The Influence of Choline Chloride/Glycerol Molar Ratio in Deep Eutectic Solvent Pretreatment on the Physicochemical Properties of Recovered Corncob Biomass

Deep eutectic solvents (DESs) are considered promising green solvents for lignocellulosic processing due to their ability to form effective hydrogen-bonding networks, along with low toxicity, biodegradability, and reasonable cost. In this study, choline chloride/glycerol (ChCl/Gly) DES system was combined with hydrogen peroxide for corncob biomass fractionation and recovered biomass production. The effect of ChCl/Gly molar ratios (1:1, 1:3, and 1:5) on extraction efficiency and the physicochemical properties of the recovered solid biomass were systematically evaluated. The calculated results showed that the recovered biomass yield increased with increasing glycerol content, reaching a maximum of 68.06 ± 1.85% at a ratio of 1:5. The color parameters (L*, ΔE, and WI) indicated an improvement in whiteness, reflecting the effective removal of chromophoric compounds. FTIR analysis confirmed a significant reduction in hemicellulose and lignin, while XRD results showed that the cellulose I structure was preserved, with a crystallinity index of 39.90% at the 1:1 ratio. SEM and TGA further demonstrated that the recovered biomass exhibited higher purity and improved thermal stability compared to the raw material. These results demonstrate that the ChCl/Gly ratio directly affects the removal efficiency of amorphous components as well as the properties of the recovered biomass. The recovered biomass shows potential for applications in reinforcement materials and adsorption, while the DES-based process represents an effective and environmentally friendly approach for lignocellulosic biomass valorization.