Vermiculite

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

Clay Mineralogy in Arctic Tundra Gelisols, Northern Alaska

Abstract: Little is understood about chemical weathering processes in Alaskan arctic soils, where moisture is generally not limited but acidity varies and the average soil temperature is close to or below freezing. Weathering reactions in soil convert primary minerals into secondary clay minerals. Silty loam textured soils from three sites in moist acidic tundra (MAT) and three sites in moist nonacidic tundra (MNT) in the northern Arctic Foothills, Alaska, were characterized with emphasis on the origin of the clay minerals. The MNT soils had a discontinuous and thinner organic layer, which leads to a deeper summer thaw and greater cryoturbation than the MAT soils. The MNT had higher cation exchange capacity and base saturation than MAT. These buffer against acidification and account for the pH differences of MAT and MNT. Other chemical characteristics including C and N content as well as Fe and Al were similar (by horizon) across the MAT/MNT boundary. X-ray diffraction of coarse (0.0002-0.002 mm) and fine clay (<0.0002 mm) fractions indicate that illite, vermiculite, and kaolinite are the predominant clay minerals. Presumably, kaolinite is detrital and vermiculite is weathered from illite. The proportion of vermiculite to illite is higher in MAT and the illite to vermiculite proportion is higher in MNT. This shows that soil acidity does affect weathering processes despite the low soil temperature.

Availability of interlayer ammonium as related to root vicinity and mineral type.

Abstract: We studied the release of nonexchangeable NH4+ from soils when cropped with ryegrass. The plants were grown in special soil containers in which part of the soil was not in direct contact with the roots. Nonex-changeable NH4+ was released only in the immediate vicinity of the roots where, it is sugge

Evaluation of Vermiculite in Reducing Ash Deposition during the Combustion of High-Calcium and High-Sodium Zhundong Coal in a Drop-Tube Furnace

Abstract: The additive injection technology has been effective in alleviating slagging and fouling during coal combustion. In this study, experiments were conducted in a drop-tube furnace to understand the influence of vermiculite injection on ash deposition during the combustion of Zhundong coal. The interaction between coal ash and vermiculite was investigated by inductively coupled plasma optical emission spectrometry (ICP–OES), X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive spectrometry (SEM–EDS). Results show that deposits formed at 1100 °C with vermiculite additive are more friable and polyporous than those without vermiculite additive, and these deposits can be easily removed. The mechanisms behind this phenomenon can be explained as follows: (1) The agglomeration of ash particles is inhibited by the partition of low-viscosity slices formed through vermiculite swelling after heat treatment. (2) Intermetallic reactions occur on the surface of vermiculite particles, resulting in the fo...

Cs–sorption in weathered biotite from Fukushima granitic soil

Abstract: The sorption characteristics of cesium (Cs) ions into weathered biotite with biotite–vermiculite interstratification collected from weathered granodiorite in Fukushima Prefecture, Japan has been investigated. Both single crystals and crushed powder forms of the weathered biotite were experimentally reacted with 20–2000 ppm CsCl aqueous solutions, and analyzed by powder X–ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) to examine the distribution of Cs inside the crystals. From the XRD pattern, the proportion of vermiculite unit layers in the weathered biotite was estimated at ~ 12%, with a tendency for segregation, and the whole XRD pattern was explained by the coexistence of biotite and vermiculite packets as well as the interstratified regions. Powder XRD of Cs–sorbed specimens showed that the 14.9 Å peak of the vermiculite packets was weakened at a low Cs concentration in the solution. Single crystals of the weathered biotite with a polished edge–surface were immersed in the CsCl solutions and examined using SEM and high–angular annular dark field (HAADF) imaging in STEM. Cs was not only incorporated in the vicinity of the exposed surface but also penetrated deeply inside the crystals. These analyses and observations revealed the Cs–sorption process in weathered biotite. At first, Cs preferentially replaced specific vermiculite interlayers in the vermiculite packets. With a higher Cs concentration in the solution, the Cs–substituted vermiculite interlayers increased in the vermiculite packets, and vermiculite layers interstratified in biotite also incorporated Cs.