Mechanisms and mass‐transfer kinetics of hemicellulose and lignin dissolution during deep eutectic solvent pretreatment

Abstract Deep eutectic solvents (DESs) are promising green solvents in lignocellulose pretreatment, as they combine low toxicity, biodegradability, and efficient ability to remove hemicellulose and lignin. However, under‐ or over‐removal of hemicellulose and lignin can hinder cellulose exposure or produce inhibitors (e.g., pseudo‐lignin or condensed lignin), reducing enzymatic hydrolysis efficiency. Here, a mass‐transfer kinetic model incorporating the pH and viscosity characteristics of DESs was developed to precisely regulate hemicellulose and lignin dissolution. The model revealed that the activation energy required for the solubilization of hemicellulose and lignin into DESs is 16.41 and 21.40 kJ/mol, respectively, which is significantly higher than that required for diffusion into the boundary layer (4.58 and 4.61 kJ/mol), indicating that solubilization is the rate‐determining step. Theoretical calculations revealed that, compared with lignin, hemicellulose exhibits greater advantages in terms of interaction energy, diffusion coefficient, and number of hydrogen bonds with DESs, making it inherently more soluble and diffusible.