Surfactants monooleate

A series of sorbitol-based nonionic surfactants are used ia foods as water-ia-oil emulsifiers and defoamers. They are produced by reaction of fatty acids with sorbitol. During reaction, cycHc dehydration as well as esterification (primary hydroxyl group) occurs so that the hydrophilic portion is not only sorbitol but also its mono- and dianhydride. The product known as sorbitan monostearate [1338-41 -6] for example, is a mixture of partial stearic and palmitic acid esters (sorbitan monopalmitate [26266-57-9]) of sorbitol, 1,5-anhydro-D-glucitol [154-58-8] 1,4-sorbitan [27299-12-3] and isosorbide [652-67-5]. Sorbitan esters, such as the foregoing and also sorbitan monolaurate [1338-39-2] and sorbitan monooleate [1338-43-8], can be further modified by reaction with ethylene oxide to produce ethoxylated sorbitan esters, also nonionic detergents FDA approved for food use. 

Some phosphorus-containing surfactants have bacteriostatic properties. In combination with their physiological acceptance they are used in cosmetics and pharmaceuticals. In mutanase oral anticarie compositions the combination of alkyl phosphates and nonionic surfactants stabilizes mutanase. A dentifrice useful for prevention of dental caries contains 0.5% sodium lauryl phosphate and 1.5% polyoxyethylene (20) sorbitan monooleate [222]. 

Figure 17-9. Surfactants in a slurry concentrate sorbitan monooleate, ethoxylated nonylphenol.

A multiwavelength approach might have been considered as an alternative to chemical derivatisation. Ruddle and Wilson [62] reported UV characterisation of PE extracts of three antioxidants (Topanol OC, Ionox 330 and Binox M), all with identical UV spectra and 7max = 277 nm, after reaction with nickel peroxide in alkaline ethanolic solutions, to induce marked differentiation in different solvents and allow positive identification. Nonionic surfactants of the type R0(CH2CH20) H were determined by UV spectrophotometry after derivatisation with tetrabromophenolphthalein ethyl ester potassium salt [34]. Magill and Becker [63] have described a rapid and sensitive spectrophotometric method to quantitate the peroxides present in the surfactants sorbitan monooleate and monostearate. The method, which relies on the peroxide conversion of iodide to iodine, works also for Polysorbate 60 and other surfactants and is more accurate than a titrimetric assay. 

Zhong et al. (2003) studied the apparent solubility of trichloroethylene in aqueous solutions, where the experimental variables were surfactant type and cosolvent concentration. The surfactants used in the experiment were sodium dihexyl sulfo-succinte (MA-80), sodium dodecyl sulfate (SDS), polyoxyethylene 20 (POE 20), sorbitan monooleate (Tween 80), and a mixture of Surfonic- PE2597 and Witconol-NPIOO. Isopropanol was used as the alcohol cosolvent. Eigure 8.20 shows the results of a batch experiment studying the effects of type and concentration of surfactant on solubilization of trichloroethylene in aqueous solutions. A correlation between surfactant chain length and solubilization rate may explain this behavior. However, the solubilization rate constants decrease with surfactant concentration. Addition of the cosolvent isopropanol to MA-80 increased the solubility of isopropanol at each surfactant concentration but did not demonstrate any particular trend in solubilization rate of isopropanol for the other surfactants tested. In the case of anionic surfactants (MA-80 and SDS), the solubility and solubilization rate increase with increasing electrolyte concentration for all surfactant concentrations. 

The study of inverse adhesive emulsions has revealed the same features as direct emulsions [112,113]. Here again, it was shown that adhesion is favored when the surfactant becomes less soluble in the continuous phase [113]. This can be tested experimentally by using binary mixtures of oils, one in which the surfactant is soluble and another one in which the surfactant is insoluble. For example, water droplets can be stabilized in mineral oil by sorbitan monooleate (Span 80). This surfactant is soluble in dodecane whereas it is not in silicon oil. The affinity of the surfactant for the organic solvent can be tuned by mixing dodecane and silicon oil. As shown in Fig. 2.38, the energy of adhesion between water droplets strongly varies as the ratio of the mixture is changed. A sharp rise is noted as the surfactant... 

In the experiments described by Pays et al. [44], the double globules were composed of dodecane and the surfactants used were sorbitan monooleate (SMO), which is oil soluble, and the water-soluble SDS. The concentrations of both surfactants were fixed and the initial internal droplet volume fraction was varied between 5% and 35%. The coalescence frequency was determined from a simple experiment in which the globule surface was totally saturated by the water droplets. For... 

Nonionic surfactants such as sorbitan monooleate yield more stable emulsions than do ionic surfactants, However, the latices from inverse emulsion polymerizations are generally less stable than those from conventional emulsion polymerizations, and flocculation is a problem. 

Further evidence for the theory of stabilisation due to enhanced intermolecu-lar surfactant interactions was presented recently [112]. Two different surfactants were employed to stabilise w/o HIPEs sorbitan monooleate, a monomeric surfactant, and a polymeric surfactant. Salt addition enhanced the stability of the HIPEs, but more so in the presence of the polymeric surfactant. Again, the interactions between the salt and the surfactant were held responsible. The polymer contained ionic groups, which enabled it to interact strongly with the salt sorbitan monooleate, however, possesses groups which can only participate in hydrogen-bonding. 

Researchers at Unilever [128] discovered that the surfactant used to form the HIPEs must be of low HLB value (between 2 and 6), as would be expected for w/o emulsions. The optimum surfactant was sorbitan monooleate (Span 80), which has an HLB value of 4.3. However, the HLB number of the surfactant is not the only criterion for the preparation of stable HIPEs the chemical nature was also found to be of importance [105]. 

Water-in-oil concentrated emulsions have also been utilised in the preparation of polymer latexes, from hydrophilic, water-soluble monomers. Kim and Ruckenstein [178] reported the preparation of polyacrylamide particles from a HIPE of aqueous acrylamide solution in a non-polar organic solvent, such as decane, stabilised by sorbitan monooleate (Span 80). The stability of the emulsion decreased when the weight fraction of acrylamide in the aqueous phase exceeded 0.2, since acrylamide is more hydrophobic than water. Another point of note is that the molecular weights obtained were lower compared to solution polymerisation of acrylamide. This was probably due to a degree of termination by chain transfer from the tertiary hydroxyl groups on the surfactant head group. 

Low-molecular-weight surfactants ( emulsifiers ) are important ingredients in food products. The types of surfactants most commonly studied in food colloids research are phospholipids (lecithin), mono/diglycerides (particularly glycerol monostearate), polysorbates (Tweens), sorbitan monostearate or monooleate (Spans), and sucrose esters. These small lipid-based amphiphiles can typically lower the interfacial tension to a greater extent than the macromolecular amphiphiles such as proteins and certain gums (Bos and van Vliet, 2001). 

Peters and Luthy (1993, 1994) performed a detailed analysis of the equilibrium behavior of solvent coal tar water mixtures in work that was complementary to column studies performed by Roy, et. al. (1995). Peters and Luthy successfully modeled ternary phase diagrams of coal tar/n-butylamine/water systems. In addition, Peters and Luthy identified n-butylamine as the leading solvent for coal tar extraction. Pennell and Abriola (1993) report the solubilization of residual dodecane in Ottawa sand using a nonionic surfactant, polyoxyethylene sorbitan monooleate, which achieved a 5 order of magnitude increase over the aqueous solubility, but is still 7 times less than the equilibrium batch solubility with the same surfactant system. 

The overall objective of this research was to evaluate the effects of cosolvent addition on the ability of an ethoxylated nonionic surfactant to recover PCE from a heterogeneous, 2-D system. The specific tasks of this work were to (a) quantify the PCE solubilization rate and capacity in the presence and absence of a representative cosolvent (EtOH) and (b) investigate the effects of EtOH addition on surfactant delivery, plume migration and PCE recovery in a 2-D, layered sand tank. A representative nonionic surfactant, polyoxyethylated (POE) (20) sorbitan monooleate (Tween 80), was selected for study because of its capacity to solubilize PCE ( 0.7 g PCE/g surf at 20°C) and relatively high interfacial tension with PCE (5 dynes/cm). EtOH was chosen as the representative cosolvent because of its relatively low density (p = 0.79 g/cm1) and regulatory acceptance. 

Polyoxyethylene (POE) (20) sorbitan monooleate (Tween 80, Lot 36218, ICI Surfactants, Inc.) was used as received with no further purification. The average molecular weight of Tween 80 is 1310 g/mole, the density is 1.07 g/cm3, the hydrophile-lipophile balance (HLB) is 15, the critical micelle... 

The selection of the mixture of surfactants should be made after the careful consideration of the interfacial film, as described in Section 4.2.3. In most cases, the most stable emulsions are made from surfactants that contain the same number of hydrocarbon chains (e.g., sorbitan monooleate and polyoxyethylene sorbitan monooleate). The optimum HLB value of the surfactants in the emulsion predicts the smallest mean droplet size that produces a stable emulsion. 

Let us first consider an inverted W/O emulsion made of 10% of 0.1 M NaCl large droplets dispersed in sorbitan monooleate (Span 80), a liquid surfactant which also acts as the dispersing continuous phase. At this low droplet volume fraction, the rheological properties of the premixed emulsion is essentially determined by the continuous medium. The rheological behavior of the oil phase can be described as follows it exhibits a Newtonian behavior with a viscosity of 1 Pa s up to 1000 s 1 and a pronounced shear thinning behavior above this threshold value. Between 1000 s 1 and 3000 s1, although the stress is approximately unchanged, the viscosity ratio is increased by a factor of 4. 

Data on the effects of surfactants on the hydrolysis of aryl sulfate esters have become available only recently. A non-ionic heterodisperse polyoxyethylene sorbitan monooleate surfactant, Polysorbate 80, was found to increase the observed rate constant for the acid-catalyzed hydrolysis of potassium 2,4-dichloronaphthyl sulfate by a factor of 16-3 at a surfactant concentration of 8 g/1, but an additional 5-fold increase... 

Sodium decyl sulfate, non-ionic surfactants such as polyoxyethyl-ene(20) sorbitan monooleate, and the polymer polyvinylpyrrolidone have been shown to enhance the photobleaching of riboflavin (Kostenbauder and DeLuca, 1963 Kostenbauder et al., 1965). The effects of surfactants and other macromolecules on the rate constants for the photobleaching of riboflavin and acetylriboflavin together with the relative fluorescent... 

Micellar catalysis of the photobleaching of riboflavin and riboflavin-5-phosphate was investigated in a recent e.s.r. study of the effects of polyoxyethylene(20) sorbitan monooleate and sodium dodecyl sulfate on the rate of formation and decay of an intermediate semiquinone radical (Kowarski, 1969). In the photodegradation of riboflavin-6-phosphate, both the rate of formation of the semiquinone radical and the rate constant for its decay were appreciably enhanced by the anionic and the non-ionic surfactant (Table 19). Similarly, the catalysis of the photobleaching of riboflavin by sodium dodecyl sulfate was found to be related to an increased rate of formation of the semiquinone radical. Hence, the micellar catalysis of the photodegradation of riboflavin and riboflavin-5-phosphate is the consequence of a combined effect of an increased rate of semiquinone radical formation and an accelerated rate of its decay (Kowarski, 1969). 

TABLE 1. Experimental conditions used in preparing poly(acrylamide-co-ammonium acrylate) with sorbitan monooleate as a surfactant. ... 

Tween 80 (also known as At-Plus 109 and Polysorbate 80) is a polyoxyethylene sorbitan monooleate and was obtained from Atlas Chemical Industries, Inc. This nonionic surfactant has an HLB (hydrophile-lipophile balance) of 15.0 and is used as an emulsifier, solubilizer, and dispersant. It was used without further purification at the 0.1% (w/v) level in partitioning and greenhouse herbicidal evaluations as described below. 

---