Mathematical model of ree separation using heat oscillating extraction

The influence of periodical oscillations of the temperature on extraction and stripping processes in the extraction systems is studied. Two extraction system were investigated, No.1: 6M NaNO₃ — Nd(NO₃)₃ — Pr(NO₃)₃ — TBP — kerosene and No. 2: Nd(NO₃)₃·3TBP] — Pr(NO₃)₃·3TBP] — kerosene — 0.1M HNO₃. Mathematical model of the non-stationary membrane extraction is presented including the dependence of extraction rate constants on temperature. The values of activation energy for direct and reverse reactions of extraction and stripping reactions of Pr and Nd were calculated from experimental time dependencies of metal concentrations and temperature by solving reverse kinetics problem using the proposed mathematical model. Series of experiments with the effect of periodical temperature oscillations on the extraction system for separation of rare earth elements using bulk liquid membrane between two extractors were made. The mathematical model describes experimental data adequately. On the basis of the extraction rate constants and activation energies the optimization of the extraction process of separation of rare earth elements by liquid membrane under the effect of periodical temperature oscillations has been carried out. The optimal conditions of separation by liquid membrane were found: frequency and amplitude of thermal oscillations, liquid membrane flow rate and optimal ratio between organic and aqueous phase in the extractors.