Electrokinetic characterization of the Al 2O 3 ceramic MF membrane by streaming potential measurements

Abstract

The alumina microfiltration(MF) membrane was modified with nanocrystalline TiO 2 in the pore wall. The electrokinetic properties of unmodified and modified alumina membranes were characterized by streaming potential measurements during tangential filtration at various conditions of pH, ionic concentration and ionic species in solutions. The modified membrane reveals a more acidic characteristic. The influence of pH value on the streaming potential of both membranes is explained by the shifting of the proton equilibrium that occurs at the surface of the membrane. The modification of the alumina membrane with TiO 2 leads to the decrease of its isoelectric point (IEP) from 6.1 to 4.0 when filtered with NaCl solution. The ionic concentration and electrolyte species also have influence on the streaming potential of both membranes. The reversal of the streaming potential sign and the change of the isoelectric point of the membrane when filtered with CaCl 2 and Na 2SO 4 solutions show specific adsorption of Ca 2+ and SO 4 2- ions onto the surface.