Showing papers on "Vermiculite published in 1988"

Transmission electron microscope study of biotite weathering

Abstract: Transmission electron microscopy suggests that biotite transforms to vermiculite primarily by direct structural modification, involving the replacement of K+ by hydrated interlayer cations, and only minor reorganization of the 2:1 layer. A second relatively uncommon mechanism appears to involve redistribution of components from two biotite sheets to form a single vermiculite layer. Distortion of the surrounding structure initially inhibits growth of vermiculite in the surrounding biotite, and promotes the propagation of vermiculite layers in opposite directions. This phenomenon may contribute to the development of relatively regular, widely spaced interstratifications of biotite and vermiculite. Additional components and space are provided by the dissolution of biotite where access of solutions is greater. During weathering, biotite and vermiculite become increasingly replaced by kaolinite, which crystallizes epitactically onto existing layers, and goethite, which develops from a poorly crystalline iron oxyhydroxide precursor to form oriented laths. In areas parts of strongly weathered samples kaolinite and goethite appear to develop in proportions consistent with a reaction that conserves both Al and Fe.

Weathering of Chlorite and Vermiculite in Ultramafic Rocks of Cabo Ortegal, Northwestern Spain

Abstract: Chloritic veins in serpentinite and their weathering products were analyzed by X-ray pow- der 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 (mlL9Fea+0.zFe2+ o.4Mg9.2Cr0.z)(S is.sA12.2)O20(OH )l 6 and Xl.3(Fe3+o.7Fe2+ o.~Mg5.zNio.l)(S is.sA12.E)OEo(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 Fe 3+-rich smectite, which probably formed by precipitation from solution.

Transitional vermiculite-smectite phases in Aqualfs of southwestern Ohio

Abstract: The clay mineralogy of two Aqualfs occurring on the Illinoian till plain of southwestern Ohio was investigated in order to (i) determine the clay mineral distribution with depth, (ii) examine the clay mineral weathering sequence, and (iii) identify the 2:1 mineral species in which hydroxy interlayers had formed. Despite the presence of multiple parent materials, no obvious discontinuities in clay mineralogy were observed. A weathering sequence involving the transformation of clay mica to vermiculite to low charge vermiculite/high charge smectite occurred. Alkylammonium ion exchange data indicated that weathering created a heterogeneous charge distribution in the 1.4-nm (expandable) mineral phase resulting in mixed low-and high-charge interlayers. The low-charge interlayers readily formed bilayer complexes with ethylene glycol (1.7 nm), and also accommodated double layers of glycerol (1.8 nm) when the mean layer charge was <0.65. Reductions in layer charge were correlated with the oxidation of octahedral Fe(II) and the expulsion of K and Mg from the mineral structure. The expansion of 2:1 layer silicates in horizons near the soil surface was restricted as a result of Alhydroxy interlayering. After interlayer materials were removed with boiling 0.33 M Na citrate, the previously interlayered minerals exhibited x-ray diffraction effects following Mg saturation and ethylene glycol and glycerol solvation that were indicative of vermiculite. Journal Article no. 170-86.

Uptake of lanthanides by vermiculite

Abstract: The uptake of Ce3+, Nd3+, Gd3+, Er3+, and Lu3+ on vermiculite was studied using cation-exchange measurements, infrared spectroscopy (IR), and X-ray powder diffraction (XRD). The reaction was followed by measuring the amount of lanthanide ions (Ln3+) taken up by n-butylammonium-ex-changed vermiculite in relation to amount of Ln3+ salt added and the pH of the equilibrium solution. The amount of Ln3+ taken up in excess of the CEC value increased with the hydration energy of the lanthanide ion and with the pH of the n-butylammonium-exchanged vermiculite suspension. At equilibrium solution pHs of 3–4.5, the uptake of Ln3+ ions was only slightly greater than the CEC, whereas at pHs >4.5 the amount taken up by the vermiculite increased sharply. The uptake of Ln3+ ions beyond the CEC of the vermiculite is probably related to the hydrolysis of Ln3+ ions on the vermiculite interlayer surface. The appearance of a band at 1715–1720 cm−1 in the IR spectra of the Ln3+-exchanged vermiculite suggests a strongly acidic medium in the interlayer space. The Ln3+-exchanged vermiculites gave XRD patterns having 002/001 intensity ratios greater than that of Mg-exchanged vermiculite.

Aqueous suspension of delaminated vermiculite

Abstract: It has been found that water stable articles, such as films and sheets, can be prepared from chemically delaminated vermiculite platelets if radical or ionically polymerizable organo-substituted onium salts are ionically bonded to the platelets and the resulting system cured.

Non-dispersible vermiculite products

Abstract: Provided is a process for the production of shaped vermiculite articles having excellent resistance to water dispersibility from an aqueous dispersion of vermiculite lamellae having incorporated therein a cationic polyquaternary ammonium salt.

Aqueous mineral dispersions

Abstract: A process for making vermiculite lamellae that includes delamination of vermiculite ore to produce a dispersion con­taining vermiculite particles in which an aqueous slurry of unexpanded vermiculite ore, that is untreated by heat or de­laminating chemicals, is subjected to a shearing action until a dispersion of vermiculite lamellae having dimensions less than 200 microns is produced.

Insulating material containing delaminated vermiculite

Abstract: An asbestos-free insulating material suitable for use as a header in molten metal casting. The material is made from a dry mixture comprising lime, siliceous component, delaminated vermiculite or spodumene or lithium aluminate or mixtures thereof, and optionally, wollastonite and organic fiber. The dry mixture is mixed with water to form a slurry, shaped, heated in the presence of steam, and dried to remove free water.

Water resistant mineral products

Abstract: An aqueous dispersion of vermiculite lamellae is provided having incorporated therein from about 0.2 to about 10% by weight of at least one internal sizing agent based on the dry weight of the vermiculite in the dispersion.

Contact‐uptake of iron from vermiculite by maize

Abstract: By means of modified two‐phase experiments, uptake of FeIII from vermiculite by maize (Zea mays L., cv. Mutin) was investigated. The solution phase consisted of Hoagland I with and without Fe. In the presence of FeEDDHA in the growth medium, leaf concentration of Fe was 2.5‐fold and Mg 2.3‐fold greater, P 4.8‐fold and K 1.2‐fold smaller in plants with roots in contact with vermiculite than in plants with roots suspended in nutrient solution. In the absence of FeEDDHA in the growth medium, growth was twofold, leaf concentration of Fe 4.2‐fold, chlorophyll b 4.2‐fold, and chlorophyll a 9.0‐fold greater and K 1.4‐fold, Ca 2.7‐fold, and P 5.2‐fold smaller in plants with roots in contact with vermiculite than in plants with roots suspended in nutrient solution. The leaf concentrations of Fe and chlorophyll a and b in plants receiving no FeEDDHA but having their roots in contact with vermiculite were equal to those in plants with roots suspended in solution containing 100 μmol L‐1 FeEDDHA. The data ind...

Observations at the mica-vermiculite interface with HRTEM

Abstract: Particle size fractions of biotite (0.5–2; 2–5; 5–20; 20–50 μ) were gradually transformed to vermiculite by exchanging the interlayer potassium with barium. In a subsequent exchange procedure, interlayer barium was removed by n-alkylammonium ions in order to preserve the expanded structure under the conditions in the electron microscope. Ultramicrotome sections cut perpendicular to the plane of silicate layers were prepared from samples representing different states of mica-vermiculite transformation.

Coating composition for preventing asbestos fibre pollution from asbestos/binder building material

Abstract: The invention relates to the use of a composition prepared using alginic acid and/or water-soluble salts thereof for the additional treatment of asbestos-containing building materials such as spray asbestos, asbestos cement or the like, to avoid or reduce asbestos fibre pollution in the surrounding air. Further additives used are fibre materials, such as cellulose fibres, to increase the mechanical stability of the coating and flame retardants, such as mica, perlite, vermiculite and also water-soluble polymer dispersions.

Process for production of mineral dispersions

Abstract: Disclosed is an improved process for producing dispersions of vermiculite ore particles by intercalating organo-cation salts into the vermiculite structure under shearing conditions to delaminate the ore and reduce particle size in one step.

Acidic additive having depositing, flocculating, deodorizing, and plant growth promoting action

Abstract: PURPOSE:To obtain the title additive having a depositing and flocculating capability and contg. no harmful metals by baking vermiculite to remove harmful metals such as mercury, and dissolving the obtained backed vermiculite in the aq. soln. of an inorg. acid. CONSTITUTION:Granular vermiculite is baked, for example, at 500-1,200 deg.C, or most preferably at 800-1,000 deg.C, 20-30% aq. sulfuric acid soln. is added to the baked vermiculite in the 4/(3-5) weight ratio of the baked vermiculite to the aq. sulfuric acid soln., and the mixture is allowed to stand for several hours at ordinary temp. or under heated conditions while occasionally agitating the mixture. The obtained aq. soln. is used as such, or concn. or diluted and used. As a result, although the mineral components such as Al and Mg in the raw material are eluted into the aq. sulfuric acid soln. the harmful metals such as Hg, Cd, hexavalent chromium, arsenic, and lead are eliminated. The acidic additive contg. no harmful metals such as mercury and having depositing, flocculating, deodorizing, and plant growth promoting actions is obtained in this way, and the contents of minerals are high as compared with the case where unbaked vermiculite is used.

Extraction of potassium from some kaolinitic soils of the tropics

Abstract: Three methods for soil potassium extraction (M NH4OAc pH 7, 0.01 M AgTU and 30 % hot H2SO4) were compared for a variety of kaolinitic soils of the tropics. The AgTU‐extractable K was much higher than the M NH4OAc‐extractable K when vermiculite clay was present in the soil. The correlation between both was given by an R value of 0.937. The amounts of K extracted by 0.01 M AgTU and by hot H2SO4 were approximately the same. The R value for these two methods was 0.843. It is suggested that the AgTU extractant could be used for determination of plant‐available K in soil and for testing for the presence or absence of vermiculite clay in soils.

Refractory cement of zirconium and aluminium oxide cement

Abstract: Refracting concrete is made of zirconium, aluminium oxide cement as binder and 10-50 wt.% with respect to solid constituents of refractory light material such as expanded vermiculite or pearlite, light fire clay and/or mineral fibres.