Kinetics of self-diffusion of water molecules in natrolite

Abstract

Solid-state ¹H NMR is applied to investigate the kinetics of diffusion of H₂O molecules in the fibrous zeolite natrolite [Na₂Al₂Si₃O₁₀]∙2H₂O. It is found that the stepwise heating of the zeolite in air leads to the following pattern of molecular diffusion jumps: at first they increase in number and then decrease exponentially with time. Conducting such an experiment in an aqueous medium leads to the opposite effect. The results obtained confirm our previous suggestion about the importance of interstitial defects, or overhydrated local states, in molecular diffusion.