キシラナーゼ利用によるＢＫＰ製造時の塩素または二酸化塩素の削減

Pulp and paper industry is one of the major contributors to environmental pollution due to its toxic and carcinogenic discharges during its various processes e.g., chlorinated bleaching of the pulp. Use of alternative bleaching chemicals e.g., enzyme and/or elemental chlorine free (ECF) or total chlorine free (TCF) agents are the best option to reduce the load of carcinogenic chlorinated compounds on our environment. Present study was carried out to highlight the application of enzyme during bleaching of wheat straw anthraquinon (AQ)-soda pulp to considerably reduce the toxic load on the environment. Wheat straw AQ-soda pulp was treated with acid (A) to reduce its metal contents followed by oxygen (O) delignification. Delignified pulp was then subjected to enzymatic (X) treatment with xylanase prior to bleaching to increase the effectiveness of successive bleaching with hydrogen peroxide (P). Handsheets were prepared from the treated pulp after each experimental trial to study its various optical, physical and chemical properties. Brightness of bleached pulp was improved up to ISO 73% with AOXP1P2 bleaching sequence. The improved brightness up to ISO 76% was achieved when alkali extraction stage was incorporated before bleaching with hydrogen peroxide (AOXEP1P2). TDS, COD and BOD5 of effluent samples during different experimental stages was monitored and compared with NEQS. It was evident from the results that enzymatic treatment not only helped to reduce the effluent load but also reduced the consumption of bleaching chemicals to achieve good brightness values.

Although highly efficient, conventional chemical bleaching is criticized for its high cost and environmental impact. In contrast, enzyme bleaching offers a sustainable and eco-friendly alternative, especially in elemental chlorine-free (ECF) and total chlorine-free (TCF) processes. This study investigates the synergy of laccase, xylanase, and mannanase in the ECF bleaching of softwood kraft pulp, focusing on their effects on fiber morphology and bleaching performance. The results demonstrate that laccase effectively oxidizes lignin, enhancing pulp brightness, while xylanase and mannanase improve bleaching efficiency by breaking down hemicellulose. The addition of mannanase during the enzymatic treatment increased the pulp brightness by 1.58 %ISO, with almost no negative impact on physical properties. The synergistic effect of the three enzymes increased the pulp brightness by 5.37 %ISO, reaching a maximum brightness of 92.35 %ISO. Furthermore, mannanase treatment significantly reduces the consumption of chemicals, cutting laccase and violuric acid usage by 38 % or decreasing total chlorine dioxide use by 13.26 %, while maintaining the same brightness level. These findings highlight the potential of using laccase, xylanase, and mannanase for efficient and eco-friendly pulp bleaching, contributing to resource conservation and environmental benefits. This study provides valuable insights into the industrial application of enzyme-based bleaching for sustainable paper production.