ali haghtalab - department of chemical engineering tarbiat modares university tehran iran
mohamadjavad kamali - department of chemical engineering tarbiat modares university tehran iran

For calculation of surface tension, the aqueous electrolyte solution is divided into three parts: liquid, surface and vapor phases. Using the Langmuir gas-solid adsorption and equality of adsorption and desorption rate for an electrolyte in surface phase, the molality of each electrolyte is obtained at the surface. For calculation of the molality of mixed aqueous electrolyte solution in the surface layer, based on the competition or non-competition between the electrolytes for adsorption in the surface layer, the two approaches are used. Using these approaches and applying the Gibbs thermodynamic, the surface tension of the binary and ternary aqueous electrolyte solutions is calculated. The new model has two adjustable parameters for calculation of the molality in the surface phase that can be determined by fitting the experimental surface tension of the binary aqueous electrolyte solution at a given temperature. For the other temperatures, the values of the surface tension of the binary and ternary aqueous electrolyte solutions are predicted. Calculation of the osmotic coefficient of the electrolyte solutions are performed using the Pitzer, E-NRTL and N-Wilson-NRF functions. Using the new model and the other surface tension models and the E-NRTL, the best average absolute deviation for the surface tension of the 65 binary aqueous electrolyte systems and the 16 ternary aqueous systems are obtained, that are 1.98 and 1.59%, respectively. Also the results of the new model are compared with the three previous models that it indicates the satisfactory results of the new model with respect to the others.

surface tension,aqueous electrolyte solution,langmuir adsorption,activity coefficient