Immobilization of cesium by crystalline zirconium phosphate

HZr2(PO4)3 was prepared by the thermal decomposition of NH4Zr2(PO4)3 which was synthesized in advance by a hydrothermal reaction from a mixed solution of ZrOCl2, H3PO4 and H2C2O4. Mixtures of HZr2(PO4)3 with various amounts of CsNO3 were treated at 700–1200°C, in order to investigate the immobilization of Cs ion. When a mixture of CsNO3/HZr2(PO4)3 in a molar ratio of 0.36 was treated at 700°C, the main product was suggested to be CsZr2(PO4)3 from XRD measurements. The leaching rate of Cs ion from this product was less than 10−10 g · cm−2 · day−1 in 0.1 mol · 1−1 HCl solution at 100°C, indicating that HZr2(PO4)3 reacts with CsNO3 to give a stable Cs-immobilized product.