Reactions of Am(Iii) and Eu(Iii) with Potassium Ferricyanide in Nitric Acid Solutions

Summary The reactions between Am or Eu present in 0.1 M nitric acid solutions, alone or both together, with 0.25 M K3Fe(CN)6, were studied at room temperature. When Am was the only trivalent metal ion in solution, precipitation of AmFe(CN)6 occurs and the residual Am concentration is about equal to 0.95 mM. However, when Am initial concentration is less than the above specified value for AmFe(CN)6 solubility, Am residual concentration measured is lower that its concentration in the initial solutions. The solubility of EuFe(CN)6 was found to be equal to 30 mM. However, when precipitate formation occurs, the Eu residual concentration after phase separation is about in average 8 mM. When Am and Eu were simultaneously present at the same concentration in solution, the solubility of Am differs little from that measured with Am alone. For initial Am concentrations below 1 mM, the solubility of Am is higher than that observed in the absence of Eu. For initial concentrations of about 8 mM, the Am solubility is lower (about 0.7 mM) than that observed for Am alone. When the initial Eu concentration is constant at 29 mM, the Am precipitation efficiency is much higher than observed in the absence of Eu, for Am concentrations between 30 and 0.5 mM. The residual Am concentratixon in solution thus drops considerably in the presence of Eu (29 mM), and is about 0.04 mM for initial Am concentrations below 4 mM.