Vermiculite

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

Radiocesium interception potential (RIP) of smectite and kaolin reference minerals containing illite (micaceous mineral) as impurity

Abstract: Cesium-137 (137Cs) is strongly adsorbed on clay minerals, especially on illite. The adsorption of Cs+ on reference clay minerals, however, has not been fully investigated in relation to the presence of illite. The objective of this study was to clarify the effect of impurities (i.e., illite and vermiculite), present in reference smectite group minerals and kaolin minerals, on the retention of Cs+. The clay mineralogy of the reference minerals was characterized by X-ray diffraction (XRD). The radiocesium interception potential (RIP) was measured as an index of the Cs+ retention ability of clays. The content of illite in clay was represented by the total potassium (K) content given that illite is a major source of K in the clay fraction. The content of vermiculite in clay was represented by the Cs fixation capacity induced by Cs saturation followed by heating of samples at 110°C. Metabentonite and beidellite gave extremely high RIP values compared with other smectite group minerals, although a peak ...

Palladium‐nanoparticle intercalated vermiculite for selective hydrogenation of α,β‐unsaturated aldehydes

Abstract: Palladium nanoparticles were generated in the interlamellar region of swelling 2:1 type vermiculite clay using an adsorption excess isotherm. An adsorption excess isotherm was constructed for vermiculite after exchanging the exchangeable Na+ ions in the interlamellar region using a binary liquid mixture (ethanol:toluene). Based on adsorption excess isotherm, 1% w/w palladium was intercalated into the interlamellar space of vermiculite. The Pd-intercalated vermiculite was characterized by X-ray diffraction, transmission electron microscopy and atomic absorption spectroscopy. The 1% w/w Pd-intercalated vermiculite was tested for its catalytic activity towards selective hydrogenation reactions involving some α,β-unsaturated carbonyl compounds using a pulse reactor and its catalytic activity was compared with commercial 1% Pd/C. The intercalated catalyst was found to be very selective towards the desired product of unsaturated alcohols. Copyright © 2007 Society of Chemical Industry

Potential bioavailability of mercury in humus-coated clay minerals

Abstract: It is well-known that both clay and organic matter in soils play a key role in mercury biogeochemistry, while their combined effect is less studied. In this study, kaolinite, vermiculite, and montmorillonite were coated or not with humus, and spiked with inorganic mercury (IHg) or methylmercury (MeHg). The potential bioavailability of mercury to plants or deposit-feeders was assessed by CaCl2 or bovine serum albumin (BSA) extraction. For uncoated clay, IHg or MeHg extraction was generally lower in montmorillonite, due to its greater number of functional groups. Humus coating increased partitioning of IHg (0.5%-13.7%) and MeHg (0.8%-52.9%) in clay, because clay-sorbed humus provided more strong binding sites for mercury. Furthermore, humus coating led to a decrease in IHg (3.0%-59.8% for CaCl2 and 2.1%-5.0% for BSA) and MeHg (8.9%-74.6% for CaCl2 and 0.5%-8.2% for BSA) extraction, due to strong binding between mercury and clay-sorbed humus. Among various humus-coated clay particles, mercury extraction by CaCl2 (mainly through cation exchange) was lowest in humus-coated vermiculite, explained by the strong binding between humus and vermiculite. The inhibitory effect of humus on mercury bioavailability was also evidenced by the negative relationship between mercury extraction by CaCl2 and mercury in the organo-complexed fraction. In contrast, extraction of mercury by BSA (principally through complexation) was lowest in humus-coated montmorillonite. This was because BSA itself could be extensively sorbed onto montmorillonite. Results suggested that humus-coated clay could substantially decrease the potential bioavailability of mercury in soils, which should be considered when assessing risk in mercury-contaminated soils.