Lignin dissolution in dialkylimidazolium-based ionic liquid-water mixtures.
The solubility of lignin from bagasse in a 1,4-butanediol/water mixed solution was investigated and explained by the solubility parameter (δvalue). To explore the lignin solubility, enzymatic hydrolysis/mild acidolysis lignin (EMAL) isolated from bagasse was used as the starting material to prepare lignin solution by ultrasonic treatment. The lignin content in solution was determined by UV-vis spectroscopy at a wavelength of 280 nm. The results showed that 240 minutes of ultrasonic treatment was needed to achieve lignin dissolution equilibrium in the 1,4butanediol/water mixture. Maximum lignin solubility (14.6 g/L) occurred at a concentration of 80% (v/v). The δ-value of lignin (14.0 (cal/cm)) was calculated based on the atomic and functional groups present in the phenylpropane unit. The δ-values of the 1,4-butanediol/water showed a decrease from 22.31 to 11.09 (cal/cm) as the concentration of 1,4butanediol increased. The maximum lignin solubility predicted by the δvalue should occur at a concentration of 80% (v/v), which agreed with the experimental result.