Extraction preconcentration with anionic surfactants in acidic solutions

Extraction preconcentration with anionic surfactants in acidic solutions on the basis of the cloud point was studied. Advantages and disadvantages of this method were considered. Conditions of the phase separation of some anionic surfactants (sodium decyl sulfate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate) in acidic solutions were studied. With the example of pyrene and its derivatives, it was demonstrated that these surfactants can be used for extraction preconcentration. Analytical characteristics of the determination of pyrene and its derivatives in model aqueous solutions by the fluorimetric method in combination with extraction preconcentration with sodium dodecyl sulfate were obtained     

Physicochemical properties of anionic triple-chain surfactants in alkaline solutions

A series of novel gemini cationic surfactants alkanediyl-alpha,omega-bis (hydroxyethylmethylhexadecylammonium bromide) with polymethylene spacer chain length of 4, 6, 8, and 10 carbon atoms was synthesized and characterized. Critical micellar concentrations of the gemini surfactants in aqueous solutions as determined by the surface tension and conductance measurements were observed to be in the range 1.39-3.63 microM. The critical micellar concentration was observed to increase initially with spacer length up to 6 methylene groups and to decrease thereafter with the increase in spacer length. The micellar microstructure in aqueous solutions examined through small angle neutron scattering (SANS) revealed that the extent of aggregation growth and variation in shapes of micelles strongly depend on head group polarity, spacer chain length, and temperature. The propensity to micellar growth with spacer chain length 4 was found to be much higher than with the longer spacer lengths. The fractional charge on the micelle increases with increased spacer chain length and temperature.     

Micellization in solutions of anionic surfactants with two ionogenic groups

Conductometry is employed to measure the critical micellization concentrations of homologous sodium monoalkyl sulfosuccinates with double-charged surface-active anions and alkyl radicals R containing 10–14 carbon atoms (ROOCCH₂CH(SO₃Na)COONa). The degrees of counterion binding with micelles and the Gibbs energy ΔG ^m of micellization are calculated. The incorporation of an additional ionogenic group into a surfactant molecule somewhat decreases ΔG ^m. For the examined series of surfactants, the increment of ΔG ^m due to one methylene group is ?4.44 kJ/mol.     

Interaction between anionic surfactants and oil dye in the aqueous solutions

The interactions between 4-phenylazo-1-naphthylamine and 6 sodium alkyl sulfates have been studied by a spectrophotometer. At lower concentrations than each CMC, 3 surfactants (octyl, decyl and dodecyl sulfate) and the dye formed hydrophobic complexes with a binding molar ratio of 11, while the others (tetradecyl, hexadecyl, and octadecyl sulfate) and the dye made 21 complexes. The wavelength of the maximal absorption is 440 nm in the former, and 520 nm in the latter. In the neighborhood of each CMC region, thermochromism occurred in every surfactant solution. The temperature at which the maximal absorption moved from 520 nm to 440 nm increased with an increase in the number of carbon atoms in the surfactant molecules. At higher concentrations than each CMC, in the case of the octyl and decyl sulfate, the maximal absorption occurred at the 440 nm band above room temperature; in the case of the dodecyl, tetradecyl, and hexadecyl sulfates, the maximal absorption occurred at the 520 nm band, regardless of temperature. In the case of octadecyl sulfate, the maximal absorption moved from 610 nm to 520 nm with increase in temperature. It is found that the protonation equilibrium of the dye is dependent on the micellar structure through the differences in the alkyl chain lengths of the surfactants, and the differences in interaction with surfactant crystals.     

The competitive adsorption of counter-ions at the surface of anionic surfactants solution

We have determined the surface excess of surface active anion and counter-ions in a non-aqueous polar solution of anionic surfactants blends, as well as their distributions near the solution surface. The blends of two anionic surfactants, sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CDS), with different contents were used as solutes to prepare the solutions. According to the isotherms that are separately fitted to the pure SDS and the pure CDS solutions (C. Wang and H. Morgner, Langmuir, 2010, 26, 3121), CDS has a slightly but significantly higher surface excess than SDS (CDS is 14.8% higher) at the concentration of 0.04 molal kg(-1) solvent. Therefore, in this work we chose 0.04 molal kg(-1) solvent as total anion concentration and varied the contents of surfactants. From present experimental results, we found that the surface excess of anion increases slightly with the CDS in the bulk content. Importantly, the fractions of Cs(+) in cationic surface excess are higher than its contents in the bulk for all three solutions. This demonstrates that Cs(+) is more competitive than Na(+) in the adsorption. The surface structure of the solutions have been characterized by concentration-depth profiles, of Cs(+), Na(+) and of sulfur which is used to identify dodecyl sulfate. Those profiles evidence that Cs ions penetrate deeper than sodium ions into the layer formed by the heads of the anions, reducing the electrical potential of the surface more efficiently. This can be used to explain the adsorption competition between those two counter-ions. The cause that makes Cs(+) more competitive than Na(+) in the adsorption can be attributed to its less tightly bound solvation shell, and thus, to its effectively smaller ion size.     

Concentration of anionic surfactants from aqueous solutions on sorbents of various nature

Russian Chemical Bulletin - The sorption isotherms of anionic surfactants (AS) from the aqueous solution on eight polar and nonpolar sorbents were obtained. The equilibrium characteristics of...     

Photolysis of 1,2-dihydroquinolines in micellar solutions of anionic and cationic surfactants

The kinetics of the photolysis of substituted 1,2-dihydroquinolines (DHQ) in micellar solutions was studied by steady-state and flash photolysis. The photolysis mechanism depends dramatically on the location of DHQ molecules in micelles, which is governed by the surfactant nature. In micellar solutions of the anionic surfactant sodium dodecyl sulfate (SDS), where the DHQ molecules are located in the Stern layer, the intermediate species decay kinetics follows a first-order law. When DHQ is in neutral form (pH 4–12), the rate constant of the intermediate carbocation decay increases from 25 to 198 s^?1 with an increasing concentration of DHQ in micelles. The positive micellar catalysis is caused by the acceleration of the final product formation with the DHQ molecule via proton abstraction from the intermediate cation. The formation of several types of intermediate species—carbocations in the aqueous phase and aminyl radicals in micelles—is observed in micellar solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB) due to the preferential location of DHQ molecules in the micellar core. The carbocation decays via a pseudofirst-order reaction with a rate constant close to that in the aqueous solution. The lifetime of the DHQ aminyl radicals in the micellar solutions is longer by several orders of magnitude than the lifetime observed for homogeneous solutions of hydrocarbons and alcohols.     

Temperature-dependent vesicle formation of aqueous solutions of mixed cationic and anionic surfactants

The phase behavior of aqueous solutions of mixed cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) was examined at different temperatures (20, 30, 40, and 50 degrees C). While stable vesicles were formed in a narrow composition range on the SOS-rich side at 20 degrees C, the range widened remarkably when the temperature was raised to 30 degrees C. Thus, the vesicle region extended to cover almost the entire composition range, CTAB:SOS = 0.5:9.5-5.0:5.0, at the total surfactant concentrations of 50-70 mM on the SOS-rich side. To analyze the temperature dependence of this phase behavior of the mixed surfactant system, DSC and fluorescence polarization measurements were performed on the system. The experimental findings obtained revealed that pseudo-double-tailed CTAB/SOS complex, the major component of the bimolecular membrane formed by the surfactant mixture, undergoes a gel (Lbeta)-liquid crystal (Lalpha) phase transition at about 26 degrees C. This phenomenon was interpreted as showing that the bimolecular membrane has no curvature and is rigid and easy to precipitate at temperatures below the phase transition point, whereas it has a curvature and is loose enough to disperse in the solution as vesicles at temperatures above the phase transition point. Vesicles formed by the anionic/cationic surfactant complex were then stable at temperatures above the phase transition temperature of the complex.     

Synthesis and surface properties of anionic gemini surfactants with amide groups

Novel anionic gemini surfactants, 1,2-bis(N-beta-carboxypropanoyl-N-alkylamino)ethane (2CnenAm; n is hydrocarbon chain length of 6, 8, 10, 12, or 14), with two hydrocarbon chains, two carboxylate groups, and two amide groups, were synthesized by three-step reactions. Their solution properties were characterized by equilibrium and dynamic surface tension, steady-state fluorescence spectroscopy of pyrene, and dynamic light-scattering techniques. The surface tension measurements of 2CnenAm give low critical micelle concentrations (cmc), great efficiency in lowering the surface tension, and strong adsorption at air/water interface. Gemini surfactants behave normally with the logarithm of cmc decrease linearly with the chain length. In addition, adsorption and micellization behavior of 2CnenAm was estimated by parameter of pC20, cmc/C20, and standard free energy (DeltaG(0)mic and DeltaG(0)ads); they are significantly influenced by hydrocarbon chain length, and the adsorption is promoted more than the micellization as chain length becomes longer. The results of dynamic light-scattering and fluorescence quenching indicate that small micelles of 2CnenAm are observed at the concentrations above the cmc, and further large particles are also seen. Further, from the dynamic surface tension measurements, it is found that the shorter hydrocarbon chain length of 2CnenAm, the faster the rate of decrease of surface tension.     

Critical aggregation concentration in mixed solutions of anionic polyelectrolytes and cationic surfactants

We have examined the polymer/surfactant interaction in mixed aqueous solutions of cationic surfactants and anionic polyelectrolytes combining various techniques: tensiometry, potentiometry with surfactant-selective electrodes, and viscosimetry. We have investigated the role of varying polymer charge density, polymer concentration, surfactant chain length, polymer backbone rigidity, and molecular weight on the critical aggregation concentration (Cac) of mixed polymer/surfactant systems. The Cac of these systems, estimated from tensiometry and potentiometry, is found to be in close agreement. Different Cac variations with polymer charge density and surfactant chain length were observed with polymers having persistence lengths either smaller or larger than surfactant micelle size, which might reflect a different type of molecular organization in the polymer/surfactant complexes. The surfactant concentration at which the viscosity starts to decrease sharply is different from the Cac and probably reflects the polymer chain shrinkage due to surfactant binding.     

Phase behavior in mixtures of cationic and anionic surfactants in aqueous solutions

Phase behavior of cationic/anionic surfactant mixtures of the same chain length (n=10, 12 or 14) strongly depends on the molar ratio and actual concentration of the surfactants. Precipitation of catanionic surfactant and mixed micelles formation are observed over the concentration range investigated. Coacervate and liquid crystals are found to coexist in the transition region from crystalline catanionic surfactant to mixed micelles.The addition of oppositely charged surfactant diminishes the surface charge density at the mixed micelle/solution interface and enhances the apparent degree of counterion dissociation from mixed micelles. Cationic surfactants have a greater tendency to be incorporated in mixed micelles than anionic ones.     

Correlation between surface free energy of quartz and its wettability by aqueous solutions of nonionic, anionic and cationic surfactants

The measurements of the advancing contact angle for water, glycerol, diiodomethane and aqueous solutions of Triton X-100 (TX-100), Triton X-165 (TX-165), sodium dodecyl sulfate (SDDS), sodium hexadecyl sulfonate (SHDS), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB) on quartz surface were carried out. On the basis of the contact angles values obtained for water, glycerol and diiodomethane the values of the Lifshitz–van der Waals component and electron-acceptor and electron-donor parameters of the acid–base component of the surface free energy of quartz were determined. The determined components and parameters of the quartz surface free energy were used for interpretation of the influence of nonionic, anionic and cationic surfactants on the wettability of the quartz. From obtained results it was appeared that the wettability of quartz by nonionic and anionic surfactants practically does not depend on the surfactants concentration in the range corresponding to their unsaturated monolayer at water–air interface and that there is linear dependence between adhesional and surface tension of aqueous solution of these surfactants. This dependence for TX-100, TX-165, SDDS and SHDS can be expressed by lines which slopes are positive. This slope and components of quartz surface free energy indicate that the interaction between the water molecules and quartz surface might be stronger than those between the quartz and surfactants molecules. So, the surface excess of surfactants concentration at the quartz–water interface is probably negative, and the possibility of surfactants to adsorb at the quartz/water film–water interface is higher than at the quartz–water interface. This conclusion is confirmed by the values of the adhesion work of “pure” surfactants, aqueous solutions of surfactants and water to quartz surface. In the case of the cationic surfactants the relationship between adhesional and surface tension is more complicated than that for nonionic and anionic surfactants and indicates that the relationship between the adsorption of the cationic surfactant at water–air and quartz–water interface depends on the concentration of the surfactants in the bulk phase.     

Methods for the determination of anionic surfactants

Methods for the determination of synthetic anionic surfactants published in the past two decades are considered, and their advantages and disadvantages are demonstrated. Spectrophotometric and potentiometric (with the use of ion-selective electrodes) techniques, including flow injection analysis versions, are used for the determination of anionic surfactants. Chromatographic techniques (primarily, high-performance liquid chromatography) are most frequently used for the separation, preconcentration, and determination of anionic surfactants in complex mixtures. Spectrofluorimetry, voltammetry, and immunoassay did not find wide application.     

Molecular nature of hydrotropic action of sodium toluenesulfonate in micellar solutions of anionic surfactants

¹H and²³ Na high-resolution pulse Fourier transform NMR spectroscopy and ESR spectroscopy with spin probes (SP) and double paramagnetic probes (DPP) have been used in an investigation of the molecular nature of the hydrotropic action of sodium toluenesulfonate (NaTS) in micellar solutions of the anionic surfactants sodium dodecylsulfate and sodium alkylbenzenesulfonate. SP and DPP methods have been used in a detailed study of the influence of the hydrotrope (NaTS) on the structure and microviscosity of the anionic surfactant micelles and their permeability for molecules of the solvent (H₂O) and for diphilic, relatively insoluble organic substrates. From an analysis of the constants of hyperfine structure, the rotational correlation times _c and _c ¹ and the values of E _act ^T and _act ^T of the SPs (I) and (II) solubilized by surfactant micelles, it has been shown that in contrast to univalent electrolytes (NaCl), the NaTS has very little effect on the rotation rate or on the polarity of the local microenvironment of the solubilized SPs. The NaTS does give a significant increase in the capability of the micelles for solubilizing the SPs (I) and (II). It has been found that the addition of NaTS to the solution increases the looseness of the Stern layer of the NaDDS and NaABS micelles, while lowering the degree of binding of bivalent and univalent Me counterions with the surfactant aggregates.L. V. Pisarzhevskii Institute of Physical Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. S, pp. 606–614, September–October, 1991. Original article submitted May 31, 1990.     

Influence of the structure of amphiphilic anions on the Krafft temperature of micellar solutions of anionic surfactants

The influence of the structure of surfactants on the Krafft temperature T _k was studied for aqueous solutions of anionic surfactants containing the sulfate and sulfonate head groups, the hydrophilic (H) and lipophilic (L) fragments in amphiphilic anions, and various polar and C₈—C₁₈ hydrocarbon groups. The best statistical quality was obtained for the model with separate account of the effect of the H and L structural fragments on the T _k value.     

Synthesis of anionic sulphonate-crown ether surfactants

Two sulphonate-crown ether surfactants （sodium （4＇-dodecanoyldJbenzo-18-crown-6）-4＂（5＂）-sulpho- nate, ammonium （4＇-dodecanoyldibenzo-18-crown-6）-4＂（5＂）-sulphonate） were designed and synthesized via a two-step continuous method. The products were purified and characterized by IR. 1H NMR and elemental analysis. The physicochemical properties of the surfactants were studied by fluorescence, conductivity and dynamic light scattering techniques.     

Interactions of anionic surfactants with methemoglobin

The liquid crystal morphologies of symmetrical diacy phosphatidylcholine liposomes examined in this research study were found to be dependent on saturated hydrocarbon chain length. Both powder X-ray diffraction and synchrotron mid-IR spectromicroscopy indicate that phosphatidylcholines with short hydrocarbon tails (i.e. ten and twelve carbons) are more likely to form unilamellar liposomes while those with long hydrocarbon tails (i.e. eighteen and twenty carbons) are more likely to form multilamellar liposomes. Hydrocarbon chain lengths of fourteen and sixteen represent a transitional zone between these two liquid crystal morphologies. The FTIR spectra where a shoulder develops on the peak at wavenumber 1750 cm(-1) particularly highlights the change in the packing of adjacent molecules in the transitional zone.     

表面活性剂在低能固体表面上的吸附 Ⅲ: 聚苯乙烯胶乳粒子对阴离子表面活性剂的吸附

在无乳化剂的条件下合成了粒径均匀的聚苯乙烯胶乳, 发展了应用表面张力计测定吸附等温线的连续平衡法, 得到不同盐浓度下聚苯乙烯胶乳对十二烷基硫酸钠和十二烷基苯磺酸钠的吸附等温线, 它们属于Giles分类的L2 型或L1 型, 采有两阶段吸附模式讨论了吸附机理, 吸附层结构及等温线类型变化的规律。     

Temperature effect on the viscoelastic properties of solutions of cylindrical mixed micelles of zwitterionic and anionic surfactants

The viscoelastic properties of semidilute mixed aqueous solutions of oleyl amidopropylbetaine and sodium dodecylbenzene sulfonate are studied in the temperature range of 20–40°C. It is shown that, at 20°C, the solution viscosity can be as high as 390 (Pa s), which is related to the formation of a network of entanglements of long cylindrical micelles of surfactants. It is revealed that, upon heating, the viscosity and relaxation time of the system decrease, while the contour length of cylindrical micelles decreases consider-ably. It is shown that this susceptibility of viscoelastic surfactant solutions to temperature is due to the low energy of break, which is much lower than the energy of covalent bonds.