The final configurations of the bulk electrolyte solutions (from Sect. II A) are placed between two graphene monolayers, which form the feed reservoir. One of these layers functions as a membrane, while the other acts as a piston; see Fig. ). These layers also function as electrodes, with an external potential difference applied between them. The positive electrode is on the left side of the feed reservoir, and the negative electrode is on the right. The rigid graphene layers are oriented parallel to the xy plane, with the layer at z = -0.3 nm acting as a piston and the one at z = 8.3 nm acting as the nanoporous graphene membrane. Note that an initial 0.3 nm gap between the solution and the solid surface, corresponding to the first hydration layer on carbon materials , facilitates the equilibration process.