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Vermiculite

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


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TL;DR: In this paper, X-ray diffraction and high-resolution transmission electron microscopy showed that cesium ions in a vermiculite clay formed a segregated monoionic layer in the interlayer spaces.
Abstract: X-ray diffraction and high-resolution transmission electron microscopy showed that cesium ions (Cs+’s) in a vermiculite clay formed a segregated monoionic layer in the interlayer spaces. Each ion w...

121 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured intra-erystalline swelling of Na-montmorillonite and Li-vermiculite using diffraction techniques and showed that the size of the interlayer separation is independent of sheet separation and electrolyte concentration.
Abstract: Various workers have studied the mechanism of swelling of Na-montmorillonite and have demonstrated that its ability to swell is due to water penetrating between the individual silicate sheets. In the present study intraerystalline swelling was followed by diffraction techniques which enabled the movement of the silicate sheets with respect to one another to be measured as a function of electrolyte concentration, with or without an externally applied load. The observations have been made on oriented flakes of Na-montmorillonite and single crystals of Li-vermiculite. Qualitatively the minerals behave similarly when swollen in salt solutions. They both show an initial stage of crystalline swelling, after which there is an explosive increase to the gel state, and then the distance apart of the silicate sheets increases linearly with C-½, where C is electrolyte concentration. Quantitatively, however, their swelling is very different, particularly after the “explosion”, where vermiculite generally gives higher spaeings than montmorillonite. There are two other important differences in the swelling of montmorillonite and vermiculite. Firstly, while the swelling of vermiculite appears to be reversible both with respect to electrolyte concentration and applied pressure, the swelling of montmorillonite shows a marked hysteresis. Secondly, in montmorillonite, swelling depends very strongly on pH or chemical treatment. There is little doubt that the development of diffuse “double layers” gives rise to repulsive forces, which cause the silicate sheets to move apart. Van der Waals’ forces have been regarded as providing attraction, but it is found that, at the observed interlayer separations, the magnitude of these attractive forces is inadequate to balance repulsion, both in montmorillonite and vermiculite. The present results demonstrate that in vermiculite swelling proceeds until the interlayer separation causes the repulsion between sheets to drop to a value of ~ 2.5 × 104 dyn/cm2. This attractive force, which limits swelling, appears to be independent of sheet separation and electrolyte concentration. In montmorillonite swelling is opposed by edge-to-face bonds between sheets, whose number and strength can be controlled by chemical treatment. These bonds act to resist any displacement of the sheets, either swelling or contraction. This mechanism is compatible with the observed swelling behavior of montmorillonite, and explains the differences between the swelling of this mineral and that of vermiculite where, because the sheets are considerably larger, the force arising from edge-to-face bonds is small or absent.

115 citations

Journal ArticleDOI
TL;DR: The influence of acid concentration and leaching time on the porous properties of silica was studied in this article, where high surface area was obtained by selectively leaching vermiculite.

114 citations

Journal ArticleDOI
TL;DR: The geochemical partitioning of a toxic metal contaminant during its migration through a shallow sand aquifer is discussed and the residual adsorbed /sup 90/Sr is strongly correlated with extractable Fe, Al, and Mn, suggesting specific adsorption by these metal oxides.
Abstract: The geochemical partitioning of a toxic metal contaminant, /sup 90/Sr, during its migration through a shallow sand aquifer is discussed. Adsorption of /sup 90/Sr from the contaminated groundwaters (pH approx. 6, I approx.0.001) causes it to have a migration velocity of only 3% of that of transporting ground water. Five microscopically identified adsorbents were isolated in the aquifer sediments and showed the following affinity sequence for /sup 90/Sr: vermiculite > feldspar > biotite > muscovite > quartz. While 4a80% of the adsorbed /sup 90/Sr is exchangeable with 0.1 M SrCl/sub 2/, the residual adsorbed /sup 90/Sr is strongly correlated with extractable Fe, Al, and Mn, suggesting specific adsorption by these metal oxides. An equilibrium adsorption model was used to determine the partitioning of /sup 90/Sr between adsorbents and between solid and solution phases. Over 90% of all /sup 90/SR in the aquifer is adsorbed. Approximately 90% of all adsorbed /sup 90/SR is equally divided between vermiculite and feldspar minerals.

114 citations

Journal ArticleDOI
TL;DR: In this article, expanded vermiculite and polypropylene fibers with low thermal conductivity were added to lightweight gypsum composites to improve the properties of the composites.

114 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202395
2022223
202163
202068
2019104
2018101