Anionic-nonionic mixed surfactants

And rez JM, Bracho CL, Sereno S, Salager JL (1993) Effect of surfactant concentration on the properties of anionic-nonionic mixed surfactant-oU-brine systems. Colloid Surface A 76 249-256... 

A recent study on electrokinetic removal of ethyl benzene from contaminated clay showed a promising use of anionic-nonionic mixed surfactants. Surfactant addition resulted in 1.6-2.4-fold more removal than afforded by EK alone, and a mixed surfactant system, including 0.5% SDS and 2.0% PANNOX 110 (nonyl phenol polyethylene glycol ether) permitted optimal ethyl benzene removal (98%). This indicated that, in the presence of mixed surfactant micelles, the zeta potential of the soil particles significantly increased compared with that seen when anionic surfactant micelles were formed, and electrolytic mobility was thus enhanced (Yuan and Weng, 2004). The use of anionic-nonionic mixed surfactants in EK will also improve the desorption and migration of PAHs. 

Zhou W, Zhu L (2008). Enhanced soil flushing of phenanthrene by anionic-nonionic mixed surfactant. Water Research 42(1-2) 101-108. 

The surfactants used in the emulsion polymerization of acryhc monomers are classified as anionic, cationic, or nonionic. Anionic surfactants, such as salts of alkyl sulfates and alkylarene sulfates and phosphates, or nonionic surfactants, such as alkyl or aryl polyoxyethylenes, are most common (87,98—101). Mixed anionic—nonionic surfactant systems are also widely utilized (102—105). 

Small micelles in dilute solution close to the CMC are generally beheved to be spherical. Under other conditions, micellar materials can assume stmctures such as oblate and prolate spheroids, vesicles (double layers), rods, and lamellae (36,37). AH of these stmctures have been demonstrated under certain conditions, and a single surfactant can assume a number of stmctures, depending on surfactant, salt concentration, and temperature. In mixed surfactant solutions, micelles of each species may coexist, but usually mixed micelles are formed. Anionic-nonionic mixtures are of technical importance and their properties have been studied (38,39). 

The critical micellar concentrations of anionic/nonionic surfactant mixtures examined are low in a saline medium, so that, at the concentrations injected in practice, the chromatographic effects resulting from the respective adsorption of monomers are masked. Such surfactants propagate simultaneously in the medium in the form of mixed micelles. 

Surfactants such as sulfated fatty alcohols may be hydrated to a higher extent than the fatty alcohols alone and thus stabilize o/w emulsions. The eombination of an anionic and a nonionic srrrfactant has proved to be partieularly effeetive, sinee the electrostatic repulsion forces between the ionie surfaetant moleeules at the interface are reduced by the incorporation of nonionic molecules, thus improving the emulsion stability. The combination of cetyl/stearyl sulfate (Lanette E) and eetyl/ stearyl alcohol (Lanette 0) to yield an emulsifying eetyl/stearyl aleohol (Lanette N) is an example of this approach. The polar properties of this srrrfactant mixtrrre are dominant, and o/w creams are formed. In contrast to w/o systems, the stabilizing effect of the surfactant mixtirre is not mainly due to adsorption at the interfaee. Instead, the mixed surfactants are highly hydrated and fonn a lamellar network, whieh is... 

When anionic and cationic surfactants are mixed they strongly interact, and it could even be said that they almost react to produce a catanionic species, which is essentially a new surfactant, in which the two hydrophilic groups have merged into a nonionic or a somehow amphoteric head attached to a double tail. The first consequence is that the new daughter species has... 

Anton RE, Salager JL, Graciaa A, Lachaise J (1992) Surfactant-oil-water systems near the affinity inversion - Part Vlll Optimum Formulation and phase behavior of mixed anionic-nonionic systems versus temperature. J Dispers Sci Technol 13 565... 

If the mixed micelle model already presented is used to predict the ionic surfactant monomer concentration, and a simple concentration—based solubility product is assumed to hold between the unbound counterion and monomer, the salinity tolerance of an anionic/nonionic surfactant mixture can be accurately predicted (91). supporting this view of the mechanism of tolerance enhancement by nonionic surfactant. 

In this paper, we report the solution properties of sodium dodecyl sulfate (SDS)-alkyl poly(oxyethylene) ether (CjjPOEjj) mixed systems with addition of azo oil dyes (4-NH2, 4-OH). The 4-NH2 dye interacts with anionic surfactants such as SDS (11,12), while 4-OH dye Interacts with nonionic surfactants such as C jPOEn (13). However, 4-NH2 is dependent on the molecular characteristics of the nonionic surfactant in the anlonlc-nonlonic mixed surfactant systems, while in the case of 4-OH, the fading phenomena of the dye is observed in the solubilized solution. This fading rate is dependent on the molecular characteristics of nonionic surfactant as well as mixed micelle formation. We discuss the differences in solution properles of azo oil dyes in the different mixed surfactant systems. 

The second factor, namely the head group interaction, can also influence the surface properties of mixed surfactant markedly. In particular, anionic/catlonic surfactant mixtures exhibit the largest effect (17,18). In nonionic/anionic surfactant mixtures, synergistic effects can still take place to a significant extent, as revealed in Figure 3 (pH 10.9, nonionic amine oxide with anionic long chain sulfate), since insertion of nonionic surfactant molecules into an ionic surfactant molecular assembly minimises electrostatic repulsion (19). 

Mixed surfactant systems are frequently used in practice. For example, latexes are often prepared in the presence of an anionic surfactant. Later, a nonionic surfactant may be added in order to enhance the colloidal stability of the system. 

The third factor determining the distribution of surfactant between the solution and the surface phase is represented by the third term from the right in Equation 17. It involves the interaction between the two surfactant species, i.e. Xl2 Analysis of the cmc of mixed surfactant systems (6-7) reveals that there is normally a net attraction when anionic and nonionic surfactants are mixed. This corresponds to a negative Xi2 suggested explanation is that the... 

Marszall (1988) studied the effect of electrolytes on the cloud point of mixed ionic-nonionic surfactant solutions such as SDS and Triton X-100. It was found that the cloud point of the mixed micellar solutions is drastically lowered by a variety of electrolytes at considerably lower concentrations than those affecting the cloud point of nonionic surfactants used alone. The results indicate that the factors affecting the cloud point phenomena of mixed surfactants at very low concentrations of ionic surfactants and electrolytes are primarily electrostatic in nature. The change in the original charge distribution of mixed micelles at a Lxed SDS-Triton X-100 ratio (one molecule per micelle), as indicated by the cloud point measurements as a function of electrolyte concentration, depends mostly on the valency number of the cations (counterions) and to some extent on the kind of the anion (co-ion) and is independent of the type of monovalent cation. 

Penfold et al. [62] have also used neutron reflectivity to study the adsorption (structure and composition) of the mixed anionic/nonionic surfactants of SDS and C12E6 at the hydrophilic silica-solution interface. This is rather different case to the cationic/nonionic mixtures, as the anionic SDS has no affinity for the anionic silica surface in the absence of the Ci2E6. The neutron reflectivity measurements, made by changing the isotopic labelling of the two surfactants and the solvent, show that SDS is coadsorbed at the interface in the presence of the Ci2E6 nonionic surfactant. The variations in the adsorbed amount, composition, and the structure of the adsorbed bilayer reflect the very different affinities of the two surfactants for the surface. This is shown in Fig. 7, where the adsorbed amount and composition is plotted as a function of the solution composition. 

With many industrial formulations, surfactants of different kinds are mixed together, for example anionics and nonionics. The nonionic surfactant molecules shield the repulsion between the negative head groups in the micelle, and consequently there will be a net interaction between the two types of molecules. Another example is the case when anionic and cationic surfactants are mixed, whereby a very strong interaction will take place between the oppositely charged surfactant molecules. To account for this interaction. Equation (3.25) must be modified by introducing activity coefficients of the surfactants,/j" and/2 in the micelle. 

Use of mixed surfactant films In many cases the used of mixed surfactants (e.g., anionic and nonionic or long chain alcohols) can reduce coalescence as a result of several effects a high Gibbs elasticity high surface viscosity and hindered diffusion of surfactant molecules from the film. 

Marti-Mestres, G., F., R. Nielloud, R. Marti, and H. Maillols, 1997. Optimisation with experimental design of nonionic, anionic and amphoteric surfactants in a mixed system. Drug Dev. Ind. Pharm. 23 (10) 993—998. 

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