The importance of the extraction medium and its film geometry to the separation efficiency is illustrated by the example of
the chromatographic extraction systems HDEHP-HCl-Eu3+ and TBP-HNO3−Sc3+. Starting from the geometry of the matrix, the effects of the exchange kinetics and flow pattern were experimentally proved.
Exchange kinetics are described as a heterogeneous transport-limited reaction in the aqueous phase. Four ranges of the rate
of exchange with the geometry of the matrix (pore diameter) were found. The flow patterns in the chromatographic layer can
be established by the individual pore cross-sectional area of the matrix. The sum of the effects of exchange kinetics and
flow patterns determines the chromatographic efficiency of the systems. Their relative effects in the two systems being investigated