Abstract: The ion exchange isotherms, the corrected selectivity coefficients and the rational thermodynamic equilibrium constants of the weak base anion resin 710A have been determined for the SO_4~(2-)-Cl~-, NO_3~--Cl~- and NO_3~--SO_4~(2-) systems at 25 ℃. The comparsion of the ion exchange equilibria between the weak and the strong base anion resins were reported. The affinity sequence of the strong and the weak base anion resins for the sulphate, nitrate and chloride are in agreement with the theoretical predictions. The SO_4~(2-)-Cl~--NO_3~- system ternary isotherm was also determined on the weak base anion resin 710A at 25 ℃. The predictions of the ternary system based solely on the binary data are consistent with the experimental data found for this system as did for the SO_4~(2-)-Cl~--NO_3~- -strong base anion resin system.

Key words: Binary ion-exchange equilibrium, Ternary ion-exchange equilibrium, Strong base anion resin, Weak base anion resin