ON THE ROLE OF XYLAN IN THE FINAL BLEACHING OF EUCALYPT KRAFT PULPS WITH HYDROGEN PEROXIDE AND CHLORINE DIOXIDE

摘要

Isolated xylans from partially (DED) and fully (DEDD/DEDP) bleached eucalypt kraft pulps were characterized using 1H NMR, UV-Vis in cadoxen solutions, size exclusion chromatography and UVResonance Raman spectroscopy. A comparative analysis was done for xylan isolated from partially bleached pulp (DED) and subjected to treatment either with chlorine dioxide or hydrogen peroxide under the same final bleaching conditions. Chlorine dioxide final stage induced new unsaturated moieties in xylan structure, while hydrogen peroxide was very effective in the removal of xylan-related chromophores. The role of xylan into the delay of brightness development in the fmal chlorine dioxide stage was highlighted.