EFFECT OF APPLIED VOLTAGE ON THE EXTRACTIVE SEPARATION OF RARE EARTH METALS BY D2EHPA IN THE PRESENCE OF AN OIL-SOLUBLE COMPLEXING AGENT

摘要

As a series of fundamental studies for application of an electric field to solvent extraction, and the effect of the applied voltage on the selective separation of rare earth metals was investigated using a modified Lewis cell in which the DC voltage was applied across the plane interface between organic and aqueous solutions. In this experiment of selective separation, the system of Pr and Nd in the aqueous nitrate solution and ISOPAR M containing an oil-soluble complexing agent, EDTA -DOA, and an extraction agent, D2EHPA, was used. The thermodynamic characteristics of the adsorption equilibrium of both agents at the interface between the organic and aqueous solutions, in the absence of the electric field, were also investigated by measurement of the interfacial tension. The experimental rates of Pr extraction, in the absence of the electric field, were measured by varying the stirring speed and EDTA-DOA concentration under given concentrations of Pr and D2EHPA and the rates were in good agreement with the calculated values using the extraction model proposed by Goto et al. Under the experimental conditions of hydrodynamic and mass transfer obtained in this experiment, the effects of the applied voltage, its polarity and EDTA-DOA concentration on the extraction rate of Pr and separation factor of Nd and Pr were examined.