EQUILIBRIUM AND KINETICS OF SOLVENT-EXTRACTION OF EUROPIUM WITH DIDODECYLMONOTHIOPHOSPHORIC ACID

The rate of extraction of europium with didodecylmonothiophosphoric acid was measured by use of a stirred transfer cell, along with the extraction equilibrium. The equation for the extraction equilibrium was determined and the equilibrium constant was obtained. The dependency of the extraction rate of europium on the concentration of the chemical species taking part in the extraction was examined. By analyzing the results based on the interfacial reaction model accompanied by diffusion, it was estimated that the rate-determining step is the reaction between the adsorbed 1:2 europium chelate complex and the extractant in the organic solution adjacent to the interface. The overall reaction rate constant and the mass transfer coefficients of europium, the extractant and the complex were obtained. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.