Interfacial tension 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. 

This potential depends on the interfacial tension am of a passivated metal/electrolyte interface shifting to the lower potential side with decreasing am. The lowest film breakdown potential AEj depends on the surface tension of the breakdown site at which the film-free metal surface comes into contact with the electrolyte. A decrease in the surface tension from am = 0.41 J m"2 to nonmetallic inclusions on the metal surface, will cause a shift of the lowest breakdown potential by about 0.3 V in the less noble direction. 

A similar technique, the so-called spontaneous emulsification solvent diffusion method, is derived from the solvent injection method to prepare liposomes [161]. Kawashima et al. [162] used a mixed-solvent system of methylene chloride and acetone to prepare PLGA nanoparticles. The addition of the water-miscible solvent acetone results in nanoparticles in the submicrometer range this is not possible with only the water-immiscible organic solvent. The addition of acetone decreases the interfacial tension between the organic and the aqueous phase and, in addition, results in the perturbation of the droplet interface because of the rapid diffusion of acetone into the aqueous phase. 

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... 

The interfacial tension of mixed adsorbed films of 1-octadecanol and dodecylammonium chloride has been measured as a function of temperature at various bulk concentrations under atmospheric pressure. The transition interfacial pressure of 1-octadecanol film has been observed to increase with the addition of dodecylammonium chloride and then to disappear. The interfacial pressure vs mean area per adsorbed molecule curves have been illustrated at a constant mole fraction of adsorbed molecules. With the aid of the thermodynamic treatment developed previously, we find that the mutual interaction between 1-octadecanol and dodecylammonium chloride molecules in the expanded state is similar in magnitude to the interaction between the scime kind of film-forming molecules. 

It is interesting to employ the system consisting of mixed adsorbed film of 1-pctadecanol and dodecylammonium chloride because the former shows the phase transition from an expanded to a condensed state ( ). The interfacial tension was measured as a function of temperature at various bulk concentrations under atmospheric pressure and the molecular interaction between film-forming components was considered. 

Octadecanol was recrystallized from hexane after fractionation by vacuum distillation, and its purity was checked by gas-liquid chromatography. Dodecylammonium chloride was recrystallized from a mixture of ethanol and water, and its purity was confirmed by the fact that it had no minimum near the critical micelle concentration on the surface tension vs concentration curve. Hexane was distilled after passing through an activated alumina column. Water was distilled from alkaline permanganate solution of distilled water after refluxing for one day. The purity of hexane and water was confirmed by the value of the interfacial tension between them. 

The interfacial tension Y was measured as a function of temperature T, molality of 1-octadecanol in hexane, and molality of dodecylammonium chloride in water under atmospheric pressure. The molality was increased up to the solubility limit. 

Figure 1 shows the plots of the interfacial tension against temperature at various values for = 7.54 mmol kg". All the curves except for the concentrated solution of dodecylammonium chloride have a break point which represents the phase transition from the condensed to expanded state. The phase transition temperature lowers with increasing and disappears above a certain ni2 value. 

Taking into consideration that the solvents are practically immiscible and that 1-octadecanol and dodecylaimmonium chloride are soluble only in hexane and water respectively, the total differential of the interfacial tension Y can be expressed as a function of temperature T, pressure p, molality m, and molality as follows (4) ... 

It was previously shown that the formation of a stable emulsion of methylene chloride in water was vital for the successful formation of individual microspheres [4,9]. Two main factors played an important role in the emulsification of methylene chloride in water and influenced the microsphere size the interfacial tension of the methylene chloride droplets in the surrounding aqueous phase and the forces of shear within the fluid mass. The former tends to resist the distortion of droplet shape necessary for fragmentation into smaller droplets whereas the latter forces act to distort and ultimately to disrupt the droplets. The relationship between these forces largely determines the final size distribution of the methylene chloride in water emulsion which in turn controls the final size distribution of the solid microspheres formed. 

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. 

Fig. 2. Variation of interfacial tension at the point of zero charge with activity of lithium chloride. The solid line is calculated assuming the exclusion of lithium and chloride ions from the inner layer. (Reprinted from [52] with permission. Copyright The Chemical Society of Japan).

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.

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