Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS^? anions as compared to those formed by TODGA and NO₃^? ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.     

Water Soluble PDCA Derivatives for Selective Ln(III)/An(III) and Am(III)/Cm(III) Separation

The synthesis and solvent extraction behavior of dipicolinic acid (pyridine-2,6-dicarboxylic acid, PDCA) and their derivatives have been studied for possible use in selective back-extraction of actinides, especially americium. The extraction was performed from an organic phase containing a mixture of trivalent actinides and lanthanides pre-extracted with N,N,N’,N’-tetraoctyl diglycolamide (TODGA). The efficiency of the back-extraction was enhanced when the picolinate platform was used in a heterocyclic decadentate ligand called h₄tpaen. Beyond selective An/Ln extraction, the aqueous soluble h₄tpaen ligand seemed a potential reagent for an intra-group Am(III)/Cm(III) separation with a separation factor SF_Cm/Am of about 3.5.     

Extraction Behavior of Actinides and Metal Ions by the Promising Extractant,N,N,N′,N′-Tetraoctyl-3,6-dioxaoctanediamide (DOODA)

Abstract

The extraction of actinides, fission products, some non-nuclear elements, and nitric acid by N,N,N′,N′-tetraoctyl-3,6-dioxaoctanediamide (DOODA-C₈) in dodecane was extensively studied. Also studied was the extraction of HNO₃ and Nd(III) by the tetradodecyl analog of DOODA-C₈ in dodecane. Both extractants contain two ether oxygen atoms in the backbone chain carrying the two amide groups and can thus act as tetradentate ligands. The extractability of actinides decreases in the order Pu(IV) > U(VI), Am(III) > Np(V) in the extraction from nitric acid and Pu(IV) > Am(III) >> U(VI) in the extraction from perchloric acid. Ions of di-, tri-, tetra-, hexa-, and heptavalent metals strongly differ in the extractability by DOODA-C₈ but, except for lanthanides(III), there is no visible correlation of their distribution ratios with ionic radii. Due to the efficient extraction of actinides, weak extraction of fission products, and sufficient extraction capacity, DOODA-C₈ is a promising extractant for the recovery of minor actinides from high-level radioactive wastes.     

Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions with CMPO-Functionalized Ionic Liquid in Molecular Diluents

The extraction of microquantities of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions with CMPO-functionalized ionic liquid 1-[3[[(diphenylphosphinyl)acetyl]amino]propyl]-3-tetradecyl-1H-imidazol-3-ium hexafluorophosphate, CMPO-FIL(I) in molecular organic diluents has been studied. The effect of HNO₃ concentration in the aqueous phase and that of extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined. CMPO-FIL(I) demonstrates greater extraction ability towards Ln(III) than its neutral CMPO analog, diphenylphosphorylacetic acid N-nonylamide. This inner synergistic effect increases with a decreasing organic diluent polarity. The partition of CMPO-FIL(I) between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of Ln(III) ions in the extraction system.     

Solvent Extraction of Plutonium(IV), Uranium(VI), and Some Fission Products with Di-n-octylsulfoxide

Abstract

Extraction behavior of plutonium(IV), uranium(VI), and some fission products from aqueous nitric acid media with di-n-octylsulfoxide (DOSO) has been studied over a wide range of conditions. Both the actinides are extracted essentially completely, whereas fission product contaminants like Zr, Ru, Ce, Eu, and Sr show negligible extraction. The absorption spectra of sulfoxide extracts containing either Pu⁴⁺ or UO₂ ²⁺ indicate the species extracted from nitric acid into the organic phase to be Pu(NO₃)₄. 2DOSO and UO₂(NO₃)₂. 2DOSO, respectively. Extraction of these actinides decreases with increasing temperature, indicating the extraction to be exothermic. DOSO extracts plutonium and uranium better than di-n-hexylsulfoxide (DHSO) under all condition and is also more soluble in aromatic diluents than the latter. The effect of gamma radiation on the extraction properties of DOSO is found to be similar to that of DHSO.     

Extraction of lanthanides(III) from Perchlorate Solutions with Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides and Tetrabutyldiglycolamide

The solvent extraction of Ln(III) ions from perchlorate aqueous solutions into an organic phase containing neutral polyfunctional organophosphorus ligands R₂P(O)CH₂OCH₂C(O)NBu₂ R = Bu (I), R = Ph (II) and R₂P(O)CH₂OCH₂P(O)R¹₂ R = R¹ = Bu (III); R = Bu, R¹ = Ph (IV); R = R¹ = Ph(V) has been studied. Their extraction behavior was compared with that of tetrabutyldiglycolamide (TBDGA), tetrabutylmethylenediphosphine dioxide (VI), P,P-dibutyl-P’P’-diphenylmethylenediphosphine dioxide (VII), tetraphenylmethylenediphosphine dioxide (VIII), dibutyl-N,N-dibutylcarbamoylmethylphosphine oxide (IX) and diphenyl-N,N-dibutylcarbamoylmethylphosphine oxide (X). The extraction equilibrium was investigated, and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted with the studied extractants from perchlorate solutions as LnL₃(ClO₄)₃ complexes. In the NaClO₄ media, TBDGA was found to possess a higher extraction efficiency towards Ln(III) ions than other neutral donor ligands studied. A successive replacement of the C(O)NBu₂ groups in the diglycolamide extractant molecule by phosphoryl ones leads to a decrease in the extraction efficiency of Ln(III) ions. In the NaClO₄ media, compounds II, IV and V with phenyl radicals at the P(O) group demonstrate a lower extraction efficiency towards Ln(III) ions than their butyl-substituted analogs. In contrast, phenyl-substituted diphosphine dioxides VIII, VII and carbamoylmethylphosphine oxide (X) extract Ln(III) ions more effectively than their butyl-substituted analogs VI and IX. The extraction of Ln(III) ions from HClO₄ solutions is accompanied by HClO₄ interaction with neutral donor extractants, which leads to a decrease of the free extractant concentration in the organic phase. By this reason, an increase in the HClO₄ concentration higher than 0.1 M is accompanied by a decrease of the Ln(III) extraction with TBDGA. In the 3 M HClO₄ system, diphosphine dioxide VIII outperforms TBDGA at the Ln(III) extraction.     

Extraction of Actinide(III,IV, V,VI) Ions and TcO4 − by N,N,N′,N′‐Tetraisobutyl‐3‐Oxa‐Glutaramide

Abstract

The extraction behavior of U(VI), Np(V), Pu(IV), Am(III), and TcO₄ ^? with N,N,N′,N′‐tetraisobutyl‐3‐oxa‐glutaramide (TiBOGA) were investigated. An organic phase of 0.2 mol/L TiBOGA in 40/60% (V/V) 1‐octanol/kerosene showed good extractability for actinides (III, IV, V VI) and TcO₄ ^? from aqueous solutions of HNO₃ (0.1 to 4 mol/L). At 25°C, the distribution ratio of the actinide ions (D _An) generally increased as the concentration of HNO₃ in the aqueous phase was increased from 0.1 to 4 mol/L, while the D _Tc at first increased, then decreased, with a maximum of 3.0 at 2 mol/L HNO₃. Based on the slope analysis of the dependence of D _M (M=An or Tc) on the concentrations of reagents, the formula of extracted complexes were assumed to be UO₂L₂(NO₃)₂, NpO₂L₂(NO₃), PuL(NO₃)₄, AmL₃(NO₃)₃, and HL₂(TcO₄) where L=TiBOGA. The enthalpy and entropy of the corresponding extraction reactions, Δ_r H and Δ_r S, were calculated from the dependence of D on temperature in the range of 15–55°C. For U(VI), Np(V), Am(III) and TcO₄ ^?, the extraction reactions are enthalpy driven and disfavored by entropy (Δ_r H<0 and Δ_r S<0). In contrast, the extraction reaction of Pu(IV) is entropy driven and disfavored by enthalpy (Δ_r H>0 and Δ_r S>0). A test run with 0.2 mol/L TiBOGA in 40/60% 1‐octanol/kerosene was performed to separate actinides and TcO₄ ^? from a simulated acidic high‐level liquid waste (HLLW), using tracer amounts of ²³⁸U(VI), ²³⁷Np(V), ²³⁹Pu(IV), ²⁴¹Am(III) and ⁹⁹TcO₄ ^?. The distribution ratios of U(VI), Np(V), Pu(IV), Am(III) and TcO₄ ^? were 12.4, 3.9, 87, >1000 and 1.5, respectively, confirming that TiBOGA is a promising extractant for the separation of all actinides and TcO₄ ^? from acidic HLLW. It is noteworthy that the extractability of TiBOGA for Np(V) from acidic HLLW (D _Np(V)=3.9) is much higher than that of many other extractants that have been studied for the separation of actinides from HLLW.     

Feasibility of Using Di-Dodecyl-Di-Octyl Diglycolamide for Partitioning of Minor Actinides from Fast Reactor High-Level Liquid Waste

The unsymmetrical diglycolamide, di-dodecyl-di-octyl diglycolamide (D³DODGA) is a modifier-free extractant proposed for partitioning of trivalent actinides from nitric acid medium. D³DODGA has been evaluated for the feasibility of using it in the absence of a phase modifier, for the partitioning of minor actinides from fast reactor high-level liquid waste (FR-HLLW). The extraction behavior of various metal ions present in the simulated FR-HLLW was studied in a solution of 0.1 M D³DODGA/n-dodecane from nitric acid medium. The distribution ratio of about 20 metal ions was measured as a function of concentration of nitric acid and other interfering ion. The extraction was found to be strongly dependent on the oxidation state of the metal ion. The extraction of Am(III) from 3–4 M nitric acid medium was quantitative in a single contact. However, it was accompanied by the quantitative extraction of fission products such as trivalent lanthanides (Ln(III)), Y(III), and Zr(IV). The extraction of Sr(II), Pd(II), and Ru(III) in 0.1 M D³DODGA/n-dodecane was not insignificant, but quite low. The extraction of Ba(II), Ni(II), Mo(VI), and Fe(III) was marginal and the extraction of Co(II), Sb(III), Mn(II), and Cs(I) in 0.1 M D³DODGA/n-dodecane was negligible. Our results indicated that 0.1 M D³DODGA/n-dodecane is a promising candidate for the separation of trivalent actinides from fast reactor high-level liquid waste containing significant quantities of trivalent lanthanides and actinides.     

Extraction Properties of P(O)-Modified N-Aryl-Carbamoylmethylphosphine Oxides in Nitric Acid Media

Novel polyfunctional neutral organophosphorus compounds, P(O)-modified N-aryl- carbamoylmethylphosphine oxides, Ph₂P(O)CH₂C(O)NH-(o-C₆H₄)(CH₂)_n-P(O)Ph₂ and Ph₂P(O)CH₂C(O)NH-(m-C₆H₄)(CH₂)_n-P(O)Ph₂ (n = 1,2), were synthesized and studied as extractants for U(VI), Th(IV) and Ln(III) from HNO₃ solutions. The influence of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Introduction of an additional phosphoryl group into the phenyl substitutent at the nitrogen atom of diphenyl(N-phenylcarbamoylmethyl)phosphine oxide resulted in an increase of the efficiency of U(VI), Th(IV), Ln(III), and Re(VII) extraction.     

Formation, Characterization and Electrical Conductivity of Polycarbosilazane-Cu(II), -Ni(II) and -Cr(III) Chloride Metallopolymers

A series of transition metal-polycarbosilazane complexes have been prepared by the reaction of poly(N,N-bis(dimethylsilyl)ethylenediamine), [–Si(CH₃)₂NHCH₂CH₂NH–] _n , with Cu(II), Ni(II), and Cr(III) chloride. The resulting complexes were characterized by infrared (FT-IR) and UV-visible spectroscopy, magnetic susceptibility measurements, thermogravimetric analysis (TGA), and powder X-ray diffraction (XRD). The average chain-chain spacing in these materials were estimated from XRD data and found to be 6.88, 7.91, 7.09, and 6.33 Å in metal-free, Cu(II)-, Ni(II)-, and Cr(III)-containing polycarbosilazanes, respectively. DC electrical conductivity measurements showed that all these metal-polycarbosilazane complexes exhibit semiconductor behavior while the metal-free matrix is an insulator.     

Extraction of Lanthanides with N,N′‐Dimethyl‐N,N′‐diphenyl‐malonamide and ‐3,6‐dioxaoctanediamide

Abstract

The extraction properties of the trivalent lanthanides (Ln(III)) with the bidentate N,N′‐dimethyl‐N,N′‐diphenyl‐malonamide (MA) and the tetradentate N,N′‐dimethyl‐N,N′‐diphenyl‐3,6‐dioxaoctanediamide (DOODA) were investigated. These diamides formed by coupling two amide groups with methylene and/or ether groups are bidentate for the MA and tetradentate for the DOODA. By adding a previous data regarding the tridentate N,N′‐dimethyl‐N,N′‐diphenyl‐diglycolamide (DGA), these extraction results enabled us systematically study an effect of number of oxygen donor on its extraction behavior of Ln(III). The change in the distribution ratios (Ds) of Lu(III) with an increase in the HNO₃ concentration is greater than that of La(III) in both the MA and DOODA systems. Therefore, the relationship between the D and atomic number, i.e., the lanthanide pattern, changes with the HNO₃ concentration: the Ds decrease with an increasing atomic number at lower HNO₃ concentrations. The Ds of the lighter Ln(III) are similar to the Ds of the heavier Ln(III) at higher HNO₃ concentrations. The number of the extractant in the extracted species for La(III) and Lu(III) obtained from slope analysis at 4 M HNO₃ in the MA system are about 3, while those in the DOODA system are quite different, i.e., 2 for La(III) and 1.5–3 for Lu(III). The comparison of the extractability of Ln(III) by MA, DOODA, and DGA shows that the magnitude of the Ds is in the sequence of MA < DOODA ? DGA. This suggests the introduction of one ether oxygen atom to the principal chain in the diamides leads to a good extractability for the Ln(III) from HNO₃ solution.     

SYNERGISTIC EXTRACTION OF Eu(III) AND Am(III) BY THENOYLTRIFLUOROACETONE AND NEUTRAL DONOR EXTRACTANTS: (CARBAMOYLMETHYL)PHOSPHINE OXIDE AND 2,6-BIS((DIPHENYLPHOSPHINO)METHYL)PYRIDINE N,P, P-TRIOXIDE

ABSTRACT

Solvent extraction of Eu(III) and Am(III) from weakly acidic solutions with octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and 2,6-bis((diphenylphosphino)methyl)pyridine N, P, P-trioxide (NOPOPO) in 1,2-dichloroethane was studied on a comparative basis. NOPOPO was found to exhibit unusually high extractability for Eu(III) and Am(III), probably due to its trifunctional nature, sufficient steric flexibility and basicity of the functional groups. Both CMPO and NOPOPO demonstrated synergistic effects in extraction of Eu(III) and Am(III) when used in combination with thenoyltrifluoroacetone (HTTA). However, the stoichiometry of the extracted species with CMPO/HTTA and NOPOPO/HTTA was different under similar experimental conditions. The extractant dependencies of the synergistic extractions suggest that the extracted species are the adduct complexes, M(ClO₄)(TTA)₂(CMPO)₂ and M(ClO₄)₂(TTA)(NOPOPO)₂, respectively. It was also observed that CMPO and CMPO/HTTA in dichloroethane extracted Eu(III) and Am(III) equally well, with very similar extraction constants. However, NOPOPO and NOPOPO/HTTA in dichloroethane demonstrated a slight preference for Eu(III) over Am(III), with the extraction constants for Eu(III) more than one order of magnitude higher than that for Am(III).     

Extraction of Lanthanides(III), U(VI), and Th(IV) from Nitric Acid Solutions with 1,5-N,N'-Bis[(diphenylphosphoryl)acetylamino]pentanes

Novel polyfunctional neutral organophosphorus ligands, namely 1,5-N,N'-bis[(diphenylphosphoryl)acetyl(alkyl)amino]pentanes [Ph₂P(O)CH₂C(O)NR]₂(CH₂)₅ (Ia, R = C₆H₁₃; Ib, R = CH₃), were studied as extractants for Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, and U from nitric acid solutions. The effect of both HNO₃ concentration in the aqueous phase and that of the extractant in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined by the slope analysis method. Compared with the related bisaminopentane [Ph2P(O)CH₂C(O)NH]₂(CH₂)₅ (Ic), the replacement of hydrogen atoms at the amide nitrogens by alkyl radicals (compounds Ia,b) leads to an increase of metal ions extraction. Bis-CMPO ligands Ia-c were found to possess higher extraction efficiency towards U(VI), Th(IV), and Ln(III) than their monophosphorylated analogue Ph₂P(O)CH₂C(O)N(C₄H₉)₂.     

Extraction Behavior of Ln(III) Ions by T2EHDGA/n-Dodecane from Nitric Acid and Sodium Nitrate Solutions

The diglycolamide extractant T2EHDGA has proven to be promising for the separation of lanthanides and minor actinides in high-level nuclear waste reprocessing. This neutral extractant has shown significant extraction capacity for HNO₃ into the nonpolar organic phase, along with hyper-stoichiometric nitrate dependence on extraction of trivalent f-elements. The transport behavior of T2EHDGA/n-dodecane toward trivalent lanthanides is not well understood. This work found a significant increase in distribution ratios for Eu(III) extracted from aqueous HNO₃ media compared with that from NaNO₃. The extraction of Eu(III) from HNO₃ results in a different thermodynamic product than predicted by classic solvent extraction of 3:1 ligand–metal complex as observed with NaNO₃ in FTIR and UV-vis spectroscopy. Experimental distribution measurements in conjunction with mass-action modeling using the solvent extraction modeling program SXLSQI suggest participation of 1 to 2 HNO₃ molecules in the Eu(III)/T2EHDGA complex upon extraction from HNO₃ media, indicative of a mechanism change responsible for the enhanced extraction behavior toward lanthanides in the presence of HNO₃.     

Rhodium catalysed hydroformylation using diphenylphosphine functionalised carbosilane dendrimers

Diphenylphosphine functionalised carbosilane dendrimers Si((CH₂)_nSi(CH₃)₂(CH₂PPh₂))₄ (n=2,3; generation 1–3) and Si((CH₂)_nSi(CH₃)(CH₂PPh₂)₂)₄ (n=2,3; generation 1–2) have been synthesised and used as ligands in the rhodium catalysed hydroformylation of 1-octene. The activity of the system depends on the size and flexibility of the dendrimeric ligand.     

Synthesis and dipole-dipole interaction-induced mesomorphic behavior of poly(oxyethylene)s containing (n-octylsulfonyl)alkylthiomethyl or (n-octylsulfonyl)alkylsulfonylmethyl side groups

Two series of ((n-octylsulfonyl)alkylthio)methyl-substituted poly(oxyethylene)s ((-OCH₂CHR-)_n, where R=-CH₂S(CH₂)_MSO₂(CH₂)₈H) (OTP-M, M=3,4,5,6,7,9,12), and ((n-octylsulfonyl)alkylsulfonyl)methyl-substituted poly(oxyethylene) ((-OCH₂CHR-)_n, where R=-CH₂SO₂-(CH₂)_MSO₂(CH₂)₈H) (OSP-M, M=3,4,5,6,7,9,12), were synthesized using polymer analogous reactions from poly(epichlorohydrin) to study the effect of dipole-dipole interactions of the sulfone groups (SO₂) on the ordered structures of the poly(oxyethylene) derivatives. The ordered phases of these polymers were studied using polarizing optical microscopy, X-ray diffraction, differential scanning calorimetry and IR spectroscopy. OTP-Ms and OSP-3 showed ordered phases originated from side chain crystallization, while OSP-Ms except OSP-3 showed liquid crystalline behavior. The poly(oxyethylene) derivatives with M=5,6,7 had double-layer structures, while the polymers with M=3,4,9,12 had intercalating double-layer structures at room temperature. The layer structures of the poly(oxyethylene) derivatives were found to be affected by the positions of the side chain sulfone groups which can generate strong dipole-dipole interactions.     

Preparation and properties of functionalized polyorganosiloxanes

A series of linear functionalized polyorganosiloxanes of the type Me₃SiO[MeSiO(CH₂)_nR]_x(Me₂SiO)_ySiMe₃, where n = 2, R = —(CH₂)NMe₂; n = 1, R = —(CH₂)OEt; n = 4, R = —(CH₂)COOEt; n = 3, R = —(CH₂)Me, have been prepared and characterized. Functional group loadings of ∼4 mol % (x = 1, y = 25), ∼11 mol % (x = 3, y = 23), and ∼30 mol % (x = 8, y = 18) were obtained by reacting commercially available copolymers Me₃SiO(MeSi{H} O)_x(Me₂SiO)_ySiMe₃ with the appropriate ratios of_x:_y, with the required quantities of HO(CH₂)_nR, using dichloro(1,5-cyclooctadiene)platinum(II) as catalyst. Amine, ether, ester, and alkyl functionalized siloxanes were obtained in good yields after purification, and each fluid polymer has been characterized by ¹H and ¹³C-nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectral measurements, elemental analysis, viscosity, surface tension, and density measurements. The functionalized polymers exhibit Newtonian behavior over the range of shear rates 0.4–79.4 s⁻¹, and significant viscosity enhancements were observed for all functionalized polymers compared with poly(dimethylsiloxane) fluids of similar chain lengths. The functionalized siloxanes exhibited in almost all cases an increase in both viscosity and density as the functional group loading increased. The surface tensions of the polymers have also been determined and lie within the range 18.8–22.3 mN m⁻¹. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 808–817, 2001     

Synergistic Solvent Extraction of Lanthanides(III) with Mixtures of 4-benzoyl-3-methyl-1-phenylpyrazol-5-one and Some Novel Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides

The solvent extraction of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from weak acidic hydrochloric acid solutions into an organic phase containing 4-benzoyl-3-methyl-1-phenylpyrazol-5-one (HP) and neutral tridentate organophosphorus ligands R₂P(O)CH₂OCH₂C(O)NBu₂ R = Bu (I), R = Ph (II) and R₂P(O)CH₂OCH₂P(O)R¹₂ R = R¹ = Bu (III); R = Bu, R¹ = Ph (IV); R = R¹ = Ph(V) has been studied. A considerable synergistic effect was observed in the presence of HP in the organic phase containing tetraoctyldiglycolamide (TODGA) and neutral organophosphorus ligands I - V. A successive replacement of C(O)NAlk₂ groups in the diglycolamide extractant molecule by P(O)Ph₂ groups leads to an increase in the extraction efficiency of Ln(III) ions when toluene was used as diluent. Phosphoryl-containing podand I possess a higher extraction efficiency towards Ln(III) ions than TODGA. The extraction equilibrium was investigated and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted as LnLP₃ and LnL₂P₃ complexes with mixtures of HP and I in toluene from weak acidic solutions.     

SYNERGISTIC SELECTIVE EXTRACTION OF ACTINIDES(III) OVER LANTHANIDES FROM NITRIC ACID USING NEW AROMATIC DIORGANYLDITHIOPHOSPHINIC ACIDS AND NEUTRAL ORGANOPHOSPHORUS COMPOUNDS

ABSTRACT

New aromatic dithiophosphinic acids (R₂PSSH) with R = C₆H_5?, ClC₆H_4?, FC₆H_4? and CH₃C₆H_4? were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R₂PSSHS and neutral organophosphorus compounds. There was no detectable extraction when R₂PSSHS were used alone as extractants for either Am(III) or Eu(III) (D_AM,EU.< 10^?3) under the experimental conditions used in this study. High separation factors (D_AM/D_EU > 20) with D_AM > 1 were achieved in the nitric acid range 0.1-1 mol/L by means of a synergistic mixture of bis(chloro-phenyl)dithiophosphinic acid + tributylphosphate (TBP), irioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 10⁶ Gy absorbed γ-doses) of the extractants was also demonstrated.     

New Bitopic Ligands for the Group Actinide Separation by Solvent Extraction

Abstract

The synthesis and evaluation of solvent extraction performance of N,N,N′,N′-tetraalkyl-6,6″-(2,2′:6′,2″-terpyridine)diamides and N,N′-diethyl-N,N′-diphenyl-6,6″-(2,2′:6′,2″-terpyridine)diamide are reported here. These new bitopic ligands were found to extract actinides in different oxidation states (U(VI), Np(V and VI), Pu(IV), Am(III), and Cm(III)) from 3 M nitric acid. The presence of three soft nitrogen donors led to the selective extraction of actinides(III) over lanthanides(III) (Ce, Eu) and the presence of two amide functional groups grafted to the terpyridine unit allowed the extraction to occur from a highly acidic medium by minimizing the basicity of the ligand. Ligands bearing long alkyl chains (C4 and C8) or phenyl groups showed increased performances in a polar diluent like nitrobenzene.