Diffusion in heteroionic zeolites: part 2. Diffusion of water in heteroionic stilbites

Heteroionic forms of a purified natural stilbite from Skye, UK, have been prepared. After characterisation by X-ray diffraction and thermal methods they have been examined as substrates for tritiated water containment. The approach has been to determine water self-diffusion parameters for comparison with those of other candidate materials such as analcime, natrolite and synthetic zeolite A. The results show that water migration through the stilbite framework is facile, as expected, and in this respect stilbite does not compete with analcime (the zeolite previously shown to most restrict water mobility). The introduction of small amounts of Co, Ni, or Zn cations, however, does make up to 70% of the water immobile in the zeolite, even at 338 K. (C) 1998 Elsevier Science B.V. All rights reserved.