Interfacial tension sodium chloride

Fig. III-9. Representative plots of surface tension versus composition, (a) Isooctane-n-dodecane at 30°C 1 linear, 2 ideal, with a = 48.6. Isooctane-benzene at 30°C 3 ideal, with a = 35.4, 4 ideal-like with empirical a of 112, 5 unsymmetrical, with ai = 136 and U2 = 45. Isooctane-

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

Effect of NaCI Concentration. The presence of surfactant in brine can have a dramatic effect on crude oil-aqueous surfactant tensions even at elevated temperatures r5,211. Figure 5 shows that the effect of sodium chloride concentration on Athabasca bitumen-D20 interfacial tensions measured at constant surfactant... 

Chan, M. Yen, T.F. Role of Sodium Chloride in the Lowering of Interfacial Tension Between Crude Oil and Alkaline Aqueous Solution, Fuel, 1981, 60, 552. 

R. Aveyard, B.P. Binks, S. Clark, and J. Mead Interfacial Tension Minima in Oil-Water-Surfactant Systems. Behavior of Alkane-Aqueous Sodium Chloride Systems Containing Aerosol OT. J. Chem. Soc. Faraday Trans. I 82, 125 (1986). 

Aveyard R, Binks BP, Clark S, Mead J (1986) Interfacial tension minima in oU-water-siufactant systems. Behavior of alkane-aqueous sodium chloride systems containing AOT. J Chem Soc Faraday Trans 82 125-142... 

Surfactant Substance that adsorbs to surfaces or interfaces to reduce surface or interfacial tension may be used as wetting agent, detergent, or emulsifying agents Benzalkonium chloride, nonoxynol 10, oxtoxynol 9, polysorbate 80, sodium lauryl sulfate, sorbitan monopalmitate... 

In Fig. 10 the interfacial tension and the stability of concentrated emulsions containing styrene and an aqueous sodium chloride solution are plotted against the concentration of sodium chloride. The w/o concentrated emulsions are stable for both Span 20 and Span 80. When SDS was used as surfactant, the o/w concentrated emulsions were more unstable at 50 °C than the above w/o concentrated emulsions because the double layer repulsion between cells is shielded by the high ionic strength. With SDS, concentrated emulsions did not form at room temperature above a salt concentration of 1.2 moll-1 because of the salting-out effect. The o/w concentrated emulsion did not form at all at 25 °C when Span 20 was employed as surfactant. 

In Fig. 10.12(a), the phase behaviour in the short float is shown. The three-phase state of the respective systems is located near the degreasing temperature T = 30°C. Efficient degreasing is a result of the ultra-low interfacial tension between water and fat. Upon diluting the short float with pure water the salt mass fraction in the water phase is effectively reduced from e = 0.21 to e = 0.07. Sodium chloride belongs to the group of lyotropic salts. When the salt mass fraction is reduced the hydration of the surfactant head... 

Using one of the pure alkyl aryl sulfonates with water, sodium chloride and decane, we are investigating simultaneously the phase behavior, the structure of the phases, and the interfacial tensions between them. Ultralow tensions are observed in this system (10), and it is important to know why they occur, when they do (13). Our first aim is to establish the equilibrium phase diagram of surfactant-water-decane as a function of... 

Precision of Measurements. Aliquots from a stock solution of 0.1 M sodium oleate (five months old) were used to prepare aqueous test solutions that were 0.01 M in sodium oleate and 0.1 M in sodium chloride pH 9 5 Interfacial tensions were measured against n-undecane without pre-equilibration. The second solution was made and measured one week after the first and the third solution two weeks after the first. The results in Table I... 

Precision of Interfacial Tension Measurements 0.01 M Sodium Oleate, 0.1 M Sodium Chloride pH 9 5 vs n-Undecane... 

Effect of Surfactant Concentration. Figure 3 compares results of alkane scans for three concentrations of sodium oleate at constant sodium chloride concentration and pH. The 0.002 M solution is derived from 95% oleic acid, the 0.01 M and the 0.1 M solutions are derived from 99% oleic acid. Both the magnitude and the alkane position of minimum interfacial tension (r = 11) are essentially concentration independent under these conditions. Wade, et al (12) reported a similar invariance in nm with a pure alkyl benzene sulfonate, although there was more change in the minimum value of interfacial tension with the sulfonate concentration than is observed with the carboxylate. The interfacial tension at for 0.01 M sodium oleate is in the range of the values of Table I. Very high interfacial tension (> 10 dynes/cm) was found at 0.0001 M sodium oleate in 0.1 M sodium chloride. 

Effect of Sodium Chloride Concentration. Figure b compares interfacial tensions of several different surfactant concentrations verses n-undecane in the presence of 0.1 M sodium chloride with values obtained without salt. Salt reduces the interfacial tension at all surfactant concentrations. Aqueous potassium oleate has a critical micelle concentration of 0.001 M (13). It could be inferred from Figure b that 0.001 M sodium oleate with no added salt is below the cmc, because of the high interfacial tension. If so, the much lower interfacial tension in the presence of 0.1 M sodium chloride stems from reduction of the cmc expected in the presence of added salt (lb). 

In Figure b9 interfacial tensions at 0.01 and 0.1 M sodium oleate and 0.1 M sodium chloride are higher than in Figure 3. However, the desired surfactant concentration in Figure U was obtained by dissolving the required quantity of sodium oleate and pH was not controlled. Data from Figure b are not directly comparable to Figure 3 for this reason. 

Table II illustrates the effect of varying the sodium chloride concentration on interfacial tension for one surfactant concentration. Between 0.01 and 0.2 M sodium chloride there appears to be a small decrease in interfacial tension. Increasing the...

Figure 13 exhibits both interfacial tension and electrophoretic mobility for the Huntington Beach Field crude oil against sodium orthosilicate containing no sodium chloride. The interfacial tension values are observed to be higher for the non-equilibrated sample in this case than for the caustic system reported in Figure 12. The minimum interfacial tension of 0.01 dynes/cm occurs at about 0.2% sodium silicate as opposed to a value of less than 0.002 dyne/cm at about 0.06% NaOH. It is interesting to note, however, that the maximum electrophoretic mobility is the same for the two systems. Once again, it should be noted that a maximum in electrophoretic mobility does not correspond to a minimum in interfacial tension for those samples which contained no sodium chloride.

In general, their work indicates that the surfactant partition coefficient between the oil phase and the excess brine phase is unity at the optimal parameter value. Their work indicates that there is a strong similarity between the interfacial tension behavior of low concentration systems and those of high concentration systems. Bansal and Shah (104) also showed that the salt tolerance of surfactant systems can be extended to rather high salt concentrations by mixing ethoxylated sulfonates with the usual petroleum sulfonate materials. An optimal salinity as high as 32% sodium chloride was observed in one of the mixed systems which was also characterized by very low oil-water interfacial tensions. 

Emulsions containing 5 wt % TRS 10-410, 3 wt % isobutanol, sodium chloride (X %), water and equal volume of dodecane oil were prepared by sonication and by hand-shaking. The coalescence behavior of emulsions was studied for hand-shaken as well as sonicated systems. In general, sonicated emulsions required a longer time for phase separation as compared to hand-shaken systems. It was observed that for both the cases, the coalescence rate at room temperature (25°C) was maximum at the optimal salinity (1.5% NaCl) while interfacial tension was minimum at this salinity. 

Density, viscosity and interfacial tension data of the equilibrated phases corresponding to an aqueous to oil ratio of 1 1 are presented in Table 1. Table 2 is the summary of the number of equilibrium phases present at 35 C for different aqueous to oil ratios and sodium chloride concentrations. It should be noted that the 1 1 system having 2% NaCl at 35°C represents a three phase system. However, at 25°C the same system gave only two phases. 

The selected electrol5rte composition is based on the effects of the various components on the physicochemical properties of the molten electrolyte. However, in some cases, the MgCl2 feedstock contains small amounts of another metal chloride such as KCl. Electrical conductivity, density, vapor pressure, interfacial tension, and metal solubility are important properties. A typical composition can be 45 % NaQ, 35 % CaCl2, 10 % KCl, and 10 % MgCl2. The content of MgCl2 must not be too low to avoid codeposition of sodium, although some sodium will always be deposited at a low activity. 

Motomura et al. [100] measured the interfacial tension of aqueous sodium perfluorooctanoate against hexane as a function of temperature around cnic. The entropy and energy of adsorption were found to be higher for sodium perfluorooctanoate than for dodecylammonium chloride or sodium dodecyl sulfate. The... 

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