Solutions Of Surfactant Sodium Dodecyl Sulfate Research Articles

Physicochemical investigations on the interaction of an anionic surfactant with cellulose based polymer microgel

Abstract This work focuses on the interaction of cellulose-based colloidal microgel dispersions with the anionic surfactant sodium dodecyl sulfate (SDS) at different concentrations. First, a Cellulose-P(NIPAAm-MAA)-based responsive microgel sample was prepared by a radical polymerization method using a one-pot process. The samples thus obtained were purified, characterized and used to study microgel-surfactant interactions. To this end, SDS solutions with different concentrations were prepared and the interactions of SDS in the premicellar and micelle regions with polymer microgel were investigated using different physicochemical techniques. Experiments were also performed at different temperatures to obtain the degree of binding of SDS to microgel in gel surfactant mixtures. Due to the temperature-sensitive properties of microgel, we observed significant changes in various properties of microgel-surfactant mixtures when the solution temperature changed. The overall results showed that various experimental variables, such as the polymer gel/surfactant ratio and temperature, affect the gel–surfactant interaction quantitatively and qualitatively. With increasing surfactant concentration, conductance, viscosity and absorbance values ​​increased, but a decrease in surface tension was observed. This is due to the adsorption of SDS at the air-water interface. The micellar activity of surfactants is enhanced by the addition of microgels. It was found that the strength and nature of the interaction depended not only on the gel/surfactant ratio, solvent type and test temperature, but also on the chemical structure of the surfactant used. Furthermore, the visual stability of the colloidal particles in the mixture of microgel and SDS was also noticeable over time.

Aqueous liquid chromatography with mobile phases of sodium dodecyl sulphate and ionic liquid

In conventional reversed-phase liquid chromatography (RPLC) with hydro-organic solvents, basic cationic solutes yield retained, broad, asymmetric peaks, owing to their interaction with free anionic silanols in the stationary phase. RPLC mobile phases to which the anionic surfactant sodium dodecyl sulphate (SDS), or an ionic liquid (IL) are added, have been proposed as solutions, since these additives are able to block the silanol effect thus improving the chromatographic performance. With these additives, it is however necessary to increase the elution strength by adding an organic solvent, such as an alcohol or acetonitrile. A novel aqueous liquid chromatographic mode (in the absence of organic solvent) is here proposed, where the mobile phases contain only a mixture of aqueous solutions of SDS and an IL derived from 1-alkyl-3-methylimidazolium associated to chloride, both environmentally friendly. When these reagents are added, the anionic surfactant adsorbed on the stationary phase is able to attract the cationic solutes, whereas the adsorbed IL cation repels them. The combination of both effects (attraction and repulsion) allows the modulation of retention, by varying the IL/SDS ratio. Given the character of the additives, a type of green liquid chromatography is achieved. In this work, the chromatographic behavior of six basic compounds of pharmaceutical interest, the β-adrenoceptor antagonists acebutolol, atenolol, carteolol, metroprolol, oxprenolol and propranolol, is examined. In order to assess the chromatographic behavior of the mixed mobile phases containing SDS and IL, changes in retention, peak profile and resolution of mixtures of the analytes were explored at varying concentration of the additives.

Enhance hydrates formation with stainless steel fiber for high capacity methane storage

In order to realize efficient gas storage of hydrate, stainless steel fiber (SSF) was added to 0.03% (mass) sodium dodecyl sulfate (SDS) solution for gas storage experiment. SSF can not only improve the problem that hydration heat cannot be removed effectively in the hydration process, but also improve gas storage speed and gas storage by increasing hydrate nucleation sites. Under the experimental conditions (273.2 K, 5–9 MPa), the peaks of temperature rise in SDS + SSF systems were found to become much smaller than those in SDS systems. The maximum gas storage rate and the maximum methane uptake of SSF + SDS system reached 9.89–24.90 cm 3 ·g −1 ·min −1 and 178.65–200.89 cm 3 ·(g H 2 O) −1 , respectively. Compared with the surfactant SDS solution without SSF, they increased by 10.47%–33.22% and 9.16%–25.36%, respectively. The effect of SSF length on gas storage performance was studied. Due to the continuous thermal conduction network, longer SSF showed a higher gas storage capacity and methane uptake rate compared with shorter SSF. At the same time, compared with other metal fillers, SSF + SDS not only had excellent gas storage performance, but also the amount of SSF (0.1 g·ml −1 ) was only 7.6% of foamed aluminum, and the volume gas storage density was increased by 145.4%. The use of stainless steel fiber made the best use of the thermal conductivity of metal, reduced the amount of metal used, and improved the volume density and mass density of gas storage.

Thermal detection of second critical micelle concentration in SDS and CTAB aqueous solutions using a modified Lewis-Nielsen effective thermal model

When surfactant molecules are in solution, they self-assemble into various configurations, with the structural conformation changing upon concentration, temperature, and pH. The thermal transport of aqueous solutions containing anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant hexadecyltrimethylammonium bromide (CTAB) was investigated using the thermal wave resonant cavity (TWRC) technique. We use the Lewis-Nielsen effective thermal conductivity model to explain the observed behavior in a new way. We consider that the form factor of the Lewis-Nielsen model relies entirely on surfactant concentration rather than being a constant, as initially was proposed by Lewis and Nielsen. Our findings indicate that the proposed method can detect the transition between spherical and rod-like surfactant micelles. Additionally, this technique could be used to calculate the thermal conductivity of surfactant molecules in water.

High-efficiency emulsification anionic surfactant for enhancing heavy oil recovery

A high-efficiency anionic surfactant alcohol ethoxylate sodium hydroxypropyl sulfonate (AEOSHS) suitable for enhancing heavy oil recovery has been synthesized through chemical modification. Its structure and properties were characterized by FT-IR, TGA and SFT. Then, the performance of surfactant AEOSHS was better than traditional anionic surfactant sodium dodecyl sulfate (SDS) confirmed through emulsification state observation, droplet size distribution test, interfacial tension (IFT) test, rheological test and porous level emulsification visualization observation. The mechanism of surfactant AEOSHS to efficiently emulsify heavy oil and W/O emulsion was clarified. Finally, the enhancing heavy oil recovery of surfactant SDS and AEOSHS was compared through long sand-packed tube flooding experiment. Experimental results show that when surfactant concentration was 0.5%, the IFT between surfactant SDS solution and dehydrated heavy oil was 0.34 mN/m, while the IFT of AEOSHS was only 0.092 mN/m. As water content of W/O emulsion increase, its density, viscosity and IFT were all increase. Surfactant AEOSHS molecule can dissolved in heavy oil because the long carbon chain and the existence of ether bonds. It can effectively disperse the layer stacking structure of resin and asphaltene so that water in W/O emulsion can be effectively emulsified. In addition, surfactant AEOSHS can emulsify heavy oil into small droplets (7.1 µm), which has high elastic modulus, so that the additional resistance was very small when it flows through porous media. Through flooding experiments, which shown that surfactant AEOSHS (0.5PV) can enhancing heavy oil recovery rate up to 18.17%, while SDS was only 8.71%. Therefore, the newly synthesized anionic surfactant AEOSHS has the ability to significantly reduce IFT and high-efficiency emulsification, and can be used for enhancing heavy oil recovery.

Screening of a Novel Solvent for Optimum Extraction of Anionic Surfactants in Water.

Anionic surfactants (AS) are detrimental aquatic pollutants due to their well-characterized toxicity to aquatic organisms. The concentration of AS in aquatic environments is increasing because of their extensive use in many industries and households. The standard reference method for AS analysis is to determine a methylene blue active substance (MBAS) complex formed between AS and the methylene blue (MB) cation by using chloroform. However, chloroform has a low AS extraction efficiency and other limiting properties, such as a high density and volatility, which make the conventional AS analytical method time-consuming and labor-intensive. In an effort to replace the use of chloroform, this study was carried out to screen novel solvents for their ability to extract AS in water samples. Criteria were based on AS extraction efficiency, physicochemical properties, and the stability of the solvent under different environmental conditions. Organic solvents, such as methyl isobutyl ketone (MIBK), 1,2-dichloroethane (DCE), dichloromethane, benzene, and n-hexane, were assessed. In extraction of the anionic surfactant sodium dodecyl sulfate (SDS), the mixture of MIBK-DCE (3:1) proved to be an optimum solvent as an alternative to chloroform. It not only enhanced SDS extractability but also improved properties, such as having a lower volatility, a lower density than water, and a quicker phase separation. Among solvents screened, no one single solvent in SDS extraction could meet such criteria. The performance of the MIBK-DCE (3:1) mixture in SDS extraction was stable, irrespective of pH and ionic strength of the SDS solution, washing process, and presence of cations. Anionic interference from halogen and polyatomic and organic anions in SDS extraction by MIBK-DCE (3:1) existed only at an elevated concentration, which is not occurring in the natural aquatic environment. Results demonstrated that a MIBK-DCE (3:1) mixture solvent could be used in AS analysis for a wide range of aquatic samples and it could be the basis for the development of a new analytical method to replace conventional chloroform.

Study on the effect of imidazolium ionic liquid as a modulator of corrosion inhibition of anionic surfactant sodium dodecyl sulfate (SDS) on mild steel in sodium chloride solution

Present paper reports investigation done on two organic compounds to test them as corrosion inhibitors for mild steel exposed to neutral NaCl solution. Organic compounds capable of corrosion inhibition must form a protective film over the metal surface. This is usually possible since many of these organic compounds possess strong interaction properties with metal and get adsorbed over its surface. These organic compounds contain electronegative functional groups and atoms like S, N, P, and O, which form center for establishment of adsorption process. Accordingly, SDS and DMImCl were chosen as organic compounds to test as corrosion inhibitors. Electrochemical polarization tests, performed in this study, reveal decrease in corrosion rate of mild steel in NaCl solution by 14.3 to 6.08 mpy (mils per year) corresponding to increased inhibition efficiency of 57.3% on addition of up to 200 ppm SDS. On mixing 200 ppm of DMImCl in NaCl + SDS solution, the inhibition efficiency enhances to 85.1%. Similar outcome is also noticed from Electrochemical impedance and weight loss test results. Analysis of results obtained through FTIR, SEM/EDAX indicate adsorption of SDS/DMImCl mixture on the mild steel surface.Tensiometry tests, on ionic solution, reveal decrease in surface tension on addition of inhibitors with consequently increased surface activity and hydrophobic interaction between chains of the two inhibitors. Calculation done on the adsorption process indicates it to be ‘Langmuir adsorption isotherm’. This inference suggests that binding sites on steel surface are identical and homogeneously distributed. This layer is covered with a monolayer of adsorbed molecules i.e. DMImCl and SDS which is responsible for corrosion inhibition.

Wetting and Drying of Aqueous Droplets Containing Nonionic Surfactants CnEm.

This paper presents a systematic study of the wetting and drying of aqueous pico-liter droplets containing nonionic surfactants polyoxyethylene alkyl ethers (CnEm; n = 10, 12, 14, m = 6 or 8) in comparison with the anionic surfactant sodium dodecyl sulfate (SDS). The spreading and drying of droplets on hydrophilic substrates were studied by tracking the three-phase contact line (TCL) and by interferometry. CnEm droplets undergo phase separation during drying: a water-rich droplet retracts and leaves behind a thin film that is postulated to be a surfactant mesophase. This thin film either retracts or breaks up into small droplets on a longer time scale. The receding contact angle of the water-rich droplet on the thin film in the late stage of drying of CnEm droplets is independent of hydrophobicity of substrates, supporting the inference that a mesophase is present on the surface. Both CnEm and SDS solutions inhibit spreading on hydrophilic surfaces, which is attributed to Marangoni contraction as a result of a surface tension gradient across the gas-liquid interface. More pronounced suppression of spreading is observed in the case of CnEm solutions, possibly due to the phase transition of surfactant solution in the vicinity of the initial TCL leading to a viscous phase at the TCL that pins the droplet. Tracer particle measurements reveal that mild Marangoni flows exist for droplets with surfactant concentrations well above the critical micelle concentration (CMC). Origins of the surfactant gradients that result in Marangoni flows are discussed.

A Study on the Fluorescence Properties of New Laser Material-n-B18H22 in SDS Aqueous Solution

The effect of anionic surfactant sodium dodecyl sulfate (SDS) on the fluorescence of n-B18H22 was studied. The experimental result revealed that the fluorescence of n-B18H22 was obviously enhanced with the increase of the concentration of SDS, mainly due to the hydrophobic protection of n-B18H22 by SDS. Under the optimum conditions, the fluorescence intensity was proportional to the concentration of n-B18H22 in the range of 0-8.0×10−3 mol·L−1 and 8.0×10−3 mol·L−1-3.3×10−2 mol·L−1, respectively. It was observed that a break appeared in the curve of fluorescence intensity with surfactant concentration. The critical micelle concentration (CMC, 7.9×10−3 mol·L−1) of SDS was obtained from this break point in a good agreement with the reported value. The fluorescence intensity increased initially with time and gradually stabilized. The results form the basis for further study of the properties and application of n-B18H22 in SDS solutions.

ФЕРМЕНТАТИВНА АКТИВНІСТЬ РЯДУ ОКСИДОРЕДУКТАЗ ЯК ПОКАЗНИК ЗБЕРЕЖЕННЯ НАТИВНОЇ ПРИРОДИ БІЛКІВ У ГІДРОТРОП-ІНДУКОВАНІЙ ФАЗІ ДОДЕЦИЛСУЛЬФАТУ НАТРІЮ

Preserving the proteins native nature after their extraction is a strict requirement in immuno-chemical analysis, medical and food industry at receiving concentrates of viruses, bacteria and proteins. Anionic surfactant sodium dodecyl sulfate (SDS) is the most common detergent that is used for extraction and preconcentration of proteins. However, using of SDS solution often leads to denaturation of proteins and loss of their functional activity. Hydrotrope-induced micellar phase of the SDS (SDS-NaCl-H2Sal) is considered as a rational alternative to classical extragens, due to its ability to quantitatively extract of proteins molecules at pH close to the isoelectric point of the protein (pI) and at conditions of their positively charged forms domination (pH ≤ pI). From our point of view, using of the SDS-NaCl-H2Sal phase can provide a stabilization of the native state of proteins after their preconcentration. The objective of the work was to evaluete the possibility of proteins native state preservation after their preconcentration into SDS hydrotrope-induced phase. Peroxidase, catalase and nitrate reductase were chosen as protein model substrates. The change in the catalytic activity of these oxidoreductases in SDS micellar phase was used as indicator of proteins native state preservation. The activity of peroxidase and catalase was determined by the method of permanganametometric titration as the amount of H2O2 that was decomposed under the action of the enzyme. The activity of nitrate reductase was determined spectrophotometrically by the reaction of Griess reagent with nitrite ions formed as a result of the enzymatic decomposition of nitrates. It has been established that the catalytic activity of peroxidase, nitrate reductase and catalase in the SDS micellar phase increases in two, three and four times in comparison with the aqueous solution, respectively. Such rising of oxidoreductases catalytic activities after their preconcentration into the hydrotrope-induced phase of SDS confirms the preservation of proteins native nature.

Self-Assembly of Oleyl Bis(2-hydroxyethyl)methyl Ammonium Bromide with Sodium Dodecyl Sulfate and Their Interactions with Zein.

Surface tension and aggregation behavior in an aqueous solution of the mixture of cationic surfactant oleyl bis(2-hydroxyethyl)methylammonium bromide (OHAB) and anionic surfactant sodium dodecyl sulfate (SDS) have been studied by surface tension, conductivity, turbidity, zeta potential, isothermal titration microcalorimetry (ITC), cryogenic transmission electron microscopy (Cryo-TEM), and dynamic light scattering. The mixture shows pretty low critical micellar concentration and surface tension, and successively forms globular micelles, unilamellar vesicles, multilamellar vesicles, rod-like micelles, and globular micelles again by increasing the molar fraction of OHAB from 0 to 1.00. The cooperation of hydrophobic interaction between the alkyl chains, electrostatic attraction between the headgroups as well as hydrogen bonds between the hydroxyethyl groups leads to the abundant aggregation behaviors. Furthermore, the solubilization of zein by the OHAB/SDS aggregates and their interactions were studied by ITC, total organic carbon analysis (TOC), and Cryo-TEM. Compared with pure OHAB or pure SDS solution, the amount of zein solubilized by the OHAB/SDS mixture is significantly reduced. It means that the mixtures have much stronger abilities in solubilizing zein. This result has also been proved by the observed enthalpy changes for the interaction of OHAB/SDS mixture with zein. Mixing oppositely charged OHAB and SDS reduces the net charge of mixed aggregates, and thus, the electrostatic attraction between the aggregates and zein is weakened. Meanwhile, the large size of the aggregates may increase the steric repulsion to the zein backbone. This work reveals that surfactant mixtures with larger aggregates and smaller CMCs solubilize less zein, suggesting how to construct a highly efficient and nonirritant surfactant system for practical use.

Measurements of the stabilisation of liquid film flow by the soluble surfactant sodium dodecyl sulfate (SDS)

Gravity-driven film flow of aqueous solutions of SDS is studied experimentally and the evolution of small-amplitude, regular inlet disturbances is investigated. With the addition of SDS, strong attenuation of non-linear growth is observed, with traveling waves remaining relatively small in height and near-sinusoidal over an impressive parametric range. The critical Reynolds number of the primary instability rises by an order of magnitude. Maximum stabilization is observed at small surfactant loadings (characterized by surface tension 60–65mN/m) and the critical Reynolds number gradually decreases with further addition of surfactant. Observations are interpreted by the competing effects of surface elasticity -which increases with the adsorbed SDS and intensifies Marangoni stresses- and surfactant mass transfer between bulk and interface -which also increases with the amount of SDS and mitigates interfacial gradients and Marangoni stresses.

Modeling Aggregation of Ionic Surfactants Using a Smeared Charge Approximation in Dissipative Particle Dynamics Simulations.

Using dissipative particle dynamics (DPD) simulations, we explore the specifics of micellization in the solutions of anionic and cationic surfactants and their mixtures. Anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyltrimethylammonium bromide (CTAB) are chosen as characteristic examples. Coarse-grained models of the surfactants are constructed and parameterized using a combination of atomistic molecular simulation and infinite dilution activity coefficient calibration. Electrostatic interactions of charged beads are treated using a smeared charge approximation: the surfactant heads and dissociated counterions are modeled as beads with charges distributed around the bead center in an implicit dielectric medium. The proposed models semiquantitatively describe self-assembly in solutions of SDS and CTAB at various surfactant concentrations and molarities of added electrolyte. In particular, the model predicts a decline in the free surfactant concentration with the increase of the total surfactant loading, as well as characteristic aggregation transitions in single-component surfactant solutions caused by the addition of salt. The calculated values of the critical micelle concentration reasonably agree with experimental observations. Modeling of catanionic SDS-CTAB mixtures show consecutive transitions to worm-like micelles and then to vesicles caused by the addition of CTAB to micellar solution of SDS.

Concentration dependent pore morphological tuning of kaolin clay foams using sodium dodecyl sulfate as foaming agent

Microstructural tailoring of kaolin foams was successfully performed from kaolin clay mineral by surfactant assisted foaming technique using the anionic surfactant sodium dodecyl sulfate (SDS). The foams were prepared via frothing of aqueous kaolin suspension with SDS solutions of different concentration and the stability of the foam was improved by insitu polymerization of methylol-urea to urea formaldehyde resin. Furthermore, the effect of surfactant concentration on slurry foaming characteristics and the corresponding change in the pore morphology of the dried foams were investigated. The result showed that the pore size, pore volume and interconnectivity changed with the increased amount of SDS. In addition, the role of SDS micellar stability on the frothing capacity and the analogous modification in the microstructure of final sintered foam were explained by a possible mechanism based on the variation of micellar stability with concentration.

Adsorption and surfactant-mediated desorption of poly(vinylpyrrolidone) on plasma- and piranha-cleaned silica surfaces.

Optical flow cell reflectometry was used to study the adsorption of poly(vinylpyrrolidone) (PVP) to a silica surface and the subsequent surfactant adsorption and polymer desorption upon exposure to the anionic surfactant sodium dodecyl sulfate (SDS). We have studied these effects as a function of pH and surfactant concentration, but also for two different methods of silica preparation, O2 plasma and piranha cleaning. As a function of pH, a plateau in the amount adsorbed of ∼0.6 mg/m(2) is observed below a critical pH, above which the adsorption decreases to zero within 2-3 pH units. An increase in pH leads to dissociation of surface OH groups and a decreased potential for hydrogen bonding between the polymer and surface. For the plasma- and piranha-cleaned silica, the critical pH differs by 1-2 pH units, a reflection of the much larger amount of surface OH groups on piranha-cleaned silica (for a given pH). Subsequent rinsing of the adsorbed layer of PVP with an SDS solution leads to total or partial desorption of the PVP layer. Any remaining adsorbed PVP then acts as an adsorption site for SDS. A large difference between plasma- and piranha-cleaned silica is observed, with the PVP layer adsorbed to plasma-cleaned silica being much more susceptible to desorption by SDS. For a plasma-cleaned surface at pH 5.5, only 30% of the originally adsorbed PVP is remaining, while for piranha-cleaned silica, the pH can be increased to 10 before a similar reduction in the amount of adsorbed PVP is seen. For a given pH, piranha-cleaned silica has a higher surface charge, leading to a smaller amount of adsorbed SDS per PVP chain on a piranha-cleaned surface compared to a plasma-cleaned surface under identical conditions. In that way, the high negative surface charge makes desorption by negatively charged SDS more difficult. The high surface charge thus protects the neutral polymer from surfactant-mediated desorption.

Competitive adsorption of the protein hydrophobin and an ionic surfactant: Parallel vs sequential adsorption and dilatational rheology

The competitive adsorption of the protein HFBII hydrophobin and the anionic surfactant sodium dodecyl sulfate (SDS) is investigated in experiments on parallel and sequential adsorption of the two components. The dynamic surface tension and the surface storage and loss dilatational moduli are determined by the oscillating bubble method. A new procedure for data processing is proposed, which allows one to collect data from many different runs on a single master curve and to determine more accurately the dependence of the dilatational elasticity on the surface pressure. Experiments on sequential adsorption are performed by exchanging the HFBII solution around the bubble with an SDS solution. Experiments with separate thin foam films bring additional information on the effect of added SDS. The results indicate that if HFBII has first adsorbed at the air/water interface, it cannot be displaced by SDS at any concentration, both below and above the critical micellization concentration (CMC). In the case of parallel adsorption, there is a considerable difference between the cases below and above the CMC. In the former case, SDS cannot prevent the adsorption of HFBII at the interface, whereas in the latter case adsorption of HFBII is absent, which can be explained with hydrophilization of the hydrophobin aggregates by the SDS in the bulk. The surface dilatational elasticity of the HFBII adsorption layers markedly decreases in the presence of SDS, but it recovers after washing out the SDS. With respect to their dilatational rheology, the investigated HFBII layers exhibit purely elastic behavior, the effect of dilatational viscosity being negligible. As a function of surface tension, the elasticity of the investigated interfacial layers exhibits a high maximum, which could be explained with the occurrence of a phase transition in the protein adsorption layer.

Interactions between Hydrophobically Modified Alkali-Swellable Emulsion Polymers and Sodium Dodecyl Sulfate Probed by Fluorescence and Rheology

The interactions between a pyrene-labeled hydrophobically modified alkali-swellable emulsion (Py-HASE) polymer and the anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution were investigated with a fluorometer, a rheometer, and a combination of both instruments to probe the fluorescence of the polymer while the solution was being sheared. Different amounts of SDS were added to two solutions with Py-HASE concentrations of 8 and 57 g/L. The pyrene monomer and excimer decays of the Py-HASE solutions were acquired and globally fitted according to the fluorescence blob model (FBM) and the model free (MF) analysis. Both models yielded the same molar fractions of pyrenes that were isolated, aggregated, or forming excimer by diffusion. The average number of pyrenes per micelle, <n>, was determined according to the FBM and found to equal 2.0 at the SDS concentration corresponding to a maximum in solution viscosity. For a Py-HASE concentration of 57 g/L, the solution viscosities at different SDS concentrations were measured from the Newtonian plateau regions and were found to peak at an SDS concentration of 11 mM. The steady-state fluorescence spectra were acquired at SDS concentrations of 0.1, 6.0, 11.1, and 17 mM while the 57 g/L Py-HASE solution was sheared. Although the solutions of Py-HASE and SDS were found to shear-thin substantially with the solution viscosity decreasing by up to 4 orders of magnitude, no change was observed in the fluorescence spectra acquired at shear rates ranging from 0.005 to 500 s(-1). The overlap of the fluorescence spectra under conditions where the solution viscosity decreased by 4 orders of magnitude suggested that the rearrangement of the hydrophobes from inter- to intramolecular associations that leads to shear-thinning occurs on a time scale that is much faster than that over which the rheology experiments are being conducted.

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.

Transport Properties of Water and Sodium Dodecyl Sulfate

In this work, results from atomistic molecular dynamics studies investigating the effect of surfactant concentration on the transport properties of bulk surfactant aqueous solutions, focusing on the anionic surfactant sodium dodecyl sulfate (SDS), are reported. The surfactant self-diffusion and the thermal conductivity of bulk aqueous SDS solutions were computed at a range of concentrations at room and boiling temperatures. Additionally, MP2f (Akin-Ojo et al., 2008, “Developing Ab Initio Quality Force Fields From Condensed Phase Quantum-Mechanics/Molecular-Mechanics Calculations Through the Adaptive Force Matching Method,” J. Phys. Chem., 129, p. 064108), one of a new generation water potentials is assessed for its suitability in reproducing the transport and thermal properties of bulk water. The thermal conductivity of MP2f water model was found to be: 0.64 W/(m⋅K) at 298 K and 0.66 W/(m⋅K) at 373 K, in much better agreement with the experimental values compared to both the rigid and the flexible TIP3P water model.

Effects of Surfactant and Polyelectrolyte on Distribution of Silicate Species in Alkaline Aqueous Tetraoctylammonium Silicate Solutions Using 29Si NMR Spectroscopy

In the present work, the structure-directing effect of the surfactant sodium dodecyl sulfate (SDS) on the distribution of the silicate species present in alkaline aqueous silicate solutions is studied using silicon-29 nuclear magnetic resonance (NMR) spectroscopy. Also, the distribution of silicate anions in the presence of polyelectrolytes is investigated using 29Si NMR spectroscopy through the use of different bases including tetraoctylammonium hydroxide and sodium hydroxide as templates (their cations) in these solutions. Both the SDS and polyelectrolytic solutions are shown to stabilize low molecular weight silicate species and thus inhibit polymerization.