Solvent fractionation of softwood and hardwood kraft lignins for more efficient uses: Compositional, structural, thermal, antioxidant and adsorption properties

Abstract

This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating values, and thermal and adsorption properties of industrial hardwood and softwood kraft lignins. The aim of the research was to develop a simple approach for obtaining lignin fractions with tailored properties for applications in certain materials. Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations, were found to be efficient for separating spruce and eucalyptus kraft lignins into fractions with low polydispersities. The ethanol fraction of spruce and the ethyl acetate fraction of eucalyptus afforded the highest yields. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material was characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and P-31 NMR spectro-scopy. The thermal properties of the lignin samples were studied using thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) was obtained through the direct measurement of weight changes in each experimental curve, and the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The adsorption properties of fractionated kraft lignins were studied using methylene blue dye. The correlations observed between molecular weight, composition and functionality and the thermal, radical scavenging and adsorption properties of the lignin fractions provides useful information for selecting the appropriate solvent combinations for specific applications of lignin raw materials (including their use as antioxidants, biofuels or sorbents in water treatment processes).

Keywords

Kraft lignin; Solvent fractionation; Structural analysis; Antioxidant activity; Thermal stability; Adsorption

Published in

Industrial Crops and Products
2019, Volume: 129, pages: 123-134
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Moriana, Rosana

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    
  • Royal Institute of Technology (KTH)
  • University of Skövde

UKÄ Subject classification

Wood Science


Publication identifier

DOI: https://doi.org/10.1016/j.indcrop.2018.11.067

Permanent link to this page (URI)

https://res.slu.se/id/publ/98452