Surfactant Sodium Dodecyl Sulfate Research Articles

Gas-liquid interface properties of fluorocarbon and hydrocarbon surfactants and their mixed foams: Molecular dynamics simulations and experimental studies

This paper focuses on the gas-liquid interface characteristics of short-chain fluorocarbon surfactant FS-50 and hydrocarbon surfactant sodium dodecyl sulfate (SDS) and their mixed systems. The foam properties of SDS, FS-50, and their mixed solutions were experimentally determined. Then, based on the molecular dynamics simulation method, the interaction mechanism of surfactant molecules at the gas-liquid interface was simulated and analyzed by constructing a foam-liquid membrane system containing surfactant molecules and water molecules. The experimental results show that FS-50 can effectively enhance the foam stability when the concentration is lower than 0.16 wt% and the mixing ratio with SDS is not more than 1:1; the simulation results show that FS-50 can change the arrangement of SDS molecules at the gas-liquid interface. Simultaneously, there is a competitive adsorption phenomenon between FS-50 and SDS at the gas-liquid interface. The low mixing ratio FS-50 can increase the thickness of the gas-liquid interface of the mixed system and the ability of SDS to form hydrogen bonds with water, enhance the water-locking ability of SDS, and further improve the stability of the foam liquid film. The interaction mechanism between short-chain fluorocarbons and SDS surfactants at the gas-liquid interface was revealed by simulation, which provided theoretical guidance for optimizing the performance of the foam liquid film.

Investigation of the synergistic effects of SiO2 and Al2O3 nanoparticles with SDS and CTAB surfactants on the stability and improving phase behavior of water-oil emulsions

The stability of emulsions is a significant challenge across various industries, including food, pharmaceutical, and petroleum. Surface-active agents utilized for enhanced oil recovery often exhibit inadequate performance under high salinity reservoir conditions, presenting a critical barrier to effective emulsion stabilization. Furthermore, due to the extreme hydrophilic or hydrophobic nature of nanoparticles (NPs), they are not effective in stabilizing emulsions on their own. To address this limitation, a minimal quantity of surfactant was introduced into the NPs to improve their wettability and achieve dual wettability. This research has examined the synergistic effects of SiO₂ and Al₂O₃ NPs combined with sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) surfactants on water-oil emulsion stability. This approach enhanced emulsion stability by combining the stabilizing effects of both the NPs and the surfactants, an aspect that has not been previously addressed in phase behavior studies through the examination of the interactions and surface behavior of surfactant-nanoparticle complexes at the oil-water interface. Several experiments, including phase behavior, FT-IR, zeta potential, contact angle, and interfacial tension (IFT) tests, were performed to evaluate the interaction of surfactants with NPs. The results demonstrate that combining NPs with surfactants, especially those with opposite charges, significantly reduces IFT to the order of 10−6 mN/m, which can overcome capillary pressure, and enhances optimal salinity levels even up to 75000 ppm. Interactions between CTAB-SiO₂ and SDS-Al₂O₃ notably improve the hydrophobicity of NPs, resulting in IFT reductions of 11.4 and 7 mN/m, respectively, compared to NPs alone.

Anthraquinone Schiff base and SDS-based visual detection for environmental safety: Targeting triphosgene and Hg2+ with secondary focus on detection of BSA

New sensing techniques with exceptional performance, i.e., high sensitivity, high selectivity, and dependability, are needed to meet the growing demand for quick and accurate environmental pollution prevention and monitoring. A novel Schiff base probe synthesized from anthraquinone and 4-(diethylamino)-2-hydroxybenzaldehyde (coded as AQHB) was synthesized and subsequently combined with anionic surfactant Sodium dodecyl sulfate (SDS) assemblies to form highly fluorescent AQHB@SDS ensemble. The zeta potential of ensemble AQHB@SDS is −52.6 mV confirm the encapsulation of AQHB (-17.3 mV) in SDS micelles. This formed fluorescent AQHB@SDS ensemble further practical applications in detection of toxic triphosgene and Hg2+ ions via naked eye color change and fluorescence quenching mechanism. The fluorescence of in-situ formed AQHB@SDS+Hg2+ complex restored by the addition of BSA. The optimized system demonstrates detection limits of 0.60, 0.68, and an impressive 0.028 nM for triphosgene, Hg2+, BSA respectively. Control experiments revealed that the -OH and -NH groups in AQHB along with anionic surfactant played crucial roles in the sensing mechanism. Moreover, the ensemble AQHB@SDS system efficiently detected triphosgene and Hg2+ in real samples, such as water and soil, highlighting its practical applicability.

Effect of ultrasonication time on the performance of carbon black water nanofluid in solar absorption

This research reveals an innovative way of finding the ultimate time of ultrasonication that offers photothermal capability across carbon black (CB) water nanofluids, a great contribution to the field of solar energy absorption and nanofluid technology. The samples were generated using a two-step procedure with varying ultrasonication periods employed, ranging from 15 to 120 minutes, in concentrations of 0.005 wt% CB nanoparticles and 0.005 wt% sodium dodecyl sulfate (SDS) surfactant. Thirty days after preparation visible observation and UV spectroscopy, scanning electron microscopy (SEM) images, and particle size distribution were used to confirm the samples’ stability. The stability properties results demonstrated the beneficial effects of ultrasonication on the dispersion properties of nanofluids. Ultrasonication of less than 30 minutes resulted in the early sedimentation of nanoparticles. According to the results, the investigated nanofluids have high photothermal conversion capability with ultrasonication time. According to the findings, 30 minutes is the “optimal” ultrasonic duration to maximize photothermal conversion efficiency.

Emulsification and interfacial characteristics of different surfactants enhances heavy oil recovery: experimental evaluation and molecular dynamics simulation study

The high viscosity and poor fluidity of heavy oil challenge its extraction, leading to the widespread use of surfactant emulsification to reduce viscosity and enhance recovery. This study evaluated three surfactants—sodium dodecyl sulfate (SDS), sodium oleate (SO), and APG0810—for their suitability and effectiveness in the X reservoir. The solution properties of these surfactants were analyzed and their micro-mechanisms investigated using MD calculations. The effects of surfactant concentration and additives on emulsification and viscosity reduction were elucidated. Ultimately, a system for emulsification and viscosity reduction was selected for physical simulation research. The experimental findings show that SO reduces interfacial tension from 52.4 mN/m to 0.0027 mN/m, transforming lipophilic surfaces into hydrophilic. MD analyses reveal SO’s optimal interfacial properties, with the lowest interfacial energy of −6423.4 kcal/mol, maximum interfacial thickness of 2.56 nm, and minimal diffusion coefficient of 0.4087 Å2/ps at the oil-water interface. These findings align with experimental results, confirming SO’s superior interfacial properties. Combining 0.3% SO with 0.5% n-pentanol results in a 98% viscosity reduction. The emulsion shows excellent stability, with no water separation in the first 30 min and only 8.3% after 2 h. Physical simulation results show that in high(low) permeability core displacement experiments, system flooding and subsequent water flooding can increase recovery rates by 15.39%(36.91%), indicating the system’s potential for enhancing oil recovery in Reservoir X. The findings suggest that the implementation of this system not only boosts the crude oil recovery rate but also carries economic significance in the industry.

Retention Mechanisms of Basic Compounds in Liquid Chromatography with Sodium Dodecyl Sulfate and 1-Hexyl-3-Methylimidazolium Chloride as Mobile Phase Reagents in Two C18 Columns

Reversed-phase liquid chromatography (RPLC) relies on a non-polar stationary phase and a more polar hydro-organic mobile phase, where compound retention is primarily governed by hydrophobicity, with more hydrophobic compounds being retained longer. The introduction of secondary equilibria in the chromatographic system through additives, such as anionic surfactants and ionic liquids (ILs), was proposed to mitigate ionic interactions between positively charged analytes and the anionic free silanol groups in non-endcapped stationary phases, thereby preventing increased retention and peak tailing. Additionally, the combined hydrophobic and ionic interactions between cationic analytes and the ions in these additives was demonstrated to create mixed retention mechanisms that influence retention and selectivity. In this regard, this study investigates aqueous chromatographic systems incorporating both the anionic surfactant sodium dodecyl sulfate (SDS) and the IL 1-hexyl-3-methylimidazolium chloride as mobile phase reagents. This combination of reagents modulates the retention, eliminating the need for organic solvents and resulting in highly sustainable HPLC procedures. The chromatographic behavior was assessed using two different C18 columns (Zorbax Eclipse and XTerra-MS). The strength of solute interactions was estimated by calculating equilibrium parameters and the contributions of hydrophobic and ionic interactions through simple mathematical models. Focusing on the retention of six basic drugs (β-adrenoceptor antagonists), the study highlighted the significant role of ionic interactions. The results demonstrate the feasibility of using aqueous systems combining SDS and an IL for the efficient separation of moderately polar basic compounds without the use of organic solvents.

Low-Foaming Nonionic Gemini Surfactants Containing Hydrophilic Poly(oxyethylene) Chain and Hydrophobic Di-tert-pentylbenzenes Groups.

Low-foaming nonionic gemini surfactants have a wide range of applications in industrial cleaning and photoresist development. In this study, three low-foaming nonionic gemini surfactants (S1, S2, and S3) with different poly(oxyethylene) chain lengths have been synthesized by using methoxy poly(ethylene glycol) and 2,5-di-tert-pentylhydroquinone. The chemical structures of the novel surfactants are confirmed by 1H NMR, Fourier transform infrared, and gel permeation chromatography (GPC), and their properties such as surface tension, wetting properties, emulsifying properties, and foaming properties are investigated. The surface tension values of S1, S2, and S3 at the critical micelle concentration are 40.29, 37.14, and 41.64 mN/m, exhibiting good surface activity. When the surfactant concentration is higher than 2 mM, the contact angles of S1 and S2 no longer change and can maintain 62 and 64°, showing good wetting properties. In addition, S3 can keep an emulsion state for 2 months at high concentrations, exhibiting good emulsion stability. Furthermore, all the prepared surfactants show good low-foaming properties. The initial foaming volumes of S1 are very low, less than 0.1 mL at various concentrations, less than 2% of the conventional surfactant sodium dodecyl sulfate. For S2, the initial foaming volumes at the concentration of 0.1, 1, 2, and 3 g/L are 1, 0.5, 0.55, and 0.45 mL, respectively. For S3, the initial foaming volumes show a general trend of increasing with concentration. The surfactants with longer poly(oxyethylene) chains possess more initial foaming volumes at the same concentration, which is because the greater cohesion between the surfactant molecules can increase the elasticity of the bubble film. Our study enriches the design rationales for low-foaming surfactants and motivates researchers to develop more advanced surfactants for industrial cleaning and photoresist development.

The Dynamic Impact of Synthetic Dyes on the Physicochemical Parameters of Cationic and Anionic Surfactants

Introduction: The interaction of dyes (crystal violet, malachite green, and congo red) with cationic (cetrimide) and anionic surfactants (sodium dodecyl sulfate) in the aqueous medium were studied via conductometric and UV-visible spectroscopy. Method: The critical micelle concentration (CMC) of both cetrimide and SDS upsurges in all the selected dyes on increasing the temperature. Thermodynamic parameters like change in Gibb’s free energy of micellization (Δ G°m ), change in enthalpy of micellization (Δ H°m ) as well as change in entropy of micellization (Δ S°m ) were calculated by employing mass action model. Result: The Δ S°m values obtained are positive with Δ G°m and Δ H°m values being negative signified that the phenomenon of micellization is spontaneous as well as exothermic in nature. Moreover, the more negative Δ H°m in water as well as in the presence of dyes signify the presence of electrostatic forces of attraction between the oppositively charged dyes and surfactant moieties. UV-spectroscopy reveals that spectral changes occur because of the interaction of surfactants with dye molecules. Conclusion: By analyzing shifts in absorption peaks, changes in intensity, and alterations in band shape, insights into the nature of surfactant-dye complexes and their potential applications in various industries can be assessed. This understanding can help in the design and optimization of products and processes involving surfactants and dyes.

Tailoring polypyrrole morphology and electronic properties through CTAB-SDS self-assembly

This study explores the polymerization of polypyrrole (PPy) within a self-assembled catanionic surfactant composed of cetyltrimethylammonium bromide (CTAB) - sodium dodecyl sulfate (SDS), aiming to control its morphology and electronic properties. The research systematically investigates how varying the compositions of CTAB and SDS surfactants influence the structural and electronic characteristics of PPy. Our findings indicate that the surfactant composition predominantly impacts the shape of PPy rather than its crystallinity. Despite the absence of significant crystallinity, variations in surfactant composition notably alter the electronic properties of PPy. Specifically, an increase in CTAB content results in electrical conductivity increasing from 0.34 to 0.01 S/m. Conversely, higher SDS content enhances the bipolaron-to-polaron ratio, particularly in the C−H deformation region, contributing to improved electronic characteristics. Additionally, packing density analysis reveals that the ordered or disordered acyl chain arrangement within the catanionic surfactant system varies significantly with surfactant composition, further influencing the morphology and electronic properties of PPy. These findings provide valuable pave for designing conductive polymers with tailored electronic properties by a catanionic surfactant, where precise control over such properties is crucial.

Investigating the interactions between an industrial lipase and anionic (bio)surfactants

In laundry formulations, synergies between amphiphiles and other additives such as enzymes increase sustainability through a large decrease in energy consumption. However, traditional surfactants are derived from petroleum, requiring chemical modifications (sulfonation, ethoxylation, or esterification) and generating environmental pollution through toxicity and low degradability. Use of biosurfactants removes these issues. To provide a firmer basis for the use of biosurfactants, we report on the interactions between the industrial lipase LIPEX® and three common biosurfactants, rhamnolipids, sophorolipids, and surfactin. The model surfactant sodium dodecyl sulfate (SDS) is included in the study for comparison. A thorough characterization by Small-angle X-ray scattering (SAXS) provides valuable information on the enzyme’s oligomerization and the surfactant micelles’ ellipsoidal morphology. Additionally, the enzymatic activity and complex formation in different surfactant mixtures are studied using isothermal titration calorimetry, activity assays, and SAXS. SDS activates the enzyme while promoting a controlled association of monomers while the biosurfactants inhibit the enzyme, independent of their effects on its quaternary structure. Rhamnolipids and surfactin promote lipase dimerization while sophorolipids have no significant effect on lipase quaternary structure. Based on these data, we propose a partial replacement that allows the enzyme to retain enzymatic activity while improving the environmental footprint of the formulation.

Effect of percentage of methanol on micellization position of mixed surfactant interaction in the absence and presence of dye

The interaction behavior of mixed surfactant-dye systems, i.e., anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl pyridinium chloride (CPC), and dye methyl orange (MO) was investigated through the allocation of micelles using conductivity measurements. Conductivity as a function of surfactant concentration was monitored to calculate the critical micelle concentration (CMC). The conductivity increased sharply as the surfactant content increased, according to the results. Moreover, the conductivity rises with temperature, whereas it falls with increased methanol (CH3OH). CH3OH-H2O mixed solvent media containing 0 %, 10 %, 20 %, and 30 % of CH3OH at 298.15, 308.15, and 318.15 K to work out the basic micelle fixation, gives significant understanding to the arrangement of the mixed surfactants. The CMC and degree of micellar dissociation (α) of SDS with CPC increase in the CH3OH and H2O mixture. The CMC and α values are increased by increasing the temperature. Various thermodynamic parameters, i.e. Standard free energy of micellization (ΔGmo), Standard enthalpy of micellization (ΔHmo), and Standard entropy of micellization (ΔSmo) were computed in SDS-CPC without MO. ΔGmo values for SDS-CPC in the presence of MO results in micellization more probable with MO.

Exploring Photophysical Properties of Organic Doped Polymeric Aggregates for Detecting Relevant Inorganic Pyrophosphate: A Pathway to Sustainable Development

Pyrophosphate (PPi) is an important environmentally and biologically relevant analyte and its easy and efficient detection is crucial for sustainable development. So, here we designed and synthesized organic-doped polymeric aggregates varying the signaling units (pyrene and anthracene) and examined their photophysical properties. By altering the signaling unit while keeping the polymeric backbone intact, we observed aggregate changes and studied their optical response with inorganic pyrophosphate (PPi). Among these probes, PYR-PEI exhibited a superior turn-off response(~6.1-fold) towards PPi in aqueous media whereas the other two probes ANH-PEI and PYR-PAH showed less response. The distinct response to PPi was primarily determined by electrostatic interaction and aggregate nature. The limit of detection (LOD) for PPi using the PYR-PEI probe was found to be 4.2 ppm, which is below the maximum allowable concentration of phosphate in surface water set by the World Health Organization (WHO) at 5mg/l. The quantification limit (LOQ) for PPi sensing was observed to be 14.27 ppm. Additionally, the PYR-PEI probe showed different fluorogenic responses (ratio-metric change) in the presence of anionic surfactant sodium dodecyl sulfate (SDS), and this resultant adduct was used for the PPi detection. The formation of premicellar aggregates between them drove the difference in the fluorogenic response with PYR-PEI and surfactant. Then the PYR-PEI composite was employed to detect PPi in spiked soil solution. Finally, chemically modified paper strips were prepared for the easy, fast, and on-location detection of PPi present in real-life samples.

Synergistic enhancement of oil recovery: Integrating anionic-nonionic surfactant mixtures, SiO2 nanoparticles, and polymer solutions for optimized crude oil extraction

Enhanced oil recovery (EOR) methods are essential for optimizing oil extraction from modern reservoirs. This research delved into the synergistic impact of combining anionic and nonionic surfactant mixtures with silica (SiO2) nanoparticles (NPs) in sodium chloride (NaCl) solutions, alongside the added enhancement of polymers, to improve crude oil recovery. The study comprehensively evaluated stability, rheological characteristics, interfacial tension (IFT) behavior, wettability alterations, and EOR experiments using mixtures of sodium dodecyl sulfate (SDS) and triton X-100 (TX-100) surfactants. Scenarios both with and without SiO2 NPs in a base solution containing 3000 ppm NaCl and 2000 ppm xanthan gum (XG) polymer were examined. Core flooding tests were carried out on San-Saba sandstone core specimens with low permeability. The stability tests and dynamic light scattering (DLS) analysis were performed to assess the stability of NPs in low saline-surfactant-polymer solution. It was observed that NPs significantly reduced the IFT between the test solutions and crude oil, with nanofluids exhibiting satisfactory stability at a 0.4 wt% SiO2 NPs concentration. Core flooding studies demonstrated a synergistic interaction between NPs and the binary surfactant-polymer mixture, resulting in substantially greater incremental recovery of oil in comparison with the case of using binary surfactant-polymer combination alone. The mechanisms contributing to EOR with nanofluids, such as IFT reduction and wettability alteration, were explored. Incorporating NPs at concentrations of 0.1, 0.2, and 0.4 wt% led to incremental oil recoveries of 4.01 %, 12.35 %, and 12.73 % of the original oil in place (OOIP), respectively, as opposed to the recovery achieved using only SDS + TX-100 + XG. Consequently, these findings advance the understanding of the potential application of SiO2 NPs in combination with the binary surfactant-polymer mixture as effective chemical EOR agents. Additionally, these insights aid in identifying suitable sandstone reservoirs for nanofluid application, contributing to the optimization of oil recovery strategies.

Effect of surface charge on laser-produced silver nanoparticles for dye reduction and surface-enhanced Raman spectroscopy

Silver nanoparticles (Ag NPs) are widely used in biological, chemical, and physical fields due to their distinct properties. However, the effect of surfactants with different polarities on the catalytic and surface-enhanced Raman spectroscopy (SERS) performance of Ag NPs has not been thoroughly studied. Here, we tailor the surface charge of laser-synthesized Ag NP without changing their morphology and investigate their catalytic and SERS capabilities. The surfactant-free silver nanoparticles (NPBare), synthesized via pulsed laser ablation in liquid (PLAL), are subsequently coated with ionic surfactants sodium dodecyl sulfate (NPSDS) and cetyltrimethylammonium bromide (NPCTAB). The synthesis and morphology of Ag NPs are confirmed using UV-Vis absorption spectroscopy and scanning electron microscopy. The surface charge of fabricated NPs is determined using zeta potential (ZP) measurements. The ZP values of NPBare, NPSDS, and NPCTAB are determined to be -17 mV, 28.7 mV, and 5.58 mV, respectively. The catalytic activity of bare and coated Ag NPs was tested against the cationic and anionic dyes, Methylene blue (MB) and Methyl orange (MO) respectively. The reduction rate of both dyes was highest when using NPBare. However, in the case of coated nanoparticles, the rate of MB and MO reduction depends on the difference between the ZP of the dye and nanoparticles: the rate of reduction increases with the difference between the zeta potentials of the dye and coated nanoparticles increases. The SERS capability of bare and coated NPs was evaluated for anionic (MO) and cationic (MB, Rhodamine B, and Crystal Violet) dyes. The SERS intensity of dyes strongly enhanced with the increase in ZP difference between the dye molecules and NPs. Surface charge modified NPs shown excellent SERS sensitivity with detection limit up to nanomolar for dye molecules as well as the homogeneity of NPs demonstrated in Raman mapping results with relative standard deviation of 17%. The results suggest that the electrostatic interaction between the nanoparticles and dye molecules plays a dominant role in SERS enhancement. These findings highlight the significance of surface charge in improving the catalytic and sensing properties of noble metal nanoparticles.

Mechanism of dust suppressant by sodium carboxymethyl cellulose grafted acrylic copolymer

In order to inhibit dust, a substance C-PAA was synthesized by free radical polymerization using sodium carboxymethyl cellulose and acrylic acid as raw materials and ammonium persulfate as an initiator. The optimal synthesis process was determined by using a single factor experimental method. Quantum chemistry and experiments were used to investigate the chemical synthesis of C-PAA. The results indicate that the active centers of the reaction were at the OH bond of sodium carboxymethyl cellulose, where H was seized by ·SO4-, produced by ammonium persulfate, to form an alkoxyl radical. Concurrently, ·SO4- attacked acrylic acid, resulting in the breakage of the CC bond, creating a CC bond, and combining with the alkoxyl group to create a new ether group that produced the compound C-PAA. The enthalpy change and activation energy of the reaction were −178.40 KJ/mol and −22.59 KJ/mol, respectively, and the infrared absorption peaks of the newly generated fatty ether and the increase in the relative content of the ether group in the final product proved that the preparation of C-PAA was successful. In order to further improve the wetting performance of the dust suppressant, pyrene fluorescence spectrometry was used to determine the critical micelle concentration of the surfactant sodium dodecyl sulfate as 1.5 g/L, and 1.5 g/L sodium dodecyl sulfate was mixed with C-PAA to obtain the dust suppressant SC-PAA. In comparison to the H2O-lignite system, the total number of hydrogen bonds in the SC-PAA-lignite system increased from 2023 to 2405, according to the molecular dynamics results. The rationale is that C-PAA in SC-PAA has a plethora of oxygen-containing functional groups, which enable it to create more hydrogen bonds with H2O as well as amino and hydroxyl groups on the surface of lignite. Due to hydrogen bonding, the dust suppressant is able to gather more water molecules adsorbed on the surface of the lignite. It then utilizes the capillary force of the coal pores to penetrate deeply into the fissures within the coal particles, thereby enhancing the wetting impact on the lignite.

Influence of Sodium Lauryl Sulfate Anionic Micelles on the Complex Equilibria of Divalent Metal Ions with Isoleucine Amino Acid

The main objective of the present investigation is the formation analysis of metal-ligand complexes of isoleucine with divalent calcium, magnesium and zinc metal ions in various concentrations of sodium dodecyl sulphate (0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 percent w/v). To look into the impact of the concentration of negatively charged micelles, the parameters were changed and the possible chemical species of isoleucine that interact with the metal ions, are being studied. The experiment was performed using pH meter at 303 K using NaCl to keep ionic strength stable at 0.16 mol dm-3 in the presence of anionic surfactant sodium dodecyl sulphate (SDS). The determination of the correction factor was conducted via the computer program SCPHD. The computational software MINIQUAD75 is utilized to determine the stability constants of ligand-metal complexes through the analysis of titration data. Based on statistical features such as skewness, 2, kurtosis and crystallographic R-factor, the best fit to the complicated speciation was selected. The metal ions Ca (II), Mg (II) and Zn (II) formed complexes ML, ML2 and ML2H2 for Ca (II), Mg(II) and ML, ML2 and ML2H for Zn (II) through the complexation of isoleucine. In order to validate the accuracy of the final established model, deliberate defects were introduced into the relevant components.

Stability mechanism of viscoelastically enhanced surfactant air foam for low permeability reservoir

Polymer has been widely studied as an effective means to improve foam stability in reservoir exploitation. Nevertheless, the deployment of this technology in low-permeability reservoirs may prove challenging and could potentially result in formation damage. The innovation of this study is the utilization of viscoelastic surfactants to create enhanced air foam with wormlike micelles and three-dimensional network structures. This can result in a synergy between the properties of fluidity control and oil washing efficiency, thereby enhancing the strength of the foam. The supramolecular self-assembly property facilitates the injection of the foam into the formation while preserving its original structure and properties, thereby enhancing the stability of the foam and markedly improving the recovery of low permeability reservoirs. The viscoelastically enhanced air foam system is composed of the zwitterionic surfactant erucylamido propyl betaine (EHSB) and the anionic surfactant sodium dodecyl sulfate (SDS), which has been designated EHSB-SDS. The foam performance was evaluated using the Waring Blender method and rheological behavior, with foam fluid viscosity, initial foam volume (V0), half-life for drainage (td) and foam half-life (tf) serving as the evaluation indicators. The influence of temperature, salinity and oil content on foam performance is considered to explore the reservoir adaptability. The dynamic/micro stability, macro rheological properties, interfacial viscoelasticity and Zeta potential of the enhanced air foam system were further studied to clarify the stability mechanism of enhanced air foam system. The td, tf and composite index of EHSB-SDS is 56.6 min, 36 h and 648000 mL·min, respectively. The viscoelastic surfactants form wormlike micelles, which increase the foam solution viscosity. This results in a slow drainage speed and the rupture of the bubbles. The adsorption of surfactant at the gas/liquid interface results in an increase in surface activity, interfacial expansion modulus and zeta potential, which serves to enhance the strength of the liquid film and the electrostatic repulsion among bubbles. These three factors are primarily responsible for the stability of the foam. The research establishes a theoretical basis for the effective development of low permeability reservoirs and new foam flooding technology.

Solvent-induced modulation of sensitivity and selectivity in the self-assembly of tetracationic cyclophanes with cholesterol sulphate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate: Observations of significant shifts

Cyclophane CP-1 demonstrates markedly distinct sensitivities toward Cholesterol sulfate (CH-S), Sodium Dodecyl Sulfate (SDS), and Sodium Dodecyl Benzene Sulfonate (SDBS) when the solvent is shifted minimally from a 95 % to a 98 % HEPES-DMSO mixture. In a 98:2 HEPES-DMSO mixture, CP-1 engages in highly selective self-assembly with CH-S, which is characterized by aggregation-induced emission enhancement (AIEE) in contrast to other steroidal sulfates such as pregnenolone sulfate (PRG-S), dehydroisoandrosterone sulfate (DIAND-S), taurocholic acid (TACH-S), and the surfactants SDS and SDBS. This assembly results in an approximate 40-fold increase in fluorescence intensity with three equivalents of CH-S and allows for the detection of concentrations as low as 200 nM under physiological conditions. Dynamic light scattering (DLS) studies illustrate the aggregation of CP-1 and CH-S, with the zeta potential of each shifting from negative values to nearly zero in a 1:2 CP-1:CH-S mixture, indicating self-assembly. This aggregation behavior is reversible, as demonstrated by a corresponding decrease and then increase in fluorescence intensity with temperature variations from 25 °C to 70 °C and back to 25 °C. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses show that CP-1 forms aggregates ranging from 100 to 180 nm, which increase to 150–250 nm upon interaction with CH-S. In a 95:5 HEPES-DMSO mixture, CP-1 exhibits a stronger AIEE response with SDS and SDBS compared to CH-S. Cyclophane CP-2, when dissolved in binary DMSO-water mixtures with water content exceeding 80 %, shows similar AIEE phenomena and undergoes selective fluorescence quenching with SDS and only a 50 % increase in fluorescence intensity with CH-S, irrespective of the HEPES concentration (95 % or 98 %).

Monolayer instability of ionic surfactants at the water/air interface due to biosurfactant molecules: A molecular dynamic approach

The decomposition of monolayers prepared with anionic surfactants, sodium dodecyl sulfate (SDS), or cationic ones, dodecyltrimethylammonium bromide (DTAB), at the water/air interface was studied when biosurfactants (surfactin) are added to the films. Molecular dynamics simulations were carried out for monolayers with a fixed number of SDS or DTAB molecules and a different amount of biosurfactants to form SDS/surfactin and DTAB/surfactin mixtures. It is found that the presence of the biosurfactant modifies interfacial and structural properties of the ionic monolayers at the interface; the DTAB monolayer is distorted even for a few surfactin molecules, whereas the SDS monolayer remains steady up to a given amount of biosurfactant. In both monolayers the surface tension decreases with the number of biosurfactants, however while for the DTAB/surfactin the values seem to fluctuate, for the SDS/surfactin mixture the values decay linearly, with a discontinuity for a given surfactin concentration. The linear behaviour of the surface tension for the SDS/surfactin allows us to evaluate free energies for the monolayers and a two-dimensional equation of state. The structure of the monolayers was analyzed in terms of density profiles, order parameters, thickness of the interfaces and the data show that the DTAB/surfactin is more distorted than the SDS/surfactin by the presence of few surfactin molecules. The results indicate that SDS surfactants are more likely to form longer lasting films with fewer surfactin molecules than DTAB.

Hydrophilic surface-modified titanium-based lithium ion sieve adsorbents for efficient lithium extraction

Titanium-based lithium ion sieve adsorbents (HTOs) are considered among the most promising materials for lithium extraction from aqueous sources. In this study, four surfactants—sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), hydroxypropyl cellulose (HPC), and tannic acid (TA)—were used to surface-etch HTOs, preparing adsorbents with enhanced hydrophilicity at the nanoscale. Correlation studies between the hydrophilicity of the HTO-X and their adsorption performance revealed that all HTO-X had lower contact angles than the unetched counterparts, indicating improved adsorption capacities. Notably, TA plays a synergistic role of “killing two birds with one stone”. The TA-etched HTO-T adsorbent exhibited the lowest contact angle (8.8°) and the highest specific surface area (62.10 m2/g). In a LiCl solution, HTO-T’s adsorption capacity for Li+ reached 33.61 mg/g, a 26 % increase over the unetched HTO adsorbent (26.56 mg/g). Simultaneously, HTO-T significantly reduces the adsorption time and enhances the adsorption efficiency during the surface diffusion phase. Additionally, HTO-T demonstrated remarkable selectivity for lithium ions, with separation factors α(Li/Na), α(Li/K), α(Li/Mg), and α(Li/Ca) of 397.13, 181.55, 1288.47, and 1345.19, respectively, showcasing an excellent separation effect. The adsorption mechanism indicates that Li+ adsorption by HTO-T primarily occurs through the disruption of O–H bonds and the formation of new O-Li bonds. This research presents an efficient strategy for the development of HTOs, demonstrating HTO-T as a potential adsorbent for lithium recovery from brine sources.