Ingress of water into zeolite 4A powder plugs.

One dimensional profiles of the concentration of water absorbed from vapour diffusing into compacted type 4A zeolite powder have been obtained by broadline NMR imaging. After an induction period of approximately 6 h, a region of full hydration advances linearly with time into the zeolite plug. This behaviour is typical of Case II diffusion. A simple numerical simulation gives good agreement with the experimental results