Birdwood Kaolinite: a Highly Ordered Kaolinite that is difficult to Intercalate - an XRD, SEM and Raman Spectroscopic Study

The intercalation of a highly ordered kaolinite from Birdwood, South Australia has been studied using a combination of electron microscopy, X-ray diffraction and Raman microscopy. Highly ordered kaolinites normally intercalate easily and to a high degree. The kaolinite under study was found to intercalate acetamide and formamide with difficulty and more than 18 days were required to achieve more than 20 % intercalation. Further treatment did not improve the degree of intercalation past 60 %. The difficulty of intercalation is attributed to the co-existence of two kaolinite phases, a highly ordered (with a Hinckley index > 1.3) and a highly disordered kaolinite, the latter material appears to coat the highly ordered kaolinite thereby limiting the intercalation. The presence of two forms of silica and a dickite were identified in the sample using X-ray diffraction

Molecular structure of dimethyl sulfoxide intercalated kaolinites

Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm for the high-defect kaolinite. An additional band at 3598 cm was observed for the high-defect kaolinite. The band at 3660 cm was assigned to the inner-surface hydroxyls hydrogen bonded to the S=O group. The other three bands are attributed to the hydroxyl stretching frequencies of water in the intercalation complex. The hydroxyl deformation region is characterized by one intense band in both the FTIR and Raman spectra at 905 cm. Significant changes in the Raman spectra of the intercalating molecule are observed. Splitting of the C-H symmetric and antisymmetric stretching vibrations occurs. Two Raman bands at 2917 and 2935 cm and four bands at 2999, 3015, 3021, and 3029 cm are observed. The in-plane methyl bending region shows two Raman bands at 1411 and 1430 cm. The DRIFT spectra show complexity in these regions. The S=O stretching region shows bands at 1066, 1023, and 1010 cm upon intercalation with DMSO for the low-defect kaolinite and 1058, 1028, and 1004 cm for the high-defect kaolinite. The 1058 cm band is signed to the free monomeric S=O group and the 1023 and 1010 cm bands to two different polymeric S=O groups. Bands attributed to the C-S stretching vibrations, the in-plane and out-of-plane S=O bending and the CSC symmetric bends all move to higher frequencies upon intercalation. It is proposed that intercalation with DMSO depends on the presence of water and that the additional bands at 3536 and 3501 cm are due to the presence of water in the intercalate

Role of water in the intercalation of kaolinite with hydrazine

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 for the low-defect kaolinite and at 3600 and 3555 cm 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. Water bending modes are observed at 1578, 1598, 1612, 1627, 1650, and 1679 cm for the hydrazine-intercalated low-defect kaolinite and at 1578, 1598, 1613, 1627, 1652, and 1678 cm 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 bands increased in intensity as the intensity of the 1612 cm 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 bands as well as the 1627 cm 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 are attributed to water coordinated to the siloxane surface

Modification of the kaolinite hydroxyl surfaces through intercalation with potassium acetate under pressure

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°C, the Raman spectra showed additional bands at 3590, 3603, and 3609 cm. The DRIFT spectra of this intercalate showed new bands at 3595 and 3605 cm. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate anion. Intercalation under 20 bars pressure at 220°C caused the differentiation of the inner surface hydroxyl groups, resulting in these additional bands. By using milder conditions of 2 bars and at 120°C, additional Raman bands were found at 3592, 3600, and 3606 cm. If the kaolinite was intercalated at 1 bar and 100°C, a new broad Raman band was found at 3605 cm. 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

Modification of the kaolinite hydroxyl surfaces through intercalation with potassium acetate under pressure

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°C, the Raman spectra showed additional bands at 3590, 3603, and 3609 cm. The DRIFT spectra of this intercalate showed new bands at 3595 and 3605 cm. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate anion. Intercalation under 20 bars pressure at 220°C caused the differentiation of the inner surface hydroxyl groups, resulting in these additional bands. By using milder conditions of 2 bars and at 120°C, additional Raman bands were found at 3592, 3600, and 3606 cm. If the kaolinite was intercalated at 1 bar and 100°C, a new broad Raman band was found at 3605 cm. 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

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 and by the water H-O-H bending vibrations in the 1560 to 1680-cm region. Far potassium-acetate-intercalated kaolinite, hydroxyl-stretching bands attributed to water are observed at ~3540, ~3475, ~3430, and ~3380 cm. Water bending modes are observed at 1560, 1586, 1610, and 1679 cm. 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 band decreased in intensity more rapidly than the 1610 cm 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 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. It is proposed that this band is due to water coordinated to the kaolinite surface