In light of fossil resource depletion and the need for sustainable solutions, the interest for lignocellulosic biomass-derived products is always bigger. Among them, lignin, the most abundant renewable aromatic biopolymer, remains underutilized, often limited to energetic valorization¹, despite its antioxidant, UV protection, and antimicrobial properties, which could address various technical and industrial needs². Waste produced by the wood industry or agriculture offers significant potential for extraction of macro-lignin.
In this work macro-lignin are firstly extracted using the eco-friendly organosolv process³. Then the nano-lignins are produced through an anti-solvent process^3-4. Nano-lignins, with their small size (100-150 nm)⁴, has a larger specific surface area, and a better homogeneity making their incorporation promising in various applications. One example of this valorization is the stabilization of Pickering emulsions.
Pickering emulsions are widely used in the cosmetic⁵ and pharmaceutical industries, particularly for encapsulating active ingredients. The majority of nanoparticles currently used are manufactured using environmentally detrimental processes, and thus, the study of the stability of Pickering emulsions stabilized with nano-lignins addresses this issue. To optimize this process, a parametric study is conducted, optimizing key factors such as the concentration of nano-lignins in suspension, the energy supplied for agitation, the oil/water ratio, and the lignin sources (Beech, Spruce, Wheat Straw). This study highlights the strong ability of nano-lignin to stabilize emulsions, notably through the achievement of emulsions stable for 60 days with a suspension concentration of only 5 mg/g.

References :
¹Bajwa, D., et al. (2019). Industrial Crops And Products, 139, 111526. ²Zhang, Z., et al. (2021). Nanomaterials, 11(5), 1336. ³Girard, V., et al. (2024). ACS Sustainable Chemistry & Engineering, 12(18), 7055-7068. ⁴Girard, V., et al. (2024). Nanomaterials, 14(22), 1786. https://doi.org/10.3390/nano14221786⁵Espinoza-Acosta, J. L., et al. (2021). (2016). BioResources, 11(2), 5452-5481.

Acknowledgement:
The authors thank the Plateforme PhotoNS of the L2CM Laboratory, (Université de Lorraine) F-54000 Nancy, France and the Plateform Green Process for Wood (GP4Wood) of LERMaB Laboratory (Université de Lorraine-INRAe), F-54000 Nancy, France.

Stéphane Parant

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