On the diffusion of hard sphere fluids in disordered porous media: New extended Enskog theory description

TL;DR

This paper develops an extended Enskog theory to accurately predict the self-diffusion of hard-sphere fluids in disordered porous media, incorporating free volume effects to match simulation results.

Contribution

It introduces a novel approach using free volume-dependent functions within Enskog theory, improving predictions for diffusion in porous media.

Findings

The new theory aligns well with computer simulations.

Inclusion of free volume fractions enhances accuracy.

The approach outperforms previous models.

Abstract

We proposed a new extended version of Enskog theory for the description of the self-diffusion coefficient of a colloidal hard-sphere fluid adsorbed in a matrix of disordered hard-sphere obstacles. In a considered approach instead of contact values of the fluid-fluid and fluid-matrix pair distribution functions, we introduced by input the new functions that include the dependence on the fraction of the volume free from matrix particles and from fluid particles trapped by matrix particles. It is shown that the introduction of this free volume fraction by the Fermi-like distribution leads to the best agreement between theoretical predictions and computer simulation results [Chang R., Jagannathan K., Yethiraj A., Phys. Rev. E, 2004, 69, 051101].