Effect of treatment temperature on the immobilization of Cs and Sr to HZr2(PO4)3 using an autoclave

The proton-type crystalline zirconium phosphate, HZr2(PO4)3, was used to immobilize Cs+ or Sr2+ by mixing HZr2(PO4)3 and an aqueous solution of CsNO3 or Sr(NO3)2 in an autoclave at 160–400 °C. The Cs or Sr immobilized HZr2(PO4)3 was further kept in the open air at 300–700 °C. The effect of treatment temperature on the immobilized amount of Cs or Sr in HZr2(PO4)3 and the leaching rate of Cs or Sr from its immobilized HZr2(PO4)3 was discussed from the standpoint of crystalline structure. The immobilization and the stabilization of Cs or Sr in HZr2(PO4)3 produced in an autoclave at 250 °C were better achieved by additional thermal treatment in the open air at 700 °C.