Lignin extraction and isolation methods

Lignocellulosic biomass is described as a three-dimensional polymeric composite material synthesized by plants. It consists mainly of structural components along with other minor nonstructural compounds. The structural compounds are formed by three biopolymers: cellulose, hemicelluloses, and lignin. The lignocellulosic biomass has been known as an energy resource since ancient times by its direct combustion. More recently, the lignocellulosic materials have been used primarily in the chemical industry, furniture industry, and construction due to their abundance, ubiquity, and availability. Finally, in the last decades, lignocellulosic biomass has aroused as a promising alternative to petrochemical fossil resources for the conversion of biomass into energy, biofuels, chemicals, and new materials, which can be applied in many fields such as biomedical applications. Among the structural compounds, cellulose and hemicelluloses are very well-known polysaccharides, which can be used for many different applications in a variety of areas. However, lignin, which is mostly generated as a byproduct in the pulp and paper industry, is mainly burned in industrial boilers, underestimating its enormous potential. The main reason of this limited use of lignin is its high dispersity; difference in type and amount of functional groups, and thermal properties, which vary in accordance with the lignins' origin and isolation process. Therefore, it is very important to establish different extraction and isolation methods along with its downstream valorization pathways for the production of different bulk chemicals, which can be used in a variety of industries especially in the biomedical field.