A COMPARATIVE-STUDY OF GEL-TYPE AND MACRORETICULAR CATION-EXCHANGE RESINS FOR THE SEPARATION OF RARE-EARTH ELEMENTS

Owing to the macro- and micro- pores in the matrix, macroreticular resins have larger micro-void volume ratio in the ion exchange column chromatography. It is advantageous in the ion exchange kinetics resulting from the quicker mass transfer. By means of EDTA displacement column chromatography for the Pr-Nd separation study, we have found that macroreticular cation exchange resins have higher separation efficiency in HETP, single stage time, and the pure Pr production rate, e.g. for AG 50W-X8, 200 approximately 400 mesh resin (gel-type) and AG MP-50, 200 approximately 400 mesh resin (macroreticular), the HETP values are 0.40 cm and 0.24 cm; the single stage times are 3.11 min and 1.30 min; the pure Pr production rates are 0.19 and 0.68 m mole/hr, respectively. Because both types of resins contain the same functional group, the single stage separation factors for Pr-Nd separation have the same value of 2.0 +/- 0.1 at 92-degrees-C. The cation exchange resins which were prepared in our laboratory with higher micro-void volume ratio could improve the separation efficiency as well as reduce the pressure drop in the ion exchange column. It is suggested that new macroreticular cation exchange resins with high micro-void volume ratio and high degree of crosslinking can improve the rare earth separation efficiency which is an important design factor in the large-scale separation process for rare earth elements.