Electrokinetic phenomena of a polyethylene microfiltration membrane in single salt solutions of NaCl, KCl, MgCl2, Na2SO4, and MgSO4

The streaming potential measurements of a polyethylene microfiltration (PE–MF) membrane were carried out under aqueous solutions of five single salts (NaCl, KCl, MgCl2, Na2SO4, and MgSO4); the zeta potential and surface charge density of the membrane were estimated on the basis of the Helmholtz–Smoluchowski equation and the Gouy–Chapmann theory. The results show that the PE–MF membrane has a weak negative charge due to the specific sorption of ions, and behaves almost as a certain zeta potential in a very dilute salt solution and as almost a certain surface charge density in a solution with a concentration more than 4 mol·m−3. However, the streaming potential, the zeta potential and the surface charge density of the membrane depend strongly on the salt concentration and the type and valence of ions.