Interfacial tension chloride system

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. 

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. 

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... 

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. 

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... 

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.

Interfacial tension is an important property in the process design of liquid-liquid processes. The decrement of interfacial tension between both phases leads to an increased interfacial area [135]. Because the volumetric rate of extraction was found to be dependent on the interfacial area, interfacial tension data are useful in understanding the effect of interfacial area on the volumetric rate of extraction and overall reaction rates for a PT-catalyzed reaction. Dutta and Patil [136] reported that the effect on the interfacial tension of the water/toluene system has been studied in the presence of four PT catalysts, i.e., tricaprylmethyl ammonium chloride, hexadecyltrimethyl ammonium chloride, hexadecy-trimethyl ammonium bromide, and hexadecyltributyl phosphonium bromide. The decrease in interfacial tension by surfactants increases the interfacial contact area, enhancing the volumetric rate of extraction. 

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. 

When measuring the surface pressure isotherms, it is desirable that the values of the interfacial tension are not time-dependent. In this case, in the interfacial region a state is reached close to the equilibrium for the surfactant distribution between the phases [55]." If the surfactant is soluble in both phases, one should be careful in calculating the surface excess in such systems, and the surfactant distribution coefficient should be determined independently. For instance, trioctylmethylammonium chloride (Oct3MeNCl) in the benzene-water system has a distribution coefficient of the order of 10 [57]. The surface pressure isotherms at the benzene-water interface are almost independent of the phase in which Oct3MeNCl is dissolved. It means that in both cases Oct3MeNCl is almost completely located in the benzene phase, i.e. the surfactant distribution equilibrium is reached at the interface. Apparently, the anomalies in the... 

Using a drop time method for the determination of interfacial tension and a four-electrode potentiostat to polarize the interface, Kakiuchi and Senda measured electrocapillary curves for ideally polarized systems, in particular for the interface between an aqueous solution of lithium chloride and a solution in nitrobenzene of TBATPB. They showed that the surface charge density, Q, obtained by differentiation of the electrocapillary curve was equal to that calculated from the integration of the corresponding differential capacity versus potential curves. This demonstrated the validity of the Lippmann equation for the polarized ITIES ... 

The addition of a surfactant to systems with particle monolayers at oil/ water interfaces allows us to determine the way in which the monolayer collapse pressure, II,., varies with the interfacial tension, of the (particle-free) oil/water interface [23]. This, in turn, can give us some feel for the physical origin of particle monolayer collapse. Quite remarkably, we hnd that there is a very close correspondence between He and yow, as seen in Fig. 23. The tensions of the oil/water interface have been varied by addition of a range of concentrations of fom different smfactants (including anionic, cationic, and nonionic), namely CTAB, SDS, cetylpyridinium chloride (CPC), and the pure sugar surfactant decyl )8-glucoside (DBG). 

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