DETERMINING THE ZETA-POTENTIAL OF CERAMIC MICROFILTRATION MEMBRANES USING THE ELECTROVISCOUS EFFECT

The possibility of measuring the zeta-potentials of porous membranes u sing the electroviscous effect was investigated. The zeta-potential of Membralox(R) ceramic microfiltration membranes was determined both wi th the newly developed electroviscous technique and by streaming poten tial measurements. It was found that the electroviscous technique prov ided a simple means of obtaining accurate values of zeta-potential, es pecially for higher zeta-potentials. The streaming potential measureme nts were found to be more suitable for the determination of the iso-el ectric point, i.e. the pH at which the zeta-potential is zero. The iso -electric points of new alpha-alumina, zirconia, and titania membranes were found to be 8.5, 8.0, and 6.3, respectively. Upon using the memb ranes and cleaning them with a detergent, the iso-electric point of th e alpha-alumina membrane decreased to 6.5, and that of the zirconia me mbrane decreased to 5.2, while the iso-electric point of the titania m embrane stayed virtually constant. Cleaning these membranes with a str ong acid or base could not reverse the observed decreases in iso-elect ric point. (C) 1998 Elsevier Science B.V. All rights reserved.