陽イオン交換マガディアイトの表面官能基と層空間の特性(II) : 水素イオン滴定と表面イオン化基

概要

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M-type magadiites (M_2Si_<14>O_<29>・nH_2O, M : Li, Na, K, Rb, Cs) prepared by exchanging Na^+ ion of magadiite (Na_2Si_<14>O_<29>・nH_2O) with a series of alkaline metal ions M^+, and silica gel treated with NaOH were studied by titrating their suspensions with HCl solution in an atmosphere of nitrogen. The reaction of neutralization was represented by the following equation. ≡Si-O^-M^++H^+→≡Si-OH+M^+ For the silica gel treated with NaOH, the resulting titration curve depicted upward curvature from the initial point to the equivalence point, because the dissociation constant of silanol groups is altered by the degree of neutralization. For M-type magadiite that is a layered polysilicic acid, on the contrary, the titration curves with definitive equivalence points were obtained, which correspond that of bases such as molecules or ion species with the definite dissociation constants. The titration curves obtained from Na-type magadiite showed only an equivalence point, and that from the others showed two equivalence points. These data indicated that the position of the structural hydroxyl groups (≡Si-OH) and the ionized groups (≡Si-O^-) on the magadiites differ according to kinds of interlayer cations. Na-type magadiite was characterized with regard to remote ≡Si-O^- groups each other, and the other types were characterized by adjacent those groups.
日本粘土学会の論文
2005-04-05