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Ionic liquids (ILs) are a unique class of solvents with potential applications in advanced separation technologies relevant to the nuclear industry. ILs are salts with low melting points and a wide range of tunable physical properties, such as viscosity, hydrophobiciy, conductivity, and liquidus range. ILs have negligible vapor pressure, are often non-flammable, and can have high thermal stability and a wide electrochemical window, making them attractive for use in separations processes relevant to the nuclear industry. Metal salts generally have a low solubility in ILs; however, by incorporating new functional groups into the IL cation or anion that promote complexation with the metal, the solubility can be greatly increased. One such task-specific ionic liquid (TSIL) is 1-carboxy-N, N, N-trimethylglycine bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) [Nockemann et al., J. Phys. Chem. B 110, 20978–20992 (2006)]. Water, which is detrimental for electrochemical separations, is a common impurity in ILs and can coordinate with actinyl cations, particularly in ILs containing only weakly coordinating components. Understanding the behavior of actinides in TSIL/water mixtures on a molecular level is vital for designing improved separations processes. Classical molecular dynamics simulations of uranyl(VI) and plutonyl(VI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) with deprotonated Hbet (betaine) and water have been performed to understand the coordination and dynamics of the actinyl cations. We find that betaine is a much stronger ligand than water and prefers to coordinate the metal in a bidentate manner. Potential of mean force simulations yield a relative free energy for betaine coordination of approximately −120 to −90 kJ/mol in mixtures with water. As the amount of betaine coordinated to the actinide increases, the diffusion coefficient of the actinyl cation decreases. Moreover, the betaine ligand is able to bridge between two metal centers, resulting in dimeric complexes with actinide–actinide distances of ∼5 Å. Potential of mean force simulations show that these structures are stable, with relative free energies of up to −40 kJ/mol. The crystal structure for [(UO2)2(bet)6(H2O)2][Tf2N]4 shows that the betaine bridges between two uranium atoms to form dimeric complexes similar to those found in our simulations [Nockemann et al. Inorg. Chem. 49, 3351–33601 (2010)]. [ABSTRACT FROM AUTHOR]

Research has been conducted on uranium(VI). The reactions of this compound with acidic aqueous chloride solutions have produced polymeric uranium(VI) compounds, and single crystals have been formed under hydrothermal conditions.

Research has been conducted on the alkali metal crown ether uranyl halide sandwich-type compounds. The synthesis and the X-ray structure of these compounds have been carried out and described.

Researchers found that neptunium, which is a small but very significant element within nuclear waste, is more stable in the environment than previously thought, which will make designing appropriate disposal methods more problematic. Tables and figures accompany the article.

Researchers from the Los Alamos National Laboratory in New Mexico performed experiments from the Yucca Mountain Nuclear Waste Repository site, NV for the solubility of neptunium and plutonium.

The spectroscopic characterization and thermodynamic stability of the mixed-ligand complex, U[O.sub.2]([O.sub.2])[(C[O.sub.3]).sub.2.sup.4-], is described in both solution and solid state. The studies have shown that the stable solution species is U[O.sub.2]([O.sub.2])[(C[O.sub.3]).sub.2.sup.4-], which has a formation constant that is relative to the tris-carbonato complex.

Two americium(III) iodates, beta-Am(IO3)3 and alpha-Am(IO3)3 are prepared from the aqueous reactions of Am(superIII) with KlO4 at 180 degrees Celsius and are characterized by single-crystal X-ray diffraction, diffuse reflectance and Raman spectroscopy. The alpha-form, consistent with the known structure of anhydrous lanthanide iodates, is a 3D network of pyramidal iodate groups, while the beta-form has a 2D layered structure with nine-coordinate Am(super III) atoms, novel to the f-element iodate series.

The synthesis and structural characterization of mixed Pu(VI) hydroxo-iodate compound, (PuO2)2(IO3)(OH)3 is presented. The structure consists of two-dimensional layers forming in the ac plane and is the first single-crystal structure of plutonium(VI) connected through hydroxide anions.

Pu L3 W-ray near edge absorption spectra for Pu(0-VII) for more than 60 chalcogenides, chlorides, hydrates, hydroxides, nitrates, carbonates, oxy-hydroxides and other compounds both as solids and in solution are reported.

Research has been conducted on neptunyl(VI) iodates. The authors describe the preparation of these compounds in HCl via aqueous reactions of Np(V) with KIO (sub)4, and their characterization via single-crystal X-ray diffraction and Raman spectroscopy.

Research has been conducted on PuO (sub)2+x. The authors report that the number of oxo atoms increases when the samples are equilibrated with humid air, and indicate that Pu reactivity in this system differes from that of isolated complexes.

Research has been conducted on nickel(II)/uranium(IV) fluorides. The preparation of these fluorides in aqueous media under mild hydrothermal conditions is described.