Vermiculite

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

Alteration of clay minerals and zeolites in hydrothermal brines

Abstract: Clay minerals and zeolites, candidate backfill minerals for nuclear waste repositories, were treated with saturated NaC1 brine and Mg-rich (Mg-Ca-Na-K) brine at 200~ and 300~ for 4 weeks under a confining pressure of 30 MPa. The AI concentrations released in NaC1 brine were lower than those in Mg-rich brine at both temperatures indicating that the Mg-rich brine is more acidic than the NaC1 brine under these hydrothermal conditions. The Si concentrations in both brines were low because of the relatively acidic conditions developed during the hydrothermal treatment. As determined by X-ray powder diffraction or by specific Cs and Sr sorption measurements, no alteration could be detected in clay minerals treated with NaCI brine at 200~ Among the zeolites tested, only phillipsite and erionite altered to analcime in NaCI brine at 200~ Zeolites and most of the clay minerals tested did not alter in the Mg-rich brine treated at 200~ Vermiculite altered to randomly interstratified vermiculite/K- vermiculite (mica-like) by selective K uptake from the Mg-rich brine. At 300~ the clay minerals did not greatly alter, whereas the zeolites altered to analcime and/or albite in the presence of the NaC1 brine. In the Mg-rich brine, Al-rich montmorillonite from Wyoming did not alter, whereas Al-poor montmorillonite from Texas altered to randomly interstratified montmorillonite/ illite at 300~ Vermiculite collapsed to form K-vermiculite (~ 10.2 A) by the selective uptake of K from the Mg-rich brine at 300~ Most of the zeoliles altered to smectiles in the Mg-rich brine at 300~ because of the acidic conditions generated by the hydrolysis of Mg. The selective Cs-sorption K~ decreased from 11,700 for untreated phillipsite to 240 and 15 for the hydrothermally produced analcime/albite mixtures from the phillipsite at 200 ~ and 300~ respectively, in NaCI brine. These results suggest that montmo- rillonites and mordenites are relatively more resistant than vermiculite or other zeolites at elevated temperatures and pressures in concentrated hydrothermal brines expected in a salt repository.

Apparatus for the expansion of mineral matter, especially perlite and vermiculite

Abstract: Perlite and vermiculite are blown by injecting the particles, entrained in a carrier gas, through a burner at the bottom of a fluidized bed furnace, into the latter with, within and codirectionally with the flame to ensure uniformity of the product.

Mineralogy Of B Horizons In Alpine Forest Soils Of Taiwan

Abstract: The nature of minerals in the B horizons of alpine forest soils in subtropical and tropical areas remains to be identified. The objective of this study was to investigate the distribution of Fe-oxides and hydroxy-interlayered vermiculite (HIV) in typical alpine forest soils of Taiwan. Five pedons at roughly 2000 m elevation of Taiwan were selected as example for this study. High gradient magnetic separation (HGMS), conventional X-ray diffraction (XRD), differential X-ray diffraction (DXRD), and transmission electron microscopy (TEM) were employed to characterize the clay minerals. The content of crystalline Fe-oxides increased sharply from E to B horizons. Only Al-substituted lepidocrocite and goethite were identified by differential X-ray diffraction (DXRD) analysis in magnetic clay fractions of the B (or placic) horizons; no substantial hematite peaks appeared in the XRD patterns of any pedons. These observations are quite different from those of Spodosols or Spodosol-like soils developed in the temperate and frigid zones of North America. Hydroxy-interlayered vermiculite (HIV) was characterized by collapse of the 1.42-nm peak in the XRD diagrams toward 1.0 nm when the K-saturated clay samples were heated to 350°C. In the surface horizons, only vermiculite could be identified in the coarse clay fractions. The distribution patterns of acid ammonium oxalate extractable Fe and Al in these pedons indicate that Al and Fe were leached from the A horizons and accumulated in the B horizons when forming Al-substituted lepidocrocite, goethite, and HIV. This is attributed to the combined effect of organic acids, Al, and Fe in the pedogenic environments. The present findings are of fundamental significance in understanding the formation of Spodosol-like soils in alpine forest soils in the subtropics and tropics.