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Abstract  

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.

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Abstract  

Sorption of macroamounts of the technetium thiourea complex cation by a cation exchange resin was studied in HNO3 and HClO4 solutions as a function of the concentration and reaction time for pertechnetate with thiourea. The distribution ratio reaches the value of 103 and may be even higher (>104) when sorption proceeds from a solution of the solid complex in dilute perchloric acid. The complex cation is extracted from 0.25–1M HNO3 with solutions of the bis(1,2-dicarbollyl)cobalt(III) anion in nitrobenzene—chloroform (1:1), log D=2.75−2.95 being obtained. The preconcentration and separation of technetium on cation exchangers from dilute mineral acids would seem to be one field of application.

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Abstract  

The specific phenomena accompanying the daughter nuclide formation by radioactive β-decay of complex parent compounds cause certain deviations from a thermodynamic distribution of daughter elements in separation procedures (e.g. in radionuclidic generators) and they are shown to complicate or, less probably, simplify their separation. A simple kinetic model has been proposed to explain such processes as the distribution of some daughter nuclides of fission products by solvent extraction with chelating compounds (systems of99Mo−99mTc and144Ce−144Pr with oxines).

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Abstract  

Various double emulsion systems with liquid membranes containing tri-n-octylphosphine oxide /TOPO/, tri-n-butylphosphate /TBP/, KELEX 100® and di-2-ethylhexylphosphoric acid /DEHPA/, as carriers for uranium/VI/ pertraction, were studied. The conditions were found at which the systems are most efficient, comparing with solvent extraction. The use of DEHPA as a membrane carrier with solutions of H2SO4 and H3PO4 encapsulated in the membrane was substanfiated.

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Abstract  

The sorption of copper on synthetic hydroxyapatite was investigated using a batch method and radiotracer technique. The hydroxyapatite sample prepared by a wet precipitation process was of high crystallinity with Ca/P ratio of 1.688. The sorption of copper on hydroxyapatite was pH independent ranging from 4 to 6 as a result of buffering properties of hydroxyapatite. The adsorption of copper was rapid and the percentage of Cu sorption was >98% during the first 15–30 min of the contact time. The experimental data for sorption of copper have been interpreted in the term of Langmuir isotherm. The sorption of Cu2+ ions was performed by ion-exchange with Ca2+ cations on the crystal surface of hydroxyapatite under experimental conditions. The competition effect of Zn2+, Fe2+ and Pb2+ towards Cu2+ sorption was stronger than that of Co2+, Ni2+ and Ca2+ ions. The ability of the bivalent cations to depress the sorption of copper on hydroxyapatite was in the following order Pb2+ > Fe2+ > Zn2+ > Co2+ ≈ Ni2+.

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Abstract  

Inorganic sorbents are often used in separation of metals and radionuclides in radioanalytical application and they were also used in technological scale for separation of radionuclides in cleanup of Three Mile Island NPP. Inorganic sorbents become popular in the last years because no problem with organic contamination, there are stable against radiation, sorption efficiency can be tailor made for selective separation of chosen metal. Contrary to the organic sorbents they have usually lower capacity and chemical stability is limited to narrower pH. Nevertheless of some problems, many good properties of inorganic sorbents make them very attractive for sorption study.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Paulenová, P. Rajec, M. Žemberyová, G. Sasköiová, and V. Višacký

Abstract  

The binding of strontium by humic acid was studied in systems designed to model soil leaching conditions. Ultrafiltration experiments were conducted for a wide range of CaCl and NaCl concentrations and for the pH range 4 to 7. It was found that the recovery of humic acid slowly decreased with increasing pH. This occurred because at neutral and basic solutions the increasing degree of ionization of the carboxylate groups leads to the full repulsion state of the humic acid and to increasing of the strontium binding (strontium recovery 60% at pH 7) with this natural polyelectrolyte. The strontium complexation in the presence of calcium was studied in different series of metal concentrations at pH 5 and the ionic strength 0.1M NaCl. The results were explained on the base of the metal ion charge neutralization model of humic complexation (CNM). Loading capacity (cca 40%) and complexation constants and Sr (3.51±0.27) and Ca (3.10±0.29) with Aldrich humic acid were found.

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Abstract  

Slovak bentonites characterized by good rheological, mineralogical and chemical stability are considered as suitable sealing barriers for construction of Slovak deep geological repository for high-level radioactive waste and spent nuclear fuel. There is several Slovak bentonite deposits, bentonites of which have appropriate adsorption properties meeting the geotechnical requirements for this type of barriers. Study of adsorption properties of bentonites (mainly smectites) is an essential step for developing the migration model long-lived corrosion and activation products, and fission products of uranium. Nuclear wastes contain the most important nuclear fission products, β-emitter 90Sr with long half-life, biological half-life and high mobility. The present paper investigates and compares the strontium adsorption properties of bentonites of different mineral composition consisted mainly of dioctahedral and trioctahedral smectites.

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Abstract  

Pure HEU-type zeolite (heulandite) crystals were allowed to interact with Sr2+ cations in aqueous solution. The powdered solid experimental products obtained from batch-type sorption experiments, using solutions of Sr2+-concentrations between 10 and 1000 mg/l, were investigated using INAA, RI-XRF and SEM-EDS. The Sr uptake by the mineral which can adequately be described with a Freundlich-type isotherm, varies from 3.14 to 6.22 mg/g. The distribution coefficients increase progressively by decreasing the solutions concentration reaching a value of 1800 ml/g. The investigated zeolite interacts with Sr2+ cations through ion exchange reactions and initial exchangeable Ca2+ cations are replaced into the structural micropores. However, in the best case, only ca. 43% of the theoretical CEC can be covered because of the limited availability of the extra framework Ca2+ cations that can be removed from the lattice under ambient treatment conditions. The XPS investigation of Sr-loaded single crystals indicated that adsorption of Sr2+ cations on the outer surface also occurs while surface precipitation phenomena must be excluded. Similar surface analyses by means of12C-RBS showed that the Sr depth-distribution at near-surface layers is quite homogenous in contrast to a previous relevant study revealing an intense surface Sr-accumulation on a natural Ca-zeolite of different structural characteristics (scolecite).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Paulenová, P. Rajec, J. Kandráč, G. Sasköiová, E. Tóthová, P. Bartoš, V. Švec, and R. Góra

Abstract  

Complexation equilibrium of metals by three humic acids of different origin with ultrafiltration method was investigated at pH 4 a 5 and ionic strength I = 0.1M NaClO4. Commercial (Aldrich) and two original humic acids (peat and soil, obtained by six step isolation process from the material from Trnava county, close to the NPP Jaslovské Bohunice) were used in this study. For the evaluation of the results, the model of metal ion charge neutralization upon humic acid functional group proposed by the Kim and Czerwinski was used. Complexation constants were calculated using the terms of this model (operational concentration, loading capacity). The values of log = 5.39±0.16 for yttrium, 6.15±0.16 for americium and 5.20±0.08 for lead were found. Correlation of free metal concentration and ratio of molar fraction of complexing functional groups confirms the validity of charge neutralisation model for metal and polyelectrolyte complexation study.

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