Vermiculite

About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.

Sorption of Cesium by Soils and Its Displacement by Salt Solutions

Abstract: Cesium was sorbed by montmorillonite, illite, and kaolinite in quantities corresponding to exchange saturation and was displaced readily on leaching with 1N KCl or CaCl/sub 2/. Vermiculite and heated (600 deg C, 12 hr) K- montmorillonite bound Cs tightly against displacement by CaCl/sub 2/ and AlCl/sub 3/, but not by KCl or NH/sub 4/Cl. Prolonged leaching with 1N KCl removed 97.5% of the Cs sorbed by heated Kmontmorillonite, while lN CaCl/sub 2/ eventually displaced 88%. Potassium and Rb sorbed on vermiculite were displaced more rapidly by Ca or Mg than by monovalent ions, but this was not the case with hented K-montmorillonite. The exchange-displacement behavior of Cs on vermiculite and heated K-montmorillonite suggests that the ion is unique in that its sorption in interlayer spaces leads to interplanar distances that admit K and NH/sub 4/ ions but greatly restrict the entry of Ca. Cesium, then, is not expected to follow the fixation-release rules that have been developed for K and NH/sub 4/. Heated montmorillonite samples leached with mixtures of CsCl and other salts sorbed more Cs when the complementary ion was Ca or Al than when it was K or NH/sub 4/. Differences were especially pronounced at low equivalent fractionsmore » of Cs in the leaching solution, showing a larger preference by exchange sites for Cs over divalent than over monovalent ions. Apparent specific sorption of Cs against exchange with CaCl/sub 2/ occurred at quite large Cs saturations. (auth)« less

Soil factors affecting the availability of potassium to plants for Western Australian soils: a glasshouse study

Abstract: A glasshouse experiment was conducted with 41 surface and 8 subsurface soils to measure their potassium (K) supply capacities and K depletion of soils by ryegrass growth for 260 days and harvesting at ~40-day intervals. Dry matter yield ranged from 0.22 g to 25.4 g/kg soil, cumulative K uptake ranged from 0.006 to 1.49 cmol/kg soil, and values of K concentration (%) in the first cut herbage ranged from 0.40% to 5.97%. Some of the light-textured soils were so impoverished in K that symptoms of K deficiency appeared during the first growth period. Water-soluble K + exchangeable K accounted for 43–100% of cumulative K uptake by the ryegrass. Multiple regression analysis indicated that 68% of the variation in dry matter yield and 90% of the variation in K uptake may be predicted by the exchangeable K content of these soils. The 6 harvests of ryegrass extracted only 0.21–12.07% of total K from these soils, which was not sufficient to cause discernible mineralogical changes in most soils. For some soils vermiculite was formed at the expense of illite/mica by K release to plants. For soils containing vermiculite but no other K-bearing clay minerals, vermiculite peaks broadened on K depletion by plants. Major proportions of total K in these soils are present in silicate minerals, yet only minor amounts are released to plants by very slow weathering processes. For soils that do not contain any K bearing clay minerals, very minor amounts of feldspar may have dissolved to release K.

Mineralogy, chemistry, and formation of oxidized biotite in the weathering profile of granitic rocks

Abstract: Biotite was oxidized in deep saprolitic weathering profiles developed on granitic rocks in a humid temperate climate in the Youngju-Andong area of South Korea. The mineralogy and chemistry of these oxidized biotites were characterized by chemical analysis, electron microscopy, X-ray diffraction, thermal analysis, and radiogenic Ar analysis. The results showed that a decrease in the b o-dimension, loss of radiogenic Ar, and formation of vermiculite are fairly well correlated with the degree of oxidation of ferrous iron. The chemical composition of oxidized biotite was modified by a non-stoichiometric removal of interlayer and octahedral cations to compensate for the charge imbalance induced by oxidation of Fe. The pervasive loss of cations and radiogenic Ar suggests their diffusion through oxidizing biotite in a non-expanded state. Iron oxidation and cation loss caused a decrease in the b o-dimension with the formation of discontinuities that acted as conduits for the weathering solutions, resulting in partial vermiculitization (<10%). The Fe oxidation was nearly completed in the lower part of the profile, concomitant with mineralogical and chemical modification to oxidized biotite that persists throughout the profile without further notable modification. Cation release from biotite is governed in early stage by the formation of oxidized biotite, and later by its decomposition.

Saponite and vermiculite in amygdales of the Granby basaltic tuff, Connecticut Valley

Abstract: Clay of apparent hydrothermal origin that fills amygdales in the Granby Basaltic Tuff (Lower Jurassic) of the Connecticut Valley was analyzed and found to consist of two exceptionally well-crystallized Fe-rich, trioctahedral 2:1 layer expandable phyllosilicates. Based on chemical and XRD analyses, the minerals were tentatively identified as saponite and vermiculite. The saponite exists predominately in the two-water hydration state, but also displays one- and three-water layer hydration states, which suggests heterogeneous layer charge distribution--a phenomenon not uncommon in smectites. The identity of the second clay remains equivocal, but XRD analyses, especially with regard to the swelling properties of the clay, indicate that it is a vermiculite. The well-crystallized nature of the Granby clay and the large size of the clay flakes (up to 1 mm) allowed us to use SEM/EDS X-ray imaging and spot analysis techniques in an attempt to detect chemical differences between the saponite and vermiculite. Results showed that the chemistry of individual crystals, within and among amygdales, was essentially uniform. This suggests that the saponite and vermiculite are chemically similar and that variations in their swelling properties result from other factors, such as crystal size, layer charge density, or charge localization within the unit layers. Crystal size differences in the Granby clay were observed with both the petrographic and scanning electron microscope. Changes in layer charge density or charge localization within unit layers could have been affected by the oxidation of Fe 2+ to Fe 3+, a transformation inferred from the green-to-brown color changes observed in the larger amygdales. The Granby clay is of special importance, because it is one of the few examples of a naturally occurring mixture of two well-crystallized, Fe-rich trioctahedral 2:1 layer expandable phyllosilicates with crystallochemieal and swelling properties that appear to bridge the op- erational definitions for the smectite and vermiculite groups.