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Abstract
A new method for determining the ζ-potential of a membrane or other porous media is proposed in which an alternating electric field is applied in the measurement of the electroosmotic flux. Determination of the apparent ζ-potential of commercial microfiltration membranes was conducted under different alternating frequencies. An increase in the magnitude of ζ-potential is obtained as a result of increased alternating frequency. A dramatic change of the apparent ζ-potential was observed when the membrane was soaked for 24 hours in a solution containing bovine serum albumin (BSA). The magnitude of the ζ-potential approached zero at pH 4.9, which indicated the adsorption of BSA on the membrane surface. When the membrane sample was soaked for 24 hours in a BSA solution containing PEG 4000, a substantial increase in the magnitude of the ζ-potential compared to that in the BSA solution was obtained. In some cases the apparent ζ-potential obtained in the BSA-PEG 4000 solution was up to that obtained in the BSA-free solution. This demonstrated the shielding function of PEG 4000 as described elsewhere. The ζ-potential was shown to be a sensitive indicator of membrane fouling caused by protein adsorption.
ACKNOWLEDGEMENT
Support from the National Natural Science Foundation of China under Grant 29676022 is gratefully acknowledged.