Modeling the surface tension and surface properties of (CO2Â +Â H2O) and (H2SÂ +Â H2O) with gradient theory in combination with sPC-SAFT EOS and a new proposed influence parameter

The surface tensions of pure fluids (carbon dioxide, hydrogen sulfide and water) and binary systems containing (CO2 + H2O) and (H2S + H2O) are modeled by using a reliable theory. The gradient theory (GT) is combined with the simplified Perturbed-Chain Statistical Association Fluid Theory equation of state (sPC-SAFT EOS) to describe the densities and surface tensions of (CO2 + H2O) and (H2S + H2O) systems at temperature range (298.15-398.15 K) and pressure range (0.1-60 MPa). A new influence parameter in terms of bulk phase's densities is also proposed. First, the influence parameters of pure components are determined. Then, the binary interaction parameters of (CO2 + H2O) and (H2S + H2O) systems are fitted according to the bulk densities and surface tensions. Subsequently, the density profiles of the interface are determined. The surface tensions reproduced by the present model are in a good agreement with experimental data (overall AAD ~5.83 and 7.50 for constant and new proposed influence parameters, respectively).