Dissolution and degradation of cellulosic fiber in carboxylic acid choline chloride-based deep eutectic solvents

In this study, bleached chemical pulp from hardwood was treated with different carboxylic acid choline chloride-based deep eutectic solvents (CA/ChCl DESs) including formic acid, acetic acid, ethanedioic acid, propanedioic acid and choline chloride. The dissolution and degradation of cellulose and hemicellulose in chemical pulps in these DESs were analyzed, while the relationships between the polarity parameters of DESs and the degradation and dissolution of cellulosic fibers were discussed. The results show that dicarboxylic acids/ChCl were more conducive to the solubility and degradation of cellulosic fibers compared to monocarboxylic acids/ChCl at a higher temperature. In addition, the increase in alkyl of the CA could reduce the solubility to cellulosic fiber. The further study reveals that the dissolution and degradation of cellulosic fibers are generally governed both by temperature and the ability of DESs hydrogen bond acidity (alpha), while temperature shows little effect on alpha. However, no remarkable relationships were found between the DESs hydrogen bond basicity (beta) and cellulose degradation and dissolution.