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- Author or Editor: I. Lapides x
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Abstract
The equation for calculation of the activation energy of the diffusion of the evolved products through the matrix (E) from a single TG curve were proposed by solving Fick's laws. The solution is based on the similarly theory by utilizing a Fourier number. The proposed method was examined by using mass loss data for the dehydroxylation of some micas with and without FeO (muscovite and its varieties and lepidolite) as determined from their TG curves. TheE values for the first stage of the dehydroxylation of these micas areE 1,=85±10 kJ mol−1; for the final stageE 2=380±40 kJ mol−1 and for the mass loss connected with fluorineE F=85±10 kJ mol−1.
Abstract
Several isomorphic groups of micas: Muscovite-Phengite-Muscovite-Li-Muscovite; Biotite-Zinnwaldite-Lepidolite and Biotite-Phlogopite were investigated by DTA, TG and DTG. Octehedral vacancies and the sites of octahedral cationic occupancy were determined from IR-spectra of the hydroxyls. The influence of a composition and fine structure of the micas on the shape of the thermal curves was discussed. A one to one correspondence between the isomorphic series members and individual thermal curves makes it possible to determine the chemical composition of a mica sample. The combination of thermal and IR-spectra of hydroxyl analyses permits to link the Order-Disorder data with thermal properties of mica.
The use of thermo-XRD-analysis in the study of organo-smectite complexes
Robert Mackenzie memorial lecture
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.
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.
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.
Abstract
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.
Summary
Co- and Ni-montmorillonites adsorb in aqueous suspensions up to 13 mmol alizarinate per 100 g clay, onto the broken-bonds whereas Cu-clay adsorbs up to 25 mmol dye per 100 g clay into the interlayer space. Unloaded Co-, Ni- and Cu-clays and samples loaded with increasing amounts of alizarinate, were gradually heated in air to 360C and analyzed by X-ray diffraction. All diffractograms were curve-fitted. Fitted diffractograms of non-heated samples, showed two peak components labeled C and D, at1.22 and1.32 nm, characterizing tactoids with mono- and non-complete bilayers of water, respectively. After heating at 120C component D decreased or disappeared and two new components A and B appeared at0.99 and1.08 nm, representing collapsed tactoids and tactoids with interlamellar oxy-cations, respectively. At 250C, C and D decreased or disappeared but A and B appeared in all fitted diffractograms. Co- and Ni-clay after heating at 360C did not show C and D. Components A and B proved that these clays collapsed indicating that initially there was no alizarinate in the interlayers. At 360C, C and D persisted in the fitted-diffractograms of Cu-clay, representing tactoids with interlamellar charcoal formed from the partial oxidation of adsorbed dye initially located in the interlayers.
Synthesis and thermo-XRD-analysis of the organo-clay color pigment
Naphthylazonaphthylamine-montmorillonite
Abstract
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.
Abstract
Montmorillonite (M) saturated with H+,Li+,Na+,K+,Rb+,Cs+,NH4 +,Mg2+,Ca2+,Sr2+,Ba2+,Mn2+,Co2+,Cu2+,Al3+ and Fe3+ were dry-ground with urea (U) in mass ratios U/M between 0.1 and 2.0 in an agate mortar and diffracted by X-ray. Extensive swellings occurred with H-, Li-, Na-, di-and trivalent cation-clays, suggesting the formation of urea-montmorillonite intercalation complexes. Mechanochemically treated samples were heated at different temperatures up to 375°C. The rise in temperature was accompanied by a decrease in the basal spacing. There was a correlation between the results of the thermo-XRD-analysis and the fine structures of the urea-montmorillonite complexes described in the literature. Five stages in the basal spacing vs. temperature curves were identified. In the first stage (at 150°C) the decrease was due to dehydration. In the second stage (175°C) this dehydration was accompanied by some thermal intercalation of excess urea. The other stages (at 225, 325 and 375°C) were associated with the degradation of urea and the condensation of the degraded species to polymeric products. At 375°C Li-, Na-, K-NH4-, Mh-, Co- and Cu-montmorillonite collapsed, indicating that urea was evolved. The other urea-clay complexes did not collapse due to intercalated polymers formed by the degradation products of urea.
Abstract
The mechanochemical solid-state adsorption of the cationic dye crystal violet (CV) by montmorillonite was investigated by XRD and simultaneous DTA-TG. Solid CV was ground with the clay for 5 min and four different varieties of CV mechanochemically treated clay were investigated. X-ray and DTA data were compared with those of CV-montmorillonite obtained from an aqueous suspension. X-ray and DTA studies of a ground mixture and a ground mixture heated at 110°C suggest that the mechanochemical adsorption of organic cations takes place on the external surfaces of the clay. The study of a ground mixture washed with water, and washed with water and acetone reveal that water is essential for the penetration of CV into the interlayer space.
