SYNERGISTIC SOLVENT EXTRACTION OF AM(III) AND EU(III) WITH THE SOFT DONOR TRIISOBUTYLPHOSPHINE SULFIDE AND THENOYLTRIFLUOROACETONE

The synergistic solvent extraction of Am(III) and Eu(III) with the neutral soft donor TIBPS and HTTA has been investigated using cyclohexane as the organic solvent and at an ionic strength of 0.1 M (NaCIO₄). The extracted species are [M(TTA)₂)] and [M(TTA)₂ (Clo₄) (TIBPS)] The extraction constants show that the synergistic factor is less than that for the analogous hard donor adducts (e.g., TBP and TOPO) and no preferential extraction of Am(III) over Eu(III) is observed.     

Synergistic Extraction Studies Using n-Octyl(Phenyl) N,N-Diisobutylcarbamoyl-Methylphosphine Oxide

Abstract

The effectiveness of n-octyl(phenyl)-N,N′-diisobutylcarbamoyl-methylphosphine oxide, CMPO, as a neutral extractant for the trivalent actinides and lanthanides from strong acid media has been well established. This investigation characterized the use of CMPO as a synergistic agent in the extraction of Am(III) and Eu(III) by thenoyltrifluoroacetone (HTTA). The distributions of the metal ions were measured using radiotracer techniques as functions of HTTA concentration, CMPO concentration and pH. The results show that the presence of CMPO enhances the extraction of Eu(III) and Am(III) by 10⁸. The synergistic adduct was M(TTA)₃·CMPO with no indication of higher complexes being formed. Unlike previous studies, the extraction of Eu(III) was more strongly enhanced than that of Am(III). The results showed little, if any, enhancement in the extraction efficiency due to the bidentate nature of the CMPO.     

Synergistic Extraction of Trivalent Actinides by Mixtures of Thenoyltrifluoroacetone and Neutral Oxo Donors

Abstract

The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf has been studied by mixtures of HTTA and TOPO as well as DOSO in xylene at 30°C. HTTA-S (TOPO, DOSO) interaction corrections have been applied to calculate the “free” S concentrations in the organic phase. In the extraction of trivalent actinides, the third-power dependence on [HTTA]_org at a fixed [S]_org has been observed only after applying this correction. The synergistic species M(TTA)₃.S and M(TTA)₃.2S were found to be extracted into the organic phase whose stability constants (β₁, β₂, and K ₂) have been evaluated. Extraction by HTTA + S(S = TOPO, DOSO, TBP, TBTP) shows the order of extraction to be Tm > Cf > Bk > Eu > Pm > Am > Cm for the trivalent ions. The Am/Cm separation factor with the synergistic mixtures is ～3 whereas with HTTA alone it is ～6 when they are extracted from the chloroacetate buffer.     

Thermodynamic and Spectroscopic Studies on Am(III) and Eu(III) in the Extraction System of N,N,N',N'-Tetraoctyl-3-Oxapentane-1,5-Diamide in n-Dodecane/Nitric Acid

Abstract

Thermodynamic parameters (ΔG, ΔH, and ΔS) for the extraction of trivalent f-elements, M(III) (M = Am, Eu), with N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) were determined in nitric acid/n-dodecane extraction system. The extraction of M(III) with TODGA was more exothermic than those with octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and dihexyl-N,N-diethylcarbamoylmethyl phosphonate (DHDECMP). The difference in ΔH between the extractants was attributed to the difference in the binding mode between them, i.e. tridentate (TODGA) and bidentate (CMPO and DHDECMP). In addition, from the results of luminescence lifetime measurement, it was found that the inner-sphere of extracted Eu(III) was dehydrated completely, and occupied by TODGA and/or NO₃ ^?.     

EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH₄NO₃, NH₄SCN, NH₄ClO₄ or a mixture of 0.3 M NH₄NO₃ + 0.7 M NH₄ClO₄ at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML₃ · 3CMPO (M = Am(III) or Eu(III), L = NO₃ ^?, SCN^? or ClO₄ ^?) and M(NO₃)(ClO₄)₂ · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The ?ΔG values follow the order SCN^? > NO₃ ^? + ClO₄ ^? > NO₃ ^? ≈ ClO₄ ^?, whereas the ?ΔH values an order NO₃ ^? + ClO₄ ^? > SCN^? > NO₃ ^? ≈ ClO₄ ^?. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.     

EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY A SYNERGISTIC MIXTURE OF THENOYLTRIFLUOROACETONE AND A LINEAR POLYETHER

Abstract

Mixtures of a linear polyether, l,13-bis[8-quinolyl]-l,4,7,10,13-pentaoxatridecane, K-5, and thenoyltrifluoroacetone, HTTA, have been shown to exhibit synergistic character in the extraction of trivalent lanthanides and actinides. The effect of the addition of K-5 to the organic phase on the extractions of Ce(III), Eu(III), Tm(III), Am(III), Cm(III), Bk(III), and Cf(III) by HTTA in chloroform from 0.5M NaNO₃ at 25°C has been measured. These results indicate the extraction is enhanced by the formation of M(TTA)₃K-5 adduct in the organic phase. The organic phase stability constants for the formation of these synergistic species have been calculated for all the metals studied. The magnitude of these organic phase stability constants for K-5 are similar to other common neutral donors. The order of stability does not follow the normal trend based on charge-to-radius ratio, but follows a pattern based on size, with Am(III) being the most stable.     

THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) FROM NITRATE AND THIOCYANATE MEDIA WITH OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE

ABSTRACT

The extraction of Am(III) and Eu(III) from 1.0 M NH₄NO₃ and NHS₄SCN at pH 2.60 into octyl(pheriyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in n-dodecane has been studied in the temperature range 15.0 to 45.0°C. Under all conditions, the species ML₃·CMPO is the dominant extracted complex. The extraction equilibrium constants are at least 10₃ higher in the SCN^- systems than in the NO₃ ^- systems. This difference is attributed to the relative energy associated with transfer of the anions from the aqueous to the: extractant phase. Extraction enthalpies and entropies have been calculated in each system from the temperature dependence of K_ex. Enthalpies are considerably more exothermic in the thiocyanate system for both metal ions. Comparison of ΔH_Am ^SCN with ΔH_EU ^SCN gives a possible indication of enhanced Am-SCN bond strength in the extracted complex.     

LUMINESCENCE STUDY OF Eu( III) COMPLEXES EXTRACTED IN THE ORGANIC PHASE

Luminescence lifetimes have been measured for Eu(III) extracted into benzene solutions. The extrac-tants were HDEHP, HTTA, and mixtures of HTTA with crown ethers, TBP, and TOPO. The results were consistent with no residual hydration for Eu(DEHP)₃, and three molecules of hydration for Eu(TTA) ₃,. The Eu(TTA) ₃,-(TOPO)? _n (n = 1,2) complexes have one water molecule or less. The hydration numbers from the luminescence lifetimes compare well with the values from Karl Fischer titrations. The hydration of the crown ether complexes can be related to the degree of steric hindrance by the aliphatic or aromatic groups attached to the crown ethers.     

Synergistic Extraction of Trivalent Actinides and Lanthanides Using Htta and an Aza-Crown Ether

Abstract

An aza-crown ether, 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (K22DD) has been shown to have a synergistic effect on the extraction of trivalent lanthanides and actinides by thenoyltrifluoroacetone (HTTA). The extraction of Am(III), Cm(III), Am(III), Eu(III), Ce(III), and Pm(III) from an aqueous acetate buffer system (pH=4.8) into HTTA/K22DD/chloroform phase was studied at 25[ddot]C. Distribution coefficients were measured as a function of HTTA concentration, K22DD concentration, and pH user radiotracer techniques. The synergistic species was determined from these studies to be M(TTA)3.K22DD. The results show that the presence of K22DD synergizes the extraction of each of the metals studied by factors of approximately lO⁴-1O⁵. Slightly larger organic phase stability constants were measured for the trivalent actinides relative to the trivalent lanthanides.     

SYNERGISTIC SOLVENT EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDE BY MIXTURES OF 1-PHENYL-3-METHYL-4-BENZOYL-PYRA2ALONE-5 AND NEUTRAL OXO-DONORS

ABSTRACT

The synergistic solvent extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am, has been studied with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP) and bis(2-ethylhexyl) sulphoxide (B2EHSO) or octyl(phenyl)-N,N-di isobutylcarbamoylmethylphosphine oxide (CMPO) in xylene. The extraction data have been analysed by both graphical and theoretical methods by taking into account aqueous phase speciation and all plausible complexes extracted into the organic phase. With HPMBP alone all the trivalent metal ions form M(PMBP)₃.HPMBP type self adducts. With B2EHSO as a neutral donor, the synergistic adduct species are M(PMBP)₃.B2EHSO and M(PMBP)₃.2 B2EHSO (where M = La, Eu, Lu and Am), whereas with CMPO as a neutral donor the only complex extracted into the organic phase is M(PMBP)₃.CMPO. The synergistic extraction constants of the above species which were deduced by non-linear regression analysis are found to increase monotonically with decreasing ionic radii of these metal ions.     

Selected Alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine Oxides as Extractants for Am(III) from Nitric Acid Media

Abstract

A new series of neutral bifunctional extractants, alkyl(phenyl)-N,N-dialkylcarbamoylmethylphosphine oxides, has been prepared and studied as extractants for Am(III) from nitric acid media. Two types of alkyl(phenyl)-N,N-dialkyl CMPO compounds were prepared, one containing N,N-diethyl groups and the other containing N,N-diisobutyl groups. The N,N-diethyl series contained hexyl(phenyl) and 6-methylheptyl(phenyl) derivatives, abbreviated HφDECMPO, and 6-MHφDECMPO, respectively. The N,N-diisobutyl series contained the n-octyl(phenyl), 6-methylheptyl(phenyl), and the 2-ethylhexyl(phenyl) derivatives, abbreviated OφD[IB]CMPO, 6-MHφD[IB]CMPO, and 2-EHφD[IB]CMPO, respectively. Third power extractant dependencies for the extraction of Am(III) from 0.5 and 3 M HNO₃ were obtained at low (<0.25 M) concentrations of extractant, but higher power dependencies were obtained above 0.25 M extractant from 3 M HNO₃. The HφDECMPO, 6-MHφDECMPO, 6-MHφD[IB]CMPO, and OφD[IB]CMPO [all 0.5 M in diethylbenzene (DEB)] are significantly better extractants than DHDECMPO for Am(III) from 1 to 6 M HNO₃. These same extractants have lower D _Am values than DHDECMPO at low acidities. HφDECMPO and OφD[IB]CMPO also have better selectivity for Am(III) over Fe(III) than DHDECMPO. HφDECMPO in DEB has a strong tendency toward the formation of a second liquid organic phase on extracting macroconcentrations of Nd(III) and U(VI) from 3 M HNO₃; however, this behavior is substantially diminished with the OφD[IB]CMPO and 6-MHφD[IB]CMPO compounds.     

Solvent Extraction and Spectrophotometric Studies on Synergistic Extraction of Plutonium(IV) by Mixtures of Thenoyltrifluoroacetone (HTTA) and Tri-n-butylphosphate (TBP) in Benzene

Abstract

The synergistic extraction of Pu(IV) from perchloric acid solutions into mixtures of thenoyltrifluoroacetone (HTTA) and tri-n-butylphosphate (TBP) in benzene was investigated by solvent extraction methods. The adduct responsible for synergism was found to be Pu(TTA)₄·TBP. The adduct formation between Pu(TTA)₄ and TBP in the benzene phase was also investigated by spectrophotometry. The equilibrium constants for the equilibria involved were obtained both by solvent extraction and by spectrophotometric methods.     

NMR STUDY OF LANTHANIDE(III) NITRATE-CMPO EXTRACTION SYSTEM (II)MOLECULAR MOVEMENT OF CMPO AND La(III)(NO3) 3-CMPO COMPLEX AND LIGAND-EXCHANGE REACTION FOR Eu(III)-CMPO AND Gd(III)-CMPO SYSTEMS

ABSTRACT

NMR( Nuclear Magnetic Resonance ) measurements were car ried out to study the molecular movement of CMPO and La(III)(NO₃) _3? CMPO complex and the ligand-exchange reaction for Eu(III) and Gd(III)-CMPO systems. From the ¹³C relaxation time measurement of La(NO₃) ₃ 3CMPO it was found that the T₁ value for the isobutyl CH and CH₂ carbons and the carbonyl carbon became considerably shorter on complexation, indicating that the carbonyl group participates in the bonding between CMPO and La³⁺ ion as well as the phosphoryl group. The numbers of CMPO molecules coordinated to Eu³⁺ and Gd³⁺ ions in CDCl₃ solution were estimated to be 3 and 2, respectively, in the presence of excess CMPO. The activation parameters for the ligand-exchange reaction were evaluated to be ΔH^* = 37.8±1.9[kJ/mol],ΔS^* = -59.9±6.5[J/molk? K] and ΔH^* = 41.3±1.6[kJ/mol], ΔS^* = -44.1±5.3[J/mol-K] for Eu(III)-CMPO and Gd(III)-CMPO systems, respectively. The independence of the exchange rate constants on the concentration of CMPO indicates that these ligand-exchange reactions seem to proceed through either a dissociative ( D ) mechanism or an interchange dissociative ( Id ) mechanism characterized by a stability constant of outer-sphere complex( KQ ) ≥ 100.     

Extraction Behavior of Am(III) and Eu(III) from Nitric Acid Medium in Tetraoctyldiglycolamide-Bis(2-Ethylhexyl)Phosphoric Acid Solution

The extraction behavior of Am(III) and Eu(III) in a solution of tetra-octyldiglycolamide (TODGA), bis(2-ethylhexyl)phosphoric acid (HDEHP), and n-dodecane (n-DD) was studied to understand the role of TODGA and HDEHP in the combined solvent system. The extraction behavior of these metal ions was compared with those observed in TODGA/n-DD and HDEHP/n-DD. The effect of various parameters such as concentrations of HNO₃, TODGA, and HDEHP on the distribution ratio of Am(III) and Eu(III) was studied. Synergistic extraction of both the metal ions observed at lower acidities (<2.0 M) was attributed to the involvement of TODGA and HDEHP for extraction. However, the extraction of Am(III) and Eu(III) in the combined solvent was comparable with that observed in TODGA at higher acidities. The slope analysis of the extraction data confirmed the involvement of both the extractants at all acidities investigated in the present study.     

SYNERGISTIC EXTRACTION STUDIES OF Am(III) AND Eu(III) FROM PERCHLORIC ACID WITH 4-BENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H- PYRAZOL-3-THIONE (BMPPT) AND TRI-n-OCTYLPHOSPHINE OXIDE (TOPO) IN BENZENE

The extraction of Am(III) and Eu(III) from aqueous HCIO₄ by BMPPT and TOPO in benzene was studied. The ligand BMPPT gave no detectable extraction in the ranges studied, but when BMPPT and TOPO were combined, a synergistic extraction was observed with a selectivity for Ara(III) over Eu(III) (K_dAm = 7.5, Am/Eu = 68, pH 3.0, 0.01 M [TOPO], 0.30 M [BMPPT]). The slope of the acid dependency for Eu and Am was 1.6 ± 0.1 and 2.7 ± 0.1, respectively, over the pH range of 2 to 3.The slope of the BMPPT dependency was 2.7 ± 0.1 and 2.8 ± 0.1 over a 2- and 20-fold concentration range for Eu and Am, respectively; the slope of the TOPO dependency was 2.0 ± 0.1 and 2.2 ± 0.1 for Am and Eu, respectively, over a 20-fold concentration range.     

Extraction of Trivalent Europium and Americium from Nitric Acid Solution with Bisdiglycolamides

Two bisdiglycolamides (BisDGAs) of N,N,N′′′,N′′′-tetrabutyl-N?,N′′-ethidene bisdiglycolamide (TBE-BisDGA) and N,N,N′′′,N′′′-tetrabutyl-N?,N′′-m-xylylene bisdiglycolamide (TBX-BisDGA) were synthesized. Their extraction behaviors of Eu(III) and Am(III), as well as nitric acid were investigated from nitric acid medium by using n-octanol as diluent. Nitric acid is extracted as the form of HNO₃·(BisDGAs)_0.6 by BisDGAs and the conditional acid uptake constants of TBE-BisDGA and TBX-BisDGA were 0.26 and 0.10, respectively. The distribution ratios of Eu(III) and Am(III) increased with the increase of nitric acid and extractant concentration, whilst decreased with temperature rise. TBX-BisDGA had a stronger extraction power for Eu(III) and Am(III) than TBE-BisDGA. Both of the extractants displayed a higher affinity toward Eu(III) than Am(III). In the examination of the acidity range from 0.5 to 5.0 M, a maximum separation factor SF_{Eu(III)/Am(III)} can reach 8.0 at 3.0 M HNO₃ for TBX-BisDGA; and 10 at 4.0 M HNO₃ for TBE-BisDGA, respectively. Slope analyses showed that Eu(III) and Am(III) are extracted as di-solvated species by TBX-BisDGA or TBE-BisDGA. The extraction mechanism was described and the apparent extraction equilibrium constant as well as Gibbs free energy change, enthalpy change and entropy change were presented. In addition, their Eu(III) complexes were analyzed by using infrared spectra.     

Actinide(III)/Lanthanide(III) Separation Via Selective Aqueous Complexation of Actinides(III) using a Hydrophilic 2,6-Bis(1,2,4-Triazin-3-Yl)-Pyridine in Nitric Acid

i-SANEX is a process for separating actinides(III) from used nuclear fuels by solvent extraction: Actinides(III) and lanthanides(III) are co-extracted from a PUREX raffinate followed by selective back extraction of actinides(III) from the loaded organic phase. This step requires a complexing agent selective for actinides(III). A hydrophilic sulfonated bis triazinyl pyridine (SO₃-Ph-BTP) was synthesized and tested for selective complexation of actinides(III) in nitric acid solution. When co-extracting Am(III) and Eu(III) from nitric acid into TODGA, adding SO₃-Ph-BTP to the aqueous phase suppresses Am(III) extraction while Eu(III) is extracted. Separation factors in the range of 1000 are achieved. SO₃-Ph-BTP remains active in nitric acid up to 2 mol/L. As a result of this performance, buffering or salting-out agents are not needed in the aqueous phase; nitric acid is used to keep the lanthanides(III) in the TODGA solvent. These properties make SO₃-Ph-BTP a suitable candidate for i-SANEX process development.     

Extraction of Lanthanides(III) and Am(III) by Mixtures of Malonamide and Dialkylphosphoric Acid

Abstract

N,N′‐dimethyl‐N,N′‐dioctylhexylethoxymalonamide, DMDOHEMA, and di‐n‐hexylphosphoric acid, HDHP, are the extractants of reference for the French DIAMEX–SANEX process for the separation of trivalent actinide ions from the lanthanide ions. In this work, the extraction of Eu³⁺ and Am³⁺ by the two extractants, alone or in mixtures, has been investigated under a variety of experimental conditions. The two cations are extracted by HDHP as the M(DHP · HDHP)₃ complexes with an Eu/Am separation factor of ～10. With DMDOHEMA, Eu³⁺ and Am³⁺ are extracted as the M(NO₃)₃(DMDOHEMA)₂ disolvate species with an Am/Eu separation factor of ～2. The metal distribution ratios measured with a mixture of the two reagents indicated that almost all lanthanides are extracted equally well. The extraction of Eu³⁺ and Am³⁺ by HDHP‐DMDOHEMA mixtures exhibits a change of extraction mechanism and a reversal of selectivity taking place at ～1 M HNO₃ in the aqueous phase. Below this aqueous acidity, HDHP dominates the metal extraction by the mixture, whereas DMDOHEMA is the predominant extractant at higher aqueous acidities. Some measurements indicated apparent modest antagonism between the two extractants in the extraction of Eu³⁺ and synergism in the extraction of Am³⁺. These data were interpreted as resulting from the formation in the organic phase of mixed HDHP‐DMDOHEMA species containing two HDHP and five DMDOHEMA molecules.     

Synergistic Extraction of Trivalent Actinides by Mixtures of 1-Phenyl-3-methyl-4-benzoyl-pyrazolone-5 and Neutral Oxo Donors

Abstract

The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and TBP or TOPO has been investigated in xylene at 30°C. With HPMBP alone, all four trivalent actinides form M(PMBP)₃· HPMBP-type self-adducts. Bk(III) shows an abnormally high extraction with HPMBP alone. With TBP or TOPO(S) as neutral donor, except in the Bk/HPMBP/TBP system where Bk(PMBP)₃· HPMBP·TBP was extracted, all metal ions were extracted as M(PMBP)₃·S and M(PMBP)₃·(S)₂ into the organic phase. The equilibrium constants (β₁, β₂, and K ₂ for the organic phase synergistic reactions have been calculated. The β₁, β₂ values for Bk(III)/HPMBP/TOPO system are much lower as compared to the corresponding values for other trivalent actinides. The reasons for this extraordinary behavior of Bk(III) have been discussed. The extraction behavior of the M(III)/HPMBP/S and the M(III)/HTTA/S systems has also been compared.     

THE EXTRACTION OF Am(III) FROM NITRIC ACID BY OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE - TRI-n-BUTYL PHOSPHATE MIXTURES

Abstract

The extraction behavior of Am(III) from nitric acid by octy1(phenyl)-N,N-diisobutylcarbamoyl methyphosphine oxides, OØD[IB]CMPO, in the presence of tributylphosphate, TBP, has been studied using diethylbenzene, decalin, and normal aliphatic hydrocarbon diluents. Relative to ØD[IB]CMPO alone, mixtures of TBP and OØD[IB]CMPO show a slight enhancement in the extraction of Am(III) from nitric acid solution above 2 M and a moderate decrease in extraction for lower acid concentrations. The net effect of TBP addition to OØD[IB]CMPO (as well as other selected carbamoyl methylphosphoryl extractants) is a relative insensitivity of the distribution ratio of Am(III) to HNO₃ concentration in the range of 0.5 M to 6 M and facilitated stripping of Am(III) with dilute acid. Since a continuous variation study of Am(III) extraction using mixtures of ØOD[IB]CMPO and TBP at a fixed total concentration revealed no evidence of a mixed complex, the TBP appears to be behaving primarily as a phase modifier

The most significant benefit gained from addition of TBP to ØD[IB]CMPO is the increased metal ion loading capacity and extractant compatibility with alicyclic and aliphatic diluents. The use of TBP to overcome phase compatibility with other bifunctional extractants of the carbamoylmethylphosphoryl type and the use of other phase modifiers with ØD[IB]CMPO have also been investigated.