| Abstract:
In this research, two types of lignin, i. e. one extracted from industrial waste water of kraft paper producing factory as black liquor and another provided from Aldrich company, were studied. First, the lignin was precipitated from its black liquor by a dilute acid and was then purified by dissolving in tetrahydrofuran (THF). Lignin samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopies. The results revealed that the Aldrich lignin has a structure similar with the lignosulfonate while lignin extracted from black liquor does not have a hydrophilic sulfonate group and has a Kraft lignin structure. Using acetylation of Kraft lignin and complementary characterization with 1HNMR spectroscopy, the ratio of hydroxyl functional groups to methoxy groups was calculated to be 1. 11 to 1, and the amount of the hydroxyl groups was calculated to be 5. 91 mmol/g of acetylated lignin, where 53% of the hydroxyl groups is related to the aromatic hydroxyl groups. Molecular weight of the Kraft lignin which was determined from the gel permeation chromatography (GPC) analysis of the acetylated Kraft lignin was 1260 g/mol, average number of the hydroxyl groups per acetylated lignin chain was calculated to be 7. 44.
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