Surfactant foamulsion stability in the absence and presence of salt

Foamulsions are widely used in many fields but the stability of them is still not fully understood. We investigate the evolution of foamulsions in the absence and presence of inorganic salt. For the system without salt, it is found that the effect of oil on the foamulsion properties depends on the critical threshold concentration of surfactant (300 mM), below which the foamulsion aging is slowed down and above it its evolution is facilitated. When salt is added, the surfactant molecules precipitates to form crystals, foamulsions tend to be generated in regions where the surfactant concentration is not less than the salt concentration, but it is difficult to foam at salt concentrations higher than 200 mM, independent of the oil concentration, unless the surfactant concentration is very high. For the prepared stable foamulsions, the stabilization mechanism is due to the inhibition of coarsening and coalescence of bubbles and oil droplets by the adsorption of surfactant molecules and crystal particles onto their surfaces. The investigation of adsorption kinetics show that maybe the crystals move to the surface of bubbles is faster than oil droplets. The system consisting of surfactant, oil, salt and water is simple and temperature sensitivity, which could have many potential applications.