Selectivity of a number of vermiculites, montmorillonites and micas for K and Cs ions was determined by sorption of these ions from equilibrium solutions of diverse concentrations. The selectivity coefficients were related to the layer charge density and the area of the frayed edges in layer silicates. Montmorillonites had the smallest selectivity for the two ions, while biotite and illite had ...

-Chloritic veins in serpentinite and their weathering products were analyzed by X-ray powder diffraction (XRD) and X-ray fluorescence spectrometry (XRF). Chlorite formed during the Hercynianage orogenesis had apparently been partly transformed to high-charge vermiculite during subsequent metamorphism of the rocks. The idealized structural formulae for these minerals are (mlL9Fea+0.zFe2+o.4Mg9.2...

Natural vermiculite, used as layered catalyst support, was modified with different chemical methods, such acid treatment, introducing into Na + and organic modification. The vermiculite-based catalysts were characterized by SEM, BET XRD respect to their images, textures structures. SEM results presented big pieced of lamellate vermiculite which had complete structure piled tightly, the expansio...

A BSTRACT: A review is given of the application of ESR spectroscopy to the study of hydrated transition metal ions and nitroxide spin probes in the interlamellar region of smectites and vermiculites. These investigations have not only provided information regarding the structure and mobility of the intracrystalline water-cation layers but have also demonstrated the reactivity and catalytic prop...

South African Palabora vermiculite was modified by ion exchange with ammonium and selected alkali metal and alkaline earth metal ions. In the exchanged vermiculite with ammonium ions, it was found that ammonia and water were the blowing agents and they were simultaneously released during thermal degradation. In the increasing ionic potential series: Na, Ba, Ca and Mg, it was found that the onse...

-The effects of Na-citrate-dithionite (NaCD), ammonium oxalate in the dark (NH4Ox-D), and photolytic reaction under ultraviolet radiation (NH4Ox-P) on the mineralogy of <2-/~m fractions of selected soils from Virginia were investigated. The NH4Ox-D treatment removed the smallest amounts of Al (<0.22%) and Fe (<0.50%) from all soils, indicating low levels of noncrystalline material in these mate...