The amount and the thermal behavior of interlayer water in original kenyaite (Na
2Si
22O
41 (OH)
8 6H
2O), and Li, Na, K, Rb, Cs ions-saturated kenyaite were mainly examined by means of X-ray diffraction, differential thermal analysis, and thermal gravimetric analysis.
The amount of interlayer water in the modifications were decreased with decreasing amount of alkali metal ions, and in the order Na
+ > K
+ >R13
+> Cs
+, which varied with the size of cation radius or the hydration energy for cations. In the case of Li and Cs modifications, however, the interlayer water content and the interlayer spacing showed relatively lower values than that of the other type modifications. Cs
+ ion in the modification may be fixed in the eight-membered ring on the interlayer surface. Li
+ion are presumed to be fixed by the adjacent=Si-OH group and=Si-O
-on the surface.
The dehydration of interlayer water in Li, Na, K, Rb, and Cs ion modifications were carried out stepwise as 4, 4, 2, 3, and 3 steps, respectively. The water molecules released at the first step (dehydration at lowest temperature) for every modification may have formed hydration bond to the interlayer surface silanol group (Si-OH). The water molecules released at the last step (dehydration at highest temperature) may have been present in the state that has been strongly attracted to exchangeable cations, because a plot of the temperature of last dehydration step of them T
d (T
d: temperature of highest endothermic DTA peak) vs. the enthalpy of hydration ΔH
h° for alkali metal ions gave linear relationship.
抄録全体を表示