Abstract
In chemical uranium enrichment, which is a multi-stage separation process utilizing adsorption-desorption reactions, the results of enrichment experiments conducted at various temperatures between 55°C and 130°C with an solution containing certain non-uranium metal ions indicated that the degree of separation obtained with maximum enrichment at the end boundary of the uranium adsorption band is approximately 10 times as great as when no such metal ions are present. (This result is expressed as α0 which is a normalized value for 1h of separation operation.) This striking improvement in enrichment behavior was attributed to the acceleration of the electron exchange reaction between U4+ and UO22+ by the catalytic effect of the coexistent metal ions, because, under the experimental conditions used in this investigation, the rate determining step of reactions in the enrichment process is reportedly the electron exchange reaction. In addition, an examination of the catalytic reaction mechanism of the electron exchange from the viewpoint of the free energy levels of various oxidation states of the coexistent metal ions strongly implied that the catalytic effect is dependent on differences in the free energy levels of the oxidation states of the metal ions added, which correspond to the standard redox potentials of these metal ions.
