Fractionation of Soda Pulp Lignin in Aqueous Solvent through Membrane-Assisted Ultrafiltration

An industrial wheat straw lignin was fractionated by a multistep process involving 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 physicochemical 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 us 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.