COUNTERCURRENT CHROMATOGRAPHY AND REVERSE MICELLES FOR SEPARATION ANDEXTRACTION OF METAL-CATIONS

Countercurrent chromatography (CCC) is a separation technique in which the stationary phase is a liquid. Diethylhexyl phosphoric acid (DEHPA ) forms reverse micelles in heptane. Metallic ions, located in an aque ous phase, can be extracted into the aqueous core of the reverse micel les in the heptane phase. A CCC apparatus can be considered as a power ful mixing and extracting machine with efficiency above several hundre ds of theoretical plates. La3+, Ce3+, Pr3+, and Nd3+ lanthanide cation s were separated using CCC with a DEHPA-containing heptane stationary phase. Studying the retention variations with aqueous mobile phase pH, it was possible to determine the lanthanide extraction constants and separation coefficients. Overloading conditions are described. Frontal chromatography was performed using a Co2+ and Ni2+ solution. The Co2 ions were concentrated in the heptane + DEHPA stationary phase, a par t of the solution was deionized, and another part was enriched in only Ni2+ ions. This method also produced the extraction constants and sep aration coefficients. The use of CCC with a complexing stationary phas e can be applied to any cation for ion filtering and concentration, or for deionization of aqueous phases.