Adsorption of Ar and SO2 on graphitized carbon black: The importance of functional groups

Grand Canonical Monte Carlo (GCMC) simulation was used to determine the isotherms and isosteric heats of argon and the strongly polar molecule, sulphur dioxide (SO 2 ), adsorbed at 78 and 273 K on a graphitized thermal carbon black (GTCB) surface with functional groups. The functional group, was modelled as oxygen atoms bonded to a C-atom in the graphene surface, since these have been shown to be retained after thermal treatment of GTCB. The simulated adsorption isotherms and isosteric heats of argon and SO 2 were compared with the experimental data. It is shown that, while functional groups do not affect the adsorption of argon, adsorption of SO 2 is very sensitive to their concentration, especially at low loadings, where the adsorption is dominated by the electrostatic interaction between SO 2 and the functional group. This is confirmed by analysis of the various contributions to the isosteric heat: (1) fluid-functional group interactions, (2) fluid-basal plane interactions, and (3) fluid–fluid interactions. Finally, we investigated the orientation of SO 2 in the first and second layers depends on loading as well as on the distance of the molecule from the surface.