Water solubility, surfactants

Natural Ethoxylated Fats, Oils, and Waxes. Castor oil (qv) is a triglyceride high in ticinoleic esters. Ethoxylation in the presence of an alkaline catalyst to a polyoxyethylene content of 60—70 wt % yields water-soluble surfactants (Table 20). Because alkaline catalysts also effect transestenfication, ethoxylated castor oil surfactants are complex mixtures with components resulting from transesterrfication and subsequent ethoxylation at the available hydroxyl groups. The ethoxylates are pale amber Hquids of specific gravity just above 1.0 at room temperature. They are hydrophilic emulsifiers, dispersants, lubricants, and solubilizers used as textile additives and finishing agents, as well as in paper (qv) and leather (qv) manufacture. 

Gas turbine fuels can contain natural surfactants if the cmde fraction is high in organic acids, eg, naphthenic (cycloparaffinic) acids of 200—400 mol wt. These acids readily form salts that are water-soluble and surface-active. Older treating processes for sulfur removal can leave sulfonate residues which are even more powerful surfactants. Refineries have installed processes for surfactant removal. Clay beds to adsorb these trace materials are widely used, and salt towers to reduce water levels also remove water-soluble surfactants. In the field, clay filters designed as cartridges mounted in vertical vessels are also used extensively to remove surfactants picked up in fuel pipelines, in contaminated tankers, or in barges. 

Surfactants and Dispersants. Castor od can be transformed from an od- to a water-soluble surfactant, depending on the moles of ethylene oxide added to its hydroxyl group. A 40 mole ethylene oxide adduct of castor od, known as PEG-40 castor od, is a surfactant that has cosolvent properties and is utilized as a fragrance solubilizer (118). Glycol hydroxystearate emulsifiers are formulated into shampoos to impart finer peadescence and give better stabdity than gylcol stearates (118) (see Hair preparation). 

Asphalts and waxes can be removed by dissolving in hot naphtha for 3 to 4 hours. The naphtha benefits from the addition of 0.1% of a water-soluble surfactant (HLB value of 15-20, such as polyethylene glycol 600 monolaurate) and 0.1% of an oil-soluble surfactant (HLB value of 0-5, such as propylene glycol monstearate). The solution must be circulated fill-and-soak methods are unsatisfactory. 

Quaternary alkylammonium salts are generally water-soluble surfactants. The sol-gel-derived anion-sensing membranes encapsulating a quaternary alkylammonium salt, especially with high contents, are easy to deteriorate due to the exudation of the cationic site from the membrane to aqueous sample phases. Moreover, another issue concerning the dispersibility of ammonium salts in sol-gel-derived membranes may happen when high... 

Larpent, C., Brisse-le-Menn, F., and Patin, H., New highly water-soluble surfactants stabilize colloidal rhodium(O) suspensions useful in biphasic catalysis, J. Mol. Catal., 65, L35-L40, 1991. 

Depending upon the physical properties of a surfactant (component), removal from the mixed liquor is further possible through precipitation of insoluble salts and adsorption onto solids or bacterial floes, which, in turn, are subsequently withdrawn with the excess sludge [53]. In particular, intact or partly degraded low water-soluble surfactants are eliminated by this route. 

Thus, especially since the development of appropriately specific and sensitive analytical methods, as discussed in Chapter 2, it seems only logical that some highly water-soluble surfactants and their even more polar metabolites have been positively detected in potable water. In the following sections, examples are given according to the different surfactant classes as well as the source of the raw water used. 

This transition may j-.e. reducing the specific surface energy, f. The reduction of f to sufficiently small values was accounted for by Ruckenstein (15) in terms of the so called dilution effect". Accumulation of surfactant and cosurfactant at the interface not only causes significant reduction in the interfacial tension, but also results in reduction of the chemical potential of surfactant and cosurfactant in bulk solution. The latter reduction may exceed the positive free energy caused by the total interfacial tension and hence the overall Ag of the system may become negative. Further analysis by Ruckenstein and Krishnan (16) have showed that micelle formation encountered with water soluble surfactants reduces the dilution effect as a result of the association of the the surfactants molecules. However, if a cosurfactant is added, it can reduce the interfacial tension by further adsorption and introduces a dilution effect. The treatment of Ruckenstein and Krishnan (16) also highlighted the role of interfacial tension in the formation of microemulsions. When the contribution of surfactant and cosurfactant adsorption is taken into account, the entropy of the drops becomes negligible and the interfacial tension does not need to attain ultralow values before stable microemulsions form. 

The previous experimental observations reported in the preceding text are, at least to a certain extent, in agreement with the well-known Bancroft rule. Indeed, a double W/O/W emulsion turns into a simple direct one when a sufficient quantity of the water-soluble surfactant is added. Similarly, by shaking a 1 1 mixture of water and oil, each phase containing one of the two types of surfactants, a direct emulsion is obtained if the aqueous phase contains a large amount of water-soluble... 

Dickinson, E., Tanai, S. (1992). Protein displacement from the emulsion droplet surface by oil-soluble and water-soluble surfactants. Journal of Agricultural and Food Chemistry, 40, 179-183. 

Dickinson, E., Owusu, R.K., Williams, A. (1993b). Orthokinetic destabilization of a protein-stabilized emulsion by a water soluble surfactant. Journal of the Chemical Society, Faraday Transactions, 89, 865-866. 

Microemulsions are transparent or translucent, thermodynamically stable emulsion systems (Griffin 1949). Forming a middle phase microemulsion (MPM) requires matching the surfactant system s hydrophobicity with that of the oil. The HLB (hydrophilic-lipophilic balance) number reflects the surfactant s partitioning between water and oil phases higher HLB values indicate water soluble surfactants while lower values indicate oil soluble surfactants (Kunieda et. al. 1980, Abe et. al. 1986). While a balanced surfactant system produces middle phase microemulsions, an underoptimum surfactant system is too water soluble (high HLB) while an over-optimunTSystem is too oil soluble (low HLB). 

In the batch process low-water-solubility monomers are emulsified in water by water-soluble surfactants, purged and heated at the initiation temperature (for energy saving this is usually lower than the reaction temperature to benefit from the reaction exotherm) and the initiator added. Temperature is then maintained for the reaction period, which can range from 1 to 24 h. Reactions are driven to the maximum conversion compatible with the system and the residual monomer and other volatile compounds are removed either by stripping or by chemical treatment. 

Is a water-soluble surfactant used as a base lubricant for synthetic fiber spin finishes, open end spinning, and overspray finishes. It is also an excellent co-emulsifier and coupling agent for many formulations. 

Is a water-soluble surfactant. It is useful as a foam builder and solubilizer for alkyl aryl sulfonates, essential oils, aromatic solvents, fats, and waxes. TRYCOL 5949 is also used as a co-emulsifier. 

Is a water-soluble surfactant used in light and heavy duty cleaning formulations. 

An oil-soluble surfactant and co-emulsifier, is used in combination with water-soluble surfactants as a defoaming agent. 

Is a water-soluble surfactant widely used for general purpose detergency, wetting, and emulsification. 

Is a moderately high-foaming, water soluble surfactant used as a wetting agent and emulsifier. 

An empirical scale developed for categorizing single-component or mixed (usually nonionic) emulsifying agents, using this principle, is the hydrophile-lipophile balance or HLB scale. This dimensionless scale ranges from 0 to 20 a low HLB (<9) refers to a lipophilic surfactant (oil-soluble) and a high HLB (>11) to a hydrophilic (water-soluble) surfactant. In gen-... 

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