Electrokinetic measurements on porous polysulfone membranes

The surface properties of porous ultrafiltration membranes were determined by means of the streaming potential. The membranes were prepared from chemically modified polysulfone through a phase inversion process. The chemical reactions were carried out in such a way that the resulting polysulfone either was fitted out with chloromethyl substituents or with quaternary ammonia groups. Due to this, the surface of the membranes cast from these materials were either neutral or positively charged. In aqueous solution, ion adsorption as well as dissociation can occur at the surface of the membranes. This can be demonstrated by streaming potential measurements at different pH values, but constant ionic strength. From the calculated zeta potential using a recently developed model, evidence can be given on the dissociation constants of acidic and basic functional groups on the surface of the membranes and on the amount of charges within the shear plane adjacent to the membrane. Using solutions which contained surfactants, qualitative information on the amount of charges within the capillaries of the membrane can be obtained. In the range from 20 to 70°C no temperature dependency of the zeta potential could be observed.