Hydrocarbons, solubilization

It is of particular interest to be able to correlate solubility and partitioning with the molecular stmcture of the surfactant and solute. Likes dissolve like is a well-wom plirase that appears applicable, as we see in microemulsion fonnation where reverse micelles solubilize water and nonnal micelles solubilize hydrocarbons. Surfactant interactions, geometrical factors and solute loading produce limitations, however. There appear to be no universal models for solubilization that are readily available and that rest on molecular stmcture. Correlations of homologous solutes in various micellar solutions have been reviewed by Nagarajan [52]. Some examples of solubilization, such as for polycyclic aromatics in dodecyl sulphonate micelles, are driven by hydrophobic... 

Solubilizing activity are also used in enhanced oil recovery. Tar and extremely viscous hydrocarbons are recovered by the injection of an aqueous solution of an anionic orthophosphate ester surfactant into a petroleum formation, retaining the surfactant in the formation for about 24 h, and displacing the solubilized hydrocarbons toward a recovery well. The surfactant forms an oil microemulsion with the hydrocarbons in the formation. An anionic monoorthophosphate ester surfactant which is a free acid of an organic phosphate ester was dissolved in water. The input of surfactant solution was 2-25% of the pore volume of the formation [250]. To produce a concentrate for the manufacture... 

An interesting class of polyeleclrolytes, denoted by polysoaps, is obtained by attaching soap-like molecules to the polymer chain. Such a polysoap is for instance produced by the quaternization of polyvinyl-pyridine with /r-dodecyl bromide. The polysoap molecules differ from ordinary poly electrolytes in that they may reach protein-like compactness in solution. They behave like prefabricated soap micelles and solubilize hydrocarbons and other compounds insoluble in water,... 

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. 

Fig. 1. Backbone structures of some of the conjugated polymers investigated as bulk solids and in dilute solution using the PR-TRMC technique. The position of the solubilizing hydrocarbon substituents is indicated by R.

Structural Considerations of Lamellar Liquid Crystals Containing Large Quantities of Solubilized Hydrocarbon Alkanes... 

The stability of a lamellar liquid crystal with such a large amount of oil is an intriguing problem. The main structural entity to be clarified before a serious attempt at an examination of the problem may be made is the degree of order of the hydrocarbon chains. This factor in turn depends on the location of the solubilized hydrocarbon chains are they penetrating the amphiphilic layer or are they forming a liquid layer between the layers of amphiphilic molecules. 

Low angle X-ray data alone cannot provide an unambiguous answer to the question of location and order of the hydrocarbon chains. We considered direct determinations of the order parameters of the solubilized hydrocarbon chains to be useful information. A preliminary NMR investigation (3) of alkane solubilized in the lamellar phases formed by and water provided tentative support for the... 

The splittings pass through a maximum with the oil content varying from approximately 20% solubilized hydrocarbon for the three outer carbons in the chain to less than 10% for the second carbon atom counted from the center of the chain. 

Effect of Monomeric Organic Additives The presence of solubilized hydrocarbon in the surfactant micelles generally increases the solubility of polar compounds in these micelles. The solubilized hydrocarbon causes the micelle to swell, and this may make it possible for the micelle to incorporate more polar material in the palisade layer. On the other hand, the solubilization of such... 

The CMC is also well defined experimentally by a number of other physical properties besides the variation of the surface tension. The variation of solution properties such as osmotic pressure, electrical conductance, molar conductivity, refractive index, intensity of scattered light, turbidity and the capacity to solubilize hydrocarbons with the increase of surfactant concentration will change sharply at the CMC as shown in Figure 5.8. The variation in these properties with the formation of micelles can be explained as follows. When surfactant molecules associate in solution to form micelles, the concentration of osmotic units loses its proportionality to the total solute concentration. The intensity of scattered light increases sharply at the CMC because the micelles scatter more light than the medium. The turbidity increases with micelle formation, because the solution is transparent at low surfactant concentrations, but it turns opaque after the CMC. Hydrophobic substances are poorly dissolved in aqueous solutions at concentrations below the CMC, but they start to be highly dissolved in the centers of the newly formed micelles, after the CMC. 

Solubilization plays an important role in emulsion polymerization of unsaturated hydrocarbons, leading to the production of latexes, which are aqueous dispersions of synthetic rubber. The polymerization process primarily occurs in micelles containing solubilized hydrocarbon, rather than in the hydrocarbon emulsion droplets. Emulsion polymerization usually yields spherical particles of uniform size [22],... 

At lower surfactant concentrations (line b) regions of phase separation appear. In such a phase-separated state there is a sequence of equilibria between phases, commonly referred to as Winsor equilibria [13,23]. In point A two macroscopic phases are formed. These are a microemulsion of composition B and an aqueous solution containing dissolved surfactant and micelles with solubilized hydrocarbon. The volumes of these macroscopic phases can be estimated in the usual way by applying the lever rule with a correction for the densities of these phases. In such a state of separation into two macroscopic phases, the equilibrium between the microemulsion and the aqueous solution is referred to as the Winsor II (WII) equilibrium. 

According to the studies carried out by V. N. Izmailova et al, the molecules of some proteins and enzymes reveal high capability to solubilize hydrocarbon molecules, which can incorporate into different segments of macromolecules. The solubilization studies, and in particular those of solubilization of hydrocarbons in aqueous solutions of proteins, allows one... 

As mentioned above, micelles have a limited capability to solubilize hydrocarbons within them thus, swollen micelles... 

Studies by Cheng et al. [73] showed that solubilization of the PAHs (phenanthrene and pyrene) increased linearly as the concentration of the biosurfactant produced by the R aeruginosa P-CG3 strain increased (Fig. 5) and from the strain ATCC 9027. The weight of phenanthrene and pyrene solubilized per gram of rhamnolipid was approximately 0.0025 and 0.0068, respectively, which is much less that shown earher for styrene (Fig. 3). The size of the micelles increases as the amount of solubilized hydrocarbon increases [71], Concentrations of the biosurfactant above the CMC in the aqueous phase increased desorption from the soil phase. 

Garrett et al. [108] and later Ashcroft et al. [109] have claimed that a rather novel application of the antifoam synergy found with hydrocarbon-calcium soap mixtures can be applied in this context. Consider then a cleaning liquid where both the hydrocarbon and a sodium soap (or fatty acid) are solubilized in a concentrated aqueous micellar solution of another surfactant. If use of the product involves dilution in hard water, then both the solubilized hydrocarbon and soap will be precipitated as the concentration of micelles decreases and the water hardness increases. It is claimed [108,109] that synergistic foam control is then observed as exemplified by the results shown in Table 8.2. Possibly precipitation of bulk phase hydrocarbon is nucleated on the calcium soap particles so that a hydrocarbon-calcium soap antifoam entity could be formed in situ giving rise to that synergy. 

Effect of Dilution with Hard Water on Foam Stability of Cleaning Liquid Containing Synergistic Mixture of Soap and Solubilized Hydrocarbon... 

The self-diffusion coefficient of the solubilized hydrocarbon was determined by Fourier transformation of the second half-echo [8]. In the micellar phase an interesting trend is observed (Fig. 20.2) the diffusion coefficient first increases with the hydrocarbon chain length up to m = 10, then a pronounced decrease for the larger dodecane and tetradecane solutes follows. 

Carcinogenic hydrocarbons which have entered the stomach with the ingested foods may be solubilized by the bile acids and fatty acids and brought into solution. Other substances present in the stomach which can solubilize hydrocarbons are the butyric and lactic acids produced by bacterial fermentation processes in vivo (see Table 10.23). The presence of these third components may... 

---