Effect of hydrothermal treatments on ion exchange and physicochemical properties of zirconium phosphate

The effect has been studied of hydrothermal treatments at 300 deg C on the physicochemical and ion-exchange properties of the crystalline α-form of zirconium phosphate of Zr(HPO4)2xH2O composition and of amorphous specimens with a P/Zr ratio of 1.04 and 1.57. On prolonged hydrothermal treatments (200-300 hr), amorphous specimens crystallize with the formation of a phase with a P/Zr ratio of 1.33, which possesses no ion-exchange properties. The composition of the phase corresponds to Zr3(PO4)4x2H2O formula. When the specimen is autoclaved in a salt solution the crystallization is accompanied by irreversible cation adsorption. In hydrothermal conditions, the crystalline α-form is characterized by high hydrolizability as compared with amorphous specimens. Accumulation of phosphate ions in the contacting solution stabilizes the initial structure of the specimen