Monitoring of Membrane Fouling with Zeta Potential
Zeta potential measurements elucidate the fouling behavior of membranes and contribute to the optimization of membrane performance.
Employment of polymer membranes for purification and separation processes experiences a steadily growing popularity. Besides their classical application in water purification, polymer membranes become increasingly attractive for the separation and upconcentration of products in the fields of food, biotechnology and pharmacy. Despite of these versatile application areas, there are restrictions for the optimum use of polymer membranes. The deposition of dissolved or dispersed matter from the feed on the membrane surface, known as membrane fouling, represents an often unresolved challenge especially for polymer membranes and pressuredriven filtration processes (such as nanofiltration and reverse osmosis). The conventional method for determining membrane fouling is monitoring transmembrane pressure (TMP) and flux is only sensitive, and thus applicable, at progressive fouling and does provide information about the characteristics of the deposited layer. Analytical methods for the characterization of the membrane surface and fouling layer, as well as of the efficiency of the related cleaning processes complement the measurement of TMP and flux. Among these methods, determination of the zeta potential at the interface between the membrane surface and the surrounding aqueous solution has been established in the past decades.
The zeta potential represents the electric charge density at the membrane-water interface and accounts for the electrostatic interaction between the membrane (solid surface) and dissolved compounds in water. This interaction is frequently the dominating force for the attraction or repulsion of ions, macromolecules, and suspended particles and, therefore, decisive for membrane fouling.
1. Elimelech, Menachem, Chen, William H. and Waypa, John J. Measuring the zeta (electrokinetic) potential of reverse osmosis membranes by a streaming potential analyzer. Desalination. 1994, Vol. 95, 3, pp. 269-286.
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