Anionic Surfactants In Aqueous Solutions Research Articles

Soluting effect of amino acids on 1‑decyl‑3‑methylimidazolium bromide and 1‑dodecyl‑3‑methylimidazolium bromide as cationic surfactants and sodium dodecyl sulfate as anionic surfactant in aqueous solutions

In this work, with the aim of shedding light on the effect of zwitterion cosolutes (amino acids) on the aggregation and surface behaviors of both cationic and anionic surfactants in aqueous solution, surface and micellar behavior of 1‑decyl‑3‑methyl imidazolium bromide ([C10mim]Br), 1‑dodecyl‑3‑methyl imidazolium bromide ([C12mim]Br) and sodium dodecyl sulfate (SDS) in aqueous solutions of 0.7 mol·kg−1 glycine, alanine and proline were studied by means of volumetric, compression, electric conductivity and surface tension measurements at different temperatures. From the experimental density and speed of sound data, the various parameters such as apparent molar volume, isentropic compression, apparent molar isentropic compression and the change of apparent molar volume upon micellization as well as upon transfer from pure water to aqueous amino acid solutions were derived. Our results showed that the order of isentropic compression for the investigated surfactants in presence of the amino acids was: SDS > [C12mim]Br ≫ [C10mim]Br. Also the obtained negative values for transfer apparent molar volume from pure water to aqueous amino acid solutions in ternary systems of ([C10mim]Br + water + proline) and ([C12mim]Br/SDS + water + glycine/alanine/proline) indicated that hydrophobic-hydrophobic interactions are predominant. The values of the degree of ionization of the counter ion on the micelles and thermodynamic properties of micellization for the investigated surfactants in aqueous amino acids solutions were obtained from the electrical conductivity measurements. It was found that, hydrophobic-hydrophobic interactions between the aliphatic chain of surfactants and amino acids have unfavorable effects on micelle formation. From the surface tension measurements, a series of parameters, including adsorption efficiency, surface tension at CMC, surface tension at micellar phase (γmic), effectiveness for surface tension reduction, maximum surface excess concentration and minimum surface area per molecule were determined for the investigated surfactants in the presence of different amino acids at 298.15 K.All the investigated amino acids have soluting-out effect and their abilities to reduce the CMC of the surfactants in aqueous solutions decrease with an increase in the hydrophobicity of the amino acid. Resultant data showed that the ability of the amino acids to decrease the CMC followed the order: glycine > alanine ≫ proline.

Removal efficiency of anionic surfactants from water during UVC photolysis and advanced oxidation process in H2O2/UVC system

AbstractSurfactants after their use are discharged into aquatic ecosystems. These compounds may be harmful to fauna and flora in surface waters or can be toxic for microorganisms of the activated sludge or biofilm in WWTP. In order to determine effectiveness of different advanced oxidation processes on the degradation of surfactants, in this study the degradation of anionic surfactants in aqueous solution using photolysis by 254 nm irradiation and by advanced oxidation process in a H2O2/UVC system was investigated. Two representatives of anionic surfactants, linear alkyl benzene sulphonate (LAS-R11–14) and ether carboxylic derivate (EC-R12–14E10) were tested. The influence of pH, initial surfactant concentration and dose of hydrogen peroxide on the degradation was also studied. Results show outstanding effectiveness of the H2O2/UVC system in the removal of surfactant from aqueous solutions.

Planar electrodes based on carbon nanotubes for the potentiometric determination of homologous sodium alkyl sulfates

Planar electrodes based on carbon nanotubes, manufactured by screen printing, are proposed for the determination of anionic surfactants in aqueous solutions. A comparative analysis of the electroanalytical characteristics of planar and solid-state sensors based on various ionophores, namely, ion associates of (1) sodium dodecyl sulfate with a cationic complexes of copper(II) and N,N′-bis(salicylidene)ethylenediamine and (2) sodium dodecyl sulfate with cetylpyridinium, is performed. It is shown that planar electrodes can be used to quantify homologous sodium alkyl sulfates in the concentrations range of 4 × 10−7 (5 × 10−6) to 1 × 10−2 (5 × 10−4) M at pH 4–10 in water bodies and to determine the total concentration of anionic surfactants in detergents.

Determination of anionic surfactants using methods of impedance spectroscopy and chemometrics

A procedure is developed for the determination of anionic surfactants (ASs) in water-oil emulsions by impedance spectroscopy with the chemometric processing of experimental data. The conditions of recording impedance titration curves were optimized and the performance characteristics of the procedure were estimated. It was shown that impedance spectroscopic titration is applicable to the determination of AS in aqueous solutions and water-oil emulsions in the presence of organic and inorganic substances. Examples of determination of ASs based on sodium olefin sulfonate are given.

Influence of Cationic Surfactants on the Formation and Surface Oxidation States of Gold Nanoparticles Produced via Laser Ablation

We report on the time evolution of gold nanoparticles produced by laser ablation in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) in aqueous solution. The broader applicability of a laser-induced nanoparticle formation kinetic model previously developed by us for the case of anionic surfactants in aqueous solution [ J. Phys. Chem. C 2010 , 114 , 15931 - 15940 ] is shown to also apply in the presence of cationic surfactants. We explore the surface properties of the nanoparticles produced in the presence of the cationic surfactants via synchrotron X-ray photoelectron spectroscopy (XPS). The XPS data indicate that at CTA(+) concentrations approximating the aqueous critical micelle concentration Au(III) is present on the nanoparticle surface. Such oxidation is not observed at (i) lower CTA(+) concentrations, (ii) in the presence of an anionic surfactant, or (iii) in the case of pure water as a solvent.

Synergistic Effects of Lignin-Phenol-based Nonionic Surfactant with Anionic Surfactants in Aqueous Solution

Surfactants made from modified lignin are attracting growing attention; therefore, a lignin-phenol nonionic surfactant named ML-AL has been prepared by modifying liquefied industrial alkali lignin (L-AL). Its basic physical and chemical properties have been shown to be favorable. In this work, anionic surfactants of sodium fatty acid soap (carbon numbers 12, 16, and 18) and sulfur-containing anionic surfactants (sodium dodecyl sulfate and sodium dodecyl benzene sulfonate) were chosen to mix with ML-AL in water-soluble media. The surface properties of each binary mixed solution system with anionic surfactant were investigated. At the same time, the mixed micelles formed by ML-AL and each anionic surfactant were studied. Non-ideal mixed micelles were obtained via ML-AL and the tested anionic surfactant. The interaction parameter (βM) and excess free energy (ΔGexcess) were both negative. Meanwhile, the critical micelle concentration (CMC) values of mixed systems (formed by ML-AL and each anionic surfactant in aqueous solution) were lower than those of a single-component system (ML-AL or single anionic surfactant). There was an optimum dosage ratio of about 0.4 in terms of synergistic effects. This research could provide a foundation for practical applications of combinations with anionic surfactants in aqueous solution.

Adsorption of CnTABr surfactants on activated carbons

Cationic surfactants of the quaternary ammonium bromide type C16TABr, C14TABr, C12TABr, and C10TABr were adsorbed from aqueous solutions onto three different types of activated carbons and compared with the adsorption of the anionic surfactant sodium dodecyl benzene sulfonate. The concentrations of both cationic and anionic surfactants in aqueous solutions were determined by UV spectroscopy. In the case of anionic surfactants, a linear dependence of UV absorbance on the surfactant concentration at 200nm can be related to the benzene fragment of the molecule. The UV sensitivity of CnTABr solutions is controlled by the hydration of bromide counterions, the electron dense nature of bromine, and a charge-transfer-to-solvent phenomenon. Changes in the textural properties of the activated carbons after adsorption of surfactants were studied by N2 adsorption and mercury intrusion porosimetry, and could be correlated to surface characteristics and adsorptive capacity. The mechanism of adsorption was found to be complex, but the porous structure of the carbon exerted a critical role and the cationic surfactants were adsorbed step-by-step. At low surfactant concentrations, adsorption occurred in micropores. We conclude that surfactants are adsorbed as individual molecules. Adsorption from more concentrated solutions occurs in meso- and macropores, and resembles surfactant adsorption on flat carbon surfaces. The carbons display somewhat different tendencies to adsorb CnTABr. Activated carbons with small pores of 0.56-0.77nm appear to be most effective for surfactant removal. A negative electrostatic potential on the interface of the carbons appears to enhance the adsorption of cationic surfactants, as would be expected. Controlling the electrostatic potential and pore size distribution of the activated carbons would be beneficial in the application of activated carbons for removal of surfactants from wastewater.

Long-chain anionic surfactants in aqueous solution. Removal by Moringa oleifera coagulant

Moringa oleifera seed extract was confirmed as a feasible coagulant in removing surfactants from aqueous effluents. Amongst them, long-chain anionic detergents such as Polyoxyethylene (3.5) sodium lauryl ether sulfate (SLES) was selected as a model compound for evaluating the coagulation response. The system coagulant–detergent was stable with different temperatures and pH, and the efficiency was very promising. M. oleifera was an effective coagulant since it was capable to reach up to 0.245 mg mg −1 coagulation capacity according to Gu–Zhu model. Design of experiments presented an optimum combination of coagulant dosage and initial surfactant concentration of 234 mg L −1 and 76 mg L −1, respectively.

Mesoporous alumina (I): Comparison of synthesis schemes using anionic, cationic, and non-ionic surfactants

A series of mesoporous alumina was prepared using a selected group of anionic, non-ionic, and cationic surfactants with Al-tri- sec-butoxide or Al 3+ in organic solvent with stoichiometric amount of water, and in aqueous solution with different hydrolyzing agents, or with complexing agent at room temperature to 100 °C. A comparison of the physicochemical properties of the materials prepared was made with respect to surface area, thermal stability, and porosity. Anionic surfactants in aqueous solution produced thermally unstable materials but in organic solvent resulted in a moderately stable alumina phase. Both cationic and non-ionic surfactants produced thermally stable mesoporous alumina after removal of the surfactant upon calcination at 500 °C when the materials were synthesized in organic solvents. Overall, mesoporous alumina prepared with cationic cetyltrimethylammonium bromide in sec-butanol in the optimized substrate composition of Al:surfactant:H 2O:solvent = 1.0:0.3:2.0:15 exhibited the best textural property among the various synthesis systems investigated.

Threadlike Micelle Formation of Anionic Surfactants in Aqueous Solution

We have investigated the formation of threadlike micelles consisting of anionic surfactants and certain additives in aqueous solution. Threadlike micelles long enough to be entangled with each other were formed in a clear aqueous solution of two anionic surfactants, sodium hexadecyl sulfate and sodium tetradecyl sulfate. These solutions also contained pentylammonium bromides or p-toluidine halides and exhibited remarkable viscoelasticity. Because the molar ratio of surfactants to cationic additives in these micelles seemed close to unity, they formed 1:1 stoichiometric complexes between surfactant anions and additive cations, as previously found in systems of cationic surfactants such as hexadecyltrimethylammonium bromide and sodium salicylate. The viscoelastic behavior of these anionic threadlike micellar systems was adequately described by a simple Maxwell element with a single relaxation time and strength, as in many similar cationic systems.

Acid-Induced Phase Separation of Anionic Surfactants for the Extraction of 1,4-Dichlorobenzene from Honey Prior to Liquid Chromatography

The acid-induced liquid-liquid phase separation of anionic surfactants in aqueous solutions and its applicability to cloud point extraction methodology were applied as a tool for the extraction of 1,4-dichlorobenzene (p-DCB) from aqueous samples. p-DCB is extracted into the micelles of sodium dodecane sulfonate (SDSA) in a 4.2 M HCl solution. The micellar phase is separated from the bulk aqueous solution after centrifugation and collected from the surface of the suspension. The micellar extracts are injected into a high-performance liquid chromatographic apparatus and quantified at 225 nm with a reference wavelength of 280 nm. Following the proposed methodology, a preconcentration factor of ca. 160 is achieved (starting from 50 mL solutions) allowing for detection limits at the low microg/L level. Application to honey samples produced detection limits of 2.5 microg/kg with quantification limits of 7.5 microg/kg, while the recoveries of the method ranged from 85% at high concentrations to 95% at lower concentrations of p-DCB. The combined uncertainty of the entire analytical procedure was 4.5% at the concentration level of 30 microg/kg allowing for reliable and reproducible results for the determination of p-DCB at the concentration levels considered as thresholds for EU and U.S. legislation (10 microg/kg).

Thermodynamics of Aqueous Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide)/Surfactant Mixtures. Effect of the Copolymer Molecular Weight and the Surfactant Alkyl Chain Length

A calorimetric study was performed to focus attention on the interactions between copolymers and anionic surfactants in aqueous solutions. Three aspects were analyzed: (1) the hydrophobicity of the surfactant, (2) the change of the copolymer molecular weight, and (3) the nature of the hydrophilicity of the copolymer. To this purpose, the family of sodium alkanoates (sodium octanoate through sodium dodecanoate) and the tri-block copolymers EO76PO29EO76 (F68), EO103PO39EO103 and EO132PO50EO132 were investigated. Comparing F68 and EO13PO30EO13 (L64), previously studied by us, provided information on the effect of the copolymer hydrophilicity. The experimental data were analyzed by means of a thermodynamic model which assumes that in the surfactant dilute region monomers of surfactant interact with unimeric copolymer leading to the formation of surfactant-copolymer aggregation complexes; when micelles do form, they can solubilize the copolymer, and then, the copolymer−micelle aggregates formation takes place. Data modeling provided useful parameters which allowed us to discriminate the various effects contributing to the formation of such aggregates. The thermodynamic properties for the formation of both the surfactant−copolymer aggregation complexes and copolymer−micelle aggregates were not consistent with the expectation; despite the more hydrophilic sites available in F68, the enthalpy and entropy for F68 were larger and the free energy more negative than those of L64. Moreover, the role of the copolymer molecular weight was important although the ratio between the number of the hydrophilic and the hydrophobic sites of binding is constant. An effort was done to verify whether these findings are representative of the physical interactions between copolymer and surfactant or reflect the large difference in the molecular masses. Therefore, the thermodynamic properties were normalized for the number of EO and PO units. They straightforwardly showed that L64 has a larger hydrophobic character than F68 and the copolymer molecular weight plays a small role.

Metal ion determination by flame atomic absorption spectrometry through reagentless coacervate phase separation-extraction into lamellar vesicles.

The phase separation of lamellar vesicles of anionic surfactants in aqueous solutions and its application as a novel liquid coacervate extraction procedure was examined. Solutions of lauric acid sodium salt separate into two phases in the presence of alkaline earth metals and a water miscible cosurfactant. It is proven that the surfactant phase is built of a perplexed network of multilamellar vesicles consisting of densely packed bilayers. Several factors affecting the formation of this new phase as well as its analytical utility in the preconcentration of metallic ions were assessed on the basis of better exploitation of this new nonspecific extraction technique. In essence, although the procedure to arrive at the optimum conditions seems laborious, the delivered method is straightforward, alleviating the requirement for prereaction with a complexing agent and highly reproducible under the optimum experimental conditions. As an analytical demonstration, the method was successfully applied to the determination of Cd(2+) and Zn(2+) in natural waters. Recoveries were higher than 95%, and detection limits as low as 3 microg L(-)(1) were accomplished by preconcentrating only 10 mL of sample volume in the presence of 0.45% (w/v) anionic surfactant.

Effectiveness of Surface Tension Reduction by Anionic Surfactants—Quantitative Structure–Property Relationships

A quantitative structure–property relationship (QSPR) has been found to predict the effectiveness of surface tension reduction by anionic surfactants in aqueous solution, as measured by the maximum surface pressure at their respective critical micelle concentrations Πcmc. Our data set contains 34 values of surface pressure for 20 anionic surfactants at different counterion concentration C at different temperatures T. Besides C and T, the best‐regressed model also contains three molecular structural descriptors of surfactants: the Kier & Hall index of zero order, KH0, of the hydrophobic fragment, the molar heat of formation ΔH f and the molecular dipole moment D. The best QSPR between Πcmc and the descriptors produces a correlation coefficient (of multiple determination) of 0.988.

Comicellization of Polystyrene-block-Poly(ethylene oxide) with Cationic and Anionic Surfactants in Aqueous Solutions: Indications and Limits

Interaction of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) with cationic and anionic surfactants was studied using light scattering, sedimentation in ultracentrifuge, and 1H NMR. The complex structure of the mixed solution containing hybrid micelles, micellar clusters, and supermicellar aggregates was confirmed by independent experiments. By proton NMR, addition of anionic surfactant, sodium dodecyl sulfate (SDS), to PS-b-PEO solution results in loosening the micelle cores and an increase of the PS molecular mobility in the presence of surfactant. At the same time, incorporation of SDS into the block copolymer solution leads to noticeable broadening of the signals related to methylene protons of the surfactant, which can be assigned to a decrease of mobility of surfactant alkyl chains “immobilized” on the PS cores. These data along with ultracentrifugation of hybrid solutions containing PS-b-PEO and surfactant at various concentrations prove that comicellization occurs and mixed micelles are formed. However, this phenomenon is observed up to a certain limiting concentration of the surfactant. In the case of cetyl pyridinium chloride (CPC), increase of surfactant loading up to 0.05 mol/L results in the solutions containing CPC micelles along with hybrid micellar clusters and supermicellar aggregates.

Optimization of the methylene blue assay for anionic surfactants added to estuarine and marine water.

The existing rapid method for the determination of anionic surfactants in aqueous solutions relies on the association of the cationic methylene blue dye with the anionic surfactant to form an electroneutral complex that is subsequently extracted into chloroform and determined spectrophotometrically. This methylene blue active substance (MBAS) assay suffers from salt interference in estuarine and marine waters due to the high concentration of chloride (Cl-) ions. The interference was shown to arise from the association of Cl- ions with the cationic methylene blue dye, which, although weak, becomes significant at the elevated concentrations of Cl- in marine water. Analysis of the kinetics of the formation and extraction into chloroform of complexes of methylene blue with a typical anionic surfactant (sodium dodecyl sulfate, SDS) and with Cl- ions revealed that the efficacy of the extraction step was critical in yielding reliable data. Based on these results, a modified, simple one-step MBAS method is described that overcomes interference by salt.

An Acid-Induced Phase Cloud Point Separation Approach Using Anionic Surfactants for the Extraction and Preconcentration of Organic Compounds

The acid-induced liquid−liquid phase separation of anionic surfactants in aqueous solutions, and its applicability to cloud point extraction methodology, were examined. The phase diagrams obtained (e.g., [HCl] vs [surfactant]) consisted of three regions: a homogeneous liquid region, two coexisting isotropic phases, and a solid region. The breadth of each region was found to depend on the surfactant structure. The behavior of each phase was also examined in relation to temperature and added salts. The anionic surfactants investigated were sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonic acid (SDBSA), sodium dodecanesulfonic acid (SDSA), and sodium dioctylsulfosuccinate (Aerosol OT). The use of anionic surfactant-mediated phase separations provided very high extraction efficiencies (80−100%) for pyrene in aqueous samples and various PAHs in a certified reference material (dried sewage sludge). The preconcentration factor achieved was found to be a function of both surfactant and acid concentrati...

Preparation of Organic Particles by Complexation between Cationic and Anionic Surfactants in Aqueous Solution

The complexation between cationic and anionic surfactant was monitored by changing molecular ratio between cationic and anionic surfactant molecule and alkyl chain length of anionic surfactant. The precipitation was identified with elemental analysis, SEM and UV-vis spectrophotometer. The relative degree of precipitation was determined by weighing the amount of precipitation and the size of the precipitation was determined with light scattering. This study enabled the preparation of organic charge transfer complex by ionic surfactants.

Spectrophotometric determination of anionic surfactants in aqueous and environmental water samples with cationic dyes

The applicatiliby of the extractive spectrophotometric method using three different cationic dyes as the chromogenic reagent for indentification and quantification of anionic surfactants in aqueous solutions and environmental samples was comparatively investigated. The inteferences due to the ions Cl−, NO3 −, Ca++, Mg++ and Fe3+ were examined as well as the effect of pH. The recoveries ranged from 95 to 104% for sea water samples.

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.