Microwave-assisted diol DES system enables efficient biomass fractionation and lignin grafting stabilization from peanut shells via a lignin-first strategy.

Abstract

Lignocellulosic biomass represents a promising renewable resource, but its valorization is often hindered by irreversible lignin condensation during conventional pretreatment processes. This study developed a novel microwave-assisted diol-based deep eutectic solvent (DES) system (ChCl/diol/AlCl₃·6H₂O) to achieve integrated fractionation of peanut shells while preserving the lignin structure. Under mild conditions (120 °C, 30 min), the system enabled near-complete removal of hemicellulose (91.17 %) and lignin (86.39 %), yielding cellulose-rich solids with enhanced enzymatic digestibility (glucose: 92.64 %, xylose: 94.56 %). Importantly, diol achieved α-etherification grafting of lignin, thereby inhibiting lignin condensation. The grafted lignin retained an intact structure with a high β-O-4 content (39.29 per 100 Ar) and retention rate (84.19 %). The DES exhibited excellent recyclability and 73.04 % total biomass valorization. This work provides a sustainable approach for integrated lignocellulose biorefining.