Xylanase Treatment of Oxygen-Bleached Hardwood Kraft Pulp at High Temperature and Alkaline pH Levels Gives Substantial Savings in Bleaching Chemicals

摘要

Oxygen-delignified hardwood kraft pulp was treated with a xylanase from Thermotoga maritima at pH 10 and 90℃ and then bleached with the sequence D_0ED_1ED_2. A brightness of 90.5% ISO was achieved for the xylanase-treated pulp, whereas a brightness of 86.7% ISO was achieved when the untreated pulp (the xylanase stage left out) was bleached with the same D_0ED_1ED_2 sequence. Xylanase treatment of the pulp at pH 10 and 90℃ reduced the chlorine dioxide consumption in the subsequent bleaching by 25% at a target brightness of 86.7% ISO. These results demonstrate that the T. maritima xylanase is effective at pH 10, 90℃ in enhancing pulp bleaching.