Utilization of inorganic salts as adjuvants for ionic liquid-water pretreatment of lignocellulosic biomass: enzymatic hydrolysis and ionic liquid recycle.

Pretreatment of lignocellulosic biomass with ionic liquids (ILs) for the large-scale biorefinery remains challenging due to its high price. This study focused on the utilization of inorganic salts as adjuvants for ionic liquid-water pretreatment to improve the tolerance to water and the reusability of the ILs. After the pretreatment of rice straw by the mixture of 40% 1-ethyl-3-methylimidazolium chloride ([C2mim]Cl) + 53% water + 7% K2CO3 at 110 °C for 1 h, the residues became highly susceptible to enzymatic hydrolysis; 93.70% of lignin was removed, and 92.07% sugar yield was achieved. [C2mim]Cl-K2CO3 aqueous biphasic system was formed at room temperature when K2CO3 concentration increased to more than 30%, and the [C2mim]Cl recovery of 94.32% was achieved. The results indicate that the addition of inorganic salts to IL aqueous solutions can significantly reduce the cost of IL pretreatment, while maintaining an efficient enzymatic hydrolysis of lignocellulosic biomass.