Surfactant Critical Concentration Research Articles

Synthesis and Kinetics of CO2-Responsive Gemini Surfactants.

Surfactants are hailed as "industrial monosodium glutamate", and are widely used as emulsifiers, demulsifiers, water treatment agents, etc., in the petroleum industry. However, due to the unidirectivity of conventional surfactants, the difficulty in demulsifying petroleum emulsions generated after emulsification with such surfactants increases sharply. Therefore, it is of great significance and application value to design and develop a novel switchable surfactant for oil exploitation. In this study, a CO2-switchable Gemini surfactant of N,N'-dimethyl-N,N'-didodecyl butylene diamine (DMDBA) was synthesized from 1, 4-dibromobutane, dodecylamine, formic acid, and formaldehyde. Then, the synthesized surfactant was structurally characterized by infrared (IR) spectroscopy, hydrogen nuclear magnetic resonance (1H NMR) spectroscopy, and electrospray ionization mass spectrometry (ESI-MS); the changes in conductivity and Zeta potential of DMDBA before and after CO2/N2 injection were also studied. The results show that DMDBA had a good CO2 response and cycle reversibility. The critical micelle concentration (CMC) of cationic surfactant obtained from DMDBA by injecting CO2 was 1.45 × 10-4 mol/L, the surface tension at CMC was 33.4 mN·m-1, and the contact angle with paraffin was less than 90°, indicating that it had a good surface activity and wettability. In addition, the kinetic law of the process of producing surfactant by injecting CO2 was studied, and it was found that the process was a second-order reaction. The influence of temperature and gas velocity on the reaction dynamics was explored. The calculated values from the equation were in good agreement with the measured values, with a correlation coefficient greater than 0.9950. The activation energy measured during the formation of surfactant was Ea = 91.16 kJ/mol.

Investigation of micellization and thermodynamic properties of cationic gemini surfactant (12-2-O-2-12) in the presence of organic solvents

The micellization behaviour and thermodynamic properties of synthesized cationic gemini surfactant (12-2-O-12-12), N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-(oxybis(ethane-2,1-diyl))-diammonium dibromide were studied in the presence of organic solvents for four different temperatures (25, 30, 35 and 40 °C). Aqueous solutions of 10 % and 20 % methanol (MeOH), ethanol (EtOH), isopropanol (IPOH) and dimethyl sulfoxide (DMSO) were used as solvents. The critical micelle concentration (CMC) of cationic gemini surfactant and the degree of counterion dissociation (α) were determined by the conductometric method. Using the CMC and α values for each of the four temperatures, the values of the standard Gibbs free energy (ΔGmo), Gibbs free energy of transfer (ΔGm,transo), enthalpy (ΔHmo), and entropy (ΔSmo) of micellization were calculated. It was observed that the CMC and α values increased with increasing solvent percentage and temperature. It was found that in all cases, the standard Gibbs free energy and enthalpy values were negative while both the micellization entropy and the standard Gibbs free energy of transfer are positive. Negative Gibbs free energy values indicated that micellization was a spontaneous situation, while positive entropy values indicated the existence of a disordered situation. The positive ΔGm,transo values show that the presence of solvents makes the environment unfavorable for micelle formation.

Surfactant-Driven Dynamic Changes in Rheology of Activated Carbon Slurry Electrodes.

Carbon black slurry electrodes are an effective means to improve flow battery performance by increasing the active surface area necessary for electrochemical reactions with a cost-effective material. Current challenges with this specific flow battery chemistry include the stability and flowability of the carbon black suspensions, especially in response to formulation choices. Advancing the manufacturing, operation, and performance of these redox flow batteries requires a deeper understanding of how slurry formulation impacts its rheological profile and ultimately battery performance. In response to this need, the linear and nonlinear rheological responses of activated carbon (AC) based slurry electrode materials used in an all-iron flow battery in the presence of a nonionic surfactant (Triton X-100) were measured. Results from these measurements show the slurry is a colloidal gel with elasticity remaining constant despite increasing surfactant concentration until α (= Csurf/CAC) < 0.65. However, at α ≥ 0.65, the slurry abruptly transitions to a fluid with no measurable yield stress. This critical surfactant concentration at which the rheological profile undergoes a dynamic change matches the concentration found previously for gel collapse of this system. Moreover, this transition is accompanied by a complete loss of electrical conductivity. From these data we conclude the site specific adsorption of surfactant molecules often used in slurry formulation has a significant and dramatic impact on the stability and flowability of these suspensions. Work presented herein demonstrates the importance of additive choices when formulating a slurry electrode.

Surfactant foamulsion stability in the absence and presence of salt

Foamulsions are widely used in many fields but the stability of them is still not fully understood. We investigate the evolution of foamulsions in the absence and presence of inorganic salt. For the system without salt, it is found that the effect of oil on the foamulsion properties depends on the critical threshold concentration of surfactant (300 mM), below which the foamulsion aging is slowed down and above it its evolution is facilitated. When salt is added, the surfactant molecules precipitates to form crystals, foamulsions tend to be generated in regions where the surfactant concentration is not less than the salt concentration, but it is difficult to foam at salt concentrations higher than 200 mM, independent of the oil concentration, unless the surfactant concentration is very high. For the prepared stable foamulsions, the stabilization mechanism is due to the inhibition of coarsening and coalescence of bubbles and oil droplets by the adsorption of surfactant molecules and crystal particles onto their surfaces. The investigation of adsorption kinetics show that maybe the crystals move to the surface of bubbles is faster than oil droplets. The system consisting of surfactant, oil, salt and water is simple and temperature sensitivity, which could have many potential applications.

Enhanced oil recovery using a novel non-ionic surfactant synthesized from olive oil: Performance and synergistic effects

In recent years, there has been increasing focus on the application of natural surfactants in enhanced oil recovery (EOR) due to the environmental concerns associated with conventional surfactants. This study presents a systematic approach in this field by introducing a novel non-ionic surfactant synthesized from olive oil through a two-step synthesis process. The synthesis of olive oil alkanolamide (OOAA) surfactant was confirmed using FTIR and characterized by GC–MS analysis. The synthesized OOAA surfactant showcased favorable attributes including effective emulsification, wettability modification, interfacial tension reduction, limited adsorption losses, and efficient oil displacement. Critical micelle concentration (CMC) of OOAA surfactant was found to be very low, 50 ppm at 303 K. At CMC, the interfacial tension (IFT) of synthesized OOAA surfactant was found to be 18.75 mN/m, which further decreased by 26 % at the optimal salinity of the NaCl solution. The contact angle study revealed significant wettability alteration for the optimized salt concentration. Adsorption of the surfactant onto rock surfaces was analyzed by using two adsorption isotherms. The Langmuir adsorption isotherm emerged as the best fitting model, yielding an R2 value of 0.899. The formulation of OOAA surfactant/PHPA/NaCl solution showed shear thinning behavior and also exhibited viscoelastic properties. The synergism of OOAA surfactant with PHPA polymer led to a substantial tertiary recovery of 31 % OOIP over the conventional water flooding. These comprehensive findings underline the potential of the synthesized OOAA surfactant for enhancing oil recovery in sandstone reservoirs.

Synthesis and surface activity of novel amino acid surfactants

AbstractAmino acid surfactants (AASs) based on environmentally friendly biomasses have the characteristics of renewable, easy biodegradation, antibacterial and low toxicity, and have been widely used in daily chemicals, pharmaceuticals, and other fields. This study concerned the use of octanal and amino acids as raw materials. In addition, seven types of amino acid‐based surfactants, through Collins reagents, Wittig‐Hornor reaction, and aza‐Micheal addition reaction, and amino acid head groups were connected with the alkyl chain by the CN bond. The structures were confirmed by infrared spectroscopy (FT‐IR) and nuclear magnetic resonance spectroscopy (1HNMR). Its surface activity and adsorption properties are evaluated. The physical properties of amino acid‐based surfactants were tested by surface tension and dynamic contact angle. The results demonstrated that histidine‐based amino acid surfactant (C8His) has the lowest critical micelle concentration (CMC) and surface tension at CMC (γCMC), 0.39 mmol L−1 and 28.79 mN L−1, respectively. Amino acid residues contribute to reducing the critical micelle concentration of surfactant. The interfacial adsorption of glycine‐based amino acid surfactant (C8Gly) significantly improved with the increase in temperature, so the surface tension decreased significantly. In addition, sodium chloride could effectively enhance the interfacial adsorption, and the gas–liquid interfacial tension and contact angle of AASs decrease.

The effects of a novel Bio-based surfactant derived from the Acacia concinna plant on chemical enhanced oil recovery in the presence of various salts and a synthesized HSPAM polymer

In this investigation, a unique idea of using a green surfactant derived from Acacia concinna (AC) plant and a hydrophobically modified copolymer consistingof acrylamide and styrene (HSPAM) for chemical enhanced oil recovery (CEOR) was studied. Firstly, the characteristics of AC green surfactant were comprehensively examined using different standard analyses, such as thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR) spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) techniques. The thermal stability test of the AC green surfactant demonstrated an acceptable 1.93% weight loss at the 80 °C (reservoir temperature). Additionally, 1H NMR and FT-IR investigations proved the structure of the saponin compound as the surfactant agent. Then, the compatibility tests revealed no precipitation at various concentrations of different salts. The efficiency of the AC green surfactant and HSPAM was examined with three different salts, including K2SO4, MgSO4, and NaCl, as three common salts present in the formation brine (FB) with salinities up to 97,000 ppm. Different experiments, including contact angle and interfacial tension (IFT) measurements, zeta potential measurements, emulsion and core flooding experiments were conducted and the efficiency of these materials for CEOR purposes was examined. The IFT results revealed that 1000 ppm is the critical micelle concentration (CMC) of AC green surfactant in deionized water (DIW). Based on the measured IFT and contact angle values, the most effective salt was K2SO4, followed by NaCl, and MgSO4. The addition of 2000 ppm of HSPAM polymer as the optimum concentration of HSPAM was very efficient in improving the performance of AC green surfactant and producing a higher quality of Winsor type III emulsion. The maximum oil recovery factor of 71.17% was achieved when 1000 ppm of AC green surfactant was injected as the tertiary recovery, and the value was further increased to 77.92% when 2000 ppm of HSPAM and 1000 ppm of AC green surfactant were injected as the tertiary recovery.

Long‐lasting chemiluminescence by aggregation‐induced emission surfactant with ultralow critical micelle concentration

AbstractThe development of green and simple chemiluminescence (CL) systems with intensive and long‐lasting emission is highly desirable in lighting and extension of their applications. In this study, it is found that the involvement of aggregation‐induced emission (AIE) surfactant could greatly enhance the CL of luminol–H2O2–Co2+ system. The inserted hydrophobic tetraphenylethylene fluorophore in AIE is able to increase the hydrophobicity of alkyl chain and decrease the critical micelle concentration (CMC) of surfactant. The synergistic effect of micelle‐improved enrichment and CL resonance energy transfer endows luminol–H2O2–Co2+ system intensive and long‐lasting emission under neutral pH conditions (pH 7.4). The visible emission is still observed even after 60 min. Our study has opened a new avenue for exploring green and simple effective CL systems through AIE surfactant with unltralow CMC toward various applications in lighting, optical sensing, and photocatalysis, etc.

Structure Identification of Adsorbed Anionic–Nonionic Binary Surfactant Layers Based on Interfacial Shear Rheology Studies and Surface Tension Isotherms

Mixtures of anionic sodium oleate (NaOl) and nonionic ethoxylated or alkoxylated surfactants improve the selective separation of magnesite particles from mineral ores during the process of flotation. Apart from triggering the hydrophobicity of magnesite particles, these surfactant molecules adsorb to the air-liquid interface of flotation bubbles, changing the interfacial properties and thus affecting the flotation efficiency. The structure of adsorbed surfactants layers at the air-liquid interface depends on the adsorption kinetics of each surfactant and the reformation of intermolecular forces upon mixing. Up to now, researchers use surface tension measurements to understand the nature of intermolecular interactions in such binary surfactant mixtures. Aiming to adapt better to the dynamic character of flotation, the present work explores the interfacial rheology of NaOl mixtures with different nonionic surfactants to study the interfacial arrangement and viscoelastic properties of adsorbed surfactants under the application of shear forces. Interfacial shear viscosity results reveal the tendency on nonionic molecules to displace NaOl molecules from the interface. The critical nonionic surfactant concentration needed to complete NaOl displacement at the interface depends on the length of its hydrophilic part and on the geometry of its hydrophobic chain. The above indications are supported by surface tension isotherms.

Surfactant Control of Coffee Ring Formation in Carbon Nanotube Suspensions.

The coffee ring effect regularly occurs during the evaporation of colloidal droplets and is often undesirable. Here we show that adding a specific concentration of a surfactant can mitigate this effect. We have conducted experiments on aqueous suspensions of carbon nanotubes that were prepared with cationic surfactant dodecyltrimethylammonium bromide added at 0.2, 0.5, 1, 2, 5, and 10 times the critical micelle concentration. Colloidal droplets were deposited on candidate substrates for printed electronics with varying wetting characteristics: glass, polyethylene terephthalate, fluoroethylene propylene copolymer, and polydimethylsiloxane. Following drying, four pattern types were observed in the final deposits: dot-like, uniform, coffee ring deposits, and combined patterns (coffee ring with a dot-like central deposit). Evaporation occurred predominantly in constant contact radius mode for most pattern types, except for some cases that led to uniform deposits in which early stage receding of the contact line occurred. Image analysis and profilometry yielded deposit thicknesses, allowing us to identify a coffee ring subfeature in all uniform deposits and to infer the percentage coverage in all cases. Importantly, a critical surfactant concentration was identified for the generation of highly uniform deposits across all substrates. This concentration resulted in visually uniform deposits consisting of a coffee ring subfeature with a densely packed center, generated from two distinct evaporative phases.

Study of a high efficient composite foam drainage surfactant for gas production

Abstract The foam drainage technique for gas production has the disadvantage of requiring a large amount of surfactant and having low resistance to salt and oil. In this study, a new surfactant mixture (composite surfactant) of lauramidopropyl betaine (LAB-35), α-olefin sulfonate (AOST), sodium alkyl sulfonate (SASE) and cetyltrimethylammonium bromide (CTAB) was tested and its foaming properties were investigated in detail. The foaming properties were determined using high-speed measurements and the Ross-Miles method. The results show that the foaming volume of the composite surfactant can reach 563 mL, indicating that the foaming behaviour of the composite surfactant is more effective than that of the individual surfactants used for the mixture. In addition, the results show that the composite surfactant has a resistance to salt, methanol and condensate oil that most foam drainage agents do not have. However, the stability of the composite surfactant gradually decreases with increasing temperature and concentration. The surface tension was measured and the critical micelle concentration of the composite surfactant is 0.023 g/L.

Slip of submerged two-dimensional liquid-infused surfaces in the presence of surfactants

Using numerical simulations, we investigate the effects of Marangoni stresses induced by surfactants on the effective slip length of liquid-infused surfaces (LIS) with transverse grooves. The surfactants are assumed soluble in the external liquid shearing the surface and can adsorb onto the interfaces. Two different adsorption models are used: a classical Frumkin model and a more advanced model that better describes the decrease of surface tension for minuscule concentrations. The simulations show that LIS may face even more severe effects of surfactants than previously investigated superhydrophobic surfaces. Constructing an analytical model for the effective slip length, we can predict the critical surfactant concentration for which the slip length decreases significantly. This analytical model describes both adsorption models of LIS on a unified framework if properly adjusted. We also advance the understanding of when surfactant advection gives rise to highly skewed interfacial concentrations: the so-called partial stagnant cap regime. To a good approximation, this regime can only exist below a specific surfactant concentration given by the Marangoni number and the strength of the surfactants.

Experimental evaluation of non-ionic mixed surfactant formulations at high-temperature and high-salinity conditions

Non-ionic alkyl polyglucoside (APG) surfactants have been considered as eco-friendly, nontoxic and biodegradable surfactants. This study investigated the feasibility and advantages of new formulations for mixed surfactants consisting of a commerical APG product and one of the following alkyl amines (AAs) – dodecylamine (C12A), tetradecylamine (C14A), hexadecylamine (C16A), and octadecylamine (C18A) for improved oil production applications in carbonate reservoirs under high-temperature and high-salinity (HTHS) conditions. The physicochemical properties including compatibility, surface tension, interfacial tension (IFT), static adsorption, wettability alteration of the solutions comprising APG and various AA under HTHS conditions were evaluated. The self-assemble behavior of molecules between APG and C12A was characterized based on the Scanning Electron Microscopy (SEM) analysis. The formulations with an ultra-low IFT were introduced and the mechanisms resulting in such ultra-low IFT were further studied and discussed. The yielded APG/AA formulation was injected as the chemical flooding agent into a micromodel to investigate the efficiency of oil displacement. Commercial APG products exhibited excellent compatibility with the simulated injection water at reservoir temperature. After mixed with AA, the APG solution became hazy or phase separated above a critical concentration (Ccrit) of AA. Ccrit was found to decrease with an increase of the hydrocarbon chain, suggesting that more APG surfactants are required to solubilize the AA with longer alkyl hydrocarbon chain. In the presence of AA, the critical micelle concentration (CMC) of APG surfactant significantly reduced due to the formation of a compact micellar structure. APG yielded a low IFT at 90 °C and a concentration of 2 g/L in the order of 10−2 mN/m, while an ultra-low IFT in the order of 10−3 mN/m was obtained upon addition of a small amount (0.3–0.5 g/L) of C12A. SEM images and proposed IFT reduction mechanisms indicated that APG and C12A synergistically generated a more compact structure via hydrophobic interaction between the hydrophobic moieties and hydrogen bonding between the hydrophilic parts of the chemicals comparing the aggregated structure formed by APG alone, such effect could eventually lead to a decrease in IFT between oil and water. The amounts of chemical adsorption and contact angle of an oil droplet on carbonate cores were not affected upon addition of AA. The micromodel test showed that the produced oil by injection of the designed APG/AA formulations was further enhanced after water flooding. Among the formulations, APG/C12A flooding resulted in a highest effectiveness on oil displacement with a cumulative oil production of 78.7% at the end of injections. To sum up, new APG/AA-based formulations were designed with an ultra-low IFT resulting from a much compact amphiphilic structure along oil-water interface. This study shows a great potential of APG surfactant and the related formulations in improving oil production for HTHS carbonate reservoirs.

Influence of polymerizable surfactants on the adhesion performance and water resistance of water-based acrylic pressure-sensitive adhesives (PSAs)

The behavior of different polymerizable surfactants was investigated to improve the water-resistance of pressure-sensitive adhesives (PSAs) based on acrylic acid (AA) and n-butyl acrylate (n-BA). Differences in the adhesion properties were found according to the chemical structure and the critical micelle concentration of the polymerizable surfactant, especially when compared to the non-polymerizable reference surfactant (Dowfax 2A1). The polymerizable surfactants with a branched structure resulted in more gel content and higher glass transition temperature in the adhesive. In general, the peel resistance and tack properties decreased with the use of polymerizable surfactants in the PSA formula. However, increased shear resistance was observed with respect to the PSA adhesive synthesized with the reference surfactant. Furthermore, the adhesives made with higher molecular weight polymerizable surfactants resulted in higher shear elastic modulus, shear strength, and deformation energy than the rest of the PSA adhesives. On the other hand, as expected, all the polymerizable surfactants studied contributed to the improved water resistance of the PSA compared to the reference PSA prepared with a conventional surfactant. The covalent bond formed between the polymer and the surfactant limited the migration of the surfactant towards the air-film interface thus reducing the formation of water entry pathways. The polymerizable surfactants with linear molecular structure showed the best water resistance performance.

N-Cholyl d-Penicilamine Micelles Templated Red Light-Emitting Silver Nanoclusters: Fluorometric Sensor for S2- Ions and Bioimaging Application Using Zebrafish Model.

Red-light-emitting silver nanoclusters (AgNCs) are recently emerged as a promising nanoprobe in the field of biomedical applications, because of their attractive properties, including brightness, luminescence stability, and better biocompatibility. In this report, we have developed highly water-soluble red-light-emitting AgNCs by using N-cholyl d-penicilamine (NCPA) as a biosurfactant at above the critical micelle concentration (CMC) at room temperature. Moreover, the NCPA was initially synthesized by demonstrating the reaction between cholic acid and d-penicilamine via a simple coupling reaction strategy. The primary and secondary critical micellar concentration (CMC) of NCPA surfactant was measured using pyrene (1 × 10-6 M) as a fluorescent probe, and the values were found to be 3.18 and 10.6 mM, respectively. Steady-state fluorescence measurements reveal that the prepared AgNCs shows the excitation and emission maxima at 365 and 672 nm, respectively, with a large Stokes shift (307 nm). The average lifetime measurements and quantum yield of the AgNCs were calculated to be 143.43 ns and 16.34%, respectively. Also, the red luminescent NCPA-templated AgNCs was synthesized in various protic and aprotic polar solvents, among which DMF and DMSO exhibit bright emission at longer wavelength as synthesized in aqueous medium. At higher concentration of AgNO3, bright luminescent and highly stable solid AgNCs was obtained with excitation and emission maxima at 607 and 711 nm, respectively. Furthermore, the synthesized AgNCs has been successfully utilized as a fluorescent probe for selective and sensitive detection of S2- ions at nanomolar level in water samples, showing its potential applicability for the detection of S2- ions in drinking, river, and tap water samples. Finally, toxicity and bioimaging studies of NCPA-templated AgNCs was demonstrated using zebrafish as in vivo model, showing no significant toxicity up to 200 μL/mL. The AgNCs-stained embryos exhibited red fluorescence with high intensity, which shows that AgNCs are stable in a living system.

Deciphering the mechanism of interaction of an ester-functionalized cationic gemini surfactant with bovine serum albumin: A biophysical and molecular modeling study

Protein–surfactant interactions have relevance in the fields of pharmaceuticals, detergency formulation, pharmacology, personal hygiene products, etc. Accordingly, we have analyzed the biomolecular interaction between a recently synthesized C16-E2O2-C16 gemini surfactant with the transport protein, bovine serum albumin (BSA), utilizing surface tension, fluorescence (intrinsic/extrinsic, synchronous, 3-D and resonance Rayleigh scattering (RRS)), circular dichroism (CD), UV–visible, Fourier transform infrared (FT-IR) and computational methods. The critical micelle concentration (CMC) and surface parameters of the gemini surfactant get modified in the presence of BSA. The interaction of the concerned surfactant with BSA occurred via a static quenching mechanism forming a less stable complex at the higher temperature. Based on calculated thermodynamic parameters, the interaction process was found to be spontaneous (∆Gb0 is negative) and that hydrogen bond (HB) and van der Waals (VDW) forces were predominant forces in stabilizing the complex (both ∆Hb0 and ∆Sb0 are negative). FT-IR and CD measurements demonstrated that the secondary structure conformation of BSA was perturbed because of the BSA-C16-E2O2-C16 complexation. The 3-D and RRS fluorescence studies demonstrated that the BSA size enlarged in presence of the gemini and ensued in the increment of scattering effect and suggested some conformational and micro-environmental alterations of Trp/Tyr residues of BSA (the same results were obtained for pyrene extrinsic fluorescence). Molecular docking and site marker displacement investigations recognized that the surfactant C16-E2O2-C16 predominantly binds within BSA’s site I (sub-domain IIA).

A study on how to control the supramolecular amphiphilic assembly of anionic bola surfactant with calixpyridinium

The fabrication of supramolecular amphiphiles by the host–guest interactions between macrocycles and surfactants is an effective method to improve the physical and chemical properties of amphiphiles. However, as far as we know, lowering the critical micelle concentration of anionic surfactant by the complexation of macrocyclic host is scarcely studied. In this work, we systematically studied the host–guest interactions between calixpyridinium and four select anionic bola surfactants. Only congo red that has a conjugated linker could assemble into supramolecular amphiphile with calixpyridinium accompanied by a decreased critical micelle concentration. As a result, the pKa value of congo red shifted significantly. Moreover, the calixpyridinium–congo red supramolecular amphiphilic assembly exhibited a valuable visible-light response for the complete photodegradation of congo red.

Current trends in protein-surfactant interactions: A review

The protein-surfactant interactions have been investigated for a long time due to their increased effectiveness in cleanliness and industrial processes. Moreover, Covid-19 outbreak has revolutionized the significance of protein-surfactant interactions, as soaps were proved the best cleansers and safe during this period. In this review article, an overview of physico-chemical aspects of protein-surfactant interactions along with various techniques has been discussed. In addition, the effect of different factors such as co-solvent, temperature, pH, chain length of surfactants, salt, and their impact on critical micelle concentration (CMC) of surfactant, structure, binding, thermodynamic parameters, and stability was also explained. This review will help the scientific community in understanding how to improve the effectiveness and applications of proteins and surfactants in pharmaceutical and other industries as protein-surfactant interactions can explain the significant phenomena of hydrophobic and electrostatic interactions.

Natural surfactant for sustainable carbon utilization in cleaner production of fossil fuels: Extraction, characterization and application studies

In this study, the extraction, characterization, and performance evaluation of a green surfactant, derived from bio-resource (Fenugreek seeds), is reported for effective carbon utilization in subsurface applications. Several characterization tools such as Fourier-transform infrared spectroscope, ultraviolet–visible spectroscope, methylene blue active substance test, surface tension tests, and scanning electron microscope were used to confirm saponin (surface activity) in synthesized surfactant and suitably compared with the properties of conventional surfactants in literature. The prepared green surfactant exhibited anionic behavior as validated by elemental analysis and adsorption studies. The critical micellar concentration of surfactant was determined by surface tension and electrical conductivity and its value was found to be around 0.2 wt%. Carbon dioxide absorption potential of green surfactant was envisaged by molality tests which confirmed that carbon dioxide absorption rate of surfactant was 7–18% higher than pure water. As a result, the surfactant showed high foam volume (> 40 ml) and foaming stability (8–10 h). The high temperature performance was also better. At 90 °C, carbon dioxide bubbles of larger size were present in sufficient quantity which indicated that foaming potential of surfactant was not severely affected by temperature. During adsorption studies, the green surfactant solution showed a mass-loss of 48–60% on a sandstone surface, which is better than the one of a conventional surfactant. It also showed superior property than conventional surfactants in adsorption isotherm investigations. Thus, the use of these green surfactants in subsurface scenario for carbon utilization and oil recovery from a porous media is recommended.

Study on foam extinguishing agent based on mixed system of branched short-chain fluorocarbon anionic and hydrocarbon cationic surfactants

The traditional aqueous film-forming foam extinguishing agent (AFFF) plays an important role in fighting liquid fires, but its environmental hazard are also increasingly prominent. The key component of conventional AFFF is fluorocarbon surfactant containing perfluorinated C8 segment, which is one of the most refractory organic pollutants in the world. In this paper, a perfluorinated branched short-chain alkyl side chain fluorocarbon anionic surfactant with high surface activity and simple synthesis route was prepared. The surface activity and aggregation behavior of the mixed solution of fluorocarbon and hydrocarbon surfactants were studied by surface tension meter and transmission electron microscope (TEM). When the mixture ratio of fluorocarbon and hydrocarbon surfactant reached 1:10, the addition of cetyltrimethylammonium bromide (CTAB) had little effect on the interfacial adsorption, but could significantly reduce the critical micelle concentration (CMC) of fluorocarbon surfactant. Meanwhile, three kinds of environment-friendly AFFF formulations (F-1, F-2, F-3) were designed with the mixed system of different hydrocarbon surfactants and this fluorocarbon anionic surfactant as foaming agents. The foam properties revealed the F-2 possessed excellent foam performance, the initial foam height h0 was 120 mm, and the 25% drainage time was 240 s, extinguishing time was 30 s, burn-back time was 760 s.