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The extraction of americium(III), curium(III), and the lanthanides(III) from nitric acid by 6,6′‐ bis (5,5,8,8‐tetramethyl‐5,6,7,8‐tetrahydro‐benzo[1,2,4]triazin‐3‐yl)‐[2,2′]bipyridine (CyMe 4 ‐BTBP) has been studied. Since the extraction kinetics were slow, N,N′‐dimethyl‐N,N′‐dioctyl‐2‐(2‐hexyloxy‐ethyl)malonamide (DMDOHEMA) was added as a phase transfer reagent. With a mixture of 0.01 M CyMe 4 ‐BTBP+0.25 M DMDOHEMA in n ‐octanol, extraction equilibrium was reached within 5 min of mixing. At a nitric acid concentration of 1 M, an americium(III) distribution ratio of approx. 10 was achieved. Americium(III)/lanthanide(III) separation factors between 50 (dysprosium) and 1500 (lanthanum) were obtained. Whereas americium(III) and curium(III) were extracted as disolvates, the stoichiometries of the lanthanide(III) complexes were not identified unambiguously, owing to the presence of DMDOHEMA. In the absence of DMDOHEMA, both americium(III) and europium(III) were extracted as disolvates. Back‐extraction with 0.1 M nitric acid was thermodynamically possible but rather slow. Using a buffered glycolate solution of pH=4, an americium(III) distribution ratio of 0.01 was obtained within 5 min of mixing. There was no evidence of degradation of the extractant, for example, the extraction performance of CyMe 4 ‐BTBP during hydrolylsis with 1 M nitric acid did not change over a two month contact. [ABSTRACT FROM AUTHOR]

Multiple parallel synthesis and evaluation have been combined in order to identify new nitrogen heterocycles for the partitioning of minor actinides(III) such as americium(III) from lanthanides such as europium(III). An array of triazine-containing molecules was made using multiple parallel syntheses from diketones and amide hydrazides. An excess of each of the resulting purified reagents was dissolved in 1,1,2,2-tetrachloroethane containing 2-bromodecanoic acid, and equilibrated with an aqueous solution containing the radiotracers 152Eu and 241Am in nitric acid ([Eu] + [Am] < 400 nanomol dm−3). Gamma counting of the organic and aqueous phases led to the identification of several new reagents for the selective extraction of americium(III). In particular, 6-(2-pyridyl)-2-(5,6-dialkyl-1,2,4-triazaphenyl)pyridines were found to be effective reagents for the separation of americium(III) from europium(III), (SFAm/Eu was ca. 30 in [HNO3] = 0.013 mol/L). [ABSTRACT FROM AUTHOR]

Studies trivalent lanthanide interactions with a terdentate bis(dialkyltriazinyl)pyridine ligand using electrospray ionization mass spectrometry. Intensity distribution of ions; Formation of 1:3 complexes with the whole lanthanide series; Conditional stability constants of the 1:3 lanthanide (III) complexes.

Abstract: Due to their amphiphilic properties, malonamide molecules in alkane are organized in reverse micelle type aggregates, composed of a polar core formed by the malonamide polar heads and the extracted solutes, and surrounded by a hydrophobic shell made up of the extractant alkyl chains. The aggregates interact with one another through an attractive potential, leading to the formation of a third phase. This occurs with the splitting of the organic phase into a light phase composed mostly of diluent, and a heavy third phase containing highly concentrated extractant and solutes. In this article, we show that the aggregation (monomer concentration, domain of stability, and attractive potential between micelles) greatly depends on the nature of the extracted solute, whereas the size of aggregate (aggregation number) is only slightly influenced by this. We describe the extraction of water, nitric acid, neodymium nitrate and uranyl nitrate. Strongly polarizable species induce consistently large attraction potentials and a small stability domain for the dispersion of nanodroplets in the solvent. Highly polarizable ions such as lanthanides or uranyl induce more long-range attractive interactions than do protons. [ABSTRACT FROM AUTHOR]

To better understand the bonding in complexes of f-elements by polydentate N-donor ligands, the complexation of americium(lll) and lanthanide(lll) cations by 2-amino-4,6-di-(pyridin-2-yl)-1 ,3,5-triazine (ADPTZ) was studied using a thermodynamic approach. The stability constants of the 1:1 complexes in a methanol/water mixture (75/25 vol %) were determined by UV-visible spectrophotometry for every lanthanide(lll) ion (except promethium), and yttrium(lll) and americium(lll) cations. The thermodynamic parameters (δH°, δS°) of complexation were determined from the temperature dependence of the stability constants and by microcalorimetry. The trends of the variations of δG°, δSδ and δS° across the lanthanide series are compared with published results for other tridentate ligands and confirm strongly ionic bonding in the lanthanide—ADPTZ complexes. Comparison of the thermodynamic properties between the Am- and Ln—ADPTZ complexes highlights an increase in stability of the complexes by a factor of 20 in favor of the americium cation. This difference arises from a more exothermic reaction enthalpy in the case of Am, which is correlated with a greater degree of covalency in the americium-nitrogen bonds. Quantum chemistry calculations performed on a series of trivalent actinide and lanthanide—ADPTZ complexes support the experimental results, showing a slightly greater covalence in the actinide—ligand bonds that originates from a charge transfer from the ligand a orbitals to the 5f and 6d orbitals of the actinide ion. [ABSTRACT FROM AUTHOR]

The new extracting agent 2,6-bis(-1,2,4-triazin-3-yl)-pyridine (L1) has been synthesised and has been shown to form unusual 12-coordinate complexes of stoichiometry [LnL12(NO3)3] with Nd and Pr which have been characterised by X-ray diffraction. [Copyright &y& Elsevier]

Examines the iodide complexes of trivalent uranium and lanthanides with 2,2'-Bipyridine in anhydrous pyridine solutions by nuclear magnetic resonance spectroscopy, conductometry and X-ray crystallography. Bond lengths and angles; Stability constants; Enthalpy and entropy values for complex formation; Conductometric titration; X-ray crystal structure with thermal ellipsoids at 30% probability.