Preparation and characterization of heterogeneous weak base anion-exchange membranes

The preparation of new heterogeneous anion-exchange membranes containing particles of a weak basic ion-exchange resin in a polypropylene matrix is described. For comparison, a heterogeneous membrane consisting of a strong basic functional group was also prepared. The anion-exchange membranes were prepared in a laboratory discontinuous homogenizer and extruder followed by compression of extruded membranes to ensure the homogeneity of the test sample. Parameters important for a subsequent transfer of production from laboratory to an industrial scale, torque and head pressure, were observed. Electrochemical and mechanical properties of resulting membranes, in particular their ion-exchange capacity, areal and specific resistances, permselectivies, swelling in water, 1moldm(-3) NaOH, and 1moldm(-3) HCl solution, were determined. Weak basic ion-exchange resin Purolite A830 behaved similarly as the strong basic ion-exchange resin during processing, and the resulting membrane showed similar electrochemical and physical properties. The heterogeneous anion-exchange membranes with other weak basic anion-exchange resins showed unsuitable swelling, which was reflected in electrochemical properties of these ion-exchange membranes.