Dissolution of Fe3O4 under cathodic polarization in EDTA solution

The most effective method for reduction of radioactivity in BWR nuclear power plants is to reduce the contamination from iron oxide deposits on the coolant pipes. Electrolytic reduction to dissolve iron oxide has been applied for the decontamination. The electrochemical behavior of the sintered Fe3O4 electrodes was studied by measuring the rest potential, polarization curve, and dissolution rate in various electrolytes. In the presence of chelating reagents such as EDTA, the dissolution rate was remarkedly enhanced. The dissolution rate was dependent on the electrode potential and two broad dissolution peaks appeared at around -0.45V and -0.9V (vs. SCE). The peak at -0.45V was caused by change in the removal rates of anion and cation species, while that at -0.95V corresponded to changes in surface compositions occurring during reductive dissolution. It was revealed that by controlling the electrode potential, Fe3O4 could be dissolved perferentially without causing corrosion of substrate iron. (author)