Optimization for removal of ruthenium from nitric acid solution by volatilizing with electrochemical oxidation

Sato, Soichi ; Endo, Noboru; Fukuda, Kazuhito ; Morita, Yasuji  

Electrochemical oxidation method, to oxidize nitrosyl ruthenium to the tetra-oxide and then to remove ruthenium to the gas phase, was studied to separate Ru from the high-level liquid waste (HLLW). We carried out the experiments to clarify the effects following fundamental conditions to the electric oxidation, which are (a) electrolyte temperature, (b) presence of promoter elements, (c) evaporation or reflux of condensed phase and (d) using or not using of diaphragm at counter electrode. We found the fast oxidation conditions as follows; (1) higher temperature; 95C, (2) Ce coexistence; 3000 ppm and (3) usage of a diaphragm for counter electrode. However evaporation or reflux conditions do not directly affect the electrochemical oxidation efficiency. Electric oxidation rate was increased 3 times compared with 25C, without Ce and diaphragm for counter electrode.