Mohammad Nader Lotfollahi - Department of Chemical Engineering, Semnan University, Semnan

The activity coefficients of ions in the several ternary systems have been calculated by the UNIQUAC model. Using these values of activity coefficients in the equilibrium equation , the solubilities of solids in the aqueous electrolyte solutions have been calculated. These calculations are performed for Na2SO4-NaCl-H2O, Na2SO4,10H2O -NaCl-H2O, K2SO4-KCl- H2O and K2SO4-Na2SO4-H2O systems. The comparison of the calculated results with the experimental data shows that the UNIQUAC model is able to give a good representation of the solid-liquid phase equilibria in these mineral solutions in the whole temperature range from 273.15 to 373.15K.

SLE calculation; UNIQUAC model; electrolyte solutions