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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 article, the copper removal efficiency by vermiculite has been investigated through laboratory experiments and the removal phenomenon appears to be consistent with an ion exchange (exchange adsorption) process.
Abstract: Copper(II) removal efficiency by vermiculite has been investigated through laboratory experiments. The removal phenomenon appears to be consistent with an ion-exchange (exchange adsorption) process. The batch sorption equilibria follows Freundlich adsorption isotherm. The uptake of copper(II) is a function of the pH of the solution and increases with increasing pH. Increasing ionic strength and the presence of soluble complexing agents such as ethylene diamine tetraacetic acid (EDTA) decrease the sorption of copper(II). The presence of other divalent cations like calcium impede dhte uptake of copper(II)
46 citations
TL;DR: The mechanism study revealed that the adsorption process of lead and cadmium ions by β-CD-loaded minerals was combined by diffusional movement with a chemical exchange of ionizable protons or cations, as well as by chemical bonding among heavy metal ions and functional groups (-OH, -COOH and CO).
46 citations
TL;DR: In this paper, the vermiculite was impregnated by glycerol containing 1, 2 and 4mol% of H 2 SO 4 at EV/Gly ratios, i.e. 1/1, 1/2 and 1/3, and heated to 380, 580 and 750°C.
46 citations
TL;DR: In this paper, it is proposed that vermiculite derives from a series of reactions whose relative rates often result in an abundance of vermiculate, and that these relative reaction rates are slow for mica dissolution, rapid for K removal, and slow for vermicule dissolution.
Abstract: Stability determinations were made by solubility methods on two trioctahedral mica-derived vermiculites. The phlogopite-derived vermiculite was found to be unstable under acid solution conditions, where stabilities of montmorillonite, kaolinite and gibbsite had previously been determined. An attempt was next made to locate a possible montmorillonite-vermiculite-amorphous silica triple point. This triple point involved conditions of alkaline pH, high pH4SiO4 and high Mg2+. These are conditions where phlogopite and biotite-derived vermiculites are most likely to control equilibria if they are stable minerals. The montmorillonite-vermiculite-amorphous silica samples went to the montmorillonite-magnesite-amorphous silica triple point, leaving no stability area whatsoever for the vermiculites. These large particle-size, trioctahedral, mica-derived vermiculites appear to be unstable under all conditions of room T and P. Arguments are presented indicating that micas are unstable in almost all weathering environments. A hypothesis is proposed that mica-derived vermiculites result from the unique way in which unstable micas degrade in these environments. It is proposed that vermiculite derives from a series of reactions whose relative rates often result in an abundance of vermiculite. These relative reaction rates are slow for mica dissolution, rapid for K removal and other reactions pursuant to vermiculite formation, and slow for vermiculite dissolution. In chemical terms, mica-derived vermiculites may be considered fast-forming unstable intermediates.
46 citations
TL;DR: In this paper, Nommik and Vantras studied the effect of anhydrous ammonia in soil clays and found that ammonium-containing clays can retain significant amounts of ammonium in excess of the cation ex- clay surface.
Abstract: of the waters of hydration is much greater than that of the bulk water (Mortland, 1968) due to polarization of Anhydrous ammonia is a widely used N fertilizer and its interac- NH 4 ,N H3, and total N increased by 12 to 23% on the Mg-exchanged compared with the Ca-exchanged soil clays. Of the two soil clays, the offixationdependsmainlyonthemineralogyofthesoils smectitic sample (Fayette) sorbed more of both N species than the with vermiculite being the most likely mineral phase to illitic sample (Blount). Samples with OM removed adsorbed signifi- fix NH 4 (Nommik and Vantras, 1982). Additional mecha- cantly more ammonia than untreated samples. The mechanism sug- nisms of NH3 retention include fixation by soil organic gested for ammonia sorption by soil clays is a combination of proton- compounds (Step 6), which for mineral soils does not ation on water associated with metal cations, coordination to the exceed 5% of applied N (Nommik and Vantras, 1982); exchangeable cations and dissolution in pore water. Soil clays can hydrogen bonding to oxide and hydroxyl ions on the retain significant amounts of ammonium in excess of the cation ex- clay surface (James and Harward, 1964); and formation change capacity (CEC) and out of competition for exchange sites. of ammine complexes with the exchangeable cations Dissolved NH3 constituted the majority of N adsorbed by the sample (Step 7) (Russell, 1965). It is clear that, even without at high RH, which is typical of field conditions. invoking the biological transformations of N, the inter- action web of N resulting from injection of anhydrous ammonia in soils is complex.
46 citations