Production of Gas-Phase Uranium Fluoroanions Via Solubilization of Uranium Oxides in the [1-Ethyl-3-Methylimidazolium]⁺[F(HF)_2.3]⁻ Ionic Liquid

Abstract

A new methodology for gas-phase uranium ion formation is described in which UO is dissolved in neat N-ethyl,N'-methylimidazolium fluorohydrogenate ionic liquid [EMIm][F(HF)], yielding a blue-green solution. The solution was diluted with acetonitrile and then analyzed by electrospray ionization mass spectrometry. UF (a U(V) species) was observed at m/z = 352, and other than cluster ions derived from the ionic liquid, nothing else was observed. When the sample was analyzed using infusion desorption chemical ionization, UF was the base peak, and it was accompanied by a less intense UF that most likely was formed by elimination of a fluorine radical from UF. Formation of UF required dissolution of UO followed by or concurrent with oxidation of uranium from the + 4 to the + 5 state and finally formation of the fluorouranate. Dissolution of UO produced a bright yellow solution indicative of a U(VI) species; however, electrospray ionization did not produce abundant U-containing ions. The abundant UF provides a vehicle for accurate measurement of uranium isotopic abundances free from interference from minor isotopes of other elements and a convenient ion synthesis route that is needed gas-phase structure and reactivity studies like infrared multiphoton dissociation and ion-molecule dissociation and condensation reactions. The reactive fluorohydrogenate ionic liquid may also enable conversion of uranium in oxidic matrices into uranium fluorides that slowly oxidize to uranyl fluoride under ambient conditions, liberating the metal for facile measurement of isotope ratios without extensive chemical separations. Graphical abstract ᅟ.

Synthesis and Dissolution of Metal Oxides in Ionic Liquids and Deep Eutectic Solvents

“…The dissolved species for UO 2 is assumed to be UF 6 − at first, which is further oxidised to uranium(VI) by oxygen from air. Upon this process, the diffusion of oxygen into the solution takes place, yielding uranyl fluoride species [116]. This IL should rather be perceived as a fluorinating agent then as a solvent for metal oxides, as the dissolution process involves the consumption of the IL anion.…”

Speciation of Copper(II)‐Betaine Complexes as Starting Point for Electrochemical Copper Deposition from Ionic Liquids

“…A currently investigated approach to overcome these problems is the application of reusable non‐aqueous solvents such as ionic liquids (ILs) [7–14] or deep‐eutectic solvents (DESs) [15–23] . Referring to hydrometallurgy, we suggest the term ionometallurgical processing for metal extraction by means of ILs and DESs.…”

New Greener and Sustainable Methodology for Direct Sequestering and Analysis of Uranium Using a Maline Supramolecular Scaffold and Mechanistic Understanding through Speciation and Interaction Studies

“…The presence of protons in Maline, acting as an oxygen acceptor, supports dissolution through the water-forming reaction with oxygen atoms of metal oxides. Therefore, in the present case, the choice of Maline as a solvating media for direct and quantitative sequestration of U matrices without any additives is beneficial over the additives and other solvating media used in the previous studies, − ,, owing to the bidentate coordination mode of Maline (obtained by EXAFS; described later) which offers strong interaction for U and hence more solvating potential than the urea and PTSA.…”

“…Previous studies ,− reported the use of additives, viz., water, aqueous hazardous acids, and Fe and Al salts during ionometallurgical processing of U matrices. Moreover, the literature survey implies the lack of direct sequestration of U from its solid matrices and the green analysis methodology for U.…”