M. Yu. Alyapyshev

Extraction of uranium(VI) with diamides of dipicolinic acid from nitric acid solutions

Abstract Three structural isomers of diamides of dipicolinic acid (N,N′-diethyl-N,N′-ditolyl-dipicolinamide, EtTDPA) with varying position of the methyl group on the tolyl ring have been synthesized and investigated on extractability toward U(VI). The polar diluent FS-13 was used, and distribution ratios of U(VI) were studied as a function of nitric acid, ligand, and lithium nitrate concentrations. Extractability of uranium was shown to increase with increased concentration of nitrate and ligands. Infrared spectra of organic extraction phases indicate that nitric acid is coextracted as part of the neutral metal-ligand complex with U(VI) and EtTDPA through hydrogen bonding with the carbonyl group in the amide moiety.

Metal extraction by N,N dialkyl -N,N'-diaryl -dipicolinamides from nitric acid solutions

A study of americium, uranium and europium extraction by various dialkyl-diarylamides of 2,6-pyridine-dicarboxylic (dipicolinic) acid has shown that maximum extractability is achieved by using polar fluorine-substituted diluents. Generally, the diamide extractability is found to increase with the alkyl radical length. We have demonstrated the possibility to separate Am and Eu in solutions with a nitric acid concentration of 0.5–2 mol/l. The extractability of these diamides with respect to the three metals rises with the acid concentration increase to 6 mol/l.

Radionuclide Extraction by 2,6‐Pyridinedicarboxylamide Derivatives and Chlorinated Cobalt Dicarbollide

Abstract The extraction properties of diamide derivatives of dipicolinamide (2,6‐pyridinedicarboxylamide or DPA, (R′R″NCO)2C5NH3) in mixtures containing chlorinated cobalt dicarbollide in the acid form (HCCD), with and without a substituted polyethylene glycol (PEG), have been investigated. Distribution ratios of Cs, Sr, U, Eu and Am have been measured for various concentrations of diamide, PEG, aqueous phase nitric acid, with various HCCD:diamide ratios, and using different organic diluents. In the absence of HCCD, the diamides show little affinity for the extraction of Am or Eu from nitric acid solutions (distributions typically <1). Addition of HCCD with the diamide extractants indicates a pronounced synergistic effect with regard to actinide and lanthanide extraction; the observed Am and Eu distribution ratios typically increase by several orders of magnitude. Cesium is also appreciably extracted by the HCCD in the presence of the various diamides. Addition of PEG (to simultaneously extract Sr) with HCCD and diamide has minimal impacts on the Eu and Am distribution ratios. The initial data indicate that alkyl substituted DPA derivatives weakly affect the extraction properties with regard to actinides and lanthanides, while aryl substituents decrease extraction ability of the mixture. The results of this preliminary work indicate that numerous HCCD‐PEG‐DPA systems are promising and effective for the simultaneous extraction Cs, Sr, Am, and Eu from acidic solutions.

Dependence of Extraction Properties of 2,6-Dicarboxypyridine Diamides on Extractant Structure

Abstract New diamides of dipicolinic acid have been prepared and their affinity for lanthanides, americium, and uranium has been explored using the liquid-liquid extraction method. These extractants feature mixed alkyl/aryl substituents. The highest extraction is seen for phenyl/ethyl derivatives. The structure-reactivity relationship for extraction and solubility is discussed.

Extraction of Lanthanides with Diamides of Dipicolinic Acid from Nitric Acid Solutions. I

Abstract Three ortho-, meta-, and para-derivates of ethyl(tolyl)diamides of dipicolinic acid were synthesized and tested on their extraction performance from nitric acids solutions. Extraction of americium and lanthanides (Ln) by these compounds as a function of nitric acid concentration was studied. Distribution ratios of studied metals were determined using ICP-OES method and radiotracer 241Am. Am/Ln separation differs among studied diamides, and the best separation was found for N,N′-diethyl-N,N′-di(ortho)tolyl-diamide.

New Diamides of 2,2′-dipyridyl-6,6′-dicarboxylic Acid for Actinide-Lanthanide Separation

The extraction of americium and lanthanides by diamides of 2,2′-dipyridyl-6,6′-dicarboxilic acid solutions in polar diluents was investigated. The dependence of extraction properties of the diamides on their structure was studied and the distribution ratios of americium and lanthanides from nitric acid solutions were determined. The highest extraction was found for the compounds with the ethyl-group and the alkyl-substituted aryl-group on the amidic nitrogen. The Am/Ln separation factors higher than 10 were achieved for extraction from high acidity media.

Novel diamides of 2,2′-dipyridyl-6,6′-dicarboxylic acid: synthesis, coordination properties, and possibilities of use in electrochemical sensors and liquid extraction

The procedure was proposed for the synthesis of various dipyridyldiamides. Their various properties in the series of rare-earth elements were studied. The possibility to use the synthe-sized compounds in polymer membranes of electrochemical sensors for the development of novel types of sensors was shown. A comparison of the influence of the ligand structure on the extraction and sensor characteristics was performed.

Extraction of Am and Eu with N,N′-substituted pyridine-2,6-dicarboxamides in fluorinated diluents

Extraction of Am and Eu with N,N′-substituted pyridine-2,6-dicarboxamides in fluorinated diluents was studied. N,N′-Diethyl-N,N′-di(p-tolyl)pyridine-2,6-dicarboxamide (EtTPDA) is readily soluble in fluorinated diluents, and its solutions allow the extraction of TPE and REE from nitric acid solutions. The extraction ability of EtTPDA in fluorinated polar diluents is higher than in CHCl3. In the extraction with EtTPDA, the Am/Eu selectivity is independent of the extractant concentration and decreases with an increase in the acidity of the medium. Americium is extracted with EtTPDA better than Eu, which allows selective recovery of Am at moderate HNO3 concentrations.

Amides of heterocyclic carboxylic acids as novel extractants for high-level waste treatment

Extraction properties of various heterocyclic carboxylic acid amides are considered. The extraction properties of heterocyclic dicarboxylic acid diamides are determined by two major factors: diamide structure and kind of diluent. Among heterocyclic (di)carboxylic acid amides and diamides, the most promising extractants for separating actinides and lanthanides are tri- and tetradentate extractants: diamides of dipicolinic, bipyridinedicarboxylic, and phenanthrolinedicarboxylic acids, which can be used for recovering metals from acid solutions.

A novel solvent system containing a dipicolinamide in room temperature ionic liquids for actinide ion extraction

Solvent extraction of Am(III), Pu(IV) and Eu(III) was done from nitric acid medium using a solvent system containing a substituted dipicolinamide extractant dissolved in room temperature ionic liquid. The solvent system was found to be more efficient as compared to the previously reported solvents in molecular diluents.