Synthesis of LiAl2(OH)(6)(+) intercalated montmorillonite by a hydrothermal soft chemical reaction

A LiAl2(OH)(6)(+) intercalated montmorillonite was prepared from a montmori llonite by using a hydrothermal soft chemical process. As a first step, lit hium aluminium hydroxide complex ions (LixAln(OH)(m)(z+)) were inserted int o the interlayer space of the montmorillonite by an ion-exchange reaction. In the second step, the ion-exchanged montmorillonite was hydrothermally tr eated to polymerize the complex ions in the interlayer space, forming a san dwich-like layered compound. The mechanism of formation of the sandwich lay ered structure was investigated by XRD, TG-DTA, chemical analyses and FTIR spectroscopy. Na+ and Ca2+ ions in the interlayer space of the montmorillon ite were first exchanged with LixAln(OH)(m)(z+) complex ions, and during th is process the basal spacing of the montmorillonite increased from 1.6 to 2 .0 nm after the ion-exchange. Two types of reactions of the ion-exchanged m ontmorillonite were observed under the hydrothermal conditions. In the temp erature range 100-150 degrees C, the basal spacing changed from 2.0 to 1.7 nm, corresponding to polymerization of LixAln(OH)(m)(z+) complex ions to Li Al2(OH)(6)(+) layers between the silicate layers. At temperatures over 200 degrees C, Li+ ions of LiAl2(OH)(6)(+) layers probably migrated into the oc tahedral sheets of silicate layers, accompanied by a decrease of the basal spacing from 1.7 to 1.4 nm. The LixAln(OH)(m)(z+) complex ion was also used for pillaring montmorillonite, and a pillared montmorillonite with a basal spacing of 1.5 nm was obtained by heat treatment of this LixAln(OH)(m)(z+) ion-exchanged montmorillonite in air at 500 degrees C.