Multicomponent ion exchange equilibria. I. Zn 2+−Cd 2+−H + and Cu 2+−Ag +−H + on amberlite IR 120

Abstract

Binary and ternary ion exchange equilibria have been studied by the batch technique using the strong-acid cation exchanger Amberlite IR 120. The following binary equilibria were studied, starting in almost all cases from either of the pure homoionic forms of the resin involved: (i) Zn 2+ − H +, (ii) Cd 2+ − H +, (iii) Zn 2+ − Cd 2+, (iv) Cu 2+ − H +, (v) Ag + − H + and (vi) Cu 2+ − Ag +. Also, the following ternary exchange equilibria have been studied, starting from the H + form of the resin: (i) Zn 2+ − Cd 2+ − H + and (ii) Cu 2+ − Ag + − H +. For the binary exchange equilibria, the thermodynamic equilibrium constants have been calculated assuming the ideal solid solution model of Argersinger et al; the specific ionic interactions in the solution phase insofar as these affect the corresponding ionic activities have been taken into account in the calculation. The ΔG values of the three exchange reactions, which together constitute a “triangle” in case of either of the two exchange systems, are found to be in good mutual agreement. For the ternary exchange systems the possibility of predicting ternary data by use of the pair of binary exchange results containing the most preferred ion was examined. The graphical procedure suggested by Streat has been used, and the correlation between the experimental and the theoretically predicted results has been found to be reasonably good for both the above ternary systems.