Abstract: The electrokinetic properties of Al2O3 microfiltration membranes (MF) were characterized by streaming potential measurements during tangential filtration of solutions with various conditions of pH, electrolyte species and concentration. Results show that the streaming potentials are dependent on the pH of filtered solutions, types of the electrolyte and ionic concentration. The IEP of the membrane is about 6.1 when filtered with 10-3 mol/L NaCl solution, and shifts toward a higher pH of 6.8 and a lower pH of 5.6 for the solutions of CaCl2 and Na2SO4 with the same ionic concentration, respectively, because of specific adsorption of Ca2+ and SO42-. The specifically adsorbed ions (Ca2+ and SO42-) can change the IEP and net charge sign of the membranes as their concentration increases, whereas electrolytes NaCl can only asymptotically reduce it to zero.

Key words: The electrokinetic properties of Al2O3 microfiltration membranes (MF) were characterized by streaming potential measurements during tangential filtration of solutions with various conditions of pH, electrolyte species and concentration. Results show that the streaming potentials are dependent on the pH of filtered solutions, types of the electrolyte and ionic concentration. The IEP of the membrane is about 6.1 when filtered with 10-3 mol/L NaCl solution, and shifts toward a higher pH of 6.8 and a lower pH of 5.6 for the solutions of CaCl2 and Na2SO4 with the same ionic concentration, respectively, because of specific adsorption of Ca2+ and SO42-. The specifically adsorbed ions (Ca2+ and SO42-) can change the IEP and net charge sign of the membranes as their concentration increases, whereas electrolytes NaCl can only asymptotically reduce it to zero.