The interdiffusion of metal ion-hydrogen ion couples in Nation membrane systems has been measured by a rotating diffusion cell (RDC) technique. At low metal concentrations, the transport rate is controlled by boundary layer diffusion and the metal flux follows the order Li+ < Na+ < K+ < Rb+ < Cs+ for alkali metals, and Ca2+ < Sr2+< Ba2+ for alkaline earth metals. At high metal concentrations, the transport process is controlled by membrane diffusion and the order of the flux is Li+ <Cs+ <Rb+ <Na+ <K+ for alkali metals, Ca2+<Ba2+<Sr2+ for alkali earth metals, and Y+ <Ca2+ < Na+ for ions of similar ionic size (0.93-0.99 Å) but different charge. The results are interpreted in terms of ionic hydration coupled with charge and size effects.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physical and Theoretical Chemistry
- Filtration and Separation