Physicochemical Properties of Soda and Kraft Lignin Extracted from Gmelina arborea Wood

Lignin, an amorphous biopolymer is one of the major components of wood. In this study, lignin was extracted from Gmelina arborea wood using Soda and Kraft pulping processes. The lignin was characterized using Fourier Transformed Infrared Spectrometer (FTIR), UV/visible spectrometer, electrospray ionization mass spectrometer and scanning electron microscope (SEM). Results revealed that G. arborea wood lignins contained several chemical functional groups. Kraft lignin (KL) contain carboxyl and thiol group in addition to other functional groups such as methoxyl, alcohols and phenolic. UV/ visible spectroscopy results revealed that Soda lignin (SL) absorbed at higher wavelength than Kraft lignin. The concentrations of both conjugated and non-conjugated phenolic group were higher in Kraft lignin than Soda lignin. ESI-MS spectra revealed that the composition of the monomers was higher in Kraft lignin while dimers composition was higher in Soda lignin. The surface morphology of both lignins were heterogeneous with uneven particle size. These physicochemical properties of lignin will enhance their applications as adsorbents, corrosion inhibitors and in the production of some industrial chemical intermediates.