Transformation of the Near-Infrared Bands of Cellulose Surface Hydroxyls under the Influence of Adsorbed Water Molecules

Abstract

Near-infrared absorption spectra of sulfite cellulose with a varied adsorbed water content were studied. Analysis of the spectra has been made on the basis of previously published relations and results of the cellulose surface hydroxyls' interaction with absorbed water. Spectra of the OH overtone region of 1.3–1.65 μm were deconvoluted to components of cellulose volume and surface hydroxyls as well as to those of absorbed water. Besides the 1.53–1.55 μm component of “bound” water, the 1.42–1.44 μm component of “free” water starts to grow as the surface coverage exceeds 1.5. Comparison of the peak positions of these water components with those of liquid water suggests that bound water is constituted of hydrogen-bonded molecules. The 1.42–1.44 μm component of free water implies nonhydrogen-bonded and partially hydrogen-bonded molecules. The whole 1.363 μm band and a part of the 1.424 μm band of surface hydroxyls turn into the 1.52–1.53 and 1.57–1.59 μm peaks, respectively, after attachment of H2O molecules. The red shift of the surface bands by approximately 780 cm−1 caused by the adsorbate is consistent with a shift of the fundamental OH band of silica gel. The possible chemical, morphological, and physical causes of the two 1.363 and 1.424 m surface hydroxyl bands are discussed.

Application of near Infrared Spectroscopy to Assessments of Colour Change in Plantation-Grown Eucalyptus Grandis Wood Subjected to Heat and Steaming Treatments

“…Recently, near infrared (NIR) spectroscopy has been applied widely and successfully to the fi eld of wood science due to its quick speed, accuracy and directness, in particular it is capable of monitoring the experimental process. Some progress has already been made on estimations of anatomical properties, 12 measurements of physical properties such as density, 13 moisture content and roughness of surface, 14 determination of mechanical properties, 13,[15][16][17] analyses of chemical properties, 18 non-destructive measurement of wood properties 19 and some application in the forest product industry. 20 However, little information has been reported on applications of NIR spectroscopy to assess the colour change of collapse-susceptible E. grandis wood subjected to heat and steaming treatments.…”

High‐quality and efficient recovery of waste agricultural mulch film mixture via solid‐state shear milling technology

“…The changes in chemical groups of powders with different milling times were characterized by infrared spectroscopy (Figure 5a). The broad peak in the region of 3500–3000 cm −1 was the stretching vibration peak of the cellulose hydroxyl group, and the hydrogen bond would make the peak move to the direction of low wavenumber 31 . With the increase in the number of milling times, the peak gradually moved to the high wavenumber, from 3330 (1 cycle) to 3440 cm −1 (9 cycles).…”

“…The broad peak in the region of 3500-3000 cm À1 was the stretching vibration peak of the cellulose hydroxyl group, and the hydrogen bond would make the peak move to the direction of low wavenumber. 31 With the increase in the number of milling times, the peak gradually moved to the high wavenumber, from 3330 (1 cycle) to 3440 cm À1 (9 cycles). This may be due to the fact that under the strong three-dimensional shear force, the hydrogen bonds of the molecular bonds of cellulose were destroyed, so some free hydroxyl groups were exposed.…”

Spectral Pre-Treatment for Diffuse Transmittance Linearity Improvement

“…This elimination can be achieved by the appropriate truncation of measured absorbance by the -log(T 0 ) subtraction. 15,34,35 In this publication, spectra of truncated absorbance…”

“…The peaks represent the same bond types as observed for the ν 1 + ν 3 overtone band of adsorbed water. 35 Water molecules can be bonded to adsorbent and to each other in the following modes: . The adsorbed H 2 O peak positions are known for matrices other than cellulose.…”