adsorbed. The results obtained by the (standard) static microcalorimeter method and the TG-DSC method were compared. This comparison showed the heats of adsorption obtained by TG-DSC are differential heats of adsorption, and it showed the range of adsorption. Characterizing the texture of pillared clays, especially microporosity, is important for monitoring the intercalation process and for determining potential applications of these materials. Correlations between the obtained heats of adsorption and the dimensions of micropores suggest that TG-DSC is a semi-quantitative method for characterizing micropores in aluminum-pillared clays.
Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer
Authors: Iwasaki Masashi , Kita Masaki , Ito Kengo , Kohno Atsuya , Fukunishi Koushi 
Published: August 2006

AbstractThe basal spacings of complexes of saponite with five cationic dyes, 1,1′-diethyl-2,2′-cyanine, crystal violet, methylene blue, 1,1′-diethyl-2,2′-carbocyanine, and 1,1′-diethyl-2,2′-dicarbocyanine, varied with degree of saturation of each dye. At low loading of dye to saponite, each cationic dye showed nearly the same absorption spectrum in the UV-visible region as that of its dilute aqueous solution, whereas the spectrum changed distinctly at high loading. With increasing degree of dye loading, the absorption band shifted to longer wavelength for 1,1′-diethyl-2,2′-cyanine (J band) and to shorter wavelength for the others (D, H bands). On the basis of the basal spacing of each respective dye-clay complex, the orientation of the intercalated dye molecules is proposed as follows: the major plane of the cationic dye lies horizontal to the 2:1 layer surface at low loading. With increasing loading, the dye molecules interact with adjacent dye molecules and orient vertically to the 2:1 layer at high loading near the cation-exchange capacity.
Stepwise Hydration of High-Quality Synthetic Smectite with Various Cations
Authors: Tamura Kenji , Yamada Hirohisa , Nakazawa Hiromoto 
Published: August 2006

AbstractSmectites synthesized from experiments at 5.5 GPa and 1500°C are of high quality, crystals are large at >10 μm, and the 2:1 layers may have a homogeneous charge distribution. Smectite was exchanged with various cations (Na+, Li+, K+, Ca2+, and Mg2+) and the hydration behavior of each sample was observed by an in situ powder X-ray diffraction method under precisely controlled relative humidity (RH). The smectite showed distinct stepwise (discontinuous) hydration versus RH. During the transition between two hydration states, the coexistence of the two states was observed. Randomly interstratified structures with one and two planes of H2O are time-dependent phenomena and relate to hydration and dehydration processes.
Saponite from the Emet Colemanite Mines, Kütahya, Turkey
Authors: Çolak Mümtaz , Helvaci Cahit , Maggetti Marino 
Published: August 2006

AbstractClay mineralogy and whole-rock chemistry of the borate-bearing layers of the Hisarcik and Esbey mines were examined. The Hisarcik clays occur as laminated or unlaminated clay layers with sharp contacts. Unlaminated layers contain quartz derived from metamorphic rocks and carbonate fragments in a clay matrix, and are interpreted as reworked tuffs deposited in playa-lake environments. An important feature is that the unlaminated clays contain little MgO (3–15 wt. %) as compared with the laminated clays (15–30 wt. %). As previous studies have shown, the clay fraction of the studied profile contains predominantly Li-bearing saponite, and accounts for 60–90 wt. % of the clay fraction (<2 μm). Illite in the clay fraction varies from 0 to 67 wt. % and the average illite percentage never exceeds 40 wt. %. Chlorite is scarce (2–5 wt. %). Illite-smectite interstratified clays (illite at 70%, smectite at 30%) were only found in low concentrations in the laminated clay layers of the upper limestone unit (above the borate zone), where illite-2M of detrital origin is also present. The Esbey clays occur interstratified with colemanite layers and envelope colemanite nodules. Calcite is the major mineral of the clays whereas quartz, plagioclase, feldspar, colemanite, and cahnite are minor components. The MgO contents vary between 4.70–13.95 wt. % in the clays interstratified with colemanite layers, between 7.24–11.89 wt. % in the enveloping clays, and between 10.27–21.25 wt. % in clays located above the colemanite zone. The composition of the clay fraction (<2 μm) in all samples is similar. Smectite represents between 40–90 wt. % of the clay fraction in the upper portion of the stratigraphic profile and decreases towards the lower part of the stratigraphic profile. Smectite always occurs with illite which may vary from 20 to 90 wt. % of the clay fraction, and a small amount of kaolinite and chlorite. Illite-2M polytype is abundant. The d(060)-reflection position suggests that the smectite minerals from the Hisarcik and Esbey colemanite mines contain both dioctahedral and trioctahedral smectites to form a transitional zone. These smectites are a product of a magnesium-rich alkaline playa-lake environment.