High-resolution solid-state NMR study on dissolution and alteration of Na-montmorillonite under highly alkaline conditions

Abstract

To clarify the structural change of Na-montmorillonite (Na-mon) with alkaline alteration, the structural analyses of Na-montmorillonite treated under highly alkaline conditions were performed by high-resolution solid-state 29Si/27Al-MAS and 3Q-MAS NMR and XRD. As a result, it is found that the bond angles (Si-O-Si) and bond lengths (Si-Si) show no variation, whereas the structural disorder around tetrahedral Si is reduced in altered samples. Moreover, the formation of analcime and its amorphous alumino-silicate precursors as secondary phases were certainly observed.