Surfactants in emulsification

As shown by these results, very reasonable predictions can be tnade regarding surfactants in emulsification using the mathe-niatical approach described. 

Liu, Q., Dong, M.-Z., Yue, X., Hou, J., 2006b. Synergy between alkah and surfactant in emulsification of heavy oil in brine. Colloids and Surfaces A Physicochemical and Engineering Aspects... 

The lowering of y is important but is not the essential role of surfactants in emulsification. Consider, for example, making an 0/W emulsion with either paraffin oil or triglyceride oil. With pure water, the former gives y w 50, the latter y 30 mNm L If surfactant is added to the water, to arrive at an equilibrium value of y 30 mNm" with paraffin oil, an emulsion can be made with pure triglyceride oil and water, yielding the same y, an emulsion cannot be made. Hence, the surfactant must have another effect. 

The relations mentioned vary greatly among surfactants, which can be classified in various ways. An important distinction is between small-molecule surfactants, for convenience called soaps , and polymers (both synthetic polymers and proteins are used). These differ greatly in properties, as illustrated below. Another distinction is between soluble and insoluble surfactants. In emulsification, surfactants have to be soluble, unless they are rendered insoluble, by chemical modification, after adsorption onto the O-W interface. 

Uses Surfactant in emulsification of aromatic hydrocarbons wetting agent detergent antistat, lubricant for textile fiber processing stabilizer for polymer emulsions... 

Uses Dispersible surfactant in emulsification of min. oils textile softener and antistat in lubricants for syn. and wool fibers Properties Liq. sol. in aromafic solv. 98% acf. 

Of the cations (counterions) associated with polar groups, sodium and potassium impart water solubiUty, whereas calcium, barium, and magnesium promote oil solubiUty. Ammonium and substituted ammonium ions provide both water and oil solubiUty. Triethanolammonium is a commercially important example. Salts (anionic surfactants) of these ions ate often used in emulsification. Higher ionic strength of the medium depresses surfactant solubihty. To compensate for the loss of solubiUty, shorter hydrophobes ate used for appHcation in high ionic-strength media. The U.S. shipment of anionic surfactants in 1993 amounted to 49% of total surfactant production. 

S. Brdsel and H. Schubert Investigation of the Role of Surfactants in Mechanical Emulsification Using a High-Pressure Homogenizer with an Orifice Valve. Chem. Eng. Process. 38, 533 (1999). 

I. Kobayashi, M. Nakajima, and S. Mukataka Preparation Characteristics of Oil-in-Water Emulsion Using Differently Charged Surfactants in Straight-Through MicroChannel Emulsification. Colloid Surfaces A Physicochem. Eng. Aspects 229, 33 (2003). 

Partition Coefficients of nonvl-phenyl-poly-(ethoxy)-ethanol (NPE) Surfactants. The solubility of surfactants in water and hydrophobic solvents is well documented (11,12,22), but only a few attempts at measuring partition coefficients between immiscible liquids have been reported (2,4,9,10). Partition coefficients of surfactants are of theoretical interest because of their relation to observed surfactant properties such as emulsification, wetting and detergency. Partition coefficients (K ) may be also of considerable practical value for predicting surfactant recov and recycling in industrial processes. For example, in the cold water extraction of tar sand, an effective surfactant with a high Kp could be efficiently recycled in the process water and would not follow the bitumen into the upgrading stream. 

Recently, nonionic ortho ester surfactants have been used as emulsifiers for squalene, a polar oil [65]. In this case a polymer is used together with the surfactant. The emulsification is made under acidic conditions, and the surfactant breaks down rapidly after the emulsion is formed, leaving a surfactant-free, polymer stabilized emulsion with reasonable stability. 

The concept of interfacial mesophases promoting spontaneous emulsification (21.22) can be applied to the Tagat TO - Miglyol 812 system, where stable liquid crystalline dispersion phases are adequate to promote the process of self-emulsification. The stability of the resulting emulsion systems can also be accounted for by liquid crystalline interface stabilisation (23.24). Phase separation of material as observed above 55f surfactant, in conjuction with the increased viscosities of such systems, will inhibit the dynamics of the self-emulsification process and hence the quality of self-emulsified systems declines when the surfactant concentration is increased above 55. ... 

The removal of liquid oily soils from surfaces is generally understood in terms of three basic mechanisms the roll - back of droplets of oily soil, the surfaces of which are modified by the presence of an adsorbed layer of surfactant direct emulsification of macroscopic droplets of soil and the direct solubilization of the oily soil into surfactant micelles or other interfacial phases formed (1-3). 

The adsorption of surfactants at the liquid/air interface, which results in surface tension reduction, is important for many applications in industry such as wetting, spraying, impaction, and adhesion of droplets. Adsorption at the liquid/liquid interface is important in emulsification and subsequent stabilization of the emulsion. Adsorption at the solid/liquid interface is important in wetting phenomena, preparation of solid/liquid dispersions, and stabilization of suspensions. Below a brief description of the various adsorption phenomena is given. 

There is a vast body of diblock copolymer studies since block choice can be such that they resemble amphiphilic surfactants. For the sake of brevity, we will skip them. Instead, we present an interesting case of triblock copolymers of poly(ethylene oxide), PEO, and poly(propylene oxide), PPO, commonly known by one of its trade names, Pluronics [117]. They have been used as non-ionic surfactants for a variety of applications such as in emulsification and dispersion stabilization. In aqueous solutions, these copolymers form micelles, and there exists a well-defined critical micelle concentration that is experimentally accessible. Several groups have investigated colloidal suspensions of these polymers [118-122], The surface properties of the adsorbed monolayers of the copolymers have been reported with respect to their structures and static properties [123-126]. 

Little and Singleterry (7) have published an interesting study on micellization of surfactants in a variety of solvents. Their data show that the better the solvent is for the surfactant, the less tendency there is for the surfactant to form aggregates or micelles. Yet to be determined is the effect of this micellization on emulsification properties. 

To this point, we have considered the interaction of nonionic surfactants within the framework of the mathanatical model. The activity and character of anionics in emulsification is complicated by the ionization steps which an anionic surfactant may take when exposed to salt solutions. For instance, in a dialkyl metallic salt, there are three compounds which may exist in various concentrations, depending ipon the ionic strength of the salt solution which, in turn, would exhibit, at least, three different HLB nuiiibers. To address the problem of generating Cohesive Energy Density parameters for the anionic hydrophiles, certain standardized assunptions... 

Nearly all of the treatment processes in which fluids are injected into oil wells to increase or restore the levels of production make use of surface-active agents (surfactant) in some of their various applications, e.g., surface tension reduction, formation and stabilization of foam, anti-sludging, prevention of emulsification, and mobility control for gases or steam injection. The question that sometimes arises is whether the level of surfactant added to the injection fluids is sufficient to ensure that enough surfactant reaches the region of treatment. Some of the mechanisms which may reduce the surfactant concentration in the fluid are precipitation with other components of the fluid, thermally induced partition into the various coexisting phases in an oil-well treatment, and adsorption onto the reservoir walls or mineral... 

Application Used as a dispersible surfactant in the emulsification of mineral oils. A softener and antistatic agent for textiles. Soluble in aromatic solvents. Used for formulating lubricants for synthetic and wool fibers. 

One of the earliest uses of power ultrasound in processing was in emulsification. If a bubble collapses near the phase boundary of two immiscible liquids, the resultant shock wave can provide a very efficient mixing of the layers. Stable emulsions generated with ultrasound have been used in the textile, cosmetic, pharmaceutical, and food industries. Such emulsions are often more stable than those produced conventionally and often require little, if any, surfactant. Emulsions with smaller droplet sizes within a narrow size distribution are obtained when compared to other methods. 

The focus here is on these mechanisms. A high content of naphthenic acids in heavy oils is a good property for soap generation and emulsification. Therefore, this chapter also presents the synergy between alkali and surfactant in heavy oil reservoirs. First, it discusses the phase behavior of the mixed system of soap and surfactant. Then it describes how to build up a UTCHEM phase behavior model and how to use the model to analyze phase behavior. In addition, this chapter investigates a number of parameters related to phase behavior. 

The other observations were reported elsewhere, however. Figure 13.3 shows polymer made the surfactant system emulsification better, and Figure 13.4 shows polymer slightly changed the value of electrophoretic mobility. The addition of polymer into an ASP system does not change IFT but shortens the phase separation time of emulsions. In these examples, when alkali concentration was below 1%, as the concentration was increased, the phase separation time decreased. When alkali concentration was above 1%, the phase separation time increased with the concentration. Thus, polymer apparently reduced the interaction between oil and alkali when alkali concentration was high. 

Emulsification—the formation of emulsions from two immiscible liquid phases—is probably the most versatile property of surface-active agents for practical applications and, as a result, has been extensively studied. Paints, polishes, pesticides, metal cutting oils, margarine, ice cream, cosmetics, metal cleaners, and textile processing oils are all emulsions or are used in emulsified form. Since there are a number of books and chapters of books devoted to emulsions and emulsification (Sjoblom, 1996 Solans and Kunieda, 1996 Becher, 2001), the discussion here covers only those aspects of emulsification that bear on the role of surfactants in this phenomenon. 

The microchannel emulsion technique has been extended to the formation of multiple emulsions [158-163], encapsulation [123, 158, 164—166], polymer bead formation [123, 125, 167-169], demulsification [116, 158, 170], and even microbubble formation [171]. New methods of stabilizing emulsions have also been investigated in this realm, including particle-stabilized [172] and protein-stabilized emulsions [173], with some work in emulsification without surfactants [135,146]. In the case of multiple emulsions, microchannel architecture can enable the formation of W/O/W emulsions in which two water droplets of different compositions can be encased in the same oil droplet [163]. 

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