Enhancement of Membrane Separation Performance
The zeta potential is sensitive to small changes in the surface chemistry and thus suitable for monitoring membrane performance.
Surface modification of polymer membranes is required to adjust the properties of a base membrane polymer for various filtration applications (drinking and waste water treatment, seawater desalination, liquid/liquid separation).
The performance of a poly(acrylonitrile), PAN, ultrafiltration membrane for alcohol-water evaporation separation is enhanced by the deposition of polyelectrolyte layers.
It was recently demonstrated (see below) that the deposition of a single layer of poly(ethylene imine), PEI, on the PAN membrane dramatically improves the separation of ethanol-water mixtures. The zeta potential of the PEI-modified membrane and the shift of the isoelectric point (IEP) to pH 8.4 confirms the presence of this cationic polyelectrolyte on the membrane surface.
The deposited polyelectrolyte layer is subject to wear during the crossflow filtration process. The zeta potential is sensitive to a decay in the PEI surface concentration and thus additionally suitable for monitoring the membrane performance.
G. Zhang, X. Gao, S. Ji, Z. Liu, J. Membrane Sci., 307 (2008) 151-155