Experimental and modeling investigation on surface tension and surface properties of (CH4 + H2O), (C2H6 + H2O), (CO2 + H2O) and (C3H8 + H2O) from 284.15 K to 312.15 K and pressures up to 60 bar

• Using pendant drop method for surface tension measurements.
• Applying the gradient theory in combination with CK-SAFT EOS.
• Applying the proposed influence parameter for the gradient theory.

In this work, the experimental surface tensions for (CH4 + H2O), (C2H6 + H2O), (CO2 + H2O) and (C3H8 + H2O) binary systems have been measured with the pendant drop tensiometer at temperatures ranged (284.15–312.15) K and pressures ranged (1–60) bar. Subsequently, the combination of gradient theory (GT) and Chen–Kreglewski Statistical Association Fluid Theory equation of state (CK-SAFT EOS) is applied for modeling these experimental surface tensions and determining the density profiles of interface. Also, a proposed influence parameter as a function of the densities of the bulk phases is applied for these systems. The binary interaction parameters for these systems are determined according to the bulk densities and surface tensions. Subsequently, the density profiles for the surface layer are determined. The surface tensions determined with the gradient theory (GT) agree well with experimental surface tensions for these systems (overall AAD ∼ 1.36 and 1.37 for constant and the proposed influence parameters, respectively).