Surfactant-water-oil system

B.W. Brooks and H.N. Richmond Phase Inversion in Non-Ionic Surfactant-Oil-Water Systems, I. The Effect of Transitional Inversion on Emulsion Drop Size. Chem. Eng. Sci. 49, 1053 (1994). 

M. Perez, N. Zambrano, M. Ramirez, E. Tyrode, and J.L. Salager Surfactant-Oil-Water System near the Affinity Inversion. XII. Emulsion Drop Size Formulation and Composition. J. Dispersion Sci. Technol. 23, 55 (2002). 

J.L. Salager, M. Minana-Perez, M. Perez-Sanchez, M. Ramirez-Gouveia, and C.I. Rojas Surfactant-Oil-Water Systems near the Affinity Inversion. Part HI The Two Kinds of Emulsion Inversion. J. Dispersion Sci. Technol. 4, 313 (1983). 

The property of interest to characterize a surfactant or a mixture of surfactants is its hydrophilic-lipophilic tendency, which has been expressed in many different ways through a variety of concepts such as the hydrophiUc-lipophilic balance (HLB), the phase inversion temperature (PIT), the cohesive energy ratio (CER), the surfactant affinity difference (SAD) or the hydrophilic-lipophilic deviation (HLD) [1], which were found to be more or less satisfactory depending on the case. In the next section, the quantification of the effects of the different compounds involved in the formulation of surfactant-oil-water systems will be discussed in details to extract the concept of characteristic parameter of the surfactant, as a way to quantify its hydrophilic-lipophilic property independently of the nature of the physicochemical environment. 

Fig.1 Phase behavior types of surfactant-oil-water systems as Winsor Diagrams for difer-ent cases of the ratio R of interactions between the surfactant adsorbed at interface and the oil and water molecules...

Salager JL (1996) Quantifying the Concept of Physico-Chemical Formulation in Surfactant-Oil-Water Systems. Prog Colloid Polym Sci 100 137-142... 

Anton RE, Garces N, Yajure A (1997) A correlation for three-phase behavior of cationic surfactant-oil-water systems. J Dispers Sci Technol 18 539-555... 

Salager JL, Bourrel M, Schechter RS, Wade WH (1979) Mixing rules for optimum phase behavior formulations of surfactant-oil-water systems. Soc Petrol Eng J 19 271-278... 

Salager JL, Minana-Perez M, Perez-Sanchez M, Ramirez-Gouveia M, Rojas Cl (1983) Surfactant-oil-water systems near the affinity inversion. Part III The two kinds of emulsion inversion. J Dispers Sci Technol 4 313... 

Salager JL, Marquez N, Anton RE, Graciaa A, Lachaise J (1995) Retrograde Transition in the Phase Behavior of Surfactant-oil-water systems produced by an alcohol scan. Langmuir 11 37-41... 

Ysambertt F, Anton RE, Salager JL (1997) Retrograde Transition in the phase behavior of surfactant-oil-water systems produced by an oil EACN scan. Colloid Surf A 125 131-136... 

Figure 11, which is based on the phase behavior of surfactant/ oil/water systems, illustrates just a few of the many different patterns of phase behavior that may be encountered. On the left is a simple, "well-behaved" system, such as is implicitly assumed in most mobility control studies on "foams." Barring unforeseen wettability problems, the system can be expected to form a "C02 in-water foam."... 

Alcohols, at least those of short chain length, have moieties that are neither extremely hydrophilic, nor extremely hydrophobic, and partition in a complex way between oil emd water, or between the oil-like interior of a micelle or membrane, and water. This property, together with their small head-group area, enables them to be used with siirfactant-water, or surfactant-oil-water systems to produce a rich diversity of microstructured solutions through changing curvature of the interface, as does cholesterol, for the same reasons. The self-assembly of biological aggregates is further complicated by the presence of amphiphilic proteins. 

Brooks, B.W. Richmond, H.N. Phase inversion in non-ionic surfactant-oil-water systems. I. The effect of transitional inversion on emulsion drop sizes. Chem. Eng. Sci. 1994, 49, 1053-1064. 

Anton, R.E. et ah. Surfactant-oil-water systems near the affinity inversion. IX Optimum formulation and phase behavior of mixed anionic-cationic systems, J. Dispersion Sci. Technol., 14, 401, 1993. Kahlweit, M. et ah. General patterns of phase behavior of mixtures of water, nonpolar solvent, amphiphiles, and electrolytes, 1,2, Langmuir, 4, 499, 1988 5, 305, 1989. 

Formulation is important because the properties of surfactant-oil-water systems in general and the formation of microemulsions in particular, are very sensitive to it and slight deviations from a proper formulation may result in drastic changes of the properties. Consequently, formulation has to be controlled accurately, which is quite challenging because of the high number of degrees of freedom in any practical case. This is why formulation is sometimes considered as magic business . 

The phase behaviour at equilibrium turned out to be the main property reported in Win-sor s work in the late 1940s. Winsor interpreted the phase behaviour through the so-called R ratio of molecular interaction energies at interface. The R ratio was a handy theoretical concept to understand the variations of the phase behaviour of surfactant-oil-water systems and somehow of the emulsion properties. It is essentially qualitative, but for the first time the phase behaviour was linked with a condition that depended on all formulation variables, but could be expressed as a single generalised variable, i.e. the R ratio [1]. The original R ratio was... 

A decade after the empirical determination of the correlations for three-phase behaviour and the corroboration that the linearity and generality could not be coincidental, a simple interpretation was found through the so-called surfactant affinity difference (SAD) concept discussed next. When a simple ternary surfactant-oil-water system exhibits three-phase behaviour, the chemical potential p. of the surfactant is equal in the three phases (oil, water and microemulsion) at equilibrium referred to by subscripts O, W and M. It holds... 

Changing the composition of a surfactant-oil-water system could modify the phase behaviour as indicated in Fig. 3.12 along the paths indicated by arrows. In many cases, the dilution by water or by oil results in the appearance or disappearance of a microemulsion. In the latter case, the microemulsion can be in equilibrium with excess water, excess oil or both. The problem is easily solved whenever a good phase diagram is at hand, which is not often the case as a matter of fact [63-65]. 

Perez, M., Zambrano, N., Ramirez, M., Tyrode, E. and Salager, J.L. (2002) Surfactant-oil-water systems near the affinity inversion. Part XII Emulsion drop size versus formulation and composition. /. Dispersion Sci. Technol., 23, 55-63. 

Salager, J.L. (1996) Quantifying the concept of physico-chemical formulation in surfactant-oil-water systems. Prog. Colloid Polym. Sci., 100, 137-142. 

Salager JL, Loaiza-Maldonado I, Minana-Perez M, Silva F. Surfactant—oil-water systems near the affinity inversion. Part I Relationship between equilibrium phase behavior and emulsion type and stability. J Dispersion Sci and Technol 1982 3 279-292. 

Figure 7 In surfactant-oil-water systems there is a segregation into oil and water domains and surfactant films. In (a) one can distinguish between cases of uncorrelated surfactant films (monolayers) and pairwise correlated films (bilayers), (b) Surfactant self-assembly can lead to discrete structures in which one of the solvents is enclosed or to structures that extend over macroscopic distances in one, two, or three dimensions. The bicontinuous structure, introduced by Scriven [34], in which both solvents form domains that are connected in three dimensions has stood in the foreground of microemulsion research. (Courtesy of Ulf Olsson.)...

In developing any theoretical method, however, a number of decisions must be made in advance. These include, in addition to a reasonable idea of what specific descriptions and predictions will be sought from the theories or models, a decision on what level of microscopic details will be incorporated into the model. Such a decision is dictated by the current limitations of the theoretical tools (e.g., classical or statistical thermodynamic theories) or computational resources. For example, microscopic models of micellization and solubilization can, in principle, be approached at the molecular level with a detailed structural representation of the various components along with their energetic interactions. Our current understanding of molecular dynamics is sufficiently comprehensive and well established to permit such a detailed approach to the evolution of mesoscopic and macroscopic structures and phenomena in surfactant-oil-water systems. However, the... 

This chapter will focus on a simpler version of such a spatially coarse-grained model applied to micellization in binary (surfactant-solvent) systems and to phase behavior in three-component solutions containing an oil phase. The use of simulations for studying solubilization and phase separation in surfactant-oil-water systems is relatively recent, and only limited results are available in the literature. We consider a few major studies from among those available. Although the bulk of this chapter focuses on lattice Monte Carlo (MC) simulations, we begin with some observations based on molecular dynamics (MD) simulations of micellization. In the case of MC simulations, studies of both micellization and microemulsion phase behavior are presented. (Readers unfamiliar with details of Monte Carlo and molecular dynamics methods may consult standard references such as Refs. 5-8 for background.)... 

Figure 20 A schematic representation of a three-component phase diagram for a surfactant-oil-water system. (From Ref. 36.)...

Other petroleum applications such as emulsion breaking, particularly for crude oil dehydration, are of first importance. A by-product of enhanced oil recovery was a better understanding of the relationship between the phase behavior of surfactant-oil-water systems and the properties of the corresponding macroemulsions [111-118]. 

The experimental technique used to find an optimum formulation, known a.s untdimensional scan, goes on as follows. Series of surfactant-oil-water. systems are prepared in test tubes, all with identical composition, and with the same formulation with the exception of the scanned variable, that is in general the aqueous phase salinity for ionic systems, and the average number of ethylene oxide groups per molecule (EON) if the systems contain an ethoxylated nonionic surfactant mixture. 

This chapter deals with emulsion properties, i.c.. type, drop. si c. siahility. and viscoMty. It shows how to estimate or measure them in practice and how thev arc related to formulation. conipu.sition. and other variables. The current kiiow how is presented in a comprehensive way so that the emulsion maker can use it to attain some suitable propeily. The ea.se of emulsion made from preequtli-bruted surfactant-oil-Water systems is treated first. Then follows a discu.ssion on how to modify emulsions to seek specific properties, which leads to the introduction t)f the dynamic inversion phenomena, discussed from the practitioner s point of view. 

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