Fractionation of soda pulp lignin in aqueous solvent through membrane-assisted ultrafiltration

An industrial wheat-straw lignin was fractionated by a multistep process involving a microfiltration followed by two membrane-assisted ultrafiltration steps starting from an aqueous-solvent solution. The parent lignin and the different fractions were fully characterized in terms of chemical composition and physico-chemical properties by gel permeation chromatography, gas chromatography-mass spectrometry, high-performance liquid chromatography, thermogravimetric analysis, differential scanning calorimetry analysis and Fourier-transform infrared spectroscopy. The results show that the proposed process allows to selectively control the molar mass distribution of the fractions and the related dependent properties. This strategy offers a better understanding of the structural complexity of soda pulp raw lignin and emerges as an essential tool for lignin valorization in the context of material science and preparative organic chemistry.