Deep eutectic solvent-enabled lignocellulosic biomass valorization: Toward understanding of biomass pretreatment,...

A comprehensive study was conducted to determine the effects of water and ethylene glycol (EG) on biomass pretreatment using a binary deep eutectic solvent (DES) containing choline chloride and acetic acid (1ChCl3AC) at a mole ratio of 1:3. Different quantities of water and EG were combined with 1ChCl3AC to pretreat wheat straw, miscanthus, eucalyptus, and sorghum stalk at 130 °C for 6 h. The changes in nanopore structure and surface roughness of wet biomass, as well as biomass crystallinity after 1ChCl3AC-based pretreatment were investigated using XRD and small-angle neutron scattering (SANS). Adding a certain amount of water or EG did not reduce the delignification ratio or saccharification rate. Furthermore, SANS was used to explore the interactions between lignin, 1ChCl3AC, and water. The study found that lignin molecules produced various nanostructures through hydrogen bond, π-π, and hydrophobic interactions in 1ChCl3AC and its aqueous solutions. Following pretreatment, lignins were extracted and fractionated with three organic solvents to minimize structural heterogeneity. A collection of lignin antioxidants with varying activities was obtained, and antioxidant activity assessments revealed three distinct interactions amongst binary lignin combinations. The findings of this study add to our understanding of the interplay of 1ChCl3AC, water, EG, and lignin.