Investigation of surface tensions for pure associating fluids by perturbed-chain statistical associating fluid theory combined with density-gradient theory

The perturbed-chain statistical associating fluid theory (PC-SAFT) and density- gradient theory (DGT) are used to construct a nonuniform equation of state for associating fluids. In the bulk phases, the nonuniform equation of state reduces to PC-SAFT that yields accurate bulk properties. In the vapor-liquid surface, this nonuniform equation of state is able to satisfactorily correlate the surface tensions for pure associating fluids by adjusting the influence parameters. The surface tensions of 13 pure associating fluids are correlated, and the results agree well with the experimental data.