Studies on Artificial Selective Dialysis Membrane for Alkali Metal Ion

Abstract

The preparation of an artificial ion selective membrane was attempted from the viewpoidt that an ion having small hydration number can move freely in the hydrophobic region inside the membrane compared with an ion having large amount of hydration. If we could make a tunnel with a hydrophobic wall across the membrane, which becomes a path for ions, K⁺ ion, less hydrated ion than Na⁺ ion, would pass through the tunnel more easily than Na⁺ ion, since the icebergs (hydrophobic hydration) formed on the wall do not interact with the thin hydration layer of K⁺ ion as do with the thick hydration shell of Na+ ion. On the basis of this interpretation, we prepared a membrane from the mixing solution of a derivative of polyamine sulfone and polyvinylalcohol by drying on a plate.
By the result on ion dialysis experiment, the ratio of diffusion constant across the membrane, DK⁺/DNa⁺, becomes 1.7 at maximum. The value is not so large, but the result supports that our guiding principle is valid for preparing an ion selective dialysis membrane.