Specialized extractant ligands – such as tri-butyl phosphate (TBP), N,N-di-(2-ethylhexyl)butyramide (DEHBA), and N,N-di-2-ethylhexylisobutryamide (DEHiBA) – have been developed for the recovery of uranium from used nuclear fuel by reprocessing solvent...

A comprehensive multiscale model determines the fundamental reaction mechanisms of the radical-induced degradation of acetohydroxamic acid in acidic aqueous solutions.

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Aqueous geochemistry could be extended considerably if nuclear-magnetic resonance (NMR) methods could be adapted to study solutions at elevated temperatures and pressures. We therefore designed an NMR probe that can be used to study aqueous solutions at gigapascal pressures. Fluoride solutions were chosen for study because 19 F couples to other nuclei in the solutions (31 P and 11 B) in ways that make peak assignments unequivocal. Correspondingly, NMR spectra of 19 F-and 11 B were collected on aqueous HBF 4-NH 4 PF 6 solutions to pressures up to 2.0 GPa. At pressure, peaks in the 19 F spectra were clear and assignable to the BF 4 À (aq), F À (aq) and BF 3 OH À (aq) ions, and these aqueous complexes varied in signal intensity with pressure and time, for each solution. Peaks in the 11 B spectra at pressure could be assigned to the BF 4 À (aq) and BF 3 OH À (aq) species. Additionally, there is a single peak that is assignable to H 3 BO 3 o (aq) and B(OH) 4 À (aq) in rapid-exchange equilibria. These peaks broaden and move with pressure in ways that suggest reversible interconversion of borate and fluoroborate species. The PF 6 À ion was found to provide a suitable 19 F shift and intensity standard for high-pressure spectra because it was chemically inert. The positions and intensities of the doublet peak also remains constant as a function of pressure and pH. Addition of electrolytes considerably distorts the phase diagram of water such that the stability region of the aqueous solution expands to well beyond the 0.8 GPa freezing pressure of pure water; some fluoroborate solutions remain liquid until almost 2.0 GPa.

The solution chemistry of aluminum has long interested scientists due to its relevance to materials chemistry and geochemistry. The dynamic behavior of large aluminum-oxo-hydroxo clusters, specifically [Al O (OH) (H O) ] (Al ), is the focus of this paper. Al NMR, H NMR, and H DOSY techniques were used to follow the isomerization of the ϵ-Al in the presence of glycine and Ca at 90 °C. Although the conversion of ϵ-Al to new clusters and/or Baker-Figgis-Keggin isomers has been studied previously, new H NMR and H DOSY analyses provided information about the role of glycine, the ligated intermediates, and the mechanism of isomerization. New H NMR data suggest that glycine plays a critical role in the isomerization. Surprisingly, glycine does not bind to Al clusters, which were previously proposed as an intermediate in the isomerization. Additionally, a highly symmetric tetrahedral signal (δ=72 ppm) appeared during the isomerization process, which evidence suggests corresponds to the long-sought α-Al isomer in solution.