Showing papers on "Vermiculite published in 1980"

Kaolins: sources of differences in cation-exchange capacities and cesium retention

Abstract: Seven kaolins from Georgia (southeastern U.S.A.), ranging from high to low commercial grade, were characterized by X-ray powder diffraction and chemical techniques to establish that the variation in quality was caused by impurities. The Ca and Cs cation-exchange capacities (CEC) varied from 2.67 to 8.17 and from 3.29 to 8.77 meq/100 g, respectively. Selective dissolution and correlation analyses strongly indicated that expandable 2:1 minerals, particularly smectite (1.2-5.9%), Were responsible for most of the observed variations in Ca CEC (r = 0.85*). The external surface CEC of kaolinite ranged from 0 to 1 meq/ 100 g. The positive significant correlation (r = 0.90**) between the Ca CEC and the K-mica content (0- 3.9%) suggested that Ca CEC may be related to the degree of mica weathering through an expandable mineral stage. The Cs-retention capacity (0.19-1.14 meq/100 g) was closely related to Cs-measured vermiculite content (r = 0.80"), and this content plus specific surface (R = 0.93**) or mica content (R = 0.86*). The Cs reten- tion appeared to be primarily related to the presence of interlayer wedges at mica/vermiculite XY interfaces.

Regularly Interstratified Chlorite/Vermiculite in Contact Metamorphosed Red Beds, Newark Group, Connecticut Valley

Abstract: A regularly interstratified chlorite/vermiculite occurs in red beds of the East Berlin Formation (Early Jurassic age) in the Connecticut Valley. The mineral is restricted to a 2.5-m wide zone of contact metamorphosed strata adjacent to and underlying the Hampden Basalt. Chemical and X-ray powder diffraction data indicate that the chlorite/vermiculite formed in response to lava-induced elevated temperatures and the availability of magnesium in the muds during and shortly after emplacement of the lava flow. Near the contact, hydrothermal fluids originating from the lava and from the synchronal weathering of basalt fragments by superheated pore waters provided a source of Mg. Further from the contact, magnesium was primarily derived from the thermal dissociation of dolomite. K2O concentrations and the distribution of clay minerals in the red mudstone suggest that the interstratified chlorite/vermiculite formed from preexisting illite or vermiculite as potassium was released and brucitic sheets were incorporated into interlayer positions.

Hydrothermal Effects on Cesium Sorption and Fixation by Clay Minerals and Shales

Abstract: The effects of hydrothermal conditions on the sorption and fixation of cesium by various clay minerals and shales were investigated. Hydrothermal heating, which may be expected in a radioactive waste repository, altered the clay minerals and shales and led to a decrease in their cation-exchange ca- pacity. Cesium sorption greatly decreased in micaceous vermiculite and in well-crystallized illites con- taining vermiculite upon hydrothermal treatment at 400~ and 300 bars pressure due to complete layer collapse. However, poorly crystallized illites heated as above showed either a small increase or only a slight decrease in Cs sorption because of partial layer collapse. These studies show that the decrease in Cs sorption is greater in well-crysallized illites than in poorly crystallized illites when treated similarly under hydrothermal conditions. Hydrothermal heating of Cs-sorbed and Cs-saturated samples increased the amount of Cs fixation in all minerals and shales as a result of collapse of the layers. For example, a sample of the Conasauga shale fixed only 18% of sorbed Cs before treatment but fixed 47% after hydrothermal treatment at 200~ and 300 bars pressure. Thus, hydrothermal conditions in a shale repository may be beneficial after leaked radioactive Cs ions are taken up by clay minerals in shales.

Mineralogical composition of the clay fraction of two fluvio-glacial sediments from east greenland

Abstract: The < 2 #m fractions of two fluvio-glacial sediments from East Greenland have been analysed chemically and by XRD and M6ssbauer spectroscopy. The bulk of each < 2 #m fraction consists of feldspars and micas (biotite) which are important constituents of the Pre- cambrian igneous and metamorphic rocks of the area. Significant amounts of vermiculitic and smectitic minerals are also present. Compared with similar minerals present in Danish soil clays, the Greenland vermiculite and smectite are characterized by a high degree ofcrystallinity and it is concluded that these minerals have been formed from biotite through K release and lattice expansion. These processes appear to have proceeded at a sufficiently high rate to yield significant amounts of vermiculite and smectite despite the cold climate prevailing in the area. The major part of Greenland is covered by inland glaciers, and exposed rocks and soils occur only in a rather narrow belt along the coasts. The surface of this ice-free belt consists mostly of solid rock although some sediments have been deposited by the glaciers either as moraines or melt-water deposits. The moraines are invariably coarse-grained and consist mainly of boulders. Most of the melt-water deposits also consists of rather coarse particles, but deposits containing significant amounts of < 2 #m material do occur (Jensen, 1965), these generally forming in glacial lakes at or near the edge of the glaciers (Weidick, 1976). Clay-size particles are also found in suspended state in present-day glacial streams. In general it is assumed that the clay-size material occurring in Greenland and other cold regions consists to a large extent of chemically unaltered fragments of the original rocks rather than of true clay minerals. For example, Jensen (1965) found that clay from a presumed glacial lake deposit near Godth~tb contained 15-30~o vermiculite, 25-40~o biotite, 25-30~ oligoclase and small amounts of quartz and hornblende. All these minerals, including vermiculite, were present in the gneisses in the vicinity of the lake. However, work by Claridge (1965), Reynolds (1971) and Foged (1975) have shown that a certain amount of chemical weathering occurs in a cold climate, this involving, particularly, the formation of expandable clay minerals from biotite. In the present investigation the mineralogical composition of two < 2 pm separates from contemporary fluvio-glacial sediments from an East Greenland glacier has been determined, particular attention being paid to the possible presence of true clay minerals. SAMPLES

Effect of chemical pretreatment on x-ray powder diffraction characteristics of clay minerals derived from volcanic ash

Abstract: The effects of NaOAc removal of carbonates, HzOz removal of organic materials, and sodium citrate-bicarbonate-dithionite (SCBD) removal of iron oxides upon the X-ray powder diffraction (XRD) characteristics of clay minerals present within weathered volcanic ash deposits were examined. All pre- treatments of samples derived from the Ae and Bhf horizons containing volcanic ash resulted in dramatic increases in XRD peak intensities, while the treatment of IIC-horizon samples resulted in subdued XRD peak intensities. Also, the chemical treatments produced an apparent increase in the amount of expandable clay minerals within the Ae horizon, due probably to the hydrolysis and removal of interlayer A1 z+ when H~O~ and SCBD were used. Hence, poorly ordered and pedogenicaUy modified vermiculite or vermiculite/ montmorillonite interstratifications became "weathered" by H + attack and AP § removal in a manner sim- ilar to the natural processes which take place in the acid and eluvial A horizon. In addition, possible XRD peak modification due to the dilution of crystalline clay concentrations 'by amorphous clay-size material appeared to be subordinate to the laboratory-induced chemical alteration of the weathered clay minerals.

Swelling minerals in a basalt and its weathering products from Morvern, Scotland; I, Interstratified montmorillonite-vermiculite-illite

Abstract: The main clay mineral in weathered basaltic rubble has been shown by X-ray diffraction, chemical, infrared and differential thermal methods to be an interstratification of montmorillonite, vermiculite and illite in the approximate ratio 2:1:1, the montmorillonite having some degree of segregation and the vermiculite and illite being randomly interstratified All three components are dioctahedral, the swelling ones having a high tetrahedral charge, a large aluminium content, and very little iron Despite the 50% montmorillonite content of the mineral, its infrared absorption pattern is generally illitic in character

Soil clay mineralogies in relation to fertility management: Effect of soil clay mineral compositions on potassium fixation under conditions of wetland rice culture

Abstract: To evaluate the impact of soil clay mineralogy on the utilization efficiency of potassium fertilizers by rice, potassium fixation studies were made on fourteen soil clays having a range of mineralogical compositions. Soil clay with monomineralic beidellite fixed the highest proportion (76%) of the added potash, followed by clays containing either dominant or major vermiculite (51–66%). Fixation was significantly less severe (<35%) in vermiculitic clays containing hydrous mica. All the clays with mineralogical suites without beidellite or vermiculite, but consisting of montmorillonite, chlorite, hydrous mica, halloysite, kaolinite, and x‐ray amorphous material did not fix appreciable amounts (<18%) of the applied potassium.

Weathering and development of two contrasting soils formed from granodiorite in south-east Queensland.

Abstract: Mineral weathering in two soils, contrasting in colour and clay distribution, formed from granodiorite, was studied by X-ray diffraction, chemical and optical techniques. The feldspars, hornblende, and quartz become comminuted and appear to be weathering entirely by solution. The main source of clay is from the weathering of biotite which gives hydrobiotite, vermiculite, smectite and kaolin. Clay coatings lining cracks and voids are restricted mostly to the weathered rock and lower part of the soil, and their main source is from decomposing biotite nearby. This weathering study permits details of the clay distribution to be postulated. The clay-rich horizons seem to be formed by settling of residual material as other constituents are lost by solution. The resulting reduced permeability would be expected to increase surface run-off and lateral flow through the upper part of the soil, giving rise to the clay-depleted upper horizons. Clay illuviation seems to be insignificant in forming the horizon of maximum clay content.

NMR Study of Adsorbed Water — III Molecular Orientation and Protonic Motions in the One-Layer of a Li Hectorite

Abstract: Recently(1) the two-layer hydrate of a Na vermiculite has been studied by nuclear magnetic resonance (N.M.R.) of 1H and 2H nuclei, vermiculite sheets being oriented with their C* axes parallel to each other. A preferential orientation of the water molecules belonging to the hydration shell of the Na+ cations was observed and two correlation times were calculated from the variation of the spin-lattice relaxation time. There is a molecular rotation about the C2 axis and a rotation of the hydration shell about the C3 axis, the correlation time of the hydration shell rotation being longer than that of the molecular rotation about C2. The cation exchange capacity (C.E.C.) of vermiculite is such that the number of charge balancing cations, here Na+, is in a 1/6 ratio with respect to the number of adsorbed water molecules. This, in addition to the value of the basal spacing indicates an octahedral arrangement for the water molecules.

Resin composition containing polyamide

Abstract: PURPOSE: The titled composition, obtained by incorporating specific flakes of vermiculite in a polyamide, and having increased strength and elongation. CONSTITUTION: A resin composition consisting of 100pts.wt. resin containing a polyamide and flakes of vermiculite having an average aspect ratio ≥5 in an amount of 0.5W100pts.wt. dispersed in the polyamide. The amount of the vermiculite up to about 15pts.wt. increases both the strength and the elongation; however, the amount ≥15pts.wt. increases only the strength and reduces the elongation as compared with those in the absence of the vermiculite. The reduction in elongation is less than that in the case of mica, etc. For improving the strength, the amount is preferably 3W50pts.wt. COPYRIGHT: (C)1982,JPO&Japio

Soilless growing and rooting medium for plants - comprising clinoptilolite, vermiculite, peat and fertilisers

Abstract: Growing and rooting medium comprises (a) clinoptylolite, dried at 250-350 degC and screened into 08-20, 20-50 and 50-80 mm fractions in a ratio of 1:1:001 to 2:3:1; (b) a NP fertiliser in an amt to provide 01-05% of N and P; (c) a mixt of untreated vermiculite (particle size 0-10 mm) and expanded vermiculite (50-150 mm) in a ratio of 1:9 to 2:8; and (d) peat The (a):(c):(d) ratio is 10:001:001 to 5:2:3 The medium has a high sorptive capacity, contains significant amts of nutrients and trace elements, has a high moisture-retaining capacity, a low bulk density and good porosity, exhibits an approx neutral reaction in water, readily releases plant nutrient, and can be produced on a commercial scale

Expandable sheet material

Abstract: PURPOSE: To improve supporting force in thermal expansion, by sheeting a mixt. comprising a specified amount of an unexpanded vermiculite particle, an inorg. fibrous material and an org. elastic binder. CONSTITUTION: A mixt. comprising 85wt% or more unexpanded vermiculite particle, pref. 8W13wt% inorg. fibrous material and pref. 2W7wt% org. elastic binder, is sheeted. It is possible to widen the application of an expanded sheet material by use of an unexpanded vermiculite particle treated with a salt contg. a nitrate ion and an ammonium ion, because the vermiculite particle is expandable at a reduced temp of 200W400°C. COPYRIGHT: (C)1981,JPO&Japio

Process for producing a reversibly swellable, large-surface, crystalline micaceous mineral with crystal sheets separate from each other, and mineral product according to the process

Abstract: 1. Method for the manufacture of a mineral substance based on a reversibly expandible, three-flake mineral of crystalline form of large surface area, with separated crystal flakes, characterised in that in the 1st stage thermally expanded vermiculite or thermally expanded hydro-mica, these minerals also having intercrystalline embedded non-expandible mineral, of a grain size range of approximately 0.5 to 4 mm, is stirred in a large excess of water, then in a flowing current for a residence time of approximately 10 to 60 sec a flotation separation of the expanded, floating vermiculite or hydro-mica from non-expanded components takes place, then in the 2nd stage the separated, expanded vermiculite or hydro-mica, with a water content of approximately 90% based on the moist weight, is freed of the residual air held between the lamellae by storage under movement and at the same time the aqueous expansion of the mineral to its final state takes place, then in the 3rd stage a preliminary crushing is brought about by intensive movement of the mixture and at the same time its state of high intrinsic viscosity is destroyed (by thixotropy), in the 4th stage the mixture is ground under turbulent flow conditions to a grain size with a particle diameter of 0.1 to 0.3 mm, the thickness of the platelet-shaped particles being up to 200 micron, then in the 5th stage under laminar flow conditions at speeds of the material to be crushed relative to the crushing body of 10 to 120 m/sec grinding takes place to give over 50 percent by weight of tabular, extremely thin, uniformly even particles with a thickness of 0.5 to 10 micron and with surface dimensions corresponding to an equivalent diameter of 10 to 200 micron and a ratio of particle thickness : equivalent diameter equal to or less than 1 : 10, and then in the 6th stage by hydro-extraction the solid matter content of the mixture is brought to approximately 40%, and the porous product is collected, or if required is dried.