Daniel R. McAlister

Novel Extraction of Chromatographic Resins Based on Tetraalkyldiglycolamides: Characterization and Potential Applications

Abstract Two new extraction chromatographic resins containing the diglycolamide class of molecules have been prepared and characterized, and potential applications identified. The new resins consist of 40 weight percent N,N,N′N′ tetraoctyldiglycolamide (TODGA) and N,N,N′N′ tetrakis‐2‐ethylhexyldiglycolamide (TEHDGA) sorbed onto 50–100 µm particle size Amberchrom® CG‐71. The new resins have capacities for Eu of approximately 0.086 mmol/mL of bed and are quite stable to extractant leaching. The resins were characterized by measuring the batch uptake of actinides, lanthanides, and yttrium, alkaline earths and 13 selected transition and post‐transition elements from HNO3 and HCl. Based on the uptake data, a number of very efficient separations were achieved using 0.5–2 mL bed volume columns and room temperature operation.

Extraction Chromatography Versus Solvent Extraction: How Similar are They?

Abstract Over the last decade, extraction chromatography (EXC) has emerged as a versatile and effective method for the separation and preconcentration of a number of metal ions. Frequently, EXC is described as a technique that combines the selectivity of solvent extraction (SX) with the ease of operation of chromatographic methods. Despite this, the extent to which EXC actually provides the selectivity of SX and to which solvent extraction data can be used for the quantitative prediction of the retention of metal ions on an EXC column has remained unclear. To address these questions, the extraction chromatographic and solvent extraction behavior of lanthanides using three different acidic organophosphorus extractants bis‐(2‐ethylhexyl) phosphoric acid (HDEHP), 2‐ethylhexyl 2‐ethylhexylphosphonic acid (HEH[EHP]), and bis‐(2,4,4 trimethylpentyl)phosphinic acid (H[DTMPeP])) have been compared. Specifically, the rate and extent of uptake of selected lanthanides by the three extractants have been examined. In addition, the relationship between the volume distribution ratios obtained in the chromatographic and liquid–liquid extraction modes have been compared and their utility in predicting the chromatographic parameter, k′, the number of free column volumes to peak maximum determined.

FT-IR STUDY OF THIRD PHASE FORMATION IN THE U(VI) OR Th(IV)/HNO3, TBP/ALKANE SYSTEMS

ABSTRACT The infrared reflectance spectra of the third phases formed in the systems UO2(NO3)2/HNO3/20%TBP in n-dodecane and Th(NO3)4/HNO3/20%TBP in n-octane gave evidence for the presence in solution of a significant amount of weakly bonded molecular nitric acid. From the correlation between the ratio of the areas of the bands at 1672 cm−1 and 1648 cm−1, characteristic of weakly intermolecularly hydrogen-bonded nitric acid and nitric acid strongly bonded to TBP, respectively, the molecular HNO3 concentration was determined. The presence of these two bands in the spectra of the third phase samples provides evidence that only part of the HNO3 is directly and strongly bound to the TBP phosphoryl group. The ratio of the weakly intermolecularly hydrogen-bonded HNO3 to that bound directly to P=O group of TBP was much higher for the uranium than for the thorium third phases formed under comparable conditions. The estimated amounts of the weakly intermolecularly hydrogen-bonded HNO3 were about 47% and 30% of the total HNO3 present in the uranium and thorium systems, respectively. In the uranium third phase, the TBP hemisolvate of HNO3 (TBPċ2HNO3) was recognized as the predominant species with accompanying very small amount of monosolvate (TBPċHNO3). In the thorium system the hemisolvate of HNO3 was also present, but the monosolvate was found to be the major species. When the thorium concentration in the third phase was increased, a conversion of monosolvate into hemisolvate was observed. Analysis of the infrared spectra for both systems indicated that the nitrate anions form bidentate chelates with the studied metals. The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.†Corresponding author. E-mail: borkowski@anchim.chm.anl.gov

Automated two column generator systems for medical radionuclides

This work describes automated chromatographic methods for the separation of medically useful radionuclides from source material containing their parent radionuclides. The separation techniques employ two chromatographic columns to ensure high chemical and radiochemical purity of the product radionuclide. The separations were performed using an automated system, the automated radionuclide separator (ARS2), consisting of syringe pumps and multiport valves controlled through a computer interface. Generator systems for (68)Ga, (99m)Tc, (188)Re and (213)Bi will be described.

HYDROGEN BONDING IN AGGREGATES OF DIALKYL-SUBSTITUTED DIPHOSPHONIC ACIDS AND MONOFUNCTIONAL ANALOGUES

Hydrogen bonding of dialkyl-substituted diphosphonic acids in nonpolar (toluene and CCl{sub 4}) and alcohol (1-decanol) solutions is examined. The compounds are monomeric in 1-decanol and dimeric or higher in nonpolar organic diluents. Infrared spectroscopy and molecular mechanics calculations suggest that the dimers of P,P{prime}-di(2-ethylhexyl) methanediphosphonic acid (H{sub 2}DEH[MDP]) and its straight-chain isomer, P,P{prime}-dioctyl methanediphosphonic acid (H{sub 2}DO[MDP]), adopt rigid highly hydrogen-bonded structures such as C or D. The homologous P,P{prime}-di(2-ethylhexyl) ethane- and butanediphosphonic acids, H{sub 2}DEH[EDP] and H{sub 2}DEH[BuDP], respectively adopt structures that are also intermolecularly hydrogen-bonded but more flexible. The effect on the P+O stretching vibration of increasing 1-decanol concentration in the solvent differs for these compounds. In the case of H{sub 2}DEH[MDP] and H{sub 2}DO[MDP], the frequency remains constant until all CCl{sub 4} has been replaced by the alcohol, then the P=O stretching frequency shifts to a lower energy. In the case of H{sub 2}DEH[edp] and H{sub 2}DEH[BuDP], a gradual shift to higher energy occurs as the alcohol concentration increases. The magnitude of the difference in the P=O stretching frequencies between CCL{sub 4} and 1-decanol solution is greatest for organophosphonic acids, less for organodiphosphonic acids, and least for organophosphoric acids.

Aggregation of dialkyl-substituted diphosphonic acids and its effect on metal ion extraction.

Solvent extraction reagents containing the diphosphonic acid group exhibit an extraordinary affinity for tri-, tetra-, and hexavalent actinides. Their use has been considered for actinide separation and preconcentration procedures. Solvent extraction data obtained with P,P′-di(2-ethylhexyl) methane-, ethane-, and butanediphosphonic acids exhibit features that are difficult to explain without knowl edge of the aggregation state of the extractants. Information about the aggregation of the dialkyl-substituted diphosphonic acids in aromatic diluents has been obtained using the complementary techniques of vapor pressure osmometry, small-angle neutron scattering, infrared spectroscopy, and molecular mechanics. The results from these techniques provide an understanding of the aggregation behavior of these extractants that is fully compatible with the solvent extraction data. The most important results and their relevance to solvent extraction are reviewed in this paper. The work at ANL was performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. Department of Energy, under contract W-31-109-ENG-38.

Synergistic Enhancement of the Extraction of Trivalent Lanthanides and Actinides by Tetra‐(n‐Octyl)Diglycolamide from Chloride Media

Abstract This work describes a unique synergistic enhancement of the extraction of trivalent actinides and lanthanides by extraction chromatographic resins containing tetra‐n‐octyldiglycolamide (TODGA) from hydrochloric acid containing anionic metal chlorides. The presence of mg/L quantities of trivalent Fe, Ga, In, Tl, or Bi in HCl leads to several orders of magnitude enhancement of the extraction of trivalent actinides and lanthanides. The synergistic effect persists, even when the amount of metal chloride exceeds the capacity of the resin. The application of this synergistic enhancement for the separation of actinium from stainless steel and the preconcentration of americium and plutonium from large soil samples will be described.

Characterization of Extraction of Chromatographic Materials Containing Bis(2‐ethyl‐1‐hexyl)Phosphoric Acid, 2‐Ethyl‐1‐Hexyl (2‐Ethyl‐1‐Hexyl) Phosphonic Acid, and Bis(2,4,4‐Trimethyl‐1‐Pentyl)Phosphinic Acid

Abstract This work describes the uptake of a wide range of metal ions, including alkaline earths, transition metals, post‐transition metals, lanthanides and actinides, from acidic nitrate and chloride media on extraction chromatographic resins prepared from three different acidic organophosphorus compounds: bis(2‐ethyl‐1‐hexyl) phosphoric acid (HDEHP), 2‐ethyl‐1‐hexyl(2‐ethyl‐1‐hexyl)phosphonic acid, (HEH[EHP]) and bis(2,4,4‐trimethyl‐1‐pentyl)phosphinic acid (H[DTMPP]). The data is plotted in a format allowing for the easy comparison of the uptake of all metal ions under a given condition. Additionally, examples of several novel separations using the three extraction chromatographic materials are discussed.

SOLVENT EXTRACTION BY DIALKYL-SUBSTITUTED DIPHOSPHONIC ACIDS IN A DEPOLYMERIZING DILUENT. II. Fe(III) AND ACTINIDE IONS

In this work, the extraction of Am(III), U(VI), Th(IV) and Fe(III) by P,P′-di(2-ethylhexyl) methylene- (H2DEH[MDP]), ethylene- (H2DEH[EDP]), and butylene- (H2DEH[BuDP]) diphosphonic acids dissolved in the monomerizing diluent 1-decanol has been investigated. A comparison of the acid dependencies with those observed in o-xylene has revealed a number of novel features which have been ascribed to extraction of metal nitrates through a solvation mechanism made possible by facile transfer of nitrate ions into the 1-decanol phase. The use of 1-decanol as the diluent gives rise to strong suppression of metal extraction, which increases along the series Fe(III)<U(VI)<Am(III)<Th(IV) and H2DEH[MDP]<H2DEH[EDP]≤H2DEH[BuDP]. The extractant dependencies of U(VI) and Th(IV) have slopes equal to 2 with all extractants. Those for Am(III) and Fe(III) exhibit variable slopes with limiting values of 1 at the lowest and 3 at the highest extractant concentrations. From the combined information provided by the acid and extractant dependencies, stoichiometries and probable structures for complexes formed in the organic phase have been proposed. The data obtained in this work suggest a simple route for actinide stripping from diphosphonic acid extractants loaded in nonpolar diluents.

METAL ION EXTRACTION BY SILYL-SUBSTITUTED DIPHOSPHONIC ACIDS. I. P,P′-DI-[3-(TRIMETHYLSILYL)-1-PROPYLENE] METHYLENE- AND ETHYLENEDIPHOSPHONIC ACIDS

In conjunction with efforts to develop novel actinide extractants that exhibit solubility in supercritical carbon dioxide (SCCO2), the effect of adding silicon-based functionalities to diphosphonic acids on their aggregation and solvent extraction chemistry was investigated. Two silyl-derivatized diphosphonic acids, P,P′-di[3-(trimethylsilyl)-1-propylene] methylenediphosphonic acid (H2DTMSP[MDP]) and P,P′-di[3-(trimethylsilyl)-1-propylene] ethylenediphosphonic acid (H2DTMSP[EDP]), were prepared and their aggregation and metal ion extraction properties compared to those of the previously studied P,P′-di(2-ethylhexyl) alkylenediphosphonic acids. Vapor pressure osmometry of H2DTMSP[MDP] and H2DTMSP[EDP] in toluene (25°C) indicates that, as is the case for the 2-ethylhexyl-substituted alkylenediphosphonic acid analogs, the compounds are dimeric and (primarily) hexameric, respectively, in the concentration range investigated. Distribution ratio measurements for the alkaline earth cations Ca2+, Sr2+, Ba2+, and Ra2+ as well as the representative tri-, tetra-, and hexavalent actinides Am3+, Th4+, and UO2+ 2 between solutions of H2DTMSP[MDP] and H2DTMSP[EDP] in o-xylene and nitric acid indicate that the behavior of these silyl-derivatized compounds closely mimics that of the analogous P,P′-di(2-ethylhexyl) alkylenediphosphonic acids, indicating that incorporation of a silyl functionality has no adverse impact on the metal ion extraction properties of diphosphonic acids.