Two-phase systems for the recovery of lignin from deep eutectic solvents

Abstract

Lignocellulosic biomass is the raw material for producing several biomaterials, being widely used in pulp and paper industries, for which the delignification stage, that is, the removal of lignin, is necessary for paper production. However, this process is carried out with solvents that are usually harmful to the environment. Due to the crescent concern about environmental issues, research has been conducted to find solvents capable of performing this biomass delignification process sustainably. In this context, Deep Eutectic Solvents (DESs) have emerged as a promising alternative due to their attractive properties, such as high solvation capacity, low vapor pressure and flammability, and low production cost. In recent years, some DESs have been successfully explored in the extraction and delignification of biomass; however, their application at an industrial level is still limited due to issues related to the recycling and recovery of lignin from these solvents. A recently proposed solution for the fractionation of lignin from DES consists of applying two-phase systems composed of water and organic co-solvents, in which the aqueous phase solubilizes the DES, while the lignin is concentrated in the organic phase. Whithin this framework, this project aims to evaluate different biphasic solvent systems to separate lignin from DES recovered from biomass delignification, by determining liquid-liquid equilibrium (LLE) data for the DES+water+cosolvent mixtures. In addition, Kraft lignin partitioning studies will be carried out in these systems. The results obtained in this work will provide insights on the selection of viable alternative solvent systems for separating lignin from promising eutectic solvents for the delignification process. Finally, recovered lignin samples will be characterized using techniques such as NMR, GPC, and FT-IR, and applications of these lignin fractions will be proposed.