A simplified resistance model for reversible multicomponent ion exchange

Ion exchange resins have found increasing application in the metallurgical sector over the last few decades through resin-in-column (RIC) technology. These processes are usually simulated by using some form of resistance model. Furthermore, of these, a dual resistance approach incorporating both film and pore-wall diffusion is the most popular and widely used technique for simulations involving ion exchange and adsorption processes. This procedure assumes that equilibrium exists at the solid/liquid interface, an assumption easily applied to single-component systems. However, in multicomponent systems, this assumption makes the simulation procedure cumbersome. In addition, the inability of frequently used isotherms to accurately describe equilibrium conditions over a wide range of solution concentrations results in significant errors. This study investigates the use of a simple film-diffusion mechanism to describe mass transfer kinetics. Furthermore, a simplified Fritz and Schleunder isotherm was used to overcome complex iterative techniques in order to obtain equilibrium conditions at the solid/liquid interface. The procedure was evaluated using a chelating resin in a ternary system and proved to be very effective with reversibility well explained. Moreover, it has been shown that the effect of the counterion may be ignored in batch operations but not in column configurations because of the significant increase of the counterion in solution. (C) 2004 Elsevier B.V. All rights reserved.