Immobilization of Cs and Sr to HZr2(PO4)3 using an autoclave

The proton-type crystalline zirconium phosphate, HZr2(PO4)3, was prepared by a thermal decomposition of NH4Zr2(PO4)3 at about 450 °C, where NH4Zr2(PO4)3 was obtained in advance by a hydrothermal synthesis using a mixed solution of ZrOCl2, H3PO4 and H2C2O4. Cs or Sr ion was immobilized to HZr2(PO4)3 by mixing HZr2(PO4)3 with an aqueous solution of CsNO3 or Sr(NO3)2 under the molar ratio CsNO3/HZr2(PO4)3 = 1.0 or Sr(NO3)2/HZr2(PO4)3 = 0.5. The mixtures were treated thermally in an autoclave at different temperatures from 200 to 275 °C and Arrhenius equation was applied to the Cs and Sr immobilization process to HZr2(PO4)3. The activation energy for the immobilization process of Cs or Sr was estimated as 179 kJ mol−1 and 186 kJ mol−1, respectively.