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- Sevastyanova, OlenaKTH,Träkemi och massateknologi (author)
Bleaching of eucalyptus kraft pulps with chlorine dioxide : Factors affecting the efficiency of the final D stage
- Article/chapterEnglish2011
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- 2011
- printrdacarrier
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- LIBRIS-ID:oai:DiVA.org:kth-150600
- https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150600URI
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- Language:English
- Summary in:English
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- QC 20140908
- The bleaching efficiency of the final D stage in the D 0(EP) D 1D 2 bleaching sequence was investigated focusing on the effect of pH in relation to the bleaching history of pulp samples. The pulps used were unbleached kraft Eucalyptus grandis pulps with a kappa number of 14.8, and the same pulp oxygen-delignified to kappa numbers 12 and 9.8. The samples were bleached according to the D 0(EP)D 1 sequence to a brightness of about 86% ISO and then submitted to the final D 2 stage under identical conditions. The target final brightness was 90.5% ISO. Changes in the kappa number, brightness, viscosity and contents of hexenuronic acid (HexA), 4-O-methylglucuronic acid and the total amount of carboxylic acid groups in pulps were monitored during the bleaching sequence. The target brightness in the D 2 stage was achieved for all pulps, but this required a different final pH for individual samples, indicating dissimilarities between chromophore types in them. In general, brightness increased as the pH increased from 3 to 6. The optimal value with respect to pulp viscosity was between pH 3 and 5. Despite unlike conditions applied in previous bleaching stages, the samples after the D 1 stage revealed similar residual lignin contents as shown by kappa number analysis. The content of hexenuronic acid in the samples was, however, found to vary broadly in the range from 2 to 26 mmol/kg. Conductometric titration showed different amounts of carboxylic (COOH) groups in pulps after the D 1 stage, of which HexA accounted for only a minor part. Since the content of 4-O-methylglucuronic acid groups was similar for all samples, the difference in the amount of COOH groups was mainly associated with oxidation of the residual lignin. Some of the charges might also originate from oxidized cellulose. It was concluded that the variations in the fiber charge result from the different bleaching conditions applied prior to the D 1 stage.
Subject headings and genre
- NATURVETENSKAP Kemi hsv//swe
- NATURAL SCIENCES Chemical Sciences hsv//eng
- 4-O-methylglucuronic acid
- Bleaching history
- Brightness
- ECF bleaching
- Eucalyptus kraft pulp
- Fiber charge
- Final D 2 stage
- Hexenuronic acid
- Kappa number
- pH
- Viscosity
- Kappa numbers
- Bleaching
- Carboxylic acids
- Chromophores
- Kraft process
- Kraft pulp
- Lignin
- Luminance
- pH effects
- Unbleached pulp
- Cleaning
- Eucalyptus
- Kraft Pulps
- Lignins
- Unbleached Pulps
Added entries (persons, corporate bodies, meetings, titles ...)
- Forsström, A. (author)
- Wackerberg, E. (author)
- Lindström, Mikael E.KTH,Träkemi och massateknologi(Swepub:kth)u1uxn4q9 (author)
- KTHTräkemi och massateknologi (creator_code:org_t)
Related titles
- In:Int. Pulp Bleach. Conf., IPBC, s. 376-4039781618394347
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