Pii: S0378-3812(00)00396-4

The concentration dependence of the surface tension of single and mixed electrolyte aqueous solutions is studied, based on the assumption that the surface layer can be treated as a separate phase located between vapor and bulk liquid phases. The mean spherical approximation modified by Lu et al. [J.-F. Lu, Y.-X. Yu, Y.-G. Li, Fluid Phase Equilibria 85 (1993) 81–100] is used to calculate the activity coefficients of water in the surface and bulk liquid phases. The relation between the electrolyte concentration in the surface and bulk liquid phases is established and only one parameter needs to be determined. The surface tensions for 31 single electrolyte aqueous solutions are correlated and the overall average absolute deviation is 0.70%. The surface tensions at different temperatures are predicted with the parameters obtained at one fixed temperature. By introducing the proper mixing rules, the surface tensions for 14 mixed electrolyte aqueous solutions are predicted without any mixing parameters, and the total average absolute deviation is 0.63%. All the calculated results are compared with that of the surface tension model for aqueous electrolyte solutions proposed by Li et al. [Z.-B. Li, Y.-G. Li, J.-F. Lu, Ind. Eng. Chem. Res. 38 (1999) 1133–1139]. © 2000 Elsevier Science B.V. All rights reserved.