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Distribution of Uranyl Nitrate and Nitric Acid Between Aqueous Solutions and 30 Volume Percent Tributyl Phosphate in Hydrocarbon Diluent

Stephen M. Goldberg, Manson Benedict, Hans W. Levi

Nuclear Science and Engineering

Volume 47 / Number 2 / February 1972 / Pages 169-186


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Equations, tables, and charts are given which represent the equilibrium distribution of uranyl nitrate and nitric acid between aqueous solution and an organic phase consisting of 30 vol% tributyl phosphate (TBP) in a hydrocarbon diluent at 25°C. These should be useful for prediction of distribution equilibria in the Purex solvent extraction process for recovering uranium from irradiated nuclear fuel. Equations for the aqueous phase represent the activities of water, nitric acid, and uranyl nitrate hexahydrate as functions of the molality of the last two components. These equations were developed by correlating data for the partial pressure of nitric acid over aqueous solutions of nitric acid and uranyl nitrate. Distribution equilibrium data for uranyl nitrate are correlated by an equation representing the ratio of the activity coefficient of the uranyl nitrate-TBP complex to the activity coefficient of uncomplexed TBP as a function of the uranyl nitrate and nitric acid content of the organic phase. This equation was fitted to distribution data for uranyl nitrate observed in the presence of nitric acid and in the absence of nitric acid. The observed molality of uranyl nitrate in the organic phase agrees with the molality predicted by this equation within an average deviation of 5.8%. Distribution equilibrium data for nitric acid in the presence of uranyl nitrate were correlated in analogous fashion.

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