Production of carboxymethylated lignin and its application as a dispersant

Kraft lignin is currently combusted in the pulping process to produce heat. It can be extracted from the process and converted to value-added products, but its limited water solubility hampers its end use applications. The main objective of this study was to investigate the carboxymethylation of hardwood kraft lignin to produce an anionic water soluble product. The results showed that the optimal conditions for carboxymethylation were 1.5 M NaOH concentration, 3 mol/mol sodium chloroacetate (SCA)/lignin ratio, 40 °C, 4 h and 16.7 g/L lignin concentration. The produced lignin had a charge density and carboxylate group of 1.8 meq/g and 1.68 mmol/g, respectively. The carboxymethylated lignin was further characterized using thermogravimetric analyzer (TGA), Fourier Transform Infrared (FTIR) spectrophotometer, Nuclear magnetic resonance spectroscopy (H NMR) and elemental analyses. Moreover, the application of carboxymethylated lignin as a dispersant for a clay suspension was successfully analyzed by means of a photometric dispersion analyzer.