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  • Author or Editor: S. Yariv x
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Abstract  

The formation of carnallite type double salts by grinding mixtures of hydrated magnesium halide and alkali halides with the same anions was investigated by X-ray diffraction, infrared spectroscopy and thermal analysis. Carnallite (KMgCl3·6H2O), cesium-carnallite (CsMgCl3·6H2O), bromo-carnallite (KMgBr3·6H2O) and cesium-bromo-carnallite (CsMgBr3·6H2O) were formed by grinding mixtures of MgCl2·6H2O with KCl or CsCl and MgBr2·6H2O with KBr or CsBr, respectively. Hydrated solid solutions of magnesium in potassium or cesium halides were obtained from that portion of potassium and cesium halides which did not take part in the formation of the double salt.

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Abstract  

DMSO-kaolinite complexes of low- and high-defect Georgia kaolinite (KGa-1 and KGa-2, respectively) were investigated by thermo-XRD-analysis. X-ray patterns showed that DMSO was intercalated in both kaolinites with a d(001)-value of 1.11 nm (type I complex). The samples were gradually heated up to 170°C and diffracted by X-ray at room-temperature. With the rise in temperature, due to the thermal evolution of the guest molecules, the relative intensity of the 1.11 nm peak decreased and that of the 0.72 nm peak (neat kaolinite) increased indicating that the fraction of the non-intercalated tactoids increased. The 1.11 peak disappeared at 130–140°C. During the thermal treatment of both complexes two additional peaks appeared at 110 and 120°C, respectively, with d-values of 0.79–0.94 and 0.61–0.67 nm in DMSO-KGa-1 and 0.81–0.86 and 0.62–0.66 nm in DMSO-KGa-2, indicating the formation of a new phase (type II complex). The new complex was obtained by the dehydration of type I complex and was composed of intercalated DMSO molecules which did not escape. The new peaks disappeared at 150–160°C indicating the complete escape of DMSO.

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Abstract  

Dimethylsulfoxide (DMSO) kaolinite complexes of low-and high-defect kaolinites were studied by thermo-IR-spectroscopy analysis. Samples were gradually heated up to 170°C, three hours at each temperature. After cooling to room temperature, they were pressed into KBr disks and their spectra were recorded. From the spectra two types of complexes were identified. In the spectrum of type I complex two bands were attributed to asymmetric and symmetric H-O-H stretching vibrations of intercalated water, bridging between DMSO and the clay-O-planes. As a result of H-bonds between intercalated water molecules and the O-planes, Si-O vibrations of the clay framework were perturbed, in the low-defect kaolinite more than in the high-defect. Type II complex was obtained by the thermal escape of the intercalated water. Consequently, the H-O-H bands were absent from the spectrum of type II complex and the Si-O bands were not perturbed. Type I complex was present up to 120°C whereas type II between 130 and 150°C. The presence of intercalated DMSO was proved from the appearance of methyl bands. These bands decreased with temperature due to the thermal evolution of DMSO but disappeared only in spectra of samples heated at 160°C. Intercalated DMSO was H-bonded to the inner-surface hydroxyls and vibrations associated with this group were perturbed. Due to the thermal evolution of DMSO the intensities of the perturbed bands decreased with the temperature. They disappeared at 160°C together with the methyl bands.

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Summary Thermo-XRD-analysis is applied to identify whether or not the adsorbed organic species penetrates into the interlayer space of the smectites mineral. In this technique an oriented smectite sample is gradually heated to temperatures above the irreversible dehydration of the clay, and after each thermal treatment is diffracted by X-ray at ambient conditions. In the thermal treatment of organo-clays, under air atmosphere at temperatures above 250°C, the organic matter is in part oxidized and charcoal is formed from the organic carbon. In inert atmosphere e.g. under vacuum above 250°C the organic matter is pyrolyzed and besides small molecules, charcoal is formed. If the adsorbed organic compound is located in the interlayer space, the charcoal is formed in that space, preventing the collapse of the clay. A basal spacing of above 1.12 nm suggests that during the adsorption the organic compound penetrated into the interlayer space. Thermo-XRD-analyses of montmorillonite complexes with anilines, fatty acids, alizarinate, protonated Congo red and of complexes of other smectites with acridine orange are described. To obtain information about spacings of the different tactoids that comprise the clay mixture, curve-fitting calculations on the X-ray diffractograms were adapted.

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Abstract  

The swelling properties of Al-pillared clays, obtained from five different smectites, were studied using X-ray diffraction. These clays, the dioctahedral beidellite and montmorillonite and the trioctahedral saponite, hectorite and laponite differ in source of isomorphic substitution and represent a series of decreasing basicity along the siloxane plane. An Al oxyhydroxy cation was inserted between the layers to form the respective pillared clays and these clays were heated incrementally to 600°C. The XRD peaks at each stage of heating were recorded as well as the same samples subsequently wetted. Basal spacings of each clay at each stage of dehydration ↭d rehydration indicated that the swelling of tetrahedrally substituted saponite and beidellite was indeed restricted, compared with the other three clays. This was attributed to greater basicity of the oxygen plane of beidellite and saponite due to tetrahedral substitution of Si by Al, resulting in an increase in the strength of hydrogen bonds between either water or the interlayer polyhydroxy cation and the clay. The data from the XRD analyses helped in addition, to clarify the thermal transformations of the Keggin ion itself. According to the changes in thed-spacings of the pillared clays it was concluded that the Keggin ion lost its structural water at ∼200°C and dehydroxylated in a range beginning at 350°C. Between 500 to 600°C this polymer cation, which is thought to form the Al2O3 oxide, did not rehydrate.

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Abstract  

Adsorption of the herbicide terbuthylazine by a soil from the Jezreel Valley was investigated by thermo-IR-spectroscopy. The adsorption took place mainly by the clay mineral montmorillonite. The adsorbed molecule was hydrogen bonded via the aniline groups to water molecules which were coordinated to the exchangeable metallic cations. When the sample was thermally treated at 115°C interlayer water was evolved, part of the herbicide decomposed and the other part became directly coordinated to the exchangeable metallic cations. The decomposition product contained a CO group.

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Abstract  

Li-, Na-, K-, Rb- and Cs-montmorillonites were saturated with benzidine, these organo-clay complexes heated under vacuum to 200°C and IR spectra recorded at various temperatures. Benzidine is mostly bound to interlayer cations through water molecules, except in Cs-clay where bonding to hydrophobic water and to water molecules which are hydrogen bonded to the oxygen plane predominates. During the thermal treatment water is lost and alkali, cations coordinate directly with benzidine. In Cs-, and to some extent also in Rb- and K-montmorillonite, benzidine is oxidized to semiquinone and quinoidal cation during the thermal treatment.

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Abstract  

Transition metal montmorillonites were saturated with benzidine (BEN) and heated gradually to 200°C, in a vacuum cell supported by KBr windows. IR spectra were recorded before and after the thermal treatment and at various temperatures during this treatment. X-ray diffractions were recorded before and after the thermal treatment. Hg clay shows properties similar to those of Mg and Ca clays. In the interlayer BEN is bound to Hg through a water molecule bridge, either by proton accepting (typeA) or by proton donation (typeB). Some BEN is also protonated (typeD). Initially typeA predominates, but after the thermal treatment, when the film is rehydrated, the amounts of typesB andD increase. With Mn-, Co-, Ni-, Zn- and Cd-montmorillonite a direct coordination of the benzidine by the dehydrated metallic cation is obtained (typeC), in addition to small amounts of typesA,B andD. During the thermal treatment water is evolved and associationsA andB are completely transformed toC. At elevated temperatures the following associations were identified in trace amounts, ammonium-amine, BEN bound to non-structured water, hydrophobic adsorbed BEN and BEN bound to the oxygen plane (typesE, F, H andJ, respectively). During the thermal treatment of Co and Cd clays some of the benzidine was oxidized, probably to semiquinone and quinoidal cation.

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