Solvent Extraction of Eu(III) from Nitrate Media

Non fluorinated ionic liquid was used as a solvent of by bis (2-ethylhexyl)diglycolamic acid (DEHDGA) to investigate the extraction of Europium (III) various parameters: extractant concentration, pH, concentration of the salting-out agent and concentration of the europium(III) ion in the aqueous feed. The efficiency of extraction was enhanced by increasing the pH of the feed solution (aqueous) upto its maxium range pH 5, that subsequently decrease at high pH values [1].

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Room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim⁺][PF₆⁻]) was applied for the extraction of Eu³⁺ Th⁴⁺ from nitrate medium using tri-n-octylphosphine oxide (TOPO) as an extractant the results were compared with extraction method of dichloro methane. Both methods involved solavation mechanism by forming [Eu(TOPO)33+](NO₃⁻)₃species. Another outcome was elucidated that the method also involve cation exchange mechanism by formation of [Th(TOPO)34+](NO₃⁻)₄ in dichloro methane, while Th4+ and Eu3+ not effected by presence of TOPO in ionic liquid method. So it can be concluded that formation of [Th(TOPO)⁴⁺](NO₃⁻)(PF₆⁻)₃ invloves that mixed ion exchange –solvation mechanism for the extraction of Th4+ ion [2].

various substituted diglycol amide (DGA) solvent extractants: N,N,N′N′-tetra(2-ethylhexyl) diglycolamide (T2EHDGA); N,N,N′N′-tetra-n-octyl diglycolamide (TODGA); N,N,N′N′-tetra-n-hexyl diglycolamide (THDGA); N,N,N′N′-tetra-n-decyl diglycolamide (TDDGA) and N,N,N′N′-tetra-n-pentyl diglycolamide (TPDGA) for the investigation Eu3+ ion transport property in nitric acid solvent extraction and supported liquid membrance (SLM) methodology. Slope analysis method was utilized to determind the nature of extracted species. By using DGAs various parameters like effect of phase modifier assay on extraction of Eu 3+ ion and effect of feed acidity were investigated [3].

Alok Rout et al prepared the ionic liquids, tri-n-octylmethylammonium bis(2-ethylhexyl)phosphate ([A336]⁺[DEHP]⁻) and tri-n-octylmethylammonium bis(2-ethylhexyl)diglycolamate ([A336]⁺[DGA]⁻) and characterized by IR and NMR spectroscopy. The extraction behavior of europium (III) in the solution of these ionic liquids present in different molecular diluents was investigated using in variation of different parameters like pH, nature of diluent, concentration of ionic liquid. The data obtained were compared with those obtained in a solution composed of the precursors of ionic liquid. The extraction of europium (III) in [A336]⁺[DEHP]⁻and [A336]⁺[DGA]⁻ionic liquids showed a strong dependence on the nature of molecular diluent used. The distribution ratio of Eu(III) increased with increase of pH; at pH>2, the distribution ratios obtained in ionic liquids were much higher than their precursors. The effect of diethylenetriaminepentaacetic acid (DTPA) on the extraction of Am(III) and Eu(III) at a fixed pH was studied to separate europium (III) from americium (III). Superior extraction of the target metals and excellent separation factors achieved with the use of these ionic liquids in conventional diluents indicates the feasibility of separating lanthanides from actinides [4].

W. Wang et al. was studied the extraction of europium by using an anionic surfactant. The influence of concentration of anionic surfactant, extraction temperature, pH, concentration of co-surfactant, salting out agent and aqueous- microemulsion ratio on extraction yield were studied by using sodium oleate (NaOL)/pentanol/heptanes/NaCl system. The extraction yield (E%) was found above 99%, when the R=8, Probably Europium was extracted in form of Eu(OL)2Cl into the microemulsion phase. The back-extraction was performed by using hydrochloric acid (0.8mol/L), back extraction resulted the yields 95.15% [5].

Extraction equilibrium constants were investigated by using nonlinear least squares method and a chemically based model was also developed. In the suggested model the salvation extraction and cation exchange reaction occurs in high and low acidity regions respectively. The non-ideality of aqueous phase and (HR)₂ were adjusted and corrected by complexation of metal with chloride ion and (HR)₂ replacing by using efficient concentration. The model verified by finding the close results of calculated metal distribution ratios and experimental results.

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E. Makrlík et al has been investigated the micro-quantity of europium and americium by using nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B^–) in presence of 1,2-(diphenylphosphino)ethylene dioxide (DPPEDO, L). The values of stability constant of both complexes are comparable in water saturated nitrobenzene. Stability of the complexes HL⁺_org and HL⁺_2;org in nitrobenzene saturated with water increases in the series of DBDECMP DPPEDO &DPBCMPO‘‘classical’’ CMPO, whereas the stability of the EuL³⁺_n;org and AmL³⁺_n;org (n = 2, 3, 4) complexes in the mentioned medium increases in the DBDECMPDPPEDODPBCMPO‘‘classical’’ CMPO order [7].

The extraction of Eu(III) was investigated by Awwadet al, from nitrate medium by CYANEX921 (C921). It was found that the chemical formula of the main extracted species in the organic phase is Eu(NO3)(3).3[C921] for extraction by C921. It was found that the Eu(III) percent extracted from toluene, n-hexane, cyclohexane and kerosene was nearly similar but with faster phase separation in favor of toluene. The relation between the shaking time and the percent of extracted C921 (%E) was studied at different pH. It was found that the best shaking time is 20 min at pH between 0.5-1.0, whereas at pH 2.0 the best shaking time is 15 min. The maximum extraction of Eu(III) was found to be after 5 min at pH 3.0. The extraction of Eu(III) increase with increasing of pH, however, the extraction precent increase from 28.5% at pH 0.5 to 98% at pH 3.0 The calculated average for the extraction constant is 6.58 at pH 3.0 under various C921 concentrations. From the data obtained, it was found that arsenazoIII (AIII) is a good stripper for Eu from organic phase which reach to 65% at pH 2. The stripping of Eu decreased from 57% to 2% when rising the pH in range of 0.5 to 11 (10).

Ohashi et al investigated the extraction of lanthanoids(III) (Ln(III) =, Eu(III) , La(III) and Lu(III) by using techniques cloud point extraction in presence and absence of di(2-ethylhexyl)phosphoric acid with triton X-100 and suggested that the extraction of Ln(III) into the surfactant-rich phase in absence of chelating agent was occurred due impurities existence in Triton X-100. The extraction yield was obtained more than 91% for all Ln(III) metals by using 3.0 x 10(-5) mol dm(-3) HDEHP and 2.0% (v/v) Triton X-100 (11).

Solvent extraction of Eu(III) from nitrate media with 4-acyl-isoxazol-5-ones and 2-acyl-5-diluents has been studied by Jaoval Arichi. Due to competitive complication of Eu³⁺ by NO₃^– in the aqueous phase, the extraction from nitrate medium is less effective than from per chlorate medium [12] Synergic extraction of Eu (III), Tb (III), with 2-thenoyltrifluoroactone and tribenzyl amine as neutral donor from chloroform from per chlorate media at lower pH was reportedly M. M. Saeed et al. The effect of temperature on extraction has also been studied [13] F.A. Shehata investigated the synergic extraction of trivalent Eu, Gd and Am from aqueous per chlorate medium using mixtures of thenoyl trifluoroacetone (HTTA) and 15-Crown-5 or 18-Crown-6 in chloroform at (25 ± I) (slope analysis of the M (TTA)₃. (CE)₂ for extracted species. The stability order took the sequence Eu(TTA)₃. (CE)₂>GA(TTA)₃. (CE)₂ with 18C6 [14]. A. Ali suggested the synergic extraction of, Eu (III), Ce (III) and Tm (III) with a mixture of tributyl phosphine oxide Picrolonic acid in chloroform. Picrolonic acid acted as a chelating agent and tributyl phosphine as a metal legend in chloroform. Among the anions fluoride, oxalate citrate and cyanide ions masked the extraction, whereas Fe (II), Cu (II) and No(II) reduce the extraction [15]. Extraction of Eu (III) and Tm (III) with picrolonic acid in MIBK was investigated by A. Ali. The buffer solution of pH was used. The composition of organic addict responsible for extraction of these material ions have been calculated by slope analysis method. Among the anions, citrate, fluoride, oxalate and cyanide ions masked the extraction, when the, Cu(II), Ni(II), Fe(III) and Co(II) minimized the extraction. D.F. Peppard compared the liquid – liquid extraction behaviour of Eu(II) and Eu(III) [16].