The composition of an ionic aqueous solution can modify the wettability behavior of a liquid/liquid/solid system. This behavior is of great importance for oil extraction and some separation processes. Here we model the contact angle and wettability on the basis of a tridimensional classical density functional theory (DFT) and Young equation for a brine/oil/solid surface system. We propose the inclusion of dispersion interaction between surface-ion and oil-ion. The equilibrium contact angle is found through the minimization of the grand potential. The approach presented here is promising and due to its versatility can be expanded to systems with some peculiarities such as roughness and thin film. (C) 2018 Elsevier B.V. All rights reserved.