Lignin has gained increased attention because of their promising advantages, including low production cost and eco-friendly properties, such as biocompatibility and biodegradability. Lignin is composed of three units, found in varying proportion according to the source of the lignocellulosic biomass (i.e., softwood, hardwood or grass), which can affect the properties of the resulting technical lignins. Despite the lignin high abundance in nature, only ~ 2% of lignin is employed as a starting material for low value applications, mainly limited by its highly variable and complex molecular structure. However, the fabrication of lignin nanoparticles (LNPs) can overcome these limitations, offering structural and morphological control of the lignin. Therefore, the production of LNPs has greatly increased their potential for high value applications in many fields, compared to the raw lignin. However, the homogeneity and morphology of LNPs varies depending on the lignin grade and preparation method, and a systematic comparison is lacking to evaluate those. In this study, we aimed to find a green preparation method to prepare LNPs using three different technical lignins as starting polymers: BLN birch lignin, alkali Protobind 1000, and kraft LignoBoost. For that, we systematically compared three anti-solvent precipitation approaches; 70% ethanol, acetone/water (3:1) and NaOH as the lignin solvent, and water/aqueous HCl as the anti-solvent. The resulting nanostructures were further characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). Their phenolic content was quantified using UV spectroscopy and compared with the conventional 31P nuclear magnetic resonance (31P NMR). Overall, our results revealed that the acetone/water mixture was the most effective solvent to obtain homogenous, small and spherical LNPs from the three technical lignins. Moreover, these LNPs showed an improved stability at different ionic strengths and a wider pH range compared to the other preparation methods, which can greatly increase their application in many fields, such as pharmaceutical and food sciences.

Green route fabrication approaches of lignin nanoparticles: a comparison study

ACS Spring Meeting 2021

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