Standard Gibbs energies of transfer of cesium ion from water to nitrobenzene and nitrobenzene-carbon tetrachloride mixture have been evaluated from electrochemical measurements. From the results the conclusion can be drawn that with increasing dielectric permitivity of organic mixed solvents the value of the Gibbs transfer energy of Cs+ ion decreases.
Authors:V. Mikulaj, P. Rajec, A. Švec, N. Cuong, and V. Ahn
A continuous extraction device for preconcentration of metals with light phase internal recycle has been developed. This system was used for preconcentration of cobalt and uranium from 20–30 dm3 samples with 10.8 dm3/hours feed rate. The emulsion membranes were created of surfactants and LIX 64 N (for cobalt) or di-2ethylhexyl-phosphoric acid (for uranium) as a carrier to control stability and permeability for long time periods. The results from continuous extraction of cobalt and uranium using the device constructed have shown the possibility to reach 100–200-fold preconcentration of metals with high yield (min. 92%).
Authors:F. Macášek, R. Kopunec, V. Mikulaj, P. Rajec, and A. Švec
Membrane extraction is treated as an analogue of solvent extraction in three-phase distribution systems. Its advantages and drawbacks are discussed with respect to separation and preconcentration of radionuclides, fission products of uranium and uranium itself.
Authors:M. Sahoo, J. Kuruc, A. Švec, R. Čech, and M. Hutta
Radiolytic products of the two-phase systems of nitrobenzene-carbon tetrachloride-water mixtures have been identified using HPLC adsorption chromatography on SEPARON SIX silica gel column under an elution gradient from n-hexane to ethyl acetate. That the product formation is a function of the mixture composition is indicated by the chromatograms. Para-nitrophenol constitutes one of the major radiolytic products in the system where the volume ratio of nitrobenzene is more than that of carbon tetrachloride and its radiation yield is dependent on the volume ratio of the aqueous phase.
Authors:V. Mikulaj, P. Rajec, A. Švec, and J. Macková
Transport of strontium through supported hollow fiber dichlorobenzene liquid membranes has been studied. The possible mechanism of strontium transport with 18-crown-6 ether as a carrier and picrate as co-counter-ion as well as the construction of a pertraction device with on-line radiometric detection of strontium using85Sr tracer is described. Preliminary results of strontium pertraction in a recycling and one-pass mode with different concentrations of crown are shown.
Authors:D. Kaniansky, P. Rajec, P. Havaši, A. Švec, and F. Macášek
The use of isotope dilution technique to eliminate problems associated with demands for a high load capacity in column-coupling capillary isotachophoresis was studied. Determinations of phosphate present in a model mixture and in white wine served for the evaluation of this approach to quantitative analysis in isotachophoresis. A high selectivity of the analysis with acceptable accuracy and precision of the determination also in complex ionic mixtures in a short time are obvious advantages of this approach.
Authors:D. Kaniansky, P. Rajec, A. Švec, J. Marák, M. Kovaľ, M. Lúčka, Š. Franko, and G. Sabanoš
An on-column radiometric detector for capillary isotachophoresis is described. Design of the detector follows its intended use, i.e., mainly the detection of14C labelled ionogenic compounds separable by this electromigration method. A key part of the detector is a small volume (70 or 200 nl) cell with the sensing part made of plastic scintillator with counting efficiencies of 13–15%. An equation correlating the precision of radioactivity measurements with physical and geometrical characteristics of the cell and isotachophoretic conditions has been derived providing a guide in optimizing both the geometrical dimensions of the cell and the isotachophoretic working conditions. A minimum detectability calculated for14C radionuclide (21 Bq for a 3 mm thickness of the sensing part of the cell) was in a good agreement with the value determined experimentally (16 Bq). Other parameters evaluated experimentally include resolving power, short- and long-term reproducibilities of the response. It was also shown that optimized driving current during the detection enables to improve the precision of the radioactivity measurement.
Authors:Ľ. Mátel, P. Rajec, V. Mikulaj, A. Švec, O. Rosskopfová, and L. Drahošová
Specific activity of239,240Pu in contaminated soils from the bank of Manivier channel was determined to be in the range of 5–40 Bq·kg–1 and for soils from the bank of Dudvah river 0.6–8 Bq·kg–1. The ratio of239,240Pu/137Cs found in the samples is about 1·10–4, which is very close to the ratio found in the pulp of high activity concentrate in the collecting tank of nuclear power plants (NPP).
Authors:F. Macášek, V. Mikulaj, P. Rajec, R. Čech, L. Mátel, R. Kopunec, J. Kuruc, and A. Švec
Radiolytical decomposition of phenol was investigated at60Co gamma irradiation (1–2 Gy·s–1, 10 kGy) of pre- and continuously aerated aqueous solutions at concentrations of phenol 1–100 mg· ·dm–3 and in the presence of sodium hydroxide, sulphuric acid, sodium and ferrous sulphate, formaldehyde, 2-propanol,n-hexane, xylene, benzene, and commercial gasoline. From the decomposition rate at doses 50–400 Gy, a phenomenological model of linear relation between the dose acquired for 37% decomposition (D37), initial concentration (g·m–3) of phenol (p0) and of an admixture (s0) was confirmed in the formD37=52ftr(p0+feqs0), wheref's are constants which can be attributed to the relative transformation resistance of phenol towards the OH radicals in given matrix (ftr, for pure waterftr=1) and relative acceptor capacity of competing substrate (feq). In real wastewaters, the efficient decrease of phenols content may be substantially lower than that in model solutions, obviously due to radiation oxidation of aromates, as proved by irradiation of aqueous solutions of benzene. Technical and economical feasibility of the process is discussed.