Combination Bands in the Infrared Spectroscopy of Kaolins—A Drift Spectroscopic Study

Abstract

Abstraet--Kaolinites with varying degrees of defect structures have been studied by both mid-infrared (IR) and near-IR diffuse reflectance spectroscopy (DRIFT). Difference bands were observed in the 2650-to 2750-cm I region. This region coincides with the kaolinite-deuterated hydroxyl stretching region. Summation bands were observed in the near-IR spectra in the 4500-to 4650-cm -~ and in the 7050-to 7250-cm t region. Each of the spectral regions of the summation and difference bands is both kaolin polytype and sample dependent. It is proposed that each of these sets of bands arises from the combination of the hydroxyl stretching frequencies and the hydroxyl deformation frequencies and, to a lesser extent, the silicon-oxygen symmetric stretching vibration of the siloxane layer. Additional difference bands of very low intensity were also observed at 2930 and 2856 cm i. Combination bands were observed in all kaolinites at 2137 and 2227 cm-L Each of the 3 major combination spectral regions was composed of 5 component bands corresponding to the 4 IR active and the 1 Raman active kaolinite hydroxyl stretching frequencies. Combination bands were also observed at --1932 and 1821 cm-L

Changes in Structure, Morphology, Porosity, and Surface Activity of Mesoporous Halloysite Nanotubes Under Heating

“…This technique is more useful than FTIR for detection of the hydroxyl stretching region of silicate minerals (Frost and Johansson, 1998). It works with no interference through sample preparation and is sensitive to the detection of surface groups (Frost and Johansson, 1998;Yuan et al, 2004).…”

“…This technique is more useful than FTIR for detection of the hydroxyl stretching region of silicate minerals (Frost and Johansson, 1998). It works with no interference through sample preparation and is sensitive to the detection of surface groups (Frost and Johansson, 1998;Yuan et al, 2004). The DRIFT spectra of halloysite heating products showed no evident change with increased heating temperature through 400ºC (Figure 4aÀc), but after heating at 500ºC the bands due to OÀH vibration of both inner-surface hydroxyl groups (at 3700 cm À1 ) and inner hydroxyl groups (3626 cm À1 ) were much smaller (Figure 4c).…”

Baseline Studies of the Clay Minerals Society Source Clays: Infrared Methods

“…In addition, reflectance spectra in the near-IR (NIR) region (11,000-4000 cm ~), where overtones and combination vibrations occur, are included. These spectra provide information on structural OH groups and H20 in clay minerals (Bishop et al, 1994;Frost and Johansson, 1998;Petit et al, 1999a) which may not be clearly observed in the MIR spectra. Small changes in stretching and bending band positions are additive in the combination bands, thereby making them more readily differentiated (Post and Noble, 1993).…”

“…The DRIFT technique is most appropriate in the NIR region, where no dilution of the sample is necessary. Thus, DRIFT is suitable for studies of hydroxyl vibrations of clays in both MIR and NIR regions (Frost and Johansson, 1998). This paper summarizes data from FTIR spectra in the NIR and MIR regions (I 1,000-400 cm -J) of many of the Source Clay samples, using both transmission and reflectance techniques.…”

Synthesis and Characterization of Marine Clay-Supported Nano Zero Valent Iron

“…Strong adsorption peaks observed in FTIR spectra of marine clay at the range of 900-1100 cm −1 indicates the functional group of silicate ion (Coates, 2000). The adsorption peaks had reduced in FTIR spectra of MC+nZVI due to the destruction of Si-O bonds by alkali, resulting from the reaction of NaBH 4 and H 2 O during preparation of nZVI (Frost and Johanssont, 1998;Yuan et al, 2008;Zhang et al, 2011). New adsorption peaks at the range of 532.7-466.4 cm −1 indicating Fe-O stretching of Fe 2 O 3 and Fe 3 O 4 were observed.…”