Direct dissolution of UO in carboxyl-functionalized ionic liquids in the presence or absence of Fe-containing ionic liquids.

Dissolution of UO is a prerequisite for the reprocessing of spent nuclear fuel. This study showed that UO could be directly dissolved in a single carboxyl-functionalized ionic liquid (IL), [HOOCMmim][TfN] 1-carboxymethyl-3-methylimidazolium bistriflimide, or [HOOCEtmim][TfN] 1-carboxyethyl-3-methylimidazolium bistriflimide. The addition of an extra Fe-containing IL, [Emim][FeCl] (Emim, 1-ethyl-3-methylimidazolium) or [Bmim][FeCl] (Bmim, 1-butyl-3-methylimidazolium) could significantly improve the dissolution kinetics.

Ionic liquids with polychloride anions as effective oxidants for the dissolution of UO.

Herein, polychloride ([Cl] or/and [Cl]) ionic liquids (ILs) were prepared from their imidazolium chloride precursors by the addition of chlorine gas. The highest storage ability of Cl was found in the [Bmim]Cl IL among the six imidazolium chlorides [Rmim]Cl (Rmim = Emim, 1-ethyl-3-methylimidazolium; Bmim, 1-butyl-3-methylimidazolium; Pmim, 1-propyl-3-methylimidazolium; Pnmim, 1-pentyl-3-methylimidazolium; Hmim, 1-hexyl-3-methylimidazolium; and Omim, 1-octyl-3-methylimidazolium). When a mixed IL of [Bmim][TfN] (1-butyl-3-methylimidazolium bistriflimide) and [Bmim]Cl was used, the IL cation could maintain good stability during the chlorination process, and the imidazolium cation [Bmim] could retain almost the same structure after the chlorine gas was introduced into the mixed IL according to H NMR spectroscopy.

Fe-containing ionic liquids as effective and recoverable oxidants for dissolution of UO2 in the presence of imidazolium chlorides.

Imidazolium-based Fe-containing ionic liquids (ILs) can directly dissolve UO2 in the presence of their corresponding imidazolium chlorides without additional oxidants. The dissolution process follows pseudo first-order kinetics initially. Raman spectroscopic studies indicate that FeCl4(2-) is the predominant reduction product after UO2 dissolution, and attenuated total reflection-Fourier transform infrared spectroscopy indicates that the UO2(2+) complex is the principal product in the ILs.