Sustainable hierarchical extraction of lignin with simultaneous recovery of acidic deep eutectic solvent

Efficient biomass pretreatment is a crucial step for improving the conversion efficiency of lignocellulosic resources into bioenergy and bio-based products, while the sustainable management of solvent systems remains a major challenge. In this work, a novel and sustainable recovery strategy for deep eutectic solvents (DES) used in biomass fractionation was developed by integrating antisolvent precipitation with activated carbon adsorption. This approach enabled high-purity DES recovery while simultaneously facilitating the hierarchical utilization of lignin. Experimental results showed that, within an activated carbon mass ratio range of 1:80 to 1:40, the retention rates of all DES components exceeded 96%, ensuring stable solvent purity during recycling. The removal efficiencies of lignin and glucose reached 89.27% and 92.67%, respectively, leading to the isolation of high-purity water-insoluble lignin (WL) exhibiting a lignin content of 76.22%, and water-soluble lignin (ACL) enriched in sugars (24.01% glucose and 10.95% xylose). These lignin-rich and sugar-rich components represent promising feedstocks for downstream biomass conversion. Furthermore, the recovered DES maintained stable chemical structure and pulping performance over three reuse cycles, with screened pulp yields remaining at approximately 40% and negligible changes in fiber morphology. Overall, this work provides an efficient and sustainable solvent recovery strategy for biomass pretreatment, contributing to cost-effective and scalable biomass conversion production from lignocellulosic resources.