Contribution of Lignin from Different Bioresources to the Pollution Load

Abstract

Lignin was extracted from eucalyptus, Pinus koraiensis, and bagasse (representatives for hardwood, softwood, and Gramineae, respectively) black liquors to quantitatively distinguish the pollution loads caused by lignin. The results indicated that the actual common chemical oxygen demand (CODCr) of lignin was lower than the theoretical CODCr with an actual oxidative ratio of approximately 85%. The results also showed that 1 kg of lignin from eucalyptus, P. koraiensis, and bagasse could produce CODCr pollution loads of 1.476 kg, 1.540 kg, and 1.561 kg, respectively, which revealed the large contribution of lignin to the pollution load. Through the elemental analysis, infrared spectroscopy, and nuclear magnetic resonance analysis in the hydrogen and carbon spectra of the different lignin, it was found that guaiacyl structures in the lignin units can lead to a better thermal stability for P. koraiensis. Compared with the P. koraiensis and bagasse lignins, the eucalyptus lignin had a higher elemental oxygen content and lower molecular weight with mainly syringyl structures, which resulted in a higher reaction activity.