Determination of Ion Exchange Capacity and Water Content

Ion exchange capacity is determined by measuring the amount of specified counter-ions in the membrane by titration after ion exchange with other ions or elution, using a suitable indicator. 

When the anion exchange membrane has weakly basic anion exchange groups, the membrane is equilibrated with acid solution, e.g., 1.0 N hydrochloric acid solution, for protonation and washed with methanol to remove non-ion-exchanged acid from the membrane. Then the membrane is equilibrated with a given amount of standardized sodium hydroxide solution and the remaining standardized sodium hydroxide is determined by titration. 

Water content changes with the concentration of electrolyte solution with which the membranes are equilibrated and with the species of counter-ions.2 The water content of an ion exchange membrane is expressed as the amount of water per gram of sodium or potassium ion-form cation exchange membrane or of chloride ion-form anion exchange membrane (g-H20/g ionic form wet or dry membrane). Whether or not the weight of reinforcing fabric has been subtracted must be specified. 

After measuring the ion exchange capacity and water content of the ion 

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