SELECTION OF COMPETITIVE ADSORPTION MODEL FOR MODELING DISPLACEMENT CHROMATOGRAPHY

The influence of the model used to describe the basic competitive interactions between a stationary phase and migrating solutes was investigated to simulate reversed-phase displacement chromatography. Experimental separations of catechol-resorcinol mixtures using phenol as the displacer were compared with numerical simulations. The competitive Langmuir model, the LeVan-Vermeulen model and the quadratic model were chosen to describe the competitive adsorption equilibria. These models were related either to their non-competitive parameters or to their competitive parameters. A novel simplified experimental procedure is proposed to obtain competitive parameters for a binary mixture. The chromatographic process is described by the equilibrium-dispersive model and the calculations were performed by using a finite difference method. The results demonstrated that competitive isotherm equations with numerically fitted parameters do not lead to a good description of a displacement separation process. On the other hand, the LeVan-Vermeulen isotherm, with non-competitive Langmuir parameters, was found to be a relevant choice to the experimental conditions involved.