A Study of Inorganic Ion Exchangers. VII. The Synthesis of γ-NH4ZrH(PO4)2 and Ion-exchange Properties of γ-Zr(HPO4)2·2H2O

The conditions for the synthesis of γ-NH4ZrH(PO4)2 and the ion-exchange properties of γ-Zr(HPO4)2·2H2O were investigated. The influence of the mole ratio of MH2PO4 (M=Na, K, and NH4) to ZrOCl2 on the formation of γ-zirconium phosphate using NaH2PO4 as MH2PO4 was such that the γ-form was obtained not in the NaH2PO4/ZrOCl2 mole ratio of 4, but in are of 8.3 or more. In case of the Na or K salt, a non-stoichiometric compound, MxZrH2−x(PO4)2, was obtained. When using the NH4 salt, a stoichiometric compound was synthesized at 120–280 °C in accordance with the following equation: ZrOCl2+NH4H2PO4→NH4ZrH(PO4)2+NH4Cl+HCl+H2O. Using an autoclave lined with Hastelloy-B and equipped with a stirrer, the synthesis was carried out by a reaction at 150–160 °C for 18–54 h. γ-Zr(HPO4)2·2H2O was prepared from NH4ZrH(PO4)2, and its ion-exchange capacity at pH 4.5 and selectivity quotient toward alkali metals and ammonium ions were measured. The measured values increased in the order of Li+<Cs+<Na+<K+<NH4+.