Conductivity with surfactants

For a cationic (CTABr) and an anionic (NaLS) surfactant in a variety of dipolar aprotic solvents, e.g., dimethyl sulfoxide, dimethyl formamide, the variation of conductance with surfactant concentration is characteristic of micellization, and critical micelle concentrations were reported, which tend to be higher than those in water, especially for CTABr [144]. 

Fig. 9.14 Change of specific conductance with surfactant concentration (DAPA = dodecylammonium perfluoroacetate). (Reproduced with permission from Ref. 275. Copyright by the American Chemical Society.)...

A study over a broader range of disulfonate monosulfonate ratios was then conducted with a series of AOS 2024 surfactants. Results are shown in Fig. 5. The carbon number and hydrophobe branching were held constant. The AS HAS ratio was 75 25. At a disulfonate monosulfonate ratio (D M) of 7 93, addition of less than 200 ppm calcium ion decreased solution transmittance to less than 10% of its initial value. When the disulfonate content of AOS 2024 was increased to 38 wt % (di monosulfonate ratio of 38 62), slightly more than 1000 ppm calcium ion was required to reduce solution transmittance to less than 10% of its initial value. When the surfactant consisted predominantly of disulfonate (di monosulfonate ratio of 84 16), the addition of more than 41,000 ppm calcium ion reduced the transmittance by less than 5% from its initial value. 

The use of electrochemical methods for the destruction of aromatic organo-chlorine wastes has been reviewed [157]. Rusling, Zhang and associates [166, 167] have examined a stable, conductive, bicontinuous surfactant/soil/water microemulsion as a medium for the catalytic reduction of different pollutants. In soils contaminated with Arochlor 1260, 94% dechlorination was achieved by [Zn(pc)] (H2pc=phthalocyanine) as a mediator with a current efficiency of 50% during a 12-h electrolysis. Conductive microemulsions have also been employed for the destruction of aliphatic halides and DDT in the presence of [Co(bpy)3]2+ (bpy=2,2 -bipyridine) [168] or metal phthalocyanine tetrasulfonates [169]. 

A screening study was conducted with samples from a Llobregat river WWTP in order to establish a better treatment for the removal of organic pollutants. Given that improvement of water quality is known to be achieved with the implementation of GAC filtration, the behaviour of surfactants (polyethoxylated nonylphenols, bromo-polyethoxylated nonylphenols) has been studied on seven different commercial GACs. These pollutants were efficiently removed using a bituminous coal-based GAC [38]. 

The reaction was first conducted with success on sucrose [82], The degree of substitution (DS) obtained was controlled by the reaction time. Thus, under standard conditions (0.05% Pd(OAc)2/TPPTS, NaOH (1 M)/iPrOH (5/1), 50 °C) the DS was 0.5 and 5 after 14 and 64 h reaction time, respectively. The octadienyl chains were hydrogenated quantitatively in the presence of 0.8-wt.% [RhCl(TPPTS)3] catalyst in a HjO-EtOH (50/10) mixture, yielding a very good biodegradable surfactant (surface tension of 25 mN m-1 at 0.005% concentration in water) [84]. Telomerization reaction was also conducted with success on other soluble carbohydrates such as fructose, maltose, sorbitol and /i-cyclodextrin. 

Pure Silica Ncinoparticles. Based on experiments conducted with the TEOS/ AOT/isooctane/water/ammonia system, and water-to-surfactant molar ratios in the range 5.7-15.8, Yamauchi et al. (20) prepared silica particles with diameters of 14-71 nm. Also using AOT, but with a different oil, i.e toluene, Espiard et al. 

When the synthesis procedure described above is conducted with Mo(OEt)5 in place of Nb(OEt), a new bronze material is formed.12-1 This material has an XRD d-spacing centered at 32 A. Attempts to remove the surfactant by acid washing led to complete loss of structure as determined by nitrogen adsorption and XRD. Attempts to stabilize the material by aging at higher temperature in order to promote further condensation in the walls led to a new blue material with a lamellar XRD pattern (d(100) = 34 A) that also... 

The synthesis of amphopropionates is thus similar to the amphoacetates except that, rather than sodium chloride being formed as a by-product, methanol often is. If made from methyl acrylate, there is usually about 5-7% methanol in the surfactant product. If alkylation is conducted with sodium acrylate, methyl acrylate is the more efficient alkylating agent. 

Rupture of emulsion bilayers. Experimental verification of the theory [399,402,403] of hole nucleation rupture of bilayer has also been conducted with emulsion bilayers [421]. A comparative investigation of the rupture of microscopic foam and emulsion bilayers obtained from solutions of the same Do(EO)22 nonionic surfactant has been carried out. The experiments were done with a measuring cell, variant B, Fig. 2.3, a large enough reservoir situated in the studied film proximity was necessary to ensure the establishment of the film/solution equilibrium. The emulsion bilayer was formed between two oil phases of nonane at electrolyte concentration higher than Cei,cr-... 

Understanding of surfactant sorption onto soil is needed to assess surbctant mobility in soil and surfactant-fecilitated transport of hydrophobic pollutants in soil/aqueous systems. Micelle-like amphiphilic nano-sized polyurethane (APU) particles synthaized from amphiphilic urethane acrylate anionomers could solubilize a model hydrophobic pollutant, phenanthrene wiliiin their hydrophobic interiors. Batch experiments were conducted with soil slurries to compare APU Sodium Dodecyl Sulfrde (SDS), anionic surfrictant for the sorption onto soil. APU particles (KniH).2 mUg) were weakly adsorbed onto the sandy soil compared to SDS (Ksui =l.3 mL/g), due to their chemically ciosslinked structure. Compared with SDS, APU particles exhibited the higher extraction efficiency to remove phenanthrene from the contaminated sandy soil. 

Soo and Radke (11) also studied the effect of average droplet size of emulsion on the flow behavior in porous media. The droplet size distribution of the emulsions that were prepared with surfactants and NaOH in a blender are shown in Figure 12. These droplet size distributions were found to be log-normal distributions. Others (9, 27) have also observed that the size of emulsion droplets was log-normally distributed. Soo and Radke (11) conducted experiments with emulsions having different average mean diameter in fine Ottawa water-wet sand packs. Their results of the reduced permeability, k/ko, and reduced effluent volume concentration as a function of the pore volume of oil (in the emulsion) injected are shown in Figure 13. All emulsions were of 0.5% quality, and the initial permeability, ko, was 1170 mD (millidarcies). The lines in the figure represent results of flow theory (12,13) based on deep-bed filtration principles. 

The surface tension and the conductivity of solutions with surfactants is not affected by the addition of povidone [492,616]. 

Although alkaline flooding only is not conducted as often as polymer flooding or surfactant flooding, alkaline injection is conducted together with surfactant and polymer injection. Simulation of alkaline flooding is very difficult because of complex chemical reactions. These complex reactions include at least the following ... 

Shinoda and coworkers [20] found that many O/W emulsions (based on ethoxylated surfactants) undergo a process of inversion to W/O at a critical temperature (PIT). The PIT can be easily measured by following the conductivity of the emulsion as a function of temperature (a small amount of electrolyte, e.g., NaCl is added to increase the sensitivity of measurement). The conductivity of the O/W emulsion increases with increase of temperature until the PIT is reached, above which there is a rapid reduction in conductivity (a W/O emulsion is formed with low conductivity as the continuous phase is now oil). Figure 15.12 shows a schematic representation of the variation of conductivity with temperature increase for an O/W emulsion. At the PIT, the interfadal tension y reaches a minimum, as illustrated in Figure 15.13 for an O/W emulsion. 

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