Surfactant amount

Analysis of NP-EO- o was made by UV-spectroscopy at 275 nm where the phenyl ring gives a strong absorption. The accuracy in the determination of the adsorption of NP-EO- o is about + 0.5 mg/g. The total surfactant concentration was determined by measuring the refractive index increment on a Jena differential refractometer. These measurements give the total surfactant adsorption with an accuracy of about 1 3 tagig. The SDS concentration was obtained from the difference (total surfactant - amount of NP-EO- o) and hence is definitely not known to an accuracy better than 3 mg/g. 

Figure 4 shows phenanthrene and naphthalene sorption isotherms to kaolinite covered with varying levels of sorbed surfactant these levels of surfactant coverage correspond to the different regions existing in the surfactant sorption isotherms discussed earlier (Fig. 1). The linearity of each isotherm was evaluated using Freundlich and linear sorption models. It is apparent from Fig. 4 and Table 4 that HOC partitioning to kaolinite with and without adsorbed surfactants results in linear or near-linear isotherms. As the amount of surfactant adsorbed on the kaolinite surface increased, the sorption of phenanthrene and naphthalene to the solid phase also increased. However, upon normalizing by the amount of sorbed surfactant present, the sorbed surfactant partition coefficient (Kss) decreased with increasing sorbed surfactant amounts (Table 4).

The amount of surfactant or inherent surface stabilizing groups required to form a polymerizable miniemulsion is comparably small, e.g., with SDS between 0.25 and 25% relative to the monomer phase, which is well below the surfactant amounts required for microemulsions. 

The high homogeneity and rather well-defined character of those latexes is clearly observed. Again, already surfactant loads as low as 1.8% relative to the dispersed phase result in stable latexes. The particle size is getting smaller with increasing amounts of the surfactant, and the surface area per surfactant molecule Asurf is between 18 nm2 at low surfactant amounts (1.8 rel.%) and 7 nm2 for higher surfactant amounts (7.1 rel.%), depending on the particle size. 

In which W Is weight percentage water of total and S the corresponding measure of surfactant amount. 

The selection of the organic phase has a substantial effect on the minimum surfactant concentration necessary to obtain the inverse microemulsion. Nevertheless, there is a threshold for the minimum surfactant amount needed to form the small microemulsion droplets (d a 5-10 nm). Calculations give a limiting value of approximately 10% of all other components lower concentrations of surfactant lead to conventional macroemulsions. 

Initiator (and amount) mol/dm X 10 Surfactant Amount mol/dm X10 Pzn Temp. °C Partide size nm Tg after dialysis water water + °C Ethanol °C ... 

The surfactant concentration has a great effect on the decrease in the dispersity degree of the emulsions. An abrupt decrease in the droplet size becomes appreciable with addition of even small surfactant amounts—0.25% of ethoxylated alkylphenol. This dispersity increase unequivocally leads to an increase in sedimentation stability. 

In 2000, the total worldwide market for surfactants amounted to approximately 19 million tons [29] with an estimated global growth rate of 3-4% per year and about 2% in the European Union. 

Figure 22.1. Percentage of surfactant amounts in different fields of application in Western Europe...

Maximum surfactant amount adsorbed at gas-liquid interface, kg/m ... 

On the other hand, the coordinates of the fishtail are shghtly affected by a change of [bmim][PF j fraction. The variation of f and T with a allows the determination of the trajectory of the middle phase. Its schematic projection onto the (7, 7) plane is voluntarily amplified and displayed in Figure 11.4. We notice, from this trajectory (dotted line), that the surfactant amount needed to produce one-phase microemulsion is highest when a = 0.58, which corresponds to equal water and [bmim][PFJ volumes. An increase or a decrease in a from 0.58 systematically, although only to a little extent, decreases the optimal amount of surfactant f. The small variation in 7 and r is a significant difference between this system and water-u-dodecane systems [40-42]. A careful examination of absolute 7 values brings the present water-[bmim] [PFJ-TX-100 closer to water-u-dodecane-C Ej. Indeed, we observe that both are inefficient nearly 50% of surfactant is needed to solubilize water with the immiscible solvent. 

This is not the end of the story, however. A third type of effect can alter the selfassociation structure and is directly related to the surfactant and or alcohol inherent properties. For instance, straight-chain ionic surfactants would produce liquid crystals of the lamellar type unless the temperature is quite elevated. Thus, in most cases of ionic systems, a large amount of alcohol (as much as two or three times the surfactant amount on a mole fraction basis) is required to melt the liquid crystal into a microemulsion, particularly for middle-phase ones [33]. Note, however, that too much alcohol could be detrimental to a high-performance microemulsion because the alcohol molecules which are not playing a cosurfactant role at the interface would dissolve into the bulk of one or both excess phases, making them more compatible [i.e., the alcohol would make the water less polar and the oil more polar (depending on the alcohol, but most particularly, intermediate solubility ones such as secondary butanol or tertiary pentanol)]. This is, of course, a way to narrow the miscibility gap, but this time by favoring the formation of a cosolubilized random mixture of all molecules instead of a microemulsion structure [50,65]. 

The ratio of specific surfactant amount to magnetite particles Xs/m and the mass fraction of surfactant in the solvent xs are defined by Eqs. (3) and (4). 

The formulation dominates the properties of SOW systems when the surfactant concentration is not too low and when the water-to-oil ratio is close to unity. When this is not satisfied, then the composition, i.e., the relative proportions of different substances, has to be taken into account. Provided that the surfactant concentration is not high enough to produce a singlephase microemulsion, say less than 10 to 20%, the most critical composition variable is the water-to-oil ratio, which is often expressed as the oil or water fraction, because the surfactant amount is small. 

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