Production of carboxymethylated lignin and its potential use in electrochemistry

Lignin, despite the complexity of its structure, has considerable potential for application in new high-value-added products. However, its use is still limited to energy production, especially in the pulp and paper sector, which results in large amounts of lignin as an industrial residue worldwide. Various methodologies for chemical modifications have been studied to improve its compatibility with polymer matrices, its water solubility, and some physicochemical properties. In this context, the main objective of this study was to characterize and optimize the carboxymethylation reaction of kraft lignin, as well as to propose the minimal formula for the lignins studied here. FTIR and NMR results showed the effectiveness of the reaction, and the new conditions presented a yield of 60%. The produced lignin was an anionic water-soluble lignin with a higher thermal resistance (TGA) and high zeta potential, which influences the wettability of the metallic surface and the quality of electrode coatings, favoring its potential use in new applications, especially in electrochemistry.