Laccase-HBT bleaching of eucalyptus kraft pulp: influence of the operating conditions.
Different operating conditions (viz. pulp consistency, oxygen pressure and treatment time) in the biobleaching of eucalyptus kraft pulp with the laccase-HBT system was tested in order to describe their effect and normalize a biobleaching protocol. A high O(2) pressure (0.6MPa) was found to result in improved laccase-assisted delignification of the pulp. Also, a high pulp consistency (10%) and a short treatment time (2h) proved the best choices with a view to obtaining good pulp properties (kappa number and ISO brightness) under essentially mild conditions. The laccase-HBT treatment was found to result in slight delignification (in the form of a 20-27% decrease in kappa number); however, an alkaline extraction stage raised delignification to 41-45%, a much higher level than those obtained in the control tests (16-23%). Also, the use of hydrogen peroxide in the extraction stage resulted in improved brightness (14-19%), but in scarcely improved delignification (4-7%). Treating the pulp with the laccase-HBT system reduced the amount of hydrogen peroxide required for subsequent alkaline bleaching by a factor of 3-4 relative to control tests.
Moldes
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Department of Textile and Paper Engineering, Universitat Politècnica de Catalunya, Colom 11, E-08222 Terrassa, Spain. diegmoldes@gmail.com
Vidal
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T
D005052:Eucalyptus / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D042845:Laccase / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010209:Paper; D011312:Pressure; D013997:Time Factors; D014865:Waste Disposal, Fluid
D006861:Hydrogen Peroxide; D042845:Laccase; D010100:Oxygen