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Electrokinetic Phenomena in Colloidal Clays
Cambridge University Press (CUP) - Tập 4 - Trang 225-239 - 1955
D. T. Oakes, Emil J. Burcik
While the variations of the physical properties of colloidal suspensions of bentonite clays under various conditions of contamination have been the subject of extensive investigations, the role of the associated electrical phenomena in the impartation of these physical properties is virtually undefined. Successful techniques for the measurement of the electrical phenomena have been reported previously but they are applicable only to very dilute clay suspensions in which negligible electrical interference between clay particles exists. Apparatus and techniques applicable to concentrations of colloidal material normally used in bentonite oil-well drilling fluids were developed and are discussed. Measurement of electrokinetic phenomena in concentrated suspensions was effected by application of the principle of electroosmosis by suitable modification of existing apparatus. The distinguishing modification was replacement of the conventional, consolidated diaphragm with a diaphragm of colloidal material supported by thin membranes. The applicability of the apparatus and techniques is demonstrated by qualitative comparison with data of previous investigations wherein the comparable depression of the electro-kinetic potential by the addition of various contaminating ions is shown. In addition, the relation between the measured electrokinetic potential and the filtration rate is shown to be linear and independent of the valence or type of contaminant for a major portion of the investigated concentration range. This suggests that for ions which appreciably repress the electrokinetic potential the fluid-loss may be used as a means of approximating the changes of the electrokinetic potential.
Synthesis of Highly Microporous and Hydrophilic Alumina-Pillared Montmorillonite: Water-Sorption Properties
Cambridge University Press (CUP) - Tập 38 - Trang 363-372 - 1990
P. B. Malla, S. Komarneni
A montmorillonite exchanged with large hydroxy-Al cations was thermally treated to convert the hydroxy cations to oxide pillars and to generate permanent microporosity in the interlayers. The pillared clay products were characterized by X-ray powder diffraction (XRD) and water-sorption measurements to delineate the effect of aging of the pillaring solutions, the methods of drying and concentration of clay-water suspensions, and the temperatures of calcination on micropore volumes. Although samples prepared at different conditions gave d(001) reflections of 17–17.5 Å, at least to 500°C, the concentrations of clay-water suspensions and the temperatures of calcination significantly changed the pore-size distribution and the volume of micropores present in the sample, as calculated from the water-sorption isotherms. A narrow pore-size distribution having little or no macroporosity or external surface condensation was observed in samples prepared by the addition of the pillaring solution directly to the clay (solid) without first making a clay-water suspension and calcining the sample at ≥400°C. About 87% of the total volume was found to be micropores of ≤14–17 Å in the sample calcined at 600°C. Aging the pillaring solution, however, did not influence either the water-sorption isotherms or the XRD patterns significantly under the conditions specified. Essentially the same results were obtained for samples prepared from both hydroxy-Al polymer (OH/Al = 2) and aluminum chlorohydrol (ACH) solutions. Although alumina-pillared clays exhibited an extreme type-I isotherm (Langmuir type) for nitrogen adsorption, the sorption of water vapor gave an isotherm of unusual shape that fit neither a BET nor a Langmuir equation. This latter behavior has previously been attributed to a unique pore size and hydrophobicity and is apparently common to all pillared montmorillonite materials. The hydrophobicity of the pillared clay apparently developed on calcination by the migration of protons from the interlayers to the octahedral sheets, in which sites of cationic substitution (negative charge) were located. Protons migrated back to the interlayers by treatment with NH3, which subsequently converted to NH4+ in the interlayers. The exchange of the NH4+ by Ca2+ introduced hydrophilicity to the alumina-pillared clay, which was reflected both in the shape of the water isotherm (close to moderate Brunauer type I), the heat of sorption, and the total sorption capacity.
Brucite identified as crystallizing from a natural cold alkaline spring gel
Cambridge University Press (CUP) - Tập 19 - Trang 335-336 - 1971
Robert W. Luce
Dehydration of Synthetic Hydrated Kaolinites: A Model for the Dehydration of Halloysite(10Å)
Cambridge University Press (CUP) - Tập 33 - Trang 415-423 - 1985
P. M. Costanzo, R. F. Giese
Several hydrates can be synthesized from well-crystallized kaolinites; of importance to the present work are a 10-Å hydrate (called the QS-10 hydrate), an 8.6-Å hydrate, and two kinds of partially dehydrated mixed-layer hydrates. One kind is a series of unstable materials with d(001) varying continuously between 10 and 8.6 Å, and the other kind is stable with d(001) approximately centered at 7.9 Å. The 10- and 7.9-Å phases have been observed in halloysites by many workers using X-ray powder diffraction, and the 8.6-Å phase has been seen by others in selected area electron diffraction photographs. Infrared spectra reveal additional similarities between the synthetic hydrates and both halloysite(10Å) and partially dehydrated halloysites. Because of these similarities, the synthetic hydrates can be used to develop a model for the dehydration of halloysite(10Å). Previous work on the 10- and 8.6-Å hydrates identified two structural environments for the interlayer water. In one, the water is keyed into the ditrigonal holes of the silicate layer (hole water), and in the other, the water is more mobile (associated water). Both types are found in the QS-10 hydrate and halloysite(10Å), whereas only hole water occurs in the 8.6-Å hydrate. In the QS-10 hydrate, stronger hydrogen bonding between hole water and the clay makes the hole water more stable than the associated water. This difference in stability is responsible for a two-step dehydration process. The first step is the loss of associated water which results in a material with d(001) = 8.6 Å. This stable hydrate must be heated to temperatures near 200°C to drive off the remaining hole water. The less perfect structure of halloysite and its common curvilinear morphology reduce the difference in stability between hole and associated water molecules, so that when halloysite(10Å) dehydrates, loss of hole water and associated water overlaps, and the d-spacing goes directly to 7.2–7.9 Å.
Mineralogy from Geochemical Well Logging
Cambridge University Press (CUP) - Tập 34 - Trang 204-213 - 1986
Michael M. Herron
Multivariate statistical analyses of geochemical, mineralogical, and cation-exchange capacity (CEC) data from a Venezuelan oil well were used to construct a model which relates elemental concentrations to mineral abundances. An r-mode factor analysis showed that most of the variance could be accounted for by four independent factors and that these factors were related to individual mineral components: kaolinite, illite, K-feldspar, and heavy minerals. Concentrations of Al, Fe, and K in core samples were used to estimate the abundances of kaolinite, illite, K-feldspar, and, by subtraction from unity, quartz. Concentrations of these elements were also measured remotely in the well by geochemical logging tools and were used to estimate these mineral abundances on a continuous basis as a function of depth. The CEC was estimated from a linear combination of the derived kaolinite and illite abundances. The formation’s thermal neutron capture cross section estimated from the log-derived mineralogy and a porosity log agreed well with the measured data. Concentrations of V, among other trace elements, were modeled as linear combinations of the clay mineral abundances. The measured core V agreed with the derived values in shales and water-bearing sands, but exceeded the clay-derived values in samples containing heavy oil. The excess V was used to estimate the V content and API Gravity of the oil. The log-derived clay mineralogy was used to help distinguish nonmarine from transitional depositional environments. Kaolinite was the dominant clay in nonmarine deposits, whereas transitional sediments contained more illite.
Hydrogen-Isotope Exchange in Halloysite: Insight from Room-Temperature Experiments
Cambridge University Press (CUP) - - 1999
Jean C.C. Hsieh

Halloysite is a common pedogenic clay mineral, often found in young soils developed on volcanic deposits (Dixon, 1989), It is a member of the kaolin group of clays with the same ideal stoichiometric composition as kaolinite [Al2Si2O5(OH)4]. Halloysite, however, often contains water of hydration (i,e., Al2Si2O5(OH)4·nH2O), and is commonly found with a tubular morphology, This “rolling” of halloysite has received a great deal of study because there is no generally agreed upon mechanism for the process and there is no corresponding phenomenon in natural kaolinite (e.g. , Bates et al., 1950; Bailey, 1989; Singh, 1996; Singh and Mackinnon, 1996). The crystal structure of halloysite often shows stacking disorder. This property, combined with a rolled morphology, makes identification by X-ray diffraction (XRD) difficult. The XRD peaks at 7.5, 4.4, and 3.6 Å are often asymmetric with a large width at half peak height (Bailey, 1989).

Forthcoming Papers
Cambridge University Press (CUP) - Tập 58 - Trang 587-587 - 2010
Occurrences of Shales Partially Altered to Pyrophyllite
Cambridge University Press (CUP) - Tập 6 - Trang 386-391 - 1957
Arthur J. Ehlmann, L. B. Sand
Examination of samples from shale outcrops on the periphery of the Utah Valley graben has revealed an unusual association of disseminated pyrophyllite with various clay minerals. Numerous samples were obtained from exposures in brick clay pits located in the Manning Canyon formation of Mississippian-Pennsylvanian age and from the Long Trail member of the Great Blue formation of Mississippian age. Associated clay minerals in these beds include illite, illite-montmorillonite mixed-layer clays, 7 Å chlorite, 14Å chlorite, kaolinite and sericite. Associated nonclay minerals include quartz, calcite, and small amounts of dolomite. Associated secondary minerals are calcite, aragonite, jarosite, gibbsite and gypsum. Three possible explanations of genesis have been considered in the present study: deposition of detrital pyrophyllite, surface weathering under special conditions, and hydrothermal or pneumatolytie activity. The third alternative explanation, hydrothermal or pneumatolytie activity, is believed to be the most acceptable. It is hypothesized that magnesium, iron, and interlayer cations have been removed from some of the original 2 : 1 layer clays in the shale by solutions localized along fault zones.
Adsorption of 1,10-Phenanthroline by Some Clays and Oxides
Cambridge University Press (CUP) - Tập 28 - Trang 149-154 - 1980
S. G. de Bussetti, E. A. Ferreiro, A. K. Helmy
The adsorption of 1,10-phenanthroline (OP) onto some clays and oxides was studied as a function of concentration, pH, and time. The adsorption was found to be irreversible and the isotherms, except for silica gel, were hyperbolic and gave rise to plots similar to that of Langmuir. Kinetic and light scattering studies show that OP is adsorbed as a micellar unit composed on the average of 3.5 molecules/micelle. This fact explains the overestimation observed in the surface areas of some sorbents since no true monomo-lecular layer of OP is formed on the surfaces. The adsorption was also found to be pH dependent, attaining a maximum, independent of the sorbent, at about pH 6. This maximum was approximately at the same pH in which only the molecular form of OP began to be present. The partial desorption of OP as the pH increased beyond 6 is possibly associated with the aggregation of micelles on the surfaces.
Characterization of Expandable Clay Minerals in Lake Baikal Sediments by Thermal Dehydration and Cation Exchange
Cambridge University Press (CUP) - Tập 53 - Trang 389-400 - 2005
Tomas Grygar, Petr Bezdicka, David Hradil, Michaela Hruskova, Katerina Novotna, Jaroslav Kadlec, Petr Pruner, Hedi Oberhansli
The sedimentary series from Academician Ridge, Lake Baikal, eastern Siberia, was examined using cation exchange capacity (CEC) to estimate the amount of expandable clay minerals (ECM) and high-temperature X-ray diffraction (HT-XRD) to determine their basic classification. The comparison of the magnetic susceptibility (MS) at sub-millennial resolution and the δl8O record of a reference Atlantic core (ODP 980) was used to create an age model. The most closely studied part of the series covered the major part of the last glacial cycle (120–20 ky BP). The HT-XRD analysis is based on monitoring the course of ECM dehydration with 5°C steps between 25 and 250°C and enabled us to improve the discrimination between ECM, chlorite and micas. The CEC obtained at millennial resolution showed that the neoformation of ECM in warmer periods of the last interglacial was either insignificant or fully compensated by their dissolution or dilution. The CEC record was correlated with the main climatic stages in the period studied. Both MS and CEC records reflected the environmental changes at about millennial resolution, including climatic instabilities between 117 and 73 ky BP (late MIS5).
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