Surfactant rich phase

LIOPHILIC PROPERTIES OF THE SURFACTANT-RICH PHASES OF POLYETHOXYLATED ALKYLPHENOLS OP-7 AND OP-10... 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

Possibility of changing the properties of micellar phases by electrolyte inclusions was shown. Under this condition, in the systems with manifestation of complexes formation between the cationic compound of the electrolyte and the polyoxyethylene chain of the surfactant, increase of the hydrophilic properties of micellar phases was observed. The electrolytes that do not have affinity to the surfactant s molecule practically do not influence the liophily of the nonionic surfactant-rich phases. 

For fluorescence PAH determination in tap water acid-induced cloud point extraction was used. This kind of extraction based on the phase separation into two isotropic liquid phases a concentrated phase containing most of the surfactant (surfactant-rich phase), where the solubilised solutes are exttacted, and an aqueous phase containing a surfactant concenttation closes to the critical micellar concentration. 

The study of the mechanism of cloud point micellar extractions by phases of non-ionic surfactant (NS) is an aspect often disregarded in most literature reports and, thus, is of general interest. The effective application of the micellar extraction in the analysis is connected with the principled and the least studied problem about the influence of hydrophobicity, stmcture and substrate charge on the distribution between the water and non-ionic surfactant-rich phase. 

Strkcttire inflkence. The specificity of interphase transfer in the micellar-extraction systems is the independent and cooperative influence of the substrate molecular structure - the first-order molecular connectivity indexes) and hydrophobicity (log P - the distribution coefficient value in the water-octanole system) on its distribution between the water and the surfactant-rich phases. The possibility of substrates distribution and their D-values prediction in the cloud point extraction systems using regressions, which consider the log P and values was shown. Here the specificity of the micellar extraction is determined by the appearance of the host-guest phenomenon at molecular level and the high level of stmctural organization of the micellar phase itself. 

THE CLOUD-POINT EXTRACTION OF ALIPHATIC AMINES INTO THE NON-IONIC SURFACTANT-RICH PHASES... 

In n-octane/aqueous systems at 27°C, TRS 10-80 has been shown to form a surfactant-rich third phase, or a thin film of liquid crystals (see Figure 1), with a sharp interfacial tension minimum of about 5x10 mN/m at 15 g/L NaCI concentration f131. Similarly, in this study the bitumen/aqueous tension behavior of TRS 10-80 and Sun Tech IV appeared not to be related to monolayer coverage at the interface (as in the case of Enordet C16 18) but rather was indicative of a surfactant-rich third phase between oil and water. The higher values for minimum interfacial tension observed for a heavy oil compared to a pure n-alkane were probably due to natural surfactants in the crude oil which somewhat hindered the formation of the surfactant-rich phase. This hypothesis needs to be tested, but the effect is not unlike that of the addition of SDS (which does not form liquid crystals) in partially solubilizing the third phase formed by TRS 10-80 or Aerosol OT at the alkane/brine interface Til.121. 

The interfacial tension-temperature relationships at various CaCL concentrations for Karamay crude in a Sun Tech IV (5 g/L) and NaCI (10 g/L) solution are shown in Figure 9. For 0, 0.025 and 0.1 g/L Ca, an increase in interfacial tension with temperature was observed. The interfacial tension values above 150°C were about the same for these concentrations. At temperatures below 100°C, the effect of Ca was to increase interfacial tension, probably by hindering the formation of a surfactant-rich phase. This is consistent with the detrimental effect or light oil/brine interfacial tensions (increase from about 10 3 to about 10 1) reported by Kumar et al. T371. ... 

On the other hand, micelle formation has sometimes been considered to be a phase separation of the surfactant-rich phase from the dilute aqueous solution of surfactant. The micellar phase and the monomer in solution are regarded to be in phase equilibrium and cmc can be considered to be the solubility of the surfactant. When the activity coefficient of the monomer is assumed to be unity, the free energy of micelle formation, Ag, is calculated by an equation... 

This phenomenon can be exploited for separation and concentration of solutes. If one solute has certain affinity for the micellar entity in solution then, by altering the conditions of the solution to ensure separation of the micellar solution into two phases, it is possible to separate and concentrate the solute in the surfactant-rich phase. This technique is known as cloud point extraction (CPE) or micelle-mediated extraction (ME). The ratio of the concentrations of the solute in the surfactant-rich phase to that in the dilute phase can exceed 500 with phase volume ratios exceeding 20, which indicates the high efficiency of this technique. Moreover, the surfactant-rich phase is compatible with the micellar and aqueous-organic mobile phases in liquid chromatography and thus facilitates the determination of chemical species by different analytical methods [104]. 

Treatment of the aely " -(surfactant-rich phase l V dilution, cleanup Jj... 

Cloud point extraction from biological and clinical samples. The most frequent use of CPE is for the separation and purification of biological analytes, principally proteins. In this way, the cloud point technique has been used as an effective tool to isolate and purify proteins when combined with chromatographic separations. Most of the applications deal with the separation of hydrophobic from hydrophilic proteins, with the hydrophobic proteins having more affinity for the surfactant-rich phase, and the hydrophilic proteins remaining in the dilute aqueous phase. The separation of biomaterials and clinical analytes by CPE has been described [105,106,113]. 

In this extraction, the concentrated surfactant-rich phase was a solid rather than a liquid. Abbreviations for surfactants Igepal CO-630 nonylphenoxypoly(ethylenoxy)ethanol PONPE-7.5 polyoxyethylene(7.5)nonylphenyl ether PONPE-10 polyoxyethylene(10)nonylphenyl ether TRITON X t-octylphenoxypolyoxyethylene ether. 

Winsor [15] classified the phase equilibria of microemulsions into four types, now called Winsor I-IV microemulsions, illustrated in Fig. 15.5. Types I and II are two-phase systems where a surfactant rich phase, the microemulsion, is in equilibrium with an excess organic or aqueous phase, respectively. Type III is a three-phase system in which a W/O or an O/W microemulsion is in equilibrium with an excess of both the aqueous and the organic phase. Finally, type IV is a single isotropic phase. In many cases, the properties of the system components require the presence of a surfactant and a cosurfactant in the organic phase in order to achieve the formation of reverse micelles one example is the mixture of sodium dodecylsulfate and pentanol. 

Analogous to the MBG-method, Boy and Voss introduced the enzyme catalysis in liquid crystalline surfactant phases [114,115]. The enzymes, e.g. alcohold-ehydrogenase, were entrapped in a liquid crystalline surfactant rich phase, and this phase was rinsed with an organic phase containing the substrate. In this way, they can perform the reaction continuously using a packed reactor module without apparent loss of activity. 

The importance of a surfactant - rich phase, particularly a lamellar one, to detergency performance was noted for liquid soils such as C16 and mineral oil (3.6). Videomicroscopy experiments indicated that middle phase microemulsion formation for C12E04 and Cjg was enhanced at 30 °C, while at 18 °C, oil - in - water, and at 40 °C, water - in - oil microemulsions were found to form at the oil - bath interface (3.6). A strong temperature dependence of liquid soil removal by lamellar liquid crystals, attributed to viscosity effects, has been noted for surfactant - soil systems where a middle - phase microemulsion was not formed (10). 

The nature of the nonionic surfactant is still an important parameter in the removal of solid C19. C12E03 and the commercial surfactant Neodol 23-6.5 both form micellar solutions (Lj phase only) at 25 °C. Detergency performance of these surfactants is poor. The presence of C12E04 as a two phase system containing a surfactant - rich phase (Lj or La) is still clearly beneficial to the kinetics of solid C19 removal. 

The importance of the presence of a surfactant - rich phase in the washing bath has been mentioned several times. The perfoimance of C12EO in removal of C g is very poor at 30 °C, (Figure 23) just below the transition of the surfactant from a... 

Non-ionic surfactants do not exhibit Krafft points. Rather the solubility of nonionic surfactants decreases with increasing temperature and the surfactants begin to lose their surface active properties above a transition temperature referred to as the cloud point. This occurs because above the cloud point a separate surfactant-rich phase of swollen micelles separates the transition is visible as a marked increase in dispersion turbidity. As a result, the foaming ability of, for example, polyoxyethyle-nated non-ionics, decreases sharply above their cloud points. The addition of electro-... 

Type III microemulsions, in which the aqueous and oleic phases are in equilibrium with a third, surfactant-rich, phase called the middle-phase microemulsion, which can contain bi-continuous emulsion. This is illustrated in Figure 3.28 [226],... 

Aqueous Solutions The transition temperature above which a non-ionic surfactant or wax loses some of its water solubility and becomes ineffective as a surfactant. The originally transparent surfactant solution becomes cloudy because of the separation of a surfactant-rich phase. Cloud points are typically reported on the basis of tests for a specified surfactant concentration such as 1 mass%. See also Coacervation. 

In aqueous solutions the micellar assembly structure allows sparingly soluble or water-insoluble chemical species to be solubilized, because they can associate and bind to the micelles. The interaction between surfactant and analyte can be electrostatic, hydrophobic, or a combination of both [76]. The solubilization site varies with the nature of the solubilized species and surfactant [77]. Micelles of nonionic surfactants demonstrate the greatest ability for solubilization of a wide group of various compounds for example, it is possible to solubilize hydrocarbons or metal complexes in aqueous solutions or polar compounds in nonpolar organic solutions. As the temperature of an aqueous nonionic surfactant solution is increased, the solution turns cloudy and phase separation occurs to give a surfactant-rich phase (SRP) of small volume containing the analyte trapped in micelle structures and a bulk diluted aqueous phase. The temperature at which phase separation occurs is known as the cloud point. Both CMC and cloud point depend on the structure of the surfactant and the presence of additives. Table 6.10 gives the values of CMC and cloud point for the surfactants most frequently applied in the CPE process. 

In many of these studies the structure of the middle phase is not established, but it is clearly immiscible in water or oil and its electrical conductivity is closer to water than oil. Phase diagram studies of oil-water-emulsifier systems Ekwall, (5), indicate that surfactant-rich phases immiscible in oil or wa"ter have rodshaped or lamellar micelles with some degree of optical anisotropy or flow birefringence, and these phases have much greater elec-rical conductivity than oil. Figure 1 illustrates that the middle phase composition varies smoothly from a water-rich composition to an oil-rich composition as the emulsifier partition changes from mostly water-soluble to mostly oil-soluble. If lamellar structures are present the relative thickness of oleophilic and hydrophilic layers must vary smoothly from the water-rich compositions to the oil-rich compositions. 

The lET between the polymer-rich phase and surfactant-rich phase in an oil-free case could be very low, sometimes as low as 10 to 10 mN/m (Szabo, 1979). These low values of IFT indicate that the trapping of sulfonate, as discussed by Trushenski (1977), relates more to the difference in mobilities of the separated phases than to capillary force (IFT). 

The viscosity of the oil-free surfactant-rich phases (above the CEC, which is defined in the next section) is high it is frequently higher than the polymer-rich phase, even though they apparently contain almost no polymer (Szabo, 1979 Pope et al., 1982). The surfactant-rich phase appears to expel polymer to the polymer-rich phase, and the sulfonate forms a complex with the polymer molecules within its phase (Szabo, 1979). 

U.S. 5441661 08/1995 Beaujean et al.l Henkel KgaA surfactant-rich phase can be incorporated into the liquid phase without segregation or separation Nonaqueous liquid detergent containing a hydrated zeolite stabilized by a polar deactivating agent... 

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