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Abstract  

Extraction chromatographic supports (XAD-7) impregnated with binary mixtures of cobalt dicarbollide and one of the two phosphororganic extractants (dibutyl-N,N-diethylcarbamoylmethyl phosphonate, DBDECMP, or octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide, (CMPO) were prepared using methanolic solutions of the extractants and subsequent evaporation of methanol at room temperature. The molar ratios (x) in isomolar series of the two extractants were 0, 0.25, 0.5, 0.75, and 1. The sorbents were used for investigating Eu capture from 0.1 and 1M HNO3 solutions under static conditions (24 hours shaking, 2 cm3 aqueous phase with 0.2 g sorbent, Eu initial concentrations 3·10–9, 0.0001, 0.001, 0.01 and 0.1M). The sorbents containing mixtures of extractants corresponding to the interpolated value x=0.45 (phosphororg./dicarb.) exhibited the highest values of the distribution ratios of Eu. A synergic effect of three orders of magnitude for low concentrations of Eu was observed. A tentative determination is given of the nature and the equilibrium constants of the chemical reactions assumed.

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Abstract  

Heat capacity and enthalpy increments of calcium niobates CaNb2O6 and Ca2Nb2O7 were measured by the relaxation time method (2–300 K), DSC (260–360 K) and drop calorimetry (669–1421 K). Temperature dependencies of the molar heat capacity in the form C pm=200.4+0.03432T−3.450·106/T 2 J K−1 mol−1 for CaNb2O6 and C pm=257.2+0.03621T−4.435·106/T 2 J K−1 mol−1 for Ca2Nb2O7 were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S m 0(CaNb2O6, 298.15 K)=167.3±0.9 J K−1 mol−1 and S m 0(Ca2Nb2O7, 298.15 K)=212.4±1.2 J K−1 mol−1, were evaluated from the low temperature heat capacity measurements. Standard enthalpies of formation at 298.15 K were derived using published values of Gibbs energy of formation and presented heat capacity and entropy data: Δf H 0(CaNb2O6, 298.15 K)= −2664.52 kJ molt-1 and Δf H 0(Ca2Nb2O7, 298.15 K)= −3346.91 kJ mol−1.

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Abstract  

Solvent extraction of several long-lived fission products from diluted nitric acid in pronounced synergistic systems involving dicarbollide and conformers of a specific thiacalix[n]arene were investigated using mainly chlorobenzene as the diluent. The following factors were experimentally investigated: molar ratio of the two extractants, total extractants concentration, aqueous acidity, nature of the mineral acid used, relative phase volumes, repeated extractions and metal concentration. Data are given on the rather slow kinetics of extraction and stripping, limited chemical stability of the extractants, selectivity and interference of foreign metals. The three different conformers of the basic compound with identical chemical composition exhibit very differing extraction properties. The plots of distribution ratios of all metals tested versus the varying concentration of one extractant keeping the concentration of the other extractant constant invariably exhibit maxima, interpreted as the result of an existence of several extracted species in the extract. Suggestions are given concerning possible practical applications of two of the conformers studied.

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Abstract  

Several calixarenes were tested with the aim to find a synergic solvent extraction system with dicarbollide suitable for the extraction of europium from nitric acidic solutions. The best results were obtained with C56H72O12S4 and chlorobenzene. Data on the selectivity and interferences by other nitrates are given. The effect of the concentrations of the extractants and aqueous nitric acid was investigated. Basic data on the kinetics of the extraction reaction are presented. Attempts are described to transform this extraction reaction into an adsorption chromatographic arrangement.

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Heat capacity and phonon spectra of A IIIN

Experiment and calculation

Journal of Thermal Analysis and Calorimetry
Authors:
D. Sedmidubský
,
J. Leitner
,
P. Svoboda
,
Z. Sofer
, and
J. Macháček

Abstract  

The low temperature heat capacities of three A IIInitrides, A III=Al, Ga and In, were measured by relaxation method in the temperature range 2–300 K and the corresponding entropies at the reference temperature 298.15 K were evaluated from the experimental data. The lattice heat capacity at constant volume was also assessed theoretically within harmonic crystal approximation by direct method using a combination of VASP software package to obtain the Hellmann-Feynman forces and the Phonon program to calculate the phonon spectra. The experimental data were analyzed by means of a Debye-Einstein model taking use of the calculated heat capacity and involving additionally an anharmonic contribution.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. Hampl
,
J. Leitner
,
K. Růžička
,
M. Straka
, and
P. Svoboda

Abstract

The heat capacity and the heat content of bismuth niobate BiNb5O14 were measured by the relaxation time method, DSC and drop method, respectively. The temperature dependence of heat capacity in the form C pm=455.84+0.06016T–7.7342·106/T 2 (J K−1mol−1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S m=397.17 J K−1mol−1 was derived from the low temperature heat capacity measurement.

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Journal of Thermal Analysis and Calorimetry
Authors:
J. Leitner
,
M. Hampl
,
K. Růžička
,
M. Straka
,
D. Sedmidubský
, and
P. Svoboda

Abstract  

The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature dependence of the molar heat capacity in the form C pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T 2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S m 0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf H 0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional theory.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Krivopustov
,
A. Pavliouk
,
A. Kovalenko
,
I. Mariin
,
A. Elishev
,
J. Adam
,
A. Kovalik
,
Yu. Batusov
,
V. Kalinnikov
,
V. Brudanin
,
P. Chaloun
,
V. Tsoupko-Sitnikov
,
A. Solnyshkin
,
V. Stegailov
,
Sh. Gerbish
,
O. Svoboda
,
Z. Dubnicka
,
M. Kala
,
M. Kloc
,
A. Krasa
,
A. Kugler
,
M. Majerle
,
V. Wagner
,
R. Brandt
,
W. Westmeier
,
H. Robotham
,
K. Siemon
,
M. Bielewicz
,
S. Kilim
,
M. Szuta
,
E. Strugalska-Gola
,
A. Wojeciechowski
,
S. Hashemi-Nezhad
,
M. Manolopoulou
,
M. Fragopolou
,
S. Stoulos
,
M. Zamani-Valasiadou
,
S. Jokic
,
K. Katovsky
,
O. Schastny
,
I. Zhuk
,
A. Potapenko
,
A. Safronova
,
Zh. Lukashevich
,
V. Voronko
,
V. Sotnikov
,
V. Sidorenko
,
W. Ensinger
,
H. Severin
,
S. Batsev
,
L. Kostov
,
Kh. Protokhristov
,
Ch. Stoyanov
,
O. Yordanov
,
P. Zhivkov
,
A. Kumar
,
M. Sharma
,
A. Khilmanovich
,
B. Marcinkevich
,
S. Korneev
,
Ts. Damdinsuren
,
Ts. Togoo
, and
H. Kumawat

Abstract  

An extended U/Pb-assembly was irradiated with an extracted beam of 2.52 GeV deuterons from the Nuclotron accelerator of the Laboratory of High Energies within the JINR in Dubna, Russia. The lay-out of this experiment and first results are reported. The Pb-target (diameter 8.4 cm, length 45.6 cm) is surrounded by a natU-blanket (206.4 kg) and used for transmutation studies of hermetically sealed radioactive samples of 129I, 237Np, 238Pu and 239Pu. Estimates of transmutation rates were obtained as result of measurements of gamma-activities of the samples. Information about the spatial and energy distribution of neutrons in the volume of the lead target and the uranium blanket was obtained with sets of activation threshold detectors (Al, Y and Au) and solid state nuclear track detectors (SSNTD). An electronic 3He neutron detector was tested on-line. A comparison of experimental data with theoretical model calculations using the MCNPX program was performed yielding satisfactory results.

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