Prediction of multicomponent ION exchange equilibria by using the e-NRTL model for computing the activity coefficients in solution

Abstract

The e-NRTL model for computing the activity coefficients in solution of electrolytes was used for the first time, as the best of our knowledge, together with the Wilson's equation for evaluating the non-ideal behavior of the resin phase, in the prediction of multicomponent ion exchange equilibria. For this purpose, experimental data for the binary systems Ni2+/Na+ and Zn2+/Na+ and the ternary system Ni2+/Zn2+/Na+ using Amberlite IR-120 reported by Franco et al. [1] were considered. The results obtained showed that the major impact over the equilibrium modelling was caused by the inclusion of the Wilson's equation demonstrating the predominant effect of the non-ideality of the resin phase. No significant differences in the results (for the systems and ionic concentrations explored here) were observed when Bromley, Pitzer and e-NRTL equations were used to predict the activity coefficients in solution. Regarding the prediction of the multicomponent equilibria, it can be said that the most complex models: Pitzer's and e-NRTL ones, yield the best results. Again, the major impact in the improvement of the prediction was the inclusion of the Wilson's parameters. Finally, since the e-NRTL model allows to indistinctly work with both electrolytes and non-electrolytes, it could be possible to design modules for simulating the ion exchange operation in process simulations software like Aspen Plus®.