Kinetics and dynamics of Gas-liquid separation and bubble generation in surfactant solutions: Role of bulk/interfacial properties and hydrodynamic conditions

Abstract

Understanding the kinetics and dynamics of gas–liquid separation and bubble generation in surfactant solutions is important for many industrial applications. To explore the potential mechanisms affecting the physical properties (expansion ratio, bubble size, and foam stability) of foams and bubbles, the surface tension of the solution, including the equilibrium and dynamic properties, was investigated. Then, the morphology of the surfactant aggregates was explored by cryo-transmission electron microscopy (cryo-TEM). Based on these experimental results, the effects of various physical and chemical factors (including the relative concentration of surfactant, dynamic surface tension, surface coverage, surface elasticity, surface mobility, aggregate morphology, etc.) on the expansion ratio and bubble size were analysed to identify which “universal” parameters can explain the phenomenon for all aqueous solutions in the gas–liquid separation process. Research has shown that the morphology of aggregates in a solution largely determines the surface properties of the solution at 1.5 ms (surface tension, surface coverage, surface elasticity, and so on). These surface properties significantly affect the expansion ratio. However, no good correlation was found between bubble size and these surface properties because surfactant vesicles can directly affect bubble size. In addition, the liquid flow rate and gas–liquid ratio have a significant impact on the expansion ratio and bubble size. Ultimately, we found that the foam stability, bubble size, and expansion ration can be described by a simple linear relationship. Our research provides new opinions for further understanding the effects of bulk/interfacial properties and hydrodynamic conditions on the physical properties of bubbles in the gas–liquid separation process.