1987 Volume 36 Issue 3 Pages 127-133
The dissolution behavior of chromium-rich oxides in sulfuric acid-cerium (IV), SC, solution has been investigated in connection with developing a chemical decontamination process for nuclear facilities. Each dissolution rate of Cr, Ni, and Fe components in the oxide, Cr0.6Ni0.6Fe1.8O4, greatly depends on the redox potential and pH of the SC solution. The magnitude of their rates is in the following order: Fe>>Ni>Cr=0 in 0.25M H2SO4 without Ce4+ and Cr>>Ni>Fe in the SC solution, indicating that the rates of Cr and Ni increase in an oxidative solution. The rate of Cr is a first order dependence on Ce4+ concentration. The amount of Ce4+ required to dissolve the oxides can be calculated if the amount of the oxides and their components were known. Namely, the dissolution is governed by redox reactions, in which Fe (II) and Cr (III) in the oxides are completely oxidized to Fe (III) and Cr (VI), but Ni (II) and Fe (III) unchanged. The difference in the total dissolution fractions between in the SC and HNO3-Ce4+ solutions suggests that the ability of a decontamination solution to dissolve the oxides should be evaluated not only by their initial dissolution rates but also the total amount of the oxides dissolved.