Three-phase behavior in a mixed nonionic surfactant system

The effect of monodisperse solubilities of each surfactant in an excess oil phase on the three-phase behavior was investigated in a water/octaethyleneglycol dodecyl ether (R₁₂EO₈)/tetraethyleneglycol dodecyl ether (R₁₂EO₄)/heptane system. The mid temperature of the three-phase region is defined as the HLB temperature. The HLB temperature is largely skewed to higher temperature in a dilute region due to the difference in the distribution of each surfactant between excess oil and microemulsion (surfactant) phases forming the three-phase body. Taking account of the monodisperse solubilities, the equation for the HLB temperature was obtained on the basis of geometrical calculation of a particular three-phase triangle. The equation well describes the three-phase behavior for a mixed surfactant system in a space of compositions and temperature.In the mixed surfactant system, the monodisperse solubility of R₁₂EO₈ in oil phase forming a three-phase body is monotonously increased with the rise in temperature, whereas that of R₁₂EO₄ is first increased and then is decreased. Consequently, the sum of both solubilities does not change greatly in a wide range of temperature.     

Compositional Analysis and Adsorption Performance of Surfactants Used for Combined Chemical Flooding

Adsorption of surfactants on reservoir sands in a combined chemical flooding process was investigated using a microcosmic method in order to reveal the effects of surfactant composition on their adsorption. Alkylbenzenesulfonate types of surfactant have been used in this study. The experimental results indicate that surfactant adsorption on the sands heavily depends on its lipophilicity, and the adsorption quantity increases with increasing the lipophilic chain length of the surfactant. It was found that the saturated adsorption could be reached when the concentration of the surfactant was near the critical micelle concentration (CMC). For oilfield applications, the molecular ion peak of the alkylbenzene‐sulfonate type surfactants should concentrate at around C₁₈.     

A review of: “Nineteenth Century Attitudes: Men of Science (Chemists and Chemistry Series,Vol. 13)”. Sydney Ross. Kluwer Academic Publishers; Dordrecht, 1991. pp. xi+235. $69.00.

Abstract

The potential of polytetrafluoroethylene (PTFE) membranes as water‐in‐oil (W/O) emulsification devices was investigated to obtain uniformly sized droplets and to convert them into microcapsules and polymer particles via subsequent treatments. Uniform W/O emulsion droplets have not been achieved using glass membranes unless the membrane was rendered hydrophobic by treatment with silanes. If a PTFE membrane is capable of providing uniform droplets for a W/O emulsion, a coordinated membrane emulsification system can be established since glass membranes have been so successful for O/W (oil‐in‐water) emulsification. In order to examine the feasibility of PTFE membrane emulsification, O/W and W/O emulsion characteristics prepared using PTFE membranes were compared with those prepared by the conventional SPG (Shirasu porous glass) membrane emulsification method. A 3 wt.% sodium chloride solution was dispersed in kerosene using a low HLB surfactant. Effects of the membrane pore size, permeation pressure, and the type of emulsifiers and concentration on the droplet size and on the size distribution (CV, coefficient of variation) were investigated. The CV of the droplets was fairly low, and the average droplet size was correlated with the critical permeation pressure of the dispersed phase, revealing that the PTFE membrane could be used as a one‐pass membrane emulsification device. Low CV values were maintained with a Span 85 (HLB = 1.8) concentration, 0.2–5.0 wt.% and a range of HLB from 1.8–5.0. For a brief demonstration of practical applications, nylon‐6,10 microcapsules prepared by interfacial polycondensation and poly(acrylamide) hydrogels from inverse suspension polymerization are illustrated.     

FORMATION OF O/W EMULSIONS BY SURFACTANT PHASE EMULSIFICATION AND THE SOLUTION BEHAVIOR OF NONIONIC SURFACTANT SYSTEM IN THE EMULSIFICATION PROCESS

Surfactant-Phase Emulsification is a very useful method to produce oil-in-water emulsions having fine and uniform droplets. The mechanism of this emulsification method and the effect of hydrophile-lipophile balance (HLB) of the surfactants on the process of this emuisification were investigated by using phase diagrams of nonionic surfactant/hexadecane/water/1,3-butanediol four component systems.

It was shown that the process of this emulsification begins with the formation of isotropic surfactant solution, followed by formation of oil-in-surfactant clear gel emulsion, and finally by formation of oil-in-water emulsion. By using this emulsification technique, fine oil-in-water emulsions were formed without a need for adjusting of HLB.     

A theoretical analysis of micelle-mediated transport through porous membranes

A novel method is proposed for the purpose of controlled release of a sparingly water soluble compound. The solubility of a sparingly water soluble compound can be increased by addition of a sufficient amount of surfactant to form micelles. The flux of the compound across a porous membrane can be enhanced if the membrane has pores larger than the micelle size so that the compound-loaded micelles can diffuse simultaneously, and micelle-mediated transport occurs. The membrane permeability of the micelle is a monotonically decreasing function of the ratio of the size of the micelle to the membrane pore size (R_m/R_p). However, the solubilizing capacity of the micelle increases with increasing size of the micelle. These opposing effects influence the transport and may result in an optimum flux of the solubilizate at a particular size of the micelle. In the determination of the optimum surfactant molecule, the concept of the hydrophilic-lipophilic balance (HLB) is employed in order to have stable aqueous solutions of the surfactants. For a family of nonionic surfactants solubilizing the hydrophobic and hydrocarbon substance n-heptane, it is shown that there exists a maximum flux of the solubilizate at a value of R_m/R_p within the limitation of the HLB. The release rates over a long period of time are nearly constant for micelles close to the optimum size for a given pore size.     

New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM‐41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real Samples

New methylene blue (NMB) dye incorporated into AlMCM‐41 surfactant‐free and hybrid surfactant‐AlMCM‐41 mesophase. UV‐vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H₃O⁺ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (E_m) values show that new methylene blue dye incorporated into AlMCM‐41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br^? ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue‐AlMCM‐41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10^?5 to 5.0×10^?4 M. The detection limit of the method is 1.0×10^?5 M, low enough for trace ascorbic acid determination in various real samples.     

Optimization of Oil-in-Water Emulsion Stability: Experimental Design,Multiple Light Scattering,and Acoustic Attenuation Spectroscopy

To find an optimal formulation of oil-in-water (O/W) emulsions (φ_o = 0.05), the effect of emulsifier nature and concentration, agitation speed, emulsifying time, storage temperature and their mutual interactions on the properties and behavior of these dispersions is evaluated by means of an experimental design (Nemrodw software). Long-term emulsion stability is monitored by multiple light scattering (Turbiscan ags) and acoustic attenuation spectroscopy (Ultrasizer). After matching surfactant HLB and oil required HLB, a model giving the Sauter diameter as a function of emulsifier concentration, agitation speed and emulsification time is proposed. The highest stability of C₁₂E₄-stabilized O/W emulsions is observed with 1% emulsifier.     

Effect of Amino‐Acid‐Based Polar Oils on the Krafft Temperature and Solubilization in Ionic and Nonionic Surfactant Solutions

Abstract

The Krafft temperature and solubilization power of ionic and nonionic surfactants in aqueous solutions are strongly affected by added polar oils such as amino‐acid‐based oils (e.g., N‐acylamino acid esters, AAE), because they tend to be solubilized in the surfactant palisade layer. The Krafft temperatures of 5 wt.% sodium dodecyl sulfate (SDS)‐water and octaoxyethylene octadecyl ether (C₁₈EO₈)‐water systems largely decreases upon addition of AAE and 1‐hexanol, whereas it decreases very slightly in isopropyl myristate (IPM) and n‐dodecane. The lowering of the Krafft temperature can be explained by the same mechanism as the melting‐temperature reduction of mixing two ordinary substances. Namely, the polar oils are solubilized in the surfactant palisade layer of micelles and reduce the melting temperature of hydrated solid‐surfactant (Krafft temperature). On the other hand, non‐polar oil such as dodecane is solubilized deep inside micelles and makes an oil pool. The solubilization of non‐polar oil is enhanced by mixing surfactant with AAE due to an increase in micellar size.     

Quantitative effect of nonionic surfactant partitioning on the hydrophile-lipophile balance temperature

Phase behaviors of water/nonionic surfactants/isooctane systems are determined experimentally in temperature-global surfactant concentration diagrams. The surfactants are monodistributed polyoxyethylene glycol n-dodecyl ether. They are used as model mixtures of two, three, or five compounds or as constituents of a commercial surfactant. It is found that the phase diagrams of these systems are bent gradually toward the highest temperatures as the global surfactant concentration decreases. Each phase diagram is well-characterized by the curve of the HLB (hydrophile-lipophile balance) temperature versus the global surfactant concentration. For any fixed global surfactant concentration, this temperature is the middle temperature of the three-phase region; it can be calculated from an additive rule of the HLB temperatures of the surfactants weighted by their mole fractions at the water/oil interface. These mole fractions are determined through the pseudophase model using surfactant partitioning. Calculations require the knowledge of the critical micelle concentration, the partition coefficient between water and oil, and the HLB temperature of each surfactant of the mixture. This treatment can be used to correctly predict the variation of the HLB temperatures of the surfactant mixtures studied versus the global surfactant concentration. Furthermore, these calculations show that the observed curvature of the phase diagrams at the lowest global concentrations is due to the most favorable partitioning toward the oil of the lowest ethoxylated surfactant molecules.     

Effect of Association of Bromophenol Blue with Tween Surfactants on Its Acid-Base Equilibria at High pH

The acid base equilibria of the sulfonephthalein dye bromophenol blue (BPB) in aqueous nonionic micellar solutions of Tween 20, Tween 40, Tween 60, and Tween 80 have been investigated spectroscopically using a partition equilibrium method. A visible red shift in the absorbance of the basic form of the dye with increase in surfactant concentration was observed at and above pH 6.98. This has been attributed to the stabilization of the acid form of the dye by the POE groups on the head of the surfactant monomers. Such stabilization effect was found to decreases with decrease in the number of carbon atom in the hydrophobic tail and with the increase in the hydrophile-lipophile balance (HLB) of the surfactant molecule. The equilibrium constant of the partition of the dyes between micellar and aqueous pseudophases (K_ass) was found to increase with the surfactants in the order Tween 80 < Tween 60 < Tween 40 < Tween 20. The pK_a2 of the dyes were predicted and found to be in good agreement with the experimental values.     

Microwave-assisted micellar extraction coupled with solid-phase extraction for preconcentration of pharmaceuticals in molluscs prior to determination by HPLC

A simple and specific analytical method was developed and tested for the determination of pharmaceuticals in mollusc samples. A combination of microwave-assisted micellar extraction (MAME) and solid-phase extraction (SPE) using a non-ionic surfactant, polyoxyethylene 10 lauryl ether, was examined to extract and determine simultaneously a group of pharmaceuticals such as carbamazepine, clorfibric acid, ketoprofen, naproxen, bezafibrate and ibuprofen by liquid chromatography using UV-diode array detector. The MAME extraction performance was evaluated by studying various parameters such as the volume and concentration of surfactant and microwave conditions. Finally, an OASIS HLB cartridge was used as an optimum SPE sorbent to clean up the extracts and preconcentrate the selected analytes. The proposed method showed satisfactory linearity and reproducibility (between 3 and 15%), as well as detection limits ranging from 30 to 220 ng/g. Finally, the method was successfully applied to the determination of the target pharmaceuticals in various kinds of mollusc samples. This study has demonstrated that microwave-assisted micellar extraction with solid-phase extraction may be used as a viable alternative to conventional methods for the extraction of pharmaceuticals in this type of matrices.     

A new modified low-energy emulsification method for preparation of water-in-diesel fuel nanoemulsion as alternative fuel

In this research, 24 of water-in-diesel fuel nanoemulsions were prepared using mixed nonionic surfactants of sorbitan monooleate and polyoxyethylene sorbitan trioleate (MTS). The emulsions were formed using a new modified low-energy method at hydrophilic-lipophilic balance (HLB) value of 10 and a working temperature of 20°C. Five HLB values of 9.6, 9.8, 10, 10.2, and 10.4 were prepared to identify the optimum value that gives low water droplet size at working conditions as: 5 wt% of water contents, 10 wt% of mixed surfactant concentration, and a temperature of 20°C. The effect of mixed surfactant concentration and water content on the droplet size for 0, 15, 30, 60, and 90 days has been studied. Droplet size of the prepared nanoemulsions was determined by dynamic light scattering and the nanoemulsion stability was assessed by measuring the variation of the droplet size as a function of time. Results show that the mean droplet sizes were formed between 26.23 and 277.1 nm depending on the surfactant concentrations, water contents, and storage time.     

Influence of the HLB parameter of surfactants on the dispersion properties of brine in residue

In order to study the relationship between the hydrophilic–lipophilic balance of surfactants and the dispersion properties of brine in residue, using droplet size and droplet distribution analytical method were determined on emulsions prepared with emulsifier blends of varying hydrophilic–lipophilic balance (HLB) values the required HLB values of emulsion. The objective of this study was to investigate the effect of HLB on the dispersion properties of brine in residue. The type of emulsion was prepared using emulsifiers with various hydrophilic–lipophilic balance values. The droplet size and droplet distribution varied widely among emulsions containing emulsifiers with different HLB values. The results obtained in this study indicate that the different systems of residue/brine need different HLB values. The HLB value of the emulsion with the least dispersion ratio or the least average droplet diameter was taken as the system of residue/brine required HLB the required HLB values of (NH₄)₆Mo₇O₂₄·4H₂O, Co(NO₃)₂, NiSO₄, Ni(NO₃)₂ and FeSO₄. The results showed that the values of HLB were determined as different system of emulsion.     

MINIEMULSION FORMATION BY TRANSITIONAL INVERSION

Very fine emulsions with droplet size in the sub-micron range, often called miniemulsions, are prepared by the moderate (magnetic) stirring of a system undergoing a dynamic transitional inversion driven by a continuous change in physicochemical formulation (here temperature). Near optimum formulation for three-phase systems, the ultralow interfacial tension favors the drop breaking rate, and fine emulsions can be made. However, this region is also known for its rapid coalescence rate. Thus, a high enough stability can be attained only by shifting the formulation away from optimum as soon as the emulsion is made. Moreover, a rapid change in formulation through the three-phase region also results in a separation phenomenon that can be harnessed to produce ultra fine droplets.

The phase behavior of surfactant-oil-water systems and emulsion properties (type, droplet size and stability) are studied as a function of surfactant concentration (2 wt.% and 6 wt.%), for two different nonionic surfactants (polyoxyethylene tri-terbutyl ethers and sorbitan derivatives) with HLB ranging from 4 to 16. Kerosene and paraffin oil are used as oil phases. The transitional inversion form W/O to O/W is induced by a rapid cooling of the stirred systems from above to below the optimum temperature for three-phase behavior.

Miniemulsions are attained when the surfactant concentration is high enough, and when the temperature quenching span covers an appropriate range related to phase behavior.     

Study of the required HLB for the solubilization of cholesterol in aqueous solution

 The solubilization of cholesterol by anionic surfactant mixtures was studied as a function of their HLB values. The relationship between the logarithm of the critical micelle concentration and the HLB value of the mixtures was not linear, which was attributed to a lack of strict additivity of the HLB values. The solubilized cholesterol/surfactant ratio was determined and it was found to be higher than that in bile salts in all the studied surfactant mixtures. Below HLB=24, emulsions were obtained, and the remaining cholesterol was solid. Above that value, limpid solutions were obtained, giving a solubility maximum at HLB≈35. The non-solubilized cholesterol was mainly in the form of lamellar mesophase. Received: 23 June 1997 Accepted: 12 August 1997     

Adsorption of the anionic surfactant sodium dodecyl sulfate on a C18 column under micellar and high submicellar conditions in reversed‐phase liquid chromatography

Micellar liquid chromatography makes use of aqueous solutions or aqueous‐organic solutions containing a surfactant, at a concentration above its critical micelle concentration. In the mobile phase, the surfactant monomers aggregate to form micelles, whereas on the surface of the nonpolar alkyl‐bonded stationary phases they are significantly adsorbed. If the mobile phase contains a high concentration of organic solvent, micelles break down, and the amount of surfactant adsorbed on the stationary phase is reduced, giving rise to another chromatographic mode named high submicellar liquid chromatography. The presence of a thinner coating of surfactant enhances the selectivity and peak shape, especially for basic compounds. However, the risk of full desorption of surfactant is the main limitation in the high submicellar mode. This study examines the adsorption of the anionic surfactant sodium dodecyl sulfate under micellar and high submicellar conditions on a C₁₈ column, applying two methods. One of them uses a refractive index detector to obtain direct measurements of the adsorbed amount of sodium dodecyl sulfate, whereas the second method is based on the retention and peak shape for a set of cationic basic compounds that indirectly reveal the presence of adsorbed monomers of surfactant on the stationary phase.     

STABILIZATION OPTIMIZATION OF AQUEOUS MONOMER SOLUTIONS IN OIL EMULSIONS USING THE COHESIVE ENERGY RATIO CONCEPT.

The Beerbower-Hill approach based on the Cohesive Energy Ratio concept (CER) has been applied in order to optimize the stabilization of Acrylamide-water or Acrylic Acid (pure and 80% neutralized)- water mixtures in cyclohexane emulsions.

Using surface tension measurements for the determination of the solubility parameter of the aqueous phase ( δ_w), it was found that the presence and amount of the water-soluble monomer could be accounted for the evaluation of the optimal HLB.

Predictions were compared to experimental HLB values obtained by using various blends of a low-HLB emulsifier (a sorbitan monooleate named MONTANE 80) and high-HLB emulsifiers (either a nonylphenolpolyoxyethylene [40 EO] or a pOE [20 EO] sorbitan trioleate, MONTANOX 85).     

Stability of polymethyl methacrylate latex dispersions prepared by using mixtures of anionic and nonionic surfactants

Summary A series of polymethyl methacrylate latex dispersions has been prepared by emulsion polymerization using various combinations of anionic and non-ionic surfactants. The effect of surfactants present in the process of emulsion polymerization on the stability of latex dispersions has been investigated. The particle diameter increases with the increase of the content of a nonionic surfactant. It also depends on the HLB values of the nonionic surfactants used. The values of critical coagulation concentration of latex dispersions were found to increase with the increase of the content of a nonionic surfactant in the surfactant blends, and also increase with the decrease of the HLB value of the nonionic surfactant. The Hamaker constant of latex dispersions decreases with the increase of the content of a nonionic surfactant. It decreases remarkably with the decrease of the HLB value of a nonionic surfactant used. The Stern potential decreases markedly with the increase of the content of nonionic surfactant. It also decreases with the decrease of HLB value of a nonionic surfactant used.

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Zusammenfassung Eine Serie Latex-Dispersionen von Polymethyl-Methacrylat wurde durch Emulsionspolymerisation unter Verwendung verschiedener Kombinationen von anionischen und nichtionischen oberflächenaktiven Agentien hergestellt. Der Effekt der oberflächenaktiven Agentien, der sich im Prozeß der Emulsions polymerisation in bezug auf die Stabilität der Latex-Dispersionen zeigt, wurde untersucht. Der Teilchendurchmesser nimmt mit der Zunahme des Gehaltes vom nichtionischen oberflächenaktiven Agens zu. Erist auch abhängig von den HLB-Werten der gebrauchten nichtionischen oberflächenaktiven Agentien. Der Wert der kritischen Koagulationskonzentration der Latex-Dispersionen nimmt mit der Zunahme des Gehaltes vom nichtionischen oberflächenaktiven Agens in den Gemischen der oberflächenaktiven Agentien zu, ebenso mit der Abnahme der HLB-Werte der nichtionischen oberflächenaktiven Agentien. Die Hamaker-Konstante der Latex-Dispersionen nimmt mit der Zunahme des Gehaltes vom nichtionischen oberflächenaktiven Agens ab. Sie nimmt auch mit der Abnahme der HLB-Werte des gebrauchten nichtionischen oberflächenaktiven Agens bemerkenswert ab. Das Stern-Potential nimmt mit der Zunahme des Gehaltes vom nichtionischen oberflächenaktiven Agens auffallend ab. Es nimmt auch mit der Abnahme des HLB-Wertes des gebrauchten nichtionischen oberflächenaktiven Agens ab.

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With 8 figures and 5 tables     

Phase Behavior of n‐Butanol/n‐Octane/Water/Cationic Gemini Surfactant System

Phase diagrams of the n‐butanol/n‐octane/water/(12‐3‐12,2Br^?1) system were determined, where n‐octane usually represents oil (O), 12‐3‐12,2Br^?1 is a gemini cationic surfactant trimethylene‐1,3‐bis(dodecyldimethyl ammonium bromide) abbreviated as S, and n‐butanol is a co‐surfactant written as A. Effects of the weight ratio of gemini surfactant to cosurfactant, S/A, and of temperature on the phase behavior were studied. The microemulsion structures including O/W, bi‐continuous (B.C.), W/O, and liquid crystal were determined by the conductivity method and polarization measurement. Experimental results show that the gemini surfactant, used facilitates the formation of microemulsions compared with its corresponding monomeric surfactant, n‐dodecyl trimethylammonium bromide (DTAB). When S/A=1/1, and the total concentration of gemini surfactant and alcohol is 20–40%, microemulsions with higher water content can form in a wider region. When the temperature increases, the size and position of each type of microemulsion region changes notably.     

Surfactant‐based ionic liquids for extraction of phenolic compounds combined with rapid quantification using capillary electrophoresis

A rapid liquid phase extraction employing a novel hydrophobic surfactant‐based room temperature ionic liquid (RTIL), tetrabutylphosphonium dioctyl sulfosuccinate ([4C₄P][AOT]), coupled with capillary electrophoretic‐UV (CE‐UV) detection is developed for removal and determination of phenolic compounds. The long‐carbon‐chain RTIL used is sparingly soluble in most solvents and can be used to replace volatile organic solvents. This fact, in combination with functional‐surfactant‐anions, is proposed to reduce the interfacial energy of the two immiscible liquid phases, resulting in highly efficient extraction of analytes. Several parameters that influence the extraction efficiencies, such as extraction time, RTIL type, pH value, and ionic strength of aqueous solutions, were investigated. It was found that, under acidic conditions, most of the investigated phenols were extracted from aqueous solution into the RTIL phase within 12 min. Good linearity was observed over the concentration range of 0.1–80.0 μg/mL for all phenols investigated. The precision of this method, expressed as RSD, was determined to be within 3.4–5.3% range. The LODs (S/N = 3) of the method were in the range of 0.047–0.257 μg/mL. The proposed methodology was successfully applied to determination of phenols in real water samples.