Solvent extraction of Np(IV) and Pu(IV) with mixtures of TOPO and HTTA

Solutions of HTTA are known to extract tetravalent actinides as M(TTA)₄ species. When TOPO is added to HTTA solutions, the extracting of Np(IV) and Pu(IV) from aqueous perchloric acid was enhanced enormously. The species responsible for the enhanced extraction were identified from the extraction data by the slope ratio method and JOB's method. It was found that the predominant species responsible for enhancement in the extraction, when [HTTA]≫[TOPO], was M(TTA)₄. TOPO for both Np(IV) and Pu(IV). Furthermore, it was established that depending on the relative concentrations of HTTA and TOPO, a number of species with the composition M(TTA)_a(ClO₄)_4-a·b TOPO, with a ranging from 1 to 4 and b having values of 1 or 2, are involved in the extraction. Several equilibrium constant values are given. Fuel Reprocessing Division.     

Substoichiometric liquid-liquid extraction and determination of vanadium based on the synergic effect of thenolytrifluoroacetone and trioctylphosphine oxide

Vanadium(IV) is extracted synergically with thenoyltrifluoroacetone (HTTA) and trioctylphosphine oxide (TOPO) in cyclohexane as the mixed ligand complex, VO(TTA)₂TOPO. The synergic extraction constant is 10^5.06. The system can be used for the substoichiometric extraction of vanadium(IV); vanadium(IV) is extracted at pH 4.0–5.0 with a substoichiometric amount of HTTA in the presence of an excess of TOPO. The substoichiometric process combined with isotope dilution was successfully applied to the determination of vanadium(IV) in NBS-1633 coal fly ash; the value found was 222.5 ± 3.5 μg g^?1. The method is shown to be accurate and precise.     

Thermodynamics of the extraction of Eu3+ with thenoyltrifluoroacetone,triphenylarsine oxide and other phosphine oxides

Extraction of Eu³⁺ from 0.1M aqueous perchlorate medium by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and tributylphosphate (TBP), HTTA and triphenylphosphine oxide (TPPO), HTTA and trioctylphosphine oxide (TOPO) and HTTA and triphenylarsine oxide (TPAsO) has been studied at various temperatures allowing for the elucidation of the mechanism of extraction in each case and a comparison between the various bases.     

Interaction effect between thenoyltrifluoroacetone and tri-n-octylphoshine oxide in the synergistic extraction of trivalent lanthanides. Determination of the composition of the extracted species+ of the extracted species

The distribution constant K_D(HTTA) of thenoyltrifluoroacetone between 10^–3M HNO₃ and cyclohexane was determined by means of spectrophotometric measurements of HTTA concentration in the aqueous phase. The distribution ratio, D, of HTTA, when tri-n-octylphosphine (TOPO) is present, and the equilibrium constant, _n , of the reaction between HTTA and TOPO in the organic phase were also determined. By means of the known K_D(HTTA) and D values, the equilibrium constant of the HTTA-TOPO interaction was calculated. Making use of K_D(HTTA) and _n values and of the slope analysis method, the composition of the extracted lanthanide complexes was established. By considering the interaction reaction between the extractants, the species Ln(TTA)₃ · TOPO and Ln(TTA)₃ · 2(TOPO), for Ln=La and Yb, were identified in the organic phase. The equilibrium constants of the reactions that give rise to the species were also calculated.From a thesis submitted by D. I. T. FÁVARO to the University of São Paulo in partial fulfillment for a Doctor of Sciences Degree in Nuclear Technology.     

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) or tri-n-octylphosphine oxide (TOPO)

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and oxo donors with widely varying basicity, viz. diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octylphosphine-oxide (TOPO) has been studied at various fixed temperatures. Results indicate that the equilibrium constants in the organic phase for addition reactions (K_S) with these donors follow their order of basicity (K_H) viz. DPSO (0.033)<TBP (0.16)TOPO (8.9) with log K_S values of 3.70, 4.28 and 6.45, respectively. The thermodynamic parameters associated with the formation of these systems have been evaluted by the temperature coefficient method. The results indicate that the complex in the organic phase for DPSO and TBP is stabilized only by enthalpy, whereas both enthalpy and entropy contribute to the stabilization of the TOPO complex. Also, enthalpy contribution is more prominent as compared with the UO ₂ ²⁺ /HTTA/TOPO system, where both enthalpy and entropy contribute almost equally.     

Liquid-liquid extraction of thorium/IV/ with LIX-54 and its mixtures

Solvent extraction of thorium/IV/ by a commercially available chelating extractant LIX-54 /a -diketone derivative/ /HA/ and its mixtures with tri-n-butyl phosphate /TBP/, thenoyltrifluoroacetone /HTTA/ and tri-n-octyl phosphineoxide /TOPO/ in benzene as the diluent have been studied. Quantitative extraction of thorium/IV/ by the mixture of 10% LIX-54 and 0.1M TOPO was noticed at pH 2.8. Influence of various concentrations of HTTA and TOPO in their mixtures with LIX-54 on the extraction of the same metal ion has been investigated and pronounced synergism was observed. Slope analyses determination shows the extracted species to be possibly of the type [Th/TTA/₂/A/₂] in case of extraction by mixtures of HTTA and LIX-54. Slopes of the linear plots were computed employing regression analysis, and variance in results has been shown.     

Solvent extraction of Er(III) and Lu(III) with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester in presence of some reagents

The extraction of Er(III) and Lu(III) from thiocyanate media with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) and also with mixtures of EHEHPA and thenoltrifluoroacetone (HTTA) or tri-n-octylphosphine oxide (TOPO) or bis 2-ethylhexyl sulfoxide (B2EHSO) in benzene has been studied systematically. Synergistic effects have been observed with mixtures of EHEHPA+HTTA or TOPO. On the other hand, antagonistic effects have been observed with mixtures of EHEHPA+B2EHSO. These extraction data have been analyzed theoretically with the aid of a computer by taking into account complexation of the metal in the aqueous phase by SCN^– and plausible complexation in the organic phase. The extraction constants of the various product species have been deduced by non-linear regression analysis. The stability constants for the thiocyanate complexes of the metal ions have also been determined.     

Synergistic extraction of radium using 2-thenoyltrifluoroacetone and tributyl phosphate or trioctylphosphine oxide

The extraction of radium into a mixture of 2-thenoyltrifluoroacetone (HTTA) and tributyl phosphate (TBP) or trioctylphosphine oxide (TOPO) in n-hexane or cyclohexane has been investigated with regard to the dependence on pH, and TBP and TOPO concentrations. It has been found that the formation of mixed complexes of the type Ra(TTA)₂ (TBP)₂ and Ra(TTA)₂(TOPO)₂ occurs and the overall extraction constants of both complexes were calculated. With the systems described, very high distribution ratios of radium have been attained; these may advantageously be used for the separation and concentration of traces of radium.     

Synergetic extraction of Co3+

The extraction of Co³⁺ from 0.1M aqueous acetate medium buffered to pH 5.3 by thenoyltrifluoroacetone (HTTA) in benzene and by 8-quinolinol (HQ) also in benzene at various temperatures has been studied. The species formed were Co(OH)₂ (TTA)·(HTTA)₂ and Co(Q₃)·2HQ, respectively. 1,10-phenanthroline (Phen) as a base was also mixed with HTTA to form the species Co(OH)₂(TTA)·(HTTA). Phen and Co(OH)₂ (TTA)(HTTA)·2Phen. No synergism was observed upon the addition of Phen to HQ.     

Solvent Extraction of Uranium(VI), Plutonium(VI) and Americium(III) with HTTA/HPMBP Using Mono- and Bi-Functional Neutral Donors: Synergism and Thermodynamics

Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO₃ with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz, DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as dileunt. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (G ⁰, H ⁰, S ⁰) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log K _s values of bi-functional donors were found to be very high and deviate from the linear plot (log K _s vs. log K _h ) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA system studied. This was supported by high +ve S ⁰ values obtained for this system.     

Extraction-separation of Eu(III) and Th(IV) ions from nitrate media into a room-temperature ionic liquid

Application of a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim⁺][PF₆ ^?]), in the extraction of Eu(III) and Th(IV) ions from nitrate media using tri-n-octylphosphine oxide (TOPO) as extractant is investigated. The results are compared with those obtained in dichloromethane. It is shown that the europium ions are extracted via a solvation mechanism by formation of [Eu(TOPO) ₃ ³⁺ ](NO₃ ^?)₃ species in both [C₄mim⁺][PF₆ ^?] and dichloromethane. Nevertheless, application of the studied RTIL makes a significant improvement in the extraction efficiency of europium ions. A different attitude was observed for the extraction of thorium ions. In fact, although the analysis of the extraction data of these ions from sodium nitrate solutions confirms the formation of [Th(TOPO) ₃ ⁴⁺ ](NO₃ ^?)₄ species in dichloromethane, the extraction of these ions into the ionic liquid was not affected by the presence of TOPO. This latter outcome states the process takes place by a cation-exchange mechanism. It is found that the extraction of thorium ions diminishes in the presence of nitric acid. Interestingly, in contrast to the results observed in the extraction of thorium ions from sodium nitrate solutions, TOPO shows a co-operative effect on the extraction of these ions from nitric acid media. This allows considering the mechanism of the extraction of Th⁴⁺ ions from nitric acid media as a mixed ion exchange-solvation mechanisms by formation of [Th(TOPO)⁴⁺](NO₃ ^?)(PF₆ ^?)₃ species.     

Kinetics and mechanism of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone-triphenylarsine oxide mixture in chloroform and aqueous nitrate medium

The kinetics of distribution of Am(III) and Eu(III) between thenoyltrifluoroacetone (HTTA) and triphenylarsine oxide (Ph₃AsO) mixture in chloroform and aqueous nitrate medium has been investigated using a stirred Lewis cell at ionic strength of 0.1M. The effect of the concentration of HTTA, Ph₃AsO, H⁺ and NO ₃ ^– on the rate of distribution of Am(III) and Eu(III) was studied. The results were interpreted by reaction mechanisms where the rate-determining steps are the parallel reactions of Am(OH)²⁺ or Eu(OH)²⁺ with one HTTA molecule and one Ph₃AsO molecule in the aqueous medium. The values at 25 °C of the rate constantk _HLL (HL=HTTA andL=Ph₃AsO) are 1.6±0.3·10⁶M^–2·s^–1 and 2.3±±0.3·10⁸M^–2·s^–1 for Am(III) and Eu(III), respectively.     

Synergistic extraction of alkaline earth cations with 3-phenyl-4-benzoyl-isoxazol-5-one and tri-n-octylphosphine oxide in toluene

The synergistic extraction of alkaline earth cations from 1M NaNO₃ aqueous solutions with 3-phenyl-4-benzoylisoxazol-5-one (HPBI) and tri-n-octylphosphine oxide (TOPO) in toluene at 25°C has been studied. The extraction efficiency follows the order Ba²⁺<Sr²⁺<Ca²⁺<Mg²⁺, which is the same as that previously observed with 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HPMBP). The extraction occurs at a lower pH range than with HPMBP because of the higher acidity of HPBI. The extracted species are M(PBI)₂(TOPO) _x withx=2 for M=Mg, Ca, Sr and Ba (logK _1,2,2=3.91, 1.18 and 0.29 respectively) and withx=3 for M=Sr and Ba (logK _1,2,3=3.28 and 2.07 respectively). The strong interactions which occur between HPBI and TOPO (logK _int=1.84) have been considered in the extraction constant calculations..     

2,2′-Dipyridyl and 1,10-phenanthroline in the synergetic extraction of Eu3+

The thermodynamics of the extraction of Eu³⁺ by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and bidentate amine bases such as 2,2-dipyridyl (Dipy) and 1,10-phenanthroline (Phen) in benzene from an aqueous phase fixed to 0.1M ionic strength (NaClO₄), pH 3.9, has been investigated. Phenanthroline forms both the Eu(TTA)₃·Phen and Eu(TTA)₃·2Phen species, which are much stronger than the dipyridyl complexes. The diluent effect on the extraction is also studied.     

Solvent extraction of hafnium(IV) by TBP and topo from acidic organic-aqueous solutions

Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO₄, 5M HCl, 6M HNO₃ and 8M H₂SO₄ solutions, and by 1·10^?4 M TOPO solution in benzene from 2M HClO₄ and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions.     

Inductively coupled plasma atomic emission spectroscopic determination of rare earth elements in geological samples after preconcentration by countercurrent chromatography—Part II

This paper directly links up with Part I [Spectrochim. Acta 48B, 1365 (1993)] which treats the first application of countercurrent chromatography (CCC) for pre-separation of rare earth elements (REE) in rocks. The rapid and reliable separation and pre-concentration of “light” REE and Y can be achieved using a system of 0.5 mol/l di-2-ethylhexylphosphoric acid (D2EHPA) in n-decane-hydrochloric acid of different concentrations and a planetary centrifuge as a CCC device. However, Tm, Yb and Lu are partially retained in the stationary phase. Comparative data is presented on three other two-phase liquid systems containing trioctylphosphine oxide (TOPO); D2EHPA and TOPO mixtures and diphenyl(dibutylcarbamoylmethylphosphine)oxide (Ph₂-Bu₂) as extractants in terms of their ability for whole REE group complete isolation from the rock constituents. The partial losses of “light” REE (La and Ce) occurred in the system of 0.1 mol/l solution of TOPO in isobutylmethylketone (IBMK) (stationary phase)-1 mol/l NH₄NO₃-6 mol/l HCl aqueous solutions (mobile phase). Complete isolution of the entire REE group can be reached in two systems: 0.3 mol/l D2EHPA + 0.02 ml/l TOPO in the solvents mixture (3:1) of n-decane + IBMK, respectively (stationary phase)-1 mol/l NH₄NO₃-6 mol/l HCl aqueous solution (mobile phase), and 1.0 mol/l Ph₂-Bu₂ solution in chloroform (stationary phase)-3 mol/l HNO₃ aqueous solution (mobile phase). The D2EHPA + TOPO mixture is recommended as more economic and accessible.     

Determination of trace transition elements in ultra high purity sodium and calcium carbonates by neutron activation analysis

Résumé On mesure le cuivre 64 et le manganèse 56 dans du carbonate de sodium ultra pur par spectroscopie du rayonnement gamma après élimination du²⁴Na par passage sur colonnes de pentoxide d'antimoine hydraté (PAH); On a aussi déterminé le cobalt, le chrome et le fer par détection spectrométrique non-destructive du rayonnement gamma du⁶⁰Co,⁵⁹Fe et⁵¹Cr. Dans le cas de CaCo₃, après irradiation et dissolution, on a déterminé simultanément le⁶⁴Cu et le⁵⁶Mn, par une séparation radiochimique sélective à pH 3 à 4 avec un mélange de dithizone (H₂D) et d'acide pynolidinedithiocarbamique (HPDC) dans CHCL₃. L'interférence radioactive de⁴⁷Sc et⁴⁷Ca produits pendant 100 heures d'irradiation de CaCO₃, étaient supprimées par extraction sélective de ce dernier en milieu HCl 5,0 M par l'oxyde de Tri-n-octylphosphine (TOPO) 0,1 M dans du cyclohexane. On a utilisé en mélange de 0,1 M Thenoyltrifluoroacetone (HTTA) 0,1 M et de TOPO 0,1 M dans du cyclohexane pour enlever le⁴⁷Ca à pH≥8.0. Après avoir éliminé l'activité des isotopes de la matrice, on mesure les pics photoélectriques de⁵⁹Fe.⁶⁰Co et⁵¹Cr pour doser ces impuretés.      

Extraction behaviors of Eu,Th, U and Am with diamides+thenoyltrifluoroacetone

N,N-dimethyl-N,N-dihexyl-3-oxapentanediamide, DMDHOPDA, N,N-dihexyl-3-thiopentanediamide, DHTPDA and N,N-dihexyl-3-oxapentanediamide, DHOPDA were synthesized and tested for the synergistic extraction of Eu³⁺, Th⁴⁺, UO ₂ ²⁺ , NpO ₂ ⁺ and Am³⁺ with thenoyltrifluoroacetone (HTTA). Although Eu³⁺, Th⁴⁺, UO ₂ ²⁺ and Am³⁺ were not extracted by DHTPDA or DHOPDA alone, they were extracted synergistically when combined with HTTA. Analysis of the dependency of extraction on pH and extractant concentration indicated that the dominant extracted species were Eu(TTA)₃(A), Th(TTA)₃(A)(X), UO₂(TTA)₂(A) and Am(TTA)₃(A) (where A is diamide, and X is chloroacetate or ClO ₄ ^– ).     

Effect of oxidation-reduction on the extraction of uranium from wet phosphoric acid by DEHPA/TOPO

Uranium is recovered from wet phosphoric acid by DEHPA/TOPO in kerosene. Uranium is present in wet phosphoric acid in the tetravalent and hexavalent states but DEHPA/TOPO extracts uranium in the hexavalent state only. The ratio of U⁴⁺/U⁶⁺ depends on several factors such as the origin of the phosphate rock, the method of preparation of phosphoric acid and the presence of other impurities. Therefore it is important to oxidize the wet acid to convert all uranium to U⁶⁺ before extraction. Uranium is stripped from the solvent by a reverse process where a concentrated phosphoric acid is used under reducing conditions. This paper studies the oxidation of wet phosphoric acid from Homs plant/Syria by H₂O₂ oxidant and the effect of oxidation on extraction coefficientK. It also studies the reduction by iron and its effect on back extraction of uranium from the solvent to phosphoric acid.     

Effect of interaction of thenoyltrifluoroacetone with neutral oxo-donors in the synergistic extraction of tervalent actinides

The interaction of HTTA with TBP, DOSO, DBBP and TOPO in xylene has been studied by a spectrophotometric method. The complex species formed is HTTA. S (where S is a neutral donor) and the equilibrium constants for the formation of the species follow the order TOPO > DBBP > DOSO > TBP. After application of a correction for the HTTA-S interaction, the free HTTA and S concentrations in the organic phase were calculated. Plots of log D vs. log [HTTA] for the tervalent actinides Am, Cm, Bk and Cf gave straight lines with a slope of 3 only after application of the interaction correction, otherwise curves with slopes varying from 3 to 2 were found. The equilibrium constants of the organic phase synergistic reactions of the tervalent actinides are found to be approximately 10% higher after application of the HTTA-S interaction correction.