Fishlike Phase Diagram Research Articles

Formation of in-situ microemulsion and its efficiency for residual PCE removal in low temperature aquifers

Microemulsion is used extensively for enhanced oil recovery due to its efficient solubilization. Recently, in-situ microemulsion has been considered to have great potential for remediation of dense non-aqueous phase liquid contaminated aquifers. However, the temperature of aquifers is substantially below that of oilfields (30–120 °C), and the influence of temperature variation on in-situ microemulsion formation and solubilization is unclear. In this work, the efficient in-situ microemulsion for low temperature aquifers were established via the ε-β fishlike phase diagram; the solubilization capacity and size distribution of microemulsion at low temperature of about 10 °C were investigated; and the remediation efficiency of microemulsion flushing for residual tetrachloroethylene (PCE) removal was evaluated. Microemulsion precursor composition of 6.0 wt% compound surfactants (Tween80: SDS=3:2), 8.0 wt% isopropyl alcohol (IPA) and 3.0 wt% NaCl was prepared to form microemulsion with PCE in situ. The PCE apparent solubility was determined to be 80.28 g L−1 at 10 °C, which was three orders of magnitude higher than that in water at the same temperature, about 0.06 g L−1. The solubilization capacity was inversely proportional to temperature and IPA concentration, whereas proportional to Na+ concentration. The microemulsion droplets size were enlarged with the increase of IPA concentration, Na+ concentration and PCE solubilization by DLS experiments. Besides, sand column flushing using various eluents (water, micelle solution, in-situ microemulsion) was conducted to determine the removal efficiency for residual PCE. It was determined that in-situ microemulsion formulations can achieve removal efficiency of 97.1% for residual PCE, which was higher than that flushed via water and micelle solution, about 54.6% and 1.1%. In summary, the results confirm great feasibility of in-situ microemulsion for DNAPLs polluted aquifer remediation.

Construction of zwitterionic surfactant-stabilized hydrophobic ionic liquid-based bicontinuous microemulsion and microstructure-dependent activity of solubilized lipase

In the present work, the sulfobetaine-type zwitterionic surfactant (SB-n) was tried for the first time to construct hydrophobic ionic liquid (HIL)-based bicontinuous microemulsions. The composition-dependent phase behavior of the HIL/water (buffer)/SB-n ternary microemulsion system was determined by the method of T-γ fishlike phase diagram. It is found that the phase inversion temperature increases markedly with the increase of the alkyl chain length (n) of SB-n, but the surfactant efficiency changes little. The HIL greatly affects the phase behavior, depending on the ion structure. It is found that the SB-12 stabilized [C8mim][PF6]-based microemulsion system has moderate phase inversion temperature, and moreover, its surfactant efficiency is the highest among the reported HIL-based bicontinuous microemulsions stabilized by conventional surfactants. The composition-dependent microstructure of the SB-12-stabilized [C8mim][PF6]-based bicontinuous microemulsion was characterized by SAXS technique, and its influence on the catalytic performance of solubilized lipase was also explored. With the increase of the mass ratio of the HIL to water (α), the correlation length (ξ) changes slightly, but the microdomain size (d) decreases steadily. Unlike α, with the increase of the surfactant concentration (γ), the d changes little, but the ξ increases markedly. This abnormal change of ξ with γ should be ascribed to the interface rigidity of the microemulsion. The catalytic efficiency of lipase depends on the rigidity of the interface and its interfacial area. The above original studies not only enrich HIL-based microemulsion systems, but also provide scientific support for lipase-based green synthesis and transformation.

Composition and Solubilization of the Microemulsion Systems Containing Triton X-100: Effects of Aqueous Composition and Oil-Water-Ratios

Abstract The composition and solubilization of the optimum microemulsion systems containing Triton X-100/pentan-1-ol/aliphatic hydrocarbon/water were studied with the ∊-β fishlike phase diagram method. The solubilities of the alkanol (S A), the mass fractions of the alkanol in the interfacial layer (AS ) and the optimum solubilization parameters (SP∗) of the microemulsion systems with different aqueous phases (salt, acid, alkali) and with different α values were obtained and discussed. The SP∗ values increase significantly with the cation radius of the chlorides (NaCl, KCl, CsCl), but decrease slightly with the anion radius of the sodium halides (NaCl, NaBr, NaI). However, SP∗ values decrease with the increased salinities and NaOH contents. The trend was reversed for the acid systems. When the oil-water ratio (α) increases, the S A and A S values significantly increase, while the SP∗ values increase slowly. As the length of the carbon chain of the alkane molecules increases, both the S A and A S values increase, while the SP∗ values decrease significantly.

Horseradish peroxidase-catalyzed oxidative polymerization of aniline in bicontinuous microemulsion stabilized by AOT/SDS

A bicontinuous microemulsion system consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), sodium dodecylsulfate (SDS), an aqueous solution (a 0.1 M disodium hydrogenphosphate/citric acid buffer solution of pH = 4.3), and decane was investigated in detail for applications as reaction medium for the horseradish peroxidase (HRP)/hydrogen peroxide-mediated synthesis of the conductive form of polyaniline (PANI). To formulate the optimal single-phase microemulsion with the phase inversion temperature being close to room temperature, the T-γ fishlike phase diagram of the AOT/SDS-buffer-decane pseudoternary system was determined. The effects of the surfactant concentration (γ), the oil-to-water ratio (α) and the temperature (T) on the conductivity of the resulting PANI and the underlying mechanism were investigated using UV–vis-NIR, ESR and small-angle X-ray scattering (SAXS) techniques. Results show that the bicontinuous microemulsion plays a template role in the PANI biosynthesis, and the PANI conductivity also depends on the activity and stability of the solubilized HRP, which are determined by the microdomain size of the microemulsions and the reaction temperature. As far as γ is concerned, it is found that as γ increases, the microdomain size of the bicontinuous microemulsion as well as the activity of the solubilized HRP decreases significantly, leading to a great decrease of the PANI conductivity. Compared with γ, the change of α has small effect on the PANI conductivity. As the α-dependent microdomain size changes little with increasing α, the small change of the PANI conductivity should be ascribed mainly to the HRP activity. For T, over the range of 20 °C–35 °C, it has a slight effect on the microdomain size of the bicontinuous microemulsion, but it has a marked effect on the enzymatic properties of HRP. As the temperature increases, the activity of HRP increases, but its thermal stability decreases greatly. Therefore, the thermal stability of HRP is the major factor causing that the PANI conductivity decreases significantly with increasing T. The present work deepens the understanding of the template effect of anionic surfactant aggregates in the biosynthesis of conducting PANI. To the best of our knowledge, this work is the first study of the use of bicontinuous microemulsions as reaction media for the enzymatic synthesis of a conducting polymer.

Anionic surfactant-stabilized hydrophobic ionic liquid-based bicontinuous microemulsion: Formulation, microstructure and laccase kinetics

The composition-dependent phase behavior of the [Cmmim][PF6]/buffer/[Cnmim][AOT]/n-butanol pseudoternary microemulsion system was investigated by the method of T-γ fishlike phase diagram. It is found that the phase inversion temperature and the surfactant efficiency decrease with the increase of the alkyl chain length (n) of the surfactant counterion and that (m) of the cation of the hydrophobic ionic liquid (HIL). The [C2mim][AOT]-stabilized [Omim][PF6]-based pseudoternary microemulsion system was found to have high surfactant efficiency and moderate phase inversion temperature. The microstructure of bicontinuous microemulsion formed in the pseudoternary system was characterized by SAXS technique, and the influence of microstructure on the catalytic performance of solubilized laccase was also explored. As the mass ratio of HIL to water increases, the microdomain size of the system decreases, and the catalytic efficiency (kcat/Km) of laccase also decreases. When the surfactant content gradually increases, the microdomain size of the system changes little, but its interfacial rigidity increases, and also the interaction between the interface and the solubilized enzyme increases accordingly, resulting in a decrease in the kcat/Km of the solubilized laccase. The variation of temperature over 35 °C–55 °C has little effect on the microdomain size of the system, but it has marked effect on the kcat/Km of the solubilized laccase. The optimal catalytic efficiency of laccase in the present microemulsion is estimated to be ca. 50 °C, which is significantly higher than that (40 °C) in the aqueous medium system, indicating that the bicontinuous microstructure in the system is helpful to improve the thermal stability of laccase. The present study is helpful for the rational formulation of laccase-compatible anionic surfactant-stabilized hydrophobic ionic liquid-based bicontinuous microemulsions, which is suitable for template-assisted biosynthesis of conducting polymers.

Phase Behavior of the Anionic Surfactant [Bmim][AOT]-Stabilized Hydrophobic Ionic Liquid-Based Microemulsions and the Effect of n-Alcohols

In this work, the fishlike phase diagram of the H2O/[Bmim][AOT]/[Bmim][PF6]/n-alcohol as a function of temperature (T) and the mass fraction of [Bmim][AOT] (with or without n-alcohol) in the total mixture (γ) has been observed for the first time at several mass ratios of [Bmim][PF6] to H2O (α) and with different n-alcohols. The larger area of the three-phase region occurs at α ≤ 0.500, and the resulting fish shapes are similar to each other. For a given α, a temperature scan (from lower to higher) at several γ values reveals that the present system forms an upper phase microemulsion first and then a lower phase microemulsion. The formation of hydrophobic ionic liquid-in-water (HIL/W) microemulsion at low temperature and water-in-hydrophobic ionic liquid (W/HIL) microemulsion at high temperature was confirmed by dynamic light scattering and small-angle X-ray scattering techniques. Here, the phase sequence that occurred during the temperature scan is opposite to that of a classic H2O/NaAOT/oil system. At th...

Polymerization of alkyl methacrylate nanoemulsions made by the phase inversion temperature method

The polymerization of several alkyl methacrylates in nanoemulsions made by the phase inversion temperature method is presented here. The temperature versus surfactant concentration fish-like phase diagrams for a fixed mixture of alkyl methacrylate/squalane (SQ) of 95/5 w/w, Brij 56 and water were elaborated. Reaction rates were extremely fast (ca. 100% conversion in less than 3 min), and only two reaction rate intervals were observed, which is typical of nanoemulsion polymerization. It suggests that chain transfer to monomer is the main termination mechanism. The addition of squalane inhibits monomer diffusion from small droplets to larger ones and prevents the diffusion of monomer from non-reacting droplets to reacting ones, which guarantees that each monomer droplet acted as a nanoreactor. Polymer particles have similar size than the original nanoemulsion droplets indicating that the nanodroplets act as templates for the formation of the polymer nanoparticles. Reaction rates, as well as kinetics and nanoparticle characterizations by quasielastic light scattering (QLS), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), are reported. Spheroidal nanoparticles with similar sizes and narrow distribution were observed by TEM for poly(ethyl methacrylate), poly(butyl methacrylate), and poly(hexyl methacrylate). The large molar masses and the narrow molar mass distributions were obtained by gel permeation chromatography.

Additive Effects on the Phase Behavior of Cationic Surfactant ([C16mim]Br) Stabilized Hydrophobic Ionic Liquid Based Middle-Phase Microemulsions

The e-β fishlike phase diagram of the system [C16mim]Br/[Omim]Tf2N/water was constructed in the presence of different additives (alcohol and inorganic salt). From the diagram some additive-dependent characteristic physicochemical parameters were obtained. Results show that with the increase of the alkyl chain length of alcohols, the solubility of the alcohol in [Omim]Tf2N, and the optimum solubilization parameter (SP*) decrease, while the maximum alcohol width (△e) for the phase inversion and the mass fraction of the alcohol in the balanced interfacial film (Ain) increase. For inorganic salts, an increase in [NaCl], or an increase of the radius of halides (X–) at constant [NaX], or the substitution of the divalent anion SO42– by the same molar concentration of monovalent anion Cl– makes both SP* and △e increase, but Ain decrease. Overall, the alcohol effect on the phase behavior of the microemulsion is greater than the salt effect, and the composition effect of an inorganic salt is greater than the concen...

The influence of alkyl polyglucosides (and highly ethoxylated alcohol boosters) on the phase behavior of a water/toluene/technical alkyl polyethoxylate microemulsion system

The influence of additives (alkyl polyglucoside, Glucopon 600 CS UP and alcohol ethoxylate C18E100) on the behavior of the water/toluene/Lutensol ON 50 (technical oxoalcohol, i-C10E5) microemulsion system as a function of temperature and composition has been investigated. The phase behavior of the microemulsions was determined by vertical sections through the Gibbs phase prism (fish-like phase diagrams). Alkyl polyglucoside shifts the one phase region to lower temperatures compared with water/toluene/Lutensol ON 50 mixtures. This is contrary to the expectation, considering the extreme hydrophilic nature of the sugar headgroup. The addition of hydrophilic alcohol ethoxylate (C18E100) to the water/toluene/Lutensol ON 50 system increases the solubilization capacity of the surfactant, even if the co-surfactant is used in small quantities, and shifts the one-phase region to higher temperature by a few degrees Celsius.

Application of ε-β fishlike phase diagrams on the microemulsion solubilizations of dense nonaqueous phase liquids

The solubilizations of dense nonaqueous phase liquids trichloroethylene (TCE), carbon tetrachloride (CCl4), 1,2-dichloroethane (DCE) and tetrachloroethene (PCE) in microemulsions containing mixed surfactants 1- dodecyl-3-methylimidazolium bromide (C12mimBr) and sodium lauryl sulfate (SLS), were studied by application of the ε-β fishlike phase diagram approach. It was found that the three-phase microemulsions would form at two XC12mimBr ranges of 0.0–0.1 and 0.8–1.0. Compared to the microemulsions containing single surfactant C12mimBr or SLS, the mixed C12mimBr-SLS microemulsions have lower solubility of the alcohol (εB) and lower mass fraction of the alcohol in the interfacial layer (AS), but higher solubilization parameter (SP*) values.The order of magnitude for the solubilization ability of the chlorohydrocarbons in the C12mimBr-SLS mixed (XC12mimBr= 0.8) microemulsion systems is: TCE > CCl4> PCE > DCE. This is consistent with the results of the literature.As the mass fraction values of oil in oil-water mixture (α) increase, εB and AS decrease, while SP* increases. The effects of both NaCl contents (w) and temperatures (T) on the physicochemical parameters of the microemulsions were also investigated. As the NaCl contents and the temperatures increase, the solubilization ability of the microemulsions increases.

Compositions and Physicochemical Properties of Tween Type Surfactants-Based Microemulsions

The compositions and physicochemical properties of the microemulsion systems consisting of Tween type surfactant (Tween 20, Tween 60, Tween 80)/butan-1-ol/dodecane/brine have been studied using ϵ-β fishlike phase diagram. From the ϵ-β fishlike phase diagram, solubility of the alcohol, composition of the interfacial layer, and solubilization ability of the microemulsion systems have been studied. The solubilization parameters of the microemulsion systems, SP* were in the order of magnitude Tween 60>Tween 80>Tween 20. The effects of different oils, alcohols, salinities and temperatures on the compositions and physicochemical properties have been investigated. The solubilization ability of the microemulsion systems increases with increasing salinities or decreasing temperatures. The effects of alcohols and alkanes display opposite patterns of change. By increasing the carbon chain length of the alkanol molecules, or decreasing the carbon chain length of the alkane molecules, the solubilization ability increases.

Middle-Phase Microemulsions Formed by n-Dodecyl Polyglucoside and Lauric-N-methylglucamide

The three-phase behaviors for the quaternary system of n-dodecyl polyglucoside or lauric-N-methylglucamide (MEGA-12)/n-alcohol/alkane/water have been studied with ϵ-β fishlike phase diagram. The increase of ϵ at constant β causes a series of phase inversions Winsor I(2) → III(3) → II . The physicochemical parameters, such as the mass fraction of n-butanol in the hydrophile-lipophile balanced interfacial layer (AS), the coordinates of the start and end points of the middle-phase microemulsion, and the solubilities of surfactant and n-butanol in alkane phase were calculated. The effects of different oils and aqueous media on the phase behavior, the composition of the interfacial layer, and the solubilizing power were investigated. It was found that the oil with small molecular volume increases the solubilizing power. In inorganic salt (NaCl) and acid (HCl) solutions, less n-butanol is needed than that in alkali (NaOH) solution to form middle- and single-phase microemulsions. The middle-phase microemulsions formed by n-dodecyl polyglucoside and lauric-N-methylglucamide were compared.

Effect of Inorganic Salts on the Phase Behavior of Microemulsion Systems Containing Sodium Dodecyl Sulfate

The effect of different inorganic salts on the phase behavior of the microemulsion systems comprising of SDS/aliphatic acid or alcohol/alkane/aqueous salt has been studied with an ϵ-β fishlike phase diagram method. The related physicochemical parameters, such as the solubility of the acid (alcohol) (ϵ B ), the composition of the interfacial layer (A S ), the mass fraction of the acid (alcohol) and surfactant contained in the interfacial layer in the whole system (ϵ i and β i ), and the optimum solubilization ability (SP*) of the microemulsion systems were calculated and discussed. As the concentration of salt (CaCl2) increases, the solubilization ability of the system would decrease for the aliphatic acid-based system, but would increase for the alcohol-based system. In the aliphatic acid-based and the alcohol-based microemulsion systems, the solubilization ability (SP*) of the microemulsion system was in the same salt order MgCl2>CaCl2∼SrCl2 and Ca (NO3)2>CaBr2>CaCl2.

Effect of the Composition of Mixed Oils on the Phase Behavior and Solubilization Ability of Microemulsion Systems

The phase behavior and the solubilization ability of the microemulsion systems containing mixed oils: sodium lauryl sulfate (SDS) + butan-1-ol + oil mixture (hexane + decane, hexane + cyclohexane, hexane + methylbenzene, methylbenzene + decane, methylbenzene + cyclohexane and methylbenzene + tetrachloroethene) + NaCl aqueous solution were studied using the e–β fishlike phase diagram method. The synergism in the solubilization ability was observed in the microemulsion systems containing mixtures of methylbenzene + hexane, methylbenzene + cyclohexane, and methylbenzene + tetrachloroethene, respectively. The solubility of the alcohol in the oil and aqueous phases and the composition of the interfacial layer in the microemulsion systems containing oil mixtures were also investigated.

Synergetic effect of cationic surfactive ionic liquid C 12mimBr and anionic surfactant SDBS on the phase behavior and solubilization of microemulsions

Synergistic effect of the surfactant mixture of ionic liquid 1-dodecyl-3-methylimidazolium bromide (C 12mimBr) and sodium dodecyl benzene sulfonate (SDBS) on the phase behavior and the solubilization ability of the microemulsion systems was studied with ɛ– β fishlike phase diagrams. The middle-phase microemulsion appears at the range of the mole ratios of C 12mimBr to SDBS 0–0.1 and 0.7–1.0. The solubilization ability (SP*) of the mixed surfactant based microemulsion systems increased markedly compared to the pure C 12mimBr or SDBS-based microemulsion systems. The mixture of C 12mimBr and SDBS also shows preferable synergism in the solubility of the alcohol and the composition of the interfacial layer. The effects of alcohols, alkanes and NaCl concentrations on the ɛ– β fishlike phase diagrams of C 12mimBr/SDBS (molar ratio = 8:2)/alcohol/alkane/brine microemulsion systems were also investigated.

Effect of Oil/Water Ratios on the Phase Behavior and the Solubilization Ability of Microemulsion Systems Containing Sodium Dodecyl Sulfate

An α–e–β fish-like phase diagram of three phase microemulsions was proposed and used to investigate the phase behavior of the microemulsion systems sodium dodecyl sulfate (SDS)/alcohol/oil/water at various oil/water ratios. Related physicochemical properties of the microemulsion systems were calculated. As the oil/water mass ratio increases, the solubility (e B) of the alcohol increases, while both the mass fraction of alcohol in the interfacial layer (A S) and the solubilization ability (SP ∗) decrease. The effect of oils on the properties of the microemulsion systems was investigated.

Studies in the phase behavior of the microemulsions formed by mixed cationic and nonionic surfactants

The middle-phase behavior for the systems of cetyltrimethylammonium bromide (CTAB)/poly-ethyleneglycol-9-monododecyl ether (AEO9)/alcohol/oil/brine and CTAB/octylphenolpolyoxyethylene-10-ether (Triton X-100)/alcohol/oil/brine have been studied with ɛ-β fishlike phase diagram method. The interfacial layer composition was determined, and some significant physicochemical parameters are derived from the hydrophilic-lipophilic balance plane equation. The effects of different alcohols, oils, temperature and inorganic salt (NaCl) on the middle-phase behavior of microemulsion formed by composite CTAB/AEO9 systems were also investigated systematically. The effects of different factors on the phase behavior of microemulsions formed by CTAB/AEO9 and CTAB/TX-100 systems were compared. The results suggest that the solubilization of CTAB/AEO9 microemulsion is higher than that of CTAB/TX-100 system under the same conditions.

Phase Behavior of the Microemulsion Systems Containing Alkyl Polyglucoside and Hexadecyl-trimethyl-ammonium Bromide

The composition and the solubilization ability of the microemulsion systems containing mixed surfactants of alkyl polyglucoside (APG) and hexadecyl-trimethyl-ammonium bromide (CTAB) were studied by using the ε∼β fishlike phase diagram method. Synergistic effect in terms of the composition of the interfacial layer and the solubilization ability was observed in microemulsion systems APG + CTAB + alcohol + alkane + NaCl aqueous solution. In the interfacial layer of the microemulsions the number of surfactant molecules notably decreases, resulting in the significant improvement in the solubilization ability of the system. The effects of the carbon chain length of the alkanes and salinity on the ε∼β fishlike phase diagrams of APG (CTAB) + alcohol + alkane + NaCl solution microemulsion systems were also discussed.

Phase Behaviour of the Microemulsion Systems Formed by the Composite Surfactants Alkyl Polyglucoside and Sodium Dodecyl Sulfate

Abstract The phase behavior of microemulsions containing composite surfactants of non-ionic alkyl polyglucoside and anionic sodium dodecyl sulfate was studied by the ∊-β fishlike phase diagram method. In microemulsion systems APG(SDS)/alcohol/alkane/water, there exists an obvious synergistic effect in terms of the composition of the interfacial layer and the solubilization ability. In the interfacial layer the number of surfactant and alcohol molecules notably decrease, resulting in a significant improvement in the solubilization ability of the system. The effects of alcohols, alkanes and salinity on the ∊-β fishlike phase diagrams of APG/SDS/alcohol/alkane/brine microemulsion systems were also discussed.

Effects of Isomeric Alcohols and Oils on the Properties of the Microemulsion Systems Formed by Alkyl Phenol Poly(oxyethylene ether)

The effects of three isomeric alcohols, butan-1-ol, butan-2-ol, and 2-methyl-propan-2-ol, on the phase behavior and physicochemical properties of the pseudoquaternary microemulsion systems alkyl phenol poly(oxyethylene ether) (OP) + butan-1-ol (butan-2-ol, 2-methyl-propan-2-ol) + hexane (heptane, octane) + 0.05 NaCl solution were investigated with an ε−β fishlike phase diagram method. The properties studied include the composition of the interfacial layer AS, the solubilities of alcohols AO,W, and the solubilization ability SP* of the microemulsion systems. With the branched chain increasing, the AS and AO,W values are in the order: butan-1-ol < butan-2-ol < 2-methyl-propan-2-ol, but the SP* values are in the inverse order. These results were discussed. The effects of oils on the phase behavior and above physicochemical properties were also investigated.