Showing papers on "Vermiculite published in 1995"

Effects of CO 2 enrichment and supporting material in vitro on photoautotrophic growth of Eucalyptus plantlets in vitro and ex vitro

Abstract: Eucalyptus camaldulensis shoots were cultured photoautotrophicallyin vitro for 6 wk with four different types of supporting materials (agar matrix, Gelrite matrix, plastic net, or vermiculite) under CO2-nonenriched or CO2-enriched conditions. Plantlets from each treatmentin vitro were then grownex vitro in a greenhouse for 4 wk. The growth and net photosynthetic rate of plantletsin vitro, as well as subsequent growth, survival percentage, transpiration rate, and net photosynthetic rate of plantletsex vitro were evaluated. CO2 enrichment significantly increased growth (total dry weight and number of primary roots) and net photosynthetic rate of plantletsin vitro, as well as the growth and survival percentage of plantletsex vitro regardless of the type of supporting materials. The growthin vitro was greatest in the vermiculite, followed by the plastic net, Gelrite matrix, and agar matrix (in descending order) under either the CO2-nonenriched or CO2-enriched conditions. The growth and survival percentage of plantletsex vitro were highest in the vermicultie under the CO2-enriched condition. The extensive root system producedin vitro was necessary for growth and survival of plantletsex vitro.

Direct Measurement of the Electric Double-Layer Structure in Hydrated Lithium Vermiculite Clays by Neutron Diffraction

Abstract: Neutron diffraction, in conjunction with isotopic substitution of Li-6 for Li-7 and H-2 for H-1, has been used to determine the structure of the electric double-layer region close to hydrated lithium vermiculite clay platelets. We have measured the intensities of the first 27 (OOl) Bragg reflections for samples in which the clay platelet spacing is 14.67 Angstrom. Difference analysis has then allowed us to establish the interlayer counterion and water distributions. We find that the lithium counterions are located midway between the clay platelets and form octahedral hydration complexes with six water molecules. The behavior of lithium is therefore rather different from that of the larger alkali-metal ions; sodium, potassium, and cesium. These ions prefer to bind directly to vermiculite clay surfaces, rather than fully solvate. Since only lithium-substituted vermiculites will swell macroscopically when soaked in water, we conclude that interlayer cations must detach themselves from the clay surfaces if the particles are to expand colloidally.

Characterization of clay–organic‐matter complexes resistant to oxidation by peroxide

Abstract: Summary In an acid soil, amounts or organic carbon resistant to peroxidation with hydrogen peroxide were strongly related to the proportions of expandable phyllosilicate (vermiculite, smectite) in the clay fraction, as measured by its K2O content and cation exchange capacity. This was taken to indicate that a substantial part of the organic matter resistant to oxidation was interlayered. The organic compounds in the clay-organic matter complexes were identified by Pyrolysis Field Ionization Mass Spectrometry (Py-FIMS). Alkyl-aromatics as well as carbohydrates, phenols, lignins, lipids and N-compounds were found in the C-horizon sample, whereas mainly alkyl-aromatics and N-compounds, more resistant to chemical oxidation, were associated with the A1 and Bw fine-clay fraction. This was interpreted as being due either to the evolution of the clay-associated compounds paralleling the mineralogical transformations, or to the selective adsorption of the more stable components.

Weathering of ammonium- or calcium-saturated 2:1 phyllosilicates by ectomycorrhizal fungi in vitro

Abstract: The ways through which ectomycorrhizal fungi benefit tree growth and nutrition have not been totally elucidated. Our study was therefore aimed at assessing fungal access to soil exchangeable and stable mineral reserves. The growth of different ectomycorrhizal fungi in bi-compartment Petri dishes with NH4+- or Ca-saturated vermiculite led to cation exchange reactions and to crystal lattice weathering. The presence or absence of soluble NH4+ or Ca did not seem to affect fungal mobilization potential. Oxalic acid appears to be involved in vermiculite weathering by Paxillus involutus and Ca ions could limit the acid dissolution of Ca-saturated vermiculite. The quantitative significance of such cation mobilization and mineral weathering still has to be assessed in situ and in association with ectomycorrhizal plants.

Dissolution process of phlogopite in acid solutions

Abstract: The alteration experiments of phlogopite with 0.01 N HCl solution containing 0.1 M NaCl at 50°, 80° and 120°C have been carried out to aid in the understanding of the dissolution process of mica and the formation of secondary phases such as vermiculite and interstratified mica/vermiculite. Twenty milligrams of phlogopite samples were suspended in 20 ml or 100 ml of leaching solution. In these experiments, the dissolution ofphlogopite occurred incongruently, where the preferential release of K occurred in almost all stages of the alteration reaction. In the 100 ml experiments, the priority in dissolution in the initial stage was in the order; K > Fe > Mg, Al > Si. This supports that phlogopite leaching is controlled by the mineral structure. At 80° and 50°C in the 20 ml experiments, the release of all elements except for K was nearly congruent. At 120°C in the 20 ml experiments, the dissolution was outwardly incongruent, which Fe decreased remarkably after six days and Al was released most slowly compared with all other elements in phlogopite. This is probably due to the precipitation of secondary phases such as aluminum and iron oxides and/or hydroxides. Vermiculite and R1-type interstratified mica/vermiculite, containing 70 ∼ 50% mica, were formed in the alteration process of phlogopite. The following two processes were confirmed for the formation of interstratified structure: Interstratified structure was formed (1) directly from phlogopite or (2) from vermiculite which was produced earlier from phlogopite by regaining of K from the ambient solution. It may depend on the release rate of K from phlogopite whether mica-vermiculite layer sequences develop or vermiculite-vermiculite sequences do.

Phyllosilicate Distribution and Origin in Aridisols on a Granitic Pediment, Western Mojave Desert

Abstract: There is considerable uncertainty about the extent of mineral weathering and neosynthesis in arid soils. Although researchers have speculated that smectite neosynthesis can occur in soils containing opaline silica cement, no evidence has been presented to support this hypothesis. We investigated the mineralogy of two Aridisols in the western Mojave Desert, California, to study phyllosilicate distribution and origin in soils with opaline silica. The clay fraction of both soils is dominated by Al-rich, dioctahedral smectite, characterized by a Mg-saturated d(001) spacing of 1.52 nm and a d(060) spacing of 0.149 to 0.150 nm. This smectite is also present in silt and sand fractions of deeper horizons, where it exists mainly as microagglomerates of clay-sized crystals. Biotite is most abundant in silt and sand fractions of near-surface horizons of both pedons, where physical weathering is greatest. Deep, alkaline, silica-rich horizons of both pedons contain more silt- and sand-sized vermiculite than biotite, probably due to rapid chemical weathering of biotite to trioctahedral vermiculite. Clay-and silt-sized hydroxy-interlayered 2 :1 minerals are present in the upper horizons of these soils. Given the lack of gibbsite and substantial amounts of kaolinite and Al hydroxy-interlayered 2 :1 phyllosilicates, we propose that neosynthetic dioctahedral smectite was the dominant sink for Al released by feldspar weathering in these Aridisols. Silica not consumed in smectite neosynthesis can cement microagglomerates. We further speculate that minimal physical weathering in the alkaline, high-silica environment of deep horizons favors aggregation of smectites to silt- and sand-sized microagglomerates.

Effect of cadmium on nitrogen fixing pea plants grown in perlite and vermiculite 1

Abstract: The effect of cadmium (Cd) on nitrogen (N2) fixing pea plants was studied. Perlite and vermiculite were compared as substrates in a hydroponic system where the plants were grown. In both experiments, there was no significant effect on nitrogenase activity when referred to fresh weight of nodules, but there was a reduction in the nodulation ratio (number of nodules developed per plant), even at low concentrations of available Cd. In plants grown in vermiculite, the nitrogenase activity expressed in terms of activity per nodule increased as Cd application increased; while in plants cultivated in perlite, that activity decreased when the applied Cd increased at the highest levels of Cd in the nutrient solution. Vermiculite had a significant interaction with the Cd in the nutrient solution, and therefore, we assume there was less Cd available to the plants than when perlite was used as the substrate. The loss of N2 fixation by the presence of Cd in plants grown in perlite has been related to a change...

Method of preparing an exfoliated vermiculite for the manufacture of a finished product

Abstract: A method of preparing particles of an exfoliated vermiculite for the manufacture of a finished product, such as a particle board, includes the steps of, if necessary, chemically modifying the vermiculite by impregnating the vermiculite with a suitable anhydride in a non-aqueous solvent; if necessary, applying to the particles of vermiculite an adhesion promoter to promote the adherence of a resin to the surfaces of the particles of vermiculite; and resinating the particles of vermiculite either with a thermoplastic resin which has been surface modified by irradiation or by fluorination, or by an isocyanate thermosetting resin, or by a dry powder novolac thermosetting resin; and if necessary removing any solvent present.

Goethitas na interface solo-rocha em amostras do Rio Grande do Sul e Minas Gerais

Abstract: Goethites from 23 yellowish (6YR - 2.5Y) saprolite materials representing the soil-rock interface of migmatite, andesite, rhyolite, basalt, sandstone, argillite and limestone, were analysed. These materials are differentiated by weathering stage, as indicated by their silicate mineral composition: halloysitic (0.7 and 1.0 nm halloysite); kaolinitic; gibbsitic; and mixed (kaolinite, mica, vermiculite and/or smectite). Iron content varies from 16 to 354 g kg -1 Fed, consisting mainly of goethite, which was concentrated as much as 1.4 to 8.9 times with a 5 mol L -1 NaOH boiling treatment, thus enhancing the XRD characterization of goethite. The goethites contain 1 to 27 cmol mol -1 Al, where samples > 20 cmol mol -1 Al are associated to gibbsitic saprolites, and the lower ones to reductive environments or to the presence of smectite. Their WHH(110) and (111) ranges, respectively, from 0.32 to 0.87°2θ and from 0.28 to 0.74°2θ; calculated SSA show a broad range from 56 to 153 m 2 g -1 . A WHH(110) > (111), and the intensity ratio I(110)/(111) > 1.2 are suggestive of goethites with an anisotropic crystal morphology, whose calculated MCD values in the a, b, and c directions, range from 10-28 nm, 5-11 nm, and 11-30 nm, respectively. Dehydroxilation temperatures T(DTA) range from 257 to 313°C, with lower values (257-265°C) for goethites with WHH(110) > 0.72°2θ. The six samples from basaltic saprolites show significant relation between WHH(110) and Al substitution (r = -0.960), and of Al with T(DTA) (r = 0.985), indicating that Al substitution increases crystallinity (= coherent domains), and consequently the thermal stability of goethite. Different parent materials, and their degree of weathering, represent different environments, thus affecting goethite properties. Established goethite properties indicative of pedoenvironments were useful to identify the environment and weathering processes of saprolites, thus confirming the continuity ofpedogenesis at the soil-rock interface.

Origin and evolution of the granite/serpentinite reaction zones at Wiry, Lower Silesia

Abstract: Contact schists between Variscan hybridal granitoid apophyses and older serpentinite at Wiry, Lower Silesia, are composed of phiogopite and chlorite, and their alteration products (vermiculite, smectite, regularly interstratified mica/vermiculite, various interstratified chlorite/vermiculite and chlorite/smectite with asymmetric iron location, and three-component interstratified mica/vermiculite/chlorite), as recognized by means of XRD examination and computer simulations. The peak contact metamorphism yielded disseminated tremolite-to-pargasite amphiboles, and minor apatite. Its conditions, determined from aluminium content and fluid inclusions in hornblende, achieved 2.6 Kbar and 560°C. The parent solutions had Ca-Na-CI composition of variable calcium and sodium proportions; the variations were related to albitization of the adjacent Strzegom granitoids. The layer silicates assemblage may be considered as an equivalent of a predecessor of weathering silicate nikiel ores from the worldwide-known deposit at the neighboring ultrabasic massif of SzkIary. Normal 0 21 false false false PL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Effect of boiling nitric acid and sodium tetraphenylboron on structural changes of micaceous clay minerals

Abstract: A comparative study on the structural changes of micaceous clay minerals has been made after extraction of K with boiling 1M HNO3 and sodium tetraphenylboron by X-ray diffraction analysis. In case of HNO3 extraction, the integral width of 1.0 nm peak decreased considerably, particularly, in the fine clay fraction; but in case of sodium tetraphenylboron, the integral width increased appreciably and new peaks appeared. It shows that while sodium tetraphenylboron causes transformation of mica into interstratified and vermiculite minerals, boiling HNO3 causes dissolution of finer particles. Differential X-ray diffraction (DXRD) shows that HNO3 treatment dissolved smectite and interstratified smectite, chlorite, vermiculite andfinerfractions of mica.

Buffer material or back-filling material for geological disposal of radioactive waste

Abstract: PURPOSE:To make it possible to improve the adsorbing efficiency of nuclides even in the condition of high ion intensity where the adsorbing efficiency of bentonite is decreased by mixing a specific ratio of vermiculite burned into bentonite conventionally. CONSTITUTION:The buffer material 4 or back-filling agent is made up of a mixture of bentonite and burned vermiculite, and it is preferable to mix 10 to 40 weight percent of vermiculite in it. This provides a high adsorption of radioactive nuclides such as Cs even in the condition of high potential of hydrogen and high ion intensity as well as the supplying function of underground water. Moreover, as the ratio of mixed vermiculite is 40 or less weight percent, the water-stopping efficiency of bentonite are hardly decreased.

Effects of Mechanical Handling on Green Lacewing Larvae (Chrysoperla Rufilabris)

Abstract: Lacewing larvae (Chrysoperla rufilabris), used for biological control of insect pests, are typically released by hand for treatment of small-scale ornamental and fruit crops. This study investigated the potential for mechanical release of larvae. Second instar larvae were mixed into vermiculite and rice hull carriers and subjected to vibrational and rotational motion. The number of live, mobile larvae reclaimed from the treated material was determined. While the mechanical treatments did not significantly reduce the number of mobile larvae recovered, rotation resulted in slightly greater larval damage than vibration.

Characterization of acid activated montmorillonite and vermiculite clays by thermal desorption and differential scanning calorimetric techniques

Abstract: Montmorillonite and vermiculite clays, activated with hydrochloric acid solutions of different concentrations, have been characterized by thermal desorption and differential scanning calorimetric (DSC) techniques using ammonia and pyridine as probe molecules. The amount of adsorbed ammonia is found to be about twice the amount of pyridine on all the samples as determined by thermal desorption studies. DSC studies reveal the heterogeneity of acidic sites on the activated catalysts. DSC thennograms show the existence of three distinct acidic sites with different strength on the surface of the catalysts.

1.4-nm Intergrade Mineral in Soils of Snbtropical China:A Review

Abstract: This paper is a review of some advances in the studies on 1.4-nm intergrade mineral of soils in sub-tropical China. 1) 1.4-nm intergrade mineral occurs ubiquitously in soils of subtropical China. The 1.4-nmrnineral in red soil and yellow soil is mainly 1.4-nm intergrade mineral, and in acidic yellow-brown soil (pH 5.5) is verniiculite alone or 1.4-nm intergrade mineral together with vermiculite. The distribution and thecontent of 1 .4-nm intergrade mineral in the mountain soils are more widespread and higher than those of thecorresponding soils in horizontal zone. 2) The interlayer material of 1.4-nin intergrade mineral ui these soilsappears to be hydroxy-Al polymers instead of hydroxy-Fe, proto-imogolite or kaolin-like material. There isa significant positive correlation between Al amount extracted from the soil with sodium citrate after DCBextraction and pH value of the citrate solution after the extraction. The citrate can also extract a certainamount of silicon from the soil, but the silicon may not come from interlayer of 1.4-nm intergrade mineral.3) It was seldom studied that either vermiculite or smectite did the natural 1.4-nm intergrade mineral comefrom in soil, or it was commonly thought to come from vermiculite. A recent report has revealed that itcan come from smectite. There are some different behaviors between the 1.4-nm intergrade mineral derivedfrom vermiculite and that from smectite. For example, they exert different influences on the formation ofgibbsite. The 1.4-nm intergrade mineral derived from smectite may promote the formation of gibbsite in theyellow soil. 4) The type of 1.4-nm minerals in soils. i.e., vermiculite or 1.4-nm intergrade mineral, may besignificant to soil properties, such as soil acidity, exchangeable Al, electric charge aiiiount and specific surfacearea. Therefore, the management for the soil in which 1.4-nm mineral is mainly 1.4-nm intergrade mineralor vermiculite should be dealt with differently.