bluuebunny/crossref_metadata_2025_split huggingface dataset:
Components of Surface Free Energy of Some Clay Minerals
Authors: Jańczuk Broniseaw , Białopiotrowicz Tomasz 
Published: August 2006

AbstractThe wetting contact angle was measured for water drops settled on the surface of pressed discs of kaolinite, alumina, bentonite, marble, montmorillonite, and quartzite immersed in hexane, octane, dodecane, cis-decalin, and air. Minimum and maximum values of the contact angle were obtained for the given systems of solid-water drop-hydrocarbon, depending on the manner of disc preparation. Using both minimum (θmin) and maximum (θmax) values of the contact angle, values of the dispersion component (γsd) of surface free energy of these solids were calculated from the equation which was derived on the basis of an equilibrium state of the system solid-water drop-hycrocarbon for two different hydrocarbons. The values of γsd for kaolinite, alumina, bentonite, marble, montmorillonite, and quartzite obtained from θmin are 83.5, 98.1, 98.9, 80.2, 95.9, and 89.7 mJ/m2, and from θmax are 73.1, 85.0, 84.4, 75.8, 85.5, and 75.5 mJ/m2. These values for marble and quartzite are similar to those in the literature (marble = 67.7 mJ/m2; quartzite = 71.3 and 76.0 mJ/m2). The values of the dispersion components of surface free energy for marble and quartzite covered with a water film (γsfd) were found to be: 41.8, 36.9; 49.2, 42.5; 49.6, 42.2; 40.2, 38.1; 48.1, 42.8; and 44.9, 38.0 mJ/m2, respectively. Values of γsfd for kaolinite, bentonite, and montmorillonite agreed well with those obtained from hydrocarbon adsorption isotherms determined by differential thermal analysis (35.5, 36.5, and 37.4 mJ/m2).Using values of γsfd and contact angles measured in the system solid-water drop-air, the nondispersion component of the surface free energy of solids with adsorbed water film (γsfn) was calculated from the modified Young equation. The values of γsfn for kaolinite and quartzite are as follows: 55.8, 69.0; 85.6, 94.0; 52.1, 75.0; 64.7, 68.9; 54.9,71.3; and 59.2,74.4 mJ/m2. The values of the nondispersion components determined for kaolinite, bentonite, and montmorillonite agreed well with those obtained by differential thermal analysis (67.6, 78.3, and 65.5 mJ/m2, respectively). Further, based on the assumption that the adsorbed water film decreased the surface free energy of these solids by the value of the work of spreading wetting, the nondispersion component (γsn) of the surface free energy of the solids was calculated to be: 86.9,129.6; 169.5, 187.7; 67.1, 144.8; 117.5, 129.3; 83.0, 135.7 and 100.2, 143.4 mJ/m2. These calculated values of the nondispersion component of marble and quartzite surface free energy agree with those obtained from adsorption isotherms determined by chromatographic and differential thermal analysis (marble = 103.8, 106.4; quartzite = 112, 115, 153.6 mJ/m2).
Weathering of Chlorite and Vermiculite in Ultramafic Rocks of Cabo Ortegal, Northwestern Spain
Authors: Buurman P. , Meijer E. L. , van Wijck J. H. 
Published: August 2006

AbstractChloritic veins in serpentinite and their weathering products were analyzed by X-ray powder diffraction (XRD) and X-ray fluorescence spectrometry (XRF). Chlorite formed during the Hercynian-age orogenesis had apparently been partly transformed to high-charge vermiculite during subsequent metamorphism of the rocks. The idealized structural formulae for these minerals are (Al1.9Fe3+0.2Fe2+0.4Mg9.2Cr0.2)(Si5.8Al2.2)O20(OH)16 and X1.3(Fe3+0.7Fe2+0.1Mg5.2Ni0.1)(Si5.8Al2.2)O20(OH)4, respectively. This transformation appears to have taken place by the removal of the hydroxy-interlayer from the chlorite without major effect on the rest of the structure. It is not clear whether other hydroxy-interlayered vermiculites containing less tetrahedral aluminum were intermediate weathering products or inherited minerals. The ultimate weathering product of chlorite and vermiculites was a Fe3+-rich smectite, which probably formed by precipitation from solution.
Electron Transfer Processes Between Hydroquinone and Hausmannite (Mn3O4)
Authors: Kung K.-H. , McBride M. B. 
Published: August 2006

AbstractA kinetic study of the oxidation of hydroquinone by aqueous suspensions of hausmannite at pH 6 was conducted using an on-line analysis system. Electron transfer between hydroquinone and the oxide was monitored by ultraviolet and electron spin resonance spectroscopy to measure the loss of hydroquinone and the appearance of oxidation products. Although hydroquinone oxidized on the surface of the oxide and the oxide surface was altered after the reduction, hydroquinone and its oxidation products did not adsorb strongly on the surface. At a high concentration of hydroquinone, p-benzosemiquinone free radicals persisted in aqueous solution and were oxidized by dissolved O2. Calculations based on the thermodynamic stabilities of the oxide and the organic species involved show that the formation of p-benzosemiquinone radical by Mn reduction is feasible. The presence of the radicals indicates that the oxidation of hydroquinone by the oxide proceeded by a one-electron transfer process. At high organic/ oxide ratios, an increase in the amount of hausmannite dissolved with increasing hydroquinone concentration suggests that the reduction of the oxide by the organic was not limited to the surface layer of the oxide. At a high concentration of hydroquinone, polymers were detected in solution, suggesting that radical-mediated reactions played a role in the polymerization process. A reaction scheme is proposed to explain the effect of the Mn oxide to hydroquinone ratio on the consumption of O2 and the appearance of quinone, p-benzosemiquinone, and polymers in solution.
Chromate Adsorption by Kaolinite
Authors: Zachara J. M. , Cowan C. E. , Schmidt R. L. , Ainsworth C. C. 
Published: August 2006

AbstractChromate (CrO42−) adsorption was investigated on kaolinite (0.2–2 μm) saturated with NaClO4 over a range of pH. Adsorption increased with decreasing pH because of protonation of chromate and/or variable charge sites on kaolinite. Chemical pretreatment to remove noncrystalline and crystalline oxide contaminants affected the magnitude of CrO42− adsorption, but not the pH range over which CrO42− adsorbed. Chromate adsorption at different sorbate and sorbent concentrations increased below the pHzpc for the kaolinite edge, suggesting the formation of weak surface complexes. If CrO42− and SO42− were present at equal concentration (5.0 × 10−7 M), the two solutes sorbed independently, suggesting binding to separate sites. The presence of excess SO42− (5.0 × 10−4 M), however, unexplainably enhanced CrO42− adsorption. The adsorption of both Chromate and sulfate can be described in terms of a site-binding model of the kaolinite edge, in which the edge is viewed as composite layers of Al and Si oxide. Surface complexation constants for CrO42− on kaolinite were similar to those for alumina, pointing to the importance of Al-OH edge sites in Chromate adsorption.
Hydrothermal Alterations of Hisingerite Material from a Basalt Quarry Near Geelong, Victoria, Australia
Authors: Shayan Ahmad , Sanders John V. , Lancucki Christopher J. 
Published: August 2006

AbstractTo understand the genetic relationship between hisingerite material in the joints of an overlying grey basalt and nontronite and Fe-rich saponite in the joints and matrix of a more deuterically altered, underlying green basalt, the hisingerite material was treated in a series of hydrothermal experiments. No well-ordered clay mineral was produced at temperatures <340°C, although extended treatment for 445 days and at 110°C or 42 days at 180°C resulted in the formation of materials that gave broad, weak, basal X-ray powder diffraction (XRD) reflections characteristic of 2:1 phyllosilicates. Hematite did not form at 110°C, but it did form at 180°C in 1- and 6-week runs. Treatments at 340°C in Pt, Ag-Pd, and Au containers resulted in mixtures of Fe-rich saponite + hematite, but the same starting material treated at 340°C in stainless steel yielded, in addition, some chlorite, probably due to the more reducing conditions in the stainless steel container. Treatment of the unaltered grey basalt at 340°C and 50 MPa for 10 days resulted in complete alteration of olivine (and probably glass) to a trioctahedral smectite.The Fe-rich saponite produced by the hydrothermal treatment of the hisingerite material has a composition and XRD pattern similar to the Fe-rich saponite found in the green basalt and an XRD pattern similar to that produced by the hydrothermal treatment of the grey basalt; thus these clays may have had a similar origin. The compositions and XRD patterns of these clays are not similar, however, to those of the nontronite in the joints of the green basalt. The nontronite probably formed during a subsequent low-temperature alteration.
Comparison of Clay and Zeolite Mineral Occurrences in Neogene Age Sediments From Several Deep Wells
Authors: Velde B. , Iijima A. 
Published: August 2006

AbstractClay and zeolite mineral assemblages were determined for five deep wells in volcano-clastic sediments (Japan) and for one well in mudstones (California). The clay mineral suites in these wells showed a gradual change with depth of illite/smectite (I/S) composition, which increases in smectite content in the upper portion towards a fully expandable mineral (2–3-km depth) and then decreases in smectite content with depth (2–5 km). The temperature of transformation or recrystallization to a fully expandable smectite mineral is about 60°–70°C in non-zeolite bearing rocks and 70°–90°C in zeolite-bearing rocks, with no apparent dependence on time. Comparison is made between the I/S smectite content in the lower part of the wells (i.e., below the occurrence of the fully expandable mineral) and the zeolite mineral zone boundaries. The 60% smectite composition was found at 108°–118°C maximum burial temperatures. The zeolite II/III zone boundary, i.e., the onset of the analcime zone, occurs between 85° and 95°C and may be slightly time-related in the span of 1–15 Ma. The clay and zeolite minerals can be used as temperature indicators in the range of the Neogene age.
Evidence for the Formation of Interlayer Polyacrylonitrile in Kaolinite
Authors: Sugahara Yoshiyuki , Satokawa Shigeo , Kuroda Kazuyuki , Kato Chuzo 
Published: August 2006

AbstractA kaolinite-polymer intercalation complex was apparently formed for the first time by the polymerization of acrylonitrile between the kaolinite layers. A kaolinite-ammonium acetate intercalation complex was dispersed in acrylonitrile monomer. The monomer was apparently incorporated between the layers by displacing intercalated ammonium acetate. After the removal of excess monomer, the intercalation complex was heated to cause polymerization. The resulting kaolinite-polyacrylonitrile (PAN) intercalate showed a basal spacing of ∼ 13–14 Å. On heating the complex at 220°C for 1 hr in air, the spacing decreased slightly. The hydrogen bond between the hydroxyls of kaolinite and probably the C≡N group of PAN was not affected after heating at 220°C. Even after heating at 400°C, the layers expanded. Because the starting kaolinite-ammonium acetate intercalation complex decomposed at a much lower temperature, these observations strongly suggest the presence of PAN between the layers.
Sintering of Montomorillonites Pillared by Hydroxy-Aluminum Species
Authors: Tichit D. , Fajula F. , Figueras F. , Ducourant B. , Mascherpa G. , Gueguen C. , Bousquet J. 
Published: August 2006

AbstractThe sintering of montmorillonites pillared by hydroxy-Al species was investigated by several techniques. The change of the microporosity of the pillared interlayer clay with temperature shows that sintering was mainly due to the loss of microporosity. On calcination of the parent clay at 760°C, the X-ray powder diffraction pattern did not change; the 060 line shifted only slightly from 8.988 to 9.017 Å. The infrared (IR) spectrum suggested some dehydroxylation, but the structure appears to have been preserved. On calcination of the pillared clay at >700°C, the intensity of the 001 line decreased steadily, the 060 line broadened, and the b parameter decreased slightly from 8.988 to 8.928 Å. Fe3+ ions apparently occupied only one site after calcination at 300°C and two sites after calcination at 700°C. Smaller isomer shifts and higher quadrupole splittings in the Mössbauer spectra suggest that calcination produced more covalent bonding of Fe3+ and a highly distorted structure. The IR spectrum was significantly modified by calcination of the sample, and the 935- and 1125-cm−1 bands disappeared and the 1035-cm−1 band broadened. These results suggest that at <700°C the pillars sintered and that the clay progressively decomposed at >750°C. The pillaring-induced decrease of thermal stability of the clay was likely due to the introduction of protons during the first step of the preparation. The thermal stability of these Al-pillared interlayer complexes is comparable to that reported for hydroxy-silicoaluminum montmorillonites and fluorhectorites.
Mössbauer Spectroscopic Identification of Iron Oxides in Nontronite From Hohen Hagen, Federal Republic of Germany
Authors: Lear Paul R. , Komadel Peter , Stucki Joseph W. 
Published: August 2006

AbstractIron impurities in the Hohen Hagen nontronite (NG-1) were identified as maghemite and goethite. The phase identified as maghemite was magnetically ordered at both room temperature and 87 K, with hyperfine magnetic fields of 48.6 and 50.7 tesla, respectively. Due to the magnetic properties of this phase, it was easily separated from aqueous dispersions of the clay using a hand magnet. X-ray powder diffraction analysis revealed maghemite, quartz, and phyllosilicate in the magnetically separated phase. The impurity identified as goethite remained in the non-magnetic <2-μm fraction of the clay, displayed magnetic order only at 87 K (47.44 tesla hyperfine field), and accounted for about 8% of the total area of the Mössbauer spectrum.
Relative Solubility of Corundum, Gibbsite, Boehmite, and Diaspore at Standard State Conditions
Authors: Peryea F. J. , Kittrick J. A. 
Published: August 2006

AbstractThe solubilities of HCl-treated samples of corundum, gibbsite, boehmite, and diaspore in aqueous solutions at 298 K and one atmosphere pressure were determined from undersaturated and supersaturated initial conditions. Solution characteristics at apparent equilibrium were measured and used to calculate equilibrium constants (Kr) for mineral dissolution reactions:
$$\begin{array}{l} A{l_2}{O_3}\left( {corundum} \right) + 3{H^ + } = A{l^3} + 1.5\,{H_2}O,\\ Al{\left( {OH} \right)_3}\left( {gibbsite} \right) + 3{H^ + } = A{l^3} + 3\,{H_2}O,\\ and\\ AlOOH\left( {boehmite\,or\,diaspore} \right) + 3{H^ + } = A{l^3} + 2{H_2}O, \end{array}$$
Assuming solid phase and water activities of unity, log Kr = 3pH - pAl3+ for all three equations. The calculated log Kr values were: 9.01 ± 0.05 (corundum), 7.76 ± 0.14 (gibbsite), 7.49 ± 0.09 (boehmite), and 6.75 ± 0.24 (diaspore), indicating that the relative thermodynamic stabilities under the experimental conditions were: corundum < gibbsite < boehmite < diaspore. The gibbsite value agreed well with that determined independently by another research group using acid-treated subsamples of the same source mineral (7.70 ± 0.02). The calculated Gibbs free energies of formation (kJ/mole) were: -1587.4 ± 2.1 (corundum), -1156.7 ± 1.6 (gibbsite), -921.0 ± 1.5 (boehmite), and -925.1 ± 2.0 (diaspore). The Δ Gfo values of the acid-treated minerals were 1.8 to 12.4 kJ/mole more negative than values recently compiled for untreated mineral samples. This result is attributed to the removal of reactive surface coatings that isolated the bulk mineral phases from the solution phase.
Modified Clays for the Adsorption of Environmental Toxicants: Binding of Chlorophenols to Pillared, Delaminated, and Hydroxy-Interlayered Smectites
Authors: Zielke Richard C. , Pinnavaia Thomas J. 
Published: August 2006

AbstractDue to their unique polarity, pore-size distribution, and high surface areas, pillared and delaminated clays are potentially useful materials for the adsorption of environmental toxicants. To determine their properties for adsorption of chlorinated phenols, alumina-pillared montmorillonite (APM), chromia-pillared montmorillonite (CPM), and alumina-delaminated Laponite (ADL) were reacted with aqueous pentachlorophenol (PCP) solutions in batch equilibrium experiments. An hydroxy-Al Laponite (HAL) in which the Na+ exchange ions were replaced by ions of the type Al13O4(OH)(24+x)(H2O)(12-x)(7-x)+ was included in the study. With ADL as the adsorbent, the extent of PCP adsorption increased with decreasing pH, and then became constant at pH ≤ pKa. Thus, the neutral phenol was preferred over the phenolate form. Binding of neutral PCP at pH 4.7 to all adsorbents never reached saturation values, and the loadings achieved were limited by the water solubility of the adsorbate. Among the pillared and delaminated clays investigated, ADL exhibited the largest capacity for physical adsorption of PCP at pH 4.7. Differences in the PCP binding capacities for APM, CPM, and ADL suggested that adsorption was dependent on the pore structure and surface composition of the modified clay adsorbent, not on surface area alone. HAL exhibited quantitative uptake of PCP at the 8 µmole/g level, indicating that a chemi-sorption mechanism may operate for PCP binding to this adsorbent. Adsorption of 3-chlorophenol, 3,5-dichlorophenol, and 3,4,5-trichlorophenol by ADL at pH 7.4 increased as the degree of hydrophobicity and chlorination of the phenol increased; hence, the binding capacity was not limited by the molecular size of the adsorbate. In contrast to the adsorption properties observed for pillared, delaminated, and hydroxy-interlayered clays, Na+-montmorillonite and Na+-Laponite did not adsorb PCP from aqueous solution.
Cacoxenite in Miocene Sediments of the Maryland Coastal Plain
Authors: Hearn Paul P. , McCartan Lucy , Soller David R. , Krohn M. Dennis , Gonzalez Virginia M. 
Published: August 2006

AbstractCacoxenite having the composition (Al4.0Fe22.5O7.1(OH)14.3(PO4)17(H2O)23.7)·50.3H2O was identified in a bed of mature quartz sand in the Miocene Calvert Formation near Popes Creek, Maryland. This is the first reported occurrence of this mineral in Atlantic Coastal Plain sediments north of Florida. The cacoxenite occurs as silt-size to sand-size grains, both as irregularly shaped aggregates and as radiating arrays of delicate acicular crystals. The presence of discrete cores and overgrowths in some grains indicates at least two generations of crystal growth. Electron microprobe analyses reveal excess Si and Al (relative to the ideal composition), which is believed to reflect ultra-fine clay particles within the cacoxenite grains. Admixed clays probably served as a substrate for the formation of ferric oxyhydroxides, which were subsequently converted to cacoxenite through the addition of dissolved phosphorus.
Celadonite and its Transformation to Smectite in an Entisol at Red Rock Canyon, Kern County, California
Authors: Reid D. A. , Graham R. C. , Edinger S. B. , Bowen L. H. , Ervin J. O. 
Published: August 2006

AbstractA green, Lithic Torriorthent soil derived from a celadonite-rich, hydrothermally altered basalt immediately north of the Mojave Desert region in southern California was studied to investigate the fate of the celadonite in a pedogenic weathering environment. Celadonite was found to be disseminated in the highly altered rock matrix with cristobalite, chalcedony, and stilbite. X-ray powder diffraction (XRD) showed the soil material to contain celadonite having a d(060) value of 1.510 Å, indicative of its dioctahedral nature. Very little smectite was detected in the parent material, whereas Fe-rich smectite was found to be abundant in the soil. The Fe-smectite and celadonite were identified as the sole components of the green-colored clay fraction (<2 µm) of all soil horizons. The soil clay showed a single d(060) value of 1.507 Å, indicating that the smectite was also dioctahedral and that its b-dimension was the same as that of the celadonite. Mössbauer spectroscopy showed that the chemical environments of Fe in the rock-matrix celadonite and in the smectite-rich soil clay were also nearly identical. These data strongly suggest a simple transformation of the celadonite to an Fe-rich smectite during soil formation.Supporting evidence for this transformation was obtained by artificial weathering of celadonite, using sodium tetraphenyl boron to extract interlayer K. The intensity of the 001 XRD peak (at 10.1 Å) of celadonite was greatly reduced after the treatment and a peak at 14.4 Å, absent in the pattern of the untreated material, appeared. On glycolation of the sample, this peak expanded to 17.4 Å, similar to the behavior of the soil smectite. The alteration of celadonite to smectite is a simple transformation requiring only the loss of interlayer K. The transformation is apparently possible under present-day conditions, inasmuch as the erosional landscape position, shallow depth, and lack of significant horizonation indicate that the soil is very young.
Determination of Surface Free Energy of Kaolinite
Authors: Chibowski Emil , Staszczuk Piotr 
Published: August 2006

AbstractThe adsorption of n-octane and water vapor on natural kaolinite was measured. From adsorption isotherms film pressures were determined which were then used to calculate the dispersion and nondispersion components of the kaolinite surface free energy. In addition, thermodesorption of water from the kaolinite surface was determined. These results suggest that physically adsorbed water remained on the kaolinite surface, even at temperatures as great as 125°C. Therefore, experimentally determined dispersion and nondispersion components appear to relate to the surface precovered with a film of water. These values are: γSf(w)d = 34.4 mJ/m2 for dispersion interactions and γSf(w)n = 60.2 mJ/m2 for nondispersion interactions. Assuming a kaolinite surface precovered with a film of water, which decreased the free energy by the work of spreading, the following components of the energy for the bare surface were calculated: γSd = 67.6 mJ/m2 and γSn = 103.4 mJ/m2, for dispersion and nondispersion components, respectively.
Mobilization of Quartz Fines in Porous Media
Authors: Cerda César M. 
Published: August 2006

AbstractThe onset of the mobilization of fine particles of quartz (fines) in sandpacks was determined by comparing the theoretically calculated hydrodynamic and colloidal forces acting on a fines particle near a representative sand grain. The results show that the mobilization of fines depends strongly on the chemistry of fluids present in the reservoir. Specifically, a critical electrolyte concentration exists for mobilization, which depends on the pH. For large particles of fines and relatively high fluid velocity, the mobilization of fines may depend on the fluid velocity, but in a narrow range of electrolyte concentration. The types of interactions between the fines and sand grain surfaces were corroborated by direct visual observations using a traveling microcell pack.The mobilization of fines in sandstones leads to a reduction of permeability (i.e., a reduction of the hydraulic conductivity).