Preparation and characterization of biobased microspheres from lignin sources

Lignin microspheres of uniform spherical shape and narrow size distribution were successfully prepared from a number of different lignins using emulsion solvent evaporation (ESE) technique. Four lignins were examined in this study include; lignin isolated from non-wood/hardwood biorefinery residue (L1), isolated lignin from hardwood kraft black liquor (L2), technical kraft softwood lignin (L3) and technical soda non-wood lignin (L4). Lignin microspheres were prepared from acetyl derivatized lignin and from a solubilized lignin fraction. Dynamic light scattering (DLS) was used to determine particle diameter, size distribution and polydispersity of lignin microspheres. Scanning electron microscopy (SEM) was used to determine morphology of the lignin microspheres. Uniform lignin acetate microspheres were successfully produced from the four lignins in a size range of 1280–1349 nm in dichloromethane and 1313–2545 nm in ethyl acetate. The ethyl acetate soluble fraction of L2 and L4 was formed into spherical shape with the size of 1152 nm and 875 nm, respectively.