Application of the mass action law to describe ion exchange equilibrium in a fixed-bed column

Ion exchange experiments were carried out in a fixed-bed column employing the binary systems Cu2+–Na+ and Zn2+–Na+. Amberlite IR 120 was used as the ion exchange resin. The ion exchange dynamics within the column was described by a model considering the external mass transfer and the diffusion within the particle. A linear driving force model was used to represent the mass transfer within the resin particles. The model considered the thermodynamic equilibrium on the liquid–solid interface, which was described by the Langmuir isotherm and by the mass action law. The results indicate that both models represent well the ion exchange dynamics in all cases.

► Mass action law describes satisfactorily ion exchange equilibrium.
► The internal and external mass transfer limitation should be considered.
► Linear driving force model can be used as approximation of the Nernst–Planck model.
► The models can be used to design a fixed-bed column.