How do temperature and chemical structure affect surface properties of aqueous solutions of carboxylic acids?

Surface properties of binary mixtures of organic acids (formic, acetic, propanoic and butanoic acids) with water have been calculated by surface tension data at various temperatures (293.15-323.15) K. The surface tension data over the whole mole fraction range are correlated by the Li et al. (LWW) model, then the interaction energy between organic acids and water have been calculated with the results of this model. Also, adsorption isotherms of binary aqueous solutions of organic acids are determined using Gibbs adsorption equation with experimental data found in the literature and using the UNIFAC group contribution method. The values of adsorption for mixtures of organic acids/water increases with increasing the alkyl chain length of organic acid at different temperatures. Finally, the results have been discussed in terms of surface concentration and lyophobicity using the extended Langmuir (EL) isotherm. The results provide information on the molecular interactions between unlike molecules that exist at the surface and the bulk. (C) 2014 Published by Elsevier B.V.