Soluble Surfactant Research Articles

INFLUENCE OF THE PHASE TRANSFER CATALYST ON THE ACCUMULATION AND DECOMPOSITION OF ETHYLBENZENEHYDROPEROXIDE

The regularities of ethylbenzene oxidation and hydroperoxide decomposition in microheterogeneous systems formed by adding sodium dodecyl sulphate to hydrocarbon media have been studied. A pronounced influence of surfactant nature on the transformation mechanism has been revealed. Anionic micellar surfactants including a linear hydrocarbon fragment catalytically accelerate ROOH decomposition, whereas hydrocarbon soluble non-ionic surfactants and solid oxides practically do not influence the reaction rate. Detailed study of the degradation kinetics in the presence of anionic alkyl sulphates has shown that the accelerating effect of surfactants is connected with their colloidal properties, namely, with the formation of joint aggregates of inverse micelles type, which facilitate the destruction of the peroxide bond. For the first time, a synergistic inhibitory effect of sodium alkyl sulphate mixtures with phenolic antioxidants in the oxidation of various hydrocarbons has been found. During the oxidation of ethylbenzene with minor additives (<1%) of sodium dodecyl sulphate (DDS) a unique case of effective self-inhibition has been determined, the mechanism of which includes two steps. Hydroperoxide, the main source of free radicals, decomposes heterolytically in joint microaggregates with DDS. The decomposition occurs selectively with the formation of acetaldehyde and phenol. Phenol being an acceptor of free radicals inhibits the oxidation of ethyl benzene. The main oxidation product of RH in this system is phenol and acetaldehyde. It should be noted that phenols formation at decomposition of alkylaromatic ROOH is usually connected with strong acids. In the case of DDS decomposition of ROOH seems to be driven by the successful orientation of ROOH molecules in the microaggregates formed by anionic surfactants. But a number of experimental factors, namely the influence of the carbon chain length in sodium alkyl sulphates on the dodecane oxidation rate and inertness of the Na2SO4 dispersion in the hydroperoxide decomposition reactions, make it possible to suggest the catalytic reaction of ROOH. Suggest that the catalytic effect of DDS on hydroperoxide decomposition is connected with its colloidal properties and decomposition occurs in common microaggregates formed by DDS and ROOH. The effective activation energy of ROOH decomposition at concentration of 10 mm is Eef = 66.3 kJ/mol. The oxidation of ethyl benzene is completely inhibited at low additions of DDS (1 mM), and the decomposition rate in an atmosphere of N2 significantly increases. DDS increases the effective decomposition constant of ROOH. This surfactant can be considered as an effective catalyst of ROOH decomposition. For citation: Kashkay A.M. Influence of the phase transfer catalyst on the accumulation and decomposition of ethylbenzenehydroperoxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 100-106. DOI: 10.6060/ivkkt.20236602.6684.

Interplay of bulk soluble surfactants and interfacial kinetics governs the stability of two-layer channel flows.

The linear stability of two-layer channel flows in the presence of bulk-soluble surfactants is investigated here, taking into account the rheological properties of the interface. The interfacial stresses are quantified using the Boussinesq-Scriven model, while the surfactant kinetics is assumed to follow the Frumkin isotherm, which accounts for their non-ideal behavior. Our results show that in general, the bulk solubility of surfactants has a stabilizing effect on the interface, both with and without the presence of inertia. On the other hand, the interfacial viscosities play a more complex role, depending on the viscosity ratios of the two fluids, the thickness of the fluid layers, the strength of the surface tension gradients, and the extent of inertia. We show that depending on the strength of inertia and the variability in the surface tension, the interfacial rheology may either stabilize or destabilize the base flow. However, for sufficiently small Reynolds numbers, the surface viscosity always has a stabilizing influence. Our results may be used to better design stable co-flow systems with applications in various processes such as surface coating, preparation of fluid lenses, as well as in a host of multi-purpose microfluidic devices.

Alkylether derivatives of choline as cationic surfactants for the design of soluble catanionic systems at ambient conditions

Mixtures of cationic and anionic surfactants are promising systems with great potential for various purposes in surface and interfacial science. However, so far their applicability has been severely limited by poor solubility at and around equimolar ratios, where too strong interactions typically cause precipitation. In the present study, we hypothesized that the insertion of ethylene oxide units between hydrophobic alkyl chains and a positively charged choline headgroup should give cationic surfactants with high intrinsic flexibility, hindering phase separation and thus allowing soluble catanionic mixtures to be formed at room temperature with conventional sulfate-based anionic surfactants. To that end, different alkylether derivatives of choline were synthesized and combined with alkyl or alkylether sulfates at varying ratios in water. The resulting mixtures of cationic and anionic surfactants were characterized in detail with respect to solubility, static and dynamic activity at surfaces and liquid/oil interfaces, adsorption on solid substrates, and cytotoxicity. In further application-oriented tests, the potential of the developed catanionic surfactant systems for wetting of hydrophobic surfaces, stabilization of liquid foams, and stain removal in lab-scale washing experiments was assessed. Our results demonstrate that the synthesized cationic surfactants can be combined with conventional anionic surfactants to give water-soluble systems across the entire range of mixing ratios, including equimolarity. This remarkable enhancement of solubility is found to be accompanied by pronounced synergistic effects in terms of interfacial activity, evidenced among others by low surface tensions, strong adsorption on solid interfaces as well as fast and complete spreading on hydrophobic substrates. These promising, and readily tunable, physicochemical properties are also reflected in improved foaming and cleaning performance, highlighting the potential of soluble catanionic surfactant formulations for a broad range of industrially relevant applications.

Effect of a soluble surfactant on the linear stability of two-phase flows in a finite-length channel

We study numerically the effect of a soluble surfactant on the stability of two-phase flow in a finite-length microchannel. The two streams drag the surfactant molecules toward the downstream end of the interface against the action of the Marangoni stress. The sharp reduction of the interfacial tension at that end enhances the interface deformation and considerably destabilizes the system, translating into a sharp reduction of the critical capillary number even for very small surfactant volume concentrations.

Direct Resolution of the Interactions of a Hydrocarbon Gas with Adsorbed Surfactant Monolayers at the Water/Air Interface Using Neutron Reflectometry

We have directly resolved in the present work the interfacial composition during and after the interactions of a saturated atmosphere of oil vapor with soluble surfactant solutions at a planar water/air interface for the first time. Experiments were conducted on interactions of hexane vapor with solutions of alkyltrimethylammonium bromides and sodium dodecyl sulfate to observe the balance between cooperativity and competition of the components at the interface. In all cases, hexane adsorption was strongly enhanced by the presence of the surfactant, even at bulk surfactant concentrations four orders of magnitude below the critical micelle concentration. Cooperativity of the surfactant adsorption was observed only for sodium dodecyl sulfate at intermediate bulk concentrations, yet for all four systems, competition set in at higher concentrations, as hexane adsorption reduced the surfactant surface excess. The data fully supported the complete removal of hexane from the interface following venting of the system to remove the saturated atmosphere of oil vapor. These results help to identify future experiments that would elaborate and could explain the cooperativity of surfactant adsorption, such as on cationic surfactants with short alkyl chains and a broader series of anionic surfactants. This work holds relevance for oil recovery applications with foam, where there is a gas phase saturated with oil vapor.

Transport of soluble surfactant on and within a foam film in the context of a foam fractionation process

This study models soluble surfactant transport on and within a foam film during a foam fractionation process. Marangoni flow drives surfactant onto the film, and also surfactant concentration is assumed to be uniform across the thin foam film. Adsorption isotherms are used to couple mass transfer equations, so as to determine the evolution of the total amount of surfactant (surface plus bulk) at any film location. Surfactant transport is considered both in the absence and presence of film drainage. It is observed that having soluble surfactant slows down evolution of Marangoni-driven flow compared to cases assuming insoluble surfactant. This is because in soluble surfactant cases, surfactants diffuse to the bulk even whilst being transferred by Marangoni flow onto the film surface. Furthermore, it is observed that a quasisteady state typically occurs after a long time, such that Marangoni flow and film drainage flow become comparable.

Influence of a soluble surfactant on the transition to tip streaming

We analyze experimentally the influence of a soluble surfactant on the onset of the tip streaming produced by hydrodynamic focusing. For this purpose, we consider the viscous entrainment mode of the selective withdrawal configuration for very different outer liquid viscosities. The minimum capillary number above which viscous entrainment can be produced is determined as a function of the surfactant concentration. We analyze the influence of the surfactant monolayer on the shape and velocity of the emitted liquid jet. The results show the importance of the monolayer dynamics for sufficiently small values of the outer liquid viscosity.

Droplet microfluidics for studying surfactant-rich interfaces found in aerosols, emulsions and foams

<h2>Abstract</h2> The presence of droplets suspended in a liquid or gas is known to play an essential role in fields ranging from materials to atmospheric science. Often, the dispersed phase is stabilized by surface active compounds and surfactants, resulting in complex chemical composition and material properties at the fluid-fluid interface. In this talk, recent advancements in use of microscale flow fields will be highlighted for measuring properties of aqueous multiphase, interface-rich systems. Systems studied will include atmospheric aerosol droplets and liquid-liquid emulsions. Microfluidic contractions, traps, and wells are used to measure surface-bulk partitioning and temperature-dependent liquid-liquid phase separation of aqueous droplets, towards better understanding of suspensions of aerosol droplets in our atmosphere. Advanced measurements of droplet shape deformations and coalescence will also be presented for both water-in-fuel and oil-in-water emulsions, for improved treatment and separation of emulsions. Dynamic interfacial tensions measurements were performed using a microfluidic tensiometer, demonstrating a dependence on if the surfactant approaches the interface from inside (dispersed) versus outside (continuous), implying phase dependent surfactant transport to curved interfaces at the microscale. Droplet coalescence and film drainage experiments are also performed in a microfluidic Stokes trap across a range of viscosity ratios and surfactant concentrations. Results are used to explore the influence of interfacial mobility and Marangoni stresses on film stability with soluble surfactants.

Analysis of influence of surfactant on the properties of diluted asphalt mixtures

In order to reduce the dosage of diluent in diluted asphalt mixture, this paper introduces a surfactant to improve the performance of asphalt mixture, the oil-soluble surfactant was added to the diluted asphalt mixture, and the effect of oil-soluble surfactant on the performance of diluted asphalt mixture during construction was investigated by mixing adhesion test, penetration test, cohesive test and rotary compaction test. At the same time, combined with rutting test, low temperature bending test and Marshall test, the effect of oil soluble surfactant on the performance of diluted asphalt mixture in service period was analyzed.The test results show that 1% oil-soluble surfactant can reduce diesel diluent at least 4%, and the addition of surfactant can significantly improve the construction performance of diluted asphalt mixture. At the same diluent dosage, the strength of asphalt mixture diluted by surfactant increases significantly, the low temperature performance and water stability are improved, and the high temperature performance is slightly insufficient and slightly reduced. The other road performance can meet the standard of hot mix.

Surfactant-Mediated Solubilization of Myelin Figures: A Multistep Morphological Cascade.

Lamellar mesophases of insoluble lipids are readily solubilized by the micellar mesophases of soluble surfactants. This simple process underscores a broad array of biochemical methodologies, including purification, reconstitution, and crystallization of membrane proteins, as well as the isolation of detergent-resistant membrane fractions. Although much is now known about the thermodynamic driving forces of membrane solubilization, the kinetic pathways by which the surfactant alters vesicular mesophases are only beginning to be appreciated. Little is known about how these interactions affect the solubilization of more complex, multilamellar mesophases. Here, we investigate how a common zwitterionic detergent affects the solubilization of a smectic, multilamellar, cylindrical mesophase of lipids, called the myelin figure. Our results reveal that myelin solubilization occurs in a multistep manner, producing a well-defined sequence of morphologically distinct intermediates en route to complete solubilization. The kinetic processes producing these intermediates include (1) coiling, which encompasses the formation, propagation, and tightening of extended helices; (2) thinning, which reflects the unbinding of lamellae in the smectic stacks; and (3) detachment or retraction, which either dissociates the myelinic protrusion from the source lipid mass or returns the myelinic protrusion to the source lipid mass─all in transit toward complete solubilization. These occasionally overlapping steps are most pronounced in single-lipid component myelins, while compositionally graded multicomponent myelins inhibit the coiling step and detach more frequently. Taken together, the appearance of these intermediates during the solubilization of myelins suggests a complex free-energy landscape characterizing myelin solubilization populated by metastable, morphological intermediates correlated with locally minimized changes in energy dependent upon the mesophase's composition. This then predicts the accessibility of structurally distinct, kinetic intermediates─such as loose and tight coiled helices, peeled myelins, retracted tubes, and detached protrusions─before reaching the stable ground state corresponding to a dissolved suspension of mixed surfactant-lipid micelles.

Competition between thermal and surfactant-induced Marangoni flow in evaporating sessile droplets

HypothesisThermal Marangoni flow in evaporating sessile water droplets is much weaker in experiments than predicted theoretically. Often this is attributed to surfactant contamination, but there have not been any in-depth analyses that consider the full fluid and surfactant dynamics. It is expected that more insight into this problem can be gained by using numerical models to analyze the interplay between thermal Marangoni flow and surfactant dynamics in terms of dimensionless parameters. SimulationsTwo numerical models are implemented: one dynamic model based on lubrication theory and one quasi-stationary model, that allows for arbitrary contact angles. FindingsIt is found that insoluble surfactants can suppress the thermal Marangoni flow if their concentration is sufficiently large and evaporation and diffusion are sufficiently slow. Soluble surfactants, however, either reduce or increase the interfacial velocity, depending on their sorption kinetics. Furthermore, insoluble surfactant concentrations that cause an order 0.1% surface tension reduction are sufficient to reduce the spatially averaged tangential flow velocity at the interface by a factor 100. For larger contact angles and smaller droplets this required concentration is larger (typically <1% surface tension reduction). The numerical models are mutually validated by comparing their results in cases where both are valid.

Synthesis and characterisation of carboxy amide-bonded pyridinium Gemini surfactants: influence of the nature of the spacer group and counterions on the aggregation behaviour

Abstract A series of novel dimeric pyridinium surfactants has been synthesised and the effects of a semi-flexible p-xylyl spacer and flexible, polyethylene glycol spacers have been studied. The nature of the spacer determines solubility and aggregation behaviour in two- and three-dimensional systems. Some of these insoluble compounds form two-dimensional, rigid-condensed structures at the air–water interface, while others form liquid-analogue monolayers. Whereas the latter compounds become soluble after exchange of the counterions, the former remain insoluble. The aggregation behaviour of Langmuir layers was, inter alia, investigated by Brewster angle microscopy. The micellisation behaviour of diluted aqueous solutions of soluble surfactants was primarily investigated by conductometric measurements and thermodynamic parameters of aggregation have been deduced with respect to the spacer length.

Promising solar photodegradation of RY 86 by hydrophilic F127 (pluronic) aided nano cobalt ferrite and its biomedical applications

To our surprise, we effectively excelled in developing the hydrophilic, non-ionic and water soluble triblock copolymer surfactant F127 (pluronic) aided spinel cobalt ferrite (CFO) nanoparticles. The crystalline nature and surface morphology of F127 aided CFO nanoparticles have been confirmed laboriously by XRD, HR-TEM, DLS, FT-RAMAN, FT-IR, UV-DRS, and SEM-EDX. SEM confirms undeclared rod-like structure and HR-TEM supports a shape similar to quasi-spherical morphology. The band gap investigation report that the Eg value of F127 aided CFO is around 1.24 eV. We found the fact that, in the UV/solar light degradation of hazardous Reactive Yellow 86 (RY 86), the photocatalytic activity of F127 aided CFO nanoparticles was accelerated by the presence of H2O2. F127 is a surfactant that played a key role in the enhanced activity of F127 aided CFO nanoparticles. By using an external magnetic field, the catalyst can be recovered from the fluid medium and thereby reused. The feasible mechanism for active liquid phase photodegradation of RY 86 has also been developed. Therefore, we assure that the novel spinel F127 aided CFO nanoparticles will shed more light for the wastewater treatment system because of its effective photocatalytic and reusable behavior. In conjunction, the antibacterial function and cytotoxicity are also performed.

Influence of a Soluble Surfactant on the Transition to Tip Streaming

Influence of a Soluble Surfactant on the Transition to Tip Streaming

Oil soluble surfactants as efficient foam stabilizers

The surface and foam properties of two oil-soluble surfactants, Span 60 and Brij 72, and two water-soluble surfactants, Tween 60 and Brij S20, are compared. Aqueous surfactant solutions containing sugar at high concentration (63 wt%) are also studied in the context of sweet food-related foams. The experimental results show that foams with very small bubbles of ca. 5 µm are formed and remain stable for more than 10 days at room temperature when oil-soluble surfactants are dispersed in the sugar-rich solutions. The excellent stability of these foams is related to (1) The multilamellar vesicles present in the respective surfactant dispersions which increase the viscosity and decrease the rate of water drainage from the foam; (2) The very slow exchange of surfactant molecules between the interface and the adjacent aqueous solution that leads to very significant difference in the surface tension of shrinking and expanding bubbles, which in turn decreases the rate of bubble Ostwald ripening. The foams formed from Span 60 are more stable as compared to the foams formed from Brij 72, due to the higher viscosity and the slower interface-solution exchange. The foams formed from Brij S20 solutions are least stable - they are completely destroyed after 1 day at room temperature, even in the presence of sugar. The main conclusion of this study is that oil soluble surfactants can form condense adsorption layers on the bubble surfaces after adsorption from aqueous solutions with and without sugar in it. The formed layers, which present a better molecular packing, reduce the gas permeability and decelerate the Ostwald ripening disproportionation of the foam This is obtained by a relatively low interfacial tension imparted by continuous shrinkage and expansion of bubbles during foam generation, ultimately ensuring long-term stabilization of formed foams.

Pore-Scale Modeling of Two-Phase Flows with Soluble Surfactants in Porous Media

Pore-Scale Modeling of Two-Phase Flows with Soluble Surfactants in Porous Media

The cause of accelerated desorption of sparingly soluble dodecanol monolayers: Convection or leakage?

The dissolution of sparingly soluble surfactants from spread monolayers is a complex multi-staged process. The desorption of dodecanol from the surface of water follows mixed barrier/diffusion kinetics only in the first stages of the dissolution. Significant acceleration of the desorption has been observed experimentally after this initial period, which has been hypothesized to be due to onset of convective diffusion; the source of convection, however, has never been identified. The goal of this work is to investigate the question through desorption experiments under controlled convection and respective modeling of the process under mixed barrier/convective diffusion control. Several hypotheses for the cause of the accelerated desorption have been tested. The analysis has shown that natural convection, Marangoni convection, convection due to the motion of the mechanical barrier of the Langmuir trough, and artificial convection caused by an electromagnetic stirrer cannot produce desorption rates of the observed magnitude. These findings convincingly prove for the first time that the convective diffusion has less of a role in the transport process than previously thought. The most likely reason for the acceleration is identified as leakage through the movable barrier. The rate of this leakage is estimated form the experimental data. Implications for the use of adsorption isobars to study desorption kinetics are discussed.

Infrared thermography applied to the surface pressure measurements in insoluble surfactant monolayers

ABSTRACT New experimental technique, based on IR thermography, is proposed to measure the surface pressure for dilute monomolecular films of surfactants on a liquid surface. The surfactant molecules are distributed unevenly along the surface, which leads to the formation of surface regions of two kinds. Part of the surface is covered with surfactant film, which suppresses the surface renewal and inhibits the heat transfer between the surface and the bulk liquid. Thus, these regions possess lower temperature compared to the rest of the surface, free of surfactant and exhibiting both buoyant and thermocapillary convection. High sensitivity of the modern IR cameras allows the measurement of the temperature difference between the surface regions, from which the surface pressure can be derived. Experiments with myristic acid are performed for different values of the surface temperature and mean concentration of the surfactant. The results demonstrate that it is possible to measure the surface pressure for liquid-expanded films with area per molecule up to . The derived parameters of 2D van der Waals gas are in agreement with published data . The proposed technique can also be used to compare the contamination level in dilute films of insoluble and soluble surfactants.

Polymer drag reduction in surfactant-contaminated turbulent bubbly channel flows

Polymer additives are commonly utilized to manipulate bubbly flows in various applications. Here, we investigate the effects of clean and contaminated bubbles driven upwards (upflow) in Newtonian and viscoelastic turbulent channel flows. Interface-resolved direct numerical simulations are performed to examine sole and combined effects of soluble surfactant and viscoelasticity using an efficient 3D finite-difference/front-tracking method. The incompressible flow equations are solved fully coupled with the FENE-P viscoelastic model and the equations governing interfacial and bulk surfactant concentrations. The latter coupling is accomplished by a non-linear equation of state that relates the surface tension to the surfactant concentration. For Newtonian turbulent bubbly flows, the effects of Triton X-100 and 1-Pentanol surfactant are examined. It is observed that the sorption kinetics highly affect the dynamics of bubbly flow. A minute amount of Triton X-100 is found to be sufficient to prevent the formation of bubble clusters restoring the single-phase behavior while even two orders of magnitude more 1-Pentanol surfactant is not adequate to prevent the formation of layers. For viscoelastic turbulent flows, it is found that the viscoelasticity promotes formation of the bubble-wall layers and thus the polymer drag reduction is completely lost for the surfactant-free bubbly flows, while the addition of small amount of surfactant (Triton X-100) in this system restores the polymer drag reduction resulting in $25\%$ drag reduction for the $Wi=4$ case.

Hydrodynamics and Interfacial Surfactant Transport in Vascular Gas Embolism

Abstract Vascular gas embolism—bubble entry into the blood circulation - is pervasive in medicine, including over 340,000 cardiac surgery patients in the U.S. annually. The gas–liquid interface interacts directly with constituents in blood, including cells and proteins, and with the endothelial cells lining blood vessels to provoke a variety of undesired biological reactions. Surfactant therapy, a potential preventative approach, is based on fluid dynamics and transport mechanics. Herein we review literature relevant to the understanding the key gas–liquid interface interactions inciting injury at the molecular, organelle, cellular, and tissue levels. These include clot formation, cellular activation, and adhesion events. We review the fluid physics and transport dynamics of surfactant-based interventions to reduce tissue injury from gas embolism. In particular, we focus on experimental research and computational and numerical approaches involving how surface-active chemical-based intervention. This is based on surfactant competition with blood-borne or cell surface-borne macromolecules for surface occupancy of gas–liquid interfaces to alter cellular mechanics, mechanosensing, and signaling coupled to fluid stress exposures occurring in gas embolism. We include a new analytical approach for which an asymptotic solution to the Navier–Stokes equations coupled to the convection-diffusion interaction for a soluble surfactant provides additional insight regarding surfactant transport with a bubble in non-Newtonian fluid.