<Original Papers>Distribution of Cs, Sr, Ce, Eu and Tb into Na- and H-Type Zeolites

Effects of pH on the distribution of radioisotopes, ^Cs, ^Sr, ^Ce, ^Eu and ^Tb, into synthetic zeolites (A, X and Y), synthetic mordenite, natural mordenite and clinoptilolite have been investigated. Cesium ion was preferentially distributed into mordenite with a high distribution coefficient (K_=10^4) from acidic aqueous solution of pH 1 to 3. As for strontium, the K_ values into zeolites A, X and Y attained about 10^4 in the neutral region, but markedly decreased with increasing acidity. The distributions of rare earth elements at tracer-level concentrations into six kinds of Na-type zeolites were shown by the curves with a maximum at a different equilibrium pH. In the presence of carrier (10 ppm), these distribution curves broadened and overlapped. In the case of H-type zeolites, the cesium ion was also captured by zeolite in the acidic region (K_=10^4), while the multivalent cations had low distribution coefficients less than 10^2 at pH 2 and the K values decreased with increase in acidity