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A series of vermiculites pillared with mixed precursors of Al-Zr,Al-Hf and Al-Ce were obtained from natural vermiculite subjected to a process of negative charge reduction through hydrothermal treatment.The catalytic activity of t...
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A series of vermiculites pillared with mixed precursors of Al-Zr,Al-Hf and Al-Ce were obtained from natural vermiculite subjected to a process of negative charge reduction through hydrothermal treatment.The catalytic activity of the solids evaluated in the decane hydroconversion,was superior to that of recognized pillared clays and comparable to those of very active catalysts such as zeolites USY.The distributions of profiles of the reaction products suggest that the porosity/pore architecture of the pillared vermiculites should be similar to that of ultrastable Y zeolites.
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Vermiculite clay (VMT) was organically modified with a quaternary organic salt and added to polypropylene (PP). The compounds were prepared by melt intercalation using a twin extruder. The morphology of the composites was investig...
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Vermiculite clay (VMT) was organically modified with a quaternary organic salt and added to polypropylene (PP). The compounds were prepared by melt intercalation using a twin extruder. The morphology of the composites was investigated through wide-angle X-ray diffraction (WAXD). The WAXD results suggested that exfoliation phenomena were found for the composites with modified clay. The thermal properties of the obtained composites were studied by means differential scanning calorimetry (DSC) and thermogravimetry (TG) measurements. A variation in the crystallinity of PP was found. A significant increase of the thermal stability of PP was achieved in the presence of the modified VMT.
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The durability and thermal stability of hardened Portland cement pastes containing vermiculite (V) and expanded vermiculite (EV) exposed to high temperatures were studied. Different mixtures were prepared using 2.5, 5, and 10 wt% ...
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The durability and thermal stability of hardened Portland cement pastes containing vermiculite (V) and expanded vermiculite (EV) exposed to high temperatures were studied. Different mixtures were prepared using 2.5, 5, and 10 wt% of both types of V. Each mixture, after 28 days of hydration, was heated at 300, 600, and 800 °C for 3 h. Two modes of cooling were used; gradual cooling in air and rapid cooling in cold water. The percentage of residual strength, chemically combined water content, change in phase composition, and the thermal stability of the heated specimens were studied. The specimens cooled in water showed greater loss in strength than the air-cooled specimens. The presence of V improved the heat resistance of ordinary type I Portland cement (OPC) pastes. 5 wt% replacement revealed the best performance at all heating temperatures. The EV showed better thermal resistance than the nonexpanded one. Addition of silica fume (SF) with V in OPC pastes lead to superior performance. This can be explained as result of the combined effects of insulation properties of V and pozzolanic reactivity of SF which accounts for the notable increase in the residual strength for these mixes.
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The proposal of this research was to obtain products with higher porosity and specific surface area than the raw vermiculite for its possible application as a support material for CO2 adsorption. In addition, it was proposed to an...
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The proposal of this research was to obtain products with higher porosity and specific surface area than the raw vermiculite for its possible application as a support material for CO2 adsorption. In addition, it was proposed to analyze the possible geological implications of the products resulting from the hydrothermal treatment of ver-miculites in relation to their genesis. Hydrothermal treatment in the presence of CO2, at low temperature and pressure conditions, was carried out in two vermiculites from Uganda and China, with different behavior to thermal exfoliation and microwave irradiation. The untreated and treated samples were characterized by several techniques: X-ray diffraction (XRD) for obtaining the mineral composition; thermogravimetry (TG -DTG) for analyzing the thermal behavior; and BET isotherms for obtaining textural parameters. In addition, the hydro-thermal solutions were characterized by the pH and the measuring of the lixiviated elements with inductively coupled plasma mass spectrometry (ICP-MS). Vermiculite can be a suitable support for CO2 adsorbents, based on the SBET and Qm values, and it is susceptible to carbonation. The hydrothermal treatment produced water loss in the expanded vermiculites by CO2 replacement; as consequence, amorphization occurred in the purer Ugandan sample, and vermiculitization occurred in the less pure sample from China.The vermiculitization process in-dicates that the geological origin of vermiculite may be hydrothermal from phlogopite.
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Tunable wettability was studied on series of organo-vermiculites with different layer charge. Reduced-charge vermiculites (RCVts) were fabricated via one-step-heating method, which constituted a high-middle charge system. Organo-v...
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Tunable wettability was studied on series of organo-vermiculites with different layer charge. Reduced-charge vermiculites (RCVts) were fabricated via one-step-heating method, which constituted a high-middle charge system. Organo-vermiculites were prepared by four cationic surfactants and characterized by XRD, FT-IR and TG. The results indicated that organo monolayer has been formed between layers and resulted in a water repelling surface. The wettability of the organo-vermiculites was monitored by capillary rise experiments. Among those factors, layer charge took a decisive position in wettability alteration. These facts give an inspiration for regulating wettability of the high charge mineral surface. (c) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
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The article deals with the technology of obtaining foamed vermiculite from roughly dressed vermiculite ore under roasting and simultaneous separation of inert material in the specialized electric module trigger furnace.
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Three types of clay minerals [Montmorillonite (Mt), Bentonite (Bent), and Vermiculite (Vt)] and their synthetically modified forms were used for the preparation of Poly(methyl methacrylate) (PMMA) polymer composite films by the so...
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Three types of clay minerals [Montmorillonite (Mt), Bentonite (Bent), and Vermiculite (Vt)] and their synthetically modified forms were used for the preparation of Poly(methyl methacrylate) (PMMA) polymer composite films by the solvent casting method. The clay minerals were successfully modified by using the cationic surfactant, cetylpyridinium chloride (CPC) through ion exchange method to render all types of clay minerals miscible with polymer matrix. The results showed successful intercalation of CPC into the interlayer region of Mt and Bent as well as surface interaction with Vt. Intercalation of PMMA in the interlayer region of Mt, OMt, and OBent was observed whereas exfoliated structure obtained in case of Bent and Vt-based polymer composite films. The enhancement in thermal and mechanical properties was found more in case of organo clay-based PMMA polymer composite than pristine clay-based PMMA composite films.
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In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KC1, NH_4Cl, NaNO_3, ...
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In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KC1, NH_4Cl, NaNO_3, NaClO_4, Na_2SO_4, Na_2CO_3, Na_3PO_4 centre dot 12H_2O, MgCl_2 centre dot 6H_2O, CaCl_2 centre dot 2H_2O, BaCl_2, SrCl_2 centre dot 6H_2O, CuCl_2 centre dot 2H_2O, CoCl_2 centre dot 6H_2O, NiCl_2, AlC1_3, and CrCl_3 centre dot 6H_2O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg~(2+), Ca~(2+), Sr~(2+), and Ba~(2+)), heavy metal ions (Cu~(2+), Ni~(2+), and Co~(2+)) and trivalent cations (Al~(3+) and Cr~(3+)) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na~+, K~+ and NH_4~+), monovalent anions (Cl~-, NO_3~-, and ClO_4~-) and multivalent anions (SO_4~(2-), CO_3~(2-), and PO_4~(3-)) acted as indifferent ions for these clay particles.
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In this work, the effect of natural (NV) and expanded (EV) vermiculite clays on the properties of biopolyethylene (BioPE)-vermiculite clay biocomposites was investigated. It was observed that the addition of NV and EV clays to Bio...
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In this work, the effect of natural (NV) and expanded (EV) vermiculite clays on the properties of biopolyethylene (BioPE)-vermiculite clay biocomposites was investigated. It was observed that the addition of NV and EV clays to BioPE increased the Heat Deflection Temperature (HDT) and improved the fire retardance. In general, the degree of crystallinity (X-c) of BioPE decreased with the increase in the NV clay content, whereas in the presence of EV clay, the decrease in the X-c was only observed for the EV clay content above 3 phr. From optical microscopy (OM) it was observed that EV clay particles were better dispersed in the BioPE matrix, whereas many NV clay agglomerates were formed. SEM micrographs showed a lack of adhesion between the BioPE matrix and the NV or EV clay, resulting in a decrease of tensile and impact strength. Rheological measurements under oscillatory shear flow indicated the formation of a percolated network structure in the BioPE-NV and BioPE-EV biocomposites containing 5 and 10 phr of NV or EV clay. The biocomposite containing 10 phr of EV clay presented the higher melt yield stress value. Rheological measurements at high shear rates showed that the processability of the biocomposites will be similar to that of neat BioPE.
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Vermiculite is a mineral with many potential uses in various industrial areas, such as in insulation, horticulture, and environmental applications. The regolith of the Sokli carbonatite intrusion in northern Finland consists of we...
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Vermiculite is a mineral with many potential uses in various industrial areas, such as in insulation, horticulture, and environmental applications. The regolith of the Sokli carbonatite intrusion in northern Finland consists of weathered micas which reportedly contain vermiculite. The aim of the present study was to characterize the weathered mica in order to determine if the weathered regolith contains vermiculite. If so, the value of the apatite-rich Sokli intrusion may increase, because the vermiculite could be classified as an ore in Sokli. For the characterization, mica fractions were investigated using electron probe microanalysis (EPMA), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The EPMA results show that the potassium (K2O) content of the mica investigated varies between 6.20 and 0.31 wt.%. The XRD results provided evidence that the interlayer distances in the mica vary between 10.1 and 14.7 angstrom. The TGA shows that the dehydration of the samples varies between 6 and 12 wt.% for temperatures up to 170 degrees C. Dehydroxylation takes place in three steps, as is characteristic for vermiculite. The results from this study revealed that mica in the weathered parts of the Sokli carbonatite is mostly vermiculite, and that the vermiculite was formed by the weathering of phlogopite. These results can be used to determine whether vermiculite is a possible future commodity at the Sokli carbonatite complex.
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