Application of the UNIFAC mo del for Es timation o f Relative Gibbs Ad sorption and thickness of the surface la yer in the binary m ixtures

Models for calculation of surface tensions are normally based on the assumption that t he surface layer forms a separate phase with constant and unifor m composition which is different from the composition of the adjace nt vapor and liquid bulk phases. In this p aper, we use d experimental values of surface te nsion for binary mixtu res of organic acids (formic, acetic, propionic and butyric acid) with water in th e temperatur e range from ۲۹۳.۱۵ K to ۳۲۳.۱۵ K. The acti vity coefficients in surface and bulk were evaluated using t he UNIFAC group contribution model and the n this coefficients is use d to estimate the relati ve Gibbs ad sorption and the thickn ess of surfa ce layer. W e compare these measu rements with calculati ons of the lengths of molecules based on m olecular modeling usin g Hyperchem software [۱, ۲].

کلیدواژه ها:

Surface tension ، Ads orption ، UN IFAC ، Thickness ، Binary mixture