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Title
Comparative kinetic analysis of a laccase-mediator system treatment of pulp after oxygen delignification and chlorine dioxide bleaching
Authors
G. Radeva I. Valchev and E. Valcheva
Received
July 31, 2009
Published
Volume 43 Issue 7-8 July-August
Keywords
laccase-mediator system, oxygen delignification, chlorine dioxide bleaching, exponential kinetic
Abstract
The effect of Novozyme AS laccase and of the 1-hydroxybenzotriazole mediator on unbleached and oxygen delignified kraft pulp is studied. The kinetic investigations, based on the relatively decreasing kappa number and light adsorption coefficient, show that an exponential kinetic equation valid for processes taking place on uniformly inhomogeneous surfaces can explain the action of the laccase-mediator system (LMS). The activation energy found remains constant during the bleaching processes, while the preexponential factor changes, thus determining the current rate decrease. The correlations derived between the kinetic characteristics depend neither on temperature nor on the reaction time. The investigations carried out indicate that delignification becomes the prevailing process in the LMS treatment, followed by chlorine dioxide bleaching. The process leading to the chromophoric decrease starts to dominate the complex process when the LMS treatment is followed by oxygen delignification.
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