Radical Formation in Ozone Reactions with Lignin and Carbohydrate Model Compounds
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M. Ragnar
Summary
Using different independent methods, the kinetics of ozone consumption and the initial radical yield in reactions of ozone with lignin and carbohydrate model compounds were investigated. It was demonstrated that ozone reacts with phenolates several orders of magnitude more rapidly than with corresponding undissociated phenols. The pH dependence of the radical yield does not completely follow the pKa-value of the phenols. In fact, the radical yield starts to increase at pH 3 for all the phenolic model compounds investigated. Several indications suggest that superoxide rather than the hydroxyl radical is initially formed when ozone reacts with lignin model compounds. In contrast to lignin model compounds no radicals were detected in ozone reactions with carbohydrate model compounds or olefins. On the basis of this study, it may be concluded that ozone bleaching should preferably be performed at pH 3 and at a higher consistency. No significant effect of metal ions was observed.
Copyright (c)1999 by Walter de Gruyter GmbH & Co. KG
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Artikel in diesem Heft
- Effects of Heat Treatments of Wood on the Feeding Behaviour of Two Subterranean Termites
- The Resistance of Wood Chemically Modified with Isocyanates. Part 1. Brown Rot, White Rot and Acid Chlorite Delignification
- Effect of IPBC/DDAC on Spore Germination and Hyphal Growth of the Sapstaining Fungus Ophiostoma piceae
- Estimation of Effect of Passage Through the Gut of a Lower Termite, Coptotermes formosanus Shiraki, on Lignin by Solid-State CP/MAS 13C NMR
- Biodegradability of Extractives in Sapwood and Heartwood from Scots Pine by Sapstain and White-Rot Fungi
- Fractional Isolation and Characterization of Polysaccharides from Oil Palm Trunk and Empty Fruit Bunch Fibres
- Rapid Determination of the Chemical Composition and Density of Pinus radiata by PLS Modelling of Transmission and Diffuse Reflectance FTIR Spectra
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- Radical Formation in Ozone Reactions with Lignin and Carbohydrate Model Compounds
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