A LignoboostTM-lignin was fractionated by solvent fractionation using water-acetone mixtures. The fractions were characterized by chromatographic and spectroscopic methods. The solvent mixtures varied from 80/20 to 70/30 percent by volume (water/acetone). The solution series was carried out in order of dercreasing water content of the mixture. Fractions shows very different chemical characteristic, especially in molecular weight distribution, functional groups and bonding types. Fractions from water rich mixtures show high contents of monomers. Accordingly, comparatively few bond types are observed in the 2D HSQC NMR spectrum. Additional signals from resinol type, which arise from β-β and α-O-γ bonds, are obtained for fractions of 40 and 50 percent by volume acetone. Water poor fractions contains the highest variety of bond types. Furthermore, different signals of LCCs are detected. Only three fractions are suitable for hydrogel formation. The free swelling capacity (FSC) of gels depends on the average molecular weight of the lignin as well as the content of monomers. Hence, the microscopic structures of the gels differs greatly and range from hyphen like to compact solids with structured surfaces. For copper sorption, too, significant differences were observed. The highest sorption capacity shows the fraction with the porous structure.

Influence of a fractionation of LignoboostTM lignin on lignin structure and sorption properties for copper(II) ions

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