Showing papers on "Vermiculite published in 1984"

Comparison Of Kinetic Equations To Describe Potassium-calcium Exchange In Pure And In Mixed Systems

Abstract: We used first-order, Elovich, parabolic diffusion, and zero-order equations to describe the kinetics of K-Ca exchange in kaolinite, montmorillonite, vermiculite and soils of the Atlantic Coastal Plain Region. The first-order equation was the best of the various kinetic equations studied to describe the reaction rate of K adsorption in the clay minerals and soils, as evidenced by the highest simple correlation coefficients (r) and the lowest values of the standard error of the estimate (SE). The parabolic diffusion law described K adsorption best on vermiculite and soils dominated by vermiculitic clay minerals. The parabolic diffusion law did not describe K adsorption well on kaolinite and soils high in kaolinite. These differences were related to the kinds of binding sites present in the pure and mixed systems. The Elovich and zero-order equations did not satisfactorily describe K adsorption in the soils and clays. Apparent potassium adsorption rate coefficients (ka/) were 0.23, 0.58, and 2.65 h-1 for vermiculite, montmorillonite, and kaolinite, respectively. The ka/ values for the soils ranged from 0.84 to 1.86 h-1, and their magnitude was related to the type and quantity of clay minerals present.

Chemical weathering processes on the vantage peak nunatak, juneau icefield, southern alaska

Abstract: On the Vantage Peak nunatak in the Juneau Icefield of southeastern Alaska, grus and soils display evidence of extensive chemical alteration in a self-evidently periglacial environment. Accompanying the alteration of bedrock to grus and soil is a decrease in grain size. Grus is dominated by very coarse sand while the soils are predominantly fine sand. Grain-size reduction is attributed primarily to mineral grain dissolution. Total chemical analyses show that alkali earths (calcium and magnesium) and alkalis (sodium and potassium) are lost as weathering progresses, while silicon and iron increase relative to resistant elements. Secondary clay minerals present in the grus and soils appear to have been derived from clay-size primary minerals. Vermiculite is the principal secondary clay mineral and appears to have formed by the alteration of biotite. Scanning electron microscopy shows that quartz and feldspars are primarily weathered by dissolution with no evidence of feldspar transformation to secondary clays...

Potassium status of some quebec soils: k released by nitric acid and sodium tetraphenylboron as related to particle size and mineralogy

Abstract: The K release characteristics of surface samples from five Quebec soils were investigated. Each soil was fractionated by size into six separates. Each separate was extracted with 1 M ammonium acetate (NH4OAc), with 1 M nitric acid (HNO3) and with sodium tetraphenylboron (NaTPB) and the K extracted was determined. The clay separates contained most of the HNO3 and NaTPB-extractable K. The average amounts of K removed by 1 M HNO3 and NaTPB from the clay was up to 16 times more than that released from silt or sand fractions. The strong relationship between extractable K and clay content was probably due to the similarity in mineralogical composition and degree of weathering of these soils. Clay-sized chlorite and vermiculite were destroyed by the HNO3 extraction but not by the NaTPB extraction. Crop response to K fertilizer was generally reduced as clay content and extractable K increased. Key words: Extractable K, NaTPB-K, HNO3-K

Thermodynamic study of Na-K-Ca exchange reactions in vermiculite

Abstract: The exchange of Na, K, and Ca ions in vermiculite has been studied between 50 and 1500C at a total normality of 0.1. The free energy changes were negative in the Na ~ K, Ca ~ K, and Na ~ Ca exchange reactions, and the cation preference in the vermiculite was Na < Ca < K in the temperature range examined. The enthalpy changes, calculated by application of the van't Hoffequation to the relation between equilibrium constant and temperature, were positive. The cation preference in the vermiculite seems to have been largely controlled by the increase in entropy which was due to the positive values of the entropy change term in the solid for the Na-K and Ca-K exchanges and the positive values of the entropy change in the solution for the Na-Ca exchange. From a thermodynamic analysis of the cation- mixing properties in vermiculite, the observed free energy change in the Na-K exchange was determined solely by the differences of the intrinsic electrostatic binding energy of the cations on the clay surface. That in the Na-Ca exchange was interpreted by taking into account an extra interaction energy of Ca-Ca pairs in addition to the intrinsic energy change. Furthermore, an additional interaction energy between K ions and the clay surface appears to have been added to the free energy change in the Ca-K exchange. In the Na ~ K and Ca ~ K exchange reactions a structural modification occurred in the K-equivalent fraction (RI0 range 0.05--0.6, and a regularly interstratified phase of 15-A and 10-A members was formed at 0.05 < Y(K < 0.4.

Potassium exchange characteristics in relation to mineralogical properties and potassium uptake by grapes of selected soils in the niagara peninsula of southern ontario

Abstract: Potassium deficiency in grapes, as well as in other fruit crops grown on soils in the Niagara peninsula, is a common and often serious problem. Ap horizon samples from 12 of these soils and grape petiole samples from nine of the soil locations were analyzed to elucidate the behavior of the soil K and its availability to grapes. The soils ranged in texture from sandy loam to silty clay and their clay mineralogy was relatively uniform with mica as the main layer silicate. Vermiculite was quantified by potential K fixation methods and was concentrated in the clay. Up to 5.8% vermiculite was present in the soils which seemed to be sufficient to reduce K availability by K fixation. Amounts of exchangeable K extracted with NaCl or NH4Cl were relatively high (0.46–2.09 meq/100 g) but were not correlated with K uptake by grapes. Energies of K exchange obtained from immiscibly displaced soil solutions were closely related to vermiculite contents and amounts of K fixed after air drying. Energies of K exchange and r...

Mineralogical characterization of West Chestnut Ridge soils

Abstract: The morphological, physicochemical, and mineralogical properties of the soils and residua from the proposed site of the Central Waste Disposal Facility were characterized. The proposed site is underlain by cherty dolostones, limestones, and shales of the Knox Group covered by a thick residuum. Three diagnostic horizons from four soil profiles and six samples from residuum cores were selected for mineralogical analysis. The coarse fractions (gravel and sand) of the samples included different types of chert, iron-manganese oxide nodules, and quartz. The samples were high in clay content (except those from the A and E horizons) and low in pH and base saturation. The clay fractions were composed of varying amounts of kaolinite, mica, vermiculite, aluminum hydroxy-interlayered vermiculite, amorphous iron and aluminum oxides, gibbsite, and quartz. Aluminum hydroxy-interlayered vermiculite is the major component in surface horizons, but kaolinite becomes dominant in subsurface horizons of the soils. Degradation of kaolinite and formation of aluminum hydroxy-interlayered vermiculite and iron and aluminum oxides are pronounced chemical weathering processes in the surface soils. The aluminum hydroxy interlayering of vermiculite reduces cation exchange and selective sorption capacities of soils. In the residua, micaceous minerals free of aluminum hydroxy interlayering, kaolinite, and amorphous iron and aluminum oxidesmore » are major components in the clay fraction. The sorption ratios of /sup 137/Cs, /sup 90/Sr, /sup 60/Co, and the uranium isotopes expected to be in the radioactive wastes should be very high for the clays having such mineralogical composition. The low acid-buffering capacity (base saturation) of the residua suggest that the fragile chemical and mineralogical equilibria can be easily broken if an extreme chemical condition is imposed on the residua.« less

The Thermal Insulating Properties of Vermiculite

Abstract: A study has been carried out to determine the thermal insulating properties of expanded vermiculite mineral in the form of loose particles and in the form of compressed vermiculite boards. Measurem...

Method for the manufacture of fire-resistant building slabs

Abstract: of EP00431441. A method of manufacturing pressed, fireproof, three-ply building boards made from inorganic expanded material, in which method the granules of expanded material, that is to say expanded vermiculite or expanded perlite for the outer layers and/or expanded vermiculite or expanded perlite for the inner layer, are first separately glued with water glass as an inorganic bonding agent and/or with thermosetting resin and/or with monoaluminium phosphate, a first layer of glued vermiculite or glued perlite occupying 1/6 of the total thickness is then deposited, the centre layer of glued vermiculite and/or glued perlite occupying approximately 4/6 of the total thickness is deposited thereon and, finally, the second layer of glued vermiculite or glued perlite occupying approximately 1/6 of the total thickness is finally deposited thereon and, after a pre-pressing stage, this three-layer deposit is solidified under the application of pressure and heat, characterised by the method steps in which a) a mixture comprising expanded vermiculite or expanded perlite and a solution of water glass with 48-50 Be and urea is used for the outer layers of the board and is used to glue the vermiculite or the perlite, the proportion of solids in the solution being up to 41% and the proportion of moisture in the mixture being up to 40%, in each case calculated to the weight of the vermiculite or of the perlite each in its absolutely dry state, b) expanded vermiculite and/or expanded perlite and the waste products largely originating from dry waste products, namely dust occuring during expanding and the cooling of granulated material and the machining of the edges of the boards, and crushed trimming residues, are used for the centre layer of the board, and the mixture of vermiculite and/or perlite and the waste products is resinified with an approximately 70% solution of phenolic resin and is glued with a 50% solution of monoaluminium phosphate and urea, the solids content of the two components being up to 24% relative to the weight of the mixture in its absolutely dry state, the ratio of the solids of the phenolic resin to the solids of the monoaluminium phosphate being 40 : 60, the moistness of the glued mixture being up to 18%, and the glued mixture for the centre layer containing up to 17.5% less solids in the bonding agent and up to 23.4% less moisture than the glued granulated vermiculite or granulated perlite for the outer layer, c) the components serving as a bonding agent are tempered to a temperature of from 25 to 30 degrees C before glueing and are then sprayed separately onto the granulated material by conducting the expanded granulated material as a falling curtain through a mist produced by spray guns from the bonding agent, d) the three-layer deposit is solidified at a temperature between 170 and 210 degrees C, such that, commencing from a high initial pressure, the pressure exerted by the heating plates on the article being pressed is reduced within predetermined intervals of time.

Mineralogy of surface soil samples of some quebec soils with reference to k status

Abstract: Surface samples of five Quebec soils (St. Bernard, Ormstown, Howick, Dalhousie and Bearbrook) were selected to represent typical agricultural soils with a range of parent material. Soil minerals were fractionated by size into five separates and examined using X-ray diffraction (XRD) techniques and chemical analyses. In nearly all cases the non-clay separates (250–2.0 μm) contained feldspars, amphiboles and quartz as dominant minerals with only small amounts of layer silicates. Feldspars, amphiboles and quartz were also relatively abundant in the clay separates. The layer silicates in the clay separates consisted mainly of mica, chlorite and vermiculite. The soils had similar mineral suites, considered indicative of a low degree of weathering. Considering the mineral composition and the low degree of weathering, it is proposed that primary K-bearing minerals, including K-feldspars, are important sources of K in these soils. Key words: K release, particle size, soil mineralogy

Effect of soil clay mineralogy on the efficiency of ammonium sulfate in flooded rice

Abstract: The effect of soil clay mineralogy on the efficiency of (NH4)2SO4 in flooded rice was investigated in a greenhouse pot trial with four clayey soils of diverse clay mineralogies (x-ray amorphous, montmorillonite, vermiculite, beidellite). KCl (75 kg K ha−1) and triple superphosphate (25 kg P ha−1) were incorporated in the soil with and without (NH4)2SO4 (100 kg N ha−1) before transplanting 1-week-old IR-36 rice seedlings which were then grown to maturity under flooded conditions. Efficiency of (NH4)2SO4 was inferred from the response of agronomic characteristics such as tiller number, height, grain and straw yields to NH4 fertilization.

Method of increasing the volume yield of exfoliated vermiculite

Abstract: A method is disclosed for increasing the volume yield of expanded vermiculite obtained by exfoliation of vermiculite ore particles. The method comprises the sequential steps of applying vegetable oil to the vermiculite ore particles and thermally exfoliating the vermiculite ore particles.

Fine-grained granular material of expanded perlite or vermiculite and method for the production thereof

Abstract: A fine-grained granular material of expanded perlite or vermiculite suitable in particular as an additive for insulating coatings consists of granules the material of which is converted to cellular glass at least on the surface of the granules. For the production of the granular material the raw perlite or raw vermiculite is subjected to a pretreatment which consists of a hydrothermal conversion of at least the surface layer, by which the melting point of the material is lowered below its expansion temperature. This hydrothermal conversion of the surface layer can be effected in a known manner.

Measurement of Ionic Activity of Sodium and Potassium in Clay-Water Systems by Membrane Electrodes

Abstract: Clay and resin membrane electrodes were used to determine the Na+ and K+ activities in clay-water systems of pure kaolinite, bentonite, and vermiculite samples. The mobility ratio decreased slightly with increase in ionic activity by clay membrane electrode while with resin membrane one a reverse trend was noted. The bonding energy (ΔF) for Na+ of different clay minerals followed the order: vermiculite > bentonite > kaolinite. For any specific mineral with the two ions the order way found to be K+ > Na+. A combination of clay and resin membrane electrodes, within specific limits of concentrations, could be effectively employed in estimating the cationic activity in clay-water systems.

Structural Study in some Vermiculite Minerals using DTA and TGA Techniques

Abstract: Structural differences occurring in vermiculite minerals of different origin are brought out in this paper. Peaks obtained in DTA and TGA are attributed to the structural modifications occurring in the minerals due to heat-treatment. The thermal domains for existence of both phyllosilicate and intermediate phases are correlated to the charge density of the mineral. Exfoliation characteristic of the minerals vis-a-vis charge density is also discussed.

Pore structure of vermiculite that has been activated by two-stage acid etching

Abstract: Acid treatment of vermiculite from the Kovdor deposit in two stages offers a means for performing a controlled etching and obtaining a sorbent with a predominant content of uniform mesopores.

An Estimate of Migration of 137Cs in a Vermiculite Column by Measuring the Surface Dose Rate with TLD

Abstract: The surface dose rate of the vermiculite column was measured during about two years with TLD to predict the migration of 137Cs in the adsorbent layer. The vertical distribution of the surface dose rate was obtained from the data measured at intervals of five centimeter in vertical direction. From this dose rate distribution we estimated the length of the 137Cs adsorbed layer and calculated Kf value and distribution coefficient Kd of 137Cs using Inoue's method. And we calculated the surface dose rate of the vermiculite column considering the 137Cs adsorbed layer as a volume source of a uniform activity distribution. For this calculation, we simplified the shape of the vermiculite column to triple layer cylinder. The core of this cylinder is vermiculite which is surrounded with rubber and mild steel shells. Broder's equation is used to calculate a build-up factor for multi-layer materials. The result of this calculation shows good agreement with the measured values with TLD, thus we can estimate the migration of 137Cs in a vermiculite column by measuring the surface dose rate with TLD.

Smectite synthesis in volcanic ash soils ‐ a probable cause of zinc deficiency in wetland rice

Abstract: In an effort to ascertain the role of clay type in the widespread Zn deficieny on certain important wetland rice soils, 200 surface soil samples both from problem and non‐problem areas were investigated for clay mineralogy and available Zn content and correlated, as information on this aspect is scanty. Results showed prevalence of Zn deficiency on soils having x‐ray amorphous and smectitic clays of volcanic ash origin. Smectite synthesis from the x‐ray amorphous constituents particularly appeared responsible for the disorder presumably either through Zn incorporation in the crystal structure to form ‘sauconite’ or through its preferential sorption on the synthesized crystallites. Other mineral species ‐ chlorite, vermiculite, kaolinite, halloy‐site and hydrous mica ‐ did not appear to be related to Zn deficiency on these soils.