Effect of xylanase treatment on chlorine dioxide kinetics and alkaline extraction efficiency during pulp bleaching

Xylanase enzymes have been successfully employed in pulp manufacturing as a means to reduce bleaching chemical demand. Referred to as bleach boosting, the mechanism by which the enzyme treatment reduces chemical demand is still not fully understood. In order to better quantify the bleach boosting effect, the impact of the xylanase treatment on chlorine dioxide delignification was studied on a northeastern hardwood. While the enzyme treatment did result in a direct reduction in the kappa number, the treatment had no effect on the rate of chlorine dioxide delignification. It was also demonstrated that the enzyme treatment did not affect the reduction in kappa number across the extraction stage. The results indicate that the enzyme treatment has no effect on either the bleaching stage or the extraction stage, suggesting that the bleach boosting effect maybe a result of the direct removal of lignin during the enzyme stage.