Sequential Extraction of Lignin from Sugarcane Bagasse: Characterization and Application in the Pb(II) Adsorption

Abstract

Lignin was extracted from bagasse by sequential extraction method. The crude lignin was divided into three fractions by molecular weight and chemical functionality (Lignin fractions L1 and L2 were recovered with diethyl ether and methanol solubility respectively, with the L3 part remaining), and the properties of each were analyzed before being applied to Pb(II) adsorption. The results indicated that the L2 fraction has the largest molecular weight due to self-condensation. The weight of the aliphatic hydroxyl group of L2 is 4.63 times of L1 and 1.65 times of crude lignin. Scanning electron microscopy (SEM) images and Brunauer-Emmett-Teller (BET) analysis show that the surface of L2 and L3 are porous with surface areas of 2.8304 m2/g and 10.7530 m2/g, respectively. The characteristics of structure and morphology for the L2 and L3 fractions display better adsorption property than crude lignin and L1 fractions, with adsorption capacities of approximately 6.46 mg/g and 7.56 mg/g. This research confirmed that each lignin fraction possessed different chemical and physical characteristics, and the L2 fraction has good solubility and adsorption properties, which provide the basis for lignin modification applied to lead Pb(II) adsorption.