Surfactant Sodium Dodecyl Sulfate Concentration Research Articles

Optimal conditions for enhancing sodium dodecyl sulfate biodegradation by Pseudomonas aeruginosa KGS

The anionic surfactant sodium dodecyl sulfate (SDS) was degraded by novel strain ofPseudomonas aeruginosa KGS under accession No. JQ328193, which was isolated from carwash wastewater. The purpose of this research was to study different optimization conditionsrequired for enhancing the biodegradation of sodium dodecyl sulfate P. aeruginosa KGS.Influence of different Physicochemical factors such as nitrogen and carbon sources, pH,temperature, inoculation percent and different concentrations of SDS on the biodegradation ofSDS were investigated by measuring the degradation rate of SDS using methylene blue activesubstance (MBAS) method. The optimum conditions determined for the this selected bacteriumstrain for degradation of SDS were 1.5mM SDS, inoculation percent 7%, pH 7.5, temperature37°C, ammonium nitrate (nitrogen source) when basal salt medium was supplemented withglucose as a co substrate. This bacterium is able to degrade about 98% of the SDS after 24h ofincubation under optimized conditions of biodegradation. The results presented in this researchindicate that Pseudomonas aeruginosa is a suitable candidate for SDS biodegradation.

Influence of Cyclopentane and SDS on Methane Separation from Coal Mine Gas by Hydrate Crystallization

The influence of cyclopentane (CP) on methane separation from low-concentration coal mine gas (30% CH4, 60% N2, and 10% O2) by gas hydrate formation was investigated in the present work. Overpressure was used as the driving force. Experiments were carried out at 286.6 K and (2.0–5.0) MPa, and the cyclopentane concentration was fixed at 7.0 wt %. The experimental results indicated that the gas uptake increased with the increase of driving force, but the methane recovery decreased with the increase of driving force. A ∼ 6% higher methane recovery was obtained under the low driving force ΔP = 1.5 MPa as compared to that obtained in the presence of tetra-n-butyl ammonium bromide (∼ 27%). Then, the anionic surfactant sodium dodecyl sulfate (SDS) was employed to enhance hydrate formation from low-concentration coal mine gas in the presence of cyclopentane. Surface tensions of the solution (H2O/CP/SDS) were measured under different SDS concentrations and reported. It was found that gas uptake and the rate of hyd...

Surfactant flushing remediation of toluene contaminated soil: Optimization with response surface methodology and surfactant recovery by selective oxidation with sulfate radicals

Surfactants are usually used in remediation of subsoil and aquifers contaminated with hydrophobic organic compounds (HOCs) such as benzene, toluene, ethylbenzene and xylenes (BTEX). Laboratory soil column experiments were conducted, using the anionic surfactant sodium dodecyl sulfate (SDS), to optimize toluene removal efficiency from contaminated soil. The influence of flushing time, SDS concentration and flow velocity on toluene removal efficiency was investigated. In the column tests the maximum toluene removal efficiency of 89.9% was achieved with 2% (wt/vol) SDS solution and 5mL/min flow velocity for 300min. Response surface methodology (RSM) based on Box–Behnken statistical experiment design (BBD) was applied to analyze the experimental variables which all showed a positive effect on toluene removal efficiency. The interactions between SDS concentration and flushing time or flow velocity were significant, while the interaction of flushing time with flow velocity was not pronounced. Under optimal conditions, the predicted and observed removal efficiencies were 96.2% and 91.0% respectively. The results confirmed that the proposed models were accurate and reliable for the analysis of the variables of surfactant flushing treatment. Furthermore, the use of the UV/S2O82- selective oxidation process was proposed for surfactant recovery and degradation of contaminant present in the solution collected. It was found that after 270min of treatment toluene was 90.1% degraded for the second time the surfactant was used and 94.7% for the third time. In addition, a test in which the regenerated solution was employed in the flushing process was carried out in a soil column. The results indicated that the UV/S2O82- oxidation process was potentially effective in selective degradation of toluene with most of the surfactant left for potential reuse in another polluted soil treatment.

Thermodynamic Properties of Poly(ethenol) with and without Sodium Dodecyl Sulfate by Viscosity, Surface Tension, and Dynamic Light Scattering

We investigate the thermodynamic properties of a water-soluble polymer poly(ethenol) (PVOH) with and without ionic surfactant sodium dodecyl sulfate (SDS) by viscosity, surface tension, and dynamic light scattering (DLS) measurements at 298 K. The viscosity, refractive index, and hydrodynamic radius values of polymer PVOH aqueous solutions without surfactant SDS increase with increasing PVOH concentration, but the surface tension of PVOH aqueous solution decreases with increasing PVOH concentration. For SDS+PVOH aqueous solutions, both viscosity and surface tension values decrease with an increase of SDS concentration when SDS concentration is lower than the critical aggregation concentration (CAC) of SDS+PVOH aqueous solutions, and the relative minimum viscosity value indicated the shrinkage of the polymer PVOH chain resulting in the formation of compact structure at the binding site of SDS+PVOH. But the viscosity increases with an increase of SDS concentration when surfactant SDS concentration is larger...

Effects of Surfactants on the Purple Membrane and Bacteriorhodopsin: Solubilization or Aggregation?

Using steady-state spectroscopic and zeta potential methods, we have unraveled the interaction of the purple membrane (PM) and bacteriorhodopsin (bR) with various surfactants below their critical micelle concentrations. We found that the charged hydrophilic heads of ionic surfactants play a role in perturbing the structure and conformation of PM and bR and that ionic surfactants of opposite charges cause opposing effects. Specifically, the addition of a low concentration (0.2 mM) of the cationic surfactant cetyl trimethylammonium bromide (CTAB) is capable of neutralizing the negatively charged lipids on the PM surface via electrostatic forces. This results in increased hydrophobicity of PM that leads to the aggregation of PM. In contrast, denaturation of PM and bR was observed when the anionic surfactant sodium dodecyl sulfate (SDS) was added to the PM suspensions. The attachment of SDS to the PM surface increases the solubility of PM and causes a loose crystalline structure. As the SDS concentration is increased to more than 3 mM, the secondary structure of the constituents of bR is significantly distorted, and the protonated Schiff base is hydrolyzed to form free retinal. The addition of the neutral surfactant diethylene glycol mono-n-hexyl ether (C6E2) does not significantly influence the PM and bR, meaning most of their original properties are preserved. We conclude that the addition of surfactants might cause the aggregation or solubilization of the membrane protein, depending on the signs of the charged hydrophilic heads of the surfactants and the charges of the membrane protein surface. Aggregation results when the surfactant and protein have opposite charges, whereas solubilization results when the surfactant and protein have the same charge.

Interactions of PAMAM Dendrimers with SDS at the Solid–Liquid Interface

This work addresses structural and nonequilibrium effects of the interactions between well-defined cationic poly(amidoamine) PAMAM dendrimers of generations 4 and 8 and the anionic surfactant sodium dodecyl sulfate (SDS) at the hydrophilic silica-water interface. Neutron reflectometry and quartz crystal microbalance with dissipation monitoring were used to reveal the adsorption from premixed dendrimer/surfactant solutions as well as sequential addition of the surfactant to preadsorbed layers of dendrimers. PAMAM dendrimers of both generations adsorb to hydrophilic silica as a compact monolayer, and the adsorption is irreversible upon rinsing with salt solution. SDS adsorbs on the dendrimer layer and at low bulk concentrations causes the expansion of the dendrimer layers on the surface. When the bulk concentration of SDS is increased, the surfactant layer consists of aggregates or bilayer-like structures. The adsorption of surfactant is reversible upon rinsing, but slight changes of the structure of the preadsorbed PAMAM monolayer were observed. The adsorption from premixed solutions close to charge neutrality results in thick multilayers, but the surface excess is lower when the bulk complexes have a net negative charge. A critical examination of the pathway of adsorption for the interactions of SDS with preadsorbed PAMAM monolayers and premixed PAMAM/SDS solutions with hydrophilic silica revealed that nonequilibrium effects are important only in the latter case, and the application of a thermodynamic model to such experimental data would be inappropriate.

Photolysis of bisphenol S in aqueous solutions and the effects of different surfactants

The photolysis of bisphenol S (BPS) in aqueous solutions was studied under a 20 W UV lamp (λ = 254 nm). The proposed intermediates and possible photolysis pathways of BPS were analyzed, and the effect of three surfactants on this photolysis was determined. UV and liquid chromatography combined with ion-trap time-of-flight mass spectrometry analyses revealed that BPS photolysis mainly occurred in two steps, and the primary photodegradation intermediates or products were p-hydroxybenzenylsulfonic acid, p-hydroxyphenol, and sulfuric acid. The results showed that BPS photolysis fitted well to a first order kinetic equation. The surfactants did not directly participate in BPS photolysis and exerted different effects depending on the structure and concentration of surfactants. The anionic surfactant sodium dodecyl sulfate (SDS) exhibited a strong inhibiting effect on BPS photolysis that increased with increased SDS concentration. At 800 mg/L SDS, the half-life of BPS photolysis was prolonged from 91.2 to 150.7 min and the inhibiting ratio of SDS was 39.5 %. By contrast, the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) showed a promoting effect on BPS photolysis that increased with increased CTAB concentration. At 120 mg/L CTAB, the half-life of BPS photolysis shortened from 91.2 to 63.0 min and the promoting ratio was 44.7 %. On the other hand, the nonionic surfactant polyoxyethylene lauryl ether (PLE) had a relatively weak inhibiting effect at 140 mg/L PLE. At 240 mg/L, the promoting ratio reached 7.9 %.

Influence of water-insoluble nonionic copolymer E6P39E6 on the microstructure and self-aggregation dynamics of aqueous SDS solution—NMR and SANS investigations

The influence of water-insoluble nonionic triblock copolymer PEO-PPO-PEO [poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)] i.e., E6P39E6 with molecular weight 2800, on the microstructure and self-aggregation dynamics of anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution (D2O) were investigated using high resolution nuclear magnetic resonance (NMR) and small-angle neutron scattering (SANS) measurements. Variable concentration and temperature proton ((1)H), carbon ((13)C) NMR chemical shifts, (1)H self-diffusion coefficients, (1)H spin-lattice and spin-spin relaxation rates data indicate that the higher hydrophobic nature of copolymer significantly influenced aggregation characteristics of SDS. The salient features of the NMR investigations include (i) the onset of mixed micelles at lower SDS concentrations (<3 mM) relative to the copolymer-free case and their evolution into SDS free micelles at higher SDS concentrations (~30 mM), (ii) disintegration of copolymer-SDS mixed aggregate at moderate SDS concentrations (~10 mM) and still binding of a copolymer with SDS and (iii) preferential localization of the copolymer occurred at the SDS micelle surface. SANS investigations indicate prolate ellipsoidal shaped mixed aggregates with an increase in SDS aggregation number, while a contrasting behavior in the copolymer aggregation is observed. The aggregation features of SDS and the copolymer, the sizes of mixed aggregates and the degree of counterion dissociation (α) extracted from SANS data analysis corroborate reasonably well with those of (1)H NMR self-diffusion and sodium ((23)Na) spin-lattice relaxation data.

PH Regulation of the Kinetic Stability of the Lipase fromThermomyces lanuginosus

Thermomyces lanuginosus lipase (TlL) is a kinetically stable protein, resistant toward both denaturation and refolding in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant decyl maltoside (DecM). We investigate the pH dependence of this kinetic stability. At pH 8, TlL remains folded and enzymatically active at multimillimolar surfactant concentrations but fails to refold from the acid urea-denatured state at submillimolar concentrations of SDS and DecM, indicating a broad concentration range of kinetic trapping or hysteresis. At pH 8, very few SDS molecules bind to TlL. The hysteresis SDS concentration range shrinks when moving to pH 4-6; in this pH range, SDS binds as micellelike clusters. Although hysteresis can be eliminated by reducing disulfide bonds, destabilizing the native state, and lowering the unfolding activation barrier, SDS sensitivity is not directly linked to intrinsic kinetic stability [its resistance to the general chemical denaturant guanidinium chloride (GdmCl)], because TlL unfolds more slowly in GdmCl at pH 6.0 than at pH 8.0. However, the estimated net charge drops from approximately -12 to approximately -5 between pH 8 and 6. SDS denatures TlL at pH 6.0 by nucleating via a critical number of bound SDS molecules on the surface of native TlL to form clusters. These results imply that SDS sensitivity is connected to the availability of appropriately charged regions on the protein. We suggest that conformational rigidity is a necessary but not sufficient feature of SDS resistance, because this has to be combined with sufficient negative electrostatic potential to avoid extensive SDS binding.

Spectroscopic studies of dye-surfactant interactions with the co-existence of heavy metal ions for foam fractionation

The interaction between a cationic dye Methylene Blue (MB) and an anionic surfactant sodium dodecyl sulfate (SDS) with the presence of Cd2+ was investigated spectrophotometrically in a certain concentration range. The spectrophotometric measurements of dye-metal ion-surfactant system were carried out. The results indicated that the SDS concentration had a significant influence on the dye spectrum, while the addition of Cd2+ hardly caused change of the maximum value of absorbance. According to this observation, we concluded that electrostatic and hydrophobic interaction between dye and surfactant occurred up to a certain level, and the homo-ions Cd2+ almost exerted no effect on the dye-surfactant complexation, establishing a theoretical foundation for simultaneous removal of organic dye and heavy metal using foam fractionation. Meanwhile, the effects of their interaction on foam performance were investigated. The results showed that the addition of Cd2+ favored the tendency to ameliorate foam properties just contrary to MB. The feasibility of foam separation for dye and heavy metal removal from simulated wastewater was also confirmed using a continuous foam fractionator. In the simultaneous removal process, with the initial SDS concentration ranging from 0.5 to 5.0 mmol/L, the maximum removal efficiencies of MB and Cd2+ were obtained as 99.69% and 99.61%, respectively. The enrichment ratios were reduced from 24.34 to 7.65 for MB and from 22.01 to 3.35 for Cd2+.

Effect of Sodium Dodecyl Sulfate on Surface Roughness and Nucleation Mechanisms of Electrodeposited CuInSe2 Films

In this study, the p-type CuInSe2 thin films were fabricated by using pulse electrodeposition with anionic surfactant sodium dodecyl sulfate (SDS) as an additive. The effect of the SDS on the surface roughness and the nucleation mechanisms of electrodeposited CuInSe2 films have been investigated in detail. It was found that films fabricated in electrolyte containing SDS surfactant are smooth and compact compared to those fabricated in electrolyte without the SDS surfactant. AFM images show that the self-assembly of SDS molecules can form directional and oblique lines lying on the Mo surface. These oblique lines can form a monolayer to change the nucleation mechanisms of films from the instantaneous to the progressive mode. The vibration modes of the chalcopyrite structure and the identification of CuxSe secondary phases were examined by micro-Raman spectrometry, which showed a decrease in secondary phases when SDS concentration was increased from 0.3 mM to 5 mM.

The effect of sodium dodecyl sulfate surfactant on the electrodeposition of Ni-alumina composite coatings

Nickel–alumina nano-composite coatings were obtained from nickel sulphamate solution containing nano-α-alumina particles by direct current (DC) plating. Nano-alumina particles were dispersed in the solution with the aid of different concentrations (50–300 mg l−1) of the anionic surfactant sodium dodecyl sulfate (SDS) by ultrasonic method. The microhardness variation of the coatings in different concentrations of SDS was investigated. Furthermore, the corrosion behavior of composite coatings was studied by polarization measurements in 3.5% w/v NaCl solution. The results revealed that increasing the surfactant concentration, up to an optimum value (125 mg l−1), led to more uniform distribution of nano-particles in the coatings, improved corrosion potential (Ecorr) to the most positive value (−0.209 V) and corrosion current density (icorr) to the lowest value (1.141 × −7 A cm−2), and enhanced the microhardness of composite coatings to 492 HV. However, beyond this optimum level, these properties were attenuated.

Conductometric study of the complex system polyelectrolyte/surfactant in aqueous solution

In this work, the interaction between the anionic surfactant sodium dodecyl sulfate (SDS) and the polyelectrolyte complex hydrolyzed polyacrylamide/poly(4-vinylpyridine) (AD37–P4VP) in aqueous solution was investigated by conductometric measurements. Three main series with SDS concentrations of 0.01, 0.25 and 1 % and in a wide range of P4VP and AD37 concentrations, from 0.1 × 10−4 to 4 × 10−4 g/ml, and from 10−4 to 10−3 g/ml, respectively, were studied. The polyelectrolyte complex interacts strongly with the SDS surfactant. These interactions are of electrostatic and hydrophobic types. Thus, the effect of salt on the critical micelle concentration of SDS, and the neutralization degree on behavior conductivity of the mixture, were quantified.

Ultrafast electron transfer in riboflavin binding protein in macromolecular crowding of nano-sized micelle

In this contribution, we have studied the dynamics of electron transfer (ET) of a flavoprotein to the bound cofactor, an important metabolic process, in a model molecular/macromolecular crowding environments. Vitamin B(2) (riboflavin, Rf) and riboflavin binding protein (RBP) are used as model cofactor and flavoprotein, respectively. An anionic surfactant sodium dodecyl sulfate (SDS) is considered to be model crowding agent. A systematic study on the ET dynamics in various SDS concentration, ranging from below critical micellar concentration (CMC), where the surfactants remain as monomeric form to above CMC, where the surfactants self-assemble to form nanoscopic micelle, explores the dynamics of ET in the model molecular and macromolecular crowding environments. With energy selective excitation in picosecond-resolved studies, we have followed temporal quenching of the tryptophan residue of the protein and Rf in the RBP-Rf complex in various degrees of molecular/macromolecular crowding. The structural integrity of the protein (secondary and tertiary structures) and the vitamin binding capacity of RBP have been investigated using various techniques including UV-Vis, circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) studies in the crowding environments. Our finding suggests that the effect of molecular/macromolecular crowding could have major implication in the intra-protein ET dynamics in cellular environments.

Aqueous Redox Reaction of SDS-Encased Carbon Nanotubes with Mercuric Ions for Optical Sensing

The redox reaction and the pseudo first-order reaction kinetics of single-walled carbon nanotubes (SWNTs) dispersed in solution of a surfactant sodium dodecyl sulfate (SDS) have been studied with Hg2+ ions. The reaction is monitored by using the unique near-infrared optical absorption properties of SWNTs. Various factors including SDS and SWNT concentrations, different pH levels, and buffer constituents have been systematically examined. It is found that the reactivity is sensitive to the concentrations of SDS and SWNTs, with an optimum at 1 wt % SDS and 0.1 mg/mL SWNTs. The reaction is pH sensitive as well, and the reactivity is higher at lower pHs. The suppressed SWNT spectral intensity by the redox reaction can be recovered by adjusting pH, enabling the reusability of SWNTs. SWNTs show high selectivity and sensitivity on Hg2+ over eleven other metal ions. The determined detection limit is 0.6 nM, lower than 10 nM, the maximum contaminant level for mercuric ions in drinking water. This work may provide insights for developing new SWNT-based optical sensors for mercuric ion detection.

Coupled synthesis and encapsulation in one-pot method for fabricating size-tunable hollow carbon spheres containing encapsulated Ag microparticles

Size-tunable hollow carbon spheres containing encapsulated Ag microparticles (HCSA) were fabricated using a one-pot method for the coupled synthesis and encapsulation. These spheres were formed by the catalyzed dehydration of glucose under hydrothermal conditions, using the anionic surfactant sodium dodecyl sulfate (SDS) as a sacrificial template to tune the cavity size of the hollow carbon spheres. In this one-pot synthesis, glucose was used as the carbonaceous source and served as the reducing agent that reacted with Ag ions. The HCSA exhibited tunable cavity sizes (1.2–2.4μm), dimensions (0.2–2.7μm), and morphologies (hollow spherical, bowl-like, ruptured, or solid spherical). The obtained products were characterized using X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, and nitrogen adsorption/desorption analysis. On the basis of the results obtained in this study, we suggest that the SDS concentration is the crucial factor in the fabrication of size-tunable HCSA. In addition, we propose a possible mechanism for the formation of the HCSA.

Kinetic investigation on the oxidation of tris(1,10-phenanthroline)iron(II) by oxone: The effect of BSA–SDS interaction

The kinetic investigations of oxidation of tris(1,10-phenanthroline)iron(II) by oxone have been studied spectrophotometrically in phosphate buffer medium of pH 6.8, temperature 308K, and ionic strength 0.25molL−1. The reactions were also carried out in presence of globular transport protein, bovine serum albumin (BSA) having isoelectric point 4.9, anionic surfactant sodium dodecyl sulfate (SDS), and their mixtures. The critical aggregation concentration (CAC) and critical micelle concentration (CMC) of SDS in presence of BSA have been determined using conductivity and kinetic measurement techniques. The secondary structure of BSA was examined by Circular Dichroism (CD) measurement at 308K. The helix nature of BSA decreases with increase of SDS concentration. The effect of pH on rate in presence of BSA is opposite to its absence, and the effect of urea on rate in presence of BSA indicates the denaturation of BSA. The results depict that amphiphile SDS interacts with BSA and different molecular events, for example, specific binding, cooperative binding, protein unfolding, and micelle formation act. Activation parameters of the reaction in different environments have been determined.

Effect of Architecture on the Formation of Surface Multilayer Structures at the Air–Solution Interface from Mixtures of Surfactant with Small Poly(ethyleneimine)s

The impact of ethyleneimine architecture on the adsorption behavior of mixtures of small poly(ethyleneimines) and oligoethyleneimines (OEIs) with the anionic surfactant sodium dodecylsulfate (SDS) at the air-solution interface has been studied by surface tension (ST) and neutron reflectivity (NR). The strong surface interaction between OEI and SDS gives rise to complex surface tension behavior that has a pronounced pH dependence. The NR data provide more direct access to the surface structure and show that the patterns of ST behavior are correlated with substantial OEI/SDS adsorption and the spontaneous formation of surface multilayer structures. The regions of surface multilayer formation depend upon SDS and OEI concentrations, on the solution pH, and on the OEI architecture, linear or branched. For the linear OEIs (octaethyleneimine, linear poly(ethyleneimine) or LPEI(8), and decaethyleneimine, LPEI(10)) with SDS, surface multilayer formation occurs over a range of OEI and SDS concentrations at pH 7 and to a much lesser extent at pH 10, whereas at pH 3 only monolayer adsorption occurs. In contrast, for branched OEIs BPEI(8) and BPEI(10) surface multilayer formation occurs over a wide range of OEI and SDS concentrations at pH 3 and 7, and at pH 10, the adsorption is mainly in the form of a monolayer. The results provide important insight into how the OEI architecture and pH can be used to control and manipulate the nature of the OEI/surfactant adsorption.

Surfactant-Induced Marangoni Eddies Alter the Coffee-Rings of Evaporating Colloidal Drops

The influence of the small ionic surfactant sodium dodecyl sulfate (SDS) on the evaporation of drying colloidal droplets is quantitatively investigated. The addition of SDS leads to a significantly more uniform deposition of colloidal particles after evaporation (i.e., the so-called "coffee-ring effect" is dramatically altered). We understand this phenomenon in the context of circulating radial Marangoni flows induced by the variation of SDS concentration along the air-water interface. Video microscopy permits the direct visualization of the colloidal particles involved in these flows, revealing a surprisingly stable "Marangoni eddy" that prevents particle deposition at the drop perimeter.

An aqueous anionic/nonionic surfactant two-phase system in the presence of salt. 1. Rheological behavior and microstructure

Aqueous binary surfactant solutions, based on the cloud point phenomenon, have been utilized to design efficient extraction of a variety of substances. In this study, the effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the clouding behaviour of aqueous nonionic surfactant solutions of Triton X-114 (TX-114), in the presence of 100 mM sodium chloride (NaCl), has been studied as a function of temperature by means of turbidity, dynamic light scattering (DLS), and rheo-small angle light scattering (Rheo-SALS). It is found that the addition of 2 mM SDS lowers the phase separation temperature of the surfactant solution by about 2 °C. The hydrodynamic radius of the surfactant aggregates increases with increase of temperature and SDS concentration. The change in microstructure of the surfactant aggregates at different temperature and SDS concentrations is also reflected by the characteristic length and aspect ratio extracted from their SALS patterns, which range from 269 to 623 nm and from 1.01 to 1.40, respectively. The increasing characteristic length and aspect ratio with SDS concentration indicate the growth of the mixed surfactant aggregates is in the flow direction and these elongated aggregates can align under shear.