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Journal of Thermal Analysis and Calorimetry
Authors: D. Melo, G. Vicentini, L. Zinner, K. Zinner, H. de Souza, M. Batista, A. Garrido Pedrosa, and R. Bezerra

Abstract  

Complexes of neodymium and europium with amides and aminoxides were synthesized and characterized by complexometric analyses with EDTA, CHN microanalytical procedures, IR absorption spectra, absorption spectra of neodymium complexes, emission spectrum of europium compounds at 77 K, thermogravimetric analyses in N2 and differential scanning calorimetry (DSC) in N2. Infrared spectroscopy results revealed that the nitrate molecules are bound to the central ions as bidentate. Thermogravimetric plots indicated that the decomposition of the complexes occurs in the range 363-1163 K and resulted in the formation of Ln2O3 residues.

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Abstract  

Natural mixture containing mostly minerals of iron, sillicon, magnesium, aluminium and calcium was exploited for the decontamination study of europium radionuclides from aqueous radioactive waste solutions. The physicochemical conditions, such as shaking and equilibration time, nature of hydrogen ions, pH, temperature, concentrations of adsorbate and adsorbent were experimentally determined. This study showed quantitative adsorption beyond pH 7 and under optimized conditions, up to 33 g of the adsorbate can be rapidly removed from radioactive effluents using only 1 kg of the mineral mixture (MM). Desorption study of the solidified radioactive waste product reveals no significant loss (< 0.01% month), indicating MM as an effective material for removal of radioactive europium and storing it in solid form over a long period of time.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Kwang-Pill Lee, Sun-Tae Hwang, Y. Yamada, K. Furukawa, and Shin-Ichi Ohno

Abstract  

Impact of energetic heavy particles on europium compound surfaces gives rise to radiative optical emission from reflected and sputtered particles and from the excited states of the solid compounds. In the present paper we discuss the optical spectrum and the sputtered secondary ion mass spectrum observed when solid europium oxide (Eu2O3) and europium chloride (EuCl3) are bombarded with 90 keV Ar+ ions from an ion accelerator. We observe the reduction reaction in solid europium chloride (EuCl3) by bombardment with a 20 A/cm2 beam of 90 keV Ar+ ions.

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Abstract  

A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10−5 to 10−7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.

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Abstract  

Sorption of europium on zirconium oxide has been studies as a function of shaking time, concentration and nature of electrolyte. The effect of initial europium concentration and the amount of adsorbent has been investigated in the range from 6.6·10–10 to 6.6·10–8 mol·dm–3 and between 10 to 200 mg of the oxide. Maximum sorption (>99.8%) from pH 10 buffer and low sorption (<3%) was observed from 0.01 mol·dm–3 nitric or perchloric acid solution. Citrate, sulfate, EDTA and carbonate reduced the sorption significantly. Under optimal conditions Ag(I), Cs(I), Tc(VII), Sb(V), Cu(II), Nd(III), Fe(III), and especially Nd and Fe showed low distribution coefficients. The data followed both Dubinin-Radushkevich and Langmuir-type isotherms. The mean free energy, of sorption was evaluated to be 10.1 kJ mol–1 and the sorption capacity was found to be 22.2 mmol g–1, using the Dubinin-Radushkevich isotherm.

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Abstract  

The solvent extraction of europium(III) with di-n-butylphosphoric {HDBP} and di-(2-ethylhexyl)phosphoric {HDEHP} acids in 3-methyl-1-butanol from 0.1 and 1.0M perchlorate medium {Na(H)ClO4} was studied at pH 1–3. It was found that the composition of the species extracted into the organic phase depended on the concentration of perchlorate anion. In 0.1M Na(H)ClO4 solutions, simple chelates Eu(DBP)3 or Eu(DEHP)3 are extracted while mixed ligand complexes Eu(DBP)2ClO4 or Eu(DEHP)2ClO4 are also extracted from 1.0M Na(H)ClO4 solutions. Compared to the extractions from perchlorate solutions, no such change in the extraction mechanism has been observed in chloride solutions containing up to 1.0M Cl. The extraction of europium(III) with these extractants into toluene from 0.1M perchlorate or chloride media was studied as well. The extraction species found were identical with those reported in the literature, i.e. {Eu[H(DBP)2]3, Eu[H(DEHP)2]3}. The extraction equilibrium constants were calculated for all complexes.

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Summary  

Sorption behavior of europium, Eu3+, on SiO2 . xH2O (silica gel) has been investigated as a function of time, the amount of silica gel, Eu3+ concentration, the ionic strength, and pH (in absence and in presence of carbonate). The sorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The sorption capacity of silica gel was determined to be in the range of (2.62-8.00) . 10-7 mol/g at pH 5.30±0.05 and 0.20M NaClO4. The mean energy of sorption was calculated to be 13.50±0.05 kJ/mol from the D-R isotherm, suggesting the involvement of ion-exchange reactions in the sorption process. Sorption of Eu3+ decreased with increased ionic strength. A gradual decrease in pH with increased ionic strength supports the involvement of an ion-exchange mechanism in the sorption process. The diffusion coefficient of Eu3+ ion on silica gel was calculated as (3.98±0.12) . 10-13 m2 . s-1 under the particle diffusion-controlled conditions.

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Abstract  

The sorption of small amounts of europium(III) on iron(III) hydroxide and oxide has been studied as a function of pH. The mechanism of sorption is discussed. Optimum conditions have been found for the preconcentration of small or trace amounts of europium(III) by iron(III) hydroxide and oxide. The influence of complexing agents (EDTA, oxalate, tartrate and 5-sulfosalicylic acid) on the sorption of small amounts of europium(III) on iron(III) oxide has also been studied.

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Abstract  

The simultaneous substoichiometric separation of europium and terbium is presented and its application to the determination of these elements with DTPA and HTTA is developed. Experimental results for the simultaneous substoichiometric separation are in good agreement with the theoretical results introduced by the principle. Europium and terbium in orchard leaves are determined by simultaneous substoichiometric neutron activation. The analytical values are 23±1.1 ppb for europium, and 17±1.2 ppb for terbium.

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Abstract  

Eu-151 Mössbauer spectra of tetrakis/diethyldithiophosphato/europium/III/ compounds suggests substantial electron transfer from dithiophosphate ligand to europium. The photochemical reaction of these complexes was investigated in organic solutions, and it was demonstrated that the Mössbauer isomer shift was correlated with their 420 nm band.

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