Aqueous Surfactant Solutions Research Articles

Triglyceride mixtures: Cold-bursting and double emulsion formation

It was shown recently that a solid-to-solid phase transitions (α-to-β, gel-to-crystal), typical for many lipid substances, can lead to formation of nanoporous network inside lipid micro-particles dispersed in aqueous surfactant solutions (Cholakova et al. ACS Nano2020, 14, 8594). These nanopores are spontaneously infused by the aqueous phase when appropriate combination of water-soluble and oil-soluble surfactants is applied. As a result, the initial lipid micro-particles can spontaneously burst into much smaller nanoparticles, just by cooling and heating of the initial dispersion. Under certain conditions, the infused aqueous phase is entrapped in the moment of lipid particle melting and double emulsion of type water-in-oil-in-water (W/O/W) is formed. The current study aims to clarify how the composition of the lipid micro-drops and surfactants affect the observed phenomena. Selected mixtures of monoacid triglycerides are studied systematically. The results show that the bursting efficiency usually decreases when the complexity of the lipid mixture increases, due to the expanded temperature interval for lipid melting. Nevertheless, complete particle bursting and lipid nanoparticles with diameters down to 20 nm are formed even for the most complex lipid compositions under appropriate conditions. The key mechanisms leading to efficient fragmentation and double emulsion formation are clarified, and the main governing factors are explored. On this basis, we reveal that the system behavior can be switched between complete particle bursting and W/O/W emulsion formation by: (1) Change in the cooling and heating rates without any changes in the chemical composition, (2) Change in the concentration of oil-soluble surfactant, and/or (3) Change in the phase in which the oil-soluble surfactant is introduced initially. Thus, we have formulated guiding rules to control the formation of lipid nanoparticles and W/O/W emulsions with triglyceride mixtures promising multiple potential applications.

Polymer and surfactant flows through a periodically constricted tube

The flow of three non-Newtonian fluids, comprising polymer and surfactant additives, in a periodically constricted tube (PCT) are experimentally compared. The radius of the tube walls is sinusoidal with respect to the streamwise direction. The three fluids are aqueous solutions of flexible polymers, rigid biopolymers and surfactants, which are typically used for drag-reduction in turbulent flows. Steady shear viscosity measurements demonstrate that rigid and flexible polymer solutions are shear-thinning, while surfactant solutions have a Newtonian and water-like shear viscosity. Capillary driven extensional rheology demonstrates that only flexible polymer solutions produce elastocapillary thinning. Particle shadow velocimetry is used to measure the velocity of each flow within the PCT at five Reynolds numbers spanning roughly 0.5 to 300. Relative to the Newtonian flows, rigid polymer solutions exhibit a blunt velocity profile. Flexible polymer solutions demonstrate a distinct chevron-shaped velocity contour and zones of opposing vorticity when the Deborah number exceeds 0.1. Using the vorticity transport equation, it is revealed that the opposing vorticity zones are coupled with a non-Newtonian torque. The PCT reveals that the surfactant solutions have similar non-Newtonian features as flexible polymer solutions – those being a chevron velocity pattern, opposing vorticity and a finite non-Newtonian torque. This observation is of practical importance since conventional shear and extensional rheometric measurements are not capable of demonstrating non-Newtonian features of the surfactant solutions. The investigation demonstrates that the PCT serves as a viable geometry for showing the non-Newtonian traits of dilute surfactant solutions.

Preparation of a new polymeric surfactant and its thickening of the Linear Alkylbenzene Sulfonate system

HypothesisIn general, the viscosity of aqueous surfactant solutions is low and does not meet the elevated viscosity operating requirements of some practical applications. Inorganic salts are the most widely used thickeners, but they are not suitable for all application systems, such as the Linear Alkylbenzene Sulfonate (LAS) system. Polymer thickeners are comb-like compounds with many hydrophobic groups. These groups in solution through intermolecular forces form a network, increasing the viscosity of the system. In addition, non-ionic surfactant fatty alcohol polyoxyethylene ether has an excellent surface activity. If the product is combined with surfactants and polymers, it is possible to increase the viscosity of the system without degrading the application performance. ExperimentsA new type of polymeric surfactant (P-AA-AEO9) with thickening properties was synthesized by fatty alcohol polyoxyethylene ether (AEO9) and acrylic acid (AA). The structure and molecular weight of P-AA-AEO9 were determined by Gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy. The surface properties of P-AA-AEO9 were investigated by the Krüss K12 surface tension meter and the Krüss bubble pressure tensiometer. Moreover, the thickening properties of the P-AA-AEO9 and the LAS/P-AA-AEO9 mixed solution was studied by rheology. FindingsP-AA-AEO9 can be used as a thickener for LAS systems. In addition, the viscosity of the LAS/P-AA-AEO9 mixed solution can be increased, thereby maintaining an excellent application performance of LAS.

Xanthate degradation at neutral and basics pH by Cu-Fenton-like process

Even residual concentrations of xanthates in copper mining wastewater can make the water toxic, preventing it from being reused and returned to rivers. Fenton and Photo-Fenton process for xanthate degradation has been explored, but its acidic pH condition is a limiting factor. The present paper study the Copper-Fenton-like process for the degradation of xanthate surfactant in aqueous solutions at an initial neutral and basic pH. This work was divided into three parts: Characterization of the surfactant’s samples using Fourier transform infrared spectroscopy; Degradation studies using the copper-Fenton reaction, where process parameters were studied (Catalyst and surfactant concentration and pH) simulating the tailing ore conditions, and the parameter, hydrogen peroxide concentration, were optimized for enhancements of TOC degradation values; Proposal of a kinetic model of degradation, both first and second order kinetic model were tested. The results demonstrate that at an initial concentration of 100 mg/L of sodium isobutyl xanthate (SIBX), the process can achieve up to 99 % degradation of SIBX after 120 min, with a total organic carbon (TOC) reduction of over 80 %. The degradation of SIBX follows a 1st and 2nd order kinetic model, consistent with previous studies. At an initial concentration of 10 mg/L for both SIBX and potassium amyl xanthate (PAX), close to complete degradation was achieved in 120 min. Overall, the results suggested the potential of the Cu-Fenton-like process for treating xanthate-contaminated wastewater, providing a cleaner and more sustainable alternative to conventional methods.

The study on the dielectric properties of structural changes of surfactant aqueous solution by molecular dynamics simulation

Dielectric constant is an important physical and chemical property of liquid in regulating solute–solvent interaction and solvation microstructure. Herein this work deals with the procedure for calculating dielectric property based on the raw data of molecular dynamics (MD) simulation. The fluctuations of the dipole moment and current which are obtained from MD can be directly related to the frequency-dependent permittivity. In this article, we have taken the sodium dodecyl sulfate (SDS) aqueous micelle system containing free charges as an example, and the dielectric behavior of micellar systems with different structures were studied. In the high frequency range, the response of positive and negative ions is shielded due to the intrinsic dipole moment polarization of the molecule. At low frequencies, the static dielectric constant can reveal the microstructral transformation of the micelles properly. Our results show that the dielectric constant is closely related to the atomic structure of the micelles, and the static dielectric constant could serve as an important method to determine the microscopic phase change process.

Water-Soluble Dicationic Deuteroporphyrin Derivative for Antimicrobial PDT: Singlet Oxygen Generation, Passive Carrier Interaction and Nosocomial Bacterial Strains Photoinactivation

Multidrug resistance of pathogenic microflora is a serious threat to the modern community looking for new approaches to treating superinfections. In this sense, antimicrobial photodynamic therapy (aPDT) is an effective and safe technique considered to be a promising alternative or an important supplement to the traditional clinically applied methods for inactivating antibiotic resistant pathogens. Macroheterocyclic photosensitizers (PS) of three generations are proposed for clinical practice. They are known as the key compounds for PDT able to be localized selectively in microbial cells and to be activated with the red light producing toxic reactive oxygen species (ROS). However, these neutral and anionic PSs possess low affinity towards the outer lipopolysaccharide membrane of Gram-negative bacteria and, consequently, poor ability to kill these pathogens under irradiation. In contrast, cationic PSs containing one or more charged groups, especially those bound to an appropriate carrier, provide efficient inactivation of microorganisms. In this paper, we focus on the study of photophysics, aggregation and photoinduced antimicrobial activity of the water-soluble derivative of deuteroporphyrin-IX, a blood group porphyrin, bearing two cationic trialkylammonium fragments. This potential photosensitizing agent is found to generate singlet oxygen in a non-polar environment and forms stable nano-sized molecular complexes with passive non-ionic carrier Tween 80, localizing in an aqueous surfactant solution as a non-aggregated form in the surface micellar layer. Two different modes of PS/Tween 80 binding characterized by their own stability constants and interaction stoichiometry are observed. Microbiological experiments clearly demonstrate that the increased permeability of the outer bacterial membrane caused by the application of the intramicellar form of the photosensitizer or addition of some potentiation agents leads to pronounced light phototoxicity of the pigment against antibiotic-resistant nosocomial strains of Gram-negative bacterial pathogens.

Effect of Surfactants on Reverse Osmosis Membrane Performance

The aim of this study was to evaluate the performance of a reverse osmosis (RO) membrane in surfactant removal using various surfactant model aqueous solutions. The separation tests were performed with laboratory scale units in a dead-end configuration. Cellulose Acetate (CA) and Polyamide (PA) RO membranes were used with nonionic, anionic, or cationic surfactants at a wide range of concentrations. Membrane performance was evaluated using permeate flux and total organic carbon (TOC) rejection. The effects of surfactant type and concentration on RO membranes were assessed. Permeate flux of the PA membrane depended on the surfactant type and concentration. The separation of cationic surfactant aqueous solutions yielded the lowest permeate flux, followed by nonionic and anionic surfactant aqueous solutions, respectively. Surfactant adsorption on the membrane surface occurred at very low concentration of cationic and nonionic surfactants due to electrostatic and hydrophobic interactions, respectively, which affected permeate flux, and micelles did not affect the permeate flux of PA membrane. However, for CA membrane the permeate flux was not affected by the feed solution. Both membranes exhibited satisfactory TOC rejection (92–99%). This study highlights the importance of assessing interactions between membrane material and surfactant molecules to mitigate membrane fouling and guarantee a better performance of the RO membrane.

Separation and Micro Determination of Zinc(II) and Cadmium(II) in Food Samples Using Cloud Point Extraction method

The cloud point extraction technique has become increasingly popular in recent years for trace metal separation and preconcentration. When heated to a specific temperature, cloud point extraction utilizes the property of nonionic surfactants in aqueous solutions to generate micelles and become turbid (so-called cloud point temperature). For analytical chemists, developing a simple and selective technology for the separation and determination of metals and medicinal drugs is a critical concern. Therefore, a sensitive, accurate, and green cloud point extraction (CPE) procedure was developed for the micro-determination of metal cations like zinc (II) and cadmium (II) in food samples. Triton X–114 and 1-(4-(Phenyldiazenyl) phenyl) azo naphthalene-2-ol (Sudan III) were used as extractants. Sudan III forms an ion-pair association complex with metal ions when the pH is 9. In the presence of 5 ppm zinc (II) or 4 ppm cadmium (II) in an aqueous solution, the maximum extraction efficiency should be achieved. In order to create Cloud Point Temperature (CPT) quantitatively, the extraction applications in this approach required heating at 85°C for 20 minutes. In this work, the impacts of different surfactants, pH, stoichiometry, and various organic reagents on interferences as well as spectrophotometric determination were explored. The linearity ranges of zinc (II) and cadmium (II) were 0.25-700 and 0.25-400 ppm, respectively. The results show low detection limits of 0.035 and 0.042 ppm for zinc (II) and cadmium (II), respectively. Also, the quantification limits for zinc (II) and cadmium (II) are 0.116 and 0.140 ppm, respectively.

Reliable assessment of carbon black nanomaterial of a variety of cell culture media for in vitro toxicity assays by asymmetrical flow field-flow fractionation

Carbon black nanomaterial (CB-NM), as an industrial product with a large number of applications, poses a high risk of exposure, and its impact on health needs to be assessed. The most common testing platform for engineered (E)NMs is in vitro toxicity assessment, which requires prior ENM dispersion, stabilization, and characterization in cell culture media. Here, asymmetric flow field-flow fractionation (AF4) coupled to UV–Vis and dynamic light scattering (DLS) detectors in series was used for the study of CB dispersions in cell culture media, optimizing instrumental variables and working conditions. It was possible to disperse CB in a non-ionic surfactant aqueous solution due to the steric effect provided by surfactant molecules attached on the CB surface which prevented agglomeration. The protection provided by the surfactant or by culture media alone was insufficient to ensure good dispersion stability needed for carrying out in vitro toxicity studies. On the other hand, cell culture media in combination with the surfactant improved dispersion stability considerably, enabling the generation of shorter particles and a more favourable zeta potential magnitude, leading to greater stability due to electrostatic repulsion. It was demonstrated that the presence of amino acids in the culture media improved the monodisperse nature and stability of the CB dispersions, and resulted in a turn towards more negative zeta potential values when the pH was above the amino acid isoelectric point (IEP). Culture media used in real cell culture scenarios were also tested, and in vitro toxicity assays were developed optimizing the compatible amount of surfactant.Graphical abstract

Precipitation and recovery of lysozyme denatured by urea and guanidine hydrochloride using anionic surfactant and acetone

The surfactant precipitation and recovery method (SPR method) consist of a precipitation step, that is precipitation of protein-surfactant complex by the addition of aqueous surfactant solution to aqueous protein solution, and a recovery step, that is dissolution of precipitate in polar organic solvent and protein recovery by addition of trace amount of aqueous salt solution. When the denaturant was not included, the precipitation ratio of lysozyme increased as the AOT/lysozyme molar ratio increased, and after reaching 100%, the precipitation ratio decreased due to the redissolution of the precipitation. It was shown that lysozyme denatured by urea and GuHCl can be recovered by the SPR method. Lysozyme denatured with urea had a precipitation ratio and recovery ratio of almost 100% up to a urea concentration of 4 kmol/m3 at an AOT/lysozyme molar ratio of 28.6. As the urea concentration increased, the precipitation ratio and the recovery ratio decreased. Lysozyme denatured with GuHCl had a precipitation ratio and recovery ratio of about 75% at an AOT/lysozyme molar ratio of 71.5 and a GuHCl concentration of 0.6 kmol/m3. The specific activity and the secondary conformation of the recovered lysozyme were confirmed to be almost the same as those of the native lysozyme by measuring the enzyme activity and CD spectrum. It was shown that lysozyme denatured with urea and GuHCl can be recovered by the SPR method as lysozyme has native properties.

Contact-free measurement of surface tension on single droplet using machine learning and acoustic levitation

HypothesisAcoustic levitation provides the possibility to deform levitated droplets in a controllable, and quantifiable manner, thus offering a means to measure the surface tension of a liquid droplet based on its deviation from sphericity. However, for new generation of multi-source and highly stable acoustic levitators, no model relates the acoustic pressure field to the deformation and surface tension. Utilizing a machine learning algorithm is expected to identify correlations between the experimental data without any set preconditions. ExperimentsA series of aqueous surfactant solutions with a large range of surface tensions were prepared, and evaporated under levitation, while the acoustic pressure was varied. A dataset of over 50,000 images was used for the training and evaluation of the machine learning algorithm. Prior to that, the machine learning approach was validated on in silico data that also included artificial noise. FindingsWe achieved high accuracy in predicting the surface tension of single standing droplets (±0.88 mN/m), and we surpassed certain physical conditions related to the size, and shape of the suspended samples that simpler theoretical models are subject to.

Effect of anions and cations on the self-assembly of ionic liquid surfactants in aqueous solution

Ionic liquid surfactants have shown increasing promise for substituting the traditional amphiphiles due to their flexible tunability and superior physicochemical properties. However, the effect of cationic structure and anion type on the surface properties of ionic liquid surfactants remains unclear. Herein, four ionic liquid surfactants [C12mim][BF4], [PyC12][Br], [C12mim][Br] and [PyC12][BF4] with the same alkyl side chain length were designed and synthesized. Their surface properties, such as micelle-free energy (ΔGmθ), surface tension reduction efficiency (ПCMC), and adsorption efficiency (pC20), and the influence of the type and structure of the anion and cation on their micellar physicochemical properties in aqueous solution were discussed according to the data. The proposed approach demonstrates that the critical micelle concentration (CMC) is determined by combining electrostatic and hydrophobic effects. When the anion is BF4−, the ionic liquid has a lower CMC, and BF4− has a superior hydrophobic effect, which allows the ionic liquid to form micelles more easily. In addition, the ionic liquid of tetrafluoroborate has higher interfacial activity (larger pC20) at the same temperature and its aqueous solution has lower surface tension, making it a more desirable surfactant. All four types of ionic liquids have negative values of ΔGmθ, implying that micelle formation is a spontaneous process. The surface activity of imidazolium- and pyridinium-based ionic liquids was slightly different from the critical micelle concentration under the same anion and carbon chain length. Imidazole and pyridine have highly similar hydrophobic and electrostatic effects, and the cation may not be the most critical factor affecting the surface properties.

ГИДРОФОБНЫЕ АРОМАТИЧЕСКИЕ ТИО(ДИТИО)СОЕДИНЕНИЯ В КАЧЕСТВЕ ХРОМОГЕННЫХ АНАЛИТИЧЕСКИХ РЕАГЕНТОВ ДЛЯ ФОТОМЕТРИЧЕСКОГО ОПРЕДЕЛЕНИЯ ТИОЛОВ ПО МЕРКАПТО-ГРУППЕ. III. АНАЛИТИЧЕСКИЕ РЕАГЕНТЫ В ВОДНО-МИЦЕЛЛЯРНЫХ РАСТВОРАХ КАТИОННЫХ ПОВЕРХНОСТНО-АКТИВНЫХ ВЕЩЕСТВ

It was discovered for the first time the ability of a number of hydrophobic aromatic azothio (dithio) compounds, chromogenic analytical reagents to the mercapto group in dipolar aprotic solvents (SH- reagents), to react in aqueous solutions of cationic surfactants with sulfhydryl compounds (SH- compounds) by the type of "thiol-thiol" substitution with manifestation of significant analytical effects (AE). Photometry of hydrophobic thiols is possible by preliminary extraction of the latter with a solution of the SH- reagent from a solution in an acyclic ultimate hydrocarbon. The "thiol-thiol" substitution products may be extracted from aqueous solutions of cationic surfactants with chloroform followed by photometry of AE in an organic medium; reducing the volume of the organic phase compared to the aqueous phase results in higher sensitivity of the assay. Appropriate analytical methods can be used to control hydrogen sulfide and thiols in natural and industrial wastewater, in hydrocarbon gases, and in biological fluids.

Mechanochemical Synthesis of Hydrophilic Sulfur Nanoparticles in Aqueous Surfactant Solutions and Their Antibacterial Activity and Acute Toxicity in Mice

Mechanochemical Synthesis of Hydrophilic Sulfur Nanoparticles in Aqueous Surfactant Solutions and Their Antibacterial Activity and Acute Toxicity in Mice

Influence of a CO2-switchable additive on the surface and foaming properties of a cationic non-switchable surfactant.

Switchable materials in general and CO2-switchable materials in particular are of great interest in environmental research. The replacement of common non-switchable materials (solutions, solvents, surfactants, etc.) with their switchable counterparts has a great potential to make processes more environmentally friendly by enhancing reusability and circularity and thus reducing energy costs and material consumption. Inspired by this, the present work deals with the surface and foaming properties of aqueous solutions of a non-switchable surfactant in presence of a CO2-switchable additive. A 1 : 1 and a 1 : 5 (molar ratios) mixture of the non-switchable surfactant C14TAB (tetradecyltrimethylammonium bromide) and the CO2-switchable additive TMBDA (N,N,N,N-tetramethyl-1,4-butanediamine) were investigated. It was found that surface properties, foamability, and foam stability can be changed by switching the additive with CO2 as a trigger. This observation can be explained by the fact that TMBDA is surface active in its unprotonated, i.e. neutral form, which disturbs the tight packing of the surfactant molecules on the surface. As a consequence, foams generated with surfactant solutions containing the neutral TMBDA are less stable than their TMBDA-free counterparts. On the other hand, the switched diprotonated additive is a 2 : 1 electrolyte with hardly any surface activity and thus does not affect surface and foam properties.

Oscillations in Dynamic Surface Tension of Cationic-nonionic Binary Surfactant Aqueous Solutions.

In this work, the adsorption dynamics of mixed aqueous solutions of tetraethyleneglycol monoocthyl ether (C8E4) - dodecyltrimethylammonium bromide (DTAB) were studied using sessile bubble surface tensiometry. When C8E4 was added to the DTAB solution, the dynamic surface tension exhibited a unique oscillation decay pattern. In contrast, the addition of DTAB to the C8E4 solution resulted in a simple monotonic decay of the surface tension. The same trend was observed for mixtures of tetradecyltrimethylammonium bromide (TTAB) and DTAB. The occurrence of two distinguishable dynamic surface tension behaviors showed reasonable similarity with the theory of the adsorption kinetics of polymer solutions, where the surface tension oscillation was caused by the delayed desorption of polymers due to the conformational change at the solution surface. We compared the dynamic surface tension of binary surfactant systems and the polymer solution theory, and discussed the origin of surface tension oscillations based on the difference in the surface activity of the surfactants.

Wetting effect of branched anionic Gemini surfactant aqueous solution on PMMA surface.

In this paper, the adsorption behaviour and wetting modification ability of the sodium salts of bis-octadecenoyl succinate (GeminiC3, GeminiC6) and monomers on polymethyl methacrylate (PMMA) surfaces were investigated. The difference in spacer length led to slightly different behaviour of surfactant molecules in solution. The large molecular structure and short flexible spacer of GeminiC3 led to a complex self-aggregation behaviour in solution, forming micelles at low concentrations, leading to a rapid decrease in surface tension and subsequent transition to monolayer or multilayer vesicles. In GeminiC6, the longer flexible spacer groups act as spatial structure modifiers that hinder the formation of vesicles. The adsorption behaviour of the gas-liquid interface was analysed in three stages for the peculiar inflection points where surface tension appears. Combining contact angle measurements, adhesion tension and interfacial tension data showed that GeminiC3 and C6 formed a saturated monolayer on the adsorbed PMMA surface at low concentrations and a bilayer structure at high concentrations. Due to the low resistance of molecular space sites, the monomers adsorbed heavily on the PMMA surface, forming semi-colloidal aggregates with the lowest contact angle of monomeric surfactant solutions reaching 38° on the PMMA surface. Also, the monomer and GeminiC3 and C6 surfactants in this paper have a very high hydrophilic modification ability on the PMMA surface compared to other literature.

Effect of 1,2-propanediol on the Critical Micelle Concentration of Decyltrimethylammonium Bromide at Temperatures from 293.15 K to 308.15 K.

It is well known that polar organic compounds, such as alcohols and polyols, exert an appreciable influence on water structure and thus have important effects on surfactant micellization. These substances are often used to modify the properties of surfactants in aqueous solutions, increasing the practical applications they have in diverse industries. In this work, the critical micelle concentration (CMC) of decyltrimethylammonium bromide (C10TAB) in water and in 1,2-propanediol aqueous solutions was determined from both sound velocity and surface tension measurements as a function of surfactant concentration in the temperature range of (293.15 to 308.15) K. The critical micelle concentration of the surfactant increases as the concentration of 1,2-propanediol becomes higher, while the effect on temperature does not show important changes within the range considered. At the selected temperatures, the standard thermodynamic parameters of micellization suggests that the addition of 1,2-propanediol makes the micellization process less favorable. Thermodynamic analysis suggests that the micelle formation of C10TAB is an entropy-driven process at the temperatures considered in this study.

Structural Transitions of Anionic, Cationic, and Nonionic Surfactant Solutions Confined between Amorphous SiO2 Slabs: Molecular Dynamics Simulations

Adsorption of surfactants of a different nature on solid surfaces has found remarkable enthusiasm in many industrial processes such as enhanced oil recovery, detergency, solubilization, and flocculation/dispersion. Surfactants can interact with solid slabs and alter their surface charge and hydrophobicity, which are essential in interfacial phenomena. Interestingly, the surface charges of amorphous materials are thoroughly different from crystalline materials due to the disordered distribution of surface atoms. Therefore, we performed molecular dynamics simulations to examine the interactions of surfactant solutions with SiO2 surface in detail. To this aim, aqueous solutions of various surfactants were confined between two amorphous SiO2 walls, which were 10 nm apart. The results indicate that the structure of the amorphous solid surfaces is changed substantially due to their interactions with surfactant solutions. The simulation results indicate the presence of the nonionic surfactant aggregates in the bulk solvent, while ionic surfactants without branching, such as SDS, form aggregates that adsorb on the SiO2 surface. The interactions of the confined surfactants with glassy SiO2 slabs change the structure of the surface layer and consequently alter the surface charge density during the simulation, which leads to the separation of cationic and anionic parts of the confined surfactants in the vicinity of amorphous SiO2 slabs.

Rheological study of nanoparticle-based cationic surfactant solutions

Worm-like micelles are of special interest among the many forms of surfactant aggregates because of their usefulness in research and technology. Micelles are elongated, flexible aggregates formed by amphiphilic molecules spontaneously self-organizing in liquids. The nature of the surfactant determines its unique shape, which may be altered by mixing it with other substances or changing physicochemical variables like as temperature, pH, or salinity. The rheology of viscoelastic fluid systems is currently being modified using nanoparticles. This method, which was just introduced about 10 years ago, has shown to be highly promising, producing significant improvements in rheological properties, particularly at reservoir temperatures. The goal of this research is to investigate and assess the rheology of an aqueous cationic surfactant solution based on graphene oxide nanoparticles. The thermodynamics, structure, and rheology of nanoparticle-based cationic surfactant solutions were investigated experimentally. According to structural and thermodynamic investigations in surfactant-nanoparticle mixtures, micelle-nanoparticle interactions arise as physical crosslinks between micelles. The existence of these interactions is shown to generate considerable viscosity and viscoelasticity in wormlike micelles, even when the fluid is Newtonian in the absence of nanoparticles. The viscosity, shear modulus, and relaxation time all increase as particle concentration increases. Adding nanoparticles generates a network of micellar entanglements as a result of that. Our results demonstrate that adding nanoparticles to surfactant solutions provides for a one-of-a-kind method of altering fluid rheology under a range of circumstances.