Separation of metal ions by countercurrent chromatography using dihexyl-N,N-diethylcarbamoyl methylene phosphonate

In the present work, the batch distribution ratios of 9 lanthanide ions, Ce 3+, Nd3+, Sm3+, Gd3+, Tb3+, Dy3+, Er3+, Yb3+ and Lu3+, are measured by coun tercurrent chromatography (CCC) with 25% DHDECMP (dihexyl-N,N-diethylcarbam oylmethylene phosphonate) in cyclohexane as the stationary phase and 3.35 m ol/L HNO3 as the mobile phase. Although perfect separation of the lanthanid e ions using this system is impossible, heavy and light lanthanides can be grouped. The light lanthanides are better separated from each other. The in terested metals can be nearly completely recovered. The dynamic distributio n coefficients (D-dyn) obtained from the chromatogram are not equal to but proportional to the batch distribution coefficients (D-bat), although the D -dyn is often equal to D-bat in the separation of organic solute. This disc repancy is attributed to that the mechanism of the separation of metal ions by CCC is different from that of the organic solute. The results are consi stent with the theoretical predictions, indicating that CCC deserves to be explored as a method for investigating the mechanism of the extraction reac tions.