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.
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.
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.
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.
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.
The adsorption of the organic anionic dye Congo red (CR) by montmorillonite saturated with Na+, Cs+, Mg2+, Cu2+, Al3+ and Fe3+ was investigated by XRD of unwashed and washed samples after equilibration at 40% humidity and after heating at 360 and at 420°C. The clay was treated with different amounts of CR, most of which was adsorbed. Clay samples, untreated with CR, after heating showed collapsed interlayer space. Unwashed and washed samples, which contained CR, before heating were characterized by three peaks or shoulders, labeled A (at 0.96-0.99 nm, collapsed interlayers), B (at 1.24-1.36 nm) and C (at 2.10-2.50 nm). Peak B represents adsorbed monolayers of water and dye anions inside the interlayer spaces. Peak C represents interlayer spaces with different orientations of the adsorbed water and organic matter. Diffractograms of samples with small amounts of dye were similar to those without dye showing peak B whereas diffractograms of most samples with high amounts of dye showed an additional peak C. Heated unwashed and washed samples were also characterized by three peaks or shoulders, labeled A' (at 0.96 nm), B' (at 1.10-1.33 nm) and C' (at 1.61-2.10 nm), representing collapsed interlayers, and interlayers with charcoal composed of monolayers or multilayers of carbon. When the samples were heated from 360 to 420°C some of the charcoal monolayers underwent rearrangement to multilayers. In the case of Cu the charcoal decomposed and oxidized. The present results show that most of the adsorbed dye was located inside the interlayer space.
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.
An intense blue organo-clay color pigment was obtained by adding naphthyl-1-ammonium chloride to a Na-montmorillonite aqueous
suspension followed by treatment with sodium nitrite. This treatment resulted in the synthesis of the azo dye 4-(1-naphthylazo)-1-naphthylamine
adsorbed onto the clay. The pigment was subjected to thermo-XRD-analysis and the diffractograms were curve-fitted. Heating
naphthylammonium-montmorillonite at 360°C resulted in the evolution of the amine at temperatures lower than those required
for the formation of charcoal and consequently the clay collapsed. On the other hand, heating the pigment at 360°C resulted
in the conversion of the adsorbed azo dye into charcoal. The clay did not collapse, thus proving that the azo dye was located
inside the interlayer space. Before the thermal treatment a short basal spacing in the pigment compared with that in the ammonium
clay (1.28 and 1.35 nm, respectively) indicated stronger surface π interactions between the clayey O-plane and the azo dye
than between this plane and naphthylammonium cation. The amount of dye after one aging-day of the synthesis-suspension increased
with [NaNO2]/[C10H7NH3] ratio but did not increase with naphthylammonium when the [NaNO2]/[C10H7NH3] ratio remained 1. After 7 and 56 aging days it decreased, indicating that some of the dye decomposed during aging.