Structural changes in the natural zeolite gismondine (GIS) induced by cation exchange with Ag, Cs, Ba, Li, Na, K and Rb

Crystals of gismondine, Ca (sub 4) Al (sub 8) Si (sub 8) O (sub 32<P6M><P255>16H) (sub 2) O, were fully ion-exchanged and their crystal structures determined. The Ag- and Cs, Na-gismondines preserved the space group symmetry P2 (sub 1) /c of the original natural crystals; that of Ba-gismondine was reduced to P2 (sub 1) , those of Li-, Na- and Rb-gismondine to I2/a, and that of K-gismondine to I2. Except for Na-gismondine no single crystals were obtained, and all refinements were carried out on powder XRD data using the Rietveld method. Non-framework cations and H (sub 2) O molecules were localized in the pores of the frameworks. The aluminosilicate coordination tetrahedra are tilted and the framework is distorted in response to the exchanged cations. Thus a remarkable shrinkage of 13.3 % for b was observed for Li-gismondine in comparison to the original gismondine; for Ag-gismondine, the cell volume shrank 7.5 % in comparison with gismondine.