Insights into the mechanism of lignin dissolution via deep eutectic solvents by using Hansen solubility theory

The lignin solubility parameters were analyzed and compared with those of 5 Deep Eutectic Solvents（DESs） and 11 commonly used solvents. The dissolution effect of DESs on lignin was better than that of common solvents. The mechanism of DESs for dissolving lignin was analyzed with Hansen solubility theory, and the findings showed that dispersion, polarity, and hydrogen bonding forces had an important influence on the dissolution of lignin. Hydrogen bonding force was the most dominant among the three, followed by dispersion force. The high strength of hydrogen bonding force and the similarity of the solubility parameters of the three forces to that of lignin are the key to determining the solubility properties of solvents for lignin, and DESs meet this requirement.