HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Persaud, N. Articles by Wierenga, P. J. Search for Related Content PubMed Articles by Persaud, N. Articles by Wierenga, P. J. Agricola Articles by Persaud, N. Articles by Wierenga, P. J.

A Differential Model for One-dimensional Cation Transport in Discrete Homoionic Ion Exchange Media¹

ABSTRACT

The heterogeneous system at equilibrium consisting of an aqueous solution of a counterion, I, in contact with a cation exchanger saturated with another counterion, J, was treated as a Donnan system. An equation was thus developed to describe the equilibrium adsorption isotherm of the cation I, as a function of the concentration of I and J in the equilibrium solution. This equation adequately described experimental "batch" equilibrium isotherms for selected cations on a synthetic cation exchange resin and on a natural soil material. The equation was incorporated into a differential convective-dispersive solute transport model, and the resulting differential equations were integrated numerically using an implicit finite difference scheme. Simulations were done to test the ability of the transport model to describe the elution curves for Na⁺, Li⁺, and Cs⁺ from miscible displacement experiments in water-saturated and water-unsaturated laboratory columns packed with the materials used for the adsorption studies. The model was successful in predicting the results of these experiments in the water-saturated columns. It was successful in predicting only the general shapes of the experimental elution curves in the water-unsaturated columns. These latter experimental curves were shifted to the right or left of the simulated curves and showed extensive tailing. It was concluded that other physical and chemical effects not accounted for in the transport model, such as diffusion kinetics between "mobile" and "immobile" water in the water-unsaturated columns were responsible for these discrepancies.

¹ Journal Article no. 858. Agric. Exp. Stn., New Mexico State University, Las Cruces, NM 88003.

² Research Associate and Professor, respectively, Agronomy Dep., New Mexico State Univ., Las Cruces, NM 88003.

Received for publication May 11, 1981. Accepted for publication December 28, 1981.