Dissolution of UO2, UO3 and of some lanthanide oxides in BumimTf2N:: effect of acid and water and formation of UO2(NO3)3-

UO2, UO3, Nd2O3, Eu2O3 and Pr6O11 powders were successfully dissolved in the ionic liquid 1-methyl-3-butyl-imidazolium bistriflimide (BumimTf(2)N) with the help of small amounts of HNO3. The uranyl species have been characterised through UV-vis and EXAFS spectroscopies. The uranium dissolution leads to the formation of UO2(NO3)(3)(-), even in the presence of water. The kinetics of UO2 dissolution/oxidation is intricate, due to the transient existence of NO2-, which is absent in the case of the UO3 dissolution, occurring with no change in the oxidation state of U.