Next-Generation 3,3'-AlkoxyBTPs as Complexants for Minor Actinide Separation from Lanthanides: A Comprehensive Separations, Spectroscopic, and DFT Study.

Progress toward the closure of the nuclear fuel cycle can be achieved if satisfactory separation strategies for the chemoselective speciation of the trivalent actinides from the lanthanides are realized in a nonproliferative manner. Since Kolarik's initial report on the utility of bis-1,2,4-triazinyl-2,6-pyridines (BTPs) in 1999, a perfect complexant-based, liquid-liquid separation system has yet to be realized. In this report, a comprehensive performance assessment for the separation of Am from Eu as a model system for spent nuclear fuel using hydrocarbon-actuated alkoxy-BTP complexants is described.

Prediction of the structures and heats of formation of MO, MO, and MO for M = V, Nb, Ta, Pa.

Structures for the mono-, di-, and tri-bridge isomers of MO as well as those for the MO and MO fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. The lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa.

Assignment of Vibrational Bands of Critical Surface Species Containing Nitrogen in the Selective Catalytic Reduction of NO by NH.

The selective catalytic reduction (SCR) of NO by NH on metal oxides plays a key role in minimizing NO emissions. Electronic structure calculations at the density functional theory level have been performed to predict the vibrational modes of NH/NH bound to validated cluster models of vanadium oxide bound to a TiO surface. Excellent agreement of the scaled calculated values with the observed bands attributed to surface-bound species is found.

Electronic Structure Investigation of NO and NO Binding on Vanadium Oxides.

NO and NO, which are generated in combustion processes, binding to vanadium oxide clusters including TiO-supported catalyst models in the selective catalytic reduction (SCR) of NO has been studied by density functional theory and coupled cluster methods. NO binding on vanadium oxides is predicted to depend on several factors, including the excitation energy of the oxide, ionization energies of both the unbound oxide and the deoxygenated reduced oxide, and the strength of the molecular V-O bonds. NO chemisorption occurs either through covalent bond formation in a HONO-like pattern or through abstraction of a metal oxide oxygen leading to the formation of NO.

Observation of Selectively Populated Monohalide Excited States from the Reactions of Group 3 Metal (Sc, Y, and La) Monomers and Dimers with Halogen-Containing Molecules.

The chemiluminescent reactions of the group 3 metals Sc and Y with F, Cl, Br, ClF, ICl (Sc), IBr (Y), and SF and La with F, SF, Cl, and ClF have been studied at low pressures (6 × 10 to 4 × 10 Torr) using a beam-gas arrangement and extended to the 10 Torr multiple collision pressure range. Contrary to previous reports, the observed chemiluminescent spectra are primarily attributed to emission from the metal monohalides. Extensive pressure and temperature dependence studies and high-level correlated molecular orbital theory calculations of the bond dissociation energies support this conclusion and the attribution of the chemiluminescence.

Prediction of An(III)/Ln(III) Separation by 1,2,4-Triazinylpyridine Derivatives.

The effect of frustrated Lewis donors on metal selectivity between actinides and lanthanides was studied using a series of novel organic ligands. Structures and thermodynamic energies were predicted in the gas phase, in water, and in butanol using 9-coordinate, explicitly solvated (HO) Eu, Gd, Am, and Cm in the +III oxidation state as reactants in the formation of complexes with 2-(6-[1,2,4]-triazin-3-yl-pyridin-2-yl)-1-indole (Core 1), 3-[6-(2-pyrazol-3-yl)pyridin-2-yl]-1,2,4-triazine (Core 2), and several derivatives. These complexations were studied using density functional theory (DFT) incorporating scalar relativistic effects on the actinides and lanthanides using a small core pseudopotential and corresponding basis set.