Vermiculite

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

Montmorillonite, vermiculite and saponite based porous clay heterostructures modified with transition metals as catalysts for the DeNOx process

Abstract: Porous clay heterostructures (PCHs) were synthesized from natural montmorillonite and vermiculite as well as synthetic saponite using the surfactant directed method. The direct synthesis of PCHs from saponite and montmorillonite was possible, while the pre-treatment of parent vermiculite with acids was necessary prior to the intercalation step. The PCH samples were characterized with respect to their composition (EPMA), structure (XRD, UV–vis-DRS), texture (BET), surface acidity (FT-IR) and chemical nature of the deposited transition metal species (UV–vis-DRS). Porous clay heterostructures as well as their derivatives modified by deposition of transition metal (Cu, Fe) oxides were tested as catalysts for the DeNOx process. The transition metal containing PCH samples were found to be active, selective and stable catalysts of this process. Their catalytic performance depended on the kind of the parent clay used for the PCH synthesis as well as deposited transition metals.

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...

Supergene Vermiculitization of A Magnesian Chlorite: Iron and Magnesium Removal Processes

Abstract: An X-ray powder diffraction study of a verrniculitized chlorite in an amphibole schist near Limoges, France, shows the following weathering sequence: chlorite ~ ordered interstratified chlorite/ vermiculite ~ vermiculite. M6ssbauer spectroscopy indicates that vermiculitization proceeded by the release of ferrous iron from the 2:1 mica layer of the chlorite. The ferric iron content of the vermiculite product is almost the same as that of the initial chlorite. Infrared spectroscopy and chemical microprobe analyses show that Mg was preferentially extracted from the hydroxide sheet of the chlorite, whereas the Si and A1 contents progressively increased to the point of the formation of a pure dioetahedral alnminous vermiculite. The Si, A1, and Mg removal processes support currently accepted vermiculitization mech- anisms, but the behavior of Fe is slightly different. In this weathering sequence, vermiculitization does not appear to have taken place by the oxidation of Fe 2+, but rather, by the simultaneous leaching of Fe 2§ and Mg.