Aqueous foam synergistically stabilized by the composite of lignin nanoparticles and surfactant

Foam is a thermodynamically unstable dispersion system, and the stability of foam under severe conditions is still a bottleneck restricting the application. Exploring the stabilization mechanism of foam and new ways to improve foam stability has always been a concern in related fields. Based on global attention to environmental friendliness, enhancing foam performance using green biomaterials is of great significance. This study explored the foam properties generated by the composite solution of bio-based lignin nanoparticles (LNPs) and surfactant. Experimental results show that, the composite foam is much more stable compared with the pure surfactant foam. The half-life time t 1/2 was 10 times higher than that of the pure surfactant foam at 423 K, and the dynamic stability of the foam under shear disturbance was significantly improved, too. A variety of experimental methods are used to investigate the foam stabilization mechanism of the composite system, and it was verified that the LNPs combined with the surfactant molecules both in bulk phase and at gas/water interface. The surfactant molecules arrange more closely at the interface, decrease the surface tension. The LNPs were carried into the foam films and the drained films could be 2–4 times thicker than pure AOS foam, which slow down the rate of gas permeating across the films and increase the strength and liquid carrying ability of liquid film. The decrease of the drainage rate and the maintaining of the thickness of the foam film both could be helpful for strengthen of the foam stability, even under harsh conditions such as high temperature and shear disturbance. Compared with water-soluble polymers, inorganic NPs and other artificially synthesized foam co-stabilizers, LNPs are of natural origin, degradable, stable in structure and have outstanding environmental-friendly superiority. The excellent performance of the green aqueous foam system composed of lignin NPs and surfactants revealed in this research shows good application prospects in the enhanced oil recovery and daily chemistry fields.