Computer Simulation of Benzene-Water Mixture Adsorption in Graphitic Slit Pores

The adsorption of mixtures of benzene water in graphitic slit pores has been studied using Monte Carlo simulation. It is shown that the adsorption of the mixture starts with the adsorption of benzene molecules on the graphite surface which then act as anchors for water molecules to adsorb. High loadings of water in a slit pore significantly affect the arrangement and orientation of benzene molecules. When the water density in the pore approaches its bulk liquid density, water molecules displace some benzene molecules from the surface, and the benzene sorption process switches from adsorption to an absorption mechanism. We have also studied the influence of the external vapor composition on the adsorption isotherms of benzene and water. It is observed that a high concentration of benzene in the vapor phase facilitates the adsorption of both benzene and water in such a manner that the condensation pressure of benzene and the onset pressure of water adsorption shift to lower values. At high pressures, the adsorption of water is dominant at the expense of benzene adsorption. This interesting finding calls for a review of the concept of graphite surface hydrophobicity when water is coadsorbed with hydrocarbons.