Dale D. Ensor

Aqueous complexation of trivalent lanthanide and actinide cations by N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine

Abstract The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO4. At 25°C, the stability constant of Am(TPEN)3+ is two orders of magnitude larger than that of Sm(TPEN)3+, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.

Synthesis of a new bisphosphonic acid ligand (SEDP) and preparation of a 188Re-(Sn)SEDP bone seeking radiotracer

The new bisphosphonate ligand SEDP (2-sulfonato-1,1-ethylidene bisphosphonic acid) has been synthesized and characterized, including the determination of the protonation constants, and used to form (188)Re-(Sn)SEDP from Na(188)ReO4. The title compound (188)Re-(Sn)SEDP shows slightly greater bone uptake and less kidney uptake than (188)Re-(Sn)HEDP in rat biodistribution studies.

Separation and preconcentration of cesium from acidic media by extraction chromatography

Abstract A novel extraction chromatographic resin for the separation and preconcentration of cesium from acidic nitrate media comprising an inert polymeric substrate impregnated with 1,3‐calix[4]bis‐o‐benzo‐crown‐6 (“BC6B”) in a chlorinated diluent is described. Cesium is shown to be both strongly and selectively retained by the resin at low (<1 M) acid concentrations and readily eluted from it using 6 M HNO3. Only potassium ion (at concentrations exceeding ca. 0.01 M) exerts a significant adverse impact on cesium retention. Unexpectedly, cesium uptake by the resin does not exhibit the acid dependency anticipated from liquid‐liquid extraction data. This is also the case for a resin employing a related macrocyclic extractant, calix[4]arene‐bis‐(t‐octylbenzocrown‐6) (“BobCalix”), prepared and partly characterized in an effort to overcome certain limitations of the BC6B‐based material. Despite this, the resin is shown to be well suited to the isolation of radiocesium from acidic solution for subsequent determination or for the removal of cesium intereference in the quantitation of other radionuclides.

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.

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 extraction of trivalent actinides and lanthanides using macrocyclic compounds

The combination of lipophilic macrocyclic oxygen donors with the extractant thenoyltrifluoroacetone /HTTA/ has been shown to have a significant synergistic effect on the extractions of trivalent actinides and lanthanides. The results show that the nitrogen containing cryptand /222BB/ is a more effective synergist than the crown ether compound /15-C-5/ with only oxygen donors.

Extraction of Cesium by a Calix[4]arene‐Crown‐6 Ether Bearing a Pendant Amine Group

Abstract The goal of this work was to evaluate the role of the amino group of 5‐aminomethylcalix[4]arene‐[bis‐4‐(2‐ethylhexyl)benzo‐crown‐6] (AMBEHB) in the extraction of cesium from acidic and basic mixtures of sodium nitrate and other concentrated salts. The extraction of cesium from nitrate media was measured as a function of extractant concentration, nitrate concentration, cesium concentration, and pH over the range 1–13. The initial studies showed a moderate decrease in the extraction of cesium in acidic media, which indicated the binding of cesium by the calixarene‐crown was weakened by the protonation of the amine group. The results also indicated that a 1∶1∶1 Cs‐ligand‐nitrate complex is formed in the organic phase. To further evaluate AMBEHB, the empirical data were mathematically modeled to determine the formation constants of the complexes formed in the organic phase. The resulting formation constants showed that the attachment of the amine group to the calixarene‐crown molecule reduced the binding stability for the cesium ion upon contact with an acidic solution. This supports the hypothesis of charge repulsion as the basis for more efficient stripping of cesium via pH‐switching.

Distribution Studies of Actinides Using a Tetradentate Extractant, 4,4′-Nonanedioyl-Bis(2,4-Dihydro-5-Methyl-2-Phenyl-3H-Pyrazol-3-One)

Abstract The extraction of Th(IV), UO2(II), Am(III), and Eu(III) from aqueous acid by a tetradentate extractant, 4,4′-nonanedioyl-bis(2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one), H2NDBP, has been studied and compared with two bidentate model compounds, 4-hexanoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one, HHMPP, and 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one, HBMPP. The distribution coefficients of UO2(II), Am(III), and Eu(III) were somewhat larger using H2NDBP relative to the model compounds under the conditions studied. However, the Th(IV) extraction using H2NDBP was greatly enhanced when compared to HBMPP or HHMPP. The distribution coefficient for Th(IV) from 0.5 M HNO3 was 11.6 using 3.0 × 10−3 M H2NDBP compared with values of D < 0.01 using 3.0 × 10−3 M HBMPP or HHMPP.

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.

Separation of Americium from Europium using Camphor-BisTriazinyl Pyridine: A Fundamental Study

ABSTRACT Among the different components present in spent nuclear fuel, long-lived trivalent actinides are particularly difficult to separate from the shorter-lived lanthanide fission products due to their similar chemical properties. Selective extraction of americium from acidic solution (up to 2M HNO3) containing tenth molar quantities of lanthanides has been achieved using neutral pyridine-based ligands dissolved in polar diluents. Nitrogen-based Bis Triazinyl Pyridine (BTP) ligands are desirable for both their excellent An/Ln selectivity and incinerability. Results pertaining to ligand solubility, kinetics, hydrolytic stability, and extraction performance in various nitric acid environments are presented.