Ternary Deep Eutectic Solvent (T-CuCl2-EG) for Lignin Removal from Corn straw

To address the challenge of lignin removal while preserving cellulose in lignocellulosic biomass valorization, this study developed a novel ternary deep eutectic solvent (DES) system composed of triethylbenzyl ammonium chloride (T, as hydrogen bond acceptor), copper chloride (Lewis acid catalyst), and ethylene glycol (EG, hydrogen bond donor) for microwave-assisted pretreatment of corn straw. The DES was designed to leverage synergistic effects between Lewis acid catalysis and hydrogen bond disruption for selective lignin extraction. Optimization via Box-Behnken experimental design revealed that optimal delignification (96.52%) and hemicellulose removal (94.60%) with 94.79% cellulose retention were achieved under microwave conditions of 130°C, 40   min, liquid-solid ratio 13.1, and CuCl₂/T molar ratio 0.198. Comparative characterization of raw and pretreated biomass using SEM, FT-IR, and XRD demonstrated that T-CuCl₂-EG disrupted the lignocellulose matrix by breaking ether/ester bonds in lignin-carbohydrate complexes, selectively solubilizing lignin/hemicellulose while preserving cellulose crystallinity. This work provides a sustainable and efficient strategy for biomass fractionation, with potential applications in biorefineries.