In-situ measurement of UO22+ concentration in molten NaCl-2CsCl by differential pulse voltammetry

Abstract

In order to assess the applicability of the Differential Pulse Voltammetry technique to the in-situ measurement of UO22+ concentration in the oxide electro-winning process, DPV measurements for UO2Cl2 in molten NaCl-2CsCl were studied. DPV measurement of UO22+ in NaCl-2CsCl at 923 K, with a set of optimized parameters (potential sweep rate −0.1 V/s, pulse cycle 0.1 s, pulse width 10 ms and pulse potential height 50 mV), showed a clear current peak at −0.9 V vs. Cl2/Cl−. This was attributed to the reduction of UO22+ to UO2+. The relation between the current peak height and the analytical concentration of the UO22+ showed good proportionality in the concentration region up to 0.06 mol.l−1, and the applicability of UO22+ concentration measurement by DPV was confirmed up to 0.4 mol.l−1. In order to assess the interference by the coexisting fission product elements to the measurement of UO22+ concentration, DPV measurements of UO22+ concentration in molten NaCl-2CsCl containing PdCl2, NdCl3, SmCl3 and CeCl3 were also performed. Even before removing Pd, the current peak at −0.9 V vs. Cl2/Cl− by the reduction of UO22+ to UO2+ was found to be distinguishable from the reduction currents of Pd2+ to Pd at −0.7 V vs. Cl2/Cl−. As a result, the application of DPV measurement technique to the in-situ monitoring of UO22+ concentration in the oxide electro-winning method requires the improvement of the DPV measuring condition or the electrode structure on higher UO22+ concentration condition. © 2006 Taylor and Francis Group, LLC.