Kinetics of Exchange Reactions in a Cation-Exchange Resin

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Abstract
The kinetics of the exchange reactions of several cations from aqueous solution by protons from a sulfonated polystyrene resin have been studied in detail. The reaction rate is first-order with respect to both the resin and the cation concentrations and increases with the stirring velocity. The activation parameters for the exchange of Mg2+, Cu2+, Cr3+, and Fe3+ ions have been determined. A ΔH‡ vs ΔS‡ plot for these reactions is linear, yielding an isokinetic temperature of 333 K. The rate of reaction appears to increase with increasing ionic radius and to decrease with increasing electrostatic charge of the cation to be exchanged. The rate-controlling step seems to be diffusion through the aqueous layer surrounding the resin particles.