The cation-exchange characteristics of Na-substituted taeniolite (NaT) and Na-substituted hectorite (NaH) for Cs
+ were investigated in aqueous solutions at 25°C. These synthetic fluoromicas swell in water. Cs
+ exchange reaction on NaT appeared to attain steady states within 8 h. The most uptake amount of Cs
+ on NaT was 1.15 mmol/g. The Na
+⇔Cs
+ exchange isotherm on NaT rose steeply and reached a plateau above the diagonal line in the lower concentration region. It was found that NaT had high selectivity for Cs
+ in the low concentration region of Cs
+. The distribution coefficient,
Kd, for Cs
+ on NaT under a large excess of Na
+ or Ca
2+ was 4.7×10
4ml/g and 3.1×10
6ml/g, respectively. NaT takes up Cs
+ from mixed solutions of large amount of Na
+ or Ca
2+and small amount of Cs
+. These results suggest that NaT is useful for separation and immobilization of Cs
+.
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