Abstract
The present manuscript demonstrated the dissolution of oxides of uranium, mainly UO2, via surface oxidation by H2O2 into ionic liquid at ambient temperature within 4 h of equilibration. The dissolution was found to be endothermic (ΔH ∼ 30.8 kJ mol-1 and 3.20 kJ mol-1) predominantly following the pseudo 2nd order rate kinetics (k ∼ 0.004 g−1 min and 0.0009 g−1 min) with activation energies of 54.12 J mol-1 and 26.69 J mol-1, for H2O2 and RCO3H, respectively. The extent of dissolution for different oxides of uranium followed the trend UO3 > UO2 > U3O8. Within 8 h of equilibration, quantitative dissolution of 50 mg mL−1 of UO2 can be achieved with optimized experimental conditions of 0.4 M HD2EHP as the complexing agent and 10 µL H2O2 as the oxidizing agent. The oxidative dissolution followed the trend C8mim.NTf2 > C8mim.PF6. In C8mim.NTf2, the most probable species was UO2(HDEHP)2+ associated to Σg+→Γg transition involving the σu+ϕu configuration with a D3d (D3) symmetry; while for C8mim.PF6 the predominate species was UO2F2(HDEHP)- with a D3h symmetry. Four hours of electro-deposition resulted a black solid deposit on the Cu electrode resulting the change in surface morphology and enhancement in the surface roughness as analyzed by the SEM images. The EDXRF analysis revealed the presence of the uranium peak; whereas the XRD pattern showed the fluorite structure revealing the deposit of UO2 phase upon electro-deposition latter confirmed by FTIR.
Published Version
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