Equilibrium model for the selective sorption of gold cyanide on different ion-exchange functional groups

Abstract Ion exchange resins are still not used commercially for gold extraction from leached pulps despite the many advantages of ion exchange resins over activated carbon. This is a result of the poor understanding of the chemistry involved and a lack of a rigorous method of modelling, design and scale-up. The present study describes a theoretical model based on the principles of statistical thermodynamics as well as the Metropolis Monte Carlo (MMC) numerical method that has been proposed previously to describe multi-component sorption equilibria. An important aspect of this modelling approach is that it does not use any solely empirical parameters. All parameters used describe only a single characteristic of the sorption system. It is therefore possible to include fundamental information of the system in order to facilitate easier parameter estimation. The model explicitly describes in a mathematical form classical non-ideal sorption phenomena such as selectivity, irreversibility and interaction between sorbed species which previously have only been understood from a chemical viewpoint. The model has been used to successfully describe the multicomponent equilibrium sorption of gold cyanide and copper cyanide onto ion exchange resins containing different aliphatic amino groups. Consequently, by varying the surface properties and comparing the model predictions with experimental data, further insight has been gained into the sorption properties of ion exchange resins for metal cyanide complexes.