Abstract:

Objective: This study explored the bleaching effect and influence of the second-generation biological complex enzyme on tung wood, and provided theoretical basis and scientific basis for the decolorization and biological improvement of tung wood and the development of tung wood pulping. Method: Paulownia elongata was used as the experimental material, and the cellulose second-generation enzyme (CTEC2) was used for pretreatment. The changes of color difference index and chemical components of samples before and after pretreatment were analyzed by controlling pretreatment time(60, 75, 90, 105 min), temperature(30, 50, 70 ℃) and pH value(3, 5, 7), The thermal degradation properties of the samples were analyzed by TGA(thermo gravimetric analysis), the changes of microstructure were investigated by SEM(scanning electron microscope), and the changes of crystallinity after pretreatment bleaching were measured by XRD(X-ray diffraction). Result: 1) Color determination: when the pretreatment conditions were pretreatment temperature 50 °C, pH value 7 and pretreatment time 105 min, the bleaching effect of paulownia wood was the best, and the brightness and whiteness were improved, and the bleaching effect will also be improved with the extension of pretreatment time. 2) Component determination showed that CTEC2 had the best pretreatment effect on Paulownia wood at 50 °C and pH 7. The relative content of cellulose increased by 10.76%, hemicellulose content decreased by 11.13%, acid-soluble lignin content decreased by 3.05%, acid-insoluble lignin content decreased by 4.22%, and extract content decreased by 1.15%. 3) From the TGA curve, the temperature corresponding to the maximum mass loss rate of pretreated paulownia wood increased, and the thermal stability increased. It can be seen from the SEM images that the pretreatment can effectively destroy the lignocellulose structure. XRD showed that the crystallinity of pretreated paulownia wood cellulose increased. Conclusion: CTEC2 can change the main chemical components of paulownia wood, reduce the content of lignin, hemicellulose and extract, so as to achieve bleaching and decolorization effect. The optimum conditions for bleaching pretreatment of paulownia wood were temperature 50 °C, pH 7 and pretreatment time 105 min.

Key words: paulownia, pretreatment, cellulose second-generation enzyme(CTEC2), bleaching and decolorization, thermo gravimetric analysis(TGA)