Bulk and interfacial physical properties of aqueous solutions of sodium lauryl sulphate and lauryl alcohol with air and benzene systems: Part II — mixed aqueous solutions of sodium lauryl sulphate and lauryl alcohol

The pH, density, bulk viscosity and electrical conductivity of aqueous solutions of mixtures of sodium lauryl sulphate and lauryl alcohol were measured for a range of concentrations at 25°C. The influence of interface age on the interfacial tension of mutually saturated benzene/aqueous solution surfaces is also reported. The effect of impurities on various physical properties was illustrated using an impure lauryl sulphate system. A detailed comparison of these data with those reported in the literature shows satisfactory agreement above the critical micelle concentration of the sodium lauryl sulphate in water. Current data in the premicellar concentration range reveal anomalous behavior. Data reported in the literature are summarized for the pH, density, bulk viscosity, electrical conductivity, surface tension, interfacial tension with benzene, surface excess concentration, surface shear viscosity, critical micelle concentration and molecular complex formation of the sodium lauryl sulphate/lauryl alcohol aqueous solutions. The interactions of the anionic-nonionic surfactants at fluid/fluid surfaces and their influence on the physical properties are examined. The use of such systems in the stabilization of dispersions is also discussed. Eighty-five references are cited.     

Bulk and interfacial physical properties of aqueous solutions of sodium lauryl sulphate and lauryl alcohol. Part III: The effect of impurities and additives on pH and electrical conductance of premicellar and micellar solutions of sodium lauryl sulphate

Experimental measurements of the pH, electrical conductance and Kraft temperatures were made for a number of commercially available and purified samples of sodium lauryl sulphate for a wide range of surfactant concentrations in aqueous solutiin at 25°C. The efect of lauryl alcohol and sodium chloride on the pH and electrical conductance was also studied. The effects of type of electrodes, sequence of measurements, the memory effect, mixing and carbon dioxide were explored for the pH measurements. The results show that pH is a convenient and reliable method for the determination of critical micelle concentration (CMC) of ionic surfactants. The pH versus concentration data can also be used to uniquely identify the presence of contaminants or species other than pure sodium lauryl sulphate in that discontinuities occur in the data at unique concentrations so that identification of the contaminant is easy. High concentration discontinuities are identified and are attributed to individual or mixture CMC values. Anomalies in the data occur for concentrations less than 0.05 wt.% and especially around 0.01 to 0.02 wt.% for pure sodium lauryl sulphate solutions. Data are also given that show the effects of aging. Data reported in the literature for the pH, electrical conductance and Kraft temperature are compared.     

Bulk and interfacial physical properties of aqueous solutions of sodium lauryl sulphate: Part IV: Dilute aqueous solution behavior by electron spin resonance studies and by pH and surface tension measurements

The electron spin resonance spectrum of the nitroxide label 2,2,6,6 – TetraMethyl – 4 – Piperidone – Oxide (TEMPO) has been investigated in aqueous solutions of a purified and commercially available impure samples of sodium lauryl sulphate (NaLS) for a wide range of concentrations. The spectra were recorded at 24°C as a function of surfactant concentration. The reorientational correlation times T_θ of the TEMPO label in aqueous solutions were calculated using the Kivelson's theory. Using the T_θ data qualitative analysis has been carried out in an attempt to understand the microscopic effects produced by the hydrophobic part of the surfactant on the water structure and the hydrophobic-hydrophobic interactions in water. Four major discontinuities in the τ_θ results have been identified with the purified NaLS system. They are found to occur at NaLS concentrations of 0.008 wt.%, 0.015 wt.%, 0.23 and 1.73 wt.%. The latter two concentrations represent the first and the second critical micelle concentration (CMC) of the surfactant while the first two concentrations reveal the existence of premicellar association and dissociation processes, respectively. These discontinuities have been also confirmed by the pH data and by surface tension results from the du Noüy ring method. The effect of addition of lauryl alcohol and sodium chloride on τ_θ values was also studied. The additive action has been found to produce an additional discontinuity, corresponding to the mixture CMC, in the τ_θ versus concentration plot. Analysis of other effects such as solution aging and hydrolysis of NaLS are also included. The applicability of the spin labelling technique for the study of aqueous solution behavior of NaLS is discussed by comparing data reported in the literature.     

异构脂肪醇聚氧乙烯醚硫酸钠的合成和性能

以异构脂肪醇聚氧乙烯醚为原料,合成了不同碳链长度的异构脂肪醇聚氧乙烯醚硫酸钠;测定了产品的表面化学性能,并与直链脂肪醇聚氧乙烯醚硫酸钠产品进行比较。结果显示,异构脂肪醇聚氧乙烯醚硫酸钠降低溶液表面张力的能力略强于直链产品,同时异构产品的去污力、润湿性能都有显著提高,但是它降低了产品的泡沫性和乳化性。异构产品胶束内核的微极性在无机盐环境中大于直链产品,说明其形成的胶束结构比较松散。     

Zinc electrowinning from acidic sulfate solutions: Part I: Effects of sodium lauryl sulfate

The effects of sodium lauryl sulphate(SLS) in the presence and absence of antimony(iii) on the current efficiency, power consumption and polarization behaviour of zinc were determined. The surface morphologies and deposit crystallographic orientations were also evaluated. The results were compared with glue as the addition agent. The addition of sodium lauryl sulfate to the zinc sulfate solution increased current efficiency, reduced power consumption and improved the surface morphology. Maximum current efficiency and minimum power consumption were achieved on addition of 0.02mgdm–3 Sb with 1mgdm–3 sodium lauryl sulfate.     

Electro-oxidation of sodium lauryl sulfate aqueous solutions

The electro-oxidation of dilute aqueous solutions of sodium lauryl sulfate (LS) was studied in the presence of metal ions and sulfuric acid, in order to achieve the complete destruction of the detergent. An undivided cell and rhodiated titanium electrodes were used. The LS concentration was studied as a function of time, added metal ion, pH, temperature, initial current density and detergent concentration. The results obtained showed that 99% LS destruction can be easily achieved and that complete oxidation occurs. LS depletion rate was found to increase with temperature, current density (up to 2 A dm^–2) and detergent concentration but to decrease with pH. The best results were obtained with iron ions dissolved in the electrolyte, but the process rate was nearly independent of Fe concentration above 0.5 mM.     

Natural dye–surfactant interactions: thermodynamic and surface parameters

The interaction of two Indian natural dyes, namely madder (Rubia cordifolia) and mallow (Punica granatum), with cationic surfactant cetyl trimethyl ammonium bromide and anionic surfactant sodium lauryl sulphate, has been studied. Spectrophotometric data showed a strong interaction between the natural dyes and the surfactants. The critical micelle concentration of the surfactants, determined by measurement of specific conductance and surface tension, was found to decrease on the addition of natural dyes in an aqueous solution of surfactants. The thermodynamic and surface parameters for the interaction have been evaluated.     

Dilational viscoelastic properties of fluid interfaces—III Mixed surfactant systems

The surface viscosity and elasticity of solutions of mixed surfactants were determined using the longitudinal wave technique combined with tracer particle measurements. The recent analysis of Maru et al., which was restricted to insoluble monolayers and to monolayers adsorbed from a single surfactant solution, has now been extended to multicomponent solutions. This analysis can be used not only to estimate the “net” viscoelastic properties at gas-liquid interfaces but also to estimate the composition as well as the intrinsic viscoelastic properties. Furthermore, when accompanied by separate measurements of shear viscoelastic properties, the above analysis can be used for the determination of dilational viscosity and elasticity.Surface viscoelasticity measurements were conducted on aqueous solutions of sodium lauryl sulfate and sodium lauryl sulfate-lauryl alcohol. Net surface viscosity and elasticity of sodium lauryl sulfate solutions increased with bulk concentration and reached a maximum at a concentration in the neighborhood of the critical micelle concentration. The presence of small amount of lauryl alcohol caused almost an order of magnitude increase in intrinsic surface viscosity and a similar increase in compositional surface elasticity. A comparison between the values of intrinsic surface viscosity and those of surface shear viscosity indicated that surface dilational viscosity exceeds surface shear viscosity by at least two orders of magnitude. These appear to be the first set of data presented hitherto for the surface dilational properties in addition to surface shear properties for the same mixed surfactant systems.     

Effects of pH and Surfactant Precipitation on Surface Tension and CMC Determination of Aqueous Sodium n-Alkyl Carboxylate Solutions

Aqueous solutions of sodium tetradecanoate (S14C) and sodium dodecanoate (S12C) were used to evaluate complicated precipitation phenomena and to monitor the effects of bulk pH adjustments on surface tension and critical micelle concentrations (CMC) determination from surface tension plots. Limited solubilities of pure sodium n-alkyl carboxylates in solution near the CMC have been reported previously many times. In this study, precipitation encountered with solutions prepared from vender-supplied S12C was eliminated through additional purification. As sodium alkyl carboxylates discussed in the literature are commonly used as received from the manufacture without additional purification, the wide range of reported CMC values as well as precipitation near the CMC for S12C are also likely due to impurities. However, complete solubility for S14C solution concentrations near the reported CMC values was not obtained through additional purification of purchased material. Hence, some CMC values reported in the literature for S14C should be reconsidered, as discontinuities in the slope of surface tension versus concentration plots are likely caused by the formation of a precipitate not micelle aggregation. In addition and in agreement with other studies, solution pH adjustments revealed a minimum surface tension for maximum solubility near the pK _a value for S14C.     

两性/阴离子表面活性剂复配体系性能研究

采用环氧氯丙烷与磷酸二氢钠反应制备中间体,再与十二叔胺反应,制备甜菜碱型磷酸酯两性表面活性剂,并与十二烷基苯磺酸钠(SDBS)进行复配。测定复配前后产品的表面张力、临界胶束浓度、泡沫稳定性和乳化能力等性能。结果表明,在最佳合成工艺条件下,甜菜碱型磷酸酯两性表面活性剂的表面张力为30 mN/m,临界胶束浓度为7.98 g/L。对于复配体系,当甜菜碱型磷酸酯表面活性剂与SDBS以质量比6∶4进行复配时增效作用最好,其表面张力为23 mN/m,临界胶束浓度为4.84 g/L,对松节油的乳化性能较好。     

十二烷基三甲基氢氧化铵与十二烷基苯磺酸钠复配体系的表面活性

考察了十二烷基三甲基氢氧化铵(DTAH)和十二烷基苯磺酸钠(SDBS)及其混合体系的表面活性、碱性和稳定性。结果表明,复配体系n(DTAH)∶n(SDBS)=9∶1时,不仅降低表面张力能力和效率均有显著提高,而且具有很好的稳定性和强碱性,其CMC(临界胶束浓度)、γCMC(临界胶束浓度时的表面张力)和pH分别为3.02×10-5mol/L,28.10 mN/m和12.46,DTAH/SDBS复配体系在表面和胶束中的相互作用参数βσ和βm分别为-18.36,-22.69,表现出很好的协同作用。     

Influence of nonionic surfactant additive on the properties of ionic surfactant solutions

The interaction of sodium dodecyl sulfate with a nonionic surfactant (a block copolymer of ethylene oxide and propylene oxide) has been investigated by the measurement of conductivity, surface tension and viscosity. The break point on the equivalent conductivity-square root of concentration diagram which gives the critical micelle concentration (cmc) of sodium dodecyl sulfate became less definite by the addition of the nonionic surfactant, because of the decrease in conductivity below the cmc and increase above the cmc. The steep decrease in reduced viscosity took place in dilute concentration of sodium dodecyl sulfate solutions. In the surface tension vs. concentration diagram, the concentration at which the two linear portions of the curve intersect represents the cmc. The addition of nonionic surfactant decreases this crossed point of sodium dodecyl sulfate and finally obscures the crossed point. These reults are interpreted in terms of an interaction between sodium dodecyl sulfate and nonionic surfactant.     

Adsorption of sodium dodecyl sulphate on cassiterite surface

Measurements of the adsorption of sodium dodecyl sulphate (SDS) onto cassiterite were made. It was found that at SDS concentrations below 10 ^?3 mol/L the adsorption depended on the manner of preparation of the cassiterite and the pH of solution. However, the adsorption isotherms showed a point of inflection at l0 ^?3 mol/L corresponding to an occupied area per molecule of about 0.8 nm². This value is close to the surface area covered by one dodecyl sulphate ion (DS ^?) as evaluated from the molecular structure of SDS. Near the critical micelle concentration (cmc), a plateau was found which corresponded to the adsorption of two statistical monolayers of DS ^? ions vertically oriented to the surface.     

Mixed Micellization of Sodium Dodecylbenzene Sulfonate with Polyoxyethylene Lauryl Ether Surfactants (POLE4 and POLE23) in n-Butanol Aqueous Solution

The values of critical micelle concentration and counterion binding constant for the mixed micellizations of sodium dodecylbenzenesulfonate (DBS) with polyoxyethylene(4) lauryl ether (POLE4) and polyoxyethylene(23) lauryl ether (POLE23) in aqueous solution of n-butanol at 25 °C were determined as a function of the overall mole fraction of DBS by using the electric conductivity and the surface tension methods. Various thermodynamic parameters were calculated and analyzed for the mixed micellization of DBS/POLE4 and DBS/POLE23 systems by means of the equations derived from the nonideal mixed micellar model. The results show that DBS/POLE23 mixed system has a greater deviation from the ideal model than DBS/POLE4 mixed system. These deviations of thermodynamic parameters for both mixed systems become greater with the addition and concentration increase of n-butanol.     

高斯多峰拟合用于混合表面活性剂十二烷基硫酸钠和吐温80临界胶束浓度的测量

报道了可见吸收光谱线型的高斯多峰拟合用于混合表面活性剂十二烷基硫酸钠(SDS)和吐温80临界胶束浓度的测定.具体的做法是以碱性品红(Fuchsin)为探针,测量固定浓度的吐温80对一系列浓度的SDS-碱性品红水溶液体系的可见吸收光谱.其光谱特征是碱性品红二聚体吸收峰和单体吸收峰叠合在一起.用高斯多峰拟合实现了体系可见光...     

Polymer polarity and surfactant adsorption

The effect of polymer polarity on surfactant adsorption from aqueous solution is discussed. The analysis assumes that surfactant adsorption at the polymer–water interface follows a Langmuir-type adsorption isotherm and the free energy of adsorption is controlled by the interfacial tension of the interface. Saturation adsorption given by the area per molecule of surfactant at the critical micelle concentration (CMC) of the surfactant is related to the polymer–water interfacial tension and the polarity of the polymer surface, calculated from the polar and dispersion contributions to the polymer surface energy. Available data on the area per molecule of sodium lauryl sulfate on various polymer surfaces have been used to test satisfactorily the above analysis. The analysis is used to interpret some of the observations relating to surfactant adsorption encountered in the emulsion polymerization of polar monomers and particle size determination of latexes by the soap titration method. Further, potential utility of such area per molecule data to characterize the nature of polymer surfaces is also discussed.     

Effect of pH on the critical micelle concentration of sodium dodecyl sulphate

Critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS) at various pH's between 2 and 10 has been studied using three methods as dye absorption, conductance, and light scattering measurement. At low pH (below pH 4) the CMC decreases whereas at higher pH it remains constant.     

月桂胺二甲磺酸钠两性表面活性剂的合成与性能表征

采用月桂胺、甲醛和无机磺化剂(NaHSO3或Na2SO3)为原料,先经两步反应合成出酸式产物,再经固相成盐反应制得月桂胺二甲磺酸钠(LADSS)两性表面活性剂,产率达86.7%,并用红外光谱(IR)对其结构进行了表征,计算了其亲水亲油平衡值(HLB)。同时,对目标产物水溶液的pH值和表面性能(表面张力、临界胶束浓度、增溶能力、中和曲线和耐硬水能力)进行了测定,结果表明LADSS是一种性能优越的表面活性剂。     

Absorption of oxygen by aqueous sodium sulphite solutions

New data have been reported on the absorption of oxygen by aqueous sodium sulphite solutions with cobalt sulphate as catalyst at 30°C. It is observed that the absorption rate increases up to a critical sulphite concentration beyond which the absorption rate becomes constant and this critical concentration varies with the catalyst concentration. The order of reaction with respect to sulphite and oxygen in the constant absorption rate regime was found to be zero and two respectively. The absorption rate is affected by the total ionic strength (sulphite and sulphate) in addition to the effect of pH and catalyst concentraion. The reported data were also analysed to ascertain the effect of temperature and a relationship has been proposed for prediction of the second order reaction rate constant.     

Electrodeposition of iron in sulphate solutions

The kinetics of iron electrodeposition from acid sulphate solutions onto a platinum electrode was investigated by means of stationary polarisation curves and electrochemical impedance spectroscopy. Together with interfacial pH data previously obtained, the effect of pH was analysed. The formation of at least three adsorbed intermediates at the cathode surface was evidenced in all pH values. The relative rate of their formation and its surface concentration depend on the solution pH as well as on the electrode potential. It is suggested that two of these species catalyses the H⁺ reduction whereas the other one may have a blocking effect on this reaction.