STATISTICAL THERMODYNAMIC MODEL FOR COMPETITIVE ION EXCHANGE

Abstract

Most models for sorption equilibria in ion exchange systems give good piedictions under well-defined conditions, but fail to give accurate predictions in industrial streams owing to undefined composition or other non-ideal influences. To alleviate the shortcomings of these models, a n;w model based on statistical thermodynamic principles and particularly the Monte Carlo method is proposed. With the use of this new method classical non-ideal behavior such as lateral interactions, heterogeneous resin surfaces and selective sorption due to steric interactions can be modeled. All the parameters used have some physical meaning and describe only a single characteristic of the sorption system. This method was applied successfully to two example systems. The first system, the more classic ideal system containing H+, K+ and Na+, was modeled almost exactly. The second concerned the sorption of gold and zinc cyanide complexes onto a strong base ion exchange resin and proved to be difficult to model with existing met...