Surface tension of aqueous electrolyte solutions at high concentrations - representation and prediction

A calculation method was developed for representing and predicting surface tension of aqueous electrolyte solutions over a wide range of concentration s, up to 36 m. Based on the Gibbs dividing surface concept, the Langmuir ad sorption equation was adopted for modeling the surface excess of electrolyt e(s). The activities of electrolytes in the aqueous solutions were calculat ed by the Fitter equation. The surface tensions for 45 aqueous single-elect rolyte systems at a single temperature were used to correlate the model par ameters, and the correlation yields an overall average absolute percentage deviation (AAPD) of 0.47. Surface tensions for 23 aqueous inorganic electro lyte systems are available at several temperatures. Application of these mo del parameters to extrapolate surface tensions of these systems to differen t temperatures yields an overall AAPD of 0.91. The proposed method was succ essfully applied to predict surface tensions for an aqueous binary electrol yte system containing a free acid (HNO3) and its salt (KNO3), which have op posite effects on surface tension with an increase in their concentrations, with an overall AAPD of 1.87. The predicted surface tensions for additiona l 11 binary and five ternary mixed-electrolyte aqueous systems indicate an overall AAPD of 1.69. (C) 2001 Elsevier Science Ltd. All rights reserved.