Uptake of thorium ions from aqueous solutions by a molecular sieve (13X type) powder

The adsorption of thorium(IV) ions on molecular sieve (13X type) powder from aqueous solutions has been studied as a function of shaking time pH, thorium ion concentration and temperature. The conditions of maximum adsorption of thorium ions obeys Langmuir and D-R isotherms over the entire concentration range studied. Thermodynamic quantities such as H, G and S have been calculated fromK _D values determined at various temperatures. The results show endothermic heat of adsorption, but negative free energy value indicates that the process of thorium adsorption on molecular sieve powder is favored at high temperature. The influence of various cations and anions on thorium(IV) ion adsorption was examined. A wavelength dispersive X-ray fluorescence spectrometer was used for measuring the thorium ion concentration in solutions.     

π-Complexes as ligands in transition-metal compounds. Communication 7. Chromium π-arenecarbonyl complexes with azacymantrene as a two-electron ligand

Conclusions The previously unknown chromium -arenecarbonyl complexes containing -pyrrolylmanganesetricarbonyl as a two-electron ligand, C₆H₆Cr(CO)₂NC₄H₄Mn(CO)₃, Me₃C₆H₃Cr(CO)₂NC₄H₄Mn(CO)₃, and PhCOOMeCr(CO)₂NC₄H₄Mn(CO)₃, have been synthesized and characterized by spectroscopic methods.For Communication 6, see [6].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2780–2782, December, 1985.     

Ab initio Calculation of the Electronic Structure and Equilibrium Geometry of Cortisol and Its Derivatives

The molecular geometries of a series of steroid hormones including cortisol, 9-fluorocortisol, 6-fluorocortisol, and 9-chlorocortisol were optimized by 3-21G and 6-31G* ab initio calculations. The results of calculations on both levels are well consistent with each other and with the experiment. The conformational changes and electron density redistribution occurring in going from cortisol to its 6- and 9-halo derivatives were discussed. A conclusion was made that the O and F atoms can participate in hydrogen bonding with the corresponding structural groups of glucocorticoid receptors.     

Structure and Electrochemical Properties of Cation-Exchange Membranes Based on Partially Imidized Polyamidoacid

The transport of water molecules and the distribution of functional groups in polyamidoacid carboxyl-containing cation-exchange membranes based on pyromellitic acid are studied by NMR and ESR techniques. It is shown that the self-diffusion coefficients of water differ in the gel and intergel regions. Structural parameters of conducting channels in the gel regions are determined. In electrodialysis of one-component and binary solutions, polyamidoacid membranes possess higher transport numbers and separation coefficients of counterions that are less hydrated in solution.     

Barrier-discharge plasma treatment of surface water to remove organic compounds

Barrier-discharge plasma treatment of real surface water to remove organic pollutants was studied. Plasma treatment decreases the potential toxicity of snowmelt and rainfall runoff containing ammonium and chloride ions, oil products, phenols, and carboxylic acids (as recalculated for CH₃COOH).     

Selective liquid adsorption and structural properties of montmorillonite and its hexadecylpyridinium derivatives

Summary An X-ray diffraction method was used to study the structures of montmorillonites, the surfaces of which were covered to a systematically increasing extent with hexadecylpyridinium (HDP) cations. It was found that, depending on the degree of cover of the surface, the HDP cations form a mono- or bimolecular layer in the interlayer space. A detailed investigation was made of the selective sorption of binary mixtures on montmorillonite and on HDP-montmorillonites with different surface coverages. The adsorption excess isotherms were determined, as were the adsorption capacities from analysis of the isotherms, and also the equivalent specific surface areas.It was established that from benzene-n-heptane mixtures the benzene is adsorbed only on the external surface of montmorillonite, while in the case of organocomplexes it causes moderate disaggregation.From benzene, alcohols with different numbers of carbon atoms are also preferentially adsorbed on the internal surfaces of montmorillonite; with the rise in the number of carbon atoms, the extent of interlamellar adsorption decreases. In the case of HDP-montmorillonites in methanol-benzene mixtures, the adsorption capacity exhibits a monotonous increase with the degree of organopbility in the range under consideration. In the event of optimum organophility the disaggregation of the organocomplex is complete, and the equivalent specific surface area is 764-778 m² · g^–1. The swelling of the organocomplex, which can be characterized by X-ray diffraction measurement, is in close correlation with the interlamellar liquid adsorption. The results show modification of the surface of montmorillonite with HDP cations fundamentally determines the nature and extent of the selective liquid adsorption.

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Zusammenfassung Die Struktur von mit Hexadecyl-pyridinium(HDP)-Kationen im systematisch gesteigerten Maße bedeckten Montmorilloniten wurde mit der Röntgendiffraktions-Methode untersucht. Es wurde festgestellt, daß die HDP-Kationen, von der Bedeckung der Oberfläche abhängend, im Schichtzwischenraum eine mono- bzw. bimolekulare Schicht bilden. Die selektive Sorption binärer Gemische wurde an Montmorilloniten und an HDP-Montmorilloniten verschiedener Bedeckung eingehend untersucht. Es wurden die Adsorptionsisothermen von Flüssigkeitsgemischen und aus deren Analyse die Adsorptionskapazitäten und die äquivalenten spezifischen Oberflächen bestimmt.Es wurde festgestellt, daß aus Benzol-n-Heptan-Gemischen das Benzol nur an der äußeren Montmorillonite-Oberfläche adsorbiert wird, während es bei Organokomplexen eine mäßige Desaggregation verursacht. Die Adsorption von Alkoholen verschiedener Kohlenstoffzahl aus Benzol erscheint auch an inneren Montmorillonit-Oberflächen bevorzugt; mit zunehmender Kohlenstoffzahl nimmt das Ausmaß der interlamellaren Adsorption ab. Bei HDP-Montmorilloniten zeigt die Adsorptionskapazität aus Methanol-Benzol-Gemischen mit zunehmender Organophilität im untersuchten Gebiet eine monotone Steigerung. Im Falle optimaler Organophilität ist die Desaggregation vollständig, die äquivalente spezifische Oberfläche beträgt 764-778 m²/g. Die durch Röntgenn-diffraktionsmessung charakterisierbare Quellung des Organokomplexes steht mit der interlamellaren Flüssig-keitsadsorption in engern Zusammenhang. Unsere Ergebnisse zeigen, daß Charakter und Ausmaß der selektiven Flüssigkeitsadsorption durch die Modifizierung der Montmorillonit-Oberfläche mit HDP-Kationen grundlegend verändert wird.

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With 14 figures and 4 tables     

Polychlorierte Verbindungen und ihre Verwendung zur gas-chromatographischen Bestimmung von Elementen im ng-Bereich

Zusammenfassung Aus polychlorierten Kaliumxanthogenaten wurden verschiedene Metall-Chelate dargestellt, dünnschicht-chromatographisch getrennt und ihre R_f-Werte unter verschiedenen Trennbedingungen bestimmt.Anschließend wurden die einzelnen Komplexe gas-chromatographisch mit Elektroneneinfang-Detektoren untersucht. Über den durch augenblickliche thermische Zersetzung des Chelats in reproduzierbarer Menge anfallenden polychlorierten Alkohol konnten Metalle im ng-Bereich quantitativ indirekt bestimmt werden.

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Polychlorinated compounds and their use for the gas-chromatographic determination of elements in the ng-rangeI. Polychlorinated xanthates and their use for the determination of nickel

Ten chelates of polychlorinated xanthates were investigated by thin-layer chromatography. Their R_f-values were determined on silica gel and aluminium oxide for several different eluents. At 200° C the xanthates pyrolize momentarily and reproducibly to the corresponding alcohol, allowing the perchlorinated ligands to be utilized for the determination of metals by electron capture gas-chromatography.Combining thin-layer chromatography and the pyrolyzing technique nanogram amounts of mixtures of metals can be determined.

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Die Arbeit wurde in dankenswerter Weise von der Deutschen Forschungsgemeinschaft, Bad Godesberg, der Fazitstiftung, Gemeinnützige Verlagsgesellschaft m. b. H, Frankfurt a. M., und dem Verband der Chemischen Industrie e.V., Düsseldorf, unterstützt.     

Polynuclear nonfused bis(1,3,4-oxadiazole)-containing systems

Nonfused bis-1,3,4-oxadiazoles were synthesized by reaction of 5-substituted mono-and bis-tetrazoles with mono-and dicarboxylic acid chlorides. The results of kinetic studies showed that the transformation of tetrazoles into 1,3,4-oxadiazoles is accelerated by 1 to 2 orders of magnitude on addition of a catalytic amount of dimethylformamide, triethylamine, or pyridine.     

The effect of preparation procedure and composition of water-ethanol suspensions of amorphous silica on their aggregative stability and kinetics of coagulation

The method of flow ultramicroscopy is employed to study the effect of the composition and preparation procedure of dilute water-ethanol suspensions of two samples of amorphous silica (fractionated fused quartz and monodisperse amorphous silica) on the kinetics of their coagulation. It is revealed that all suspensions prepared by the addition of silica powders to water-ethanol mixtures with ethanol contents of 96 and 40 vol % are stable with respect to aggregation, as the suspensions prepared by the addition of aliquots of concentrated dispersions of the aforementioned silica samples in 96% ethanol aged for different time periods to water-ethanol mixtures containing 96 vol % ethanol. At a 40-vol % content of ethanol in the mixture, the coagulation whose character (including “superfast” coagulation) substantially depends on the time of aging of initial concentrated silica dispersions occurs. Furthermore, kinetic studies are performed for the coagulation of dilute silica suspensions prepared by the addition of silica powders to water-ethanol solutions containing 40 vol % of ethanol and traces (<1 ppm) of poly(ethoxysilane), poly(acrylic acid), and a supernatant prepared by the centrifugation of concentrated silica dispersion in 96% ethanol aged for more than 3 months. It is found that the addition of aliquots of the aforementioned ethanol solutions to silica suspensions in 40% ethanol, which are initially stable with respect to aggregation, causes their superfast coagulation.