Electrokinetic characterization of poly(vinyl butyral) hollow fiber membranes by streaming potential and electroviscous effect

Abstract

Streaming potentials and electroviscous effects were measured for two poly(vinyl butyral) (PVB) hollow fiber membrane modules with molecular weight cut off at 40 and 200kDa (M40 and M200) in KCl and CaCl2 electrolyte solutions. The results show that the PVB membrane has a weak negative charge due to the specific adsorption of ions, and the streaming potential of the membrane depends strongly on the salt concentration, type and valence of ions. The iso-electric points (IEP) of membranes M40 and M200 are both around 3.0 in KCl electrolyte solution and 3.5 in CaCl2 electrolyte solution. The electroviscous effect increases with the increase of electrolyte concentration at low electrolyte concentration, it reaches a maximum at a certain concentration and then decreases with the increase of electrolyte concentration. The electroviscous effect is little greater for M40 than for the M200, and the electroviscous effect of KCl solution is greater than that of CaCl2 solution under the same concentration. The zeta potentials for M200 have been calculated by streaming potential and the electroviscous effect. The values of zeta potentials calculated from streaming potential are less negative than those from electroviscosity measurements.