Showing papers in "Clay science in 1992"
TL;DR: In this paper, the formation process of kaolinite from the amorphous mixture of silica and alumina by hydrothermal reaction was studied by XRD, IR, DTA-TG, TEM, and high-resolution solid state 29 Si- and 27 Al-MAS/NMR.
Abstract: The formation process of kaolinite from the amorphous mixture of silica and alumina by hydrothermal reaction was studied by XRD, IR, DTA-TG, TEM, and high-resolution solid state 29 Si- and 27 Al-MAS/NMR. The amorphous mixture of the starting material prepared with commercially available silica-sol and alumina-sol was hydrothermally treated with distilled water in a Teflon pressure vessel at 220°C for a reaction time varying from 1 to 144 hours. The Q 4 state component of the amorphous starting material changed into an intermediate amorphous Q 3 state. The intermediate amorphous phase converted into crystalline kaolinite with spherical shape (Q 3 state). The yield and crystallinity of kaolinite increased with an increase in the reaction time
16 citations
TL;DR: In this article, a starting material of a mixture of rice husk ash, magnesium chloride and lithium chloride with a molar ratio of Si: Mg: Li = 8: 5.34: 0.66 was used for smectite synthesis.
Abstract: When rice husk is burnt, about 20 wt% of the husk remains as ash. The rice husk ash has more than 95 wt% of silica with high porosity and large surface area, because it still retains the skeleton of cellular structure. These properties of the rice husk ash can be used to synthesize siliceous raw materials such as clay minerals. Syntheses of smectite from the rice husk ash were conducted by using a starting material of a mixture of rice husk ash, magnesium chloride and lithium chloride with a molar ratio of Si: Mg: Li = 8: 5.34: 0.66. The optimal conditions of smectite synthesis is as follows
8 citations
TL;DR: In this paper, anion exchanged hydrotalcites have been characterized by means of X-ray, thermal and infrared spectroscopic methods, showing that the exchanged SO 4 occupied the site of CO 3.
Abstract: Anion exchanged hydrotalcites have been characterized by means of X-ray, thermal and infrared spectroscopic methods. The sample has been treated in the solution containing various anions such as S 2− , SO 4 2− , SO 3 2− , HSO 3 − , S 2 O 3 2− , S 2 O 4 2− , S 2 O 5 2− , SCN − . The dehydration temperature of structural OH as well as the CO 3 remarkably shifts from 400 to 480°C in the samples exchanged with anions such as SO 4 2− , HSO 3 2− , S 2 O 5 2− , which suggests the presence of some interactions between the anions and the structural OH. All the sulfur atoms exchanged are retained in the temperature up to 980°C. Infrared spectroscopic and thermogravimetric data show that the exchanged SO 4 occupy the site of CO 3
8 citations
8 citations
8 citations
TL;DR: The removal of acetaldehyde by sepiolite combined with 2-aminobenzoic acid (OABA) (sepiolite-OABA complex) from ambient air was studied in this paper.
Abstract: The removal of acetaldehyde by sepiolite combined with 2-aminobenzoic acid (OABA) (sepiolite-OABA complex) from ambient air was studied in comparison with that of the aldehyde by sepiolite, coconut-shell active carbon (carbon), 5A-zeolite, 13X-zeolite, diatomaceous earth, as well as these porous material-OABA complexes. Experiments were done at 25°C in ambient air. The removal rate of the aldehyde by these porous material-OABA (10%) complexes followed the order of sepiolite->> carbon->13X-zeolite->5A-zeolite>diatomaceous earth-OABA (10%) complexes. The amount of the aldehyde removed by the sepiolite-OABA complex was much larger than that by OABA and that by sepiolite itself
5 citations
TL;DR: In this paper, the adsorption of acetaldehyde by sepiolite combined with 2-aminobenzoic acid (sepiolite-OABA complex) was studied in comparison with that of the aldehyde by mere selforganite.
Abstract: The adsorption of acetaldehyde by sepiolite combined with 2-aminobenzoic acid (sepiolite-OABA complex) was studied in comparison with that of the aldehyde by mere sepiolite. Experiments were carried out at 25°C in ambient air having relative humidity of 9.0, 30, 60, and 80%. Combination of 2-aminobenzoic acid (OABA) with sepiolite was found to give big enhancement on the adsorptive capacity of sepiolite. For example, in 9.0% relative humidity, the adsorptive capacity of sepiolite combined with 10% OABA was about 10 times larger than that of mere sepiolite. In 30, 60, and 80% relative humidity, that of sepiolite combined with 10% OABA was about 30, 50, and over 100 times larger than that of mere sepiolite, respectively
4 citations
TL;DR: In this article, the main constituent minerals in the samples were identified to be halloysite(7A), mica, quartz, feldspar, and gibbiste by X-ray powder diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM).
Abstract: Some clay raw materials in Nepal were characterized and their aptitude for porcelain raw material was studied. The main constituent minerals in the samples were identified to be halloysite(7A), mica, quartz, feldspar, and gibbiste by X-ray powder diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM). The chemical composition of the bulk sample showed very low Fe 2 O 3 and TiO 2 contents, and therefore, the whiteness of sintered body is on a very good level. The vitrification temperature was around 1200°C and high bulk density still maintained in the temperature range from 1200 to 1350°C
4 citations
TL;DR: For example, this article showed that water molecules previously adsorbed on the surface of pyrophyllite and talc decreased both the strength and amount of acid sites, although the degrees of the decrease were smaller.
Abstract: Pyrophyllite and talc were shown to have acid sites on their surface, and the strength and amount of the acidity were much higher for pyrophyllite than talc. The strength and amount of the acidity of both minerals were not affected by the exchangeable cation species. Water molecules previously adsorbed on the surface of the minerals lowered both the strength and amount of the acid sites, although the degrees of the decrease were smaller than the case of montmorillonite. When the water was introduced after the adsorption of indicators, the water molecules did not affect voth the strength the amount of the acidity
4 citations
TL;DR: In this paper, the adsorption of tris(1,10-phenanthroline)copper (II) ([Cu(phen) 3 ] 2+ ) by a clay mineral has been studied with electron spin resonance (ESR) measurements.
Abstract: The adsorption of tris(1,10-phenanthroline)copper(II) ([Cu(phen) 3 ] 2+ ) by a clay mineral has been studied with electron spin resonance (ESR) measurements. The chelate, tris(1.10-phenanthroline)copper(II) ([Cu(phen) 3 ] 2+ ), is co-adsorbed with a large excess of racemic or enantiomeric [Ru(phen) 3 ] 2+ . The spectra of a freeze-dried sample of a clay-chelate adduct at 77 k show that there are two kinds of adsorption states: the one (denoted by state A) is characterized by the parameters of g II = 2.263 − 2.275 and A II = 151 − 160 G and the other (denoted by state B) by g II = 2.213 − 2.229 and A II = 150 − 186 G
4 citations
TL;DR: In this article, the gold decoration technique of electron microscopy was applied to natural (001) surfaces of two kinds of pyrophyllite crystals (green and white colored specimens) collected from ''Roseki» deposits distributed in the Shokozan area, Chugoku province, southwest Japan.
Abstract: The gold decoration technique of electron microscopy was applied to natural (001) surfaces of two kinds of pyrophyllite crystals (green and white colored specimens) collected from «Roseki» deposits distributed in the Shokozan area, Chugoku province, southwest Japan. The specimens are characterized by some parallel steps of malformed circular or polygonal forms with varying step separations. Crystals exhibit paired and single steps which may be correlated to 2M or 1T polytypes, respectively. The paired steps take place normally by the interlacing process on their crystal growth. The different surface microtopographs on both green and white colored crystals are explained based on the understanding on spiral morphology
TL;DR: In this article, the authors synthesize synthetic fluorine micas using talc and K 2 SiF 6 at 900°C for one hour in an electric furnace and the one dimensional Fourier synthesis showed that the electron density of K + in the interlayer site of synthetic micas increased and that of Mg 2+ from the octahedral site decreased.
Abstract: Fluorine micas were synthesized using talc and K 2 SiF 6 at 900°C for 1 hour in an electric furnace. With increasing K 2 SiF 6 /talc ratio, b and c unit cell parameters of synthetic fluorine micas were decreased. This result may be interpreted in terms of the shrinkage of the octahedral sheet by the loss of Mg 2+ from the octahedral site. Infrared absorption spectra of synthetic micas showed the splitting of the absorption band of Si-O stretching, which indicates that some alkali ions migrate into the interlayer site of silicate skeleton. The one dimensional Fourier synthesis showed that with the increase of K 2 SiF 6 /talc ratio the electron density of K + in the interlayer site of synthetic micas increased and that of Mg 2+ from the octahedral site decreased
TL;DR: In this paper, the authors examined the mineralogical composition of a Yellow-brown soil of China and found that micas and their transformation products dominated the clay fraction, however, the transformation products of micas were different between the fine and coarse (0.2-2 μm) clay fractions.
Abstract: Clay mineralogical composition of a Yellow-brown soil of China was examined. Common to the A and C horizons, micas and their transformation products dominated the clay fraction. The transformation products of micas were, however, different between the fine (<0.2 μm) and coarse (0.2-2 μm) clay fractions. Irregularly interstratified mica/smectite or mica/vermiculite/smectite of the smectite-rich phase was found in the fine clay fraction, while smectite and regularly interstratified mica/smectite were detected in the coarse clay fraction. The endo-type and exo-type K-replacement models were proposed to explain the different transformation products between the two clay fractions
TL;DR: In this article, the authors used X-ray diffraction patterns to determine the direction of the reaction in a natural mixture of kaolinite-pyrophyllite-boehmite.
Abstract: Hydrothermal experiments have been carried out to find the equilibrium conditions for the reactions: 2kaolinite = pyrophyllite + 2diaspore + 2water (1) kaolinite + 2quartz = pyrophyllite + water (2) As starting materials, a natural mixture of kaolinite-pyrophyllite-boehmite was used for the experiments. Determination of reaction direction was based upon X-ray diffraction patterns. It has been confirmed that the equilibrium curve for the reaction (1) passes through the points 325 ± 10°C at 1kb and 330 ± 10°C at 2kb, and the curve for the reaction (2) passes through 250 ± 10°C at 1kb and 260 ± 10°C at 2kb. The present temperatures for the reaction (2) are lower than any other one reported so far
TL;DR: In this paper, the particle size distribution of illite and iron oxide-precipitated illite was examined as a function of pH by means of the sedimentation balance.
Abstract: The particle-size distribution of illite and iron oxide-precipitated illite was examined as a function of pH by means of the sedimentation balance. Due to the precipitation of 5% iron oxides on the illite surfaces, aggregation occurred over a pH range of 3 to 10, and the degree of aggregation was greater for higher pH values. The aggregation was explained by the decrease of repulsion between face surfaces of illite due to the partial neutralization of the negative charge of illite surfaces, based on the electron micrographs and zeta potential measurement