Barbara F. Smith

THE USE OF SOFT DONOR LIGANDS, 4-BENZOYL-2,4-DIHYDRO-5- METHYL-2-PHENYL-3H-PYRAZOL-3-THIONE AND 4,7-DIPHENYL-UO- PHENANTHROLINE, FOR IMPROVED SEPARATION OF TRIVALENT AMERICIUM AND EUROPIUM

ABSTRACT The extraction of Am(ITI) and Eu(III) from aqueous 0.1 M NaClO4 using a mixture of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (HBMPPT) and 4,7-diphenyl-l,10-phenanthroline (DPPHEN) was studied. Individually, neither the HBMPPT nor the DPPHEN in toluene showed any extraction capabilities for Am(III) or Eu(III) under the experimental conditions used in this study. Combination of the two ligands, however, yielded a synergistic system which showed a strong preference for Am(III) over Eu(III). Slope analysis indicated that the extracted species took the form M(BMPPT)3(DPPHEN) for both metal ions studied. The separation factor DAm/DEu was 190 at pH = 3.7, [HBMPPT] = 3.0 x 10-2, and [DPPHEN] = 2.7 x 10-3.

A preliminary evaluation of microporous hollow fiber membrane modules for the liquid-liquid extraction of actinides

Abstract Microporous hollow fiber (MHF) membrane modules provide an inexpensive, low-maintenance, and dispersion-free approach to continuous-flow liquid-liquid extraction processes. This work involves analyzing the potential for using these modules for process-scale metal separations such as radioactive waste stream cleanup and environmental remediation. In this work, MHF modules are used to remove neodymium (a surrogate for americium) from 2 M nitric acid using DHDECMP [dihexyl N , N -diethylcarbamoylmethylphosphonate] and CMPO [ n -octyl(phenyl)- N , N -diisobutylcarbamoylmethylphosphine oxide] as extractants in diisopropylbenzene. The modules are also used to concentrate the neodymium from the organic by back-extracting it into 0.01 M nitric acid. The performance of this technology is discussed in terms of the number of theoretical equilibrium extraction stages provided by each module, as well as how the modules extraction and back-extraction capabilities are affected by different aqueous and organic flow rates, and by the different extractants.

THE SYNTHESIS AND ACTINIDE AND LANTHANIDE COMPLEXATION OF“ SOFT” DONOR LIGANDS: COMPARISON BETWEEN 4-BENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-THIONE ( HBMPPT) AND 4-THIOBENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-ONE ( HTBMPP) WITH TRI-n-OCTYLPHOSPHINE OXIDE (TOPO) SYNERGIST FOR Am( III) AND Eu( III) EXTRACTION

ABSTRACT A comparison study between two “ soft” donor ligand isomers, 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione ( HBMPPT) and 4-thiobenzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one ( HTBMPP), both with tri-n-octylphosphine oxide ( TOPO) synergist in toluene, is reported for the extraction of Am( III) and Eu(UI). The more stable ligand, HBMPPT, gave no detectable extraction, but when HBMPPT and TOPO were combined, substantial extraction occurred with selectivity for Am( UI) over Eu( III) in three acid systems HC1, HCIO4, and HNO3. A maximum separation factor ( SF = DAm/ DEu) of 125 was obtained at pH 3.0 for the HBMPPT/ TOPO/ HCIO4 system. The other less stable ligand isomer, HTBMPP, did extract Am( m) to a small extent but combination with TOPO greatly enhanced the extraction. A maximum SF of 15 at pH 3.0 was observed for the HTBMPP/ TOPO/ HCIO4 system. Comparison of HBMPPT/ TOPO among the acids studied indicated different extraction mechanisms in the linear region in each system f...

Preconcentration of low levels of americium and plutonium from waste waters by synthetic water-soluble metal-binding polymers with ultrafiltration

A preconcentration approach to assist in the measurement of low levels of americium and plutonium in waste waters has been developed based on the concept of using water-soluble metal-binding polymers in combination with ultrafiltration. The method has been optimized to give over 90% recovery and accountability from actual waste water.

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

ABSTRACT 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) (KdAm = 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.

Amides as Phase Modifiers for N,N′-Tetraalkylmalonamide Extraction of Actinides and Lanthanides from Nitric Acid Solutions

Abstract The N,N′-tetraalkylmalonamides are a class of compounds under development for transuranic (TRU) separations under high nitric acid conditions. There are several issues that challenge the further development of these ligands. One is the development of improved synthetic procedures that lend themselves to commercial scale-up. Another major issue is the third-phase formation that occurs when the N,N′-tetraalkylmalonamides are contacted with medium-to-high nitric acid concentrations in hydrocarbon solvents. To address the synthesis issue we have developed a new synthetic approach for preparing these materials. Third-phase formation can be eliminated by addition of diluent modifiers such as tributylphosphate (TBP). TBP is inappropriate if a nonphosphate-containing process stream is required. Amides have been proposed as alternatives for TBP in a variety of applications because of their ease of synthesis and the variety of substituents that can be generated. We have been able to develop an amide phase-...

Evaluation of synthetic water-soluble metal-binding polymers with ultrafiltration for selective concentration of americium and plutonium

Water-soluble metal-binding polymers in combination with ultrafiltration are shown to be an effective method for selectively removing dilute actimide ions from acidic solutions of high ionic strength. The actinide-binding properties of commercially available water-soluble polymers and several polymers which have been reported in the literature were evaluated. The functional groups incorporated in the polymers were pyrrolidone, amine, oxime, and carboxylic, phosphonic, or sulfonic acid. The polymer containing phosphonic acid groups gave the best results with high distribution coefficients and concentration factors for241Am(III) and238Pu(III)/(IV) at pH 4 to 6 and ionic strengths of 0.1 to 4.

Preparation and crystal and molecular structures of uranyl complexes of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione and the pyrazol-3-one analogue

Abstract Uranyl complexes of the ligands 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (Hbmppt), the 3-one analogue (Hbmpp), and the corresponding anions were prepared and characterized by elemental analysis and spectroscopic methods. The complexes UO2(NO3)2(Hbmppt)· acetone and UO2(NO3)2(Hbmpp)·acetone can be isolated from the reaction of UO2(NO3)2·6H2O and Hbmppt for Hbmpp in acetone. In ethanol, UO2(NO3)2·6H2O reacts with K(bmppt) or Hbmpp to give UO2(bmppt)2·2EtOH or UO2(bmpp)2· 2EtOH, respectively. The ethanol adducts will react with dimethylsulfoxide to yield the dmso complexes UO2(bmppt)2(dmso)·acetone and UO2(bmpp)2(dmso). UO2(NO3)2(Hbmmppt)·acetone crystallizes in the triclinic space group P l with a = 9.663(5), b = 11.522(4), c = 11.823(3) A, α = 78.18(3), β = 72.56(3), γ = 76.54(4)°, Z = 2, V = 1208.3 A3, pcalc = 2.05 g cm−3, RF = 0.031, RwF = 0.038. The crystal structure shows two bidentate nitrate anions and a neutral bidentate Hbmppt ligand (US = 2.871(3) A) in the equational plane of the UO22+ ion. The Hbmppt ligand is bound as the NH tautomer with a hydrogen bond between the NH group and the oxygen atom of the acetone of crystallization (N⋯O = 2.71 A). UO2(bmppt)2(dmso)· acetone crystallizes in the monoclinic space group P21/n with a = 16.010(2), b = 11.050(2), c = 23.084(4), β = 98.77(2)°, Z = 4, V = 4035.7, pcalc = 1.63 g cm−3, RF = 0.052, RwF = 0.090. The crystal structure shows discrete molecules of UO2(bmppt)2(dmso) with a pentagonal bipyramidal geometry. The UO22+ group is coordinated with two bidentate bmppt anions and the oxygen of a dmso molecule in the equatorial plane. The bmppt anions are bound quite unsymmetrically. The dihedral angle between the plane of one bmppt anion (US = 2.836(6), UO = 2.36(1) A) and the uranyl equatorial plane is 38.5° while for the other bmppt anion (US = 2.902(6), UO = 2.29(1) A) the dihedral angle is only 11°.

PREPARATION OF WATER-SOLUBLE POLYMERS MODIFIED WITH SULFUR DONORS FOR RECOVERY OF HEAVY METALS

Polyethylenimine (PEI) was modified with ligands containing sulfur donors to give soluble polymers for binding toxic metal ions. Reaction of purified PEI with mercaptosuccinic anhydride, ethylene sulfide, or methylthiocyanate gave PEI-MSA (25% functionalization), PEI-ET (100% functionalization), and PEI-TU (25% functionalization), respectively. Purification of the polymers was accomplished by diafiltration. The capacities for toxic metal ions (Hg, Cd, and Pb) and transition metal ions (Cu and Ni) were measured for each of the polymers. PEI-ET and PEI-TU showed high affinity for the softer metal ions, Hg and Cd, with loading capacities substantially higher than those for the base polymer PEI. Both polymers had high capacities for Cu. Release of the metal ions from the polymers was accomplished by lowering pH; however, small amounts of metal remained bound to the polymers at pH 1. Competition studies showed that PEI-TU and PEI-ET bound Hg and Cu more strongly than Cd and Pb.

SELECTIVE EXTRACTION OF TRIVALENT ACTINIDES FROM LANTHANIDES WITH DITHIOPHOSPHINIC ACIDS AND TRIBUTYLPHOSPHATE

A variety of chemical systems have been developed to separate trivalent actinides from lanthanides based on the slightly stronger complexation of the trivalent actinides with ligands that contain soft donor atoms. The greater stability of the actinide complexes in these systems has often been attributed to a slightly greater covalent bonding component for the actinide ions relative to the lanthanide ions. We have investigated several synergistic extraction systems that use ligands with a combination of oxygen and sulfur donor atoms to achieve a good group separation of the trivalent actinides and lanthanides. For example, the combination of dicyclohexyldithiophosphinic acid and tributylphosphate has shown separation factors of up to 800 for americium over europium in a single extraction stage. Such systems could find application in advanced partitioning schemes for spent nuclear fuel and nuclear waste.