Ion-Exchange and Adsorption Column Kinetics with Uniform Partial Presaturation

Abstract

The available mathematical solutions for fixed‐bed concentration histories apply primarily to one‐component systems in adsorption and to two‐component systems in ion exchange. Thomas has developed explicit general relations for the saturation of an adsorbent bed initially free of saturating component by a fluid phase containing only this component; as well as for the converse elution situation. These results are extended here to cases of mixed binary feeds (in ion exchange), and cases of columns that are uniformly partially saturated prior to the run under study. New definitions of the dimensionless parameters that characterize the sorption processes render the existing numerical framework applicable for evaluating this broadened range of operating conditions. From the theoretical standpoint, these new parameters clarify the mathematical interrelationships between adsorption and ion exchange, between saturation and elution, and between sorption of trace components and sorption of gross or bulk components. A method is suggested for calculating physical‐adsorption operations which do not conform to Langmuir isotherms. Calculation procedures based upon this approach are illustrated by an idealized but representative example.