Nonionic surfactants characterization

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

Nonionic surfactants are often characterized ia terms of their hydrophi1 e—1 ipophi1 e balance (HLB) number (see Emulsions). For simple alcohol... 

What characterizes surfactants is their ability to adsorb onto surfaces and to modify the surface properties. At the gas/liquid interface this leads to a reduction in surface tension. Fig. 4.1 shows the dependence of surface tension on the concentration for different surfactant types [39]. It is obvious from this figure that the nonionic surfactants have a lower surface tension for the same alkyl chain length and concentration than the ionic surfactants. The second effect which can be seen from Fig. 4.1 is the discontinuity of the surface tension-concentration curves with a constant value for the surface tension above this point. The breakpoint of the curves can be correlated to the critical micelle concentration (cmc) above which the formation of micellar aggregates can be observed in the bulk phase. These micelles are characteristic for the ability of surfactants to solubilize hydrophobic substances in aqueous solution. So the concentration of surfactant in the washing liquor has at least to be right above the cmc. 

Levine, L.H. Garland, J.L. Johnson, J.V. HPLC/ESI-Quadrupole Ion Trap-MS for Characterization and Direct Quantification of Amphoteric and Nonionic Surfactants in Aqueous Samples. Anal. Chem. 2002, 74, 2064-2071. 

Siekmann B. and Westesen K., Melt-homogenized sohd hpid nanoparticles stabilized by the nonionic surfactant tyloxapol. II. Physicochemical characterization and lyo-philization, Pharm. Pharmacol. Lett., 3, 225, 1994. 

Triton SP-Series surfactants use both a hydrophobe and an ethoxylate chain hydrophile. The surfactants are characterized by nonionic surfactant features such as good detergency, surface activity, and wetting. When the pH of an aqueous solution that contains a Triton SP-Series surfactant is reduced, the bond between the surfactant hydrophobe and hydrophile is permanently destroyed, thus eliminating surfactancy. This product was launched commercially in December 1996 and is currently available. The surfactants cannot be used in highly acidic environments. Other compounds that might be found in the contaminated waste, snch as phosphate, may interfere with the oil/water separation after snrfactant deactivation. All information is from the vendor and has not been independently verified. 

Al-Saden, A. A., A. T. Florence, T. K. Whatley, F. Puisieux, and C. Vautuion. 1982. Characterization of mixed nonionic surfactant micelles by photon correlation spectroscopy and viscb Hiylloid Interface Sci 86 51-56. 

Emulsions are two-phase systems formed from oil and water by the dispersion of one liquid (the internal phase) into the other (the external phase) and stabilized by at least one surfactant. Microemulsion, contrary to submicron emulsion (SME) or nanoemulsion, is a term used for a thermodynamically stable system characterized by a droplet size in the low nanorange (generally less than 30 nm). Microemulsions are also two-phase systems prepared from water, oil, and surfactant, but a cosurfactant is usually needed. These systems are prepared by a spontaneous process of self-emulsification with no input of external energy. Microemulsions are better described by the bicontinuous model consisting of a system in which water and oil are separated by an interfacial layer with significantly increased interface area. Consequently, more surfactant is needed for the preparation of microemulsion (around 10% compared with 0.1% for emulsions). Therefore, the nonionic-surfactants are preferred over the more toxic ionic surfactants. Cosurfactants in microemulsions are required to achieve very low interfacial tensions that allow self-emulsification and thermodynamic stability. Moreover, cosurfactants are essential for lowering the rigidity and the viscosity of the interfacial film and are responsible for the optical transparency of microemulsions [136]. 

Aramendia et al. [20] have compared the nonreactive sodium lauryl sulfate (SLS) to the polymerizable sodium tetradecyl maleate (M14), synthesized according to the procedure described by Stahler [21] in the seeded polymerization of methyl methacrylate/butyl acry-late/acrylic acid using tert-butyl hydroperoxide and ascorbic acid as initiator. Nonyl phenol 30 EO (NP30) was the nonionic surfactant used in the seed latex. Latex characterization... 

The hydrophilicity of nonionic surfactants can be characterized numerically as their hydrophile-lipophile balance (HLB). An HLB value of 3-6 indicates that the compound is a likely W/O emulsifier 7-9, a wetting agent 8-13, an O/W emulsifier 13-15, a detergent and 15-18, a solubilizer (of oil or other nonpolar compounds) in water. The HLB values of some common compounds are presented in Table 34.12.170 An HLB value of 8.0 is shown in Table 34.12 for lecithin, but manufacturers are able to supply modified lecithins with values of2-12. 

We have previously reported on the coupling of an SEC to a mass spectrometer operated in the electrospray mode of ionization and its application to the molecular weight characterization of octylphenoxy-poly(ethoxy)ethanol oligomers (20). The analysis of nonionic surfactants... 

Cuzzola et al. [25-26] identified and characterized Fenton oxidation products of lauryl sulfate and AES. The Fenton reaction is a frequently applied oxidative treatment in STPs. The degradation prodncts of anionic surfactants have been objects of stndy as well, because their biodegradation products might involve the loss of the snlfate group, resulting in essentially nonionic surfactants (see below). According to Schroder [27], the biodegradation of nonylphenol ethoxy sulfates does not involve a loss of the sulfate. 

L.H. Levine, J.L. Garland, J.V. Johnson, LC-ESl-quadrupole ion trap MS for characterization and direct quantification of amphoteric and nonionic surfactants in aqueous samples. Anal. Chem., 74 (2002) 2064. 

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. 

In the present study, we have examined other transport properties of 0/W microemulsions containing the nonionic surfactant Tween 60 whose dielectric and conductivity properties have been previously characterized. We have chosen properties (water self-diffusion, ionic conductivity at low frequencies, and thermal conductivity) that can be analyzed using the same mixture theory, and which therefore can be compared in a consistent way. Limited transport data are presented from other microemulsions as well. 

A series of related experiments investigated nonionic surfactant sorption onto soil, mechanisms of nonionic surfactant solubilization of polycyclic aromatic hydrocarbon (PAH) compounds from soil, and microbial mineralization of phenanthrene in soil-aqueous systems with nonionic surfactants. Surfactant solubilization of PAH from soil at equilibrium can be characterized with a physicochemical model by using parameters obtained from independent tests in aqueous and soil-aqueous systems. The microbial degradation of phenanthrene in soil-aqueous systems is inhibited by addition of alkyl ethoxylate, alkylphenyl ethoxylate, or sorbitan- (Tween-) type nonionic surfactants at doses that result in micellar solubilization of phenanthrene from soil. Available data suggest that the inhibitory effect on phenanthrene biodegradation is reversible and not a specific, toxic effect. 

Phenanthrene Solubilization. A model characterizing the distribution of HOC in systems of soil and micellar nonionic surfactant solution was described previously (7). In this model HOC is assumed to partition among three distinct compartments the soil, the micellar pseudophase, and the aqueous pseudophase. The solubilization model accounts for the partitioning of HOC between the micellar pseudophase and the aqueous pseudophase, the increase in apparent HOC solubility associated with nonionic surfactant monomers in the aqueous pseudophase, the sorption of surfactant onto soil, and the increase in fractional organic carbon content of a soil as a result of surfactant sorption. Evaluation of the model with experimental data was described by Edwards et al. (12). 

McNamee, C.E., Tsujii, Y, and Matsumoto, M., Physicochemical characterization of an anatase TiO2 surface and the adsoiption of a nonionic surfactant An atomic force microscopy sliidy, Langmuir, 21. 11283, 2005. 

In contrast to the electrostatic stabilization provided by SDS [40,41 ], the nonionic surfactant NP-40 imparts a steric repulsion force between two interactive hairy particles [42, 43]. Stable St mini-emulsions with NP-40 in combination with various coemulsifiers (CA, HD, DMA or SMA) were prepared and characterized [ 13]. The rate of Ostwald ripening for these mini-emulsions decreases in the series CA>DMA>HDsSMA. 

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