Polyimide-based membranes for desalination

A method of making a polyimide membrane, comprising:

• mixing at least one dianhydride monomer and at least one phenylenediamine monomer in a first solvent to form a mixture;
• wherein a molar ratio of the dianhydride monomer and the phenylenediamine monomer present in the mixture is in a range of 1:5 to 5:1;
• heating the mixture thereby polymerizing the dianhydride and phenylenediamine monomers to form a polyimide polymer in a crude mixture;
• precipitating the polyimide polymer from the crude mixture to separate the polyimide polymer from the crude mixture;
• mixing and dissolving the polyimide polymer in a second solvent to form a polyimide solution;
• applying the polyimide solution onto a surface of a substrate to form a polyimide liquid layer on the substrate;
• immersing the substrate after the applying in at least one liquid medium selected from the group consisting of water and an alcohol, thereby precipitating the polyimide polymer from the polyimide solution to form the polyimide membrane disposed on the surface of the substrate;
• and
• removing the polyimide membrane from the surface of the substrate;
• wherein the polyimide membrane has a thickness in a range of 30 to 100 micrometers (μm).