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Abstract  

The solubility isotherm of the system Eu2O3-SeO2-H2O was studied at 100C. Certain amounts of the obtained selenites (normal and acid) were subjected to thermal analysis. The intermediate phases were isolated and chemical and X-ray phase analysis was made. The scheme of thermal decomposition was determined.

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The sorption of Eu(III) ions onto PAN loaded PUF has been optimized and investigated under the influence of various temperatures, i.e., 303, 313 and 323 K. Maximum retention (>96%) of Eu(III) ions (1.79. 10-5M) onto PAN loaded PUF (7.75 mg. ml-1) was achieved after 30-minute equilibration time from pH 7 buffer solution. The variation of sorption with temperature yields the thermodynamic parameters ΔH=79±2 kJ. mol-1, ΔS=276±7 kJ. mol-1. K-1and ΔG=-1.4±0.1 kJ. mol-1at 298 K. The positive value of enthalpy and negative free energy show endothermic and spontaneous nature of sorption, respectively. The sorption data followed Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherms at all the three given temperatures. The Freundlich constant 1/n=0.70, 0.62 and 0.55 and sorption capacities C m=10.8 mmol. g-1, 6.1 mmol. g-1and 4.4 mmol. g-1, respectively, decreased with increasing temperature. Similarly, the sorption capacities of D-R isotherm X m=197.6 µmol. g-1, 201.2 µmol. g-1and 137.4 µmol. g-1, also decreased with temperature. However, the sorption free energy E=10.2 kJ. mol-1, 11.2 kJ. mol-1and 12.7 kJ. mol-1, increased with temperature. The monolayer coverage (Q) computed from Langmuir isotherm was 11.1±0.6 µmol. g-1and remains constant at all the three temperatures investigated. However, the binding energy constant bincreased with temperature. The relationship of bwith temperature and differential heat of adsorption (ΔH diff) have been evaluated and discussed.

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A radiotracer method, initially developed to analyze migration from retail plastic food packaging into food simulants, has been developed to assess the measurement of inorganic contaminants migrating from recycled paper and board into real food. This new radiotracer method has been applied to the study of 10 food samples and their corresponding recycled paper and board packaging. Samples of paper and board were irradiated in a thermal neutron flux of 1.26 . 1016n m-2 . s-1 for 15 hours to activate elements of interest. After a decay period of 10 days the paper and board was placed in contact with the corresponding foodstuff. The food was analyzed for any radioactivity migrating from the packaging by gamma-ray spectrometry. Samples were analyzed regularly during the 90 days contact time. Detection limits for the determination of migration was as low as a few µg/kg in the food. Results from the migration study have shown that, of the 60 elements measured, only Zn and Fe were detected in food, at concentrations of 0.012-0.25, and 0.045-0.11 mg/kg, respectively. This was despite the recycled paper and board samples being highly elevated in many other elements such as Cr (0.9-15.1 mg/kg) and Ba (3.3-75.4 mg/kg). The level of migration of Zn and Fe into food from packaging was insignificant compared to the UK recommended daily allowances of 15 mg, and, therefore, represented no hazard to human health.

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The thermal behavior of[Eu2(BA)6(dmbpy)2] (BA=C7H5O 2 , benzoate; dmbpy=C12H12N2, 4,4-dimethyl-2,2-bipyridine) and its kinetics were studied under the non-isothermal condition in a static air atmosphere by TG-DTG, IR and SEM methods. Thermal decomposition of [Eu2(BA)6(dmbpy)2] occurred in four consecutive stages at T P 232, 360, 455 and 495°C. The kinetic parameters were obtained from analysis of the TG-DTG curves by Achar and Madhusudanan—Krishnan—Ninan (MKN) methods. The most probable mechanisms for the first stage was suggested by comparing the kinetics parameters.

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Abstract  

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  

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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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  

151Eu Mössbauer spectrum of IR-transmitting calcium aluminate glass, 60CaO·32Al2O3·5Fe2O3·3Eu2O3, consists of a broad peak due to distorted Eu(III) with and values of 0.91 and –2.02 mm·s–1, respectively. Debye temperatures ( D) of 360 and 320 K were obtained from the temperature dependence of absorption area (A) and that of , respectively. These D values indicate that Eu(III) atoms occupy substitutional sites of distorted Al(III)O4 tetrahedra in calcium aluminate glass. The value of 0.62 mm/s obtained from the heat-treated sample (glass ceramic) indicates that Eu(III)-O bonds became less covalent. A smaller value of –1.20 mm·s–1 was obtained for Eu(III) in the glass ceramic, indicating less distorted Eu(III)O4 tetrahedra.

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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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