REDUCTION OF ION-EXCHANGE EQUILIBRIA DATA USING AN ERROR IN VARIABLES APPROACH

An error in variables method (EVM) was used to reduce binary ion-exchange equilibria data. Ion-exchange equilibria data were collected via batch equilibrium experiments. Three binary ion-exchange systems were studied: the Na+1-Cd+2, Na+1-Cu+2, and Cu+2-Cd+2 systems with a strong acid synthetic ion-exchange resin. The Wilson model and a three-suffix, two-parameter Margules equation were used to model the dependency of the resin phase activity coefficients with resin-phase composition. The EVM was used to determine the best-fit estimates of the Wilson and Margules equation binary resin-phase activity coefficient parameters. Statistical analysis of the data fits indicates that although both equations were able to adequately model the resin phase nonidealities, the Wilson model provided the superior data fits based on the minimized objective functions.