Modern Theory for Multicomponent Ion Exchange Equilibria and Chromatographic System Behavior in Columns

Abstract

Theoretical description, including computerized simulation of the dynamic behavior of multi-component ion exchange (IEx) chromatographic systems for the displacement-elution regime in column is presented. Multi-component IEx equilibria used for the simulation of IEx dynamics have been described by the modern theoretical approach called by the German authors as the “Surface Complexation Theory” (SCT-Model). The main proposal in the SCT-Model is that the fixed groups of any ion exchanger form Surface Complexes with counter-ions of the components. By computerized simulation the dynamic behavior of the multi-component concentration waves formed by the displacer ions (H⁺ or Na⁺) including two various components Me₁ ⁺ and Me₂ ⁺ eluted during the displacement-elution dynamics in the IEx columns is analyzed. The term “wave” reflects one of the fundamental concepts applied in the theory of chromatography.[1–3] The behavior depends on SCT-parameter values, used in the SCT-Model for multi-component equilibria. The experimental SCT-parameters obtained previously for a number of ion exchangers are used for the computerized simulation of the dynamic processes on the basis of differential mass balance equations.

Keywords:

• mass transfer
• ion exchange
• multicomponent
• theory of dynamics
• equilibria
• concentration distributions
• fixed bed
• surface complexes
• displacement-elution
• computerized simulation

ACKNOWLEDGMENTS

The author wishes to express his deep gratitude to Professor Wolfgang H. Höll for his encouragement and friendly support of our collaborative work over the last 12 years. This research was effectively supported by the German DFG, and DAAD Foundations.