Physical and chemical synergistic strategy: A facile approach to fabricate monovalent ion permselective membranes

Abstract Separation of monovalent ions is essential for chemical engineering industries, such as metallurgy, bio-refining, and waste recovery. As a critical consideration of separation, constructing functional layer on the membrane surface to fabricate “special grade” ion exchange membrane (monovalent permselective membrane, MVS) is an effective strategy for monovalent ions sieving via electrostatic repulsion mechanism. Here in this study, we proposed an electrical deposition (physical-assembly) and in-situ chemical reaction (nucleophilic substitution) synergized approach to fabricate MVS. By using commercial AMX membrane as the substrate, polydopamine assisted co-deposition of chitosan was pre-performed on pristine membrane, and then the reactive blue 4 was selected and electrically deposited. The synergistic approach strengthened the ion sieving through counter-charged layer, while the chemical reaction provide long-term stability. The resultant membrane displayed Cl− permselectivity up to 11.85 without significant sacrificing of ion-flux. And this membrane can keep appropriate stability after operating the electrodialysis process for ten cycles.