Electrochemical interference of some fission products during the electrodeposition of uranium oxide from 1-butyl-3-methylimidazolium chloride ionic liquid

Abstract

The electrochemical behaviour of UO22+ in 1-butyl-3-methylimidazolium chloride (C4mimCl) ionic liquid was investigated in the presence and absence of fission product ions such as palladium(II), ruthenium(III) and europium(III), by cyclic voltammetry. These fission product elements exists in significant quantities in the spent nuclear fuel and their reduction potentials are very close to the reduction potential of UO22+ to UO2. The cyclic voltammogram of UO22+ at glassy carbon working electrode consisted of a cathodic wave at −0.7V (Vs Pd) due to the reduction of UO22+ to UO2 and a couple of oxidation waves at −0.54V (Vs Pd) and 0.30V (Vs Pd). The voltammogram of UO22+ in the presence of Pd2+ showed a cathodic wave at −0.7V due to the reduction of both metal ions and three prominent anodic waves. However, The voltammogram of the ionic liquid solution containing Eu3+ and UO22+ showed a couple of cathodic waves at −0.67V and −0.9V (Vs Pd) due to the reduction of UO22+ to UO2 and Eu3+ to Eu2+ respectively. The voltammogram of UO22+ in the presence of Ru3+ was very complex. The apparent individual diffusion coefficient of UO22+, Pd2+, Eu3+, Ru3+ in ionic liquid medium was determined and compared with the apparent diffusion coefficient of UO22+ in the presence of other metal ions. The voltammetric studies and the diffusion coefficients indicated that co-existence of Pd2+, Eu3+, Ru3+ with UO22+ could reduce the current efficiency of uranium oxide deposition to a significant extent.