Acetone/Water Cosolvent Approach to Lignin Nanoparticles with Controllable Size and Their Applications for Pickering Emulsions

In this study, we showed that lignin nanoparticles (LNPs) with controllable size could be prepared using the acetone/water cosolvent (A/W) approach. The solubility of lignin in A/W of varied constitution (10:0 to 0:10 v/v) was determined, and A/W containing 7:3 (v/v) acetone to water was identified as the optimum solvent. A positive correlation between LNP size and lignin concentration was observed, with the smallest LNPs (28.5 ± 5.4 nm) obtained at 5.00 g/L of lignin, while serious aggregation occurred at lignin concentrations above 100 g/L. The rotary evaporation procedure used to remove acetone had no noticeable effect on the size of LNPs. The obtained LNPs were utilized as emulsifiers to stabilize oil-in-water Pickering emulsions of various oils. The results indicated that the high efficiency of LNPs in stabilizing Pickering emulsions was due to their irreversible adsorption at the oil–water interface of the droplets. Overall, a straightforward way for the controllable preparation of LNPs and their use as Pickering emulsifiers was demonstrated.