Improvement of kraft pulp bleaching by treatments with laccase, urea, and refining
2013 (English)In: Holzforschung, ISSN 0018-3830, Vol. 67, no 6, 651-658 p.Article in journal (Refereed) Published
Unbleached Eucalyptus kraft pulps were treated by three methods and the bleaching effects have been evaluated. The treatments were performed by a laccase mediator system (LMS), refining (R), and urea (U) alone and in combination of these methods. The bleached pulps were characterized in terms of κ number, hexenuronic acid content, brightness, and viscosity. In addition, the lignin-carbohydrate complexes (LCCs) were fractionated and characterized with regard to the fractionation yield, lignin content, and carbohydrate composition. Moreover, the 1 H nuclear magnetic resonance spectra were recorded and the thioacidolysis-gas chromatography and thioacidolysis-size exclusion chromatography analyses were performed. The LMS treatment resulted mainly in a slightly better delignification as manifested by a κ number (K no.) reduction of 0.8 units. The effects of the U treatment included delignification (1.4 κ units), hexenuronic acid removal (3 μ mol g-1), and improved pulp brightness (3.4 ISO units). The R treatment darkened the pulp (3 ISO units), whereas the bleaching of the R-pulp by subsequent LMS or U treatment enhanced the brightness (0.5 unit more) or delignification (0.3 unit more). The residual lignin in the pulp samples was present mainly as xylan-lignin. The Klason lignin content from the xylan lignin fraction decreased as the degree of delignification increased. The pulp darkening followed by the R treatment was interpreted as the result of the formation of condensed lignin structures, but these condensed lignins were substantially removed by the subsequent LMS or U treatment.
Place, publisher, year, edition, pages
2013. Vol. 67, no 6, 651-658 p.
bleaching, Eucalyptus, laccase-mediator system, lignin-carbohydrate complex (LCC), refining, thioacidolysis, urea
IdentifiersURN: urn:nbn:se:kth:diva-126277DOI: 10.1515/hf-2012-0140ISI: 000324719100005ScopusID: 2-s2.0-84904999585OAI: oai:DiVA.org:kth-126277DiVA: diva2:642052
QC 201310172013-08-202013-08-202013-10-17Bibliographically approved