Commercial Surfactants Research Articles

Universal and simple method for facile fabrication of sustainable high internal phase emulsions solely using meat protein particles with various pH values

High internal phase emulsions (HIPEs) have recently been investigated for applications in food areas: plant proteins, polysaccharides, and commercial surfactants have been used as emulsifiers, but meat proteins have rarely been reported as emulsifiers for HIPEs. In this report, we describe an outstanding HIPE stabilized solely by meat protein particles. The natural stabilizer was prepared by a one-pot centrifugation process (3000×g, 20 min), and the HIPEs were fabricated by a simple one-pot homogenization process (5000 rpm/min, 1 min). The meat proteins could form homogeneous and stable HIPEs in the continuous phase over a wide pH range of 3–11. In this state, the HIPEs exhibited excellent stability in three conditions: heat, freeze-thaw, and storage (60 days). Interestingly, these natural stabilizers were also perfect combinations of soybean oil, corn oil, sunflower oil, and n-hexane, and they exhibit the potential to act as nutrition delivery systems, animal fat replacements, partially hydrogenated oils, and other functional materials.

Cover Image, Volume 94, Issue 11

The cover image is based on the Research Article Trichloroethylene solubilization using a series of commercial biodegradable ethoxylated fatty alcohol surfactants by Javier I Garza‐Arévalo et al., DOI: 10.1002/jctb.5965.The image was prepared by the first author, Javier I. Garza‐Arévalo. image

Biotechnological potential of exopolysaccharide as a bioemulsifier produced by Rhizobium radiobacter CAS isolated from curd

Succinoglycan exopolysaccharide (EPS) from Rhizobium radiobacter CAS and its rheological behavior has been studied earlier. In present investigation the emulsifying potential of CAS EPS has been determined. CAS EPS concentration was optimized with hydrocarbons soybean oil and n-Hexane, whereas effect of pH (3.0–11.0), salinity, monovalent ions, divalent ion, (NaCl, KCl and MgCl2), freezing/thawing, temperature heating, emulsion stability and rheology on emulsifying activity (EA) was inspected using n-Hexane, paraffin oil, groundnut oil and soybean oil. CAS biopolymer represented superior emulsion stabilization ability (100%) under stress conditions and was highly tolerant to extreme pH, inorganic salts concentrations. Thermal stability of emulsions has found 100% at −20 °C–40 °C, whereas, at temperature 50 °C–120 °C high emulsion index (82.4–94.1% respectively) were recorded. Wetting filter paper test verified oil-in-water (o/w) type emulsion whereas rheological property showed pseudoplastic nature of emulsions. During stability of emulsions up to 30 days, some reduction of emulsification activity was observed for paraffin oil, however CAS hydrocolloid formed 100% emulsion index for n-Hexane, groundnut and soybean oils. These emulsifying and better hydrophilic physical properties make CAS hydrocolloid a prospective alternative to commercial biopolymers and chemical surfactants.

The synergistic effect of enzymatic detergents on biofilm cleaning from different surfaces

Biofilm growth is a significant source of contamination in the food industry. Enzymes are considered green countermeasures against biofilm formation in the food industry owing to their biodegradability and low toxicity. In this study, the synergistic effect of enzymes was studied against biofilm cleaning from hard surfaces. A mixed-microbial sample was sourced from a meat packaging line and biofilms were grown under high shear conditions on stainless steel and polyethylene surfaces. A model cleaning-in-place (CIP) parallel-plate flow chamber was used for firstly, the enzymatic cleaning and secondly, a disinfection step. The cleaning effectiveness was evaluated in response to different formulations containing non-foaming commercial surfactants among with amylase, protease and lipase at neutral pH. The formulation combining all three enzymes was the most effective, showing a synergy essential for the deformation of biofilm structure and consequently better disinfection of both material surfaces.

Drag Reduction by Wormlike Micelles of a Biodegradable and Non‐Biodegradable Surfactants

AbstractThis study describes the effects of wormlike micelles formed by the commercial surfactants tallowalkylamidopropyl dimethylamine oxide (Aromox APA‐TW) and oleyl methyl bis(2‐hydroxyethyl) ammonium chloride (Ethoquad O/12) as drag reducers. Ethoquad O/12 is immune to degradation by heat and microorganisms. Conversely, Aromox APA‐TW is biodegradable in the environment, and its susceptibility to heat‐induced degradation was previously assessed. This work considers the effects of temperature, salt, and time on the drag‐reduction capacity (in different Reynolds number) of wormlike micelles of these two surfactants. Wormlike micelles formed by Aromox APA‐TW are able to reduce drag at higher temperatures compared to wormlike micelles formed by Ethoquad O/12. However, Aromox APA‐TW can degrade after being heated to 80 °C and also after storage of the wormlike micelle solutions. Ethoquad O/12 does not undergo degradation after being heated or stored. These surfactants have the potential to be used as additives in industrial operations, as the wormlike micelles formed are able to reduce drag in systems with long pumping distances or recirculation, even in solutions with high salt concentrations (brine) and high temperatures.

Improved performance of immobilized TiO2 under visible light for the commercial surfactant degradation: Role of carbon doped TiO2 and anatase/rutile ratio

• The CDT (A/R)/GAC nanocomposite was synthesized using the sol–gel technique. • The band gap decreased from 3.17 eV to 2.72 eV after C doping. • The band gap decreased from 2.72 eV to 2.66 eV after temperature changing. • The effects of initial temperature and light intensity were studied. Nanoparticles of TiO 2 with different ratios of anatase (A)/rutile (R) phases were successfully synthesized via sol-gel method. Carbon-doped TiO 2 (CDT) was supported on the surfaces of granular activated carbon (GAC) for photocatalytic degradation and mineralization of the commercial nonylphenol (NP) surfactant under visible light irradiation. The physicochemical characteristics of the synthesized composites (TiO 2 , CDT, and CDT/GAC) were determined in detail by X-ray diffraction, scanning electron microscopy, elemental mapping, Brunauer–Emmett–Teller, UV–Vis absorption and PL spectra. The results indicated that the band gap decreased from 3.17 eV to 2.72 eV after C doping, and to 2.66 eV by changing the calcination temperature from 475 °C to 600 °C; the visible light absorption also increased. This study demonstrates that the CDT/GAC photocatalyst with an A (53.06)/R (46.94) ratio exhibited high degradation efficiency. COD and TOC removal of 99% and 89%, respectively, and 80% NP decrease within 60 min. The NP degradation increases with increasing temperature and light intensity. The Langmuir–Hinshelwood kinetic model fitted with the experimental data. In addition, it is reported that the synthesized photocatalyst became stable and highly active, even after five cycles. The results also showed that the values of the carbon oxidation state (COS) and the average oxidation state (AOS) were highly increased after the decomposition of NP by the Xenon/CDT (A/R)/GAC process over 3.37 and 3.87, respectively.

A comparative study of dynamic adsorption of anionic synthetic and nanocellulose-based surfactant in Malaysian reservoir

This project is aimed at studying the applicability of nanocellulose-based surfactant as a sustainable surfactant for enhanced oil recovery process (EOR) in Malaysia. Abundant biomass waste from palm oil industry in Malaysia is hard to be disposed of. Therefore, potential application of biomass in chemical EOR is an attractive alternative to minimize these problems. For this study, nanocellulose is synthesized from oil palm empty fruit bunch (OPEFB) and undergoes chemical modification for it to act like a surfactant. All methods and techniques in synthesizing nanocellulose and preparing nanocellulose-based surfactant are made inhouse. While waiting for the material preparation, adsorption study is carried out by using anionic synthetic surfactant. Characterization result shows the nanocellulose undergoes chemical modification successfully. The IFT results for the nanocellulose-based surfactants are also in a good and acceptable range, but there are some limitations in using nanocellulose-synthesized surfactant. The average particle size of nanocellulose is 283.5 µm which is larger than size of the reservoir pore throat. Dynamic adsorption cannot be performed as the large particle size of nanocellulose might plug the porous domains. Therefore, it is recommended to further improve the method of synthesizing nanocellulose from OPEFB because the nanocellulose-based surfactant is expected to have potential of lower adsorption in porous media once it becomes nanosized and due to its advantages such as being of lower cost and environmental friendly compared to other commercial surfactants.

Breaking water-in-oil emulsion of Northern Iraq’s crude oil using commercial polymers and surfactants

Water (W) and oil (O) normally mix during production and while passing through valves and pumps to form a persistent water-in-oil (W/O) emulsion, which is a serious restriction in oil production and transporting and refining processes. The objective of this work is to treat emulsions of two crude oil samples labeled KD1 and DGH2 using commercial polymers and surfactants which are also known as demulsifiers. Hydrophile–lipophile balance (HLB) in the demulsifier structure has demonstrated a great effect on breaking W/O emulsion. Emulsion breakers with low HLB value showed better reduction in the dynamic IFT, high diffusivity at the W/O interface, and accelerated coalescence of water droplets. Concomitantly, high emulsion temperatures were found to reduce the interfacial film viscosity and accelerate water droplets coalescence. A maximum water separation efficiency (WSE) of 97% was achieved in the case of KD1 and 88% for DGH2, and using a (1:1) polymer blend demulsifier further increased WSE to 99% after 100 min.

Low pressure modified polyamide 6 membrane for effective fractionation of dyes and NaCl

A co-polymer (SPAA6) of 5-sulfoanthranilic acid (5SAA) and ε-caprolactam was used to prepare membrane through nonsolvent induced phase separation (NIPS) method. The micro-structure of membrane was adjusted by small molecules to improve mechanic strength and performance, involving 7 commercial ionic surfactant and a self-synthesized one, S20. S20 showed the best compatibility with SPAA6, which converted spherical phase into network of strip-like units in micro-structure of membrane. Meanwhile, average pore size of the membrane was narrowed from 4.271 nm to 3.391 nm, tested by BET method. Tensile strength of membrane was improved from 2.5 MPa to 2.9 MPa. Therefore, anionic dyes rejection and membrane stability were both improved. It actually demonstrated that molecular weight distribution of SPAA6 was crucial for micro-structure construction of membrane since S20 was the SPAA6 of low molecular weight. In blend solution filtration test, membrane MS2 (1:2 for S20:SPAA6) displayed 98.22% rejection to Congo Red (CR) acid and 96.18% NaCl permeation under 1 bar. It showed 80.18% rejection to chrome blue K (ABK) and 96.28% NaCl permeation. Both water permeance were higher than 3.5 L·m−2·h−1·bar. Membrane MS2 showed the potential of fractionation of dye and NaCl, which was promising in textile waste water treatment.

Application of commercial zwitterionic surfactants and ionic liquids to reduce interfacial tension and alter wettability in a carbonate reservoir

ABSTRACTInterfacial tension (IFT) reduction and wettability alteration are major mechanisms to chemically enhanced oil recovery (CEOR) in carbonate reservoirs. The purpose of this research was to investigate the effects of different surfactants on IFT and wettability alteration. Four different surfactants including ionic liquids and zwitterionic surfactants, namely [C12mim]Cl, TR-880, NX-2760, and NX-1510, were used in this study. Reservoir core samples, formation brine and crude oil from the Karanj oil field, located in Iran were used. The results showed that the tested surfactants are capable of reducing IFT significantly, changing the wettability to greater hydrophilicity, thus potentially facilitating oil recovery.

Synthesis of Triazole‐Based Nonionic Surfactants for Nanostructured Drug Delivery: Investigation of Their Physicochemical and Biological Aspects

AbstractSynthesis of novel nonionic surfactants has attracted attention of synthetic chemists due to the issues of the currently used commercial surfactants. The synthesis of three biocompatible triazole‐based nonionic surfactants is reported for nanovesicular drug loading. The surfactants were synthesized in a three‐step reaction and characterized using 1HNMR and mass spectroscopy techniques. They were investigated for their critical micelle concentration (CMC) using a UV–Visible spectrophotometer. Their biocompatibility was investigated against cell culture and in blood. All the synthesized nonionic surfactants were further explored for their nanovesicular drug loading using clarithromycin as a model hydrophobic drug. Nonionic surfactants revealed lower CMC in 35–45 μM and were less hemolytic and cytotoxic. They were capable of self‐assembling in nanosize niosomal vesicles encapsulating increased amounts of drug. The results suggest the synthesized nonionic surfactants as biocompatible nanotechnology‐based drug‐delivery vehicles.

Influence of salinity and hardness on the micellization of an extended surfactant studied by turbidimetry

The injection of surfactants as the active component of Enhanced Oil Recovery (EOR) formulations is the current chemical method with the more promising potential because it produces substantial reduction of oil/water interfacial tension. However, the molecular arrangements depending on salinity and hardness, is not well understood. This is a key factor when trying to understand the solubilization of oil and the retention of surfactant during EOR processes. Nevertheless, the formation of micelles is one of the phenomena most affected by the salt concentration but, usually, this parameter is not considered. In this work, the micellization of a commercial extended surfactant at different concentrations and several salinities and hardness is studied. Results showed that size, shape and/or number of micelles are affected by the salinity and hardness. The explanations for this fact include the formation and re-solubilization of calcium soaps, salting-out phenomena and the electric charge shielding, which affect the micellar packing factor. The re-arrangement of molecules, depending on the electrolytes in solution, could favor the formation of spherical, rod-like micelles, and eventually the co-existence of both, or even other types of aggregates and it could be inferred by the analysis of set of data obtained from simple and cheap technique as turbidimetry and complimentary verified by a more sophisticated technique such like DLS.

Effect of the number of ethylene oxide units on the properties of synthesized tailor-made cationic gemini surfactants for oilfield applications

The solubility and heat stability of the surfactants are the most prominent features required for oilfield applications. Commercial surfactants such as petroleum sulfonate, polyoxyethylene ether, and alkyl benzyl sulfonate suffer because of stability issues under high salinity and high-temperature conditions. Herein, two new cationic amido-amine type poly(ethylene oxide) gemini surfactants containing lower and higher degree of ethoxylation were synthesized. It was observed that the addition of a sufficient number of ethylene oxide groups between the hydrophobic tail and the ionic head group of the cationic gemini surfactant significantly enhanced their solubility. The surfactant containing a higher degree of ethoxylation was found to be soluble in formation water and seawater. However, the surfactant with a lower degree of ethoxylation precipitated in formation water and seawater and hence was not studied further. Thermogravimetric analysis results of the surfactants containing a higher degree of ethoxylation exhibited degradation temperature above 300 °C that was greater than the typical reservoir temperature (90 °C). The structure characterization results of the aged sample of surfactant at 90 °C for 90 days demonstrated the survival of the original chemical structure, revealing a high long-time heat stability. The reduction in critical micelle concentration (CMC) was observed upon enhancing salt concentration, and the minimum CMC was noticed in seawater (3.91 × 10−5 mol/L). Rheological investigations revealed that the viscosity, as well as storage modulus, was reduced upon increasing the concentration of surfactant. The surfactant also exhibited superior foaming properties compared to the commercial surfactants. The cationic amido-amine type poly(ethylene oxide) gemini surfactants showed excellent surface and thermal properties and are potential candidates for oilfield applications such as enhanced oil recovery in harsh reservoir conditions.

Ion flotation removal of a range of contaminant ions from drinking water

The effect of a natural, biodegradable surfactant obtained using a novel and efficient chemical reaction between cysteine (a thiol-based amino acid) and an octanoyl (C8) compound, was investigated for its application to the ion flotation removal of low levels of different contaminant ions from aqueous solution. The synthesised amino acid-based single-chain surfactant shows a high water solubility and exhibits extensive foaming in a typical flotation chamber over a wide pH range. In a batch ion flotation process, this surfactant was able to remove 97–99% of the 5ppm of strontium, lanthanum, arsenic and different heavy metal ion levels present in contaminated water, in a simple, single-stage physiochemical process; while this surfactant showed significantly lower efficiency for the removal of iron, selenium and gold ions. In a solution mixed with heavy-metal ions, including arsenic, copper, cadmium, magnesium, lanthanum, chromium, lead and iron, the surfactant shows high affinity to bind with arsenic, copper and chromium compared with the others. Moreover, the effectiveness of this surfactant for removal of gold ions from aqueous binary mixtures in the presence of iron and mercury ions has been explored. This new surfactant is highly efficient compared with commercial surfactants (e.g., SDS and CTAB) for ion flotation. Importantly it is an environmentally acceptable compound. It can be decomposed into cysteine (amino acid) and octanoic acid (caprylic acid, which is taken as a dietary supplement). The surfactant has the potential for wide usage in ion flotation and in froth flotation.

Production of bio-base surfactant Saponin from Cissuspopulnea plant leave

Cissuspopulnea plant shows higher surface tension and sorption behaviour property as well as foam formation/capacity far better especially leaves and roots than some commercial/synthetic surfactants (OMO) that were used in the study. This saponin- based surfactant is significantly be as an eco-friendly and may show better biodegradability than the commercial surfactants. The natural surfactant from Cissuspopulnea plants leave and roots will contribute to efforts in diversify the Nigerians economy, a way to solve the problem of non-biodegradable, high price and non-eco-friendly phenomenon that exists in the production of commercial/synthetic surfactant and add value to green chemistry and sustainable development and exploitation of the cleansing properties of saponin present in Cissuspopulnea plants.

Nanoparticle Formation in Stable Microemulsions for Enhanced Oil Recovery Application

Magnetic iron oxide and titanium dioxide nanoparticles (NPs) have been synthesized inside stable oil-in-water microemulsions in harsh environment of high temperature-high salinity (HT-HS). Screening of anionic−nonionic mixture of commercial surfactants was carried out to identify the appropriate compositions for the production of stable microemulsions in harsh environment. The effects of salinity and NPs formation on interfacial tension and rheological properties of microemulsions were evaluated and compared with other studies. It was found that oil-inwater microemulsions exhibit a non-Newtonian behavior in the absence of NPs, while the surfactant solutions show Newtonian behavior. The shear-thinning characteristic of microemulsions was improved and the interfacial tension between microemulsions and oil phase was increased after generation of NPs. A set of flooding experiments were accomplished using a microfluidic device to assess the efficiency of enhanced oil recovery on the pore scale in the absence and presence of NPs. The flooding tests confirmed the improvement of oil recovery efficiency after the formation of NPs inside the microemulsions. The oil displacement of API flooding was equal to 69.8% and the maximum oil displacement of 76.9% was observed after the injection of microemulsion containing iron oxide NPs.

Effect of residual chemicals on wormlike micelles assembled from a C22-tailed cationic surfactant

HypothesisUltra-long-chain surfactants, particularly C22-tailed ones, have attracted considerable attention because of their ease of self-assembly into wormlike micelles (WLMs). Commercial C22-tailed surfactants often contain non-negligible amounts of chemical residues introduced during their production. Since the noncovalent driving force of wormlike self-assembly can be greatly affected by the composition, we hypothesized that the residual chemicals could play a significant role in tuning the micelle microstructure and macroscopic properties of the surfactants. ExperimentsTo confirm this hypothesis, a highly pure (>99%) C22-tailed cationic surfactant, N-erucylamidopropyl-N,N,N-trimethylammonium iodide (EDAI) was synthesized, and various amounts of corresponding reactants (iodomethane or N-erucamidopropyl-N,N-dimethylamine) or solvents (acetone) commonly used in surfactant synthesis were introduced as residues. The impact of each individual residue on the macroscopic appearances, rheological properties, and micelle morphology of the surfactant solution were investigated. FindingsIncreasing the residue fraction in the EDAI solution resulted in an initial increase, followed by a dramatic drop in solution viscosity. This behavior was described in terms of micellar structural transformations based on analysis of cryo-TEM observations and surface tension measurements. These findings are of crucial importance in understanding the sophisticated behaviors of WLMs and will benefit the industrial preparation of ultra-long-chain surfactants for commercial use.

Electrodes for Membrane Surface Science. Bilayer Lipid Membranes Tethered by Commercial Surfactants on Electrochemical Sensors.

Commercial surfactants, which are inexpensive and abundant, were covalently grafted to flat and transparent electrodes, and it appears to be a simple functionalization route to design biomembrane sensors at large-scale production. Sparsely tethered bilayer lipid membranes (stBLM) were stabilized using such molecular coatings composed of diluted anchor-harpoon surfactants that grab the membrane with an alkyl chain out of a PEGylated-hydrogel layer, which acts as a soft hydration cushion. The goal of avoiding the synthesis of complex organic molecules to scale up sensors was achieved here by grafting nonionic diblock oligomers (Brij58 = C xH2 x+1(OCH2CH2) nOH with x = 16 and n = 23) and PEO short chains ((OCH2CH2) nOH with n = 9 and n = 23) from their hydroxyl (-OH) end-moiety to a monolayer of -Ar-SO2Cl groups, which are easy to form on electrodes (metals, semiconducting materials, ...) from aryl-diazonium salt reduction. A hybrid molecular coating on gold, with scarce Ar-SO2-Brij58 and PEO oligomers, was used to monitor immobilization and fusion kinetics of DOPC small unilamellar vesicles (SUV) by both quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) techniques. Using flat and transparent thin chromium film electrodes, we designed biosensors to couple surface sensitive techniques for membranes, including X-ray reflectivity (XRR), atomic force microscopy (AFM) with subnanometer resolution, and optical microscopy, such as fluorescence recovery after photobleaching measurements (FRAP), in addition to electrochemistry techniques (cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)). The advantages of this biomembrane-sensing platform are discussed for research and applications.

Trichloroethylene solubilization using a series of commercial biodegradable ethoxylated fatty alcohol surfactants

AbstractBACKGROUNDAlthough certain pollutants are prohibited or heavily regulated, particularly in Europe and the USA, contaminated sites still represent a serious threat to the environment and health. The physical and chemical properties of ‘dense non‐aqueous phase liquid’ (DNAPL) pollutants such as trichloroethylene (TCE), including their low solubility, high specific density and tendency to remain adsorbed to organic materials, make their removal from polluted sites extremely difficult.RESULTSThis study tested the ability of a series of commercial fatty alcohol ethoxylated surfactants of CiEj type (i = number of carbons in the alkyl chain; j = number of ethylene oxide (EO) units), known to be biodegradable and low‐cost, to improve the solubility of TCE in water; this would make its removal from contaminated sites more effective. The solubility of TCE in Synperonic™ 91/5 (C10E5), 91/6 (C10E6), 91/8 (C10E8), 91/10 (C10E10) and 13/8 (C13E8) aqueous solutions was evaluated and the solubilization performances were reported as molar and weight solubilization ratios (MSR and WSR). Solubility was measured above the critical micelle concentration (CMC) up to 0.7 mol L−1 at 5, 20 and 30 °C to assess the feasibility of the approach for TCE removal from sites located in different climatic areas. Increasing EO units contributed to improved TCE solubility (at constant alkyl chain length).CONCLUSIONThe best surfactant was Synperonic™ 91/10 with an MSR of 3.54 at 19 °C. The results show that an optimal combination of EO units and alkyl chain length, and not only the hydrophilic–lipophilic balance (HLB) value, is key for the design of effective TCE remediation systems from groundwater. © 2019 Society of Chemical Industry

Effects of the water-oil volume ratio and premixing or pre-equilibration on the interfacial tension and phase behavior of biphasic mixtures

The interfacial tension (IFT) between an aqueous surfactant solution and displaced crude oil in a tertiary oil recovery process is the most important parameter affecting the oil mobilization. The key question, which has not been addressed previously in a systematic way, is which IFT is the most relevant to the oil recovery: the un-pre-equilibrated IFT, or the IFT obtained after the aqueous solution has equilibrated, totally or partially, with the oil. The un-pre-equilibrated IFT values may be close to the IFT values of oil/water during the initial stages of the oil recovery process before phase equilibration. Conversely, the pre-equilibrated IFT values may be close to the IFTs during the later oil recovery stages, because then the phases are closer to equilibrium. Here, we compare the IFT behavior in the laboratory at 24 °C and at 1 atm of un-pre-equilibrated and pre-equilibrated systems of a crude oil, a brine containing eight salts, and a commercial surfactant. The synthetic brine used is similar to the one present in an actual oil reservoir. The surfactant used here is a commercial anionic surfactant, PETROSTEP® S-13D HA, which is the sodium salt of a single-extended-isopropoxylated-chain sulfate. The pre-equilibrated equilibrium IFT (EIFT) values are quite different from the un-pre-equilibrated EIFT values. In addition, the effects of three mixing methods and the water-to-oil volume ratio (WOR) on the pre-equilibrated IFT were evaluated. Of the three methods examined here, (A) mild mixing, (B) magnetic stirring, and (C) shaking vigorously by hand, method C combined with centrifugation is the best method to evaluate the phase behavior and EIFT of premixed systems and produces mixtures that are the closest to the equilibrium state. For method C, the surfactant concentration in the aqueous layer after equilibration was the lowest due to surfactant partitioning into the oil phase. Moreover, the WOR affects the pre-equilibrated EIFT in brine systems significantly because of the different proportions of surfactant components that partition into the oil phase. For the surfactant at an initial concentration of 0.8 g·mL−1 in the aqueous phase, as the WOR decreases from 2.33 to 0.43, or as the oil volume fraction in the mixture, φ, increases from 0.3 to 0.7, the surfactant concentration in the aqueous layer drops to the range from 5.9 g·mL−1 to 2.2 g·mL−1, and the EIFT increases by a factor of ˜70. In addition, the pre-equilibrated EIFTs are different from the un-pre-equilibrated EIFTs at the same surfactant concentration in the aqueous layer evidently because of preferential partitioning of the various surfactant components. This phenomenon can be accounted for with a simple two-phase extraction model, if the more surface-active component partitions preferentially in the oil. Therefore, the effects of the mixing method and centrifugation, the WOR, and the preferential partitioning of surfactant components into the oil phase should be evaluated for general surfactant screenings for uses in EOR applications.