Electrokinetic leakage as a tool to probe internal fouling in MF and UF membranes

Abstract

Tangential electrokinetic measurements are widely used to characterize membrane fouling as the membrane zeta potential is partly governed by the presence of foulant materials on its surface. However, in the case of porous materials as micro-(MF) and ultrafiltration (UF) membranes, a part of the streaming current flows through the porosity of the membrane during measurements. This under various transmembrane pressures (TMP). A significant impact of the TMP on the internal fouling of a MF PES membrane was highlighted, whereas almost no impact of the TMP was noticed in the case of an UF PAN membrane. The developed methodology using the quantification of the electrokinetic leakage phenomenon allows distinguishing the contributions of internal and external (surface) fouling. These findings offer new application of tangential electrokinetic measurements to gain more insight into the characterization of membrane fouling.

Advanced electrokinetic characterization of layer-by-layer assembled polyelectrolyte membranes: Consideration and use of the electrokinetic leakage phenomenon

“…underneath the membrane surface (Figure 1). This parasitic phenomenon has been called electrokinetic leakage [2]. Describing the sample/channel/sample system as a parallel electrical circuit, Yaroshchuk and Luxbacher [27] derived the following equation as an alternative to the classical Smoluchowski equation (which implicitly assumes that the experimentally measured streaming current (Is) does not flow elsewhere than in the channel formed by the two samples of membranes):…”

“…Zeta potential is a widely-used indicator providing insight on materials surface charge [1]. Its determination is valuable for membrane separations, to understand fouling [2][3][4][5][6][7][8][9], ageing [10][11][12][13] and rejection mechanisms [14,15]. It is therefore crucial to use characterisation techniques and develop optimised experimental protocols to determine the zeta potential of membranes reliably and accurately.…”

“…However, it has been shown that a part of the streaming current generated by the hydrostatic pressure gradient is likely to flow through the porous layer(s) underneath the membrane surface [27]. This parasitic phenomenon can be taken into account by adding a contribution to the classical Smoluchowski equation as first proposed by Yaroshchuk and Luxbacher (2010) [27] and subsequently applied in a few studies [2,30,31].…”