NAMS 2002 Workshop - ICOM 2008

Composite Polymeric Membrane Formation – 5
Monday July 14, 4:30 PM-5:00 PM, Waialua
Experimental Verification of Effect of Support on Membrane Performance
R. Takagi (Speaker), Shukugawa Gakuin College, Nishinomiya, Japan, takagi@shukugawac.ac.jp
A. Pihlajamäki, Lappeenranta University of Technology, Lappeenranta, Finland
T. Shintani, Nitto Denko Corporation, Osaka, Japan
M. Nyström, Lappeenranta University of Technology, Lappeenranta, Finland
Generally, a membrane is a composite, made by forming a skin layer on a
support. The ion permeability coefficient of the support is generally different from
that of the skin layer. Thus, the characteristic properties of the support also affect
membrane performance. The effect of the support on the membrane
performance has been theoretically studied. It is already reported that the
variation of membrane charge, pore radius, porosity and thickness of the support
affect the ion flux and, then, affect the rejection of the membrane. It is very
important to know the effect of the support on the membrane performance to
design a new membrane. Unfortunately, it is very difficult to verify the effect of
the support experimentally. It will be possible to verify the effect of the support
experimentally, if the characteristic properties of the skin layer and the support
are known separately. It is possible to characterize the support as a separate
membrane experimentally. However, it is very difficult to experimentally
characterize the skin layer as a separate membrane, since the skin layer is very
thin and it is almost impossible to obtain the skin layer as a separate membrane.
In this paper, a potential way to experimentally verify the effect of the support is
discussed. The composite membrane will be asymmetric with respect to
membrane charge, since the porosity and the pore radius of the support are
different from those of the skin layer. It is theoretically reported that the
membrane potential of the asymmetric membrane with respect to membrane
charge varies by changing the membrane setting from (bulk solution 1|skin layer |
support | bulk solution 2) to (bulk solution 1| support | skin layer | bulk solution 2).
The membrane potential is an electric potential difference generated between the
bulk solutions when the membrane separates two bulk solutions with different
concentration of electrolyte or different kind of electrolyte. Then, if the skin layer
and the support are homogeneously charged and the membrane potential of the
composite membrane varies by changing the membrane setting, it shows that the
membrane is asymmetric with respect to membrane charge. It means that the
effect of the support is not negligibly small and that the support affects the
membrane performance.