Effect of microemulsion composition

THE EFFECT OF MICROEMULSION COMPOSITION ON THE ADSORPTION OF PETROLEUM SULFONATES ON BEREA SAND/MONTMORILLONITE CLAY ADSORBENTS... 

The adsorption from microemulsion of two petroleum sulfonates, PDM-334 and TRS 10-410, on Berea sand/montmorillonite clay adsorbents has been studied to determine 1) the effect of microemulsion composition, specifically its relative oil and brine content, on sulfonate adsorption 2) the effect of adsorption on the microemulsion composition and interfacial tension behavior. Whereas the degree of sulfonate adsorption can be determined by conventional methods (e.g. UV spectroscopy), one must utilize a microemulsion property which is a sensitive function of the relative oil and brine content of the microemulsion in order to determine the adsorption-induced changes in the microemulsion composition. This can be accomplished by the use of the microemulsion specific refraction. 

A qualitative model is proposed which accounts for the observed adsorption behavior in terms of the effect of microemulsion composition on the sulfonate-microemulsion, sulfonate-adsorbent and microemulsion-adsorbent interactions. 

The objective of the present work is to determine the static adsorption of petroleum sulfonates from microemulsions on representative reservoir solids and to define the effect of microemulsion composition, specifically its relative oil and brine content, on sulfonate adsorption. It is also of interest to determine the effect of adsorption on the microemulsion oil and brine content because of the relationship between microemulsion composition and interfacial behavior. Consequently, the adsorption of a given petroleum sulfonate was determined from a series of microemulsions where each microemulsion contained different volume fractions of the same oil and brine. The difference in microemulsion composition within such a series was effected either by using a different cosurfactant in each microemulsion or by changing the total surfactant/cosurfactant concentration. The adsorbent was carefully reproduced in each experiment in terms of sand/clay composition and total surface area. All experiments within a series were therefore carried out at constant temperature, pressure, adsorbent composition and total surface area. 

Changez M., Varshney, M., Chander, J. and Dinda, A.K. (2006) Effect of the composition of lecithin/n-propanol/isopropyl myristate/water microemulsions on barrier properties of mice skin for transdermal permeation oftetracaine hydrochloride In vitro. Colloid Surf. B, 50,18-25. 

Table 2 also shows that the specific refraction of each microemulsion increases as a consequence of adsorption. This result indicates that all post-adsorption microemulsions have higher oil to brine ratios than the corresponding pre-adsorption microemulsions. The effect of these compositional changes is reflected in the interfacial tension behavior of the microemulsions (Figure 3). The microemulsion-oil and microemulsion-brine interfacial tensions both before and after adsorption exhibit the familiar correlation with r (8) however, all values are decreased and all values are increased as a consequence of adsorption. The minimum in the controlling interfacial tension (yc)xnin also increased from 0.0070 dyne/cm to 0.0077 dyne/cm. It is interesting to note that the values for the n-butanol microemulsion both before and after adsorption lie considerably above the y curves. The microemulsion at r = 0.288 cm /g was not part of the adsorption... 

Fig. 6. Effect of surfactant composition and cosurfactant component on the microemulsion specific refraction also shown are the interfacial tensions for selected microemulsions and the locus of minima formed by the intersection of the array surface and the r plane.

Yaghmur, A., Rappolt, M., Ostergaard, J., Larsen, C. Larsen, S. W. (2012). Characterization of bupivacaine-loaded formulations based on liquid crystalline phases and microemulsions the effect of lipid composition. Langmuir, 28(5), 2881-9. 

The effect of microemulsion structure on reaction rate has also been studied in relation to oxidation and reduction of cysteine residues in keratin [10]. The system sodium dodecyl sulfate (SDS)/n-pentanol/water/dodecane was chosen as a microemulsion because in this system the realm of the existence of the isotropic region in the pseudoternary phase diagram is a continuous domain, extending from the water apex to the close vicinity of the hydrocarbon-surfactant edge. It was shown experimentally that the microemulsion structure varied smoothly with composition within the isotropic region. 

Table 15.5 The effect of interfacial composition and electrical property of the W/IL microemulsions on the catalytic activity of laccase.

Effect of Ionic Strength. Both yE systems were examined for ionic strength effects. Microemulsion compositions were prepared at 70% water, with a cyanide concentration of 0.032 M with respect to the water content. Potassium bromide was used to vary the ionic strength of the reaction mixtures. Ionic strength in the CTAB yE was varied from 0.04 to 0.34. Since the Brij yE tolerated a much higher salt concentration without phase separation, ionic strength in that system was varied between 0.04 and 1.80. As will be seen, the Brij system exhibits a salt effect, while the CTAB yE does not. Rate constants obtained for reaction (1) in the Brij yE were therefore corrected to take into account the effect of ionic strength in that system (vide infra). 

For a given surfactant, the ability to form a single-phase w/o microemulsion is a function of the type of oil, nature of the electrolyte, solution composition, and temperature (54-58). When microemulsions are used as reaction media, the added reactants and the reaction products can also influence the phase stability. Figure 2.2.4 illustrates the effects of temperature and ammonia concentration on the phase behavior of the NP-5/cyclohexane/water system (27). In the absence of ammonia, the central region bounded by the two curves represents the single-phase microemulsion region. Above the upper curve (the solubilization limit), a water-in-oil microemulsion coexists with an aqueous phase, while below the lower curve (the solubility limit), an oil-in-water water microemulsion coexists with an oil phase. It can be seen that introducing ammonia into the system results in a shift of the solubilization... 

A major effect of cholesterol on the conformation of apoE was revealed by comparing the conformation on DMPC discs, on HDLc, and on spherical artificial microemulsion particles by circular dichroism (Mims et ai, 1990). Conformational differences of apoE on different types of particles also were demonstrated using NMR to probe lysyl microenvironments. When the apoE lysyl residues were labeled by reductive methylation with [ C]formaldehyde to allow detection, the lysyl microenvironments manifested dramatic differences on a discoidal particle compared to spherical particles (S. Lund-Katz et aL, 1993). On spherical particles, two lysine microenvironments were observed, but on discoidal particles eight peaks were observed (apoE has 12 lysyl residues). These results indicate that apoE structure differs significantly on the two lipid surfaces. In a systematic study of the effect of the particle lipid composition on the conformation of apoE, conformation was shown to be affected by a number of parameters (Mims et ai, 1990). The a-helical content was lower when apoE was bound to a spherical particle compared to a discoidal particle. It was concluded that this probably reflects the different ways in which the amphipathic helices interact with phospholipid on the two particles. With discoidal particles the interaction is primarily with phospholipid acyl side chains, whereas with spherical particles the interaction is with polar phospholipid head groups. In addition, the conformation of apoE was influenced by the diameter of the microemulsion particle and possibly by the order/ disorder of the lipid components. 

In this article we describe the phase behavior of a microemulsion system chosen for the free radical polymerization of acrylamide within near-critical and supercritical alkane continuous phases. The effects of pressure, temperature, and composition on the phase behavior all influence the choice of operating parameters for the polymerization. These results not only provide a basis for subsequent polymerization studies, but also provide data on the properties of reverse micelles formed in supercritical fluids from nonionic surfactants. 

This section describes how to use Hand s rule to represent binodal curves and tie lines. The surfactant-oil-water phase behavior can be represented as a function of effective salinity after the binodal curves and tie lines are described. Binodal curves and tie lines can be described by Hand s rule (Hand, 1939), which is based on the empirical observation that equilibrium phase concentration ratios are straight lines on a log-log scale. Figures 7.15a and 7.15b show the ternary diagram for a type II(-) environment with equilibrium phases numbered 2 and 3 and the corresponding Hand plot, respectively. The line segments AP and PB represent the binodal curve portions for phase 2 and phase 3, respectively, and the curve CP represents the tie line (distribntion cnrve) of the indicated components between the two phases. Cy is the concentration (volnme fraction) of component i in phase) (i or j = 1, 2, or 3), and 1, 2, and 3 represent water, oil, and microemulsion, respectively. As the salinity is increased, the type of microemulsion is changed from type II(-) to type III to type II(-i-). C, represents the total amount of composition i. 

Figure 8.2 Relative detergency of cosmetic soil with 3 wt.% silicone resin in a series of microemulsions containing DC at 25°C. (a) Effect of DC concentration. The composition change corresponds to that from point p to q in Fig. 8.1. Concentration of ethanol is 12 wt.%. (b) Effect of ethanol concentration. The composition change corresponds to that from point r to s in Fig. 8.1. Concentration of DC is 6 wt.%. (c) Effect of composition change along the solubilisation limit from the point t to s in Fig. 8.1. Dashed lines represent the phase boundaries. (From Ref. [1 ], reprinted with permission of JOCS.)...

Joubran, R.F., Cornell, D.G. and Parris, N. (1993) Microemulsions of triglyceride and non-ionic surfactant-effect of temperature and aqueous phase composition. Colloid Surf. A, 80, 153— 157. 

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