Synthesis of lignin nanoparticles from Oxytenanthera abyssinica by nanoprecipitation method followed by ultrasonication for the nanocomposite application

Abstract

Lignin nanoparticles (LNPs) have a wide range of potential uses in the biomedical and environmental fields. They are used to prepare antioxidants, food packaging material, energy storage, cosmetics, thermal/light stabilizers, reinforced materials, and drug delivery. In this study, LNPs were prepared from soda lignin obtained from Oxytenanthera abyssinica using dioxane, acetone, ethanol, and acid-base solvents through the nanoprecipitation method, followed by an ultrasonic process. These methods produced four different LNPs with yields in the range of 28.5% to 88.9%. Scanning electron microscope (SEM) showed that the spherical-shaped LNPS (100–400 nm) were obtained using the acetone solvent, while irregularly shaped LNPs were formed by dioxane (150–400 nm), ethanol (40–200 nm) and acid-base (100–800 nm) solvents. The maximum zeta potential of the LNPAS samples was |-35.1 mV|, determined by the dynamic light scattering (DLS), with a particle size distribution between 91.28 and 458.7 nm. According to the energy-dispersive X-ray spectrometer (EDX) results, the sample contains the elements C, O, Si, Na, and Mo. X-ray powder diffraction (XRD) analysis showed very small crystallinity sizes ranging from 0.31 to 0.35 nm. Proton nuclear magnetic resonance (H-NMR) and Fourier transformation infrared Spectroscopy (FTIR) were used to find the functional groups in the synthesized LNPs. The Thermogravimetric analysis (TGA) peak showed that LNPS was thermally stable, and rapid mass loss occurred between 300 and 415 °C. Differential Scanning Calorimetry (DSC) data shows that the highest exothermic peaks are obtained at 345.2 °C. Synthesis of LNPs by dissolving isolated soda lignin in acetone, ethanol, dioxane, and acid-base solvents was quickly recovered, cheap, and eco-friendly. The synthesized are free of sulfur; they do not use toxic solvents such as Tetrahydrofuran (THF), Dimethyl sulfoxide (DMSO), and Dimethylformamide (DMF). Thus, they provide benefits for high-value-added Nanocomposite applications such as bio-based nonmaterial and food packaging materials. Acid-base nanoprecipitation procedure is the best approach regarding stability and size, but the acetone nanoprecipitation method is preferable regarding shape.