N-diisobutylcarbamoylmethylphosphine Oxide Research Articles

Technology for reprocessing mother liquor and washing solution from crystalization purification of HTGR SNF

The extractants diphenyl-N,N-dioctylcarbamoylmethylphosphine oxide and diphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide for the processing of spent fuel were tested. The conditions for extraction and separation of uranium and TPE–REE were determined. A technological scheme was proposed for processing spent nuclear fuel from high-temperature gas-cooled reactors. During dynamic testing, at least 99.9% of uranium and plutonium and at least 99.5% of americium and rare earth elements were extracted. The TPE + REE and U+Pu fractions were isolated. The U+Pu fraction contained approximately 5% Am, while the TPE + REE fraction had less than 0.1% U and Pu.

Probing activated radioprotection of simple hydrophilic phosphonic acids in aqueous solution

Previous investigation into the radiation chemistry of the ligand octylphenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and its analogues demonstrated their ability to undergo activated radioprotection in an organic solvent – a feature most advantageous for spent nuclear fuel reprocessing scenarios. This phenomenon was dependent on these organophosphorus compounds forming a sacrificial complex involving extracted nitric acid and the presence of an adjacent phenylphosphine oxide motif in the molecule. However, the hydrophobic nature of these compounds prevented elucidation of which components were essential for activated radioprotection; for example, does the phenylphosphine oxide motif only require protonation, or simply the presence of complexed nitrate anion(s), or both? To begin to address these questions, we report on the effect of dissolved nitrate on the radiation chemistry of a series of simple hydrophilic phosphonic acids (methyl, ethyl, phenyl, and benzyl) in aqueous solution. An extensive suite of gamma irradiations supported by high performance liquid chromatography and nuclear magnetic resonance techniques was used to demonstrate that all four compounds were unable to undergo activated radioprotection. Although some nitrate protection was observed, this was attributed to changes in the available suite of radiolysis products, and not to the formation of nitrate-phosphonic acid sacrificial complexes. The absence of activated radioprotection and evidence for the formation of a [PhPA•NO3−] complex further supports the necessity of complex formation to activate the radioprotection mechanism.

Microanalysis of silica-based adsorbent for effective recovery of radioactive elements

ABSTRACTFor effective recovery of radioactive elements by adsorbents using polymer-immobilized silica (SiO2-P) supports, the microstructure of SiO2-P particles impregnated with octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide as extractants and their change with the crosslinking degree of polymer (CDP) were investigated using scanning transmission X-ray microscopy (STXM) and extended X-ray absorption fine structures (EXAFS) analyses; further, their relation with adsorption/elution behavior was discussed. The results of STXM analysis suggested that the polymer is distributed within several hundred nanometers of the pore surface, and its distributions are spread by the increase of CDP. In addition, the capture of impurity molecules such as H2O by polymers with high CDP was indicated. EXAFS analyses showed that the local structure around adsorbed europium ions is similar irrespective of the CDP. The adsorption/elution tests demonstrated that a higher CDP inhibited the elution of adsorbed europium ions from the adsorbent.

Thermodynamic Insight into the Solvation and Complexation Behavior of U(VI) in Ionic Liquid: Binding of CMPO with U(VI) Studied by Optical Spectroscopy and Calorimetry.

The complexation of U(VI) with octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO, denoted as L) in ionic liquid (IL) C4mimNTf2 was investigated by UV-vis absorption spectrophotometry and isothermal titration calorimetry. Spectro-photometric titration suggests that three successive complexes, UO2Lj2+ (j = 1-3), formed both in "dry" (water content < 250 ppm) and "wet" (water content ≈ 12 500 ppm) ionic liquid. However, the thermodynamic parameters are distinctly different in the two ILs. In dry IL, the complexation strength between CMPO and U(VI) is much stronger, with stability constants of the respective complexes more than 1 order of magnitude higher than that in wet IL. Energetically, the complexation of U(VI) with CMPO in dry IL is mainly driven by negative enthalpies. In contrast, the complexation in wet IL is overwhelmingly driven by highly positive entropies as a result of the release of a large amount of water molecules from the solvation sphere of U(VI). Moreover, comparisons between the fitted absorption spectra of complexes in wet IL and that of extractive samples from solvent extraction have identified the speciation involved in the extraction of U(VI) by CMPO in ionic liquid. The results from this study not only offer a thermodynamic insight into the complexation behavior of U(VI) with CMPO in IL but also provide valuable information for understanding the extraction behavior in the corresponding solvent extraction system.

Understanding the complexation of the Eu3+ ion with TODGA, CMPO, TOPO and DMDBTDMA: Extraction, luminescence and theoretical investigation

A comparative study was carried out to understand the complexation behavior of the Eu3+ ion with important reagents, namely TODGA (N,N,N′,N′ tetraoctyl diglycolamide), CMPO (octyl (phenyl)-N, N-diisobutyl carbamoyl methyl phosphine oxide), DMDBTDMA (dimethyl dibutyl tetradecyl malonamide) and TOPO (tri-n-octyl phosphine oxide) in dodecane, used for the separation of actinides and lanthanides from lab and nuclear high-level wastes, by experimental (extraction and luminescent) and theoretical means. A solvent extraction study revealed the metal–ligand stoichiometry as 1:3 for all the systems with the extraction efficiency TOPO>CMPO>TODGA>DMDBTDMA at 1M HNO3, while TODGA>CMPO>DMDBTDMA>TOPO at 3M HNO3. A luminescence investigation revealed the presence of single species in the extracted complex for all the systems, with no inner sphere water molecules for all the systems except for DMDBTDMA which had one inner sphere water molecule. The high intensity of the 5D0–7F2 transition revealed the presence of Eu3+ ions in an asymmetric environment with the local point group symmetry C3v for the TODGA and DMDBTDMA complexes, compared to C3h symmetry for the CMPO and TOPO complexes. Judd–Offelt parameters, radiative, non-radiative lifetimes, branching ratio, transition probabilities and quantum efficiencies for all the complexes were estimated and compared. Three O-donor atoms from each TODGA molecule coordinated to the Eu3+ ion in the first coordination sphere, while three CMPO units were found to be coordinated in a monodentate fashion. For the Eu-TOPO complex, three O donor atoms from each of the three TOPO molecules and six O donor atoms from three nitrate ions were coordinated. Out of three DMDBTDMA ligands, one was found to be coordinated in a bidentate mode, whereas two were in a monodentate mode, along with three nitrate ligands bonding in a monodentate fashion.

The Radiation Chemistry of CMPO: Part 2. Alpha Radiolysis

Octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in dodecane was subjected to α-irradiation using a He-ion beam, 244 Cm isotopic α-rays, and He and Li ions created by the n,α reaction of 10B in a nuclear reactor. Post-irradiation samples were analyzed for the radiolytically-induced decrease in CMPO concentration, the appearance of degradation products, and their Am solvent extraction distribution ratios. The –G CMPO-value for the radiolytic degradation of CMPO was found to be very low compared to values previously reported for γ-irradiation. Additionally, isotopic irradiation to absorbed α-doses as high as 600 kGy in aerated solution had no effect on Am solvent extraction or stripping. The main CMPO radiolysis products identified in He-ion beam irradiated samples by ESI-MS include amides, an acidic amide, and amines produced by bond rupture on either side of the CMPO carbonyl group. Deaerated samples irradiated using the reactor in the absence of an aqueous phase, or with a dilute nitric acid aqueous phase showed small but measurable decreases in CMPO concentration with increasing absorbed doses. Higher concentrations of nitric acid resulted in lower decomposition rates for the CMPO. The radio-protection by dissolved oxygen and nitric acid previously found for γ-irradiated CMPO also occurs for α-irradiation. This suggests that similar free-radical mechanisms operate in the high-LET system, but with lower degradation yields due to the lower overall radical concentrations produced.

The Radiation Chemistry of CMPO: Part 1. Gamma Radiolysis

Octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) was irradiated using 60Co γ-rays, and post-irradiation samples were analyzed for the decrease in CMPO concentration, the appearance of degradation products, and the effects on americium solvent extraction. The –G-value for the radiolytic degradation of CMPO depends on the presence of nitric acid and oxygen during irradiation, with both providing protection from radiolytic degradation. The –G-value does not depend on the γ-ray dose rate or the CMPO concentration. Effects on solvent extraction performance were independent of the change in CMPO concentration, but rather related to the nature of the degradation products. The main products were identified by ESI-MS and were different for irradiation in the presence of nitric acid.

Interaction of hydrated protons with octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO): NMR and theoretical study

Interaction of octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO, the 'classical' rare metal extraction agent) with fully ionized hydrated protons (HP) was studied in acetonitrile-d(3) using (1)H, (13)C, (31)P NMR, PFG NMR and magnetic relaxation. The experimental results were confronted with high-precision ab initio DFT calculations. Relative chemical shifts of NMR signals of CMPO (0.01 mol/L) under the presence of HP in the molar ratio β = 0-2.0 mol/mol show binding between CMPO and HP. Self-diffusion measurements using (1)H PFG NMR demonstrate that larger complexes with higher content of CMPO are generally formed at β < 0.75. Analyzing the collective dependence of (13)C and (31)P NMR chemical shifts on β by the use of program LETAGROP, we obtained very good fitting for the assumed coexistence of two complexes (CMPO)(2)·HP (C(2)) and CMPO.HP (C(1)). The logarithms of the respective stabilization constants log K(i) were found to be 7.518 (C(2)) and 4.581 (C(1)). The system dynamics was studied by measuring the transverse (1)H NMR relaxation using CPMG sequence with varying delays t(p) between the π pulses in the mixtures with β = 0.4-0.8. The following exchange correlation times were obtained: τ(10) = 2.35 × 10(-5), τ(20) = 0.82 × 10(-4), τ(21) = 0.45 × 10(-3) s. The DFT calculations support the conclusion that the complexes C(1) and C(2) are the main species in the mixtures of CMPO with HP. They also agree with the NMR and FTIR observation that the main site to which H(3) O(+) is bound is the P=O group, whereas the amide group does not form a strong bond with the ion when excess water molecules are present.

Solvent extraction of europium and americium into phenyltrifluoromethyl sulfone by using synergistic mixture of hydrogen dicarbollylcobaltate and “classical” CMPO

Extraction of microamounts of europium and americium by a phenyltrifluoromethyl sulfone (FS 13) solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (“classical” CMPO, L) has been investigated. The equilibrium data have been explained assuming that the complexes \( {\text{HL}}_{{}}^{ + } \), \( {\text{HL}}_{2}^{ + } \), \( {\text{ML}}_{ 2}^{3 + } \), \( {\text{ML}}_{ 3}^{3 + } \) and \( {\text{ML}}_{ 4}^{3 + } \) (M3+ = Eu3+, Am3+) are extracted into the organic phase. The values of extraction and stability constants of the cationic complex species in FS 13 saturated with water have been determined. It was found that the stability constants of the corresponding complexes \( {\text{EuL}}_{n}^{3 + } \) and \( {\text{AmL}}_{n}^{3 + } \), where n = 2, 3, 4 and L is “classical” CMPO, in water-saturated FS 13 are comparable.

Extraction of Microamounts of Calcium and Strontium into Nitrobenzene by Using Hydrogen Dicarbollylcobaltate in the Presence of “Classical” CMPO

Abstract Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (“classical” CMPO, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL2 +, CaL2+, CaL2 2+, CaL3 2+, SrL2 2+, SrL3 2+ and SrL4 2+ are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.

Removal of Pd(II), Zr(IV), Sr(II), Fe(III), and Mo(VI) from simulated high level liquid waste by extraction chromatography utilizing the macroporous silica-based polymeric materials

To eliminate a few specific elements from highly active liquid waste (HLW), two macroporous silica-based N, N, N′, N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) and octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) impregnated polymeric composites, TODGA/SiO 2-P and CMPO/SiO 2-P, were synthesized. It was done by an advanced vacuum sucking technique through impregnation of the chelating agents into the pores of SiO 2-P particles support. The partitioning of Sr(II), Pd(II), Zr(IV), Mo(VI), and Cs(I) from a 3.0 M HNO 3 solution containing some typically simulated fission and non-fission products Ru(III), Rb(I), Fe(III), Na(I), K(I), and Ba(II) was performed at 298 and 323 K, respectively. In the first column packed with TODGA/SiO 2-P, Sr(II), Pd(II), and Zr(IV) were adsorbed and eluted effectively by 0.01 M HNO 3, 0.05 M DTPA-pH 2.5, and 0.5 M oxalic acid, respectively, while others showed very weak or almost no adsorption and flowed into effluent along with 3.0 M HNO 3. Cs(I), Fe(III), and Mo(VI) containing effluent was then applied to the second column packed with CMPO/SiO 2-P. Fe(III) and Mo(VI) were found to be adsorbed together and eluted utilizing 0.05 M DTPA-pH 2 at 323 K. The effective partitioning of Fe(III) was of great benefit to the evaporation, concentration, and finally geological disposal of HLW. The separation of Sr(II) and Mo(VI) was useful for the vitrification of HLW due to the Sr heat generator property and low solubility of Mo oxides in molten glass materials. Cs(I) can be separated by a novel silica-based 1,3-[(2,4-diethyl-heptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) impregnated polymeric composite (Calix[4]arene-R14/SiO 2-P). In terms of the results obtained, a highly specific partitioning process of Fe(III) and some specific fission products Sr(II), Pd(II), Zr(IV), Cs(I), and Mo(VI) from a simulated HLW by extraction chromatography was proposed.

Removal of Actinides from Acidic Solution via Carrier-Mediated Facilitated Transport Across Mesoporous Substrates with Nanoengineered Surfaces: Thiol Self-Assembled Monolayers with D(tBu)ΦD(iBu)CMPO Ligands

:The surface engineering of polycarbonate track-etched (PCTE) membranes was performed to create a permselective membrane for the removal of trace levels of fission products and transuranic metals from acidic streams. Electroless gold deposition was used to place a gold coating on the PCTE substrates. The gold coating was subsequently functionalized through the formation of a self-assembled monolayer of dodecanethiol, which was further functionalized with di-(4-t-butylphenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide. Transport characteristics of metal ions, 137Cs, 85Sr, 241Am, and 239Pu, were obtained using a two-compartment diffusion apparatus. Transport studies showed that the functionalized membranes enhance the transport rates of 241 Am and 239Pu and inhibit the transport of 137Cs and 85Sr. Diffusion studies over an extended time revealed that the facilitated transport characteristics of 239Pu through the ligand-coated membranes are dependent on nitrate anion concentrations in the feed and sink cells.

Development of polymer inclusion membranes based on cellulose triacetate: carrier-mediated transport of cerium(III)

Polymer inclusion membranes (PIMs) consisting of cellulose triacetate (CTA) as a polymer matrix, 2-nitrophenyl n-octyl ether (NPOE) as a solvent and octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) or N, N, N′, N′-tetraoctyl-3-oxapentanediamide (TODGA) as a carrier were developed, and the facilitated transport of cerium(III) ions using the PIMs was investigated experimentally. It was observed that the present PIMs were very effective to transport cerium(III) ions from the feed phase to the strip phase. The transport rate was strongly influenced by the experimental conditions such as the solvent/polymer ratio, the operating temperature, the membrane thickness, the carrier concentration and the feed concentration. The experimental results indicated that the transport was controlled by the diffusion of the ion-carrier complex in the membrane.

Uranyl coordination environment in hydrophobic ionic liquids: an in situ investigation.

Different inner-sphere coordination environments are observed for the uranyl nitrate complexes formed with octyl-phenyl-N,N-diisobutylcarbamoylmethylphosphine oxide and tributyl phosphate in dodecane and in the hydrophobic ionic liquids (ILs) [C(4)mim][PF(6)] and [C(8)mim][N(SO(2)CF(3))(2)]. Qualitative differences in the coordination environment of the extracted uranyl species are implied by changes in peak intensity patterns and locations for uranyl UV-visible spectral bands when the solvent is changed. EXAFS data for uranyl complexes in dodecane solutions is consistent with hexagonal bipyramidal coordination and the existence of UO(2)(NO(3))(2)(CMPO)(2). In contrast, the complexes formed when uranyl is transferred from aqueous nitric acid solutions into the ILs exhibit an average equatorial coordination number of approximately 4.5. Liquid/liquid extraction results for uranyl in both ILs indicate a net stoichiometry of UO(2)(NO(3))(CMPO)(+). The concentration of the IL cation in the aqueous phase increases in proportion to the amount of UO(2)(NO(3))(CMPO)(+) in the IL phase, supporting a predominantly cation exchange mechanism for partitioning in the IL systems.

Studies on the Separation of Minor Actinides from High-Level Wastes by Extraction Chromatography Using Novel Silica-Based Extraction Resins

To develop an advanced partitioning process by extraction chromatography using a minimal organic solvent and compact equipment to separate minor actinides such as Am and Cm from nitrate acidic high-level waste (HLW) solution, several novel silica-based extraction resins have been prepared by impregnating organic extractants into the styrene-divinylbenzene copolymer, which is immobilized in porous silica particles (SiO2-P). The extractants include octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO), di(2-ethylhexyl)-phosphoric acid (HDEHP), and bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301). Compared to conventional polymer-matrix resins, these new types of extraction resin are characterized by rapid kinetics and significantly low pressure loss in a packed column.The results of separation experiments revealed that trivalent actinides and lanthanides can be separated from other fission products, such as Cs, Sr, and Ru in simulated HLW solution containing concentrated nitric acid by extraction chromatography using a CMPO/SiO2-P resin-packed column. Satisfactory separation between Am(III) and a macro amount of lanthanides from simulated HLW solution with pH 4 was achieved by using a newly purified Cyanex 301/SiO2-P resin. However, the Am(III) separation was very sensitive to the purity of Cyanex 301, and the improvement of its stability is an important task for practical utilization.

NMR study of lanthanide (III) nitrate complexes in CMPO/TBP systems

The coordination properties of the lanthanide (Ln) (Ln; La∼Eu) nitrate complexes in octyl (phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO)/tributylphosphate (TBP) systems were investigated using NMR techniques. In Ln/CMPO/TBP systems where the mole ratio of CMPO to the Ln ion ([CMPO]/[Ln]) is under 3, 13C- and 31P-NMR spectra show that several kinds of complexes are produced in which both CMPO and TBP coordinate to the Ln (III) ion. The contribution of CMPO to the coordination with the Ln (III) ion increases with [CMPO]/[Ln], and in the case where [CMPO]/[Ln]>3, only CMPO coordinates to the Ln (III) ion directly in the bidentate manner. The distances from the Ln (III) ion to phosphoryl P or carbonyl C are estimated to be 3.3∼4.3 Å. In this system, TBP is absent from the first coordination sphere of the Ln (III) ion, but decreases the exchange rate constants, activation enthalpy and activation entropy in the CMPO exchange reaction between the free and coordinated states by the action from beyond the first coordination sphere.

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).

Synthesis and Characterization of Plutonium(IV), Uranium(VI), Morium(IV) and Neodymium(III) Nitrate Complexes with Bidentate Organophosphorus Ligands

Solid adducts of actinide and lanthanide nitrates of the type [M(NO3(X)y], where M = Pu4+, UO2 2+, Th4+ and Nd3+; n = 2 for UO2 2+, 3 for Nd3+ and 4 for Th4+ and Pu4+; y = 1 for UO2 2+, 1.5 for Th4+ and 2 for Pu4+ and Nd3+; and X = dihexyl N, N-diethylcarbamoylmethylphosphonate (DHDECMP) or octyl (phenyl) (N, N-diisobutylcarbamoylmethyl) phosphine oxide (CMPO), were isolated and purified by a solvent extraction route from benzene. These compounds have been characterized by elemental analyses, and their melting points. The IR and visible absorption spectra of these complexes indicate that they are O-bonded. The extract ant in all the complexes acts as a bidentate ligand whereas the nitrate ion acts as a bidentate group in the Th4+, UO2 2+ and Nd3+ complexes but in the case of the Pu4+ complexes one of the nitrate ions probably is acting as monodentate ligand. A slight upfield shift of phenyl, methyl and methylene protons around phosphoryl and carbamoyl oxygens in the 1H NMR spectra of the uranium, thorium and neodymium complexes, as compared to the pure ligand, further reaffirms the bidentate nature of CMPO. Thermal studies of the uranyl and thorium complexes are reported.

Preparation and Characterization of New Chelating Resin Containing n-Octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine Oxide (CMPO) as a Functional Group

(1998). Preparation and Characterization of New Chelating Resin Containing n-Octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine Oxide (CMPO) as a Functional Group. Journal of Nuclear Science and Technology: Vol. 35, No. 2, pp. 163-165.

Trivalent f-Element Intra-group Separation by Solvent Extraction with CMPO-complexant System

For trivalent actinide and lanthanide separation, the solvent extraction system which employs neutral bifunctional extractant n-octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and aminopolyacetic acid was investigated. The system is based on CMPO-tri-n-butylphosphate (TBP) mixed solvent and diethylenetriaminepentaacetic acid (DTPA)-sodium nitrate solution. The separation is achieved by complexing trivalent actinide preferentially with DTPA in aqueous phase and extracting lanthanide into organic phase. Mutual separation between light lanthanide, Am and Cm was mainly governed by complex formation with DTPA. The acidity is most affecting parameter for partitioning and its increase results in decrease of distribution ratio. For selective stripping of trivalent actinide from 0.2 M CMPO—1.0 M TBP in n-dodecane at room temperature, 0.05 M DTPA and 2–4 M sodium nitrate solution (pH 2) is useful. From the observed distribution behavior, a basic flow sheet which is composed of four steps was proposed. In batchwise experiments with radioactive nuclides, separation factor of larger than 13 and 27 for Ce/Am and Cm/Eu, respectively, were obtained and the applicability of the system was indicated.