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Vermiculite
About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.
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TL;DR: In this paper, the authors measured the contribution of clay, silt, very fine sand (VFS) and fine sand fractions to K fixation in five Sierra Nevada granitic alluvium soils.
50 citations
04 Apr 2011-Journal of Environmental Science and Health Part A-toxic\/hazardous Substances & Environmental Engineering
TL;DR: A group of 262 sediment samples were collected from various lakes, rivers, reservoirs, and bayous of Louisiana and the dominant clay mineral was Hydrated Interlayer Vermiculite (HIV), which represented 51–83% of the total clay mineral.
Abstract: A group of 262 sediment samples were collected from various lakes, rivers, reservoirs, and bayous of Louisiana. All samples were analyzed for total mercury. Twenty nine of the samples with total mercury content ranging from 11 to 401 ppb (μg/kg) were analyzed for clay minerals and other sediment physical and chemical properties. Clay content in sediments varied from 3 to 72%. Clay minerals were determined by X-ray diffraction (XRD) technique. Identification of clay minerals was determined by MacDiff software and quantification of clay minerals was obtained by Peak Height Percentage (PHP) calculation. The dominant clay mineral was Hydrated Interlayer Vermiculite (HIV), which represented 51–83% of the total clay mineral. Significant linear correlations were observed between Hg and total clay content (r= 0.538**). However Smectite was the only individual clay type correlated (r= 0.465**) with mercury in sediment. Cation exchange capacity (r= 0.404*), organic matter (r= 0.577**), and sulfur (r= 0.676**) were ...
50 citations
TL;DR: The most weatherable primary minerals are plagioclase feldspar, biotite and fine-grained dioctahedral mica and their decomposition, which is mediated by organic acids, leads to the formation of proto-imogolite allophane, vermiculite, and smectite as mentioned in this paper.
Abstract: Many areas where concern has arisen over the recent acidification of their surface waters contain podzolic soils developed upon granitic materials. The mineral weathering processes in these soils are reviewed and the ways in which such processes could be altered by acid deposition are considered. The most weatherable primary minerals are plagioclase feldspar, biotite and fine-grained dioctahedral mica and their decomposition, which is mediated by organic acids, leads to the formation of proto-imogolite allophane, vermiculite and smectite. Other clay minerals occurring in podzols such as kaolinite and halloysite, as well as gibbsite, are probably inherited from previous weathering cycles, although a present-day pedogenic origin should not be ruled out entirely. The possibility is considered that the partial replacement of soil organic acids by mineral acids introduced through precipitation could bring about significant differences in mineral weathering, leading to more acid soils with more dissolved ionic aluminium in soil and stream waters. The weathering products involved in the mobilization of aluminium from podzols are likely to be proto-imogolite allophane and hydroxy Al-interlayered vermiculite or smectite. Another possibility is that sand and silt-sized plagioclase feldspars are more reactive than previously realized.
49 citations
TL;DR: The question of whether clay minerals can be biogenically transformed as a result of lichen activity at the lichen-rock interface remains unresolved as discussed by the authors, and several microscopical and analytical techniques, such as scanning electron microscopy-backscattered electron (SEM-BSE), energy dispersive spectroscopy (EDS), and high-resolution transmission electron microscope (HRTEM), have been applied in an attempt to address this issue.
Abstract: The question of whether clay minerals can be biogenically transformed as a result of lichen activity at the lichen-rock interface remains unresolved. We applied several microscopical and analytical techniques—scanning electron microscopy-back-scattered electron (SEM-BSE), energy dispersive spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM)—in an attempt to address this issue. Unaffected granitic biotite and bioweathered material from the granitic biotite and Parmelia conspersa lichen thalli interface were examined using HRTEM after ultrathin sectioning. The n-alkylammonium treatment of ultrathin sections was carried out in order to study the biogenous mineralogical transformation of the biotite. Microsamples proceeding from unaffected biotite zones demonstrated homogenous 10-A d(001)-value biotite phase. HRTEM images of lattice fringes of samples taken from the lichen-biotite contact zone reveal large areas of both unexpanded (10-A) and randomly and R = 3 distributed expanded (from 14- to 30-A) layers of phyllosilicates identified as interstratified biotite-vermiculite. Results of artificial biotite weathering (replacement of K by Ca ion) also revealed the biotite-vermiculite phase formation, indicating that K release in biotite is one of the mechanisms responsible for interstratified mineral phase formation. Two parallel processes, physical exfoliation of biotite and inter-layer ionic exchange of K and subsequent vermiculite formation, are the mechanisms for biotite bioweathering induced by lichens.
49 citations
TL;DR: Vermiculite was treated with 0.8 m solutions of hydrochloric and sulphuric acids for 2, 8, and 24 hours as mentioned in this paper. But the acid treatment strongly modified the vermiculite structure leading to a distinct increase of its catalytic activity in the selective catalytic reduction of nitric oxide (SCR NO) process.
49 citations