Production of carboxymethylated lignin from industrial black liquor

In the search for innovations, lignin has become an ideal candidate for application in new products with high added value, due to its aromatic structure, its natural abundance and its wide functionalization. It is considered the second largest constituent of available biomass, comprising about 10-30% of the total biomass, demonstrating its high availability and establishing its importance for new applications (CURMI et. al., 2021; SHINGANIA et. al., 2021). According to Zhou et. al. (2022), the valorization of lignin is essential to maximize the use of biomass and reduce waste generation. Kraft lignin has been recognized as a potential raw material for new products with high added value, mainly with the adoption of new techniques that improve the characteristics of the material, such as chemical modifications of carboxymethylation, in which alkaline lignin becomes soluble in water. (KONDURI et al., 2015). This work was effectively transformed into CML-Na, with a yield of 60% in its total production. The characterizations showed that there was a lignin carboxymethylation reaction, which can be observed through the differences found in the infrared spectra and in the TGA curves. The results prove the feasibility of using kraft lignin for the development of chemical modification, in search of new products with high added value and sustainability.