The Structures and Functions of Ion-Exchange Membranes

The mobile cations are referred to as counterions and the mobile anions that carry the same electrical charge as the polymer membrane that are more or less completely excluded from the membrane are referred to as co ions. Due to the exclusion of the co ions, a cation-exchange membrane is more or less impermeable to anions. Anion-exchange membranes carry positive fixed charges and exclude cations. Thus, they are more or less impermeable to cations. To what extent the co ions are excluded from an ion-exchange membrane depends on membranes as well as on solution properties. Bipolar membranes enhance the dissociation of water molecules into H + and OH ions and are used in combination with monopolar membranes for the production of acids and bases from the corresponding salts [5], 

The most desired properties of ion-exchange membranes are high permselectivity, low electrical resistance, good mechanical and form stability, and high chemical and thermal stability. In addition to these properties bipolar membranes should have high catalytic water dissociation rates. 

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