SYNERGETIC EFFECT OF ALKALINE EXTRACTION AND XYLANASE TREATMENT ON CHLORINE DIOXIDE BLEACHING OF WHEAT STRAW PULP

摘要

Enhanced chlorine dioxide bleaching of wheat straw pulp by synergetic effect of alkaline extract and xylanase treatment (X) was investigated. The results demonstrated that the efficiency of ClO2 delignification (D) with single xylanase pretreatment was not improved significantly. Using the XDP and DXP bleaching sequences, the aided-bleaching effect of xylanase was limited and the final brightness was increased only by 1.5 points. However, xylanase treated pulp reduced the consumption of H2O2 by 25% to 33.3% in subsequent H2O2 (P) bleaching stage. By combining peroxide-reinforced extraction (EP) and xylanase treatment with the XDEPP and DXEPP bleaching sequences, the final brightness was enhanced up to 5.4 points over controls. With the same sequences, xylanase treated pulp reduced the charge of ClO2 by 17% to 20%, equivalent to savings of 2kg ClO2 t-1 pulp, while still maintaining a comparative final brightness. The analysis of UV-Vis spectroscopy of chromophores released from xylanase-treated pulps showed a characteristic peak at 280 nm, indicating the presence of lignin or lignin-derived compounds in the released coloring matter.