bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimate of Clay-Mineral Content: Additions of Proportions of Soil Clay to Constant Standard
Authors: Ruhe Robert V. , Olson Carolyn G. 
Published: August 2006

AbstractThe method of known additions for estimating clay-mineral content was reversed in that increasing proportions of soil clay were added to a standard composed of equal weights of kaolinite, illite, and montmorillonite. After glycolation, peak-area ratios were calculated from 7.2 (kaolinite), 10 (illite), 14 and 17 Å (vermiculite and montmorillonite) diffraction peaks of standard, mixes, and soil clay. Ratios were plotted against % soil clay from the standard (0%) through the mixes (14 to 77%). Curves of fit were calculated and projected to 100% soil clay giving theoretical values which agree with measured values. As weight proportions are known in the standard, the projections permit estimates of clay-mineral weight proportions in the soil clay.
Thermodynamic and Structural Features of Water Sorption in Zeolites
Authors: Simonot-Grange Marie Hélène 
Published: August 2006

AbstractThe water adsorption capacity of zeolites is a function of pressure and temperature. Desorption of zeolites may be of three types, wherein the crystal lattice undergoes (1) no or little change, (2) a reversible change, or (3) an irreversible change. In the first two cases, the divariance of the zeolite-water vapor equilibrium results in networks of isobars, isotherms, and isosteres which can be transformed into a “characteristic” curve following the Polanyi-Dubinin theory. Because the volume of the micropores of a zeolite structure is constant, the isotherms and “characteristic” curve can be transformed linearly. During desorption, if the volume of the micropores varies due to a change of structure, the curves show linearity breaks.On the basis of X-ray diffraction, differential thermal, and thermal gravimetric analyses, the equilibrium curves and structural changes of heulandite and stilbite were determined, using specially designed equipment. In the reversible adsorption range, heulandite shows no linearity breaks in the transforms and no structural variation. Stilbite, however, shows a linearity break in the transforms corresponding to a structural change.
Clay-Polymer Interactions: Summary and Perspectives
Authors: Theng B. K. G. 
Published: August 2006

AbstractThe adsorption of uncharged polymers by clays is largely “entropy-driven.” Polymer conformation changes from a random coil in solution to an extended form at the surface in which adsorbed polymer segments or trains alternate with loops and tails extending away from the surface. Although the net interaction energy, ε, per segment-surface contact is small (~1 kT unit), the total energy of adsorption is large because the fraction of train segments, p, is commonly between 0.3 and 0.5. The adsorption isotherms are typically of the high-affinity type, and there is an apparent lack of desorption on dilution. Positively charged polymers (polycations) are adsorbed largely through electrostatic interactions between the cationic groups of the polymer and the negatively charged sites at the clay surface. Here ε ≫ 1 kT unit and p > 0.7, leading to an almost complete collapse of the polymer chain onto the surface. Indeed, beyond a given level of adsorption charge reversal can occur in that the clay-polycation system effectively behaves as an anion exchanger. Little adsorption occurs with negatively charged polymers (polyanions) due to initial charge repulsion between the polymer and the clay surface. Acid pH, a high ionic strength, and the presence of polyvalent cations in the system enhance and promote polyanion adsorption. Uncharged polymers and polycations can enter the interlayer space of expanding 2:1 type layer silicates but polyanions generally fail to intercalate.The interactions of clays with biopolymers, such as proteins, nucleic acids, and polysaccharides, can be rationalized in similar terms. When intercalation occurs, the interlayer biopolymer is further stabilized against microbial (enzymatic) degradation giving rise to practical applications of clay-polymer complexes as flocculants and soil conditioners. Polyanions are effective as flocculants because of their large “grappling distance,” whereas uncharged polymers are better suited as soil conditioners because they can spread over adjacent clay/soil particle surfaces like a coat of paint.
Anion Interactions with Freshly Prepared Hydrous Iron Oxides
Authors: Harrison Jeffrey B. , Berkheiser Vaughn E. 
Published: August 2006

AbstractInfrared analysis showed that the bonding habit of oxyanions with freshly precipitated hydrous ferric oxides depends upon the nature of the anion and its hydration level. Monovalent oxyanions adsorb through an electrostatic interaction with the hydrated hydrous oxide surface. All divalent oxyanions, with the exception of tellurate, coordinate directly with surface iron cations. Tellurate, an octahedral anion, apparently penetrates and incorporates in the hydrous oxide structure. The symmetry of the free anion has a significant role in determining the configuration of the resultant complex. For anions of the same charge, those with tetrahedral geometry (in uncoordinated states) show a higher degree of specificity for the surface than the trigonal planer anions. Without exception, each bidentate bridging complex forms by replacement of protonated and unprotonated hydroxyls. With the anion geometry and the charge being equal, the suspension pH determines the adsorption capacity of the hydrous oxide.
Influence of Silica Content on the Surface Charge Characteristics of Allophanic Clays
Authors: Gonzales-Batista A. , Hernandez-Moreno J. M. , Fernandez-Caldas E. , Herbillon A. J. 
Published: August 2006

AbstractThe surface and charge characteristics of 6 allophanic clays originating from a climatosequence of Andisols have been studied by titration, ion retention, surface area, and reactivity measurements. Several properties of these clays, such as the pH of zero charge, the magnitude of the surface area, and the reactivity of structural hydroxyl groups, appear to be governed by their chemical composition, especially by their silica content. A similar relationship between the above properties and silica content also exists for synthetic aluminosilicate gels (often quoted in the literature as possible models of allophanes), despite their different structure to the natural clays. An explanation is that as desilication proceeds, octahedral polymeric units of aluminum progressively individualize in both the synthetic and natural samples. The surface areas of the aUophanic clays, based on the slope of the titration curve at pH 7, are closely related to the amounts of structural hydroxyl that can react with fluoride at about the same pH. The permanent negative charges are always very low, even for silica-rich, allophane-bearing samples. It is therefore suggested that all of these clays should be virtually free of tetrahedral aluminum.
Synthesis of Methyl-t-Butyl Ether from Methanol and Isobutene Using a Clay Catalyst
Authors: Adams J. M. , Clement D. E. , Graham S. H. 
Published: August 2006

AbstractThe acid-catalyzed reaction between methanol and isobutene to give methyl-t-butyl ether may be carried out using a cation-exchanged smectite as the catalyst. In 1,4-dioxan solvent at 60°C smectites exchanged with Al3+, Fe3+, or Cr3+ give yields of ∼60% after 4 hr, whereas smectites exchanged with Cu2+, Pb2+, Ni2+, Co2+, Ca2+, and Na+ give less than ∼8% yield. The reaction is efficient only when certain solvents are used, e.g., with Al3+-smectite the yield is ∼5% when using 1,2-dimethoxyethane, diethyleneglycol diethylether, n-pentane, tetrahydropyran, N-methylmorpholine, or tetrahydrofuran solvents compared with ∼60% using 1,4-dioxan solvent (4 hr). Moreover, the effective solvents depend somewhat on the clay interlayer cation. The use of tetrahydrofuran and tetrahydropyran gives ∼35% yields at 60°C (4 hr) with Fe3+- or Cr3+-smectites but ∼4% yield with Al3+-smectite.
Natural Ammonium Illites from Black Shales Hosting a Stratiform Base Metal Deposit, Delong Mountains, Northern Alaska
Authors: Sterne Edward J. , Reynolds Robert C. , Zantop Half 
Published: August 2006

AbstractNaturally occurring ammonium illites have been discovered in black shales surrounding a stratiform base metal deposit in the DeLong Mountains, northern Alaska. Infrared spectra of the samples exhibit pronounced absorption at 1430 cm−1, the resonant-banding frequency for NH4+ coordinated in the illite interlayer. X-ray powder diffraction characteristics of the ammonium illites include an expanded d(001) spacing, with values as large as 10.16 Å, and ratios for I001/I003 and I002/I005 of about 2. Infrared analyses of physical mixtures of NH4Cl with a standard illite, and comparisons with synthetic ammonium micas indicate significant substitution (>50%) of NH4+ for K+ in the illite interlayer position. Nitrogen determinations on two ammonium illites after removal of carbonaceous matter gave values of 1.48 wt. % NH4+ and 1.44 wt. % NH4+. A survey of more than 150 different shale horizons indicates that the NH4+ content of the illites increases in proximity to the stratiform base metal mineralization.
Adsorption of Alkylphosphoric Acid on Kaolinite and Smectite in Water-Decane
Authors: Siffert B. , Trescol J. J. 
Published: August 2006

AbstractBis-ethyl 2-hexylphosphoric acid (di-2 EHPA) dissolved in decane is chemisorbed on kaolinite and montmorillonite dispersed in an acidic aqueous solution. The adsorption results in the formation of complexes with the surface cations of the clays. The adsorption isotherms are of the Langmuir type and reveal a limiting value of adsorption on H+-kaolinite of 12.2 mg/g, comparable to that measured in the absence of water. For H+-montmorillonite, however, the limiting value in the presence of acid is somewhat less (20.6 mg/g vs. 23.8 mg/g). Di-2 EHPA does not react with the magnesium cations available at the surface. The isotherm is “stepped” and suggests the presence of adsorption sites with distinctly differentiated energies. The sites of di-2 EHPA adsorption can be masked by treating the two clay minerals with polyphosphate anions. Thus, with pyro- and tripolyphosphate anions, di-2 EHPA uptake in acidic medium is very low. Adsorbed di-2 EHPA can be recovered by treating the clays with fluoride, hydroxyl, and dihydrogenphosphate anions. Dihydrogenphosphate anions lead, however, to a state of equilibrium between the organic and inorganic phosphate anions adsorbed.
Palygorskite-Sepiolite Clays of Lebrija, Southern Spain
Authors: Galan E. , Ferrero A. 
Published: August 2006

AbstractThe Upper Pliocene sediments near Lebrija in southern Spain contain commercial deposits of palygorskite and sepiolite. These sediments of continental origin consist chiefly of carbonate, marl, and clay resting on marine Pliocene quartzose sand. The lowest unit, the “Marly-Calcareous Bed,” consists of sepiolite-rich marl associated with concretions and irregular layers of chert, <0.5 m thick, and local diatomite layers, as well as limestone, sandy limestone, marl, and clayey sandstones. This unit has a maximum thickness of 30 m and contains three clay-mineral suites as follows: (1) bottom—sepiolite ± palygorskite; (2) center—sepiolite and palygorskite ± illite; (3) top—palygorskite and illite, ± sepiolite and smectite. Sepiolite decreases and palygorskite and illite increase toward the top, reflecting the composition of detrital material supplied to the basin. Beds 0.5–1 m thick locally and containing 50 to 60% sepiolite have been called “Tierra del Vino” (wine earth) because the material formerly was used to clarify and purify wine. The sepiolite-rich beds are as much as 15 m thick in the eastern part of the area. The upper unit is called the “Palygorskite Bed” because certain layers, 0.3 to 3 m thick, contain 35 to 75% palygorskite. The palygorskite-rich layers are interbedded with limestone and marl, and the entire unit is 15 m thick. The total resource of palygorskite is estimated at about 9 million tonnes.The sediments are believed to have been deposited in a brackish, lacustrine environment. Originally, tectonic stability and an arid climate favored the formation of sepiolite at about pH 8. Later, after significant weathering of the source rocks, detrital illite was transformed to palygorskite in the Mg- and Si-rich waters. Here, palygorskite was also precipitated directly.
Transformation of Iron-Bearing Kaolinite to Iron-Free Kaolinite, Goethite, and Hematite
Authors: Rozenson Israel , Spiro Baruch , Zak Israel 
Published: August 2006

AbstractFerruginous clay partings in limestones of the marine, largely evaporitic, Upper Triassic Mohila Formation (Makhtesh Ramon, Israel) contain hexagonal plates and cube-like bodies up to one millimeter across. Analyses by electron microscopy, infrared and Mössbauer spectroscopy, and X-ray powder diffraction indicate that the matrix contains Fe-rich anhedral kaolinite, up to 100 μm in size; the hexagonal plates are composed of euhedral, Fe-free kaolinite covered with well-developed acicular goethite and platy hematite (0.5 to 2 μm in size), and the cubes consist of fine-grained goethite with minor amounts of kaolinite. The anhedral kaolinite appears to be detrital, the hexagonal plates to be authigenic, and the cubes to be pseudomorphs after pyrite. Oxidation appears to have altered Fe-rich kaolinite and pyrite to Fe-free kaolinite, goethite, and hematite and was accompanied by recrystallization and pseudomorphic replacement. The alteration process was slow and was probably induced by a small increase in pH and in the Al/Fe ratio, resulting from oxidation of reduced components (pyrite, ferrous carbonate, organic matter) in a semiclosed, sediment-mud system. Overlying kaolinitic flint clay deposits may be the final product of a similar process.
Clay Minerals in the 1980 Deposits from Mount St. Helens
Authors: Pevear D. R. , Dethier D. P. , Frank D. 
Published: August 2006

AbstractPhyllosilicates are major components of the <2-μm fraction (1–3 wt. % of most bulk specimens) in more than 50 samples of air-fall tephra from several 1980 eruptions of Mount St. Helens. In all samples, trioctahedral smectite is the major clay mineral. The integral series of 00ℓ reflections in ethylene glycol-treated samples indicates a lack of interstratification; absence of a peak near 5 Å after heat treatment, the 060 peak at 1.54 Å, and energy dispersive chemical analyses indicate that the smectite is a Mg- and Fe- rich, trioctahedral saponite. Minor mica and chlorite are present in the <2-μm fraction of most samples, and some samples show a peak near 12 Å after heating to 550°C which is probably due to the presence of an interstratifled chlorite/collapsed smectite or chlorite/collapsed vermiculite. The tephra contains glass and crystals originating from new magma and lithic fragments incorporated from the pre-existing cone. The clay minerals in the tephra are lithic components stripped from older, hydrothermally altered rocks during explosive ejection. Cleaned pumice fragments, which are new magmatic components, lack smectite, but contain rare biotite in xenoliths. Old, hydrothermally altered rocks from the volcano's summit and from the debris-avalanche (former north flank) contain saponite together with chlorite and chlorite/smectite which may have formed from it. Saponite and zeolites that precipitated from neutral to alkaline hydrothermal solutions line cavities in some of these rocks. The saponite was probably not subjected to magmatic temperatures because heating this material for 5 min at 750°C collapses it irreversibly to 10 Å. Kaolinite, alunite, and opal, indicative of acid-sulfate alteration, were found only in the pre-1980 summit crater and the southwest thermal area, but were not evident in the lithic components of the 1980 deposits.
Smectite in Marine Quick-Clays of Japan
Authors: Egashira Kazuhiko , Ohtsubo Masami 
Published: August 2006

AbstractClayey sediments of marine origin having sensitivities (ratio of undisturbed to remolded shear strength) as high as 1000 at a reduced salt concentration are found around Ariake Bay, Kyushu, Japan. The clay fraction of the sediments contains smectite as a principal mineral (33–42%) in contrast to the illitic composition of most previously described quick-clays. However, this smectite is a low-swelling type, and the Na-form expands only to about the same extent as the Ca-form and gives a sediment volume almost equal to that of the Ca-clay. This low-swelling smectite appears to consist of packets of unit layers even after saturation with Na, and thus reacts like the kaolinite or illite of conventional quick-clays.
Effect of the Removal of Reactive Surface Material on the Solubility of Synthetic Gibbsites
Authors: Bloom P. R. , Weaver R. M. 
Published: August 2006

AbstractThe solubility of four different gibbsite preparations was measured, including two commercial hydrated aluminas produced by Alcoa, a Fisher ACS-grade Al(OH)3, and a laboratory preparation. The Alcoa samples and the laboratory-prepared sample had been studied previously by other investigators but without using a long-term acid treatment. Scanning electron microscopy showed globular surface material that was removed by a 14-day, 0.1 M HCl treatment. Solubility was determined at pH 4 from both over-and undersaturation with continuous agitation for 228 days. The acid treatment correlated with a decrease in log*Kso[*KSO = (Al3+)/(H+)3] of about 0.5 units. The mean solubility of the three acid-treated commercial gibbsite samples was log*Kso = 7.55 ± 0.055 (*Kso = 3.5 × 107). The solubility of the acid-treated laboratory preparation was log*Kso = 7.86 (*Kso = 7.2 × 107). The greater solubility of the laboratory-prepared gibbsite is attributed to a greater concentration of structural defects in the crystals.
Structural Model for Benzidine-Vermiculite
Authors: Slade P. G. , Raupach M. 
Published: August 2006

AbstractA combination of X-ray diffraction, infrared, and chemical data has established that the ion exchange of vermiculite with singly charged benzidine cations in an aqueous solution at pH 1.6 results in a black, highly ordered benzidine-vermiculite intercalate. The intercalate has a basal spacing of 19.25 Å and a primitive unit cell with “a” and “b” edges parallel and equal to those of vermiculite. The number of benzidine molecules per cell is equal to its electric charge. In this structure the benzidine molecules are steeply inclined to the silicate surfaces and close-packed within domains. The domains contain alternating rows of benzidine cations; from row to row the planes are either approximately parallel or perpendicular to the (120) plane, but along any one row the planes of the aromatic rings are parallel to each other. Hydrogen bonding operates between amine nitrogens and surface oxygens.
Adsorption and Catalytic Decomposition of 4-Nitrobenzenesulphonylmethylcarbamate by Smectite
Authors: Fusi Paolo , Ristori Giuseppe Gabriele , Franci Marco 
Published: August 2006

AbstractAdsorption and catalytic decomposition of 4-nitrobenzenesulphonylmethylcarbamate (herbicide Nisulam) on Upton, Wyoming, bentonite saturated with different cations was studied using thin-layer chromatography and infrared spectroscopy. Nisulam is adsorbed at room temperature by coordination through the NO2 group to the exchange cation regardless of the cation's nature. On moderate heating (75°–90°C) this molecule decomposes to 4-nitrobenzenesulphonamide whereas a similar compound (herbicide Asulam) containing the NH2 functional group instead of NO2 is adsorbed by protonation at room temperature and decomposes into different products. For cations having a high polarizing power, a coordination bond between the Asulam molecule's C=O group and the exchange cation is established, and the molecule decomposes to sulphanilic and carbamic acid. In contrast, for cations having a low polarizing power there is no coordination, and the molecule decomposes mainly into sulphanilamide. Nisulam's coordination to the exchange cation through the NO2 group instead of C=O is ascribed to inductive and conjugation effects, typical of the nitro group.
Origin of Magnesium Clays from the Amargosa Desert, Nevada
Authors: Khoury Hani N. , Eberl Dennis D. , Jones Blair F. 
Published: August 2006

AbstractDeposits of sepiolite, trioctahedral smectite (mixed-layer kerolite/stevensite), calcite, and dolomite, found in the Amargosa Flat and Ash Meadows areas of the Amargosa Desert were formed by precipitation from nonsaline solutions. This mode of origin is indicated by crystal growth patterns, by the low Al content for the deposits, and by the absence of volcanoclastic textures. Evidence for low salinity is found in the isotopic compositions for the minerals, in the lack of abundant soluble salts in the deposits, and in the crystal habits of the dolomite. In addition, calculations show that modern spring water in the area can precipitate sepiolite, dolomite, and calcite following only minor evaporative concentration and equilibration with atmospheric CO2. However, precipitation of mixed-layer kerolite/stevensite may require a more saline environment. Mineral precipitation probably occurred during a pluvial period in shallow lakes or swamps fed by spring water from Paleozoic carbonate aquifers.
Thin-Film Analysis of Clay Particles Using Energy Dispersive X-Ray Analysis
Authors: White G. N. , Berkheiser V. E. , Blanchard F. N. , Hallmark C. T. 
Published: August 2006

AbstractA standardless method of energy dispersive X-ray fluorescence in conjunction with scanning electron microscopy was used to analyze selected areas of clay-size particles of talc, pyrophyllite, and kaolinite supported by a carbon planchet. Peak intensity ratios of fluorescing elements relative to silicon were converted directly to weight or mole ratios using conversion factors determined theoretically. The conversion factors depend upon particle thickness and mass adsorption coefficients of the sample for the elements analyzed. The effects of particle thickness become significant above ~0.1 μm. Without using particle thickness corrections, the mean molar ratios of metal to Si agreed to within 6.1,0.5, and 9.7% of the theoretical ratios for kaolinite, pyrophyllite, and talc, respectively.
A Model of Clay Swelling and Tactoid Formation
Authors: Kleijn W. B. , Oster J. D. 
Published: August 2006

AbstractAn electrostatic model for the stability of clay tactoids (stacks of parallel clay platelets at ~10 Å separation) in an aqueous solution has been developed. The counter ions located in the interstitial water layers are assumed to be in equilibrium with the bulk solution. Generally, the counter-ion charge density is slightly different in magnitude from the platelet charge density. Approximating the discrete charges by homogeneously charged planes, a one-dimensional potential distribution can be calculated. From this the Gibbs energy of electrostatic interaction (using single platelets as a reference) can be computed. The model predicts that clay minerals with high (vermiculite, mica) and low (pyrophyllite, talc) degrees of cationic substitution form stable tactoids. For smectites, charge density, electrolyte concentration, and counterion species determine the swelling characteristics. At a particular charge density, lower valences of the counter ions and lower electrolyte concentrations lead to increased swelling. If tactoids are formed, the number of platelets is governed by a dynamic equilibrium between electrostatic forces, van der Waals forces, and external forces, such as shear forces due to hydrodynamic flow.