An ion-exchange membrane is a type of membrane that facilitates the passage of ions (charged particles) while blocking the passage of larger molecules. It is used in a wide range of applications, including water purification, desalination, and chemical synthesis. The membrane is often composed of a polymer containing ion-exchange groups that allow the selective passage of ions. Ion-exchange membranes are typically made of a cation-exchange resin and an anion-exchange resin, which allow for the exchange of ions between two solutions.