Richard E. Barrans

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.

FUNDAMENTAL INVESTIGATIONS OF SEPARATIONS SCIENCE FOR RADIOACTIVE MATERIALS

ABSTRACT Fundamental investigations of solvent extraction and ion exchange separations of radioactive materials have been conducted within the National Laboratory system of the U. S. Department of Energy (and its predecessor agencies) for the past 50 years. Basic research conducted at Oak Ridge and Argonne National Laboratories has produced both high quality new science and important applications in nuclear technology. The present contribution is an attempt to summarize the most important scientific results arising from this research during the past 10 years, a time of great change in the nuclear separations field, and to suggest possible directions for the next stage of research and development in this field.

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.

Synthesis of Symmetrical Methylenebis(Alkyl Hydrogen Phosphonates) by Selective Cleavage of Methylenebis(Dialkyl Phosphonates) with Morpholine

Abstract The preparation of partial esters of methylenebisphosphonic acids has been of recent interest due to their potential therapeutic applications. This paper describes a convenient method to prepare symmetrical methylenebis(alkyl hydrogen phosphonates) by the selective cleavage of the corresponding methylenebis(dialkyl phosphonate) with refluxing morpholine. The effects of structural variations on the amine as well as the substrate have been investigated to understand the scope and limitations of this reaction. A superior approach to hindered bisphosphonic acid esters involves the cleavage of their dimethyl esters, 4, using morpholine. This method is also useful to access a number of C-alkyl dialkyl methylenebisphosphonic acids such as 6. This study clearly shows that cleavage with morpholine is convenient, inexpensive, and allows for the preparation of a variety of P,P′-disubstituted partial esters in good yields and high purity.

Supercritical Carbon Dioxide-Soluble Ligands for Extracting Actinide Metal Ions from Porous Solids

Numerous types of actinide-bearing waste materials are found throughout the DOE complex. Most of these wastes consist of large volumes of non-hazardous materials contaminated with relatively small quantities of actinide elements. Separation of these wastes into their inert and radioactive components would dramatically reduce the costs of stabilization and disposal. For example, the DOE is responsible for decontaminating concrete within 7000 surplus contaminated buildings. The best technology now available for removing surface contamination from concrete involves removing the surface layer by grit blasting, which produces a large volume of blasting residue containing a small amount of radioactive material. Disposal of this residue is expensive because of its large volume and fine particulate nature. Considerable cost savings would result from separation of the radioactive constituents and stabilization of the concrete dust. Similarly, gas diffusion plants for uranium enrichment contain valuable high-purity nickel in the form of diffusion barriers. Decontamination is complicated by the extremely fine pores in these barriers, which are not readily accessible by most cleaning techniques. A cost-effect method for the removal of radioactive contaminants would release this valuable material for salvage.