Surfactant stabilizing foams

Alcohol sulfates are excellent foaming surfactants. According to the Kitchener and Cooper classification [148], alcohol sulfates form metastable foams. However, quantitative values cannot easily be compared because foam largely depends not only on the instrument used to produce and evaluate foam but also on the concentration of surfactant, impurities, temperature, and many other factors. In addition, a complete characterization of the foam capacity should take into account the initial amount of foam, its stability, and its texture. 

The foam volume and stability of alcohol sulfates is relatively increased in hard water compared to soft water. The amount and quality of foam is dependent on the alkyl length. Sulfates with C12-C,4 alkyl chains produce the richest creamy foam with small bubbles. C8-C10 alcohol sulfates are foam depressants and C16-C18 alcohol sulfates are poor foaming surfactants. Foams produced by alcohol sulfates are also relatively stable in the presence of sebum. Sodium and ammonium alcohol sulfates foam better than triethanolamine alcohol sulfates. Alcohol ether sulfates produce lighter foams than those of alcohol... 

W. A. Rendall, C. Ayasse, and J. Novosad. Surfactant-stabilized foams for enhanced oil recovery. Patent US 5074358, 1991. 

L. L. Schramm, C. Ayasse, K. Mannhardt, and J. Novosad. Method for improving enhanced recovery of oil using surfactant-stabilized foams. Patent CA 2006482,1991. 

The role of various surfactant association structures such as micelles and lyotropic liquid crystals (372), adsorption-desorption kinetics at liquid-gas interfaces (373) and interfacial rheology (373) and capillary pressure (374) on foam lamellae stability has been studied. Microvisual studies in model porous media indicate... 

Choose nonionics as suds stabilizers for use with foaming surfactants that are ionic. Prefer those with higher ability to lower the critical micelle concentration (CMC) of the foaming surfactant. 

Based on the underlying physical chemistry of surfactants at interfaces, important features of foam structure, stability, rheology, and their inlerrelalionships can be considered as ultimately originating in ihe molecular composition of the base liquid. 

In concentrated emulsions and foams the thin liquid films that separate the droplets or bubbles from each other are very important in determining the overall stability of the dispersion. In order to be able to withstand deformations without rupturing, a thin liquid film must be somewhat elastic. The surface chemical explanation for thin film elasticity comes from Marangoni and Gibbs (see Ref. [199]). When a surfactant-stabilized film undergoes sudden expansion, then immediately the expanded... 

In pure liquids, gas bubbles will rise up and separate, more or less according to Stokes law. When two or more bubbles come together coalescence occurs very rapidly, without detectable flattening of the interface between them, i.e., there is no thin-film persistence. It is the adsorption of surfactant, at the gas-liquid interface, that promotes thin-film stability between the bubbles and lends a certain persistence to the foam structure. Here, when two bubbles of gas approach, the liquid film thins down to a persistent lamella instead of rupturing at the point of closest approach. In carefully controlled environments, it has been possible to make surfactant-stabilized, static, bubbles, and films with lifetimes on the order of months to years [45],... 

The highest efficiency to reduce pattern collapse was found for concentrated surfactant solutions. This may, however, have serious disadvantages. Watanabe et al. [15] noticed that high surfactant concentrations melt the photoresist and amplify the pattern collapse. In contrary, Miyahara et al. [16] found that some nonionic surfactants stabilize the photoresist surfaces and prevent melting. In addition, concentrated surfactant solutions tend to foam which also might cause structure defects. Zhang et al. [17] therefore proposed a less foaming diol-type surfactant for the reduction of pattern collapse. 

The most important factor regulating the rate of foam column destruction are the surfactant kind, electrolyte concentration and additives that determined the structural characteristics of the foam (dispersity, film type and thickness, etc.) and foam film stability. 

In Figure 12 the process of collapse versus time for the three surfactant solutions and two oil phases is presented. From these results we conclude that C. A0S in the presence of n-octane and n-dodecane and Enordet AE 1215-30 in the presence of n-dodecane are low stability foams. Higher stability foams are formed by C. AOS in the presence of n-dodecane and Enordet AE 1215-30 in the presence of n-octane. 

The primary beneficiation act is schematically represented in fig. 5.43. Hydro-phobic particles (filled) attach to the ciir bubbles, whereas the hydrophilic ones (open) remain dispersed. The former ones move upward. Usually there is a surfactant-stabilized foam on top of the vessel, it is here that the attached particles can be recovered at Increased concentration. On the other hand, the unfloatable hydrophilic tailing can be removed from the lower side of the reactor. 

As a rule, the fluid dispersions (emulsions, foams) are stabilized by adsorption layers of amphiphile molecules. These can be ionic and nonionic surfactants, lipids, proteins, etc. All have the property to lower the value of the surface (or interfacial) tension, o, in accordance with the Gibbs adsorption... 

Copious foam usually requires the use of high-foaming surfactants, typically anionic or amphoteric surfactants or a mixture of surfactants. Long-lasting foam often requires the use of foam stabilizers in addition to surfactant mixtures. 

Over few last decades, applied problems have arisen which are related to the behavior of foams in porous media. It turns out that aqueous surfactant-stabilized foams can drastically reduce the gas mobility in porous media [334], This fact is of great applied significance in petroleum and gas industry. In [106, 189, 233], mechanisms of foam control of gas migration through porous media are presented. 

Alkamide . [Rhone-Poulenc Surf.] Alkanolamid or alkyl amidopropyl dimethylamines surfactant, det ent, foam booster/stabilizer, superfatting agent, thickener, emulsifier for personal care and laundry prods., cleaners lubricant for cutting oils. 

Swanic. [Swastik] Surfactants foam booster/stabilizer, wetting agent, emulsifier, detergent for cosmetics, deto-gent systems, textiles, concrete. 

Tegostab . [Goldschmidt] Silicone surfactants stabilizer for polyurethane foams. 

In 1961, Fried (1) demonstrated that aqueous surfactant-stabilized foam could drastically reduce the mobility of gases in porous media. At that time, foam was studied mainly from a phenomenological perspective. In the intervening 30 years, foam has been recognized as a fluid with unique rheological properties within porous media, and the scope of research has expanded to include local pore-scale phenomena and local microstructure. Because of its dispersed nature, foam profoundly affects the flow patterns of nonwetting fluids within porous media. 

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