Solubilization of water

Petroleum sulfonates are widely used as solubilizers, dispersants (qv), emulsifiers, and corrosion inhibitors (see Corrosion and corrosion inhibitors). More recentiy, they have emerged as the principal surfactant associated with expanding operations in enhanced oil recovery (66). Alkaline-earth salts of petroleum sulfonates are used in large volumes as additives in lubricating fluids for sludge dispersion, detergency, corrosion inhibition, and micellar solubilization of water. The chemistry and properties of petroleum sulfonates have been described (67,68). Principal U.S. manufacturers include Exxon and Shell, which produce natural petroleum sulfonates, and Pilot, which produces synthetics. 

When secondary or primary amines are used in place of ammonia the corresponding dialkylaminomethylenephosphonic acids (7) or alkyliminobismethyl-enephosphonic acids (8) are formed. These are used as lime soap dispersants and solubilizers of water in organic solvents [131-135]. 

The solubilization of water in lecithin-reversed micelles has been found to be an exothermic process. This finding confirms that water interacts with the zwitterionic head group of lecithin, promoting the formation of strong intermolecular H bonds [104]. 

Investigations of the solubilization of water and aqueous NaCl solutions in mixed reverse micellar systems formed with AOT and nonionic surfactants in hydrocarbons emphasized the presence of a maximum solubilization capacity of water, occurring at a certain concentration of NaCl, which is significantly influenced by the solvent used [132],... 

For the scale-up of reverse micelle extractions, it is important to know which factors determine the mass transfer rate to or from the reverse micelle phase. So far most work has concentrated on the kinetics of solubilization of water molecules [34,35], protons [36], metal ions [20,35,37,38 0], amino acids [41], and proteins [8,35,42,43]. There are two separate processes forward transfer, which is transfer of solute from the aqueous to the reverse micelle phase, and back transfer, which is the antithesis of the first one. 

The role of LCC s in living plant tissues is presumed to be related to the prevention of water-soluble hemicelluloses from dissolving out of the cell wall by the formation of micelles or aggregates that immobilize sugar chains, and the solubilization of water-insoluble material such as lignin, thereby enabling it to move to any place in the cell. 

Frank, S. G., Zograti, G., Solubilization of Water by Dialkyl Sodium... 

Solubilization of water. Detergency is defined as the ability of surfactant molecules to solubilize water molecules or polar substances in soft-core and hardcore RMs. Thus, micellization and solubilization are competitive processes. Any solubilized probe molecule causes a decrease in the CMC. Solubilization describes the dissolution of a solid, liquid or gas by an interaction with surfactant molecules. Addition of water has a dramatic effect on surfactant aggregation in hydrocarbons because hydrogen bonding has an appreciable stabilizing effect on reverse micelles. Solubilization for reverse micelles is phenomenologically similar to the adsorption processes (Eicke and Christen, 1978 Kitahara, 1980 Kitahara et al., 1976 Singleterry, 1955). 

Micellar solubilization of water by surfactants having different polar groups follows the order ... 

The water in the RMs is considered to be a composite of two different types the "bound water" region, and the remaining "free water" region. On the basis of the IR data up to a Wo = 4, the water solvates the AOT ion-pair, further increasing in the water concentration up to a Wo = 10, probably giving rise to a hydration shell around the new-separated ions of AOT. Further increasing water concentration gives rise to the so called "free water". It has been shown by various physico-chemical techniques that the water of the reverse micelle behaves differently from normal water, especially at low concentrations (Wo < 10). Solubilization of water by such micelles promotes dissociation of ion pairs in the micelle to form micellar free ions. 

The typical detergent-dispersant additives used in modem lubricating oils are metallic detergents/sulfonates, phenolates, phosphonates, salicylates, ashless dispersants/succinimides and benzylamines. Water is solubilized by strong ion-dipole interactions. The solubilization of water (Watanabe, 1970) by hydrogen bond formation with succinimides and the amount solubilized is smaller than that solubilized by sulfonates. 

The difference is ascribed to the smaller micelle cavity of succinimides relative to sulfonates. Mixed micelles of naphthalene-sulfonate-succinimide show weaker solubilization capacity than that of individual additives. The solubilization of water in a micellar system is closely related to the micelle core (Fontana, 1968). Addition of water to this non-polar solution, as engine lubricating oil is, produces a new set of phenomena. For small amounts of water, the micellar aggregates show swelling by uptake of water. The highly bounded water in reversed micelles makes surfactants less effective. 

The major benefit of the solubilization principle is the increased water solubility of water-insoluble drugs such as phenolic compounds, iodine, steroids, and vitamins. The solubilization of water-insoluble materials in micelles may have some effects on drug activity and absorption. In addition, drugs in the micelles may prefer to stay... 

Some fundamentals of micelle formation and of the solubilization of water-insoluble substances by micelles are reviewed. The accelerating effect of micellization upon the rate of dissolution and of transport of solubilizate through bulk liquid is then considered. Membranes present an obstacle to transport. A larger fraction of the total driving force can be brought to bear upon this obstacle as other resistances are reduced by solubilization. Hence, transport across a membrane will, in general, be accelerated whether micelles are effective within the membrane or not. It is now possible to determine also this contribution of micelles to the transport within the membrane. In a specific case it was found to be negligible. 

At an air-water interface, a monolayer forms with heads lying down and tails up (toward air), whereas at an air-hydrocarbon interface the monolayer lies with tails down. By closing on the tail side, the sheetlike structure can be dispersed in aqueous solutions as spherical, rodlike, or disklike micelles (Fig. 3). Closure on the head side forms the corresponding inverted micelles in oil. Oil added to a micellar solution is incorporated into the interior of the micelle to form a swollen micellar solution. Thus, surfactant acts to solubilize substantial amounts of oil into aqueous solution. Similarly, a swollen inverted micellar solution enables significant solubilization of water in oil. 

Wickramanayake P, Moffatt JR. (1993) Solubilization of water-insoluble dyes via microemulsions for bleedless, non-threading, high print quality inks for thermal inkjet printers, US5226957. 

The most important property of micelles in aqueous or nonaqueous solvents is their ability to dissolve substances that are insoluble in the pure solvent. In aqueous systems, nonpolar substances are solubilized in the interior of the micelles, whereas polar substances are solubilized in the micellar core in nonaqueous systems. This process is called solubilization. It can be defined as the formation of a thermodynamically stable isotropic solution with reduced activity of the solubilized material (8). It is useful to further differentiate between primary and secondary solubilization. The solubilization of water in tetrachloroethylene containing a surfactant is an example of primary solubilization. Secondary solubilization can be considered as an extension of primary solubilization because it refers to the solution of a substance in the primary solubilizate. 

The spectroscopic probe pyridine-N-oxide was used to characterize polar microdomains in reverse micelles in supercritical ethane from 50 to 300 bar. For both anionic and nonionic surfactants, the polarities of these microdomains were adjusted continuously over a wide range using modest pressure changes. The solubilization of water in the micelles increases significantly with the addition of the cosolvent octane or the co-surfactant octanol. Quantitative solubilities are reported for the first time for hydrophiles in reverse micelles in supercritical fluids. The amino acid tryptophan has been solubilized in ethane at the 0.1 wt.% level with the use of an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (AOT). The existence of polar microdomains in aggregates in supercritical fluids at relatively low pressures, along with the adjustability of these domains with pressure, presents new possibilities for separation and reaction processes involving hydrophilic substances. 

The influence of octane on solubilization of water and solvatochromic polarity is pronounced as shown in Table HI. Two combinations of octane concentration and Wq were investigated. In both cases, large amounts of water are solubilized at low pressures. The polarities do not change with an increase in pressure as they are already comparable with that of bulk water. At these high concentrations of octane, the fluid is much less compressible than ethane. In the future, we will explore lower concentrations of octane to determine if pressure could be used to tune the polarity in the one phase region. 

The addition of 0.01 M octanol increases significantly the solubilization of water from a Wo of 3 to 11. The polarity increases to approach the pure water value of 254 nm, but it was not adjustable with pressure in the one phase region. 

Based on these results, we explored the possibility of using octanol as an amphiphilic cosolvent without the need for AOT. With the addition of octanol at a concentration of 0.5 M, it becomes possible to solubilize water at 0.05 M at only 80 bar. The Xmax is close to that of pure octanol, so that it is unlikely that water pools were formed. The cosolvent octanol could play an important role in SCF technology by increasing the solubilization of water. 

With this information at hand, an examination of the energy changes for all the alternatives 1-3 were considered useful in order to understand the energy foundation for the solubilization of water into a soap/acid complex. 

Swatloski RP, Visser AE, Reichert WM, Broker GA, Farina LM, Holbrey ID, Rogers RD (2002) On the solubilization of water with ethanol in hydrophobic hexafluorophosphate ionic liquids. Green Chem 4 81-87... 

A general pattern of microemulsion phase behavior exists for systems containing comparable amounts of water and a pure hydrocarbon or hydrocarbon mixture together with a few percent surfactant. For somewhat hydrophilic conditions, the surfactant films tend to bend in such a way as to form a water-continuous phase, and an oil in water microemulsion coexists with excess oil. Drops in the microemulsion are spherical with diameters of order 10 nm. Both drop size and solubilization expressed as (VJVX the ratio of oil to surfactant volume in the microemulsion, increase as the system becomes less hydrophilic. At the same time interfacial tension between the microemulsion and oil phases decreases. Just the opposite occurs for somewhat lipophilic conditions. That is, a water in oil microemulsion coexists with excess water with drop size and solubilization of water (VJV,) increasing and interfacial tension decreasing as the system becomes less lipophilic. When the hydrophilic and lipophilic properties of the surfactant films are nearly balanced, a bicontinuous microemulsion phase coexists with both excess oil and excess water. For a balanced film (VJV,) and (VJV ) in the microemulsion are nearly equal, as are 7, 0 and... 

Change in the nature and molecular weight of the solvent affects the extent of solubilization of water. The amount solubilized by sodium di(2-ethylhexyl)sulfo-... 

These effects on the solubilization of water are in agreement with the prediction of Mitchell and Ninham that bringing the > 1 value of the ratio Vh /1c< o (Chapter 3, Section II) closer to 1 should increase the solubilization of water in inverted micelles. This is also consistent with increases in the solubilization of water observed upon the addition of benzene or nitrobenzene to solutions of sodium di(2-ethylhexyl)sulfosuccinate in isooctane (Maitra, 1983). The effects were explained as caused by desolvation of the surfactant by the additives, with consequent decrease in the value of Vh-... 

Predict the effect on the solubilization of water by micelles of R(OC2H4)xOH in heptane of ... 

Shinoda, K. andOgawa, T. (1967) Solubilization of water in nonaqueous solutions ofnon-ionic surfactants.. Colloid Interface Sci. 24, 56. 

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