Inorganic membrane selectivity to ions in relation with streaming potential

The streaming potential, permeate flux and ion transmission are measured on an inorganic ultra filtration membrane (ZrO2). The streaming potential depends on charge distribution, which is modified by changing the pH, the ionic strength, and the nature of ions. This study points out the effect of membrane net charge on ion transmission for monovalent and divalent salt filtration (NaCl and CaCl2), even in the case of large pore radius (2 nm, MWCO=10 000 g/mol) compared to the ionic radius in the case of the tangential filtration. The filtration of a mixture of both the salts put into the fore that sodium ion transmission is slowed down when calcium is present in solution because of the relative ion mobility. (C) 1999 Elsevier Science B.V. All rights reserved.