In this work, ion exchange equilibrium in NaY-packed columns was examined and equilibrium data was generated for Na+ <-> Fe2+ in zeolite. In this context, different mathematical models were evaluated to describe the equilibrium: the through adsorption approach (Langmuir type model, Jain & Snoeyink model and Langmuir-Freundlich model), the ion exchange approach (the ideal and non-ideal mass action law) and the thermodynamic approach (LAST ideal adsorbed solution theory and RAST real adsorbed solution theory). Experiments were carried out at 30 degrees C using solutions of 1, 2 and 3 meq L-1 at pH 4.5 and a column flow rate of 8 mL min(-1). Fe(II) was retained through ion exchange followed by adsorption. The non-ideal mass action law best fit the experimental data as it predicted the exchange process of electrolytes and detected the adsorption multilayer. (C) 2014 Elsevier B.V. All rights reserved.