5.1. Processes of ion exchange, adsorption and hydrolysis
Ion exchange process is characterized by the capacity, selectivity and kinetics of the exchange. Capacity is needed in several determinations, such as the normalization of equilibrium isotherms and the application of kinetic models in order to determine the ion-exchange diffusion coefficients (Table 5). Differences in the exchange isotherms derived by different researchers for the same ion-exchange systems are mainly due to the assumption of different cation-exchange capacities of zeolitic materials.
IUPAC recommendations for ion-exchange nomenclature define the following capacity types: “Theoretical (specific) capacity, apparent capacity (effective capacity)”, “Practical (specific) capacity”, “Useful capacity” and “Breakthrough capacity” [46].