The role of water in the intercalation of kaolinite with potassium acetate

Water in intercalated kaolinites is observed first as bands in the hydroxyl-stretching region at 3300 to 3550 cm(-1) and by the water H-O-H bending vibrations in the 1560 to 1680-cm(-1) region. For potassium-acetate-intercalated kaolinite, hydroxyl-stretching bands attributed to water are observed at similar to 3540, similar to 3475, similar to 3430, and similar to 3380 cm(-1). Water bending modes are observed at 1560, 1586, 1610, and 1679 cm(-1). These bands are attributed to (a) water molecules adsorbed on the kaolinite surface, (b) zeolitic water, (c) molecular first layer water, and (d) ordered water on the hydroxyl surface, respectively. The intensities of the bands are a function of the method of preparation of the intercalated kaolinite, As the kaolinite was washed for varying time intervals, the 1560 cm(-1) band decreased in intensity more rapidly than the 1610 cm(-1) band. Even after washing for 24 h significant concentrations of water remained on the kaolinite and only heating removed the water. The 1560, 1586, and 1610 cm-l bands are attributed (a) to free or non-hydrogen-bonded water held in the interlayer spaces of the kaolinite, (b) to water in the hydration sphere of the potassium ion, and (c) to surface-adsorbed water on the kaolinite layers, In kaolinites intercalated under pressure, an additional band was observed at 1679 cm-l. It is proposed that this band is due to water coordinated to the kaolinite surface. (C) 1998 Academic Press.