Xylan accessibility of bleached eucalypt pulp in alkaline solutions
authors Gomes, TMP; de Sousa, ARM; Belenkiy, YI; Evtuguin, DV
nationality International
journal HOLZFORSCHUNG
author keywords Eucalyptus globulus; fibril aggregation; kraft pulping; refinability; xylan
keywords STRUCTURAL-CHARACTERIZATION; ACETYLATED HETEROXYLAN; CELLULOSE; HARDWOOD; EXTRACTION; HEMICELLULOSES; TEMPERATURE; RETENTION; SOFTWOOD; FIBERS
abstract The accessibility of glucuronoxylan from a refined, bleached Eucalyptus globulus industrial kraft pulp in 0-18% aqueous NaOH solution at room temperature (25 degrees C) was studied. The extraction profile revealed a maximum extraction of xylan in the pulp at about 10-12% NaOH concentration and was explained by the maximum swelling of the pulp according to the Gibbs-Donnan equilibrium. The kinetics of xylan removal and the monitoring of its structural features were performed at 5 and 10% NaOH concentrations. The maximum yields of xylans with 10% and 5% NaOH were as high as 90% and 60% for 2 h extraction, respectively. The structural features of xylan were assessed by acid methanolysis and one-dimensional (1D)/two-dimensional (2D) nuclear magnetic resonance (NMR), and the molecular weight by size exclusion chromatography (SEC). The xylan extracted with 10% NaOH had a slightly higher molecular weight and a lower branching with uronic moieties than the xylan extracted with 5% NaOH. The former was less pure (contained more beta-cellulose) than the latter. Structural studies by NMR resulted in the conclusion that there are at least two types of xylans removed from the pulp: one xylan with relatively high 4-O-methyl-alpha-D-glucuronosyl [MeGlcA-(1 ->] and [-> 2)-MeGlcA-(1 ->] substituents and another xylan with a much lower substitution with uronic residues.
publisher WALTER DE GRUYTER GMBH
issn 0018-3830
year published 2020
volume 74
issue 2
beginning page 141
ending page 148
digital object identifier (doi) 10.1515/hf-2019-0023
web of science category Forestry; Materials Science, Paper & Wood
subject category Forestry; Materials Science
unique article identifier WOS:000510621600006
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journal analysis (jcr 2019):
journal impact factor 1.826
5 year journal impact factor 1.828
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