The153/151Eu isotope separation factor (q) for the Eu(II)/Eu(III) chemical exchange in the liquid-liquid extraction system, containing Eu (III) in di (2-ethylhexyl) phosphoric acid (HDEHP) and Eu(II) in water acidified with hydrochloric acid, was found to be 0.9993±0.0002 (2) for the single stage. Some theoretical aspects of separation of the Eu isotopes are discussed. The decisive role of the electron exchange reaction and complexation by the counter-ion in the aqueous phase is emphasized.
Authors:Yanxia Geng, Zhan Li, Duoqiang Pan, and Wangsuo Wu
For the selective extraction of Am(III) and Eu(III), quadridentate divalent phenolic Schiff bases-bis-salicylaldehyde ethylenediamine
(H2salen) was investigated as a kind of extractant. The influences of alkaline cation, inorganic anion, ionic strength, pH and
the concentration of H2salen on the distribution ratio of Am(III) and Eu(III) were investigated in detail. As a result, Am(III) and Eu(III) made
anionic 1:1 complexes with the ligand (H2salen) and could be extracted into nitrobenzene as ion-pairs with a suitable monovalent counter anion in the aqueous solution,
the extracted species were possibly of the type Am(H2salen) Eu(salen)Cl and Eu(H2salen)Cl3, respectively. The extractability of Eu(III) was significantly stronger than that of Am(III) and the maximum separation factor,
SF(Am/Eu), was 96 at pH 4.0. The results indicated that H2salen had good selectivity for Am(III) and Eu(III).
Authors:Y. Wang, Q. Fan, P. Li, X. Zheng, J. Xu, Y. Jin, and W. Wu
The sorption of Eu(III) on calcareous soil as a function of pH, humic acid (HA), temperature and foreign ions was investigated
under ambient conditions. Eu(III) sorption on soil was strongly pH dependent in the observed pH range. The effect of ionic
strength was significant at pH < 7, and not obvious at pH > 8. The type of salt cation used had no visible influence on Eu(III)
uptake on soil, however at low pH values, the influence of anions was following the order: Cl− ≈ NO3− > ClO4−. In the presence of HA, the sorption edge obviously shifted about two pH units to the lower pH, whilst in range of pH 6–7,
the sorption of Eu(III) decreased with increasing pH because a considerable amount of Eu(III) was present as humate complexes
in aqueous phase, then increased again at pH > 11. The results indicated that the sorption of Eu(III) on soil mainly formed
outer-sphere complexes and/or ion exchange below pH ~7; whereas inner-sphere complexes and precipitation of Eu(OH)3(s) may play main role above pH ~8.
Authors:Y. Takahashi, T. Kimura, Y. Kato, Y. Minai, and T. Tominaga
Luminescence lifetime of Eu(III) in polyacrylate and polymaleate complexes has been measured to evaluate the number of water molecules bound to the ion. The number of residual water molecules hydrated to Eu(III) in the polyacrylate and polymaleate complexes ranged from 3.5 to 4.5 when the supporting electrolyte concentration was 0.01. The residual hydration number decreased with the addition of supporting electrolyte. These results indicate that Eu(III) is surrounded by polymolecular ligands in these complexes.
The selective transport of Am across a supported liquid membrane (SLM) has been investigated by using bis (2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a mobile carrier. This extractant containing soft donor atoms exhibits strong affinity for actinoids, giving a large separation factor between trivalent Am and Eu. Separation of Am from Eu was achieved by an SLM containing highly purified Cyanex 301. Americium was preferentially transported across the SLM and concentrated in the product solution, while most of Eu remained in the feed solution.
Authors:H. Mimura, H. Hoshi, K. Akiba, and Y. Onodera
Microcapsules enclosing an extractant with strong affinity for Am were prepared by employing a biopolymer gel as an immobilization matrix. A relatively large separation factor between Am and Eu was exhibited by the microcapsule containing of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301, HA) and alginic acid (HALG). The chromatographic separation of these metal ions was accomplished by gradient elution through the column packed with HA-HALG.
The extraction of Na3+, Eu3+ and Tm3+ by di-(2-ethylhexyl)phosphoric acid, HDEHP has been studied from various aqueous acidic solutions. The extraction of these elements is inversely proportional to the third power of the hydrogen ion concentration. Antagonistic effects were observed when the extraction was studied by mixtures of HDEHP and tributyl phosphate, TBP, or trioctylphosphine oxide, TOPO. The presence of water-miscible alcohols and acetone generally increases the extraction of these three elements from HCl solutions. Reaction mechanisms have been suggested and discussed in the light of the data obtained.
The extraction of Eu3+ and Am3+ by a mixture of CMPO and dicarbollide in nitrobenzene has been studied. The synergetic effect of dicarbollide is pronounced at low acidities but still lower than for previously studied DBDECMP. Separation properties towards Am/Eu pair are small.
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.
The extraction of Eu3+ from perchloric acid by ethyl hydrogen benzyl phosphonate (HEBP) dissolved in a series of organic diluents, has been studied at different temperatures. From the variation of the distribution ratio with temperature, the thermodynamic functions H, S and G have been determined. The meaning of the experimentally obtained thermodynamic quantities is discussed.