Showing papers on "Vermiculite published in 1991"

Preparation of porous materials by chemical activation of the llano vermiculite

Abstract: A B S T R A C T: A mild acid attack of the Llano vermiculite produces porous materials suitable for use as cracking catalysts and/or catalysts supports. After HCI attack at 80~ (1 M), the number of acid sites measured by the Hammett indicator method is ~0.50/nm 2, and the specific surfaces are 245 m2/g after calcination at 550~ (4 h), and 55 m2/g after steaming at 750~ (4 h). The performance of leached (1 M HCI) vermiculite has been compared with another hydrocarbon cracking catalysty-AI203. The leached vermiculite produces a definite higher conversion and higher C3, C4 and gasoline yields, but much lower coke production. By electron microscopy, infrared spectroscopy, X-ray powder diffraction and thermal analysis, it has been shown that the leached vermiculite samples are composed of more or less attacked layers retaining their original platy morphology, and non-crystalline hydrated silica. Chemical analyses indicate that octahedral cations are dissolved first.

Characterization and genetic interpretation of clays in an acid brown soil (Dystrochrept) developed in a granitic saprolite

Abstract: X-ray diffraction and chemical analyses were performed on clay fractions separated from an acid brown soil (Dystrochrept) by means of size fractionations using high-gradient magnetic separation techniques. Breakdown of large phyllosilicates preexisting in the saprolite involved physical fragmentation and mineralogical transformations strongly related to chemical weathering. Compared to the C horizon, the proportion of chlorite and vermiculite decreased strongly in the silt and coarse-clay fractions of the Al horizon, but was maintained in the finer clay fraction (< 1 μm). The distribution of mica in the different fractions was quite the opposite. Micas are the major component of the Al, 1–2 μm fractions, and their proportion progressively decreased with decreasing fraction size. Thus, it is concluded that during fragmentation and/or simple transformation of the larger phyllosilicates, clusters of chlorite, mica/vermiculite, and vermiculite layers were preferentially affected. A concentration of mica layers took place in the coarse clay fractions as chlorite and vermiculite residues were accumulated in the fine clays. The process involved the loss of Fe and Mg, leaving, or forming, more aluminous dioctahedral minerals. As the transformation processes occurred, dissolution of preexisting minerals led to the precipitation of amorphous and/or crystalline Fe- and Al-oxides, and possibly of phyllosilicates. The new phyllosilicates appear to be montmorillonitic. The most abundant end products of the weathering processes in either the Al or the Bw horizons appeared to be quite different. In the Al horizon they were identified mainly a hydroxyl-Al (Fe) intergrade smectite (montmorillonite), whereas in the Bw horizon the major component was an intergrade vermiculite originating, at least in part, from chlorite.

Dehydration and rehydration of saponite and vermiculite

Abstract: The rehydration properties and behavior of interlayer cations of Ca-, Mg-, Na-, and K-saturated homoionic saponite and vermiculite heated at various temperatures were examined and their rehydration mechanisms elucidated. The most notable features of saponite were (1) except for the Mg- saturated specimen, all saponite samples rehydrated until the crystal structure was destroyed by heating; (2) the rehydration rate in air after heating decreased in the order: K + > Na § > Ca 2+ > Mg2+; (3) the interlayer cations apparently migrated into hexagonal holes of the Sit4 network on thermal dehydration; and (4) the b-parameter expanded on thermal dehydration. The rehydration properties and behavior of interlayer cations of vermiculite were: (1) except for the K-saturated specimen, all vermiculite samples rehydrated until the crystal structure was destroyed by heating; (2) the rehydration rate in air after heating decreased in the order: Mg 2+ > Ca ~+ > Na + > K+; (3) the interlayer cations apparently did not migrate into the hexagonal holes, but remained at the center of the interlayer space, even after thermal dehydration; and (4) except for the K-saturated specimen, the b-parameters of the samples contracted on thermal dehydration. The different rehydration properties of saponite and vermiculite were apparently due to the behavior of the interlayer cations during thermal dehydration. For rehydration to occur, the interlayer cations of saponite had to migrate out of the hexagonal holes. Consequently, saponite saturated with a large cation rehydrated rapidly, whereas saponite saturated with a small cation rehydrated slowly. On the other hand, the interlayer cations of vermiculite remained in the interlayer space; therefore, the rehydration properties of vermiculite were strongly affected by the hydration energies of the interlayer cations. Fur- thermore, electron diffraction patterns suggested that the saponite and vermiculite consisted of random stacking and ordered stacking of adjacent 2:1 layers, respectively. The nature of the stacking of the minerals seemed to be the most important factor controlling the behavior of interlayer cations in the thermal dehydration process.

Partially dehydrated vermiculite flakes and method of making same

Abstract: Intumescent vermiculite flakes useful in mountings of catalytic converters are prepared by partially dehydrating vermiculite ore to afford a uniform content of chemically bound water from about 10 to 32% by weight and a uniform bulk density from about 02 to 09 g/cm 3 Such a mounting affords good support to the monolith at warm-up temperatures, exerts adequate holding forces at operating temperatures without danger of cracking the monolith, and does not incur gradual reduction in holding forces at operating temperatures The mounting layer can be applied as either a mat or a paste

Protection of Nitrosomonas europaea colonizing clay minerals from inhibition by nitrapyrin.

Abstract: Nitrate production by Nitrosomonas europaea in inorganic liquid medium containing ammonium was limited by reduction in pH. In the presence of montmorillonite and vermiculite, expanding clays with high cation-exchange-capacity (CEC), nitrite yield was increased, ammonia oxidation continued at pH values below those which inhibited growth in the absence of clays and growth was biphasic. The first phase was similar to that in the absence of clays, while the second was characterized by a lower rate of nitrite production. Illite, a non-expanding clay with low CEC, had no significant effect on ammonia oxidation, while oxidation of ammonia-treated vermiculite (ATV) occurred with no significant change in the pH of the medium. ATV, montmorillonite and vermiculite, but not illite, protected cells from inhibition by nitrapyrin at concentrations inhibitory to cells growing in suspended culture. This protection was maintained in ATV homo-ionic to Al3+, but montmorillonite made homo-ionic to Al3+ did not provide protection from inhibition. Attachment of cells to clays with high CEC is therefore advantageous in providing exchange at the clay surface of NH+4 and H+ produced by ammonia oxidation, in reducing pH toxicity, and in protecting cells from inhibition.

High-elevation forest soils of the southern appalachians. ii : geomorphology, pedogenesis, and clay mineralogy

Abstract: We investigated soil mineral weathering sequences in three geologically distinct high-elevation areas of southern Appalachian spruce-fir (Picea rubens Sarg.-Abies fraseri [Pursh.] Poir) forests in order to elucidate the pedogenic factors that distinguish these unique soils from their low-elevation counterparts. Four pedons representing a developmental sequence ranging from soils having distinct spodic field morphology (E plus Bhs horizons) to those having either minimal (weak E horizons) or no spodic character (umbric epipedons/cambic horizons) were selected for further study from a total of 35 excavated pits. Whereas the mineralogy of sand and silt fractions reflected inheritance from parent materials, clay mineral suites of all soils were very similar, indicating biotic and climatic controls on weathering. Surface-horizon clay fractions were dominated by regularly interstratified mica/vermiculite and high-charge smectite, which decreased with depth in all profiles. Subsoil clay fractions were principally composed of gibbsite and hydroxy-interlayered vermiculite. Genesis of secondary 2:1 layer silicates in these soils occurs initially by the pseudomorphic transformation of biotite to both hydrobiotite and vermiculite. However, direct conversion of biotite to kaolinite is of little importance in these soils. The demonstrated mobility of Al-organic complexes out of surface horizons and the inability of hydroxy-Al interlayers to form in vermiculite in the presence of organic acids suggest that these soils are undergoing early stages of podzolization and that they are more similar to northern Appalachian Spodosols than they are to adjacent low-elevation soils of the southern mountains.

``Dealumination'' and Aluminum Intercalation of Vermiculite

Abstract: Dealumination of vermiculite was carried out using (NH4)2SiF6 solutions. The dealuminated products were studied by high-resolution solid state 29Si and 27Al nuclear magnetic resonance. A decrease in the cation-exchange capacity (CEC) resulted from the partial removal of Al from the tetrahedral layer, which decreased the framework negative charge, and from the partial replacement of Mg by Al in the octahedral layer, which increased its positive charge contribution. The lowest CEC was obtained by swelling the structure with butyl-ammonium prior to the reaction with (NH4)2SiF6. Thus, CECs in the range observed for beidellite were measured; however, the lowest (Al/Si)IV ratio was still more than twice as high as in beidellite. In addition, the dealumination reaction yielded noncrystalline silica as a by-product.

Chlorite Vermiculitization and Pyroxene Etching in an Aeolian Periglacial Sand Dune, Allen County, Indiana

Abstract: Weathering has etched and deeply-denticulated the constituent orthopyroxenes, and chlorite has been transformed to vermiculite in the upper 3 m of an aeolian, periglacial sand dune formed in northeastern Indiana about 13,000 b.p. Pyroxene weathering begins with the development of cleavage-parallel etch pits on {010} and {100} surfaces. These pits coalesce and eventually crop out on basal surfaces as denticulations. The mean denticulation size increases logarithmically toward the surface, and the denticulation size of the orthopyroxenes is a quantifiable feature of the weathering process. Ferruginous pendants, microboxworks of iron oxides, and other indications of iron redeposition within the ortho-pyroxene microenvironments were not observed. Chlorite in the dune has been weathered to vermiculite. The parent chlorite is a high-Fe variety, and the transformation to vermiculate does not involve the development of a chlorite/vermiculite intermediary phase. Fe2+ is oxidized as part of the transformation process and this iron is retained in the sediment as discrete goethite and as crystalline and noncrystalline coatings on the dune grains. The vermiculite from depths shallower than 64 cm is only partly expandable and is completely collapsed by K-saturation or heat treatment. This is a hydroxy-Al vermiculite and its formation is typical of intense weathering under the acid conditions prevalent at the dune surface.

Local environment of intercalated lanthanide ions in vermiculite

Abstract: The local structure of interlayer lanthanide ions ion-exchanged into vermiculite clay has been determined as a function of the nature of the lanthanide ion and of the physical form of the sample (powders and oriented films) using X-ray absorption spectroscopy. Water molecules form the first coordination shell, with metal–oxygen bond lengths of 2.52 (La—O), 2.53 (Ce—O), 2.32 (Er—O) and 2.33 A(Lu—O), very similar to the corresponding interatomic distances in aqueous lanthanide nitrate solutions. However, the coordination numbers of the heavier lanthanide ions are greater than those of the lighter ones, in contrast to the behaviour observed in solution. This variation is attributed to the participation of coordinated water in the transmission of local charges on the lanthanide ions to the vermiculite layer surface. Across the lanthanide series a significant difference in coordination number between La-vermiculite powder (6 neighbours) and film (9 neighbours), is reduced in the cerium sample (7.5 and 9, respectively) and reached a negligible variation in the heavier (Er, Lu) vermiculites. This is attributed to a diffusion phenomenon of water within the vermiculite interlayers. Preliminary a.c. conductivity measurements of Lu-vermiculite films are in the range of 10–6 S cm–1.

The chemical composition and structure of a 14 a intergradient mineral in a korean ultisol

Abstract: A B S T R A C T: An intergradient 14 A mineral showing X-ray diffraction features of "chloritized" vermiculite in a Korean Ultisol was studied. The structural formula of the whole 2 : 1 layer-silicate (14 A mineral and mica) in the Na+-saturated 0.24).5 /~m fraction was obtained by elemental, thermogravimetric and 29Si and 27AI nuclear magnetic resonance spectroscopic analyses in combination with extraction of the interlayer material from the 14 A mineral by hot 1/3 M sodium citrate treatment. This formula showed: (1) the 2 : 1 layer contains nearly one AI 3+ in four tetrahedral positions, and AI 3+ is the dominant cation in the octahedral sheet; (2) K +, exchangeable Na + and sodium citrate extractable 1 : 1 layer occupy the interlayer space of the 14 & mineral in similar proportions. Very little interlayer K was replaced by Na + during the citrate treatment. Possible schemes of alteration of the 2 : 1 layer to the 1 : 1 layer as its interlayer material are discussed. Many soils formed under leaching conditions in the humid temperate region contain a 14 intergradient mineral as a major clay component. It is called partially interlayered or "chloritized" vermiculite. "Chloritized" vermiculite is commonly identified by X-ray powder diffraction (XRD) analysis: it does not collapse readily when K-saturated, but its 14 ~ reflection becomes diffuse and shifts toward 10 ~ on heating to 300 ~ and 550~ (Rich, 1968; Barnhisel & Bertsch, 1989). When A1 is removed by treatment with reagents such as hot 1/3 M sodium citrate, the mineral collapses on K-saturation but does not expand with glycerol solvation. The following two observations on the 14 ~ mineral in several Korean Ultisols and Alfisols, however, questioned this identification: (1) the citrate treatment which resulted in removal of the interlayer material also resulted in dissolution not only of A1, but of Si at the molar Si/A1 ratio of -1-0; (2) the dissolution of the kaolin group mineral was indicated by difference infrared (IR) spectroscopy but not by XRD analysis for the citrate-treated and untreated samples. On the basis of these observations, Wada & Kakuto (1983a,b) suggested that the 14 & mineral is an intergradient vermiculite-kaol in mineral, in which each 14 & layer partially transforms into double kaolin layers. Later, ultramicrotomy and transmission electron microscopy (Wada & Kakuto, 1989) showed that the 14 ~ mineral particles are composed of stackings of more or less curved and often discontinuous silicate layers. On saturation with K +, the silicate layers had spacings of 14-10 ~, with 14-12 being dominant. There was, however, no indication of the double kaolin layers with a spacing of 7 & close to the edge of each 14 & layer as suggested earlier. In the present study, XRD, chemical, thermogravimetri c and 29Si and 27A1 nuclear

Flame spread barrier made from mechanically delaminated vermiculite sheet

Abstract: One or more layers of a sheet comprising (1) 60% to 99%, based on the weight of solids, of vermiculite delaminated by mechanical means only, (2) 1% to 40%, based on the weight of solids, of at least one fibrous material and (3) 0.1% to 4%, based on the weight of the vermiculite, of at least one flocculating agent, can be used to protect heat-sensitive substrates such as resin matrix composites from fire or heat.

The in Situ Weathering of a Test Mineral (Vermiculite) Introduced in a Podzol (Haplaquod) and in a Hydromorphic Soil (Haplaquept) Compared to the Soil Clay Minerals Evolution

Abstract: In the Landes du Medoc (France), the soil mantle is organized in short soil toposequences (10–20 metres) made of podzols (Haplaquods) in the less waterlogged upper part, and of hydromorphic soils (Haplaquepts) in the lower part. In the upper part, podzolization is shown by the strong redistribution of OM-Al complexes in a Spodic horizon. Because of the presence of these complexes in the groundwater, this process is likely to be active at present. In the eluvial horizons of podzols, the study of the clay minerals has revealed a weathering process by acidocomplexolysis. On the other hand, weathering in the hydromorphic soil has given intergrade minerals which reflects a simple acidolysis. Samples of a test-vermiculite were introduced in the main horizons of the soils. They were removed and reexamined after six months (winter period or summer period) or one year of in situ experiment. The weathering of the test-vermiculite showed distinctive features according to the soils and the seasons. After the summer period no change could be identified in the test-vermiculite from any of the two soils. After the winter period a few interlayers were blocked at 14 A (interlayered hydroxy-Al) in the vermiculite from the A 1 horizon of the hydromorphic soil. The phenomenon was more pronounced for the vermiculite from the E and Bh horizons of the podzol where most of the interlayers were blocked. According to experimental models such a behaviour is due to the presence of a non-complexing acidic medium in these horizons: this does not correspond to the results reduced from the study of the soil clay minerals.

Nitrification Related to Acidification and Silicate Weathering

Abstract: Experiments of nitrification were performed with NH + 4 saturated vermiculite as nitrogen source. The effect of the acification produced by the reaction of nitrification is evaluated concerning weathering effect either on the CaCO 3 present in the medium or on the vermiculite. A balance was made on the protons produced by the reaction and the release of elements in solution and their interlayer fixaiton by the vermiculite.

Spraying agent for inner wall surface of building

Abstract: PURPOSE:To obtain the title spraying agent capable of making up a sound- insulating, fireproof and moisture condensation-preventive wall surface on an asbestos layer, also of immobilizing said asbestos layer, by incorporating a water-based epoxy resin with inorganic porous granules and expandable silicate. CONSTITUTION:The objective spraying agent can be obtained by incorporating (A) a water-based epoxy resin with (B) inorganic porous granules (e.g. calcined vermiculite) and (C) an expandable silicate.

Yield increasing agent of mushrooms and culture thereof

Abstract: PURPOSE:To obtain a yield increasing agent for shortening (one month) a culture cycle of mushrooms, always harvesting maximum yield by blending Kanumatsuchi with vermiculite, edible oil, barley, soybean flour and rice bran CONSTITUTION:Kanumatsuchi is blended with vermiculite, edible oil, barley, soybean flour, rice bran and preferably rock wool to give the objective yield increasing agent Mushrooms are cultured in a medium containing the yield increasing agent, water and sawdust

Vermiculite utilizing bilogical deodorizing method

Abstract: PURPOSE: To always hold pressure loss in a bacteria immobilized bed containing peat on which bacteria having malodor decomposability are immobilized to a low level. CONSTITUTION: A deodorizing bacteria immobilized bed is formed by mixing peat supporting deoderizing bacteria and vermiculite and a malodor is passed through the immobilized bed to be deodorized. Pref., 30-70% of peat and 70-30% of vermiculite are contained in the immopblized bed. COPYRIGHT: (C)1992,JPO&Japio

Preparation of modifying and using aluminosilicates

Abstract: Mineral aluminosilicates enhanced as ion-exchange media for separating diverse ionic materials are provided by dry heating. A hydrated mineral alumino-silicate is irreversibly dehydrated in part, to improve the ratio of its affinity for preferred ions, relative to non-preferred ions, even though doing so reduces its affinity for both types of ions. Such dehydration is accomplished by heating the aluminosilicate until a temperature is reached at which its affinity for non-preferred cations is reduced enough that the ratio of its affinity for preferred ions to its affinity for non-preferred ions is greatly increased. Such aluminosilicates may be zeolites, such as clinoptilolite, or layered clays, such as vermiculite or smectite. 850° C. is an example of such temperature.

A method of rendering water resistant a vermiculite article

Abstract: A method of rendering water resistant a vermiculite article such as a film or coating comprised of delaminated vermiculite lamellae comprising the step of contacting the article with a solution of an inorganic monovalent cation selected from the group consisting of: H⁺, Na⁺, K⁺, Cs⁺, Rb⁺ and Fr⁺, and mixtures thereof.

Fiber-vermiculite composite sheet and manufacture thereof

Abstract: PURPOSE: To produce a fiber/vermiculite composite sheet useful as a flame- propagation barrier, etc., using a continuous papermaking machine by delaminating vermiculite only by mechanical shearing force, dispersing the delaminated vermiculite in water together with a fiber material and agglomerating the dispersion. CONSTITUTION: A shearing action is applied to an aqueous slurry of a vermiculite ore until a dispersion containing vermiculite lamella having a dimension of <=200 μm is obtained to effect the delamination of vermiculite only by mechanical shearing force. The objective sheet is produced by dispersing 20-99 wt.% (in terms of solid weight) of the mechanically delaminated vermiculite and 1-80 wt.% (in terms of solid weight) of at least one kind of fiber material (preferably a combination of glass fiber and wood pulp) in water and adding 0.1-10 wt.% (based on the vermiculite) of at least one kind of agglomeration agent to effect the agglomeration of the dispersion.

DTA of Pt exchanged vermiculite mineral

Abstract: DTA curves of Pt and Pd exchanged vermiculite mineral samples are presented The minor structural changes brought by introduction of these cations in Mg and Ni vermiculites are explained Results of chemical analysis and XRD are also discussed

Compost for growth of plant

Abstract: PURPOSE:To provide the subject compost for growth of plants excellent in water retention and air-permeability and having a property of prevention of moisture permeation by blending granular pumice and(or) granular vermiculite with the main component composed of granular rock wool and peat-moss. CONSTITUTION:Granular rock wool and peat-moss (e.g. material obtained by grinding sediment of peat-moss) are used as the main components and granular pumice and (or) granular vermiculite are blended with the above-mentioned main components to produce the objective compost for growth of plants. In addition, a pH adjusting agent (e.g. slaked lime) is preferably added thereto. As the mixture ratio, about 20-60vol.% granular rock wool, about 20-70vol.% peat-moss, about 10-40vol.% pumice or vermiculite and about 0.05-0.2vol.% pH adjusting agent are suitable. A suitable fertilizer component is additionally blended therewith in an amount of about 0.1-2vol.% according to the kind of use and the resultant mixture is placed at the service.