Current perspectives on the applicability of lignin material in the biosorption process

Generally, cheap and environmentally friendly biosorbent materials attract the attention of researchers and become the focus of research. Cellulose (C₅H₁₀O₅) and hemicellulose (C₅H₁₀O₅) come to the fore among biosorbent materials in biosorption processes. However, lignin is also a very abundant and underutilized biopolymer resource that can be preferred for biosorbent production. Lignin (C₁₈H₁₃N₃Na₂O₈S₂) is an amorphous phenolic biopolymer with a structurally three-dimensional branched network structure. Three major cinnamyl alcohol (p-coumaryl alcohol, sinapyl alcohol, and coniferyl alcohol) monomers combine to form the lignin matrix. This biopolymer has advantages such as being available in large quantities, high selectivity and sorption capacity. However, one of the biggest disadvantages is that lignin exhibits a heterogeneous structure for the balanced production of biosorbents. The structural behavior of lignin depends largely on the source and the process conditions from which it is isolated. Today, although the use of lignin-based biosorbents is increasing, only 5% of the available lignin globally is used. Therefore, there are still significant opportunities for the development and evaluation of this material in various fields (water/wastewater treatment, industrial sectors, medicine and cosmetics, etc.). This review summarizes the world's current trends, perspectives, and recent developments in lignin-based biosorbents in terms of all properties of lignin.