Effective isotherms and equilibrium characteristics of a weak acidic cation resin

Abstract

The equilibrium properties of a weak acidic cation resin were studied theoretically and experimentally. Equations were derived for the effective isotherm of this type of resin. The derived equations are applicable to the exchange of hydrogen ions with any metallic ions with a valence of n. Based on equilibrium theory, theoretical breakthrough curves were derived from the effective isotherm expressions. Experiments were performed using IRC-50, a weak cationic resin. Column runs were conducted with 0.05 to 0.1 N of both NaCl and Ca(NO3)(2) solutions. The experimental breakthrougough curves obtained for both Na+ - H- and Ca+ + - H+ exchange show that the breakthrough occurs very early and that the operating capacity is only 2-3% of the ultimate capacity of the resin. Comparing the theoretical breakthrough curves with the experimental ones suggests that the value of the normalized dissociation constant is between 0.001 and 0.003, and that for both the Na+ - H+ and Ca+ + - H+ exchange systems, the normalized selectivity coefficient is between 0.2 and 0.5.