Morphological changes of lignin during separation of wheat straw components by the hydrothermal-ethanol method. (December 2019)

• Record Type: Journal Article
• Authors: Li, Jinbao; Feng, Pan; Xiu, Huijuan; Li, Jingyu; Yang, Xue; Ma, Feiyan; Li, Xiang; Zhang, Xuefei; Kozliak, Evguenii; Ji, Yun
• Is Part Of: Bioresource technology. Volume 294(2019)
• Publication Date: 2019-12
• Subjects: Wheat straw -- Biomass component separation -- Hydrothermal treatment -- Ethanol extraction -- Lignin; Biomass -- Periodicals; Biomass energy -- Periodicals; Bioremediation -- Periodicals; Agricultural wastes -- Periodicals; Factory and trade waste -- Periodicals; Organic wastes -- Periodicals; Bioénergie -- Périodiques; Déchets agricoles -- Périodiques; Déchets industriels -- Périodiques; Déchets organiques -- Périodiques; Déchets (Combustible) -- Périodiques; 662.88
• DOI: 10.1016/j.biortech.2019.122157
• Languages: English
• ISSNs: 0960-8524

Abstract

Highlights: Most of hemicellulose separation in hydrothermal-ethanol process occurs on the first step. Hydrothermal treatment inhibits the subsequent lignin extraction by ethanol. Insoluble lignin deposits on the fiber surface during hydrothermal treatment. Subsequent heating with ethanol induces deposited lignin to form a coating layer. Abstract: The separation efficiencies of wheat straw components by hydrothermal treatment and ethanol extraction have been compared. The results showed that the lignin removal rate by two-step hydrothermal-ethanol method was significantly lower than that of single-step ethanol extraction. Microscopic and adsorption studies (using SEM/AFM, XPS and pore structure analysis) showed that during the hydrothermal treatment a large lignin fraction migrated from the intercellular layer and cell wall and deposited on the fiber surface. Furthermore, the deposited lignin then spread on the fiber surface to form a lignin coating layer, which prevented its dissolution in ethanol. Without prior heating, i.e., upon a single step ethanol extraction, the massive lignin deposition was avoided, presumably due to its efficient dissolution hindering its tight binding with carbohydrate polymers on the fiber surface. Therefore, the lignin removal efficiency was drastically reduced as a result of hydrothermal treatment compared to ethanol extraction.