| 摘要 |
<p>According to the present invention, prior to evaporation treatment of a ruthenium-containing nitric acid solution (2), ruthenium ions in the nitric acid have been converted into a nitrosyl ruthenium complex compound in which nitro group (NO2) is coordinated and the thus pretreated ruthenium-containing nitric acid is supplied to an evaporation apparatus (9). When the nitric acid solution (2) where ruthenium is in the form of a nitrosyl ruthenium complex compound in which nitro group is coordinated is supplied to the evaporation apparatus (9) the nitro group coordinated in the nitrosyl ruthenium complex compound is replaced with nitrato group. During this replacement, oxidation-reduction potential of the nitric acid solution (2) is kept low while release of nitro group continues and oxidation decomposition of ruthenium nitrosyl nitrato complex and oxidation into ruthenium tetraoxide as a final product are inhibited and thus volatilization of ruthenium is inhibited.</p> |
