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Title: FT-Raman investigation of bleaching of spruce thermomechanical pulp

Source: Journal of pulp and paper science. Vol. 30, no. 10 (Oct. 2004): Pages 269-274

Author(s)Agarwal, U.P.; Landucci, L.L.

Publication Year: 2004  View PDF »

Category: Journal Articles

Abstract: Spruce thermomechanical pulp was bleached initially by alkaline hydrogen peroxide and then by sodium dithionite and sodium borohydride. Near-infrared Fourier-transform-Raman spectroscopy revealed that spectral differences were due primarily to coniferaldehyde and p-quinone structures in lignin, new direct evidence that bleaching removes p-quinone structures. In unbleached pulp, the contribution of p-quinones was detected in the 1665-1690 cm-1 region. This contribution was removed to varying degrees in bleached pulps, depending on the extent to which the pulps were brightened. The relative change in the post-colour number of pulp was correlated linearly with the Raman intensity decline in the 1665- 1690 cm-1 region, indicating that p-quinone structures were largely responsible for determining pulp brightness. The 13C nuclear magnetic resonance spectra of milled softwood lignins, obtained to further support the Raman findings, exhibited a peak at ~180 ppm due to quinones. This peak was not detected in the spectra of milled hardwood lignins.

Keywords: Thermomechanical pulps, Fourier analysis, Raman spectroscopy, Picea, bleached pulps, quinones

File size: 504 kb(s)

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RITS Product ID: 16416
Current FPL Scientist associated with this product
Agarwal, Umesh P.
Research Chemist

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