Preferential transport behaviors of ternary system cupric–nickel–zinc ions through cation-exchange membrane with a complexing agent by dialysis

Preferential transport behaviors of ternary metal ion system were studied in a stirred batch cation-exchange membrane dialyzer. Cu2+–Ni2+–Zn2+ system was chosen for investigation. Malonic acid, oxalic acid and citric acid were employed, respectively, as a complexing agent in order to enhance the discrepancy in transport fluxes of metal ions. The results show that the effective order of complexing agents is malonic acid > oxalic acid > citric acid. The stoichiometric ratio of complexing agent to metal ions and the pH value of the feed solution are the primary factors on the preferential transport behaviors of metal ions. The optimal dimensionless permeation flux ratio of PZn–Na/PNi–Na/PCu–Na is obtained about 5.3/3.6/0.7. On the basis of the Nernst–Planck equation and interface equilibrium, a theoretical model of the system is established. The predicted results obtained by theoretical model are in good agreement with the experimental results.