Interfacial tension table

The simplest way to understand the difference in the interfacial stractures mentioned above will be to consider the relevant interfacial tension, since an interfacial tension (mN m ) is equivalent to the interfacial free energy (mJ m ) [27]. As shown in Table 12.3, the interfacial free energy in the water/CCU system (44.5 mJ m"" ) is higher than that in the water/DCE system (27.9 mJ m ). This implies that, since the energy necessary to construct a water/CCU interface is larger than that for a water/DCE interface, the former is likely to construct a molecularly sharp interface. Therefore, interfacial roughness becomes smaller with increasing the interfacial tension (Table 12.3). 

Sometimes the mutual solubility of a solvent pair of interest can easily be decreased by adding a third component. For example, it is common practice to add water to a solvent system containing a water-miscible organic solvent (the polar phase) and a hydrophobic organic solvent (the nonpolar phase). A typical example is the solvent system (methanol + water) + dichloromethane. An anhydrous mixture of methanol and dichloromethane is completely miscible, but adding water causes phase splitting. Adjusting the amount of water added to the polar phase also may be used to alter the K values for the extraction, density difference, and interfacial tension. Table 15-5 lists some common examples of solvent systems of this type. These systems are common candidates for fractional extractions. 

Contact Angle and SAXS Studies. The contact angles which developed at the junction of flocculated oil droplets, illustrated in Figure 2, can be used together with the measured interfacial tensions (Table 1) in a vector diagram to demonstrate that the interfacial tensions on the outer surface of the oil drops (yqw) are appreciably greater than the interfacial tensions (YqW) In the plane of contact between drops ... 

The maximum amount of surfactant, F , that can be delivered at interfaces (water-air or water-oil) depends on the ability of molecules to pack and is an important parameter for practical applications, such as detergency applications, in determining such properties as foaming and emulsification. The maximum value of the surface excess concentration is commonly called the effectiveness of adsorption of the surfactant. Extensive studies have been devoted to compare various molecular structures of surfactants for their effectiveness in reducing the interfacial tension. Table 1 provides values of r , in mol/m, and the area per molecule at the interface at maximum adsorption aZ, in A, for representative surfactants. 

Using appropriate data from Table II-9, calculate the water-mercury interfacial tension using the simple Girifalco and Good equation and then using Fowkes modification of it. 

The system of Fig. 15-38 is one of high interfacial tension, so that the heights of transfer units are relatively high and stage efficiency low. For systems of low interfacial tension, on the other hand, stage efficiencies may be very much improved. Table 15-8 lists sources of mass-transfer data. 

Compatibility and various other properties such as morphology, crystalline behavior, structure, mechanical properties of natural rubber-polyethylene blends were investigated by Qin et al. [39]. Polyethylene-b-polyiso-prene acts as a successful compatibilizer here. Mechanical properties of the blends were improved upon the addition of the block copolymer (Table 12). The copolymer locates at the interface, and, thus, reduces the interfacial tension that is reflected in the mechanical properties. As the amount of graft copolymer increases, tensile strength and elongation at break increase and reach a leveling off. 

TABLE 19 Efficiencies and Effectiveness of Water-Air Interfacial Tension Reduction of Alcohol and Alcohol Ether Sulfates... 

The presence of calcium and magnesium ions increases the adsorption of the surfactants at the water-air interface and leads to a corresponding lowering of the surface tension at the CMC as shown by the data in Table 4. A C16 branched AOS gives a lower surface tension than a linear C16 AOS this too is in agreement with other model studies and theoretical predictions [42, and Sec. 2 on interfacial tension). 

TABLE 10 Effect of Hydrophobe Carbon Number on Interfacial Tension of Olefinsulfonates ... 

TABLE 12 Comparison of Interfacial Tension Properties of a- and Internal Olefinsulfonates8... 

TABLE 13 Effect of Di Monosulfonate Ratio on Interfacial Tension of Olefinsulfonate Solutions3... 

Effect of Aqueous Phase Salinity and pH on Interfacial Tension. Comparison of the first two entries in Table 14 shows that an increase in AOS 2024 solvent salinity from 0 to 3% NaCl results in a significant decrease in IFT. This suggests that the optimum salinity of this AOS 2024 sample is closer to 3% NaCl than to 0%. 

Decreasing the pH of 3% NaCl (entries 2 and 3, Table 14) could decrease neutralization of crude oil organic acids. This neutralization increases both aqueous phase salinity and effective surfactant concentration. A lower effective surfactant concentration at pH 8 could account for the increased interfacial tension value. However, a similar pH change does not reduce IFT when the surfactant is AOS 1618 with a much lower di monosulfonate ratio (entries 6 and 7, Table 14). 

The better interaction observed with the unmodifled clay was also explained in terms of surface energy. The values of surface energy of the fluoroelastomer and the clays, along with work of adhesion, spreading coefficient and interfacial tension are reported in Table 2.4. 

When the two phases separate the distribution of the solvent molecules is inhomogeneous at the interface this gives rise to an additional contribution to the free energy, which Henderson and Schmickler treated in the square gradient approximation [36]. Using simple trial functions, they calculated the density profiles at the interface for a number of system parameters. The results show the same qualitative behavior as those obtained by Monte Carlo simulations for the lattice gas the lower the interfacial tension, the wider is the interfacial region in which the two solvents mix (see Table 3). 

TABLE 3 Interfacial Widths, Bulk Composition, and Interfacial Tension in erg cm at the Interface Between Two Dipolar Liquids [5]. x Denotes the Mole Fraction of Solvent Si in Phase i... 

Surfactants have been widely used to reduce the interfacial tension between oil and soil, thus enhancing the efficiency of rinsing oil from soil. Numerous environmentally safe and relatively inexpensive surfactants are commercially available. Table 18.6 lists some surfactants and their chemical properties.74 The data in Table 18.6 are based on laboratory experimentation therefore, before selection, further field testing on their performance is recommended. The Texas Research Institute75 demonstrated that a mixture of anionic and nonionic surfactants resulted in contaminant recovery of up to 40%. A laboratory study showed that crude oil recovery was increased from less than 1% to 86%, and PCB recovery was increased from less than 1% to 68% when soil columns were flushed with an aqueous surfactant solution.74-76... 

Table III Interfacial tension data for the Athabasca bitumen/D20 and Enordet C1618 (2 g/L) system as a function of NaCI concentration and temperature...

The results show that although all the demulsifiers lower the shear viscosity, they differ widely in their demulsification effectiveness, as measured by the residual bottom sediment and water content (Figure 1) (BS and W%) of the dehydrated oil. For example, the demulsifier 0P1, although it lowers both the equilibrium interfacial tension (Figure 2) and the shear viscosity (Table I), nevertheless is ineffective. This is because it takes a much longer time for the oil-water interfacial tension to reach equilibrium with 0P1 than with PI or P2 (see later). 

In general, there is no correlation between the tension and the shear viscosity of an oil-water interface. However, for systems containing demulsifiers, a low interfacial tension (IFT) often leads to a lowering of the shear viscosity. Demulsifiers, in general, are large disordered molecules and when they are present at the interface they create a mobile, low viscosity zone. However, a low IFT is not a necessary condition for a low viscosity interface. A large demulsifier such as PI, although not very surface active, can still lower the shear viscosity to a very low value (Table I). 

Cosolvent flooding is an experimental method for removing DNAPLs trapped below the water table. It involves injecting a highly concentrated aqueous mixture of solvents, such as alcohols, a chemical that is miscible with either phase in the aquifer. This process has the tendency to increase or enhance DNAPL (or LNAPL) solubility greatly, and to reduce the NAPL-water interfacial tension. Depending upon the phase behavior between the cosolvent and NAPL, a cosolvent flood can be developed to emphasize either enhanced dissolution (i.e., use of methane flooding for the dissolution of TCE) or NAPL mobilization. 

The film pressure values for the detergency system are also listed in Table 2. These quantities represent the difference in interfacial tension between two pure phases and the interfacial tension of the same two phases which are at saturation equilibrium with the third phase. Since the PEG fiber surface was assumed insoluble in either the bath or soil, = 0. 

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