Interfacial tension emulsion stability affected

Alkaline inorganic chemicals such as sodium silicates, sodium hydroxides, sodium carbonate, and sodium phosphates have been added to injection fluids used in enhanced oil recovery systems. These chemicals can, in varying degrees, affect various rock and fluid parameters such as interfacial tension, interfacial viscosity, emulsion stability, rock wettability, hardness-ion content, ion-exchange capacity or equilibria, surfactant adsorption, phase equilibria, etc., in order to improve recovery efficiency for residual oil remaining after waterflooding. 

Emulsification is a stabilizing effect of proteins a lowering of the interfacial tension between immiscible components that allow the formation of a protective layer around oil droplets. The inherent properties of proteins or their molecular conformation, denaturation, aggregation, pH solubility, and susceptibility to divalent cations affect their performance in model and commercial emulsion systems. Emulsion capacity profiles of proteins closely resemble protein solubility curves and thus the factors that influence solubility properties (protein composition and structure, methods and conditions of extraction, processing, and storage) or treatments used to modify protein character also influence emulsifying properties. 

Emulsions and foams are two other areas in which dynamic and equilibrium film properties play a considerable role. Emulsions are colloidal dispersions in which two immiscible liquids constitute the dispersed and continuous phases. Water is almost always one of the liquids, and amphipathic molecules are usually present as emulsifying agents, components that impart some degree of durability to the preparation. Although we have focused attention on the air-water surface in this chapter, amphipathic molecules behave similarly at oil-water interfaces as well. By their adsorption, such molecules lower the interfacial tension and increase the interfacial viscosity. Emulsifying agents may also be ionic compounds, in which case they impart a charge to the surface, which in turn establishes an ion atmosphere of counterions in the adjacent aqueous phase. These concepts affect the formation and stability of emulsions in various ways ... 

Figure 13. Electrophoretic mobility (Fen Kem 3000) of the emulsion from Figure 12 after cationic polymer addition (A). The cationic polymer has neutralized the oil droplet surface charge and electrostatically destabilized the emulsion. The photomicrograph (B) shows this destabilized emulsion that has begun to flocculate or a lomerate but that is not coalescing. This electrostatic destabilization is not the only factor affecting emulsion stability. Factors such as interfacial tension and film strength can prevent coalescence of the emulsion droplets, even though they can now closely approach each other and ag omer-...

The presence of surfactants, either natural or added, promotes emulsion stability by the reduction of interfacial tension and the formation of highly rigid films on the surface of the droplets. This reduction of interfacial tension can increase the maximum, M, in Figure 4 significantly through charge stabilization or steric stabilization (J5). Because the nature and shape of the interaction energy curve determine the stability of OAV (and other types) of emulsions, any process, parameter, or phenomenon that affects the shape of this curve will ultimately control emulsion stability. 

Temperature. Temperature can affect emulsion stability in a number of ways. Temperature affects interfacial tension, which generally decreases with increasing temperature (J 7,... 

A lower interfacial tension will lead to a more stable emulsion. Temperature affects physical properties of oil, water, interfacial films, and surfactant solubilities in the oil and water phases, which can all affect emulsion stability. Further, the rheology of the emulsion itself is affected significantly by temperature. 

Emulsion stability is affected by temperature, continuous phase viscosity, droplet sizes and their distribution, interfacial tension (IFT), and interfacial film properties. Some of these effects were discussed in the preceding section. This section discusses the effects of viscosity, polymer, IFT, and interfacial film. 

The interfacial tension, o, affects the rate ratio directly only through the capillary pressure, P = 2o/P. The electrolyte primarily affects the electrostatic disjoining pressure, n, which decreases as the salt content increases, thus destabilizing the OAV emulsion. It can also influence the stability by changing the surfactant adsorption (including the case of nonionic surfactants). 

Coalescence is also controlled by the condition of drop surfaces. Surfactants reduce the interfacial tension and help preserve drop stability, therefore affecting drop sizes. Surface-active materials are important in suspension/emulsion polymerization processes. 

The interfacial tension, o, affects directly the rate ratio in Eq. (89) through the capillary pressure, 2da. The addition of electrolyte would affect mostly the electrostatic component of the disjoining pressure (see Fig. 8a), which is suppressed by the electrolyte the latter has a destabilizing effect on OAV emulsions. In the case of ionic surfactant solutions the addition of electrolyte rises the surfactant adsorption and the Gibbs elasticity (see Fig. 5), which favors the stability of emulsion I. 

Emulsifiers have long been used to stabilize O/W and water-in-oil (W/O) emulsions, because they play the role of decreasing the interfacial tension between the phases, which facilitates the separation of one phase in the form of small droplets [14]. To stabilize the emulsion, an emulsifier forms a thin film (interface) between the internal and external phases. The nature of the thin films formed at the interface of the emulsion droplets is controlled by the type of emulsifier and affects the stability of the emulsion interface [15-17]. For example, the addition of Tween 20 or Tween 60 results in thin interfaces around the oil... 

---