Optimization of lignin extraction from bamboo by ultrasound-assisted organosolv pretreatment.

[Display omitted] • Lignin extraction from bamboo was optimized by ultrasound-assisted organosolv process. • Temperature was the most significant parameter affecting the lignin yield. • Maximum lignin yield of 65.81 ± 2.40% was obtained under sono-assisted pretreatment. • High purity lignin of 95.37 ± 1.17% was obtained from this pretreatment. For a sustainable biorefinery, reduction in the recalcitrance of lignocellulosic biomass is very crucial for the efficient utilization of each fraction. The present work investigated an integrated pretreatment method to recover high-quality lignin along with the cellulose-rich pulp. An optimization study employing response surface methodology investigated the synergistic effects of ultrasound and organosolv pretreatment from Bambusa tulda (bamboo). The optimal condition (180 °C, 55 min, and 30 min sonication) resulted in 65.81 ± 2.40% of lignin yield with 95.37 ± 1.17% purity. A reduction in 7.85% yield and 1.54% purity of lignin with organosolv pretreatment highlighted the efficacy of sonication in lignin extraction. Ultrasound resulted in homolytic cleavage of the lignin-carbohydrate bond that enhanced delignification and increase the cellulose crystallinity. NMR, FTIR, GPC, and TGA of lignin suggested the superiority of sonication in maintaining lignin quality. A significant amount of β-O-4 linkages in extracted lignin is favorable for its subsequent valorization. [ABSTRACT FROM AUTHOR]