Polyfunctionality of α-Zr(HPO4)2·H2O. Case of H+/Ag+ and H+/Tl+ Ion Exchange Processes

A detailed investigation of the ion exchange processes of silver and thallium(I) ions on α-Zr(HPO4)2·H2O has been carried out. The H+/Ag+ exchange occurs in AgNO3 or CH3COOAg solution with a single phase transition and leads to Zr(AgPO4)2·H2O (interlayer distance 8.4 Å). The H+/Tl+ ion exchange process has been performed by titrating the exchanger with 0.1 M (TlNO3+TlOH) solution, owing to the great ionic size of Tl(I). The titration curve shows essentially a single plateau. In a similar way to that for H+/Ag+ exchange, the process takes place with a single phase transition, leading to Zr(TlPO4)2·H2O (interlayer distance 9.0 Å). Since the processes are new examples in which a univalent cation is exchanged with a single phase transition in α-Zr(HPO4)2·H2O, the so called “polyfunctionality” of this exchanger has been discussed, considering the high polarizability of Ag+ and Tl+ ions. The catalytic potential applications of zirconium phosphate loaded with Ag+ ions are outlined.