Random Surface Statistical Associating Fluid Theory: Adsorption of n-Alkanes on Rough Surface

TL;DR

This paper introduces RS-SAFT, a novel theoretical approach combining SAFT and DFT to accurately predict the adsorption of chain hydrocarbons on rough, heterogeneous surfaces, validated by experiments with hexane on carbon black.

Contribution

The paper develops RS-SAFT, a new SAFT-DFT based model capable of describing adsorption on natural rough surfaces with heterogeneity, extending previous theories.

Findings

RS-SAFT accurately predicts hexane adsorption on carbon black.

The model accounts for surface roughness and heterogeneity.

Predictions align well with experimental data at different temperatures.

Abstract

Adsorption properties of chain fluids are of interest from both fundamental and industrial points of view. Density Functional Theory (DFT) based models are among the most appropriate techniques allowing to describe surface phenomena. At the same time Statistical Associating Fluid Theory (SAFT) successfully describes bulk PVT properties of chain-fluids. In this publication we have developed novel version of SAFT-DFT approach entitled RS-SAFT which is capable to describe adsorption of short hydrocarbons on geometrically rough surface. Major advantage of our theory is application to adsorption on natural roughs surfaces with normal and lateral heterogeneity. For this reason we have proposed workflow where surface of real solid sample is analyzed using theoretical approach developed in our previous work [1] and experimentally by means of low temperature adsorption isotherm measurements for simple fluids. As result RS-SAFT can predict adsorption properties of chain fluids taking into account geometry of the surface sample under the consideration. In order to test our workflow we have investigated hexane adsorption on carbon black with initially unknown geometry. Theoretical predictions for hexane adsorption at 303K and 293K fit corresponding experimental data well.