Single Surfactant Systems Research Articles

Enhanced recovery of a viscous oil with a novel surfactant

Steam-based recovery methods are usually employed to recover heavy and viscous oils, but they are not efficient in deep and thin oil reservoirs. Chemical flooding is studied here to improve recovery of a viscous oil (about 300 cp at the reservoir temperature of 70 °C) from a thin, high permeability, unconsolidated reservoir. A large number of novel short-hydrophobe based surfactants were designed and synthesized. As these surfactants do not require expensive aliphatic alcohols for their synthesis, they are likely to be less costly than conventional anionic surfactants. Only phenol hydrophobe-based non-ionic surfactants with varying number of propylene oxide (PO) and ethylene oxide (EO) groups are discussed in this paper. These surfactant molecules were investigated for their aqueous stability, interfacial tensions (IFT) with a viscous crude oil, and oil recovery from sandpack or sandstone cores. Surfactant phase behavior experiments with viscous crude oil showed low IFT (not ultralow) for single surfactant systems. A chemical formulation using only a single surfactant (Phenol-7PO-15EO) was chosen for corefloods in sandpacks and sandstone cores. Water flood recovered about half of the original oil and reduced the oil saturation to about 48% in the high permeability sandpacks. The tertiary surfactant polymer flood with Phenol-7PO-15EO increased the cumulative recovery to 99% for sandpacks. The oil recovery was insensitive to injection brine salinity in the range studied. As the permeability decreased, the tertiary oil recovery decreased. Surfactant-polymer formulations with this surfactant can be recommended for high permeability sandstone reservoirs with viscous oils, but not for sub-Darcy sandstones.

Fine-tuned order-order phase transitions in giant surfactants via interfacial engineering

Thermotropic order-order phase transitions (OOTs) in block copolymers are not commonly observed in the strong segregation region. Phase separation of giant surfactants composed of hydrophilic molecular nanoparticles (MNPs) as heads and hydrophobic flexible polymer chains as tails occurs generally in the strong segregation region. By introducing a rigid molecular segment at the junction point of the giant surfactants, the interface between the MNPs and polymer tails could be delicately manipulated, resulting in the occurrence of thermotropic OOTs that are sensitively dependent on the properties of those junction segments. For samples with hydrophilic junction segments, no thermal-induced OOT has been observed. However, for samples with hydrophobic junction segments, complicated thermotropic OOTs between as many as four different ordered phases in a single giant surfactant system, from lamellae (LAM) to hexagonally perforated layer structure (HPL), double gyroids (DG), and finally to hexagonally packed cylinders (HEX), have been observed with increasing temperature. These results demonstrated that interfacial engineering could be used to regulate the self-assemble behavior of macromolecules at the nanometer scales.

CdSe Quantum Dots to Quantum Rods: Transition Studies and Evaluation of Sensitivity as Transducers for Biosensing Glucose

Background: The estimation of glucose level in the blood serum, has been widely used as a clinical indicator of diabetes. Optical and electrochemical sensing of glucose widely uses Glucose Oxidase (GOD) enzyme, as the catalyst for glucose oxidation, which releases hydrogen peroxide (H2O2). Optical biosensors are superior to their electrochemical counter-parts as they are resistant to electromagnetic interference, easier to fabricate into a microdevice and require low power supply. The quantum-dot-based biosensors work on the phenomenon of fluorescence quenching following the release of H2O2. Methods: The CdSe nanoparticles are prepared in two series by room-temperature microemulsion method. In series A, only AOT surfactant is used to synthesize spherical CdSe nanoparticles. In series B, the mixed surfactant system of AOT and lecithin is used to synthesize anisotropic CdSe. The morphology and crystallography is studied as the CdSe shape changes from spherical to rod-like. As the CdSe nanoparticles are studied from spherical to rod-like morphology, the transducing sensitivity of these nanoparticles is evaluated with respect to glucose biosensing. The effects of size and shape are studied, based on the fluorescence quenching by H2O2 solutions. The sensitivity of proposed nanoparticles, is evaluated as a function of size, shape, surface area and number concentration of CdSe nanoparticles. Results: The spherical CdSe nanoparticles are found to increase in size as R(water-to-surfactant ratio) is increased from 4 to 12, in series A. Also, the aspect ratio of CdSe nanoparticle is found to increase from 4.2 to 12.8 as the ratio of AOT to lecithin is varied from 1:0.5 to 1:3. The decrease in sensitivity index is seen with increasing surface area for both series A and B. The sensitivity is decreasing again with increasing maximum dimension of the CdSe nanoparticle in the dispersion. While the trend is reverse in case of the number concentration for CdSe nanoparticles synthesized in series B. Conclusion: From the data presented, it can be safely concluded that the sensitivity indices for series A are better than those for series B, for the same values of a) the total surface area of CdSe nanoparticles, b) total number concentration, and c) maximum dimension of CdSe nanoparticles. Also, the single surfactant system (series A) is simple, cheaper and more reproducible to synthesize the CdSe nanosheres, as compared with the mixed surfactant system forming CdSe quantum rods (series B). With these points, it is reasonable to report that CdSe spherical QDs are better candidates for glucose biosensing, as compared to CdSe quantum rods.

Dilational Viscoelastic Properties of Water–Fuel Interfaces in Single and Binary Surfactant Systems

The interfacial rheology of a surfactant film surrounding a water-in-oil emulsion influences the stability of the emulsion significantly. In this research, we chose monoolein of molecular weight of...

Foaming in aqueous solutions of mixtures of a zwitterionic and a cationic surfactant in presence of an electrolyte

This paper reports the foamability and the stability of foams of aqueous solutions of mixed systems of a zwitterionic surfactant (i.e. N-Dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and a cationic surfactant (i.e. cetyltrimethylammonium bromide) in the presence of NaCl. The synergism between the surfactants was examined by measuring the surface tension for various compositions of the surfactants and the salt. The interaction occurring between the surfactant molecules adsorbed at the air–water interface influenced the monolayer properties. The mixed surfactant system produced a significant decrease in surface tension as compared to the single surfactant systems. In the presence of salt, the surface tension reduction was larger. The interaction among the surfactant molecules at the air–water interface and the same in the mixed micelles was quantified by the respective interaction parameters. The blender test was used to investigate the foamability and foam stability. The foamability studies showed synergistic behavior inasmuch as higher foam volumes were generated in the mixed surfactant systems as compared to the single surfactant systems. The addition of salt had a remarkable effect on the foaming properties of the mixed surfactant systems. It increased the stability of foams significantly. The synergism between the surfactant molecules had a notable influence on the zeta potential at the air–water interface.

Exploring the Potential Application of Palm Methyl Ester Sulfonate as an Interfacial Tension Reducing Surfactant for Chemical Enhanced Oil Recovery

As the petroleum industry is facing challenges to add more oil reserves in their book, greater emphasis has been placed on improving the ultimate recovery factor for oilfields. When the recovery from primary and secondary methods could not be improved further, enhanced oil recovery (EOR) generally will be sought as the last option. One of the techniques applied in EOR is known as surfactant flooding. Though surfactants are very effective for the incremental oil recovery, there are implications during the post-flooding process. EOR surfactants that derived from petrochemicals generally display negative effects towards the marine ecosystem. This initial study aims to evaluate the potential application of palm oil based methyl ester sulfonate (MES) as a possible candidate for EOR application. Three qualitative and quantitative tests were performed on MES to evaluate its properties and capabilities for application in a specific offshore field. The results obtained from the qualitative compatibility and stability tests show that this anionic surfactant has great stability and compatibility with the brine solution as there are no visible signs of precipitation formation. However, the qualitative phase behavior test results indicated that the surfactant solution although has the ability to react with the crude oil but not at the required micro-emulsion state. In addition, the quantitative interfacial tension (IFT) test results also verified and supported the phase behavior test results where the strength of the MES was not adequate as a single surfactant system to achieve the ultra-low IFT state.

Solubilization of polycyclic aromatic hydrocarbons by novel ester-bonded Gemini prolinol-based surfactant and its binary mixtures with conventional surfactants

Aqueous interactions of a novel ester-bonded Gemini prolinol-based surfactant, 2,2′-((adipoylbis(oxy))bis(methylene))bis(1-dodecyl-1-methylpyrrolidin-1-ium) bromide C12-6-C12PB, with dodecyl sodium sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB), or cetyltrimethyl ammonium bromide (CTAB) were studied using conductomeric measurement. The experimental critical micelle concentration (CMC) was lower than the ideal CMC, and the negative interaction parameters indicate that there is a synergistic interaction between the surfactants in the binary solution. The solubilization capacities of single and binary surfactant systems towards polycyclic aromatic hydrocarbons (PAHs) (i.e., naphthalene, anthracene, and pyrene) were evaluated and are discussed in terms of the molar solubilization ratio (MSR), micelle-water partition coefficient (Km), and free energy of solubilization (). C12-6-C12PB and SDS respectively had the minimum and maximum MSR when presented individually in the solution. The MSR values in the binary system are greater than those in the single surfactant system, and this indicates that synergism in a mixed system enhances PAH solubility. With a molar ratio of 0.7:0.3, C12-6-C12PB/SDS had a relatively greater solubilization capacity for PAHs because of large aggregates. The negative value of indicates the spontaneity of the solubilization process.

Mixed surfactant enabled EVA emulsion for PPD applications

PPD emulsion product is advantageous for use in sub-ambient temperature as it improve the physical handling characteristic compared to traditional product. However, existing PPD emulsion system is solely implementing a single anionic surfactant system which leads instability towards a series of temperature changes. Therefore, mixed surfactant (anionic and non-ionic) surfactant was introduced to overcome this problem. Through this research, sodium dodecyl sulfate (SDS) act as anionic surfactant and Tween 80 used as non-ionic surfactant in this study. The stability of an emulsion was identified through particle size and zeta potential. For the mixed surfactant composition, the result show the presence of SDS content contributes in reduction on particle size. Furthermore, the study on effectiveness of surfactant on EVA emulsion was evaluated. The result indicates with present of surfactant, interfacial surface tension was reduced. The freezing point and pour point depressant test of the EVA emulsion was evaluated. Present of non-ionic surfactant help in stability and flow-respond at low temperature. Mixed surfactant system provides sufficient protection from droplet size growth caused by the temperature changes which eventually leads to instability.

Predictive Modeling of Micellar Solubilization by Single and Mixed Nonionic Surfactants

Micellar solubilization is an important concept in the delivery of poorly water-soluble drugs. The rational selection of the type and the amount of surfactant to be incorporated in a formulation require comprehensive solubility studies. These studies are time and material demanding, both of which are scarce, especially during late discovery and early development stages. We hypothesized that, if the solubilization mechanism or molecular interaction is similar, the solubilization capacity ratio (a newly defined parameter) is dictated by micellar structures, independent of drugs. We tested this hypothesis by performing solubility studies using 8 commonly used nonionic surfactants and 17 insoluble compounds with diverse characteristics. The results show a striking constant solubilization capacity ratio among the 8 nonionic surfactants, which allow us to develop predictive solubility models for both single and mixed surfactant systems. The vast majority of the predicted solubility values, using our developed models, fall within 2-fold of the experimentally determined values with high correlation coefficients. As expected, systems involving ionic surfactant sodium dodecyl sulfate, used as a negative control, do not follow this trend. Deviations from the model, observed in this study or envisioned, were discussed. In conclusion, we have established predictive models that are capable of predicting solubility in a wide range of nonionic micellar solutions with only 1 experimental measurement. The application of such a model will significantly reduce resource and greatly enhance drug product development efficiency.

Micellization of Anionic Sulfonate Gemini Surfactants and Their Interactions With Anionic Polyacrylamide

AbstractAnionic sulfonate gemini surfactants 8‐s‐8(SO3)2 and 12‐s‐12(SO3)2 (s = 3, 6) were synthesized, and their micellization in aqueous solution at 25.0 °C and pH 9 was investigated. The results show that the critical micelle concentrations (CMC) of 8‐s‐8(SO3)2 are more than 2 orders of magnitude larger than those of 12‐s‐12(SO3)2, but the spacer length has a relatively small impact on the CMC. Moreover, the interactions of n‐s‐n(SO3)2 (n = 8, 12; s = 3, 6) with anionic polyacrylamide (PAM) at 25.0 °C and pH 9 were investigated using surface tensiometry, rheolgy, and scanning electron microscopy (SEM). The results indicate that the surface tension and rheological properties of PAM depend on the concentration of n‐s‐n(SO3)2. Below the critical aggregation concentration of C1, surface tension is sharply reduced, the surface tension of n‐s‐n(SO3)2/PAM is lower than n‐s‐n(SO3)2 alone, but viscosity is almost unchanged with increasing Cn‐s‐n(SO3)2. Above C1, surface tension reduces very slowly until the saturated concentration of C2 is reached. Above C2, surface tension rapidly reduces until CM is attained, suggesting free n‐s‐n(SO3)2 micelles begin to form. In the region of C1–CM, the viscosity significantly increases. Above CM, surface tension is basically unchanged and these curves coincide with those of the single surfactant system. Moreover, the viscosity is almost constant. The SEM images indicate that fibrous aggregates are formed below C1, then transformed into multilayer fibrous aggregates above C1, and further into fiber‐braided‐structured and spider‐web‐structured aggregates above CM. The variation of viscosity is closely associated with the transformation of aggregates.

Porous microspheres of polyaniline, poly(o-toluidine), and poly(m-toluidine) prepared from double emulsions stabilized by toluidine isomers as the single surfactant

HypothesisPorous spheres of the conducting polymer polyaniline (PANI) and its derivatives are promising materials for use as functional encapsulants for payload delivery and catalyst supports. Stable water-in-oil-in water (W/O/W) double emulsions can be used to obtain this morphology, but typically require multiple surfactants and stabilizers. A single surfactant system that uses a small amphiphilic molecule is desirable, as it can simplify the method, improve its efficiency, and reduce its cost. ExperimentsGranular poly(o-toluidine) (POT) was transformed into porous microspheres when ammonium hydroxide was added to an aqueous acidic dispersion containing the preformed polymer and amphiphilic o-toluidine (OT). The OT, POT, and ammonium hydroxide concentrations were varied to understand the formation mechanism. Conditions were optimized to obtain a narrowed size distribution. FindingsThe rapid change from acidic to alkaline surroundings produces a W/O/W double emulsion from POT and OT over a relatively narrow concentration range. Spheres form when POT dissolves in immiscible OT droplets, and entrapped water droplets form the pores. OT serves as the single amphiphilic surfactant and dissolved POT serves as a hydrophobic co-stabilizer. o-Toluidine, m-toluidine, or p-toluidine could be used as the single surfactant to obtain porous spheres from preformed POT, PANI and poly(m-toluidine).

Model-Free Analysis of Critical Micellar Concentrations for Detecting Demixing in Surfactant Mixtures.

Aqueous mixtures of two or more surfactants are often employed for research or industrial purposes because such mixtures offer advantages over single-surfactant systems. This is particularly true for mixtures of fluorocarbon (FC) and hydrocarbon (HC) surfactants, which display a broad range of mutual miscibilities in mixed micelles. Unfortunately, the prediction and even the experimental elucidation of the micellar mixing behavior of surfactant mixtures remain challenging, as evidenced by conflicting results and conclusions derived from diverse, and often complex, mixing models. One of the most intriguing questions is whether certain combinations of FC and HC surfactants form only one type of mixed micelle or rather demix into two micelle populations, namely, FC-rich and HC-rich ones. Here, we demonstrate a novel approach to the model-free analysis of critical micellar concentrations (CMCs) of surfactant mixtures that is based on a fit of the experimental data with cubic splines using a stringent thermodynamic criterion for mixing. As a proof of principle, we analyze CMC values determined by isothermal titration calorimetry and confirm the conclusions with the aid of combined 1H- and 19F-NMR spectroscopy. Specifically, we show that aqueous mixtures of an FC maltoside and an HC maltoside conform with the assumption of only one type of micelle regardless of the mixing ratio, whereas combining the same FC surfactant with an HC surfactant carrying a zwitterionic phosphocholine headgroup gives rise to two coexisting micelle populations at high mole fractions of the FC maltoside.

EFFECTS OF NANOPARTICLES AND SURFACTANT CHARGE GROUPS ON THE PROPERTIES OF VES GEL

Abstract - Application of viscoelastic surfactant (VES) fluids in hydraulic fracturing is still in the development stage, though shear thinning behavior and water solubility are the two important characteristics behind increasing interest in their use in fracturing jobs. Effects of ionic characteristics and the concentration of different surfactants on the rheological properties of VES fluid have been investigated in detail in the present study for a number of surfactant systems. Phase behavior of the system was studied and the gel region was identified. Effects of alkali on the viscosity, thermal stability, and miscibility (in water) of the developed gel were also investigated. Dynamic rheological study was carried out to determine the storage modulus and loss modulus. This study shows that mixed anionic-anionic system gives improved rheology compared to single anionic and mixed anionic-zwitterionic surfactant systems. Keywords : Hydraulic Fracturing; Viscoelastic gel; Surfactant based fluids; Rheology; Nanoparticles.

Investigation of the physicochemical and biological properties of proline‐based surfactants in single and mixed surfactant systems

AbstractA series of surfactants derived from l‐Proline, the free amine esters, the ester hydrochlorides and the quaternary ammonium compounds with varying chain lengths (C8–C14) were synthesised. The physicochemical and biological properties were determined in both single and sodium dodecyl sulphate (SDS) mixed systems with a view of enhancing the properties of the individual surfactants as potential ingredients in detergent formulations. The mode of action of the proline surfactants were investigated by their ability to form mixed micelles with the phospholipid 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphatidylcholine (DMPC). The presence of a quaternary ammonium moiety and an increase in alkyl chain length were found to enhance the antibacterial activity of the proline QUAT derivatives. The SDS‐C14 QUAT mixed system displayed good antibacterial activity with optimum activity at mole fractions αQUAT: 0.4 and 0.6. The antibacterial activity of the mixed system was found to be governed by the monomers rather than the micelles. The SDS‐C14 QUAT mixed system also showed moderate irritancy which makes them potential candidates as detergents.

Comparative study of the production of rhamnolipid biosurfactants by B. thailandensis E264 and P. aeruginosa ATCC 9027 using foam fractionation

Biosurfactants are surface-active agents that are produced by a variety of microorganisms including yeasts, filamentous fungi and bacteria. In this work, we report on the ability of Pseudomonas aeruginosa ATCC 9027 and Burkholderia thailandensis E264 to produce rhamnolipids via a 10-L bioreactor and their recovery through foam fractionation studies in a continuous stripping mode. The recovery of Rha-C10-C10 (mono-rhamnolipids) produced by P. aeruginosa ATCC 9027 increased (from 6% to 96%), whilst the enrichment decreased (from 2.9 to 1.2) with the increasing airflow rate. These results are consistent with foam fractionation of a single surfactant system with stable foam. The recovery and enrichment of Rha-Rha-C14-C14 (di-rhamnolipids) produced by B. thailandensis E264 (and an unknown molecule) in a single-component system were found to display different characteristics. Both recovery and enrichment were found to decrease with the airflow rate. It is postulated that a competitive adsorption process could occur between the smaller molecule identified by electrospray ionisation–mass spectrometry (ESI–MS) and Rha-Rha-C14-C14.

Interfacial tension of oil/water emulsions with mixed non-ionic surfactants: comparison between experiments and molecular simulations

Smaller Span molecules occupy the free spaces between bulkier Tween molecules thus lowering interfacial tension as compared to those obtained for single surfactant systems.

Surfactant effect on the physicochemical characteristics of γ-oryanol-containing solid lipid nanoparticles

Abstract Surfactants employed in production of solid lipid nanoparticles (SLNs) play a major role on physical stability of nanoparticles, and the extent of drug dissolution and permeability into cells. In this study, cationic (cetyl pyridinium chloride), anionic (sodium dodecyl sulfate) and non-ionic (Tween 80) surfactants, as well as its combinations, were employed to formulate compritol based SLNs using γ-oryzanol as a model drug. The physicochemical properties of drug-loaded SLNs are influenced by the surfactant composition systems. Surfactant blend systems gave SLNs with superior stability compared with single surfactant systems due to enhanced incorporation of the drug within the solid lipid matrix. This may be due to synergic effects arising from electrostatic repulsion of the surfactant charges (ionic), the steric hindrance of surfactant structure (non-ionic), and ion-pairing effects between cationic and anionic ones. The cytotoxicity results demonstrated that positively charged SLNs can be uptaken into cells to a high extent. Nevertheless, the mixed surfactant systems (cationic/non-ionic and cationic/anionic/non-ionic), have remarkable advantages providing SLNs with high cell internalization capability, however, low cytotoxicity. This systematic investigation may give an insight into the practical integration of multi-surfactant systems to achieve non-toxic and highly effective drug delivery systems.

Solubilization of herbicides by single and mixed commercial surfactants

The solubilization capabilities of micellar solutions of three single surfactants, two alcohol alkoxylates B048 and B266, and the tallow alkyl ethoxylated amine ET15, and their equimolar mixed solutions toward the herbicides flurtamone (FL), metribuzin (MTZ) and mesotrione (MST) were investigated. The solubilization capacity was quantified in terms of the molar solubilization ratio (MSR), critical micellar concentration (CMC), micelle–water partition coefficient (Kmc), binding constant (K1), number of aggregation (Nagg) and Stern–Volmer constant (Ksv). The herbicides were greatly solubilized into different loci of the micelles: FL within the inner hydrophobic core, MST at the micelle/water interface and MTZ in the palisade region. Equimolar binary surfactant mixtures did not improve the solubilization of herbicides over those of single components, with the exception of MTZ by the B266/ET15 system which enhanced solubilization by 10–20%. This enhanced solubilization of MTZ was due to an increased number of micelles that arise from both the intermediate Nagg relative to that of the single surfactants and the lower CMC. The use of Ksv values was a better predictor of the solubilization of polar molecules within binary mixtures of these surfactants than the interaction parameter βM from regular solution theory (RST). The results herein suggest that the use of mixed surfactant systems for the solubilization of polar molecules in environmental remediation technologies may be very limited in scope, without clear advantages over the use of single surfactant systems.

Enhanced photodegradation of pentachlorophenol by single and mixed nonionic and anionic surfactants using graphene-TiO₂ as catalyst.

The photodegradation of pentachlorophenol (PCP) in a surfactant-containing (single and mixed) complex system using graphene-TiO2 (GT) as catalyst was investigated. The objective was to better understand the behavior of surfactants in a GT catalysis system for its possible use in remediation technology of soil contaminated by hydrophobic organic compounds (HOCs). In a single-surfactant system, surfactant molecules aggregated on GT via hydrogen bonding and electrostatic force; nonideal mixing between nonionic and anionic surfactants rendered GT surface with mixed admicelles in a mixed surfactant system. Both effects helped incorporating PCP molecules into surfactant aggregates on catalyst surface. Hence, the targeted pollutants were rendered easily available to photo-yielded oxidative radicals, and photodegradation efficiency was significantly enhanced. Finally, real soil washing-photocatalysis trials proved that anionic-nonionic mixed surfactant soil washing coupled with graphene-TiO2 photocatalysis can be one promising technology for HOC-polluted soil remediation.

Detergency of Vegetable Oils and Semi‐Solid Fats Using Microemulsion Mixtures of Anionic Extended Surfactants: The HLD Concept and Cold Water Applications

AbstractIn spite of the increasing interest in cold temperature detergency of vegetable oils and fats, very limited research has been published on this topic. Extended surfactants have recently been shown to produce very promising detergency with vegetable oils at ambient temperature. However, the excessive salinity requirement (4–14 %) for these surfactants has limited their use in practical applications. In this work, we investigated the mixture of a linear C10–18PO–2EO–NaSO4 extended surfactant and a hydrophobic twin‐tailed sodium dioctyl sulfosuccinate surfactant for cold temperature detergency of vegetable oils and semi‐solid fats. Four vegetable oils of varying melting points (from −10 to 28 °C) were studied, these were canola, jojoba, coconut and palm kernel oils. Anionic surfactant mixtures showed synergism in detergency performance compared to single surfactant systems. At temperatures above the melting point, greater than 90 % detergency was achieved at 0.5 % NaCl. While detergency performance decreased at temperatures below the melting point, it was still superior to that of a commercial detergent (up to 80 vs. 40 %). Further, results show that the experimental microemulsion phase behaviors correlated very well with predictions from the hydrophilic–lipophilic deviation concept.