Investigation of the Effect of Marangoni Flow and Molecular Arrangement on the Stability of Nanoparticle-stabilized Foam- An Experimental Study

The main purpose of this study is to determine the molecular arrangement in lamella and the role of Marangoni convection in foam stability in the presence of nanoparticles. Experiments were conducted in two different foam systems of (1) anionic nanoparticles-cationic surfactant (CTAB) and (2) anionic nanoparticles-anionic surfactant (SDS). Observations showed that the effective mechanisms of stability are different. Although nanoparticles increase the stability of both foam systems, the presence of nanoparticles in the like-charge system improves foamability. In contrast, in the unlike-charge system, foamability decreases with the increment of nanoparticle concentration. The most influential factor in the foam stability in the like-charge case is the repulsive force which sends more surfactant molecules to the interface. Surface tension results demonstrate that Marangoni flow restitutes the negative impact of gravity drainage and increases the foam stability. In contrast, In the unlike-charge system, the presence of nanoparticles at the interface increases detachment energy significantly, and as a result, the stability boosts. The accumulation of nanoparticles in the interface changes it to a solid-like and high elasticity surface; thus, Marangoni flow is lost.