Maximum Water Solubilization Research Articles

Effect of alcohols on water solubilization in surfactant-free diesel microemulsions

Microemulsions are preferred over other methods of mixing two immiscible liquids as they are thermodynamically stable, but require a high percentage of surfactant. Surfactant-free microemulsions, on the other hand, use an amphisolvent instead of surfactants, making them an economical alternative. The current experimental investigation focuses on formulation of surfactant-free water-in-diesel microemulsions with the help of straight-chain aliphatic alcohols as diesel replacement for IC engines. Dynamic light scattering measurements revealed these microemulsions had average water droplets of less than 10 nm. The microemulsions were formulated using single-alcohol, two-alcohols, and three-alcohols. It becomes crucial to study the water solubilization of microemulsions as the addition of water in diesel improves combustion efficiency. The water solubilization in surfactant-free microemulsions was found to be dependent on the hydrophilic–lipophilic balance (HLB) of the alcohols, as it determined the solubilizing property of alcohol. The microemulsions could only be formulated in the HLB range of 6.27 to 7.76 and were found to have maximum water solubilization in the HLB range of 6.67 to 7.63. Butanol had the highest water solubilization in a single alcohol system, butanol–ethanol in the ratio of 3:1 for the two-alcohol system, and propanol–butanol–octanol in the ratio of 3:1:1 for three-alcohol systems. Alcohols with higher HLB were more hydrophilic, causing migration of alcohol from the interface to bulk water. In comparison, alcohol with a lower HLB caused the migration of alcohol from the interface to bulk diesel, which resulted in reduced water solubilizations. Hence, the microemulsions could not be formulated beyond specific HLB range. The formulated microemulsions could be a prospective substitute for diesel fuel as alcohols can be derived from renewable routes.

Structure and pseudo-ternary phase diagram of water/Triton X-100/1-pentanol/cyclohexane microemulsion

To gain insight into the structure and properties of microemulsions, pseudo-ternary phase diagrams of water/Triton X-100/1-pentanol/cyclohexane microemulsions which were constructed by using cyclohexane as oil, Triton X-100 as surfactant, 1-pentanol as cosurfactant and water as the hydrophilic phase were determined at different temperatures through measuring electrical conductivity. Maximum water solubilization was determined by optimizing the mass ratio of surfactant to cosurfactant (K = 0.75). SAXS, NMR, ATR-FTIR, DSC and rheometer were applied to analyze the structure and other properties of microemulsions. The phase transitions of microemulsion system were discussed at the dilute water line and the nanostructure sizes of the microemulsions were determined. In addition, the type of water in W/O microemulsion was specifically analyzed.

Dyeing properties of CI reactive violet 2 on cotton fabric in non-ionic TX-100/Span40 mixed reverse micelles

In order to improve the dyeing properties of reactive dyes onto cotton fabric in reverse micelles, non-ionic mixed reverse micelles were prepared using non-ionic TX-100 and Span40 as a dyeing media. The maximum water solubilization, diameter of water pool, aggregation density, and conductivity values of the reverse micelles with different concentrations of TX-100/span40 were measured and compared. The adsorption and dyeing capacity of reactive dyes on cotton fabric in reverse micelles were investigated. Additionally, the Lagergren first-order equation and the pseudo second-order equation were also employed to fit the experimental data. The results indicated that the diameter of water pool and packing density of reverse micelles were increased with an increasing amount of Span40, which caused lower conductivity. The repelling force and competitive adsorption between the dyes and cotton fabric were decreased with an increasing amount of Span40, and the higher adsorption and improved dyeing properties in reverse micelles were obtained. Moreover, the dye adsorption process in mixed TX-100/Span40 reverse micelles could be described using pseudo-second-order kinetic equations. The adsorption is a chemical process.

Physicochemical investigation of mixed surfactant reverse micelles: Water solubilization and conductometric studies

Abstract Solubilization of water in mixed reverse micelles (RMs) comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and polyoxyethylene (20) sorbitan trioleate (Tween-85) or polyoxyethylene (20) sorbitan monooleate (Tween-80) or sorbitan trioleate (Span-85) has been studied at different compositions ( X nonionic = 0–1.0) at a total surfactant concentration, S T = 0.1 mol dm −3 in polar lipophilic oils of different chemical structures: viz., ethyl oleate (EO), isopropyl myristate (IPM) and isopropyl palmitate (IPP) at 303 K. The enhancement in water solubilization (i.e., synergism) has been evidenced by the addition of nonionic surfactant to AOT/oil(s)/water systems. The maximum water solubilization capacity ( ω 0,max ) and X nonionic,max (mole fraction at which synergism occurs) have been influenced by polar head group and hydrophobic moiety of nonionic surfactant. The standard free energy change of dissolution of water ( Δ G s 0 ) of these systems depends on water content, X Tween-85 and oil. Solubilization efficiency parameter ( S P water * ) has been evaluated to underline the efficacy of oils in obtaining maximum water solubilization capacity in mixed RMs. Conductance behavior of these systems in absence and presence of additives (bile salts and hydrotrope) has also been investigated under varied water content ( ω ) at 303 K. Volume-induced percolation threshold ( ω p ) depends on X Tween-85 , oil type, and additives. An attempt has been made to give an insight to the mechanism of solubilization phenomena, standard free energy change of dissolution of water, percolation in conductance and microstructures of these systems by dynamic light scattering (DLS) measurements, wherein the chemical structures of both nonionic surfactants and polar lipophilic oils played significant role.

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

AbstractIn this study the effect of an anionic surfactant (sodium dodecyl sulfate SDS) and oils (hydrocarbons: C12–C16) on the formation and phase behavior of the systems of oil/monoacylglycerols (MAG):SDS/propylene glycol/water has been investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C). Electrical conductivity measurement, FT‐IR spectroscopy and differential scanning calorimetry methods were applied to determine the structure and type of the microemulsions formed. The dimension of microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of SDS has a strong influence on the shape and extent of the microemulsion areas. Addition of an ionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of the isotropic region change with the temperature. It was shown that the presence in the systems of a surfactant more hydrophilic than MAG caused an increase in water content in the microemulsions. It was found that, depending on temperature and concentration of the surfactant mixture, it was possible to obtain a W/O type microemulsion with a dispersed particles size distribution ranging from 20 to 50 nm and containing about 17–38% water in the system. Among different alkanes (from C12 to C16), hexadecane embedded microemulsions showed a maximum water solubilization capacity.

Properties of Microemulsions with Mixed Nonionic Surfactants and Mint Oil

Abstract In this study we used electrical conductivity, dynamic viscosity, dynamic light scattering, and small angle X-ray scattering for the characterization of the water + propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/peppermint oil microemulsion systems. The maximum water solubilization in the peppermint oil was found to be dependent on the surfactants mixing ratio (w/w). A Static percolation threshold was determined. The activation energy of conductive flow depends on the surfactants mixing ratio. The hydrodynamic diameter of the diluted microemulsions decreases with the increase in temperature. The periodicity d of the microemulsions increases with the increase in the aqueous phase content. The correlation length ξ increases and decreases with the increase in the aqueous phase content indicating the onset of structural transitions.

The effect of structural variation of alcohols on water solubilization in nonionic microemulsions: 1. From linear to branched amphiphiles—General considerations

This article is the first part of a two-part study that exemplifies how to treat the solubilization of water in multicomponent surfactant-based systems. In particular, it aims at clarifying the role of cosurfactants in water solubilization in these systems. The judicious selection of the components in such systems to maximize water solubilization is occasionally thought to be dictated by the chain length compatibility principle, which may be expressed quantitatively by the BSO (Bansal, Shah, O'Connell) equation. Here we demonstrate some limitations of the equation. For example, in our best model system, C 12(EO) 8/dodecane + pentanol = 1:1 (by weight)/water at 27 ± 0.2 ° C , the BSO equation predicts that no alcohol is needed for maximum water solubilization, contrary to our experimental findings. We discuss how to optimize the alcohol/oil weight ratio needed for stabilizing four-component microemulsions. In our model systems C 12(EO) 8 or C 18:1(EO) 10/pentanol/dodecane/water, this optimal weight ratio is 1:1. We also highlight the difference between the effect of normal alcohols on water solubilization—which passes via a maximum—and their effect on percolation processes and structured changes of proteins, which depends solely upon the alcohol hydrophobicity. For the investigation of the effect of branching on phase behavior the utilization of an extended form of the geometrical branching factor F b is suggested. The meaning of this factor is elucidated by comparing it with topological indices.

Water solubilization capacity of mixed reverse micelles: Effect of surfactant component, the nature of the oil, and electrolyte concentration

Solubilization of water in mixed reverse micellar systems with anionic surfactant (AOT) and nonionic surfactants (Brijs, Spans, Tweens, Igepal CO 520), cationic surfactant (DDAB)–nonionic surfactants (Brijs, Spans, Igepal CO 520), and nonionic (Igepal CO 520)–nonionics (Brijs, Spans) in oils of different chemical structures and physical properties (isopropyl myristate, isobutyl benzene, cyclohexane) has been studied at 303 K. The enhancement in water solubilization has been evidenced in these systems with some exceptions. The maximum water solubilization capacity ( ω 0 , max ) in mixed reverse micellar systems occurred at a certain mole fraction of a nonionic surfactant, which is indicated as X nonionic , max . The addition of electrolyte (NaCl or NaBr) in these systems tends to enhance their solubilization capacities further both at a fixed composition of nonionic ( X nonionic ; 0.1) and at X nonionic , max at 303 K. The maximum in solubilization capacity of electrolyte ( ω max ) was obtained at an optimal electrolyte concentration (designated as [NaCl] max or [NaBr] max). All these parameters, ω 0 , max vis-à-vis X nonionic , max and ω max vis-à-vis [NaCl] max, have been found to be dependent on the surfactant component (content, EO chains, and configuration of the polar head group, and the hydrocarbon moiety of the nonionic surfactants) and type of oils. The conductance behavior of these systems has also been investigated, focusing on the influences of water content ( ω), content of nonionics ( X nonionic ), concentration of electrolyte ([NaCl] or [NaBr]), and oil. Percolation of conductance has been observed in some of these systems and explained by considering the influences of the variables on the rigidity of the oil/water interface and attractive interactions of the surfactant aggregates. Percolation zones have been depicted in the solubilization capacity vs X nonionic or [electrolyte] curves in order to correlate with maximum in water or electrolyte solubilization capacity. The overall results, obtained in these studies, have been interpreted in terms of the model proposed by Shah and co-workers (Langmuir 3 (1987) 1086; J. Colloid Interface Sci. 120 (1987) 320 and 330) for the solubility of water in water-in-oil microemulsions, as their model proposed that the two main effects that determine the solubility of these systems are curvature of the surfactant film separating the oil and water and interactions between water droplets.

Effect of NaCl and temperature on the water solubilization behavior of AOT/nonionics mixed reverse micellar systems stabilized in IPM oil

Solubilization of water in mixed reverse micellar systems formed with anionic surfactant (AOT) and nonionic surfactants (Brij-30, Brij-35, Brij-52, Brij-56, Brij-58, Brij-76, Tween-20, Tween-40, Span-20, Span-40, Span-60, Span-80) in isopropyl myristate (IPM) oils has been studied. The enhancement in water solubilization (i.e. synergism) has been evidenced by the addition of nonionic surfactants to AOT/IPM system. The maximum water solubilization capacity ( ω 0,max) and the mole fraction of nonionic surfactant at which maximization occurs ( X nonionic,max) in these mixed reverse micellar systems has been found to depend on surfactant component (size and nature of polar group and hydrocarbon moiety of the surfactant). The addition of electrolyte (NaCl) in these systems has been found to enhance the solubilization capacity ( ω max) depending upon the content and their EO chains and type of polar head group of nonionic surfactant used. The maximum solubilization of electrolyte, ω max was obtained at an optimal concentration of it ([NaCl] max), which depends on the content and their EO chains and type of polar heads of the nonionic surfactants. The temperature induced solubilization of water (in absence and presence of additives) for AOT blended with nonionic surfactants (Brijs, Tweens, Spans) at different compositions has been investigated. The stability of these systems with respect to temperature has been found to be dependent on the content and nature of the polar head group as well as the hydrophobic moiety of the nonionics. The energetic parameters ( Δ G ¯ ° , Δ H ¯ ° and Δ S ¯ ° ) of the desolubilization process of water in the mixed systems have been estimated from the solubilization capacity–temperature profile. An attempt has been made to shed more insight into the process of solubilization–desolubilization of water (or aqueous NaCl) in mixed reverse micelles stabilized in IPM oil on the basis of the model proposed by Shah et al. [M.J. Hou, D.O. Shah, Langmuir 3 (1987) 1086; R. Leung, D.O. Shah, J. Colloid Interf. Sci. 120 (1987) 320, 330] and thermodynamic approach.

Phase Behavior and Formation of Microemulsions in Water/A−B−A Block Copolymer (Polyhydroxystearic Acid−Polyetylene Oxide−Polyhydroxystearic Acid)/1,2-Alkanediol/Isopropyl Myristate Systems

Phase diagrams of the ternary system water/poly(12-hydroxystearic acid)−poly(ethylene oxide)−poly(12-hydroxystearic acid) (PHS−PEO−PHS)/isopropyl myristate and the quaternary system water/PHS−PEO−PHS/1,2-alkanediol/isopropyl myristate were investigated at 25 °C. The alkanediols tested in this work are 1,2-hexanediol and 1,2-octanediol. The different phases formed have been examined by optical (phase contrast and polarizing) microscopy. The nature of the continuous media has been determined by conductivity. Particular attention was paid to the L2 (water-in-oil micoremulsion). The amount of water solubilized in this region increases as the surfactant concentration increases. The minimum content of polymeric surfactant and cosurfactant for maximum water solubilization is about 37%. The present investigation has also shown the relation between the oil polarity and the maximum water content that can be solubilized in microemulsions.

A DSC study of water behavior in water-in-oil microemulsions stabilized by sucrose esters and butanol

Sub-zero temperature differential scanning calorimetry (SZT-DSC) has been applied to a model nonionic water-in-oil microemulsion system based on: sucrose esters/water/1-butanol/ n-alkanes (C 12–C 16). The maximum water solubilization was 40, 56 and 80 wt.% for the systems containing n-dodecane, n-tetradecane and n-hexadecane as the oil phase, respectively. Two types of solubilized water have been detected. The so-called ‘bulk’ (free) water present in the core of the microemulsion and the ‘interfacial’ (bound) water attached at the interface to the surfactant (and/or butanol). The internal distribution of the water within the microemulsions was determined along two dilution lines (with 32 and 43 wt.% of the initial surfactant). It was found that for the n-dodecane system the maximum ‘interfacial’(bound) water is 12 and 14 wt.% along the two dilution lines, respectively. Above this water content a core of ‘bulk’ (free) water is formed. The type of the oil and the butanol interfacial participation strongly affect the water internal distribution. Both the temperature of fusion, T f, of the ‘bulk’ (free) water and of the ‘interfacial’ (bound) water are strongly affected by the butanol and the oil. The nature of the surfactant, its fatty chain length and its HLB also affect the binding capabilities and capacity of water in microemulsion systems. For both n-dodecane and n-hexadecane, 11–13 molecules of water can be bound to the surfactant at the interface.

FRAGRANCE EMULSIONS STABILIZED BY A TRIBLOCK COPOLYMER

The phase diagram was determined of the system a fragrance oil, phenethyl alcohol, a commercial triblock copolymer, PE/L101, and water. The stability of emulsions containing 95 wt% water and various amounts of the fragrance and polymer was investigated both visually and with the aid of an optical microscope. The stability of the two-phase emulsions was explained through the interfacial behavior of the polymer and the density change of the oil phase. Double emulsions were found to form when the oil phase composition is close to that of the L2 phase with maximum water solubilization.

Non-ionic sucrose esters microemulsions for food applications. Part 1. Water solubilization

Factors affecting water solubilization in four-component nonionic microemulsion systems stabilized by polyol nonionic surfactants (sucrose esters) have been investigated. The effect of changing the chain length of alcohol (used as cosurfactant) and the lipophilic moiety of surfactant have been explored. The maximum water solubilization in the isotropic region (at oil/ n-butanol ratio of 1) was 47, 23 and 55 wt.% for sucrose stearate (S-1570), sucrose laurate (L-1695) and sucrose palmitate (P-1570), respectively. Replacing the triglyceride oil (MCT) by dodecane caused a decrease in the water solubilization (40 wt.%) for sucrose stearate with an oil/ n-butanol ratio of 1. The empirical BSO (Bansal, Shah, O’Connell) [1] equation which was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths, i.e. N S= N O+ N A, where N S, N O, N A are the surfactant chain lengths, oil and alcohol, respectively, was re-examined for this type of surfactants. This study demonstrates that a maximum water solubilization is obtained when the N S=( N O±3)+ N A for N S is greater than 14; when N S is less than 14, this equation cannot predict the maximum water solubilization.

Reverse Micelle Formation and Water Solubilization by Polyoxyalkylene Block Copolymers in Organic Solvent

A systematic investigation of the effects of polymer chemical composition and molecular mass on (i) the micellization of polyoxyalkylene block copolymers [poly(ethylene oxide)/poly(propylene oxide), PEO/PPO, and poly(ethylene oxide)/poly(butylene oxide), PEO/PBO] in an organic solvent (p-xylene: selective solvent for the PPO and PBO blocks) in the presence of some water and (ii) the solubilization of water (selective solvent for the PEO blocks) in these systems is presented. The ability of the (“reverse”) micelles to solubilize water has been employed for the detection of the critical micellization concentration (“reverse” cmc). The “reverse” cmc values were in the range 0.01−0.1 m (5−20 wt %), while the maximum water solubilization values were 0.3−0.5 g of water per g of copolymer. The cmc decreased with increasing copolymer molecular mass for a given copolymer chemical composition. A notable increase (more than doubling) in the water solubilization capacity (expressed in water molecules per EO segment)...

Water Solubilization and Chain Length Compatibility in Nonionic Microemulsions

The BSO (Bansal, Shah, O'Connell) equation ( J. Colloid Interface Sci. 75, 462, 1980) was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths. The present study examines, for the first time, the applicability of this equation for nonionic microemulsions. By constructing pseudo-ternary phase diagrams and measuring the area of the single phase regions as well as the water contents at the boundary, we find that the solubilization capacity is directly related to the alcohol chain length only if the alcohol solubility in both the aqueous and oleic phases is limited. In addition, we try to integrate the concept of chain length compatibility with the competition between the natural curvature and the critical radius of the interface. The attempt to unify the experimental results may serve as a guideline for optimization of microemulsion systems.

Microemulsion formation and metal extraction in the system water/aerosol OT/extractant/isooctane

The effects of metal extractants anti-2-hydroxy-5-nonylbenzophenone oxime (HNBPO), Versatic 10, and di(2-ethylhexyl)dithiophosphoric acid (DEHDTPA) on the maximum water solubilization in Aerosol OT/isooctane-based systems have been investigated. DEHDTPA was found to substantially increase the water uptake, while HNBPO and Versatic 10 gave less improvement or a reduction in water uptake. The result is highly dependent on the presence of Cu 2+. In addition dithiophosphoric acid lowered the HLB temperature of the Aerosol OT-based system, even more so when combined with copper. The equilibrium distribution of copper in the liquid-liquid extraction by the Aerosol OT/Versatic 10/isooctane mixture clearly demonstrates the significance of a proper balancing of the hydrophilic/lipophilic properties of the surfactant mixture. Below the HLB temperature extraction takes place already at pH 1.8, while above the HLB temperature the extraction is efficiently obstructed at this pH.

MONOHEXYL ETHER OF ETHYLENE GLYCOL AND DIETHYLENE GLYCOL AS MICROEMULSION COSURFACTANTS

ABSTRACT Hexyl carbitol has been found to give excellent water solubilizing capacity (42–45%) at high heptane level (41–43%) of w/o microemulsions using only 1% of SDS or CTAB. However, the maximum water solubilization decreased considerably as hexyl carbitol and heptane were replaced by hexyl cellosolve or/and toluene. The latter systems required a much higher concentration of SDS or CTAB. The solubilizing capacities for both systems of hexyl carbitol-heptane-SDS and hexyl carbitol-heptane-CTAB were markedly reduced by the addition of 1.5% NaCl. The effects of the nature of cosurfactant, oil and salinity are explained in terms of interfacial fluidity of the w/o microemulsion droplets.

Solubilization and phase equilibria of water-in-oil microemulsions: I. Effects of spontaneous curvature and elasticity of interfacial films

The solubilization and phase equilibria of w/o microemulsions have been shown to be dependent on two phenomenological parameters, namely the spontaneous curvature and elasticity of the interfacial film, when interfacial tension is very low. The spontaneous curvature of an interface is basically determined by the geometric packing of surfactant and cosurfactant molecules at the interface, whereas the interfacial elasticity is related to the energy required to bend the interface. The droplet size and solubilization of microemulsions is mainly determined by the radius of spontaneous curvature, and is further influenced by interfacial elasticity and interdroplet interactions. A w/o microemulsion with a highly curved and relatively rigid interfacial film can exist in equilibrium with excess water at the solubilization limit due to the interfacial bending stress. Increasing the natural radius and fluidity of the interface can increase the droplet size and hence the solubilization in the microemulsion. On the other hand, a w/o microemulsion with a highly fluid interfacial film can exist in equilibrium with an excess oil phase containing a low density of microemulsion droplets due to attractive interdroplet interaction. Increasing the interfacial rigidity and decreasing the natural radius in this case can increase water solubilization in the microemulsion by retarding the phase separation process. Thus, a maximum water solubilization in a w/o microemulsion can be obtained by minimizing both the interfacial bending stress of rigid interfaces and the attractive interdroplet interaction of fluid interfaces at an optimal interfacial curvature and elasticity. The study of phase equilibria of microemulsions can serve as a simple method to evaluate the property of the interface and provide phenomenological guidance for the formulation of microemulsions with maximum solubilization capacity.