Studies on Electrochemical Generation of Ceric Ions in Nitric Acid Medium

Abstract

Cerous/ceric redox couple is considered as a potential Mediated Electro Oxidative (MEO) catalyst in the electro-oxidative dissolution of difficult-to-dissolve trans-uranic elements in the concentrated nitric acid medium. The electrochemical oxidation behavior of Ce III in 11.5 M HNO 3 was investigated by cyclic voltammetry (CV) using two different working electrodes platinum (Pt) and glassy carbon (GC) at 298 K. At higher acidity, cerous to ceric oxidation on GC working electrode was found to be a reversible process contrary to a quasi-reversible observed at Pt working electrode. To compare the current efficiency in electrochemical cells for the oxidation of Ce III ions, lab and bench scale oxidation of 0.05 and 0.5 M Ce III in 11.5 M nitric acid was performed in divided and undivided cell assemblies using Pt electroplated Ti (PET) or pure Pt gauze as anodes. Almost 100% yield for Ce IV could be achieved in divided cells and under identical conditions; the conversion efficiency was 30% lower in undivided cells. These studies revealed the concentration dependence of Ce III besides cell potential and temperature on the rate of oxidation.