Effects of D-hot pretreatment on micro-distribution of residual lignin in sugarcane bagasse pulp and fiber properties

Abstract

Pretreatment of sugarcane bagasse pulp by hot chlorine dioxide has been performed to study delignification and structural changes in lignocelluloses. The compositions of the products were measured by gas chromatography mass spectrometry. The structure and morphology of the D-hot pretreated sugarcane bagasse pulps were characterized by FTIR, scanning electron microscope, X-ray diffraction, Metso Kajaani FS300 fiber analyzer and optical analyzer. Temperature played a crucial role in the lignin depolymerization and hemicellulose hydrolysis. The results show that the lignin content was reduced by 28.39% in the P layer and 20.93% in the S layer with increasing temperature from 60 to 95 °C. The resulting compositions of D-hot stage effluent were mainly including oxidized lignin and derivatives of furfural. Compared with the control, the category of oxidized lignin can be increased with D-hot pretreatment. Also, pretreated bagasse pulp has high brightness of 59.71% ISO, crystallinity index of 70.84%, L/W of 50.84 and outstanding optical properties. Therefore, bleached bagasse pulps might have the opportunities for further application in paper and paper-based materials. The graphical abstract showed that the changes of the crystallinity index (CrI), the brightness, and the L/W of the SCB pulp fibers with increasing reaction temperature from 60 to 95 °C. Also showed that the cross section of the single fiber and the region of P and S layer. EDS images of P and S layers for the unbleached SCB pulp, control pulp and D-hot bleached SCB pulps, the peaks corresponding to elemental carbon and oxygen were shown for the samples. In EDS, oxygen/carbon atom ratios and lignin mass in P and S layer of the unbleached pulp and bleached pulps were determined. The degradation products of lignin (1)–(3) in the control and degradation products (2)–(15) in the D-hot effluent were identified.