Mixtures of anionic surfactants

The target HLB can be obtained by using a mixture of anionic surfactant (HLB = 9.4) and nonionic surfactant HLB = 16.7) in the right proportions (1 3.75 based on the formula in Table 3). Such mixing of anionic and nonionic surfactants is expected to lower the individual CMC s and thus an increase of the soil solubilization capacity. The surfactants in the product should be in spherical micelle phase to give a transparent/translucent appearance and small viscosity (Table 6). 

Scamehorn et. al. (19) reported the adsorption isotherms for a binary mixture of anionic surfactants. A formal adsorption model developed for single surfactant systems ( ) was extended to this binary system and shown to accurately describe the mixed adsorption isotherms (19). That theoretically based model was very complex and is probably not feasible to extend beyond two surfactant components. 

Scamehorn, J.F., Schecter, R.S. and Wade, W.H. (1982) Adsorption of surfactants on mineral oxide surfaces from aqueous solutions. II. Binary mixtures of anionic surfactants. /. Colloid Interface Sci., 85, 479-93. 

The adsorption of binary mixtures of anionic surfactants of a homologous series (sodium octyl sulfate and sodium dodecyl sulfate) on alpha aluminum oxide was measured. A thermodynamic model was developed to describe ideal mixed admicelle (adsorbed surfactant bilayer) formation, for concentrations between the critical admicelle concentration and the critical micelle concentration. Specific... 

Scamehorn et. al. expanded a single component adsorption equation ( ) to describe the adsorption of binary mixtures of anionic surfactants of a homologous series (1 1). Ideal solution theory was found to describe the system fairly well. The mixed adsorption equations worked very well in predicting the mixture adsorption, but the equations were complex and would be difficult to extend beyond a binary system. 

Scamehorn et. al. ( ) also developed a reduced adsorption equation to describe the adsorption of mixtures of anionic surfactants, which are members of homologous series. The equations were semi-empirical and were based on ideal solution theory and the theory of corresponding states. To apply these equations, a critical concentration for each pure component in the mixture is chosen, so that when the equilibrium concentrations of the pure component adsorption isotherms are divided by their critical concentrations, the adsorption isotherms would coincide. The advantage of... 

The adsorption of binary mixtures of anionic surfactants in the bilayer region has also been modeled by using just the pure component adsorption isotherms and ideal solution theory to describe the formation of mixed admicelles (3 ). Positive deviation from ideality in the mixed admicelle phase was reported, and the non-ideality was attributed to the planar shape of the admicelle. However, a computational error was made in comparison of the ideal solution theory equations to the experimental data, even though the theoretical equations presented were correct. Thus, the positive deviation from ideal mixed admicelle formation was in error. 

Micelles and monolayers composed of homologous mixtures of anionic surfactants can be approximately described by ideal solution theory to model the mixed surfactant aggregate (35). Therefore, surprising that mixed admicelles composed surfactants also obey ideal solution theory, important to note that this is true at all levels within Region II, as seen by the... 

Scamehorn, J. F., R. S. Schechter, and W. H. Wade (1982b), Adsorption of Surfactants on Mineral Oxide Surfaces from Aqueous Solutions. II. Binary Mixtures of Anionic Surfactants, J. Colloid Interface Sci. 85, 479-493. 

Mixture of Anionic Surfactants onto Alumina. Most EOR surfactants are mixtures of isomers, but these mixtures are too complex for application of basic theory. In contrast, the effectiveness of ideal solution theory in explaining region II adsorption for binary mixtures of anionic surfactants has been demonstrated [5Jj. These controlled isomeric mixtures allow application of the ideal solution theory. The application of this theory utilized a reduced adsorption equation for mixtures of anionic surfactants [52]. The parameters for this reduced... 

There have been a number of studies concerning mixtures of anionic surfactants with either nonionics or cationics, but only a very few have addressed the kinetics of these complex systems [75, 76]. When looking at enhancement of anionic surfactant adsorption at the water-cellulose interface, Paria et al. [75] fonnd that the greatest rate increase could be achieved by pretreating the snrface with cationic surfactant, rather than using a mixed solution. 

Mixtures of surfactants exhibit different levels of synergism depending on the charge and molecular structure of the individual surfactant components [7]. When ionic and nonionic surfactants are mixed, the properties of the two surfactants are maintained. In mixtures of cationic and nonionic surfactants, in general, no synergistic or antagonistic effect is observed. In mixtures of anionic surfactants and some nonionic surfactants such as alcohol ethoxylates, however, some synergistic effect is observed. In contrast to mixtures of ionic and nonionic surfactants, mixtures of anionic and cationic surfactants have properties that are drastically different from their ionic surfactant components. These differences will be discussed in detail below. 

A mixture of anionic surfactants (salts of fatty acids (currently named soaps), alkyl sulfates and alkyl sulfonates may be determined by three titrations. These three surfactants are titrated using dichlorofluorescein as indicator a dimidium bromide and disulfine blue mixture are used for titration of alkyl sulfates and alkyl sulfonates, while disulfine blue is used for alkyl sulfonates titration after acid hydrolysis (Cozzoli, 1993). 

In a mixture of anionic surfactant and starch, aqueous iodine exhibits a color range from pure blue to violet, depending on the characteristics of the surfactant (32,33). With proper standards, it is possible to distinguish between short and long alkyl chains, and between linear and branched chains. 

An automated electronic tongue consisting of an array of potentiometric sensors and an artificial neural network (ANN) was developed to resolve mixtures of anionic surfactants. The sensor array was formed by five different flow-through sensors for anionic surfactants, based on polyvinyl chloride membranes having cross-sensitivity features. 

---