Xylanase and laccase based enzymatic kraft pulp bleaching reduces adsorbable organic halogen (AOX) in bleach effluents: A pilot scale study

In present study, xylanase and laccase were produced in a cost-effective manner up to 10 kg substrate level and evaluated in elemental chlorine free bleaching of Eucalyptus kraft pulp. Compared to the pulp pre-bleached with xylanase (15%) or laccase (25%) individually, the ClO2 savings were higher with sequential treatment of xylanase followed by laccase (35%) at laboratory scale. The sequential enzyme treatment when applied at pilot scale (50 kg pulp), resulted in improved pulp properties (50% reduced post color number, 15.71% increased tear index) and reduced AOX levels (34%) in bleach effluents. The decreased AOX level in effluents will help to meet AOX discharge limits, while improved pulp properties will be value addition to the paper. (C) 2014 Elsevier Ltd. All rights reserved.