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 precipitation 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 black liquor at pH 2.0 after separation of the polysaccharide degradation products 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-chemical properties and structural features of the isolated lignin fractions were characterized by UV, FT-IR, and 13C-NMR spectroscopies as well as GPC, and the results are reported.