Journal
HOLZFORSCHUNG
Volume 64, Issue 2, Pages 153-159Publisher
WALTER DE GRUYTER & CO
DOI: 10.1515/HF.2010.019
Keywords
bleached pulp; bleaching; cellulose degradation; delignification; hydroxyl groups; oxygen radicals; selectivity
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The concentration of the hydroxyl radical generated during oxygen delignification was measured with a radical trapping agent. The N,N'-(5-nitro-1,3-phenylene)-bisglutaramide (NPG) was found to be effective but the experiments revealed that at pH higher than 11.5 the anionic form of hydroxyl radical the oxyl anion radical - causes up to four times more chain cleavage than the hydroxyl radical. It was also found that the effect of both radicals in the pulp moderated at higher partial oxygen pressure and in the presence of hemicelluloses. The implications are that selectivity can be improved by maintaining a moderate alkaline pH profile, increasing the oxygen partial pressure, and retaining hemicelluloses in the brownstock.
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