Showing papers on "Vermiculite published in 2010"
TL;DR: In this article, a series of chitosan-g-poly (acrylic acid)/vermiculite hydrogel composites were synthesized and used as adsorbents for the removal of methylene blue (MB) from aqueous solution, and the results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant.
Abstract: A series of chitosan-g-poly (acrylic acid)/vermiculite hydrogel composites were synthesized and used as adsorbents for the investigation of the effect of process parameters such as vermiculite content, pH of dye solution, contact time, initial concentration of dye solution, temperature, ionic strength and concentration of surfactant sodium dodecyl sulfate on the removal of Methylene Blue (MB) from aqueous solution. The results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant. The adsorption kinetics of MB onto the hydrogel composite followed pseudo second-order kinetics and the adsorption equilibrium data obeyed Langmuir isotherm. By introducing 10 wt.% vermiculite into chitosan-g-poly (acrylic acid) polymeric network, the obtaining hydrogel composite showed the highest adsorption capacity for MB, and then could be regarded as a potential adsorbent for cationic dye removal in a wastewater treatment process.
234 citations
TL;DR: In this paper, a novel photo-Fenton catalyst was prepared by iron pillared vermiculite (Fe-VT), which was characterized by laser particle size analyzer, XRD, X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and X-Ray photoelectron spectroscopy (XPS) methods.
99 citations
TL;DR: In this article, a parametric study investigating the impacts of loading amount of active phase, growth temperature, H2 reduction, space velocity, and apparent gas velocity on the intercalated growth of vertically aligned carbon nanotube (CNT) arrays among lamellar catalyst was performed.
86 citations
TL;DR: In this paper, the removal of nickel ions from aqueous solutions and activated sludge by employing ultrafiltration (UF) membranes together with natural aluminosilicate minerals (bentonite, zeolite and vermiculite).
84 citations
TL;DR: Palabora as discussed by the authors represents an interstratified vermiculite-biotite containing less than 50% vermiculate, and was prepared by immersion in saturated brine at ambient conditions.
62 citations
TL;DR: Vermiculite and phlogopite were reacted with nitric acid under controlled conditions as discussed by the authors, which increased the specific surface area and porosity and led to partial leaching of iron, aluminium and magnesium from the octahedral sheets.
47 citations
TL;DR: In this paper, X-ray diffraction of coarse (0.0002-0.002 mm) and fine clay fractions indicate that illite, vermiculite, and kaolinite are the predominant clay minerals.
Abstract: Little is understood about chemical weathering processes in Alaskan arctic soils, where moisture is generally not limited but acidity varies and the average soil temperature is close to or below freezing. Weathering reactions in soil convert primary minerals into secondary clay minerals. Silty loam textured soils from three sites in moist acidic tundra (MAT) and three sites in moist nonacidic tundra (MNT) in the northern Arctic Foothills, Alaska, were characterized with emphasis on the origin of the clay minerals. The MNT soils had a discontinuous and thinner organic layer, which leads to a deeper summer thaw and greater cryoturbation than the MAT soils. The MNT had higher cation exchange capacity and base saturation than MAT. These buffer against acidification and account for the pH differences of MAT and MNT. Other chemical characteristics including C and N content as well as Fe and Al were similar (by horizon) across the MAT/MNT boundary. X-ray diffraction of coarse (0.0002-0.002 mm) and fine clay (<0.0002 mm) fractions indicate that illite, vermiculite, and kaolinite are the predominant clay minerals. Presumably, kaolinite is detrital and vermiculite is weathered from illite. The proportion of vermiculite to illite is higher in MAT and the illite to vermiculite proportion is higher in MNT. This shows that soil acidity does affect weathering processes despite the low soil temperature.
39 citations
TL;DR: In this article, a modified vermiculite from Palabora (South Africa) was modified by thermal shock (700°C), chemical exfoliation (80°C in the presence of H 2 O 2 ) and ultrasonic treatments to improve the adsorption of boron.
39 citations
TL;DR: The finding of an association between CFE and cardiovascular mortality suggests persons exposed to Libby amphibole should be monitored for this outcome, and a clear exposure-response relationship between C FE and mortality from asbestos-related causes is demonstrated.
Abstract: Objective:To examine the relationship between cumulative fiber exposure (CFE) and mortality in a retrospective cohort study of vermiculite workers exposed to Libby amphibole (n = 1862).Methods:Extended Cox regression was used to estimate the hazards associated with CFE as a time-dependent covariate
37 citations
TL;DR: In this paper, natural clinoptilolite and vermiculite as well as their Na-forms are used for simultaneous removal of Fe (1.5 ppm) and Mn (0.1 ppm) from underground water samples.
Abstract: In the present study natural clinoptilolite and vermiculite as well as their Na-forms are used for simultaneous removal of Fe (1.5 ppm) and Mn (0.5 ppm) from underground water samples. Vermiculite exhibited higher removal levels than clinoptilolite for both Fe and Mn. In general, Fe removal is higher than Mn for vermiculite and the opposite holds for clinoptilolite. In particular, Fe and Mn removal levels are between 88–94% and 65–100% for vermiculite and 22–90% and 61–100% for clinoptilolite, respectively. Pretreatment as well as the use of smaller particle size increased the removal of both metals. The experimental results showed that the maximum permissible concentrations according to the legislation can be achieved.
32 citations
TL;DR: Respiratory symptoms were associated with other vermiculite exposures as well, and the number and frequency of these activities showed a positive trend with usually having a cough, while there was no association between any of the activities and abnormal spirometry.
Abstract: BackgroundLibby, Montana, was home to the largest vermiculite ore mine in the United States. The processing, use, and transport of the ore, which was contaminated with amphibole asbestos, led to ge...
TL;DR: In this paper, the vermiculite in the Southern Eastern Desert of Egypt at the contact of the metapelite and serpentinite rocks with the pegmatites and gneisses of the Hafafit uplift is the only known deposit in the Nubian Shield (ANS) rocks of the Eastern Desert (ED).
TL;DR: In this paper, soil clay samples from surface and subsurface horizons of 18 Thai upland Oxisols and Ultisols under a tropical monsoonal environment were characterized for chemical composition, mineralogy and K release to 0.3 M sodium tetraphenylboron (NaTPB) solution for periods up to 168h.
TL;DR: In this article, the average formula for hydroxy-interlayered vermiculite has been evaluated through depth distribution trends, thermodynamics-solubility, and alluvial chronosequences to develop a more thorough understanding of mineral transformations and pedogenesis in these landscapes.
TL;DR: In this paper, the adsorption of Cu(II) and Cr(III) ions by pure clay mineral, vermiculite, was examined in aqueous solution with respect to the adsorbent dose, initial metal ion concentration, pH, and contact time.
Abstract: The adsorption of Cu(II) and Cr(III) ions by pure clay mineral, vermiculite, was examined in aqueous solution with respect to the adsorbent dose, initial metal ion concentration, pH, and contact time. The studies showed that vermiculite can be used as an adsorbent material for the moderate removal of Cr(III) and Cu(II) from aqueous solutions. Lagergren first-order, pseudo-second-order, and intraparticle diffusion models were used to describe the kinetic data. The kinetics of adsorption indicates that the process fitted well the intraparticle diffusion model.
TL;DR: In this article, Fe2+-modified vermiculite was used as a new adsorbent for Cr(VI) removal, which has a higher adsorption capacity and a faster rate than the Freundlich model.
Abstract: A novel adsorbent: Fe2+-modified vermiculite was prepared in a two-step reaction. Adsorption experiments were carried out as a function of pH, contact time, and concentration of Cr(VI). It was found that Fe2+-modified vermiculite was particularly effective for the removal of Cr(VI) at pH 1.0. The adsorption of Cr(VI) reached equilibrium within 60 min, and the pseudo-second-order kinetic model best described the adsorption kinetics. The adsorption data follow the Langmuir model more than the Freundlich model. At pH 1.0, the maximum Cr(VI) sorption capacity (Q max ) was 87.72 mg · g−1. Desorption of Cr(VI) from Fe2+-modified vermiculite using NaOH treatment exhibited a higher desorption efficiency by more than 80%. The sorption mechanisms including electrostatic interaction and reduction were involved in the Cr (VI) removal. The results showed that Fe2+-modified vermiculite can be used as a new adsorbent for Cr(VI) removal which has a higher adsorption capacity and a faster adsorption rate.
TL;DR: In this paper, the authors investigated the effect of organic matter decomposition on the breakdown of K-rich micaceous minerals in the rhizosphere zone of alfalfa and found a significant increase in total K uptake in pots containing trioctahedral mica (phlogopite) and OM as compared with non-OM treatments.
TL;DR: The use of low-cost minerals in combination with ultrafiltration membranes can be employed to treat industrial wastewater, resulting in a final effluent with very low copper concentrations.
TL;DR: In this article, the adsorption capacity of vermiculite, a natural clay, for removing dibenzothiphene (DBTP) from water solutions was investigated.
Abstract: The adsorption capacity of vermiculite, a natural clay, for removing dibenzothiphene (DBTP) from water solutions was investigated. DBTP is an organic compound with sulfur, commonly found in fossil fuels and coal. This compound can also be found in the environment due accidental spills of oil and derivatives. Due to its structure and physical–chemical properties it is considered a persistent compound. Vermiculite (VT) was used as an adsorbent in its natural form, impregnated with copper ions (Cu-VT), and hydrophobically modified (HDTMA-VT) by replacement sodium cations by hexadecyltrimethyl ammonium ion. The results showed that DBTP was adsorbed in considerable amounts by HDTMA-VT; however, the Cu-VT adsorbed DBTP in some proportions of HDTMA-VT. Because of the presence of sulfur atoms in the structure of the molecule, π complexation can be observed. The adsorption isotherms were treated by the Freundlich equation. The values of K
f are similar to Cu-VT and HDTMA-VT, showing that the adsorption may be either through hydrophobic interactions or interactions through the formation of π complex. Meanwhile, the results with the VT (natural form) showed a much smaller value of K
f. It is believed, compared with the literature, and because of the chemical composition of the vermiculite, that the adsorption mechanism is also conducted by π complexation, considering the absence of organic carbon content.
01 Jan 2010
TL;DR: The results showed that the adsorption capacity for dye increased with increasing pH, contact time and initial dye concentration, but decreased with increasing temperature, ionic strength and sodium dodecyl sulfate concentration in the present of the surfactant.
Abstract: 一系列(丙烯酸的酸) chitosan-g-poly ， /vermiculite hydrogel composites 被综合并且为象蛭石内容那样的进程参数的效果的调查用作吸附物，染料答案的 pH ，接触时间，染料答案的起始的集中，温度，从水的答案的甲又蓝色( MB )的移动上的表面活化剂钠 dodecyl 硫酸盐的离子的力量和集中。结果证明为染料的吸附能力与增加 pH，接触时间和起始的染料集中增加了，但是与表面活化剂在礼品增加温度，离子的力量和钠 dodecyl 硫酸盐集中减少了。MB 的吸附动力学到 hydrogel 上，合成跟随的假秒顺序动力学和吸附平衡数据服从了兰米尔等温线。由介绍 10 wt% 蛭石进 chitosan-g-poly (丙烯酸的酸) 聚合网络，获得的 hydrogel 合成为 MB 显示出最高的吸附能力，然后能在一个废水处理过程为 cationic 染料移动被认为是潜在的吸附物。
TL;DR: In this paper, soil from the 2002 Hayman, Colorado, fire was analyzed by X-ray diffraction, and the results indicated fire impacts the structure of soil, including alteration of the 001 illite peak, the 00 1 kaolin peak, and a decrease in the swelling com- ponent of mixed-layer illite/smectite.
Abstract: High-intensity forest fires can degrade, collapse, or completely destroy clay minerals in soils, with signatures of these changes remaining for years after the burns. To ascertain immediate impacts of high-intensity fire on soil clay minerals and mineral recov- ery over time, soil from the 2002 Hayman, Colorado, fire was analyzed by X-ray diffraction. Sample locations included burned soil from within the perimeter of the fire, unburned soil near the origin, and soil from adjacent historic burns. The unburned soils contain mixtures of illite, mixed-layer illite/smectite and illite/vermiculite, kaolin, and mixed-layer chlorite. Surface soils (surface-7.7 cm) contain illite, mixed-layer illite/smectite, and kaolin. Sub- surface soils (7.7-13.0 cm) contain mixed-layer illite/vermiculite, in addition to the same minerals found at the surface. Deep soils (13.0-27.0 cm) show disappearance of mixed- layer illite/smectite and illite/vermiculite and show evidence of the presence of mixed-layer chlorite. Comparisons between recently and historically burned soils and unburned soils showed slight trends in alterations of clay mineral structures in the surface soil, including alteration of the 001 illite peak, the 001 kaolin peak, and a decrease in the swelling com- ponent of mixed-layer illite/smectite. These trends indicate fire impacts the structure of soil
Patent•
28 Sep 2010
TL;DR: In this article, a method for producing laminar phyllosilicate particles (for example: kaolinite, montmorillonite, pyrophyllite, bentonite, smectite, hectorite, sepiolite, saponite, laponite, halloysite, vermiculite, mica, chlorite, illite and mixtures) with or without surface modification is presented.
Abstract: The present invention relates to a method for producing laminar phyllosilicate particles (for example: kaolinite, montmorillonite, pyrophyllite, bentonite, smectite, hectorite, sepiolite, saponite, laponite, halloysite, vermiculite, mica, chlorite, illite and mixtures) with or without surface modification, the largest dimension of which (in the so-called D100) has a size of 0.05 to 15 microns; as well as to the phyllosilicate particles that can be produced according to said method and to the use of such particles as additives in plastic or ceramic matrices for producing materials that can be used in multiple sectors.
TL;DR: In situ neutron scattering experiments designed to follow amino acid adsorption on an exchanged, 1-dimensionally ordered n-propyl ammonium vermiculite clay show chiral specificity, measured in situ, in real time in the neutron beam, is of interest for the question of whether clays could have played an important role in the origin of biohomochirality.
Abstract: Recent work suggests a link between chiral asymmetry in the amino acid iso-valine extracted from the Murchison meteorite and the extent of hydrous alteration. We present the results of neutron scattering experiments on an exchanged, 1-dimensionally ordered n-propyl ammonium vermiculite clay. The vermiculite gel has a (001) d-spacing of order 5nm at the temperature and concentration of the experiments and the d-spacing responds sensitively to changes in concentration, temperature and electronic environment. The data show that isothermal addition of D-histidine or L-histidine solutions produces shifts in the d-spacing that are different for each enantiomer. This chiral specificity is of interest for the question of whether clays could have played an important role in the origin of biohomochirality.
TL;DR: In this article, X-ray diffraction analysis of a pale-podzolic soil for five years under conditions of a model field experiment was carried out, and it was found that the main changes of the biotite in all the horizons included the degradational transformation of its crystal lattice to interstratified mica-vermiculite structures.
Abstract: The biotite changes in the 1–5 μm fraction after its occurrence in the F, H, AE, and E horizons of a pale-podzolic soil for five years under conditions of a model field experiment were assessed by X-ray diffraction analysis. It was found that the main changes of the biotite in all the horizons included the degradational transformation of its crystal lattice to interstratified mica-vermiculite structures and vermiculite. The intensity of this process gradually decreased from the F horizon down the profile in parallel with the decrease in the amount of roots and the abundance and activity of microbiota. Chloritized structures were present among the products of the biotite weathering in the H, AE, and E horizons; the degree of chloritization gradually increased from the H horizon to the E horizon. The main identified products of the biotite weathering in the AE and E horizons formed during the 5 years of the model experiment were identified in the clay and fine-silt fractions from these horizons of the native pale-podzolic soils. Therefore, the vermiculite, soil chlorite, and mixed-layer illite-vermiculite minerals in the soils studied could be considered as products of the recent soil functioning. The obtained results and literature data showed that the weathering of biotite resulted in the formation of K- and Al-buffer systems.
TL;DR: In this article, the authors investigate changes in mineralogical composition resulting from the bio-leaching of a black schist ore that contained pyrrhotite, pyrite, sphalerite, pentlandite, and chalcopyrite as the main sulfide minerals.
TL;DR: In this article, the influence of ammonium quaternary compounds as coupling agent in polyethylene/clay nanocomposites to improve the performance of polyethylenes used as packaging barrier material was investigated.
Abstract: This work investigates the influence of some ammonium quaternary compounds as coupling agent in polyethylene/clay nanocomposites to improve the performance of polyethylene used as packaging barrier material. The 3 wt % of vermiculite used as a nanofiller was added to linear low-density polyethylene (LLDPE) and to linear low-density polyethylene grafted with maleic anhydride (LLDPE-g-MA). The analysis results revealed that the influence of both the clay exfoliation in a polymer matrix and the coupling agents on the barrier properties were significant. Among the coupling agents used, cetylpropyldimethylammonium chloride yielded the best result for vermiculite exfoliation. A reduction of up to 18% in the oxygen-permeability coefficient was observed in the nanocompounds with exfoliated vermiculite. The nanocomposite produced with vermiculite did not prove to be efficient as a moisture barrier against according to the analysis performed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
TL;DR: In this article, a systematic study of the properties of layered silicates that could affect their hydrothermal stability at different pH is described: type of layers, octahedral occupancy, layer charge, and origin of the layer charge.
Abstract: Many environmental applications in the inorganic remediation field are based on the swelling and ion-exchange capacities of smectites, even though these can be affected by hydrothermal treatment in water and acidic media. Here a systematic study of the properties of layered silicates that could affect their hydrothermal stability at different pH is described: type of layers, octahedral occupancy, layer charge, and origin of the layer charge. The silicates studied were selected on the basis of their different characteristics associated with these properties. Kanemite (1:0 phyllosilicate), kaolinite (1:1 phyllosilicate), and pyrophyllite and talc (2:1 phyllosilicates with no-layer charge) were examined in order to determine the effect of layer structure, whereas the hydrothermal reactivity of silicates with different layer charge was analyzed by comparing the talc-hectorite-Laponite1 and talc-saponite-trioctahedral vermiculite series. Samples were treated hydrothermally at 300oC for 48 h in pure water and in a 0.01 M HNO3 solution and the final products were analyzed by X-ray diffraction, scanning electronic microscopy, and solid-state nuclear magnetic resonance spectroscopy. All layered silicates, except for kanemite, were found to remain intact after hydrothermal treatment in water and acidic media, with only minimal short-range structural changes observed. The extent of the structural changes depended on the octahedral sheet occupancy (greater extent) and the number of isomorphic substitutions (lesser extent), both of which weaken the structure.
TL;DR: Based on the characters of expanding and layer adsorbing of vermiculite, the authors in this article showed that the expanded times increase with the increasing of concentration of hydrogen peroxide.
Abstract: Based on the characters of expanding and layer adsorbing of vermiculite，industrial vermiculite samples from Weili Mine of Xinjiang Province were expanded by both chemical and microwave chemical methods. The influences to the exfoliation ratio of different parameters such as concentration of hydrogen peroxide, power of the microwave, heating time, ratio of solid-liquid, immersion time were discussed. And the expanded mechanism of vermiculite was also analyzed. The results indicate that the expanded times increase with the increasing of concentration of hydrogen peroxide, and the best expanding point appears when the concentration of hydrogen peroxide is 30%. The solid-liquid ratio of vermiculite and hydrogen peroxide has little effect on the expanding of vermiculite. The vermiculite samples could be expanded 8.5 times by heated 2 min under 800W microwave power after immersion for 12 h when the concentration of hydrogen peroxide is 30%. As a result, the vermiculite could be expanded because of the oxygen pressure produced by the decomposition of hydrogen peroxide into the vermiculite interlayer. When using the microwave chemical method, the pressure of both oxygen and interlayer water lead to the increases of the expanded times. And exfoliation vermiculite plays an important part in energy-saving and environmental treatment.
TL;DR: In this paper, a composite, chitosan-g-poly(acrylic acid)/vermiculite, was prepared by aqueous dispersion polymerization using chitasan as the stabilizer, acrylic acid as the monomer and vermiculites as the inorganic additive.
Abstract: In this study, a composite, chitosan-g-poly(acrylic acid)/vermiculite, was prepared by aqueous dispersion polymerization using chitosan as the stabilizer, acrylic acid as the monomer and vermiculite as the inorganic additive. It was then cross-linked with common divalent or trivalent cations to obtain adsorbents with a higher affinity for phosphate ions. Factors influencing the adsorption capacity were investigated, the results indicating that the trivalent ion cross-linked hybrid exhibited a potential for the removal of phosphate ions and that a lower concentration of cross-linking agent could achieve the complete cross-linking of carboxylate groups within the composite. The adsorption of phosphate ions onto the developed adsorbent was pH-dependent, with a lower pH yielding a higher adsorption capacity. The Langmuir and Freundlich models were used to describe the adsorption data; the maximum adsorption capacity of 22.64 mg/g was comparable with that reported for other adsorbents. Desorption studies showe...
TL;DR: In this article, the preparation and characterization of cadmium sulfide (CdS) particles grown on the Mg and Na-vermiculite (MgV, NaV) fractions of less than 40μm.