FORMATION OF W/O MICROEMULSIONS IN THE EXTRACTION SYSTEM RH(III)-HCL-KELEX-100 AND ITS IMPACT ON RH(III) DISTRIBUTION

The extraction behavior of chloro complexes of rhodium (III) into an organic phase of Kelex 100 extractant has been investigated from the standpoint of aquation and microemulsion formation. The aquation of Rh-chloro complexes has been confirmed experimentally to be the main factor which suppresses the liquid-liquid extraction of rhodium. In addition, the formation of Kelex 100-acid-water aggregates in the organic phase has been unequivocally demonstrated by performing various measurements such as water uptake, viscosity, interfacial tension, and light scattering. Due to aquation which is promoted by the formation of microemulsions, very limited overall rhodium extraction can be effected by direct liquid-liquid extraction. (C) 1995 Academic Press, Inc.