Liquid–liquid interfacial tensions of binary water-hydrocarbons mixtures via gradient theory and CPA equation of state

•We combined Gradient Theory of fluid interfaces with CPA equation of state.•We correlated liquid–liquid interfacial tensions with only one constant parameter.•We made predictions of the pressure effects over interfacial tensions.•The deviation from measure data was 0.14mN/m (average) at 0.1MPa.•The model generally over-predicts interfacial tensions at high pressures.