A critical review of the growth, drainage and collapse of foams

Abstract

This review focuses on the current knowledge regarding (i) the mechanisms governing foamability and foam stability, and (ii) models for the foam column kinetics. Although different length scales of foam structure, such as air-water interface and liquid film, have been studied to elucidate the mechanisms that control the foamability and foam stability, many questions remain unanswered. It is due to the collective effects of different mechanisms involved and the complicated structures of foam sub-structures such as foam films, Plateau borders and nodes, and foam networks like soft porous materials. The current knowledge of the effects of solid particles on liquid film stability and foam drainage is also discussed to highlight gaps in our present level of understanding foam systems with solid particles. We also critically review and summarize the models that describe macroscopic foam behaviors, such as equilibrium foam height, foam growth and collapse, within the context of the mechanisms involved.

A novel strategy for realising environmentally friendly pigment foam dyeing using polyoxyethylene ether surfactant C14EO5 as a foam controller

“…Foamability represents the capability of surfactants solution to produce foams, and foam stability refers to the lifetime of a foam column. As for the foam stability, foam drainage caused by gravity is crucially important [27]. On the one hand, the surface energy DE = cA increases with increasing newly created surface A and surface tension c during foam formation [26].…”

“…Firstly, the influence of pigment dispersion or binder on the surface tension and viscosity of a foaming dispersion containing 8 wt% C 14 EO 5 was investigated in order to help analyse their effects on foam properties. Solid particles reportedly can act as antifoam to destroy foam films [27]. In particular, when the pigment dispersion concentration was higher than 2 wt%, the viscosity increased dramatically.…”

Remediation of Diesel Contaminated Soil by Tween-20 Foam Stabilized by Silica Nanoparticles

“…In the study conducted, the drainage of liquid from foam stabilized by 0.5% silica nanoparticles was found to be slower and higher diesel oil removal efficiency was noted. Though the mechanism by which silica hydrophobic particles affect drainage is unclear, the hydrophilic particles tend to adhere to the foam [25]. …”

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

“…We recall the scaling relation for the description of the droplet size in turbulent mixing in emulsification, which is relevant to the breakup of bubbles in foam formation [12] The dynamics of adsorption of surfactant molecules must be considered when the adsorption time is longer than the time scale of foam formation [7,18]. The evolution of the surface tension value is controlled by two processes: (i) the diffusion of surfactant molecules to the surface and (ii) the adsorption of surfactant molecules on the interface, which must overcome an associated energy barrier.…”

“…Unlike surfactants, antifoams prevent foam formation. As a rule of thumb, solutions with low surface tension, fast adsorption dynamics, and high surface viscoelasticity are considered to be good foaming solutions [4][5][6][7]. However, foam properties are determined by many interrelated factors that can interact and produce synergistic or antagonistic effects.…”