ABSTRACT
Water in intercalated kaolinites is observed first as bands inthe hydroxyl-stretching region at 3300 to 3550 cm-1 and bythe 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 approximately 3540, approximately 3475, approximately 3430, and approximately 3380 cm-1. Water bending modes areobserved 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) orderedwater on the hydroxyl surface, respectively. The intensities ofthe 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-1 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-1. It is proposed that this band is due to water coordinated to the kaolinite surface. Copyright 1998 Academic Press.
ABSTRACT
Kaolinite hydroxyl surfaces have been modified upon intercalation with potassium acetate under a range of conditions. Modification is observed by changes in the hydroxyl stretching region using Raman and infrared spectroscopy. Upon the intercalation of low defect kaolinite with potassium acetate under a pressure of 20 bars and 220 degreesC, the Raman spectra showed additional bands at 3590, 3603, and 3609 cm-1. The DRIFT spectra of this intercalate showed new bands at 3595 and 3605 cm-1. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate anion. Intercalation under 20 bars pressure at 220 degreesC caused the differentiation of the inner surface hydroxyl groups, resulting in these additional bands. By using milder conditions of 2 bars and at 120 degreesC, additional Raman bands were found at 3592, 3600, and 3606 cm-1. If the kaolinite was intercalated at 1 bar and 100 degreesC, a new broad Raman band was found at 3605 cm-1. It is proposed that the effect of intercalation of the low defect kaolinite under pressure caused the kaolinite to become disordered and this disordering was dependent upon the temperature of intercalation. Copyright 1998 Academic Press.
ABSTRACT
A low-defect kaolinite of 7.18-Å basal spacing was expanded upon intercalation with hydrazine. The 001 d-spacing was broad and the peak resolved into components at 10.28, 9.48, and 8.80 Å. It was found that the ordered kaolinite predominantly expanded to 9.48 Å with 31.2% and 10.28 Å with 38.0% of the total peak area. A high-defect kaolinite showed expansion by hydrazine in identical steps with d-spacings of 10.27, 9.53, and 8.75 Å. It is proposed that the intercalation of the kaolinite by hydrazine occurs according to the orientation of the hydrazine molecule and that water plays an integral part in the process of kaolinite expansion. For the hydrazine-intercalated kaolinite, hydroxyl stretching bands attributed to water are observed at 3413, 3469, and 3599 cm-1 for the low-defect kaolinite and at 3600 and 3555 cm-1 for the high-defect kaolinite. Upon the exposure of the low-defect hydrazine-intercalated kaolinite to air, an additional water band is observed at 3555 cm-1. Water bending modes are observed at 1578, 1598, 1612, 1627, 1650, and 1679 cm-1 for the hydrazine-intercalated low-defect kaolinite and at 1578, 1598, 1613, 1627, 1652, and 1678 cm-1 for the hydrazine-intercalated high-defect kaolinite. The intensities of these bands are a function of the exposure to air and measurement time. The 1650- and 1679 cm-1 bands increased in intensity as the intensity of the 1612 cm-1 band decreased. Even after exposure to air for 24 h, water remained in the kaolinite interlayer space and only after heating was the water removed. The 1578, 1598, and 1612 cm-1 bands as well as the 1627 cm-1 band are attributed to (a) free or non-hydrogen-bonded water held in the interlayer spaces of the kaolinite, (b) water in the hydration spheres of the hydrazine, and (c) adsorbed water on the kaolinite surface. In kaolinites additional bands at 1650 and 1679 cm-1 are attributed to water coordinated to the siloxane surface. Copyright 1998 Academic Press.
