Interfacial tension formation

Thus, adding surfactants to minimize the oil-water and solid-water interfacial tensions causes removal to become spontaneous. On the other hand, a mere decrease in the surface tension of the water-air interface, as evidenced, say, by foam formation, is not a direct indication that the surfactant will function well as a detergent. The decrease in yow or ysw implies, through the Gibb s equation (see Section III-5) adsorption of detergent. 

Atomization. A gas or Hquid may be dispersed into another Hquid by the action of shearing or turbulent impact forces that are present in the flow field. The steady-state drop si2e represents a balance between the fluid forces tending to dismpt the drop and the forces of interfacial tension tending to oppose distortion and breakup. When the flow field is laminar the abiHty to disperse is strongly affected by the ratio of viscosities of the two phases. Dispersion, in the sense of droplet formation, does not occur when the viscosity of the dispersed phase significantly exceeds that of the dispersing medium (13). 

Critical Micelle Concentration. The rate at which the properties of surfactant solutions vary with concentration changes at the concentration where micelle formation starts. Surface and interfacial tension, equivalent conductance (50), dye solubilization (51), iodine solubilization (52), and refractive index (53) are properties commonly used as the basis for methods of CMC determination. 

Properties of Component Phases As discussed in the preceding subsection, dispersions of gases in liquids are affected by the viscosity of the hquid, the density of the liquid and of the gas, and the interfacial tension between the two phases. They also may be affected directly by the composition of the hquid phase. Both the formation of bubbles and their behavior during their lifetime are influenced by these quantities as weh as by the me(manical aspects of their environment. 

The entropy of formation of the interface was calculated from the temperature coefficient of the interfacial tension.304 The entropy of formation has been found to increase with the nature of the electrolyte in the same sequence as the single cation entropy in DMSO.108, 09,329 The entropy of formation showed a maximum at negative charges. The difference in AS between the maximum and the value at ff=ocan be taken as a measure of the specific ordering of the solvent at the electrode/solution interface. Data 108,109304314 have shown that A(AS) decreases in the sequence NMF > DMSO > DMF > H90 > PC > MeOH. 

Figure 17. Energy for the nucleation of a surface film on metal electrode. M, metal OX, oxide film EL, electrolyte solution. Aj is the activation barrier for the formation of an oxide-film nucleus and rj is its critical radius. 7 a is the interfacial tension of the metal-electrolyte interface, a is the interfacial tension of the film-electrolyte interface. (From N. Sato, J. Electro-chem. Soc. 129, 255, 1982, Fig. 5. Reproduced by permission of The Electrochemical Society, Inc.)...

Acid flooding can be successful in formations that are dissolvable in the particular acid mixture, thus opening the pores. Hydrochloric acid is common, in a concentration of 6% to 30%, sometimes also with hydrofluoric acid and surfactants added (e.g., isononylphenol) [130,723]. The acidic environment has still another effect on surfactants. It converts the sulfonates into sulfonic acid, which has a lower interfacial tension with oil. Therefore a higher oil forcing-out efficiency than from neutral aqueous solution of sulfonates is obtained. Cyclic injection can be applied [4,494], and sulfuric acid has been described for acid treatment [25,26,1535]. Injecting additional aqueous lignosulfonate increases the efficiency of a sulfuric acid treatment [1798]. 

Optimizing the formulation of micellar surfactant solutions used for enhanced oil recovery consists of obtaining interfacial tensions as low as possible in multiphase systems, which can be achieved by mixing the injected solution with formation fluids. The solubilization of hydrocarbons by the micellar phases of such systems is linked directly to the interfacial efficiency of surfactants. Numerous research projects have shown that the amount of hydrocarbons solubilized by the surfactant is generally as great as the interfacial tension between the micellar phase and the hydrocarbons. The solubilization of crude oils depends strongly on their chemical composition [155]. 

The B. licheniformis JF-2 strain produces a very effective surfactant under conditions typical of oil reservoirs. The partially purified biosurfactant from JF-2 was shown to be the most active microbial surfactant found, and it gave an interfacial tension against decane of 0.016 mN/m. An optimal production of the surfactant was obtained in cultures grown in the presence of 5% NaCl at a temperature of 45° C and pH of 7. TTie major endproducts of fermentation were lactic acid and acetic acid, with smaller amounts of formic acid and acetoin. The growth and biosurfactant formation were also observed in anaerobic cultures supplemented with a suitable electron acceptor, such as NaNO3[1106]. 

Demulsifiers (specifically, oil spill demulsifiers) can be applied to oil spills in low concentrations. They prevent mousse formation for significant periods of time and cause a large reduction in oil-water interfacial tension. The best of these was found to prevent emulsification at dosages as low as 1 part inhibitor to 20,000 parts of fresh oil at 20° C [273]. At dosages of 1 1000, at temperatures higher than 10° C, the chemical also results in significant and rapid dispersion of the oil. For very low temperatures or highly weathered oil, the performance of the chemical falls off sharply. 

The interaction between the adsorbed molecules and a chemical species present in the opposite side of the interface is clearly seen in the effect of the counterion species on the HTMA adsorption. Electrocapillary curves in Fig. 6 show that the interfacial tension at a given potential in the presence of the HTMA ion adsorption depends on the anionic species in the aqueous side of the interface and decreases in the order, F, CP, and Br [40]. By changing the counterions from F to CP or Br, the adsorption free energy of HTMA increase by 1.2 or 4.6 kJmoP. This greater effect of Br ions is in harmony with the results obtained at the air-water interface [43]. We note that this effect of the counterion species from the opposite side of the interface does not necessarily mean the interfacial ion-pair formation, which seems to suppose the presence of salt formation at the boundary layer [44-46]. A thermodynamic criterion of the interfacial ion-pair formation has been discussed in detail [40]. 

It follows from the above that the mechanism for electrical potential oscillation across the octanol membrane in the presence of SDS would most likely be as follows dodecyl sulfate ions diffuse into the octanol phase (State I). Ethanol in phase w2 must be available for the transfer energy of DS ions from phase w2 to phase o to decrease and thus, facilitates the transfer of DS ions across this interface. DS ions reach interface o/wl (State II) and are adsorbed on it. When surfactant concentration at the interface reaches a critical value, a surfactant layer is formed at the interface (State III), whereupon, potential at interface o/wl suddenly shifts to more negative values, corresponding to the lower potential of oscillation. With change in interfacial tension of the interface, the transfer and adsorption of surfactant ions is facilitated, with consequent fluctuation in interface o/ wl and convection of phases o and wl (State IV). Surfactant concentration at this interface consequently decreased. Potential at interface o/wl thus takes on more positive values, corresponding to the upper potential of oscillation. Potential oscillation is induced by the repetitive formation and destruction of the DS ion layer adsorbed on interface o/wl (States III and IV). This mechanism should also be applicable to oscillation with CTAB. Potential oscillation across the octanol membrane with CTAB is induced by the repetitive formation and destruction of the cetyltrimethylammonium ion layer adsorbed on interface o/wl. Potential oscillation is induced at interface o/wl and thus drugs were previously added to phase wl so as to cause changes in oscillation mode in the present study. 

For the case of a thread at rest, the initial growth of a disturbance can be relatively well characterized by linear stability theory. In the initial stages, the deformation of the thread follows the growth of the fastest growing disturbance (Tomotika, 1935). Eventually the interfacial tension driven flow becomes nonlinear, leading to the formation of the smaller satellite drops (Tjahjadi et al., 1992). 

Isaacs and Smolek [211 observed that low tensions obtained for an Athabasca bitumen/brine-suIfonate surfactant system were likely associated with the formation of a surfactant-rich film lying between the oil and water, which can be hindered by an increase in temperature. Babu et al. [221 obtained little effect of temperature on interfacial tensions however, values of about 0.02 mN/m were obtained for a light crude (39°API), and were about an order of magnitude lower than those observed for a heavy crude (14°API) with the same aqueous surfactant formulations. For pure hydrocarbon phases and ambient conditions, it is well established that the interfacial tension behavior is dependent on the oleic phase [15.231 In general, interfacial tension values of crude oiI-containing systems are considerably higher than the equivalent values observed with pure hydrocarbons. 

In n-octane/aqueous systems at 27°C, TRS 10-80 has been shown to form a surfactant-rich third phase, or a thin film of liquid crystals (see Figure 1), with a sharp interfacial tension minimum of about 5x10 mN/m at 15 g/L NaCI concentration f131. Similarly, in this study the bitumen/aqueous tension behavior of TRS 10-80 and Sun Tech IV appeared not to be related to monolayer coverage at the interface (as in the case of Enordet C16 18) but rather was indicative of a surfactant-rich third phase between oil and water. The higher values for minimum interfacial tension observed for a heavy oil compared to a pure n-alkane were probably due to natural surfactants in the crude oil which somewhat hindered the formation of the surfactant-rich phase. This hypothesis needs to be tested, but the effect is not unlike that of the addition of SDS (which does not form liquid crystals) in partially solubilizing the third phase formed by TRS 10-80 or Aerosol OT at the alkane/brine interface Til.121. 

The interfacial tension-temperature relationships at various CaCL concentrations for Karamay crude in a Sun Tech IV (5 g/L) and NaCI (10 g/L) solution are shown in Figure 9. For 0, 0.025 and 0.1 g/L Ca, an increase in interfacial tension with temperature was observed. The interfacial tension values above 150°C were about the same for these concentrations. At temperatures below 100°C, the effect of Ca was to increase interfacial tension, probably by hindering the formation of a surfactant-rich phase. This is consistent with the detrimental effect or light oil/brine interfacial tensions (increase from about 10 3 to about 10 1) reported by Kumar et al. T371. ... 

Figure 10 Effect of temperature on the interfacial tension of Karamay crude in reservoir formation water and synthetic br ine.

Since Thin Film Spreading Agents do not produce ultralow interfacial tensions, capillary forces can trap oil in pore bodies even though the oil has been displaced from the surface of the porous medium. Therefore, recovery of incremental oil is dependent on the formation of an oil bank. Muggee, F. D. U.S. Patent 3 396 792, 1968. 

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