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Abstract  

The complex formation of Eu(III) by bicarbonate/carbonate ions has been studied at 0.1 M ionic strength and 25°C using synergistic solvent extraction system of 1-nitroso-2-naphthol and 1,10-phenanthroline in chloroform. Concentrations of bicarbonate (5·10–3 to 1·10–1 M) and carbonate (5·10–4 to 1·10–2 M) ions in the aqueous phase have been varied in the pH range of 8.0 to 9.1 to simulate ground and natural water compositions. Under these conditions, the following species have been identified: Eu(HCO3)2+, Eu(HCO3)2 +, Eu(CO3)+ and Eu(CO3)2 . Their conditional formation constants (log ) have been calculated as 4.77, 6.74, 6.92 and 10.42, respectively. These values suggest that the carbonate complexes of Eu(III) are highly stable.

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The adsorption of Eu(III) on multiwalled carbon nanotubes (MWCNTs) as a function of pH, ionic strength and solid contents are studied by batch technique. The results indicate that the adsorption of Eu(III) on MWCNTs is strongly dependent on pH values, dependent on ionic strength at low pH values and independent of ionic strength at high pH values. Strong surface complexation and ion exchange contribute to the adsorption of Eu(III) on MWCNTs at low pH values, whereas surface complexation and surface precipitation are the main adsorption mechanism of Eu(III) on MWCNTs. The desorption of adsorbed Eu(III) from MWCNTs by adding HCl is also studied and the recycling use of MWCNTs in the removal of Eu(III) is investigated after the desorption of Eu(III) at low pH values. The results indicate that adsorbed Eu(III) can be easily desorbed from MWCNTs at low pH values, and MWCNTs can be repeatedly used to remove Eu(III) from aqueous solutions. MWCNTs are suitable material in the preconcentration and solidification of radionuclides from large volumes of aqueous solutions in nuclear waste management.

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Abstract  

The absorption effect of 5% w/w non-proliferative cell suspensions of Mycobacterium smegmatis on labelled solutions of Eu3+ ions, both alone and in admixtures with Am3+, Co2+ and Cs+, was studied at pH 1.0 as a function of time and cationic concentration. For 10 M concentrations of Eu, Co and Cs, selective adsorption of the trivalent lanthanide and actinide ions was practically quantitative after 90 min; no significant adsorption was observed for cobalt and cesium ions. Column adsorption measurements with the mycobacterial biomass showed that desorption of the M3+ ions did not occur at less than 2M HCl and remained incomplete even at higher acidities.

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Abstract  

The extraction of Am3+ and Eu3+ from aqueous picric acid solution by N, N-dinaphthyl-N, N-diphenyl-3,6-dioxaoctanediamide (LI) and 1, 1-(3, 6, 9-trioxaundecanedionyl)diphenothiazine (LII) was investigated by a radioactive tracer technique. Extraction distribution ratios of Am3+ and Eu3+ have been measured as a function of pH, picric acid concentration, extractant concentration, diluent and temperature. The extraction of Am3+ is preferred to that of Eu3+ for both LI and LII, and the latter gives larger separation factor than the former. The equilibrium constants and thermodynamic parameters of extraction reactions were also calculated.

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Abstract  

Distribution of Hg2+, Co2+, Sc3+ and Eu3+ between the cation exchanger Dowex-50X8, [H+] (100–200 mesh), and 1M HNO3 solution containing different benzylamine (BA) concentrations has been studied. The distribution coefficient, D, for Co2+, Sc3+ and Eu3+ is very small and does not vary seriously with the BA concentration. It is also found that Hg2+ is highly taken by the resin from the media studied. In this respect, D increases with increasing BA concentration to reach a maximum at 0.5% BA in 1M HNO3. This behaviour is explained by the exchange of molecular species between the cation exchanger and the aqueous phase. Based on the results, a radiochemical separation procedure for the selective isolation of Hg2+ from Co2+, Sc3+ and Eu3+ has been developed. The radiochemical purity is not less than 99.8% and the chemical yield more than 95% for the separated203Hg.

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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  

Sorption of124Sb(III) from benzene, toluene, o-xylene and nitrobenzene on treated fly ash, pyrolysis residue and bentonite clay was studied at room temperature using the batch method. In comparison to a former study for the sorption of124Sb(V), the results revealed relatively higher sorption of the trivalent state than the pentavalent one. According to the type of the nonpolar solvent used, the order of uptake of the radioactive isotopes was often o-xylenetoluene>benzene. The sorption tendency of the sorbents used towards the radionuclides was: bentonitepyrolysis residue>treated fly ash. Sorption from an aqueous medium on the same sorbents has also been investigated for124Sb(III) compared to124Sb(V),152Eu(III) and their mixtures. The obtained results showed that the order of uptake of the different radionuclides was: Eu(III)>>Sb(III)>Sb(V)>mixture. The investigation was extended to the desorption studies of these radionuclides in the acidic and the neutral media from the dried radioactivity loaded sorbents.

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Abstract  

The octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), loaded as stationary phase on silica, has been used for the sorption of Eu and actinides from acidic aqueous solution. Different commerical solid support were investigated and, finally SiO2 was chosen. Experiments were performed to obtain basic data on actinide removal. Distribution coefficients, kinetics, sorption isotherms (three adsorption model correlations were tested) and the acidic concentration effect were studied.

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Abstract  

The equilibrium extraction behavior of Sm(III), Eu(III) and Dy(III) from aqueous NaClO4 solutions in the pH range of 4–9 at 0.1 M ionic strength into organic solutions of 1-nitroso-2-naphthol (HA) and 1,10-phenanthroline (Phen) has been studied. The equilibrium concentrations of Eu were assayed through the 344 keV photopeak of the152Eu radiotracer used. The concentrations of Sm and Dy were measured by irradiating one mL portions of the organic extract and analyzing the 104 and 108 keV photopeaks of the short-lived neutron activation products,155Sm and165mDy, respectively. Quantitative extraction of Eu with 5×10–2 M HA alone was obtained in the pH range of 6.7–7.8 with n-butanol, 7.4–8.5 with chloroform, 8.0–8.7 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.1–8.0 with methyl isobutyl ketone (MIBK). But, Eu was extracted only to a maximum of 78% and 83% in the pH range of 8.3–8.9 and 7.4–8.1 with carbon tetrachloride and xylene, respectively. The extraction of Sm and Dy were found quantitative in the pH range of 6.3–7.0 and 6.6–7.1, respectively, with 5×10–2 M HA alone in MIBK solutions. The synergistic extraction of Eu was quantitative in the pH range of 6.6–9.8 with chloroform, 7.8–8.9 with ethyl acetate, 7.7–8.5 with isoamyl alcohol and 6.0–9.6 with MIBK when 1×10–2 M each of HA and Phen were employed. Sm and Dy were quantitatively extracted into MIBK solutions containing 5×10–2 M each of HA and Phen in the pH range 6.0–7.5 and 6.1–7.5, respectively. The distribution ratios of these lanthanides (Ln) were determined as a function of pH, and HA and Phen concentrations. The analysis of the data suggests that these Ln are extracted as LnA3 chelates when HA alone is used. In the presence of HA and Phen, both LnA3(Phen) and LnA3(Phen)2 adducts are formed only in the MIBK system while LnA3(Phen) complexes are the predominant ones in all other solvent systems studied. The extraction constants and the adduct formation constants of these complexes have been calculated.

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Abstract  

Solid-state Ln–C8H7O3 compounds, where Ln stands for Eu(III) and Gd(III) and C8H7O3 is 3-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and decomposition of the isolated compounds.

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