Data processing of cation exchange equilibria in zeolites: a modified approach

After reviewing the fundamental literature concerning the equilibrium of binary cation exchange reactions on zeolites, this paper provides a straightforward procedure of computation of their thermodynamic parameters, Kα and ΔGo, based on a method of evaluation of cations activity coefficients in solution, which is simple and accurate and is equipped with a sufficiently large data-base. The computation procedure was tested on isothermal equilibrium data of Cd2+ and Zn2+ exchange for Na+ in zeolite A at 25.0°C and 0.05, 0.10, and 0.50 total normality, by calculating their Ka and ΔGo and by comparing these results to those obtained evaluating the cations activity coefficients through a reference largely used method and to previous literature data. The results obtained show that the proposed methods give results in good agreement with those obtained with the reference method so that it appears to be a good alternative for the determination of cation activity coefficients in solution.