1982 by CRC Press, Inc. It is now more than twenty years since reports of ion exchange behavior of zirconium phosphate gels first appeared in the chemical literature. 1, 3 Since that time, research into the nature of this and similar compounds has continued unabated. Part of the impetus for this effort resulted from the discovery that zirconium and titanium phosphates could be prepared in crystalline form. 4, 5 In the interim many other layered group (IV) phosphates and arsenates have been crystallized and studied as well as dozens of exchanged forms. 6, 7, 8 In addition, there are now quite a number of known phases of zirconium phosphate. 9 Furthermore, the original one, zirconium bis(monohydrogen orthophosphate), can be obtained as a gel, as single crystals, and in all intermediate stages of crystallinity. 10 For all of these products the ion exchange 3behavior differs, being a function of the crystallinity and structure. Thus, it is a mistake to consider zirconium phosphates as a single compound. It is essential to an understanding of the observed behavior that the exchanger be properly characterized. We shall attempt to do this as far as possible so that some reasonable correlation between structure and behavior may emerge.
