Using the heterogeneous isotope exchange technique, a study was made of the diffusion of 22Na in type-A synthetic zeolite at 21C. The exchange rate did not fit the classical function for the time-independence of an ideal diffusion process. For the initial exchange, the diffusivity at 21C was about 3 x 10-7cm2/s. Over the range of 0 to 30C, the diffusivity was described by:

D(cm2/s) = 1 x 10-3exp[-0.39(eV)/kT]

Isotope Exchange Studies on Silicate Ion Exchangers. Interpretation of Non-Uniform Self-Diffusion of Alkali Metal Ions in Synthetic Zeolite. H.Gaus, H.Hoinkis: Zeitschrift für Naturforschung A, 1969, 24[10], 1511-7