Ion-Exchange Membrane Characterization

Characterization of ion-exchange membranes is closely related to their preparation. The most interesting properties of ion-exchange membranes are (Spiegler 1958):

• Τhe electrical resistance in different electrolyte solutions

• The type and density of fixed charges and their distribution in the membrane matrix

• The permselectivity of the membrane for different ions

• Τhe transport rate of neutral components, especially water

• The mechanical and chemical stability and the swelling in different electrolyte solutions

A series of procedures and techniques are applied to determine the different membrane properties. Microscopic examination yields information on heterogeneity of the membrane structure and in case of reinforced membranes the type of reinforcement used. The electrical charge of an ion-exchange membrane can be determined qualitatively by using indicator solutions. A drop of a 0.05 % solution of methylene blue and methyl orange on a membrane sample stains a yellow spot on top of an...