Surfactants TWEEN

Tuz Golu (lake), 5 784 Tversky similarity, 6 8 T vessicant agent, 5 816 physical properties, 5 817t Twaron fiber, 13 373 Tween surfactants, 24 150 12-membered ring macrolides, 15 272, 275t 2,6-TDI, reaction with a polyether triol, 25 459. See also Toluene diisocyanate (TDI)... 

ST68 Sonicated Span/ Tween surfactant mixture air Animal studies [19]... 

Adhesion Tensions and Tar Sand Extraction with Tween Surfactants. Mea-surement of the adhesion tension (t) allows the determination of the wettability of a given solid by a given liquid or surfactant solution. Measurements of adhesion tension between both bitumen or clay surfaces and various surfactant solutions is thus highly relevant to a study of the effects of surfactants in the separation of bitumen from Athabasca tar sand. 

Fig. 10 relates the composite extraction index (see above) obtained in the low-shear aqueous test system for these Tween surfactants, and adhesion tensions measured against various solids. Adhesion tensions against platinum and bitumen saturated pyrophyllite are irregularly related to tar sand extraction, while the adhesion tension against a fresh pyrophyllite surface is linearly (inversely) related to tar sand extraction. This is the first linear correlation between a measurable property of a surfactant solution and tar sand extraction which we have been able to obtain, and there appears to be no such finding in the literature. Fig. 11 gives the relations between extraction of bitumen with the paddle mill, solvent-aqueous-surfactant extraction and adhesion tensions measured against platinum, bitumen saturated pyrophyllite and hydrated (48 hours in water) pyrophyllite. 

Figure 8, Adhesion tension vs, HLB, Tween surfactants. (9) Fresh surface of pyrophyllite (O) hydrated pyrophyHite (O) bitumen-saturated pyrophyl-...

Figure 9. Adhesion tension and HLB vs. spreading tension, Tween surfactants. Symbols as in Figure 8 ([J) mica f ) spreading tension against a 20% (w/v) solution of bitumen in kerosene.

Figure 10, Aqueous-surfactant extraction of tar sand (composite extraction index) vs, adhesion tension against various solids for Tween surfactants (0.02% w/v). Symbols as in Figure 8.

Yeh, D.H., Pennell, K.D., and Pavlostathis, S.G. (1999). Effect of Tween surfactants on methanogenesis and microbial reductive dechlorination of hexachlorobenzene. Environ. Toxicol. Chem., 18, 1408-1416. 

Scheme 4.6 Molecular structures of the Triton surfactants and Tween surfactants used for C02 absorption. Reproduced from Ref. [83] by permission of The Royal Society of Chemistry...

Typically, the polysorbate (Tween) surfactants have HLB values in the range 9.6-16.7 the sorbitan ester (Span) surfactants have HLBs in the lower range of 1.8-8.6. 

Ionic detergents, such as cetyltrimethylammonium bromide or sodium dodecyl sulfate, give pore sizes between 2 and 4 nm, whereas nonionic surfactants such as the Pluronics and the Tween surfactant series (ethoxylated sorbitan esters) give materials with larger pores (around 10 nm) and thicker walls (Table 18.1). 

Of course, the surfactant molecules can also phase separate to form micelles within the solvent as shown in Fig. 10.30, in addition to other liquid aystal phases which can strongly influence particle nucleation and growth. Fot example, the formation of a hexagonal liquid crystal phase for 55% Tween surfactant dissolved in 45% water caused crystal growth of copper sulfate to be much inhibited, producing monosize dispersions of crystals around 2 pm in diameter. ... 

Poly(ethylene glycol) Tween surfactant and water 2004MAH... 

Ethoxylated derivatives of Spans (Tweens) are produced by the reaction of ethylene oxide on any hydroxyl group remaining on the sorbitan ester group. Alternatively, the sorbitol is first ethoxylated and then esterified. However, the final product has different surfactant properties to the Tweens. Some examples of Tween surfactants are given below. 

The ethoxylated derivatives of Spans (Tweens) are produced by reaction of ethylene oxide on any hydroxyl group remaining on the sorbitan ester group. Alternatively, the sorbitol is first ethoxylated and then esterified. However, the final product has different surfactant properties to the Tweens. Some examples of Tween surfactants are polyoxyethylene (20) sorbitan monolaurate. Tween 20 polyoxyethylene (20) sorbitan monopalmitate, Tween 40 polyoxyethylene (20) sorbitan monostearate. Tween 60 polyoxyethylene (20) sorbitan mono-oleate. Tween 80 and polyoxyethylene (20) sorbitan tristearate. Tween 65 and polyoxyethylene (20) sorbitan tri-oleate. Tween 85. 

The second phase of biotic screening evaluated the effect of Tween surfactants on the reductive dechlorination of HCB by the mixed culture. Experiments were conducted in 28-mL serum tubes sealed with Teflon-lined rubber septa and aluminum crimps. Each tube contained HCB (-140 fig/L) dissolved in methanol, glucose, and Tween surfactant at concentrations of either 10, 50, 200, or 1,000 mg/L. At each sampling time, the contents of the tubes were extr ted with isooctane followed by an analysis for HCB, dechlorination products and excess gas production. The following parameters were measured total gas and methane production, pH, ORP, particulate organic carbon, volatile fatty acids (VFAs), and total chemical oxygen demand (COD). 

Hexachlorobenzene concentration profiles and total gas production for the glucose-fed culture exposed to three initial surfactant (Tween series) loadings are shown in Figure 4. At surfactant concentrations of 10 and 200 mg/L, total gas production was identical to that of the reference (without surfactant amendment). As the initial surfactant concentration was increased to 1,000 mg/L (Figure 4C), total gas production was equal to or exceeded the reference case. These data suggest that many of the Tween surfactants were subject to biodegradation. Both the rate and extent of HCB disappearance decreased, however, as the initial surfactant concentration was increased from 10 to 1,000 mg/L. The HCB concentration in azide-amended controls did not vary significantly over die... 

Figure 3. Methane production by glucose-fed cultures in presence of Tween and non-Tween surfactants at an initial concentration of200mg/L from Yeh et al. (18).

The sorption of HCB by Appling soil was evaluated as a function of surfactant (Tween 80) concentration and mixing time. Tween 80 was selected for these experiments because it readily dissolves in water and remains in solution. Although several of the Tween surfactants (i.e.. Tween 60,61 and 65) were less inhibitory toward HCB dechlorination (Figure 4D-F), these surfactants were more difficult to dissolve in water and were susceptible to the formation of separate phases (e.g., precipitate). The formation of surfactant-rich phases by Tween 60 has also been reported by Shaiu et al. (22). 

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