Surfactants soluble

A quantitative treatment of surfactant solubility has been successfully made empirically using linear free energy relationships. An important relation is that for the linear free energy of transfer of alkanes to water [23] ... 

An a priori method for choosing a surfactant was attempted by several researchers (50) using the hydroph i1 e—1 ip oph i1 e balance or HLB system (51). In the HLB system a surfactant soluble in oil has a value of 1 and a surfactant soluble in water has a value of 20. Optimum HLB values have been reported for latices made from styrene, vinyl acetate, methyl methacrylate, ethyl acrylate, acrylonitrile, and their copolymers and range from 11 to 18. The HLB system has been criticized as being imprecise (52). 

Blends of sodium hypochlorite with 15% HC1 and with 12% HCl/3% HF have been used to stimulate aqueous fluid injection wells(143). Waterflood injection wells have also been stimulated by injecting linear alcohol propoxyethoxysulfate salts in the absence of any acid (144). The oil near the well bore is mobilized thus increasing the relative permeability of the rock to water (145). Temperature effects on interfacial tension and on surfactant solubility can be a critical factor in surfactant selection for this application (146). 

Surfactants are selected based primarily on the degree of solubilization. Other factors to be considered include toxicity, biodegradability, surfactant sorption, and surfactant solubility and compatibility with the separation process. Surfactants have the ability to lower the interfacial tension between water and the contaminant by as little as a factor of three to four orders of magnitude. Combined with a sufficient reduction in capillary forces, this allows pumped groundwater theoretically to move the DNAPL toward the recovery or extraction well. This is accomplished by injecting surfactant solution into the contaminated zone. Impacted groundwater characterized by an increase in the concentration of the contaminant is then recovered and treated. 

Krafft point (for ionic surfactants) and cloud point (for nonionic surfactants) are both a limit to surfactant solubility. The solubility of ionic surfactants decreases significantly below the Krafft point, since its concentration falls below the CMC and individual surfactant molecules cannot form micelles. Therefore, the Krafft point of an ionic surfactant must be below the desired wash temperature for maximum soil removal. In contrast, the solubility of some nonionic surfactants decreases with increasing temperature. Above the cloud point, the surfactant becomes insoluble. Thus, the cloud point of a nonionic surfactant should be 15-30°C above the intended wash temperature [8],... 

Hydrotropes (LD, DW, HC) Maintain product homogeneity Ability to increase surfactant solubility Color and odor Cumene sulfonate Ethyl alcohol Toluene sulfonates 0-10% 0-10%... 

Surfactants Soluble compounds which possess groups of opposite polarity and solubilizing tendencies. They can form oriented monolayers at phase interfaces, form micelles, and possess detergency, foaming, wetting, emulsifying, and dispersing properties. 

Experiments on the stability of the HIPEs indicated that one of the most important factors was the solubility of the emulsifier in the continuous (formamide) phase. Thus, the higher the surfactant solubility, the more stable the emulsion. The emulsifier concentration was also important stability increased to a maximum, then decreased, with increasing surfactant concentration. Surprisingly, the HLB number did not appear to have much effect on the stability of the emulsions, over the range studied (11 to 14). This was attributed to the high concentration of emulsifier in the continuous phase, although the narrow HLB value range is probably also a factor. 

Of the cations (counterions) associated with polar groups, sodium and potassium impart water solubility, whereas calcium, barium, and magnesium promote oil solubility. Ammonium and substituted ammonium ions provide both water and oil solubility. Triethanolammonium is a commercially important example. Salts (anionic surfactants) of these ions are often used in emulsification. Higher ionic strength of the medium depresses surfactant solubility. To compensate for the loss of solubility, shorter hydrophobes are used for application in high ionic-strength media. The U.S. shipment of anionic surfactants in 1993 amounted to 49% of total surfactant production. 

Similarly to the solubility of active drugs, the solubility of surfactants that were used in CFC systems has significantly changed. Surfactant solubility in HFA 134a ranges from 0.005% to 0.02% w/v, much lower than the concentration required to stabilize suspensions (0.1-2.0% w/v) (24,42). The surfactants can be solubilized with the addition of cosolvents such as ethanol. However, it is most likely that cosolvents will be incompatible with suspension formulations because drug solubility will also be promoted and crystal growth will occur. 

For ionic surfactants micellization is surprisingly little affected by temperature considering that it is an aggregation process later we see that salt has a much stronger influence. Only if the solution is cooled below a certain temperature does the surfactant precipitate as hydrated crystals or a liquid crystalline phase (Fig. 12.4). This leads us to the Krafft temperature1 also called Krafft point [526]. The Krafft temperature is the point at which surfactant solubility equals the critical micelle concentration. Below the Krafft temperature the solubility is quite low and the solution appears to contain no micelles. Surfactants are usually significantly less effective in most applications below the Krafft temperature. Above the Krafft temperature, micelle formation becomes possible and the solubility increases rapidly. 

Matheson, K.L., M.F. Cox, and D.L. Smith. 1985. Interactions between linear akylbenzene sulfonates and water hardness ions. I. Effect of calcium ion of surfactant solubility and implications for detergency performance. JAOCS 62, 1391-1399. 

Fig. 2.8. Temperature dependence of surfactant solubility in the region of the Krafft point. (From Ref.2 )...

The wetting of a liquid drop placed on a solid surface has already been described (Section 3.4) by the critical surface tension of the surface and by Young s equation. Temperature is a factor in wetting by aqueous solutions since it influences surfactant solubility. For example, the fastest wetting for polyoxyethylenated non-ionic surfactants is produced by those whose cloud points are just above the use temperature [193]. 

Composition vs. properties. With such a wide pallet of raw materials, it is possible to produce a very wide range of attributes in the surfactant and the HLB may be varied from 8 (low C number, low EO), to give surfactants soluble in organic media, to >20 (very good aqueous solubility). Ether sulphates (laureth-2 or laureth-3) would have HLB values of 20. 

Certain antifoams, for example, methyl or ethyl alcohols, when introduced in the foaming solution, affect indirectly the foam stabilising properties of the adsorption layers because they change either the surfactant solubility or its CMC. It has been established [39] that addition of antifoams (2-ethylhexanoI and tributyl phosphate) increases CMC. Schick and Fowkes [40] have observed a certain change in CMC of NaDoS when tetradecanol is added. If the compounds added improve the foaming ability (such as dodecylglycol ether and (3-hydroxyethyl laurylamide), CMC decreases. 

As indicated in Figures 5 and 6, there is a nearly linear relationship between the log[AOT] solubility and the fluid density over several order of magnitude of AOT concentration. This type of behavior would be expected for the solubility of a non-aggregate forming, solid substance in a supercritical fluid (XL). The solubility and phase behavior of solid-supercritical fluid systems has been described by Schneider (2H) and others, and such behavior can be predicted from a simple Van der Waal s equation of state. Clearly, this approach is not appropriate for predicting surfactant solubilities in fluids, because it does not account for the formation of aggregates or their solubilization in a supercritical fluid phase. 

In Figures 5 and 6, one might expect to see two different solubility regions. At low fluid densities where intermolecular forces are reduced and the surfactant concentration is below the CMC, the solubility should increase gradually as the density increases. At higher densities, above the CMC, the solubility should increase rapidly because the total surfactant solubility is dominated by the saturation concentration of micelles in the fluid. This type of behavior is not apparent in Figures 5 and 6, perhaps because the CMC is below 10 M. 

A lower interfacial tension will lead to a more stable emulsion. Temperature affects physical properties of oil, water, interfacial films, and surfactant solubilities in the oil and water phases, which can all affect emulsion stability. Further, the rheology of the emulsion itself is affected significantly by temperature. 

Ridder KB, Davies-Cutting CJ, and Kellaway IW. Surfactant solubility and aggregate orientation in hydrofluoroalkanes. Int J Pharm 2005 295 57-65. 

In general, low-carbon alcohols can increase surfactant solubility, so SPI can be alleviated when an alcohol is added. However, the effect of alcohols on surfactant-polymer compatibility is complex. Not all alcohols can improve the... 

If the disjoining pressures, flj and Il2, are zero, the ratio in Equation 5.292 will be very small. Hence, emulsion 1 (surfactant soluble in the continuous phase) will coalesce much more slowly and it will survive. This underlines the crucial importance of the surfactant location (which is connected with its solubility), thus providing a theoretical foundation for Bancroft s rule. The emulsion behavior in this case will be controlled almost entirely by the hydrodynamic factors (kinetic stability). 

The Krafft point can be defined as the temperature T above which the amphiphile (surfactant) solubility in water greatly increases [3], The reason is that the water solubility of the amphiphile, which increases with temperature, reaches the amphiphile critical micelle concentration (Cm in Figure 3.6). When the solubility curve is above Cm the dissolved amphiphile forms micelles and the amphiphile... 

The decrease of surfactant solubility in solution may also modify the phase equilibria in the system [26],... 

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