Alkaline deep eutectic solvent for separation and extraction of lignin from lignocellulose biomass

As a natural biopolymer, lignin from agroforestry waste has a wide range of applications in the preparation of bio-based materials and petrochemical alternatives. However, the application of lignin depends on the effective separation from biomass. In recent years, deep eutectic solvents (DESs) have been used in the separation and extraction of lignin due to their simplicity of synthesis and effective separation of lignocellulose. Although some studies have been devoted to the separation and depolymerization of lignin by acidic DESs, fewer reports have focused on the effect of alkaline DESs. In this paper, some investigations are reviewed on the pretreatment of biomass using alkaline DESs in recent years and recent research progress on the separation and extraction of biomass lignin from alkaline DESs are summarized in terms of the types and nature of alkaline DES solvents, and the various influencing factors in the treatment of biomass, etc. For the sake of environmental and economic benefits, the effective recycling of solvents is discussed. Furthermore, this paper reviews the application of lignin extracted by alkaline DES in the preparation of value-added products such as platform compounds and bio-based modified materials, we expect that our review may offer the route for future studies to address he effective extraction of lignin from agricultural and forestry wastes by alkaline DESs and promote the high-value use of lignin.