The solution-diffusion model - Order of magnitude calculation of coupling between the fluxes in pervaporation

In this paper, we develop an expression of Fick's law to be used in the dif fusion-solution model when coupling exists. To derive this relationship we have manipulated the generalised Stefan-Maxwell equation to get a more conv enient generalised multicomponent Fick's law in which clearly defined diffu sivities and coupling coefficients appear: the two equations are wholly equ ivalent. In the general accepted frame of hypotheses when using the solutio n-diffusion model we have written Fick's equation when coupling between the fluxes exists. The order of magnitude of coupling is calculated, using pre viously published experimental data, leading to the conclusion that couplin g, in selective pervaporation process, can be neglected. (C) 2001 Elsevier Science B.V. All rights reserved.