Leaching Properties of Alkali and Alkaline-Earth Metallic Elements Immobilized by HZr2(PO4)3

Mixtures of crystalline proton type zirconium phosphate, HZr2(PO4)(3), with (MNO3)-N-I (M-I = Li, Na, K, Rb, Cs) and M-II (NO3)(2) (M-II = Mg, Ca, Sr, Ba) were thermally treated at 700degreesC for 5 h, in order to investigate the immobilization of M-I and M-II. All M-I and M-II immobilized products gave X-ray diffraction (XRD) patterns attributable to (MZr2)-Zr-I(PO4)(3) and (MZr4)-Zr-II(PO4)(6) with a NASICON-type structure, and had the same crystal state as HZr2(PO4)(3). The a-axis lattice constant of (MZr2)-Zr-I(PO4)(3) and (MZr4)-Zr-II(PO4)(6) decreased monotonically with increasing the ionic radius of M-I and M-II, respectively, while the c-axis lattice constant increased. The electrical conductivity of (MZr2)-Zr-I(PO4)(3) and (MZr4)-Zr-II(PO4)(6) sintered at 1400degreesC decreased with increasing the ionic radius of M-I and M-II, respectively. Leaching tests for (MZr2)-Zr-I (PO4),(3) and (MZr4)-Zr-II (PO4)(6) were carried out at 160degreesC for 24 h in 1 mol . dm(-3)-HCl. The leaching rate decreased with increasing ionic radius of M-I and M-II, except for the case of Rb and Cs in (MZr2)-Zr-I(PO4)(3) and Sr and Ba in (MZr4)-Zr-II(PO4)(6).