Ultrapure Water Process Ion Exchange Membrane Classification Two

Based on the distribution of active groups in the base membrane, ion exchange membranes can be further classified into heterogeneous membranes, homogeneous membranes, and semi-homogeneous membranes.

1. Heterogeneous Membranes: These are thin films made by mixing fine powder of ion exchangers with binders. They contain both ion-exchange active groups and a binder portion forming the film structure, resulting in a discontinuous chemical structure, hence the name heterogeneous or non-homogeneous membrane. These are easy to manufacture and inexpensive, but generally have poor selectivity and high membrane resistivity.

2. Homogeneous Membranes: These are membranes made directly from polymeric materials with ion-exchange groups, or by directly attaching active groups to a polymeric membrane base. In these membranes, the ion-exchange active groups are chemically bonded to the film-forming polymeric material, resulting in a completely uniform composition, hence the name homogeneous membrane. These membranes possess excellent electrochemical and physical properties and represent the main development direction of ion exchange membranes in recent years.

3. Semi-homogeneous Membranes: In these membranes, the polymeric material and ion-exchange active groups are uniformly combined, but they are not chemically bonded together. For example, a semi-homogeneous membrane is made by dissolving an ion exchange resin and a film-forming polymer binder in the same solvent and then casting it. Its appearance, structure, and performance are intermediate between those of heterogeneous and homogeneous membranes.