Showing papers on "Vermiculite published in 2013"

On the mechanism of exfoliation of ‘Vermiculite’

Abstract: Six samples of 'Vermiculite' have been studied to investigate the mechanism of its well known but poorly understood property to exfoliate. The samples were analysed quantitatively by XRD to determine their precise mineralogical composition. Electron microprobe methods, including elemental mapping of native potassium and of caesium (introduced by cation exchange) were used to examine variation in the chemical composition of the particles. Most of the samples examined show heterogeneous mineralogical compositions which occur as distinct zones within the volume of individual particles, presenting a mosaic texture. Exfoliation is related to this mosaic distribution of the different mineral phases within the particles. Lateral phase boundaries between vermiculite and mica layers, or vermiculite and chlorite layers are postulated to prevent or impede the escape of gas from a particle, resulting in exfoliation when the pressure exceeds the interlayer bonding forces that hold the layers together. This mechanism provides a common explanation for the exfoliation of 'Vermiculite' by thermal methods or by treatment with H2O2. Paradoxically, one sample which consists of pure vermiculite, in the mineralogical sense of the term, demonstrates that pure vermiculite does not and should not exhibit the property of exfoliation. Our explanation of the mechanism of exfoliation explains the commonly observed particle size dependence of exfoliation and the tendency for obviously poly-phase 'Vermiculite' samples to show the largest coefficients of expansion.

Potassium dynamics in three alluvial soils differing in clay contents

Abstract: Despite the presence of a huge amount of potassium (K + ) in the soil, most of the soils are deficient in plant available K + . A large amount of the K + is fixed by clay minerals present in such soils and cannot be taken up by plants to achieve optimum plant growth. In such type of soils, large amount of K + fertilizers are required for optimum plant growth, as plants do not respond enough to a normally recommended K + fertilization. Vermiculite clay minerals can fix an enormous amount of applied K + , which becomes slowly available to the plants. The K + dynamics in such soils are valuable to recommend K + fertilizer requirements for sustainable nutrient management. We analyzed the K + dynamics of three alluvial soils, i.e Kleinlinden, Giessen and Trebur, collected from Germany and found that the soils with vermiculite and smectite clay minerals have more K + fixing ability than soils dominated by illite clay minerals. However, as the K + concentration decreased in the soil solution, smectite-dominant soils may easily release fixed K + due to lower particle-charge, whereas vermiculite and illite dominant soils may not release fixed K + easily. Moreover, ammonium exchangeable K + , non-exchangeable K + , total K + and K + -fixing capacity of these soils are directly proportional to the soil clay contents. While recommending K + fertilizers clay contents and the type of clay minerals is not considered and recommended K + fertilizers sometimes do not response plant growth enhancement. Therefore potassium fertilizer should be recommended by taking into consideration the type and amount of clay minerals present in the soil.

Lodo de esgoto e vermiculita na produção de mudas de eucalipto

Abstract: The success concerning forest plantations is not only dependent on the species used, but is also directly related to the kind of container, seeds quality and substrate used. Thus, this study aimed at evaluating the use of sewage sludge, together with vermiculite, in the composition of substrates used for producing Eucalyptus grandis seedlings from seeds. A completely randomized design, with six treatments and six replications of four plants, was used. The treatments consisted of the following sewage sludge and vermiculite proportions (v:v): 100:0 (T1), 80:20 (T2), 60:40 (T3), 40:60 (T4), 20:80 (T5) and a commercial substrate (T6). The collar diameter, height, ratio between shoot height and collar diameter, shoot dry matter, root dry matter, total dry matter, ratio between shoot and root dry matter, ratio between height and shoot dry matter and Dickson Quality Index were evaluated. At 90 days after germination, it was observed that the use of different proportions of sewage sludge and vermiculite influenced positively the growth of Eucalyptus seedlings, with better results for higher proportions of vermiculite. The best substrate was the one with 20% of sewage sludge and 80% of vermiculite.

Biotite-controlled linear compositional weathering trends in tonalitic to quartz dioritic saprock, Santa Margarita Ecological Reserve, southern California, USA

Abstract: Geochemical data derived from saprock produced by the weathering of K-feldspar-absent or K-feldspar-poor tonalite to quartz diorite yield linear compositional weathering trends pointed away from the p(K)-apex in p(A)–p(CN)–p(K) ternary diagrams. In contrast, published geochemical data derived from the classical granodioritic Toorongo weathering profile of south Australia yields a linear compositional weathering trend pointed away from the p(CN)-apex. The latter plagioclase-dominated weathering trend has been recognized since about 1984 and is due to the removal of CaO and Na2O from plagioclase. In contrast, to our knowledge, the biotite-dominated weathering trend derived from K-feldspar-absent to K-feldspar-poor tonalite to quartz diorite has not been documented or recognized previously, and is likely due to the removal of K2O from the interlayer position of biotite as it is transformed into vermiculite or mixed-layer biotite/vermiculite.

Mineralogical and geomicrobial examination of soil contamination by radioactive Cs due to 2011 Fukushima Daiichi Nuclear Power Plant accident

Abstract: Soil contamination by radioactive Cs from Fukushima Daiichi Nuclear Power Plant accident was investigated. Absorption and desorption experiments of Cs were conducted for several phyllosillicates (kaolinite, sericite, montmorillonite, vermiculite, chrysotile and biotite), zeolite and solid organic matter (dead and green leaves). The results confirmed the characteristic sorption and desorption of Cs by these materials. The 2:1 type phyllosilicate, especially, vermiculite and montmorillonite absorbed Cs well. Heated vermiculite for agricultural use and weathered montmorillonite also adsorbed Cs. Leaves also absorbed Cs considerably but easily desorbed it. In summary, the relative capacity and strength of different materials for sorption of Cs followed the order: zeolite (clinoptilolite) > 2:1 type clay mineral > 1:1 type clay mineral > dead and green leaves. Culture experiments using bacteria of both naturally living on dead leaves in Iitate village, Fukushima Pref. and bacterial strains of Bacillus subtillis, Rhodococus erythropolis, Streptomyces aomiensis and Actinomycetospora chlora were carried out. Non-radioactive 1% Cs solution (CsCl) was added to the culture media. Two types of strong or considerable bacterial uptakes of Cs were found in bacterial cells. One is that Cs was contained mainly as globules inside bacteria and the other is that Cs was absorbed in the whole bacterial cells. The globules consisted mainly of Cs and P. Based on all these results, future diffusion and re-circulation behavior of Cs in the surface environment was discussed.

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 ...

Approaches for cesium uptake by vermiculite

Abstract: BACKGROUND Expanded vermiculite is widely used in many fields, especially as an ameliorant in agriculture. Although it is known as a cation-exchanger, in a search for a new cesium adsorbent for environmental conservation, the ion-exchange behaviour of cesium on vermiculite in various grain sizes was investigated. The adsorption of cesium from artificial seawater was also investigated. RESULTS The effect of the vermiculite grain size was clearly identified. The preferred gain size for general use was found to be 500 µm. The amount of adsorption was low in these artificial seawater samples, however, almost similar ion-exchange behaviour was observed in both of the pure water and artificial seawater samples. CONCLUSION Adjustment of grain size according to the end use enables unlimited availability for application as an adsorbent of cesium. The results showed that vermiculite is a promising material for the recovery of cesium from contaminated seawater. © 2013 Society of Chemical Industry

On the mechanism of exfoliation of 'Vermiculite'

Abstract: AB ST R ACT : Six samples of ‘Vermiculite’ have been studied to investigate the mechanism of its well known but poorly understood property to exfoliate. The samples were analysed quantitatively by XRD to determine their precise mineralogical composition. Electron microprobe methods, including elemental mapping of native potassium and of caesium (introduced by cation exchange) were used to examine variation in the chemical composition of the particles. Most of the samples examined show heterogeneous mineralogical compositions which occur as distinct zones within the volume of individual particles, presenting a mosaic texture. Exfoliation is related to this mosaic distribution of the different mineral phases within the particles. Lateral phase boundaries between vermiculite and mica layers, or vermiculite and chlorite layers are postulated to prevent or impede the escape of gas from a particle, resulting in exfoliation when the pressure exceeds the interlayer bonding forces that hold the layers together. This mechanism provides a common explanation for the exfoliation of ‘Vermiculite’ by thermal methods or by treatment with H2O2. Paradoxically, one sample which consists of pure vermiculite, in the mineralogical sense of the term, demonstrates that pure vermiculite does not and should not exhibit the property of exfoliation. Our explanation of the mechanism of exfoliation explains the commonly observed particle size dependence of exfoliation and the tendency for obviously poly-phase ‘Vermiculite’ samples to show the largest coefficients of expansion.

Vermiculite’s strong buffer capacity renders it unsuitable for studies of acidity on soybean (Glycine max L.) nodulation and growth

Abstract: Background Vermiculite is the most common soil-free growing substrate used for plants in horticultural and scientific studies due to its high water holding capacity. However, some studies are not suitable to be conducted in it. The described experiments aimed to test the suitability of vermiculite to study the effect of acidity on nodulation and growth of soybean (Glycine max L.).

Evolution of dioctahedral vermiculite in geological environments – an experimental approach

Abstract: Dioctahedral vermiculite commonly occurs in soils and fresh sediments, but has not been reported in sedimentary rocks. Little is known of the evolution of this mineral during diagenesis. According to the available literature, dioctahedral vermiculite is likely to exhibit strong potential for selective sorption and fixation of K+ involving interlayer dehydration and collapse. he objective of the present study was to investigate the influence of K+ saturation and seawater treatments on the structure o dioctahedral vermiculite. Due to the fact that no dioctahedral vermiculite standard reference material was available, a natural sample of soil clay containing dioctahedral vermiculite was used in the study. The clay was saturated with K+ using different protocols simulating natural processes taking place in soils and marine environments. The solid products of the experiments were analyzed for potassium content using flame photometry. The effect of the treatments used on the structure of dioctahedral vermiculite was studied using X-ray diffraction (XRD). The percentages of the collapsed interlayers were estimated by modeling the XRD patterns based on a whole-pattern multi-specimen modeling technique. All the treatments involving K+ saturation caused K+ fixation and irreversible collapse (i.e. contraction to 10 A) of at least a portion of the hydrated (vermiculitic) interlayers. Air drying of the K+-saturated samples greatly enhanced the degree of the collapse. The results obtained gave no clear answer as to whether time had had a significant effect on the degree to which irreversible collapse occurred. Selective sorption of K+ from artificial seawater was observed. These results clearly indicate that collapse of dioctahedral vermiculite is likely to occur in soils during weathering and in sediments during early diagenesis. Both processes need to be taken into consideration in sedimentary basin studies.

Inorganic-organic Hybrids Originating from Organosilane Anchored Onto Leached Vermiculite

Abstract: The reactivity of clay minerals leached in grafting reactions was investigated. Precursor solids were prepared by treating the sodium vermiculites with nitric acid solutions at several concentrations. The lixiviation produced the restructured porous solids with surface area over a wide range, varying from 133 to 673 m2 g - 1. The sodium and lixiviated vermiculites reacted covalently with silylating agent, 3-aminopropyltrimethoxysilane, to attach this agent onto the inorganic surface, through the free available silanols. The products were characterized by CNH elemental analysis, infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance in the solid state for carbon and silicon. CHN data expressed by significant contents of anchored organic chains, up to 2.14 mmol g - 1, as the degree of leaching was increased. The success of this investigation is directly related to the leaching of the natural vermiculite, which is strongly influenced by the reactivity of the abundant original source.

Effects of Different Collecting time and Different Medium on Rooting of Pomegranate " Malas torsh cv." Cuttings

Abstract: As developing pomegranate cultivation in Iran, demand for suitable and commercial varieties is increasing. An experiment was conducted to study the influence of seven collecting times (Nov-Feb) with fifteen days interval and six different media (Perlite, cocopeat, vermiculite, sand and equal mixes) on rooting characteristics of pomegranate "Malas torsh cv." cuttings in 2010-2011. Uniform sized cuttings of pencil thickness and 30 cm in length long with four buds were separated from healthy pomegranate trees in certain times and after placing under wet cleaned sand and application of rooting hormones , planted in mentioned media on 3 Feb. Rooting hormone (Naphtalene Acetic acid 4000ppm) was applied on the cuttings for (5 seconds) under bottom heat and mist system. The results showed that most rooting percent and fresh root weight were obtained in sand+vermiculite and vermiculite, respectively. Also the most freshroot fresh weight and rooting percent was observed in 21 Dec and 4 Feb, respectively. Interaction between collecting time of cuttings and media showed significant effects (p <0.001) on rooting characteristics. The most effect on rooting percentage and root numbers was obtained on 5 Jan and 4 Feb in vermiculite and 19 Feb in vermiculite + sand respectively.

Experimental Investigation of Adsorption of Copper from Aqueous Solution using Vermiculite and Clinoptilolite

Abstract: Considering the point that the existence of heavy metals in the wastewater are so dangerous forthe environment and it would have many bad consequences for all the creatures including human beings, wemust try out the ways that make us capable of adsorbing these heavy metals. In order to accomplish this goal we should use a method called adsorbing. In this study the adsorption of copper ions in hydrated copper nitrate (Cu (NO3)2, 3H2O) aqueous solution on natural zeolite (Clinoptilolite) and vermiculite was studied in batch reactors. The effect of temperature (25, 50, 75 °C), solution pH (1.00-5.5) and concentration effect on the traditionally defined adsorption isotherm in the adsorbate range 100-325 mg/L for clinoptilolite and 100- 650 mg/L for vermiculite on the removal of copper was studied. The results showed that an increase in pH increases the adsorptivity of vermiculite. Pseudo second order model best described the reaction rate. Batch adsorption experiments conducted at room temperature (25±1 °C) showed that the adsorption pattern followed the Langmuir and Freundlich isotherm models. Optimum conditions for adsorption were determined at pH 5.5, and vermiculite and clinoptilolite at a dose of 3g. The concentration of metal ions was measured by Atomic Absorption Spectro eter (AAS). The results indicated that vermiculite and clinoptilolite are appropriate for adsorbing copper ions.