Investigation on the effect of acetylation and reduction treatments on the chromophore groups of isolated lignin from unbleached hardwoods chemimecanical pulp using FT-IR spectroscopy

This study lignin from unbleached hardwoods chemimechanical pulp was extracted and the chromophor functional groups of the lignin were studied. Acetylation and reduction treatments were perfomed and samples were analyzed by FT-IR spectroscopy. A mild acidic dioxin extraction method was employed to isolate lignin. For the acetylation and reduction treatments of lignin acetic acid and sodium borohydride were used respectively. The results of untreated and treated (acetylated and reduced) lignin spectra showed that، the major of lignin chromophor groups such as hydroxyl and carbonyl groups have been reduced or eliminated by these treatments. In the acetylated lignin، the absorption band of hydroxyl groups has been weakened and in the 1743. 16 Cm-1 region، acetoxy compounds band has appeared and also a cluster absorption band was observed in the 1228. 76 Cm-1 region. In the reduced lignin، most of the absorption bands of the carbonyl groups have been weakened or eliminated، especially in the 1705. 56 and 1629. 54 Cm-1 region.