The extraction rate constants from the independent experiment with one extractor (Lewis cell) on rare earth elements´ (REE) mass transfer kinetics study were received. Two extraction systems were investigated, №1: 6M NaNO3 - Nd(NO3)3 - Pr(NO3)3 - three-n-butylphosphate (TBP) - kerosene and №2: [Nd(NO3)3·3TBP] - [Pr(NO3)3·3TBP] - kerosene - 0.1M HNO3.
Received data was set in the developed mathematical model of extraction kinetics. Calculated kinetics curves match well with experimental ones.
The series of experiments with extraction of REE under conditions of periodical thermal oscillations with low mass transfer in both extraction systems were worked out. The influence of periodical oscillations of the temperature on extraction and stripping processes in the extraction systems is studied. Mathematical model of the non-stationary membrane extraction is enhanced 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 temporal dependencies of metal concentration and temperature by solving reverse kinetics problem using proposed mathematical model.
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 influence of periodical oscillation of the temperature is carried out. The optimal conditions of separation by liquid membrane were found: frequency and amplitude of thermal oscillations, effective boundary area and liquid membrane flow rate.
The series of experiments with influence of periodical oscillations of the temperature on the extraction system using bulk liquid membrane between two extractors were carried out. The following extraction system was investigated: 6M NaNO3 - Nd(NO3)3 - Pr(NO3)3 - TBP - kerosene - 0.1M HNO3 with 0.5M TBP in kerosene as bulk liquid membrane. The mathematical model describes experimental data adequately.
Acknowledgements. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under grant RC0-20000-SC14 and RUC2-20011-ST-04 administered by the Civilian Research and Development Foundation.
The article is admitted to the International Scientific Conference "Contemporary Scientifically Based Technologies", Spain, Tenerife, 2006, November 20-27; came to the editorial office on 27.02.06.