CORRELATION OF THE MUTUAL DIFFUSION-COEFFICIENTS OF BINARY-LIQUID MIXTURES

A correlative UNIDIF model for the mutual diffusion coefficients of bi nary liquid mixtures is developed using statistical thermodynamics and the absolute reaction rate theory. In this model, a mole fraction ave rage of the logarithm of the pure-component limiting diffusion coeffic ients is taken as a reference term. The model expresses the excess par t of the diffusion coefficient relative to this reference term in a fo rm similar to that of a UNIQUAC equation which comprises two parts due to the combinatorial and residual contributions. The combinatorial pa rt depends on the molecular sizes and shapes. The residual part includ es two binary interaction parameters, which are obtained from data reg ression, for each binary mixture. Mutual diffusion coefficients of non polar + nonpolar, nonpolar + polar and polar + polar fluid mixtures ar e correlated in this study. Optimal binary interaction parameters are presented. Correlation results using the UNIDIF model for mutual diffu sion coefficient are satisfactory and are superior to those from other methods. (C) 1998 Elsevier Science B.V. All rights reserved.