Demonstration of contact induced ion exchange in zeolites

In this paper, it is demonstrated that exchange of the cationic species Na/sup +/, Li/sup +/, K/sup +/, and Ca/sup 2 +/, can occur between different zeolite crystals based only on a simple physical contact between the crystallites. The structural changes accompanying the exchange have been monitored by powder XRD and /sup 29/Si MAS NMR/sup 3/ studies which, because they are sensitive to long- and short-range ordering effects, respectively, complement each other and give a complete description of the structures. Zeolite A has been chosen for this work as it has a well-defined structure and XRD pattern and gives a single sharp absorption in its /sup 29/Si MAS NMR spectrum. 4 references, 1 figure.