NAMS 2002 Workshop - ICOM 2008

Membrane and Surface Modification III – 6
Friday July 18, 12:15 PM-12:45 PM, Honolulu/Kahuku
Surface Modification of an Aromatic Polyamide Membrane By Self-
Assembly of Polyethyleneimine on the Membrane Surface
Y. Zhou (Speaker), University of Waterloo, Waterloo, Canada
S. Yu, Zhejiang Sci-Tech University, China
C. Gao, The Development Center of Water Treatment Technology, China
X. Feng, University of Waterloo, Waterloo, Canada - xfeng@uwaterloo.ca
Reverse osmosis is now a well accepted technique for water and waste water
treatment, and interfacially polymerized thin film composite (TFC) polyamide
membranes are being used extensively for these applications. Because
polyamide membranes are negatively charged under typical operating conditions
(pH > 4) due to carboxyl groups on the membrane surface, they are vulnerable to
fouling by cationic contaminants. In this study, an aromatic polyamide TFC
membrane was modified by electrostatic self-assembly of polyethyleneimine on
the membrane surface, and the modified membrane showed significantly
improved anti- fouling properties. It was expected that the charge reversal on the
membrane surface due to the application of the polyethyleneimine layer would
increase the fouling resistance of the membrane to cationic foulants because of
the enhanced electrostatic repulsion, and the increased surface hydrophilicity
would help minimize the flux reduction. The effects of parameters involved in the
membrane surface modification (e.g., polyethyleneimine concentration and
deposition time) on the membrane performance were investigated in terms of
water permeation flux and salt rejection with and without the presence of
decyltrimethylammonium bromide (which is a common cationic surfactant
present in waste water). It was shown that the improved fouling resistance and
the increased surface hydrophilicity compensated for the reduction in membrane
permeability due to the deposition of the polyethyleneimine layer.