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Physical surfactant solutions

Physical and ionic adsorption may be either monolayer or multilayer (12). Capillary stmctures in which the diameters of the capillaries are small, ie, one to two molecular diameters, exhibit a marked hysteresis effect on desorption. Sorbed surfactant solutes do not necessarily cover ah. of a sohd iaterface and their presence does not preclude adsorption of solvent molecules. The strength of surfactant sorption generally foUows the order cationic > anionic > nonionic. Surfaces to which this rule apphes include metals, glass, plastics, textiles (13), paper, and many minerals. The pH is an important modifying factor in the adsorption of all ionic surfactants but especially for amphoteric surfactants which are least soluble at their isoelectric point. The speed and degree of adsorption are increased by the presence of dissolved inorganic salts in surfactant solutions (14). [Pg.236]

Other detection methods are based on optical transmittance [228-231], Alcohol sulfates have been determined by spectrophotometric titration with barium chloride in aqueous acetone at pH 3 and an indicator [232] or by titration with Septonex (carbethoxypentadecyltrimethylammonium bromide) and neutral red as indicator at pH 8.2-8.4 and 540 nm [233]. In a modified two-phase back-titration method, the anionic surfactant solution is treated with hyamine solution, methylene blue, and chloroform and then titrated with standard sodium dodecyl sulfate. The chloroform passing through a porous PTFE membrane is circulated through a spectrometer and the surfactant is analyzed by determining the absorbance at 655 nm [234]. The use of a stirred titration vessel combined with spectrophotometric measurement has also been suggested [235]. Alternative endpoint detections are based on physical methods, such as stalag-mometry [236] and nonfaradaic potentiometry [237]. [Pg.280]

The average Nusselt number, Nu, is presented in Fig. 4.10a,b versus the shear Reynolds number, RCsh- This dependence is qualitatively similar to water behavior for all surfactant solutions used. At a given value of Reynolds number, RCsh, the Nusselt number, Nu, increases with an increase in the shear viscosity. As discussed in Chap. 3, the use of shear viscosity for the determination of drag reduction is not a good choice. The heat transfer results also illustrate the need for a more appropriate physical parameter. In particular. Fig. 4.10a shows different behavior of the Nusselt number for water and surfactants. Figure 4.10b shows the dependence of the Nusselt number on the Peclet number. The Nusselt numbers of all solutions are in agreement with heat transfer enhancement presented in Fig. 4.8. The data in Fig. 4.10b show... [Pg.160]

Surfactant Solutions New Methods of Investigation, edited by Raoul Zana Nonionic Surfactants Physical Chemistry, edited by Martin J. Schick Microemulsion Systems, edited by Henri L Rosano and Marc Clausse Biosurfactants and Biotechnology, edited by Naim Kosaric, W. L. Cairns, and Neil C. C. Gray... [Pg.4]

In a previous publication ( ), results were presented on the micellar properties of binary mixtures of surfactant solutions consisting of alkyldimethylamine oxide (C12 to Cig alkyl chains) and sodium dodecyl sulfate. It was reported that upon mixing, striking alteration in physical properties was observed, most notably in the viscosity, surface tension, and bulk pH values. These changes were attributed to 1) formation of elongated structures, 2) protonation of amine oxide molecules, and 3) adsorption of hydronium ions on the mixed micelle surface. In addition, possible solubilisation of a less soluble 1 1 complex, form between the protonated amine oxide and the long chain sulfate was also considered. [Pg.116]

The temperature (or salinity) at which optimal temperature (or optimal salinity), because at that temperature (or salinity) the oil—water interfacial tension is a minimum, which is optimum for oil recovery. For historical reasons, the optimal temperature is also known as the HLB (hydrophilic—lipophilic balance) temperature (42,43) or phase inversion temperature (PIT) (44). For most systems, all three tensions are very low for Tlc < T < Tuc, and the tensions of the middle-phase microemulsion with the other two phases can be in the range 10 5—10 7 N/m. These values are about three orders of magnitude smaller than the interfacial tensions produced by nonmicroemulsion surfactant solutions near the critical micelle concentration. Indeed, it is this huge reduction of interfacial tension which makes micellar-polymer EOR and its SEAR counterpart physically possible. [Pg.151]

Solutions of highly surface-active materials exhibit unusual physical properties. In dilute solution the surfactant acts as a normal solute (and in the case of ionic surfactants, normal electrolyte behaviour is observed). At fairly well defined concentrations, however, abrupt changes in several physical properties, such as osmotic pressure, turbidity, electrical conductance and surface tension, take place (see Figure 4.13). The rate at which osmotic pressure increases with concentration becomes abnormally low and the rate of increase of turbidity with concentration is much enhanced, which suggests that considerable association is taking place. The conductance of ionic surfactant solutions, however, remains relatively high, which shows that ionic dissociation is still in force. [Pg.84]

Figure 3.21 Changes in physical properties of an aqueous surfactant solution at concentrations near the critical micelle concentration, shown here as a narrow range of concentrations. Figure 3.21 Changes in physical properties of an aqueous surfactant solution at concentrations near the critical micelle concentration, shown here as a narrow range of concentrations.
Critical micelle concentration (cmc) Concentration at which the physical properties of a surfactant solution show an abrupt change. [Pg.504]

Figure 2.2 Physical properties of aqueous surfactant solution as a function of surfactant concentration. Figure 2.2 Physical properties of aqueous surfactant solution as a function of surfactant concentration.
An early attempt to correlate the physical properties of surfactant solutions and their foams with oil recoveries was performed by Deming in 1964 (50). Deming concluded that high foaming ability favored high displacement efficiency, but that high foam stability were not required for high displacement efficiency. Bernard and Holm found that oil substantially decreased the abilities of most surfactants to reduce aqueous permeabilities, but that some surfactants remained effective even in the presence of oil (52,53). [Pg.14]

Physical Chemistry of Surfactant Solutions and the Process of Micellisation... [Pg.27]

Physical Chemistry of Surfactant Solutions and the Process of Micellisation 29 Table 3.1 Critical micelle concentration (cmc) of surfactants. [Pg.29]

Although, the spherical micelle model accounts for many of the physical properties of solutions of surfactants, a number of phenomena remain unexplained, without considering other shapes. For example, McBain [9] suggested the presence of two types of micelle - spherical and lamellar - in order to account for the drop in molar conductance of surfactant solutions. The lamellar micelles are neutral and hence they account for the reduction in conductance. Later, Harkins et al. [Pg.32]

According to this model a clear discontinuity in the physical property of a surfactant solution, such as surface tension and turbidity, should be observed at the cmc. This is not always found experimentally and the cmc is not a sharp break point. [Pg.36]


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