Surfactants and foam have been capturing the interests of researchers worldwide due to their unique behavior of surface activity, the dynamic nature of foam formation, and simultaneous annihilation. The present review classifies the surfactants and admixtures used to generate stable aqueous foam for various applications. The study focuses on the surfactants’ classification, surfactant-solvent interaction, foam formation, characteristics, and a range of admixtures to enhance the foam performance.
The research focus has recently shifted towards the sustainability aspect of the surfactant’s utilization in various industrial applications. One such aspect is the development of green foaming agents from natural and renewable sources and assessing their suitability for different applications. Further, the effect of parameters, like type of surfactant, surfactant concentration, surfactant-solvent interaction, and foam production method, on the foamability of a surfactant solution and related foam characteristics, including stability, rheology, and texture, have been widely researched. However, still, there is no rule to predict the best foam. The best foam can only be obtained by trial and error by optimizing the influencing factors. Another vital concern is the non-standardization of foam assessment methods across the industries and regions, which needs to be addressed. Recently, research has progressed in identifying suitable admixtures for foam performance enhancement and utilizing them to produce stable foams for application in enhanced oil recovery, drug delivery, and manufacturing of aerated food products and foamed concrete. Although foam stabilization using various admixtures has been recognized well in the literature, the underlying mechanism requires further research. The interaction of surfactant and admixtures in solution is quite complicated. Several admixtures in ionic additives and nanoparticles may destabilize the foam instead of stabilizing beyond a particular concentration. Further, the influence of an admixture may not be similar for all vital foam characteristics. Hence, the effect of individual and multiple admixtures on the foaming solution and foam characteristics requires further research.