Modeling of the Simultaneous Extraction of Nitric Acid and Uranyl Nitrate with Tri-n-butyl Phosphate. Application to Extraction Operation

A mathematical model developed for the equilibrium HNO3‒UO2(NO3)2-tri-n-butyl phosphate (TBP)-diluent is the basis of the computation of distribution isotherms. The isotherms are used to study the influence of TBP concentration on two chosen operation parameters, distribution coefficients and number of theoretical stages, for the selected flow sheets. It is established that an increase in TBP concentration leads to a decrease in the number of theoretical stages for the extraction flow sheets but to their increase for the stripping flow sheets. Given diagrams can be used to determine the efficiency of extraction processes. Agreement with available literature calculations on the number of theoretical stages supports the use of our model in the computation of distribution isotherms, of the system quoted above, in a wide range of nitric acid, uranyl nitrate, and TBP concentrations.