Study of the zeta potential and streaming current of ultrafiltration membranes in contact with an anionic surfactant

The controlled adsorption of surfactants on ultrafiltration (UF) membranes can modify their surface properties by increasing the fields of applicability. In this context, the understanding of the phenomena involved in the adsorption process of the surfactants is very important. The latter may be accomplished through measurements of the electrokinetic properties of the modified membranes under different conditions. Thus, this work is focused on the study of the streaming current and the zeta potential of polyethersulfone (PES) UF membranes modified with the anionic surfactant sodium dodecyl sulfate (SDS). The study was performed by measuring of the streaming current at the first contact between the membrane and the surfactant. The results obtained show that there are two zones of behavior, for the concentrations under and above the critical micelle concentration (CMC). In the first case a positive current was observed, meanwhile for the concentrations higher than the CMC the current observed was negative. Measurements of zeta potential of the modified membrane showed that the saturation of the membrane was reached at lower concentrations of SDS, and that the adsorption of the surfactant is taking place only on the membrane surface.