Ion exchange on a chelating resin: Multicomponent equilibrium predictions using binary data

Highly selective chelating ion exchange resins are an attractive option for metal removal from wastewater due to their ability to separate mixed metals for recovery and reuse. The ability of the chelating resin Amberlite ® IRC-718 to separate copper, cadmium and sodium ions from solution has been experimentally examined. It was found this resin shows strong preference for copper over cadmium, and an even stronger preference for both of these ions over sodium. The adsorption isotherms for this resin are very non-ideal for the monovalent-bivalent pairings. A series of experiments containing all three ions was also performed.; In addition, this work examines the performance of five literature models in representing the experimental data, notably their prediction of ternary behavior using parameters fit from binary data. All models were based on equilibrium partitioning of the ions between the resin and the solution, and varied in complexity using between one and four adjustable parameters. The Error in Variables method was used to estimate model parameters, and the resulting fit was subjected to rigorous statistical examination. The severe non-ideal behavior of the chelating resin presents a challenge for the models. The results were mixed: although the models represented the binary data adequately, statistical analysis suggested potential bias in the estimates, and the ternary predictions were generally poor. Possible explanations for these problems are presented.; Data from literature were also examined to further evaluate and compare model performance. The ternary predictions were much closer to the experimental observations than for the chelating ion system. Thus it can be concluded that these models were successful at representing the data sets for various resin-ion systems to a degree sufficient for preliminary engineering design, and to reduce the number of experimental screening trials needed to develop multicomponent ion separation.