Synthesis and characterization of lignin nanoparticles isolated from oil palm empty fruit bunch and application in biocomposites

Abstract

Valorisation of industrial biomass wastes, such as oil palm empty fruit bunch (EFB) generated by the palm oil industry, could promote its sustainable use while minimising the adverse impacts on the environment. To this end, the present study attempted to synthesize lignin from EFB. A simple yet environmentally friendly technique, ultrasonication, has been employed to convert the isolated lignin to lignin nanoparticles (LNPs). The transmission electron microscopy results and dynamic light scattering measurements have confirmed the mean particle size of LNPs at 220 nm. Also, LNPs showed better thermal performance compared to lignin, as indicated by a higher glass transition and maximum degradation temperature. LNPs were stable in the pH range of 4.5 - 9.0 and sodium chloride concentration below 100 mM over a week of storage. At pH 7, the LNP suspension remains stable without precipitation for up to three months of storage under ambient conditions. In addition, the LNPs were incorporated into the starch matrix to form biocomposites and then compared against lignin biocomposites and neat starch film for their thermal, mechanical, and hydrophobic performance. The biocomposites with LNPs are anticipatedly possessing better performance than the neat starch film and lignin biocomposites in all aspects.

Keywords

• Lignin nanoparticles
• Ultrasonication
• Alkali lignin
• Starch composites
• Biocomposites
• Reinforcing agent