Fractional separation and physico-chemical analysis of lignins from the black liquor of oil palm trunk fibre pulping

A continuing study of the lignin fractions, separated by a two step precipi tation method instead of the traditional one step precipitation method from the black liquor of oil palm trunk fibre pulping (OPTFP), was carried out. The degraded lignins were isolated from the supernatants of the OPTFP blac k liquor at pH 2.0 after separation of the polysaccharide degradation produ cts at pH 7.0, 5.5, 5.0, 3.5, and 2.0 in 3 vols 95% ethanol, respectively. A very high recovery of lignin fraction (93.6%) that was relatively free of non-lignin matter was obtained by precipitation at pH 7. The physico-chemi cal properties and structural features of the isolated lignin fractions wer e characterized by UV, FT-IR, and C-13-NMR spectroscopies as well as GPC, a nd the results are reported. (C) 2001 Elsevier Science B.V. All rights rese rved.