Showing papers on "Vermiculite published in 1985"

Si, Al distribution in micas; analysis by high-resolution 29 Si NMR spectroscopy

Abstract: The analysis of 29Si MAR-NMR spectra of micas and vermiculite shows that the two main factors that govern the Si, Al distribution in the tetrahedral sheet of these minerals are: (i) Loewenstein's rule (avoidance of Al-O-Al linkages), and (ii) local balance of charges. In muscovite, phlogopite and vermiculite, Al is randomly distributed in hexagonal ring sites (meta and para dispositions equally favoured), but complying with the two above restrictions. In margarite Si and Al are observed to alternate strictly, in agreement with previous X-ray diffraction analysis.

Determination of layer-charge density of expandable 2:1 clay minerals in soils and loess sediments using the alkylammonium method

Abstract: A B S T R A C T : The alkylammonium adsorption method for the determination of layer-charge density was slightly modified and applied to mixtures of expandable clay minerals (i.e. predominantly 18 A minerals after glycerol sorption) from two loess samples and two soils (Haplaquept and Aquentic Chromudert) having different K-adsorption properties. The layer-charge density of the so-called 18 A minerals from these sediments and soil samples varied between --0.23 and -0.85 per formula unit, which suggested the presence of different amounts of vermiculite within the 18 A minerals. The amounts of these vermiculites were related to K-fixing and K-buffering properties of the different samples. High-resolution electron micrographs of vermiculites saturated with tetradecylammonium exhibited a basal spacing of 25 .A. It was confirmed, that the alkylammonium ions in the interlayers of the vermiculites formed a paraffin-type structure. In the fine clay from the loess samples an interstratification of vermiculite and illitic layers was observed. In order to understand the cation exchange behaviour of soils containing smectites and vermiculites it is important to quantify these two mineral species. The direct measurement of the expansion of layer-silicates may help to explain the adsorption/desorption behaviour of expandable clay minerals in sediments and their relation to clay mineral transformation in soils. Knowledge of the layer charge is also essential to differentiate smectites from vermiculites. Glycerol and ethylene glycol methods are probably not adequate for this purpose, though they have been in common use for some time (Brindley, 1966). Adsorption of n-alkylammonium ions offers a way of measuring the layer-charge density of smectites and vermiculites and also the charge heterogeneity of low-charge vermiculites (Lagaly & Weiss, 1971; Lagaly et al., 1976; Lagaly, 1981, 1982). The alkylammonium ions are arranged with their chains lying flat or tilted (paraffin-type), the former being typical for low-charge silicates and the latter for high-charge ones (Stul & Mortier, 1974; Lagaly & Weiss, 1975). Special embedding and sectioning procedures (Vali, 1983) allow n-alkylammonium-saturated silicates to be cut perpendicular to the a-b plane; because of the stability of expanded n-alkylammoniumsaturated layer-silicates, the layer distances are preserved. Electron micrographs show clearly the layer-sequence in clay mineral mixtures from sediments and soils. Although some information on the use of the n-alkylammonium procedure for the determination of layer-charge heterogeneity of pure clay minerals is available, such information on mixed clay fractions from soils and sediments is scanty. The purpose of the present investigation was to determine the layer charge of the 'glycerol 18/~ clay mineral

Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite1

Abstract: To test the double-layer theory of swelling as applied to layer silicates, the interlayer separation, λ, in a Li-saturated vermiculite from Grouse Creek, Utah, was measured as a function of the swelling pressure, II. An oriented sample of the vermiculite (46-105 μm) was placed in an environmental chamber mounted on an X-ray diffractometer and compressed between N2 gas and a porous membrane in contact with a solution draining to the outside atmosphere. After equilibration at each of several successively higher gas pressures, the c-axis spacing was measured by X-ray diffraction, and the corresponding X was calculated by subtracting the thickness of an elementary silicate layer. The results of these measurements showed that. (1) the relation between II and λ for vermiculite is the same as that previously observed for Na-montmorillonite, i.e., II is an exponential function of 1/λ. (2) the values of II predicted by double-layer theory are much smaller than those observed if the surface potential is assigned the appropriate value; an. (3) the observed relation between II and λ does not have the form predicted by this theory. On the basis of these results, a repulsive force not ascribable to double-layer overlap must be primarily responsible for swelling; this force must result from the in-depth perturbation of the water by the surfaces of the vermiculite layers.

Transformation of vermiculite to pedogenic mica by fixation of potassium and ammonium in a six-year field manure application experiment

Abstract: In a field experiment in which heavy applications of liquid dairy manure were added annually for 6 yr to a vermiculite-containing corn-cropped sandy clay loam soil (Mountain series), fixation poten...

Insulating cementitious mixture and method of use.

Abstract: A cementitious mixture including water-repellent vermiculite, polypropylene fibers and cement A preferred embodiment utilizes: asphalt-coated, expanded vermiculite; collated, fibrillated polypropylene fibers; and non-shrinking Portland cement Test data indicates a greatly increased compressive strength compared to previously known vermiculite insulating concretes A pre-fabricated building panel utilizing the mixture of the present invention, and a method of manufacture thereof, are also disclosed Calculated R values indicate good thermal insulating characteristics

Oxygen isotope changes during mica alteration

Abstract: Oxygen isotope analyses (δO18) of micas that were artificially depleted in K+ indicate little or no isotope exchange during the transformation. The oxidation of iron in K-depleted, iron-rich micas by H2O2 treatment resulted in 1.6 to 4.6% decrease in SO18 due to the fact that the equilibrium fractionation factor is less than the initial difference between the starting δO18 of the fluid and micas. The oxygen isotope ratio of a saponite formed by the weathering of phlogopite showed a 9.7% increase in δO18 due to authigenic recrystallization. These results suggest that oxygen isotope ratios can be used to determine the nature of chemical transformation during the weathering of mica to vermiculite and/or smectite.

Relationship between exchangeable and total magnesium in Pennsylvania soils

Abstract: The particle size distribution, total and exchangeable Mg, and mineralogical compositions were determined on eight well-drained, noncultivated subsoils from Pennsylvania. No correlation was found between the clay content and total Mg (r =.29), or between the clay content and exchangeable Mg (r =.35). Serpentine, talc, and hypersthene were found in the very fine sand and silt fractions of soils having relatively high exchangeable Mg. Mica and 14-A clay minerals were the only Mg-bearing minerals noted in the same fractions of soils having relatively low exchangeable Mg. Of the Mg-bearing clay minerals found in the clay fractions (smectite, vermiculite, chlorite, illite, and interstratified chlorite/vermiculite), only smectite decreased as the exchangeable Mg in the soils decreased. Two distinctly different distribution patterns of Mg were found for soils having relatively high and low exchangeable Mg. The former soils showed a decreasing Mg content as the particle size decreased, and the latter soils showed the opposite. Exchangeable Mg correlated significantly with the amount of Mg in whole soil, sand, and silt, but not with the amount of Mg in the clay, an indication that sand and silt but not clay were the important sources of exchangeable Mg in these soils.

Fixation of zinc by some rice soil clays under upland conditions

Abstract: Because of widespread Zn deficiency in rice, an experiment was designed to evaluate the Zn fixing capacity of several clay minerals separated from tropical rice soils. The study involved the addition of 25 μg Zn per g of clay as zinc sulphate, incubation at an ambient temperature of 30 C±2 followed by alternate wetting and drying and extraction by 0.005 M DTPA to assess the magnitude of Zn fixation. On average, 57% of the applied Zn was unextractable by 0.005 M DTPA and considered fixed. The dominantly biedellite clay systems possessed the highest capacity to fix Zn (70%), followed by vermiculite (59%) and montmori‐llonite (55%). Clay systems containing hydrous mica impregnated with important proportions of kaolinitic and vermiculitic type minerals fixed 40% of the added Zn. Most of the clays, consisting of mixed mineralogy, fixed more than 50% of the applied Zn.

Thermal properties of heat insulators in the vermiculite-phosphate system.

Abstract: The effect of firing operation on the thermal properties of heat insulators in the vermiculite-phosphate system was investigated by measuring their compressive strength and thermal conductivity.The aggregates used were the raw vermiculite from Fukushima Prefecture, Japan and Palaboroa area, N.E. Transvaal, S. Africa, and the bonding material of aggregates was sodium metaphosphate. Magnesium dihydrogen phosphate and aluminum dihydrogen phosphate were tried as the additives.The compressive strength was increased when a proper quantity of magnesium dihydrogen phosphate was added to the vermiculite-sodium metaphosphate system. This was attributed to the formation of bridge bonds due to the reactions of magnesium oxide component in vermiculite with sodium metaphosphate and magnesium dihydrogen phosphate. A considerable decrease in strength was observed when aluminum dihydrogen phosphate was added. This was explained by the X-ray diffraction evidence that alminum dihydrogen phosphate did not react with vermiculite. The thermal conductivity of the vermiculite-phosphate system was considerably smaller than that of the expanded vermiculite-bond clay-phosphate system or the expanded vermiculite-portland cement system. This corresponded to the porosity increase caused by the dehydration reaction of magnesium dihydrogen phosphate with raw vermiculite on firing.

Effect of soil organic matter oxidation on the collapse of vermiculite

Abstract: Oxidation of organic matter with H2O2 produced substantial amounts of NH3 which was then fixed by vermiculite, causing partial or complete collapse and converting the mineral to a mica-like product. The collapse of the mineral was indicated by shifts in the 001 spacing from 1.476 to 1.030 nm and the appearance of a well-defined band at 1430 cm−1 in the IR spectrum, indicative of the presence of NH4+ in the interlayer positions of the clay. Our data suggest that: (a) the transformation of vermiculite to mica during H2O2 oxidation may result in underestimation of the vermiculite content of soils by XRD, and (b) the wide occurrence of mixed-layer minerals in soils may in part have resulted from the fixation of NH3 liberated from the microbial mineralization of organically bound N. Key words: Ammonia, X-ray diffraction, IR spectrophotometry, mixed-layer minerals, H2O2 pretreatment

Invloed van bewerking en besproeiing op die verwering van gneis in die Augrabies-gebied

Abstract: Influence of cultivation and irrigation on the weathering of gneiss in the Augrabies area. Physical, chemical and mineralogical criteria were used to determine whether any changes in the properties of soils derived from gneiss in the Augrabies area occurred as a result of cultivation and irrigation. The evidence suggests that cultivation and irrigation have caused an increase in the rate of weathering and soil formation. The A horizons of cultivated soils had higher clay contents as well as CEC values than uncultivated soils. Sand and silt fractions of most of the cultivated and uncultivated soils consisted mainly of quartz, feldspar (especially albite) and hornblende. Small amounts of vermiculite and mica occurred in the silt fraction. Clay fractions of the uncultivated soils consisted mainly of smectite, mica and quartz. Kaolinite dominated in the horizons of the soils that had been irrigated for more than 10 years. Some of the Rand C horizons of cultivated soils showed very strong vermiculite peaks. A horizons of cultivated soils had higher exchangeable potassium and percentage carbon values than uncultivated soils. The former is probably caused by weathering and/or fertilization and the latter can be ascribed to the greater production of plant material on the irrigated land.

QM polymers and other products derived from parabola vermiculite

Abstract: The trimethylsilylation of parabola vermiculite gives polyorganosiloxanes of the structure QxMy. (Q = SiO42: M = ((CH3)SiO12) which will form gels in a wide range of organic solvents and resins. No other mineral has so far been reported to yield trimethylsilylated products capable of forming gels. The effect on the nature and yields of these QM polyorganosiloxanes' of variation in reaction time, particle size and vermiculite/hexamethyldisiloxane ratio have been investigated. The QM polyorganosiloxanes produced are hydrophobic insoluble powders which gel in a wide range of organic solvents. Reaction with NaOH/EtOH mixtures gives ‘silicone-silicate’ hybrids by replacement of trimethylsilyl groups with sodium ions. i.e. ‘QMNa’ products. The ability of these products to form films is compared to that of parabola vermiculite itself and also acid-leached vermiculite. QM polyorganosiloxanes give films which can either be peeled off as an integral film or, after heating on a glass slide at 50°C. will give a hard hydrophobic surface. Preliminary investigation has also shown that QM polymers can be used as fillers in epoxy resins.