stabilizers are essential to prevent phase separation and ensure long-term stability. Most conventional stabilizers are synthetic surfactants derived from fossil resources, raising environmental and health concerns and highlighting the need for sustainable alternatives. Lignin, an abundant byproduct of the pulp industry, shows strong potential as a natural stabilizer. Converting lignin into lignin nanoparticles (LNPs) greatly improves its dispersibility and surface activity, enabling their use as Pickering stabilizers. In this study, we developed a green, high-yield, and scalable anti-solvent precipitation method to produce LNPs with reproducible performance. The solvents are fully recyclable, and the resulting nanoparticles can be redispersed in water through sonication.

We systematically investigated how the initial lignin concentration influences LNPs characteristics and their ability to stabilize emulsions. The size and morphology of the LNPs were analyzed using dynamic light scattering (DLS), transmission electron microscopy (TEM), and asymmetric flow field-flow fractionation coupled with multi-angle light scattering (AF4–MALS). Their interfacial properties were evaluated through contact angle measurements and dynamic interfacial tension analysis. By increasing the initial lignin concentration, LNPs with hydrodynamic diameters ranging from 100 to 370 nm were obtained. These nanoparticles showed strong interfacial activity, readily adsorbing at the oil–water interface and reducing interfacial tension. When used as stabilizers in Pickering emulsions, the LNPs produced uniform droplet sizes and highly stable emulsions. Interestingly, LNPs of different sizes exhibited similar stabilizing performance. Combined AF4–MALS, TEM, and atomic force microscopy (AFM) analyses suggest that a portion of the LNPs undergoes partial deformation during ultrasonication, generating smaller fractions that contribute to emulsion stabilization.

Overall, this work demonstrates a scalable and sustainable route for producing LNPs with stable, size-independent surface properties, enabling reliable performance in Pickering emulsions. The findings provide valuable insight into designing reproducible, bio-based colloidal stabilizers and support the broader development of eco-friendly emulsions.