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- Author or Editor: H. Aly x
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Abstract
The kinetics of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone (HTTA) and triphenylarsine oxide (Ph3AsO) mixture in chloroform and aqueous nitrate medium has been investigated using a stirred Lewis cell at ionic strength of 0.1M. The effect of the concentration of HTTA, Ph3AsO, H+ and NO
3
–
on the rate of distribution of Am(III) and Eu(III) was studied. The results were interpreted by reaction mechanisms where the rate-determining steps are the parallel reactions of Am(OH)2+ or Eu(OH)2+ with one HTTA molecule and one Ph3AsO molecule in the aqueous medium. The values at 25 °C of the rate constantk
HLL
(HL=HTTA andL
=Ph3AsO) are 1.6±0.3·106M–2·s–1 and 2.3±±0.3·108M–2·s–1 for Am(III) and Eu(III), respectively.
Abstract
Humin is separated from a soil sample and characterized by elemental analysis, IR and potentiometric titration. These investigations indicated that humin displayed similar characteristics as humic acid. The sorption behavior of137Cs,90Sr and153Gd with humin was investigated from aqueous solution. The results indicated that the sorption process follows the order: Gd3+≫Sr2+>Cs+. It was time dependent and increased with pH. The sorption in the presence of humic acid or EDTA showed that both form a metal-ligand complex and consequently decrease the % uptake.
Abstract
The removal efficiency of moderate levels of radon from groundwater supplies was evaluated using the diffused bubble aeration technique. An aeration system was designed, constructed and operated for that purpose. The effect of air-to-water ratio and detention time on radon removal were evaluated through 32 runs. The possibility to reduce the radon activity in the influent stream to the U.S. Environmental Protection Agency proposed maximum contaminant level (MCL) was verified through many alternative combined values of both air-to-water ratios and detention times. The results showed that at detention time of 19 minutes and air-to-water ratio of 12, the average radon removal is about 97%. The stripping constant characterizing this system was calculated and the removal efficiency at extended values of detention time was predicted. The data obtained are site specific, being dependent on container size, type of diffusers, temperature, and influent radon radioactivity.
Abstract
Tin(IV) antimonate (SnSb), cerium(IV) antimonate (CeSb), silicon(IV) antimonate(SiSb) ant titanium(IV) antimonate (TiSb) were prepared under various conditions. The ion-exchange properties and the thermal stability of these materials were examined in order to elucidate their applicability to the processing of radioactive liquid wastes. Capacity, equilibrium measurements, adsorption isotherms and the selectivity patterns for Cs+, Sr2+, Co2+ and Eu3+ ions on these sorbents at different conditions were determined. The effect of high concentrations of salts and complexing agent as interfering ions in the feed solutions on the distribution coefficient of the metals, mentioned above, was tested as a function of [HNO3]. Based on the results obtained, practical separation experiments on column were performed.
Abstract
The thermodynamic functions for the extraction of Sc3+ by liquid cation exchangers HD and HDEHP are determined radiometrically by the temperature coefficient method. The role of diluent dielectric constant on the extraction of Sc3+ by HD is also studied. The thermodynamic parameters determined indicated that the free energy variation for the extraction of Sc3+ by HD is mainly determined by the entropic terms arising from the hydration—dehydration process of the exchanged ions. In the case of HDEHP as extractant, the free energy variations are determined mainly by the entalpic terms of the system.
Abstract
A new route has been developed for the micro-determination of227Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of228Th, the β-decay product of the 6.1 hrs228Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10−17 g227Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.
Abstract
Iron(III) (FeTi) and chromium (III) titanates (CrTi) were prepared as cation exchange materials in a granular form. The rate of the isotopic exchange of Na+/*Na+ and Zn2+/*Zn2+ between aqueous solution and iron(III) and chromium(III) titanates in Na+ or Zn2+form has been carried out radiometrically in the 25-60 °C temperature range. The exchange rate is controlled by a particle diffusion mechanism and experimental and theoretical approaches have been used to obtain the rate of diffusion through the spherical particles of the exchangers. The values of self diffusion () of Na+ and Zn2+ ions were measured at different operation conditions, particle size, reaction temperatures and drying temperatures of the matrix. The values of kinetic and thermodynamic parameters were calculated and their significance discussed.
Abstract
Sorption of Na(I), Cs(I) and Co(II) radionuclides from aqueous solutions by titanosilicate have been investigated. The time dependent studies for metal ions showed relatively rapid sorption kinetics between 5 and 30 min to reach equilibrium. A batch adsorption model based on assumption of the pseudo-second-order mechanism was applied to predict the sorption rate, while the equilibrium capacity was calculated at different temperatures. The adsorption of different radionuclides onto titanosilicate was found to be favored at high ions concentrations and low temperature for Na+ and Co2+ while at high temperature for Cs+. Activation energy of adsorption was computed to be 2.35, 24.11 and 5.74 kJ/mol for adsorption of Na(I), Cs(I) and Co(II), respectively. The results revealed that the adsorption of Cs+ is the highest relative to Na+ and Co2+ at different conditions which may be attributed to its low hydration energy. Further, the equilibrium isotherm for the interested ions was analyzed and it was found to obey Frundlich equation.
Abstract
The electrical conductivity of pure and Co-doped MgAl2O4 spinels was measured at 700–1100 K. The results of both pure and doped spinels were found to be fitted with an exponential expression with two different activation-energy parameters, in two ranges of temperature. The effect of 
-irradiation on the electrical conductivity of pure and doped spinels was also studied. The kinetic parameters of the isothermal annealing of the induced irradiation damages in the spinels were determined. All the results were found to be consistent with the ionic conduction which was suggested to be due to the motion of the cation vacancy.
Abstract
The extraction of U(IV) from phosphoric acid by octylphenyl acid phosphate (OPAP) in kerosene was investigated. Parameters affecting the extraction of U(IV) from phosphoric acid were investigated. The effects of H3PO4, H2SO4, H2O2, Na2CO3 and (NH4)2CO3 concentrations, phase ratio and temperature on the stripping of uranium from the organic phase were studied. Based on the bench-scale results, a continuous counter-current extraction flow sheet was developed and tested using a 16-stage horizontal type mixer settler. The continuous extraction scrubbing stripping showed that the extraction efficiency of the developed process is 99%, whereas the stripping efficiency is 97%.
