Dilute Surfactant Solutions Research Articles

A novel approach for structure quantification of fatty acids films on rain water

A complete compositional or structural description of naturally occurring surfactants on rainwater is not currently feasible. A main limitation of previous work has been the lack of means for correlating force-area characteristics with the chemical makeup of the films. Instead of analyzing the chemical composition of rain water film-forming organics, it is postulated here to introduce the novel scaling procedures (2D virial equation of state and 2D polymer film scaling theory) applied to the surface pressure-area ( π− A) isotherms and surface pressure-temperature ( π− T) isochors, and resulting from generalized physical formalisms modified to a multicomponent surfactant film. A set of the introduced structural film state parameters could become sensitive indicators for surface-active source-specific organic matter pathways tracing, where the measurement of surfactant concentration and chemical analyses are avoided. Performed comprehensive film studies on rain, marine and snow-melted water samples exhibited significant and differentiated film structural parameters variability. The developed procedure allows one to recover the film parameters ( π, Γ, A lim, E isoth) present originally at the raindrop surface from the Langmuir trough data supplemented with the simultaneously taken rain event characteristics (rain rate and rain drop diameter distribution). It requires the partitioning effect of the surfactant molecules between the surface and bulk phases to be estimated where the entering quantities are: the partitioning coefficient K p= Γ/ c and a degree of the rain water interfacial system area development A r/ V r evaluated here using the fatty acids concentrations as model input data. The latter parameter depends on the rain rate and the form of the drop size distribution function differing significantly from the Marshall–Palmer one at low I r (<1 mm h −1). The partitioning factor K p related to the physicochemical composition of the film-composing material exhibited a seasonal and source-specific features and varies in a rather narrow range (5.3–13.7 cm) being of secondary importance in comparison to the interface development term. Original rain drop films exhibited low surface pressures (1.9–5.4 mN m −1) characteristic of a quasi-ideal 2D gas behavior found in a diluted surfactant solution (with c≈10 −3a) and are composed of slightly soluble immiscible components of mean molecular masses within 261–270 Da in agreement with chemical analyses. The concept is quantified using the Langmuir trough film and disdrometer data on a set of rainwater events observed at Gdańsk, Poland in May 2002.

Rheological Characteristics and Turbulent Friction Drag and Heat Transfer Reductions of a Very Dilute Cationic Surfactant Solution

Turbulent friction drag and heat transfer reductions and rheological characteristics of a very dilute cationic surfactant solution, cetyltrimethyl ammonium chloride (CTAC)/sodium salicylate (NaSal) aqueous solution, were experimentally investigated at various temperatures. It was found that there existed a critical temperature above which drag and heat transfer reductions disappeared and shear viscosities rapidly dropped to that of water. It was surmised that drag and heat transfer reductions had a certain relationship with rheological characteristics and a rheological characterization of CTAC∕NaSal surfactant solutions was performed to clarify this relationship. The effects of Reynolds number and fluid temperature and concentration on drag and heat transfer reductions were qualitatively explained by analyzing the measured shear viscosity data at different shear rates and solution temperatures and concentrations. The Giesekus model was found to fit the measured shear viscosities reasonably well for different temperatures and concentrations of the surfactant solution and the model parameter values obtained by fitting were correlated with temperature at certain solution concentrations. From the correlation results, the temperature effect on viscoelasticity of surfactant solutions was analyzed to relate the rheological characteristics with drag and heat transfer reduction phenomena.

Lyophilic properties of surfactant-rich phases of polyethoxylated alkylphenols formed at cloud point temperature

The influence of the concentration conditions, solutions acidity, and electrolyte additions on the lyophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 formed at cloud point temperature were studied. The lyophilic properties of surfactant-rich phases were determined by estimating of their effective hydration values and solvation free energy of methylene and carboxyl groups at cloud point extraction of aliphatic monocarboxylic acids. It was shown that the surfactant-rich phases formed from the dilute surfactant solutions have more hydrophobic properties than the phases formed from the high concentrated solutions. The possibility of changing the lyophilic properties of surfactant-rich phases by electrolyte additions was shown: complex formation between electrolyte cation and the polyoxyethylene chain of the surfactant increases the hydrophilic properties of the surfactant-rich phases. Calculations of the solvation free energy of methylene and carboxylic fragments of the aliphatic carboxylic acids at micellar extraction showed the uniqueness of the surfactant-rich phases which are able to energetically advantageously extract both hydrophilic and hydrophobic molecules of substrates.

The Fluid Dynamical Properties of a Dilute Surfactant Solution around a Circular Cylinder

Influence of adding cationic surfactant (Ethoquard O12) with a consentration of 50 ppm on water flow around a cylinder in a range of Reynolds number Res between from 64 to 600 was investigated by using LDV and PIV. At Res =300, the flow with the surfactant formed a stagnant zone, which appeared periodically, in front of the cylinder expanding along the axial direction. The period of the appearance was about 120 [s]. The periodic flow structure was visualized by the measurements of velocity fluctuation. The development of the stagnant zone in front of the cylinder induced the expansion of a low speed flow area near the side of the cylinder.

Basicity of some P1phosphazenes in water and in aqueous surfactant solution

The pKa values in water and in dilute surfactant solution for 15 ring-substituted phenyl P1 pyrrolidino phosphazenes PhN=P(NC4H8)3 and the phenyl P1 dimethylamino phosphazene PhN=P(NMe2)3 previously studied in acetonitrile (AN) and tetrahydrofuran (THF) are reported. The nonionic surfactant Tween 20 was used for the basicity measurements of some compounds to overcome the solubility problems. Measurements with a control group of phosphazenes in both media were used to validate the use of the obtained pKa values as estimates of aqueous values. The pK(a) values of the studied phosphazenes in aqueous medium vary from 6.82 (2,6-dinitro-) to 12.00 (4-dimethylamino-). The basicity span is 5.18 pKa units. The aqueous pKa values of the P1 phosphazenes were correlated with the respective basicity data in AN and THF and from these correlations the pK(a) values in water for the parent compounds HN=P(NC4H8)3 and HN=P(NMe2)3 were estimated as 13.9 and 13.3. Also a comparison of the basicity of phosphazenes and some guanidines, amines and pyridines was made. In water the parent phosphazenes and guanidines are the strongest of all the groups of bases studied. In AN and THF the parent phosphazenes are clearly the strongest bases followed by guanidines, amines and pyridines which are bracketed between the basicities of phenyl phosphazenes. In the gas phase the phosphazenes for which data are available are clearly more basic than the other compounds referred to here. Comparison of the basicity data of P1 phosphazenes and some guanidines confirms earlier conclusions about the partly ylidic character of the N=P double bond.

Current Understanding of Formation Mechanisms in Surfactant‐Templated Materials

AbstractFor Abstract see ChemInform Abstract in Full Text.

ESI-MS quantitation of increased sphingomyelin in Niemann-Pick disease type B HDL

HDLs have been proposed to have antiatherogenic properties because of their role in reverse cholesterol transport as lipid acceptors. To elucidate the phospholipid profile of these particles, we used electrospray ionization mass spectrometry to examine the phosphatidylcholine (PC) and sphingomyelin (SM) composition of HDLs purified from plasma and nascently generated in vitro from fibroblasts. We also quantitatively compared the phospholipids present in these lipoproteins between normal and Niemann-Pick disease type B (NPD-B) subjects characterized by sphingomyelinase (SMase) deficiency. We demonstrated that plasma HDLs from NPD-B were significantly enriched in SM by an average of 28%, particularly the palmitoyl SM (with an increase of 95%), which accounted for approximately 25-44% of total SM molecular species. Similarly, we observed an increase of approximately 63% in total SM levels in nascent HDLs prepared from NPD-B fibroblasts. Although PC levels in nascent HDLs were comparable between control and NPD-B cells, there was a 95% increase in total PC levels similar to that of SM in plasma HDLs extracted from NPD-B subjects. These data provide insight into the structure of HDLs and identify potential new roles for SMase in lipoprotein metabolism.

Electrochemical Deposition of Mesoporous Nickel Hydroxide Films from Dilute Surfactant Solutions

A series of micelle-templated mesoporous nickel hydroxide films were prepared by electrochemical deposition from dilute surfactant solutions by using different types of template and by varying plating solvent composition. Lamellar mesostructured Ni(OH)2 films are obtained with only anionic surfactant sodium dodecyl sulfate (SDS) as the template. In particular, a unique cooperative assembly fashion, that is, the combination between Ni2+ and a complex composed of the primary template SDS and a cosurfactant, such as triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) copolymers and poly(ethylene glycol), was explored, by which two-dimensional hexagonal mesoporous Ni(OH)2 films were electrodeposited. Meanwhile, the deposition medium also plays a crucial role in determining the mesostructure of Ni(OH)2 films. For the composite nickel hydroxide films deposited from aqueous solution or dilute aqueous solution of ethylene glycol (<20 wt %) in the presence of SDS or the SDS-poly(alkylene oxide) polymer complexes, a mixed lamellar phase with d(001) = 37.4 A and d(001) = 28.5 A was obtained. However, single lamellar phase with d(001) = 37.4 A was electrodeposited from concentrated aqueous solutions of ethylene glycol (> or = 20 wt %). Furthermore, such deposition baths have access to hexagonal mesoporous nickel hydroxide films with d(100) = 37.4 A at 70 degrees C with the SDS-poly(alkylene oxide) polymer complexes as the templates. Within the potential window for Ni(OH)2, the morphology and quality of mesostructured films are significantly dependent on the deposition potential, while the mesostructures of the composite films always remain unchanged.

Current Understanding of Formation Mechanisms in Surfactant-Templated Materials

Surfactant-templated materials are created through self-assembly in solutions containing both surfactant micelles and an inorganic species. The resulting materials are composites containing an organized surfactant micelle array encapsulated in the inorganic material. Removal of the surfactants generates nanoscale pores which replicate the highly organized micelle phase, producing high surface area materials with uniform pores that have applications in catalysis, molecular separation, encapsulation for sensors and slow release, and thin films for optoelectronics and photoelectrochemical devices. This review looks at recent work aimed at understanding how these materials self-assemble from dilute surfactant solutions to form intricate nanoscale configurations, which also often show complex and highly ordered structures on longer length scales.

Physicochemical Interactions During Surfactant Flooding of Fractured Carbonate Reservoirs

Summary Recovery from fractured, oil-wet/mixed-wet, carbonate reservoirs by waterflooding is poor. Dilute surfactant methods are being developed to improve oil recovery from fractured carbonates. This paper investigates the interactions of dilute alkaline anionic surfactant solutions with crude oil on carbonate mineral surfaces. Wettability, phase behavior, interfacial tension, and adsorption experiments have been conducted. Anionic surfactants have been identified that can change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant dodecyl trimethyl ammonium bromide (DTAB) with a west Texas crude oil. All the carbonate surfaces (lithographic limestone, marble, dolomite, and calcite) show similar behavior with respect to wettability alteration with an anionic surfactant. Anionic surfactants, which lower the interfacial tension with the crude oil to very low values (&amp;lt;10−2 mN/m), have also been identified. The adsorption of the sulphonate surfactants can be suppressed significantly by the addition of Na2CO3, because the addition of carbonate can change the zeta potential of calcite to a negative value. Greater than 50% OOIP can be recovered from oil-wet carbonate cores by spontaneous imbibition of 0.05 wt% anionic surfactant solutions in the laboratory scale.

Effects of non-isothermal heating on drag reduction in surfactant aqueous solution flow

In this study we investigate the control of flow characteristics and heat transfer of a drag-reducing dilute cationic surfactant solution in a channel, in order to develop a highly efficient heat exchanger. As has been reported by many authors, addition of certain polymers or surfactants reduces heat transfer in drag-reduced water flow. Therefore, other measures must be taken in order to compensate the reduction in heat transfer. Specifically, this study investigates the effects of non-isothermal heating on drag-reduced flow: experiments were conducted in order to study passive control for effecting the drag-reduction state by employing temperature-dependent physical properties and heat transfer augmentation by complex flow. In addition, velocity and temperature profiles were measured under the coexistence of turbulent and drag-reducing flow in order to clarify the effect of drag reduction. It was confirmed that the drag reduction state was changed and diminished due to the temperature rise near the wall, especially the condition in the region of 50< y +<100 greatly influence on drag reduction of pipe flow.

Development characteristics of drag-reducing surfactant solution flow in a duct

Development characteristics of dilute cationic surfactant solution flow have been studied through the measurements of the time characteristics of surfactant solution by birefringence experiments and of the streamwise mean velocity profiles of surfactant solution duct flow by a laser Doppler velocimetry system. For both experiments, the concentration of cationic surfactant (oleylbishydroxymethylethylammonium chloride: Ethoquad O/12) was kept constant at 1000 ppm and the molar ratio of the counter ion of sodium salicylate to the surfactants was at 1.5. From the birefringence experiments, dilute surfactant solution shows very long retardation time corresponding to micellar shear induced structure formation. This causes very slow flow development of surfactant solution in a duct. Even at the end of the test section with the distance of 112 times of hydraulic diameter form the inlet, the flow is not fully developed but still has the developing boundary layer characteristics on the duct wall. From the time characteristics and the boundary layer development, it is concluded that the entry length of 1000 to 2000 times hydraulic diameter is required for fully developed surfactant solution flow.

Electrocatalytic Properties of Thin Mesoporous Platinum Films Synthesized Utilizing Potential‐Controlled Surfactant Assembly.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Effects of Surfactant on Formation of Water Bell

Water bell which resulted from the equilibrium between surface tension and centrifugal acceleration was found by Felix Savart in 1833 for the first time. To investigate the effects of surfactant on water bell formation, we took photographs of the water bells for distilled water and dilute surfactant solutions with high-speed video camera and digital camera. From the analysis of these photos, it was found that the surface shapes at the same injection pressure were almost same in spite of an addition of surfactant and became very stable when the surfactant was added. Then we performed a numerical simulation based on the equilibrium of a liquid sheet. Results showed the closely coincidence with the calculated shapes and the measured ones.

Chemistry of silica at different concentrations of non-ionic surfactant solutions: effect of pH of the synthesis gel on the preparation of mesoporous silicas

Ordered and disordered mesoporous silicas have been synthesized through an assembly of non-ionic decaoxyethylene cetyl ether [C 16(EO) 10] and a tetramethoxysilane silica source by variation of the pH value of the synthesis gel. The structure, texture and morphology of the mesoporous silicas, synthesized with concentrated and diluted surfactant solutions, have been discussed from the perspective of silica’s chemistry upon a variation of pH values of the synthesis gel (micellar solution). With concentrated surfactant solutions (50 wt%), disordered compounds are obtained in a range of pH from 2.0 to 7.0 (micellar solution). As the pH increases, however, the pore size distributions (PSD) become broader and bimodality appears due to the micelle-templated silica (MTS) mesopores and openings arising from silica dissolution–reprecipitation processes. Also, the MTS pores expand due to a change in conformation of the surfactant hydrophilic head upon pH increase. On the other hand, diluted surfactant solutions (10 wt%) lead to ordered materials in a pH range from 2.0 to 7.0 (synthesis gel). The PSD remain very narrow but interparticular porosity appears and the morphologies undergo deep changes from toroids, gyroids and ropes to aggregates of very small particles with increasing pH.

Treatment of severe meconium aspiration syndrome with dilute surfactant lavage.

Despite the development of new adjuvant therapies, meconium aspiration syndrome (MAS) remains a serious respiratory disorder in neonates. Surfactant inactivation by meconium can be overcome by use of exogenous surfactant. This study sought to assess the efficacy and safety of dilute surfactant lavage at 2 different concentrations to treat severe MAS. We retrospectively reviewed the charts of all term infants with a diagnosis of MAS who had an oxygenation index (OI) > 20 during a 2-year period. Tracheobronchial lavage was performed with a dilute surfactant suspension (5 mg/mL or 10 mg/mL) to reach a total dose of 60 to 70 mg/kg of phospholipid, administered in aliquots of 2 mL. The records of 22 patients were reviewed, of whom 12 had undergone lavage. These patients were subdivided into low-concentration (surfactant concentration, 5 mg/mL; n = 6) and high-concentration (surfactant concentration, 10 mg/mL; n = 6) subgroups. There were no significant differences in demographic characteristics between these 2 subgroups. The lavaged infants had a significantly higher arterial partial pressure of oxygen (PaO(2)) 24 hours after lavage than the infants without lavage (178.3 mm Hg vs 80.6 mm Hg, p < 0.05). The incidence of pneumothorax (1/12 vs 7/10, p < 0.05) and requirement for inhaled nitric oxide (5/12 vs 9/10, p < 0.05) were significantly lower in the lavaged group. All infants tolerated the procedure well except for 2 with transient complications. There were no significant differences in duration of lavage, response and complications between subgroups lavaged at low and high surfactant concentration. Early lavage with dilute surfactant solution at a phospholipid concentration of either 5 mg/mL or 10 mg/mL is effective for the treatment of severe MAS. Further large-scale, prospective, randomized, controlled trials are necessary to establish the optimal dose, concentration, surfactant product, and instillation method of this treatment before it can be recommended for routine use.

Electrochemical degradation of surfactants by intermediates of water discharge at carbon-based electrodes

The electrochemical oxidation of anionic (sodium dodecylbenzenesulfonate) and cationic (hexadecyltrimethyl ammonium chloride) aqueous dilute surfactant solutions at a BDD (boron-doped diamond) electrode has been studied by batch electrolysis experiments and potentiodynamic measurements. In the potential region of water decomposition ( E>2.3 V vs. SHE), surfactants could be deactivated and oxidised with total organic carbon (TOC) removals up to 82% by the action of intermediates of water discharge (e.g. hydroxyl radicals). Of the investigated process parameters, the initial electrolyte pH had the highest impact on surfactant oxidation. An initial pH of 10 significantly enhanced the electrochemical oxidation of both surfactants. The process was not diffusion-controlled and instantaneous current efficiencies (ICE) for TOC removal were in all cases low, varying from 5 to 12% on average. The surfactant deactivation and oxidation potential of the BDD electrode was compared with other carbon-based electrodes. Applying an equal electrode surface, the BDD electrode showed much higher surfactant removals compared to plane graphite. Graphite granules and carbon felt suffered from abrasion, leading to additional carbon loading of the surfactant solutions. Based on the current electrolysis configuration, the specific energy requirement with the BDD electrode for the electrochemical oxidation of surfactants was estimated at 10–20 kW h m −3 effective wastewater.

Time-dependent drag reduction and ageing in aqueous solutions of a cationic surfactant

The turbulent pipe flow of a highly dilute aqueous cationic surfactant solution is investigated by means of a pulsed ultrasound Doppler method with special emphasis on the wall boundary layer. The velocity profiles are recorded for several Reynolds numbers at varying ages of the solution. The wall shear stress ve- locities us used for the normalization of the velocity profiles are determined by fitting the measured profiles to the universal linear velocity profile in the viscous sub- layer. The theoretical pressure loss is then calculated from the numerical values of us and compared to the experimental values. Two different scaling methods are discussed for the velocity fluctuations concerning the correlation of the root-mean square values with the effect and the amount of drag reduction. It is shown that outer scaling with the mean velocity is appropriate for the detection of drag reduction in surfactant solutions, rather than inner scaling with the wall shear stress velocity, which is common practice in investigations of 'usual' turbulent flows.

Shear-Thickening in Salt-Free Aqueous Solutions of a Gemini Cationic Surfactant: A Study by Small Angle Light Scattering

The shear-thickening regime of dilute cationic surfactant solutions is studied by means of small-angle light scattering. The 2-dimensional intensity pattern measured in the flow velocity−vorticity plane exhibits an intense streak pattern perpendicular to the flow direction. The main features of this streak pattern are as follows: (i) a periodic modulation of the intensity in the vorticity direction, (ii) fluctuations of the intensity and orientation as a function of scattering volume, (iii) a strong correlation of the average intensity with the apparent shear viscosity, and (iv) an average shape independent of the applied shear rate. The corresponding anisotropic optical contrast profile with a characteristic modulation length about 33 μm in the vorticity direction cannot be interpreted in terms of the alignment of large anisotropic colloidal objects in the flow but, instead, is consistent with the existence of an aligned heterogeneous gellike layer in the gap.

Kinetics of the Shear-Thickening Transition Observed in Dilute Surfactant Solutions and Investigated by Flow Birefringence

We report on the rheo-optical properties of dilute surfactant solutions which exhibit a shear-induced thickening transition. The surfactant investigated is cetyltrimethylammonium tosylate at concentrations around 0.2 wt % in water. By comparing data obtained by rheology and rheo-optics, we first confirm that the thickening transition is associated with the transformation of the initially isotropic micellar liquid into a birefringent and strongly aligned phase. In both experiments, the transition occurs at the same critical shear rate, denoted γ̇c. Using a new treatment for the analysis of the rheo-optical data, we have been able to determine the birefringence Δn and extinction angle χ at steady state, but also as a function of the time and of the spatial coordinate in the 1 mm gap of a Couette-type shearing cell (with a spatial resolution of 15 μm). Starting from a solution in a quiescent state and applying steady shear, we provide an accurate description of the kinetics of formation of the shear-induced and viscous phase. At steady state, we observe strong variations of the flow birefringence Δn as a function of the spatial coordinates within the gap, as well as a failure of the stress-optical law. The extinction angle χ is then close to 0°, independent of the shear rate and of the spatial coordinates. The flow birefringence also exhibits rapid fluctuations around the average profiles, on a length scale comprised between 50 and 100 μm. These fluctuations are interpreted as shear bands of enhanced and reduced birefringence, a result which suggests a strongly inhomogeneous and instable shear flow in the shear-induced phase.