Chemical treatment of Bagasse by oxalic acid-choline chloride and lactic acid-choline chloride deep eutectic solvents

Bagasse carbohydrates, which are mainly consist of cellulose and hemicelluloses, are important raw materials in chemical industries; because they can be easily prepared from biomass in large scale, their application is simplified in large scale. Derivation and purification of biomass chemicals are difficult, costly and require the use of complex methods with environmentally dangerous chemicals and solvents. Therefore, researchers are looking for simpler, cheaper, safer and environmentally friendly compounds and processes. The use of deep eutectic solvents has been reported as one of these methods in biomass processing. In this study, the use of new oxalic acid-choline chloride and lactic acid-choline chloride deep eutectic solvents for bagasse treatment was investigated. Results indicated that these new solvents were effective in the solubilization and extraction of short-chain and amorphous carbohydrates, especially hemicelluloses; as the final processing yields were respectively reduced to about 50 and 59%, and the main part of degradation belonged to the hemicelluloses. Cellulose to holocellulose ratio was increased in all treatments to about 90%. The lactic acid-choline chloride solvent was effective in lignin solvation, as the lignin content was reduced to 6.2%, while oxalic acid-choline chloride solvent did not have an ideal efficiency toward lignin removal, and the least amount of lignin in treated product was about 11%. Also, the viscosity drop of cellulosic pulp in lactic acid-choline chloride solvent-treatment was much less compared to oxalic acid-choline chloride solvent-treatment, as the cellulosic pulp viscosity for these treatments were 11.1 and 4.3 cp., respectively.