Prediction of <i>n</i>-Alkane Adsorption on Activated Carbon Using the SAFT–FMT–DFT Approach

The SAFT–FMT–DFT approach to adsorption equilibrium combines elements of the statistical associating fluid theory (SAFT), fundamental measure theory (FMT), and classical density functional theory (DFT) to create a framework to model fluids described as chain molecules in the presence of external fields. In this paper, the SAFT–FMT–DFT approach is used to calculate single pore isotherms to develop a pore size distribution for BPL activated carbon, described by the 10–4–3 fluid-wall potential, based on nitrogen adsorption at 77 K. The nitrogen pore isotherms show a progression of monolayer transitions, pore filling, and pore condensation. The pore size distribution is used to predict excess adsorption isotherms for methane, ethane, n-butane, n-pentane, and n-hexane adsorbed on the carbon at 298.15 and 348.15 K. Parameters for interaction of the molecules with the solid are obtained using experimental data for adsorption of each alkane on the planar wall of a nonporous graphitized carbon. The predicted excess n-alkane isotherms agree well with experimental isotherms.