Electrokinetic characterisation of cleaned non-circular multi-channelled membranes

The possibility of using the electroviscous effect to measure the zeta potential of previously fouled non-circular multi-channelled membranes is assessed. Measurements of the streaming potential and permeate flow reduction arising from the electroviscous effect were carried out at various electrolyte (KCl) concentrations and pH. Under similar conditions both techniques identify the isoelectric point although the magnitude of the zeta potentials found from the electroviscous measurements is greater than those found from streaming potential measurements even when surface conductivity has been taken into consideration through the inclusion of correction factors. Differences between the two methods increase when comparison is made between virgin and used membranes. These differences are attributed to inadequacies in the electrokinetic flow theory used to convert electroviscous ratios to zeta potentials. Furthermore, the non-circular multi-channel geometry may introduce some discrepancies in calculations using electroviscous theory. The results suggest that the electroviscous technique is suitable for the determination of the isoelectric point but not the complete characterisation of used membranes.