Emulsification plays a key role in enhanced oil recovery (EOR) by facilitating the mobilization of residual oil. In this study, lignin nanoparticles (LNPs) were rapidly and environmentally synthesized from rice straw via acidification combined with ultrasonication, yielding spherical particles with sizes of 80–200 nm and a zeta potential of approximately -40 mV. FTIR analysis confirmed that the lignin structure was preserved after nanoization, while surface activity and dispersibility were enhanced. SEM, DLS, and zeta-potential results demonstrated that the obtained LNPs possessed suitable physicochemical properties for stabilizing oil-in-water emulsions. At low concentrations, LNPs acted as effective Pickering stabilizers, producing emulsions with high stability and nearly constant viscosity for up to 31 days. Compared with cellulose nanoparticles, biosurfactants, and alkali-based LNPs, the proposed green and scalable method achieved superior emulsion stability, highlighting the potential of lignin nanomaterials as environmentally friendly emulsifier stabilizers for EOR and promoting the valorization of agricultural residues.
Nguyen et al. (2026) studied this question.