Green and sustainable production of high-purity lignin microparticles with well-preserved substructure and enhanced anti-UV/oxidant activity using peroxide-promoted alkaline deep eutectic solvent

Deep eutectic solvents (DESs) have emerged as promising and eco-friendly solvents for the efficient extraction of lignin from biomass due to their low cost and environmental benefits. Nevertheless, the prevalent use of acidic DESs in lignin extraction often results in excessive depolymerization and recondensation of lignin, thereby impeding its downstream applications. In this study, we developed a range of alkaline DESs (ADESs), both pure and peroxide-containing, for the extraction of high-quality lignin from bamboo. Moreover, carbon dioxide (CO2) was employed for the precipitation and regeneration of the extracted lignin. The obtained lignin fractions were comprehensively characterized in terms of yield, purity, morphology, solubility, structural features, and anti-UV/ oxidant activity. The results showed that the monoethanolamine-based ADES demonstrated superior performance among the pure ADESs. Structural analysis confirmed the well-preserved substructures of lignin fractions obtained using ADESs, with beta-O-4 bond retention ranging from 49.8 % to 68.4 %. The incorporation of a suitable amount of peroxide improved lignin yield, morphology, solubility, and anti-UV/oxidant activity. Additionally, the anti-UV/oxidant activity of lignin exhibited a positive correlation with its phenolic hydroxyl content. This study provides a valuable reference for the green and sustainable production and valorization of lignin within the

Automated summary

Deep eutectic solvents (DESs) have been developed as eco-friendly solvents for extracting lignin from biomass. This study focused on the development of alkaline DESs (ADESs) for high-quality lignin extraction from bamboo. Pure ADESs and peroxide-containing ADESs were used, and carbon dioxide (CO2) was employed for precipitation and regeneration. The extracted lignin was characterized in terms of yield, purity, morphology, solubility, structure, and anti-UV/oxidant activity. It was found that the monoethanolamine-based ADES showed superior performance, and the addition of peroxide improved lignin yield and activity. The anti-UV/oxidant activity of lignin was positively correlated with its phenolic hydroxyl content.