Influence of gas flow rate and surfactant concentration on SDBS foam properties

Foams stabilized by surfactants are widely applied in many industrial practices; thus, the investigation of properties of these foams is of significance. The aim of this study is to examine the influence of gas flow rate and surfactant concentration on properties of foams stabilized by sodium dodecyl benzene sulfonate (SDBS). Experiments were conducted using a commercially available instrument, FoamScan, with which the foamability, foam stability, bubble size, and liquid content of foam were determined. The results showed that as an increase in gas flow rate at the same surfactant concentration the foaming time decreased while the liquid content of foam increased. On the other hand, increasing the surfactant concentration at a desired gas flow rate, the foam properties (both foamability and foam stability) of SDBS increased at concentrations c < critical micelle concentration (cmc), but this effect did not scale linearly with concentration. When c ≥ cmc, there was no evident change in both foamability and foam stability. Moreover, foam stability was controlled not only by foam drainage process but also by bubble coalescence. These findings provide guidelines for generating foams with excellent properties suitable for specific foam applications by adjusting the gas flow rate and surfactant concentration.