The membrane potentials have been measured for the dense and the asymmetric membranes of cellulose acetate and of aromatic polyamide. The dependence of ionic mobility in the asymmetric membrane of aromatic polyamide on the ionic radius is significantly different from that in the dense membrane. Moreover it is very noteworthy that the asymmetric membrane behaves as if it is negatively charged while the dense membrane behaves as if it is uncharged.
Cellulose acetate itself is slightly negatively charged membrane material and this is confirmed in the both cases of the dense, and the asymmetric membranes. The dependence of the ionic mobility in both membranes on the ionic radius is rather similar to each other. However, a little difference was observed between them.
It is concluded that the ionic behavior in the membranes depends not only on the membrane materials, but also on the physical structure of the membranes.
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