Interfacial tension sodium chloride concentration

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... 

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). 

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...

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. 

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-

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 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. 

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. 

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