Surfactant Sodium Lauryl Ether Sulfate Research Articles

Synthesis and Performance of Biobased Surfactants Prepared by the One-Pot Reductive Amination of l-Arabinose and d-Galacturonic Acid.

Herein, we report a method for the synthesis of biobased surfactants derived from sugar beet pulp (SBP) monosaccharides, l-Ara and d-GalA. The surfactants were prepared via one-pot reductive amination, allowing the introduction of different alkyl chain lengths and methyl modifications. Optimal reaction conditions were established to achieve high yields and easy purification. The synthesized surfactants including the tertiary amines exhibited desirable properties, including solubility, foamability, and reduction of surface tension. Notably, the anionic surfactants derived from d-GalA demonstrated better solubility and foam performance compared to those derived from l-Ara. In addition, these surfactants exhibited surface tension and critical micelle concentration (CMC) comparable to those of the commercial surfactant sodium lauryl ether sulfate (SLES). Furthermore, the biodegradable surfactant GalA1.8 displayed excellent emulsifying properties and low skin irritation potential. On the l-Ara surfactant with a short chain, Ara1.6 has potential as a hydrotrope. These findings suggest that biobased surfactants derived from SBP monosaccharides have promising applications in various industries, including pharmaceuticals, cosmetics, detergents, and chemicals.

Can wormlike micelle stiffness be estimated from zero‐shear viscosity? Experimental investigation with a model system and specific salt interactions

AbstractThe microstructure of wormlike micelles (WLM) directly affects the rheological properties of their solutions. Investigating the structure–property relationships of WLM has long been a popular topic for researchers who have developed theoretical and empirical models to describe their viscoelastic behavior. All these models rely on a collection of characteristic “length” parameters that are often difficult to estimate using relatively simple rheological tests. In particular, the micelle stiffness, as described by the persistence length, can be difficult to measure experimentally, while being very impactful on the bulk rheology of WLM solutions. Here, an array of inorganic salts (NaCl, LiCl, MgCl2, NaBr, NaI, and Na2SO4) have been used to induce wormlike micelle formation in an aqueous solution of the surfactant sodium lauryl ether sulfate. Ion dissociation/association with the surfactant head groups and the hydrogen bond network of the water alters the effective stiffness of the micelles, allowing for an estimation of the stiffness using three different methods: (1) small angle neutron scattering (SANS) measurements, (2) oscillatory rheological measurements, and (3) steady rheological measurements with a thermodynamic packing parameter model. Each of these methods are then compared and shown to be consistent with each other for the micelle solutions tested. The consistency of the results across all the measurements suggests that the approach used in this study, which estimates micelle parameters using steady shear rheology and a thermodynamic model, could provide a simpler and more accessible method for estimating micelle parameters in a wide range of surfactant systems.

Bioaugmentation With a Consortium of Bacterial Sodium Lauryl Ether Sulfate-Degraders for Remediation of Contaminated Soils.

The anionic surfactant sodium lauryl ether sulfate (SLES) is the main component of most commercial foaming agents (FAs) used in the excavation of highway and railway tunnels with Earth pressure balance-tunnel boring machines (EPB-TBMs). Several hundreds of millions of tons of spoil material, consisting of soil mixed with FAs, are produced worldwide, raising the issue of their handling and safe disposal. Reducing waste production and reusing by-products are the primary objectives of the “circular economy,” and in this context, the biodegradation of SLES becomes a key question in reclaiming excavated soils, especially at construction sites where SLES degradation on the spot is not possible because of lack of space for temporary spoil material storage. The aim of the present work was to apply a bacterial consortium (BC) of SLES degraders to spoil material excavated with an EPB-TBM and coming from a real construction site. For this purpose, the BC capability to accelerate SLES degradation was tested. Preliminary BC growth, degradation tests, and ecotoxicological evaluations were performed on a selected FA. Subsequently, a bioaugmentation experiment was conducted; and the microbial abundance, viability, and SLES concentrations in spoil material were evaluated over the experimental time (0.5, 3, 6, 24, 48, and 144 h). Moreover, the corresponding aqueous elutriates were extracted from all the soil samples and analyzed for SLES concentration and ecotoxicological evaluations with the bacterium Aliivibrio fischeri. The preliminary experiments showed the BC capability to grow under 14 different concentrations of the FA. The maximum BC growth rates and degradation efficiency (100%) were achieved with initial SLES concentrations of 125, 250, and 500 mg/L. The subsequent bioaugmentation of the spoil material with BC significantly (sixfold) improved the degradation time of SLES (DT50 1 day) compared with natural attenuation (DT50 6 days). In line with this result, neither SLES residues nor toxicity was recorded in the soil extracts showing the spoil material as a by-product promptly usable. The bioaugmentation with BC can be a very useful for cleaning spoil material produced in underground construction where its temporary storage (for SLES natural biodegradation) is not possible.

Phase separation of saturated micellar network and its potential applications for nanoemulsification

Phase separation of saturated micellar network, as a result of cross-linking of branched micelles, is established in mixed solutions of the anionic surfactant sodium laurylethersulfate (SLES) and the zwitterionic cocamidopropyl betaine (CAPB) in the presence of divalent counterions: Ca2+, Zn2+ and Mg2+. The saturated network appears in the form of droplets, which are heavier than water and sediment at the bottom of the vessel. In the case of Mg2+, the sedimented drops coalesce and form a separate multiconnected micellar phase – a supergiant surfactant micelle. For this phase, the rheological flow curves show Newtonian and shear-thinning regions. The appearance/disappearance of the Newtonian region marks the onset of formation of saturated network. The addition of small organic molecules (fragrances) to the multiconnected micellar phase leads to an almost spontaneous formation of oil-in-water nanoemulsion. The nanoemulsification capacity of the multiconnected micellar phase decreases with the rise of the volume of the oil molecule. A possible role of the network junctions in the nanoemulsification process can be anticipated. The properties of the multiconnected micellar phases could find applications in extraction and separation processes, in drug/active delivery, and for nanoemulsification at minimal energy input.

Isolation and Characterization in a Soil Conditioned With Foaming Agents of a Bacterial Consortium Able to Degrade Sodium Lauryl Ether Sulfate.

The anionic surfactant Sodium Lauryl Ether Sulfate (SLES) is the principal component of several commercial foaming products for soil conditioning in the tunneling industry. Huge amounts of spoil material are produced during the excavation process and the presence of SLES can affect its re-use as a by-product. Anionic surfactants can be a risk for ecosystems if occurring in the environment at toxic concentrations. SLES biodegradability is a key issue if the excavated soil is to be reused. The aim of this study was to identify bacteria able to degrade SLES, so that it could potentially be used in bioaugmentation techniques. Enrichment cultures were performed using bacterial populations from spoil material collected in a tunnel construction site as the inoculum. A bacterial consortium able to grow in a few hours with SLES concentrations from 125 mg/L to 2 g/L was selected and then identified by Next Generation Sequencing analysis. Most of bacteria identified belonged to Gamma-Proteobacteria (99%) and Pseudomonas (ca 90%) was the predominant genus. The bacterial consortium was able to degrade 94% of an initial SLES concentration of 250 mg/L in 9 h. A predictive functional analysis using the PICRUSt2 software showed the presence of esterase enzymes, responsible for SLES degradation. The bacterial consortium selected could be useful for its possible seeding (bioaugmentation) on spoil material from tunneling excavation.

Direct Measurements of kT-Scale Capsule-Substrate Interactions and Deposition Versus Surfactants and Polymer Additives.

We report a novel approach to directly measure the interactions and deposition behavior of functional capsule delivery systems on glass substrates versus the concentration of an anionic surfactant sodium lauryl ether sulfate (SLES) and a cationic acrylamide-acrylamidopropyltrimonium copolymer (AAC). Analyses of three-dimensional optical microscopy trajectories were used to quantify lateral diffusive dynamics, deposition lifetimes, and potentials of mean force for different solution conditions. In the absence of additives, negatively charged capsule surfaces yield electrostatic repulsion with the negatively charged substrate, which inhibits deposition. With an increasing SLES concentration below the critical micelle concentration (CMC), capsule-substrate electrostatic repulsion is mediated by the charged surfactant solution that decreases the Debye length. Above the SLES CMC, depletion attraction causes enhanced deposition until eventually depletion repulsion inhibits deposition at concentrations ∼10 wt %. Addition of an ACC causes deposition via capsule-substrate bridging at all concentrations; the weakest deposition occurs at intermediate AAC concentrations from a competition of steric repulsion and attraction via a few extended bridges. The novel measurements and models of capsule interactions and deposition on substrates in this work provide a basis to fundamentally understand and rationally design complex rinse-off cleansing formulations with optimal characteristics.

Passive, active, and interactive drag-reduction technique to reduce friction and enhance the mixing intensity in rotating disk apparatus

Rotating disks are applied in many industrial heat and mass transfer systems because of their high mixing performance. The presence of non-Newtonian viscous liquids in these systems limits the mixing performance, thereby affecting the required heat and mass transfer. In this study, passive, active, and interactive drag-reduction techniques are proposed to enhance the mixing and drag-reduction performance of rotating disks and are experimentally tested. An SV-grooved surface (triangular shaped) is engraved on a disk attached to a rotating disk apparatus to test the liquid resistance based on torque readings and the velocity profile using a miniature laser Doppler velocimeter (Mini-LDV, MicroPro). The polymer polyisobutylene and the surfactant sodium lauryl ether sulfate are chosen as the passive–active integrated drag-reduction components in an experiment using different additive concentrations and polymer–surfactant complexes in the same tests. The experimental results show that the selected passive design of the riblets can enhance flow by 8% and that this percentage increases when polymeric additives and polymer-surfactant complexes are introduced. The velocity profile results show that high-velocity zones are created above the rotating surface and that these zones contribute significantly to enhancing the mixing intensity in the drag-reduction system.

Control of surfactant solution rheology using medium-chain cosurfactants

The rheological properties of surfactant solutions play an important role in their applications. Here we study systematically how different cosurfactants affect the rheological properties of mixed solutions of the anionic surfactant sodium laurylether sulfate (SLES) and the zwitterionic cocoamidopropyl betaine (CAPB). Mixed SLES+CAPB solutions are used in various formulations due to their excellent foaming and cleaning properties. These solutions possess nearly Newtonian behavior and low viscosity. However, the addition of cosurfactants in low concentrations may significantly increase the viscosity of these solutions and even transform them into viscoelastic gels. Here we study systematically a wide range of ionic and nonionic cosurfactants with different head-groups, chain-lengths and structures of the hydrophobic tails (linear, branched, double bonded). We reveal an optimal chain-length of 8–10 carbon atoms of the cosurfactant molecules which ensures the highest viscoelasticity of the triple SLES+CAPB+cosurfactant solutions. Cationic cosurfactants and nonionic ones with small head-group (e.g. fatty alcohols and fatty acids) are most efficient in increasing the solution viscoelasticity. There is a hierarchy in the parameters of the cosurfactant molecules which govern this behavior − most important is the head-group charge, then the chain-length and, finally, the presence of branching and double bonds in the hydrophobic tails. The observed trends are explained with the effect of the cosurfactant molecules on the properties of the entangled wormlike micelles formed in these solutions.

Sodium lauryl ether sulfate (SLES) degradation by nitrate-reducing bacteria

The surfactant sodium lauryl ether sulfate (SLES) is widely used in the composition of detergents and frequently ends up in wastewater treatment plants (WWTPs). While aerobic SLES degradation is well studied, little is known about the fate of this compound in anoxic environments, such as denitrification tanks of WWTPs, nor about the bacteria involved in the anoxic biodegradation. Here, we used SLES as sole carbon and energy source, at concentrations ranging from 50 to 1000 mg L−1, to enrich and isolate nitrate-reducing bacteria from activated sludge of a WWTP with the anaerobic-anoxic-oxic (A2/O) concept. In the 50 mg L−1 enrichment, Comamonas (50%), Pseudomonas (24%), and Alicycliphilus (12%) were present at higher relative abundance, while Pseudomonas (53%) became dominant in the 1000 mg L−1 enrichment. Aeromonas hydrophila strain S7, Pseudomonas stutzeri strain S8, and Pseudomonas nitroreducens strain S11 were isolated from the enriched cultures. Under denitrifying conditions, strains S8 and S11 degraded 500 mg L−1 SLES in less than 1 day, while strain S7 required more than 6 days. Strains S8 and S11 also showed a remarkable resistance to SLES, being able to grow and reduce nitrate with SLES concentrations up to 40 g L−1. Strain S11 turned out to be the best anoxic SLES degrader, degrading up to 41% of 500 mg L−1. The comparison between SLES anoxic and oxic degradation by strain S11 revealed differences in SLES cleavage, degradation, and sulfate accumulation; both ester and ether cleavage were probably employed in SLES anoxic degradation by strain S11.

The Effect of Surfactant on Selectivity in the Extraction of Aromatic Hydrocarbons from the Lube Oil

An investigation was conducted in order to examine the effect of the addition of surfactant to the fraction of the light lubricating oil (spindle) during the solvent extraction process. The solvent power and selectivity can be further increased by using surfactant as an additive. This could facilitate the separation phase and increase the yield of the raffinate. In this study, we suggested the use of ethoxylated anionic surfactant (sodium lauryl ether sulfate). The aromatics in the lube oil were extracted at different temperatures (ranging from 333.15 to 343.15 K) with different concentrations of surfactant (ranging from 0.01 to 0.1 wt%). The extraction temperature and the amount of surfactant in furfural were systematically investigated to determine their optimum values. Compositions in monoaromatics, diaromatics, polyaromatics, and saturates were determined by using UV–Vis spectrophotometry. When surfactant was added, the solvent acquired the ability to preferentially extract polyaromatics instead of the monoaromatics. This directly affects the required oil quality. It was found that using 0.01 wt% of surfactant at 343.15 K yields the optimum extraction conditions.

Study of adsorptive behavior of sulfonated polyacrylamide onto carbonate rock particles to enhance oil recovery

The adsorption of sulfonated polyacrylamide (SPAM) as an enhanced oil recovery polymer onto carbonate rock particles was studied using UV-visible spectroscopy. The effect of the experimental parameters of polymer concentration, salinity and temperature was investigated. The results showed that polymer adsorption increased as the SPAM concentration increased, but decreased as temperature and water salinity increased. Adsorption of the polymer in the presence of the anionic surfactant sodium lauryl ether sulfate (SLES) was evaluated in electrolyte media and in pure water. The adsorption equilibrium data for SPAM in electrolyte media was better fitted to the Langmuir isotherm than the Freundlich model. The thermodynamic parameters indicated that adsorption is a spontaneous and exothermic physisorption process.

Aggregation behavior of sodium lauryl ether sulfate with a positively bicharged organic salt and effects of the mixture on fluorescent properties of conjugated polyelectrolytes.

The aggregation behavior of anionic single-chain surfactant sodium lauryl ether sulfate containing three ether groups (SLE3S) with positively bicharged organic salt 1,2-bis(2-benzylammoniumethoxy)ethane dichloride (BEO) has been investigated in aqueous solution, and the effects of the BEO/SLE3S aggregate transitions on the fluorescent properties of anionic conjugated polyelectrolyte MPS-PPV with a larger molecular weight and cationic conjugated oligoelectrolyte DAB have been evaluated. Without BEO, SLE3S does not affect the fluorescent properties of MPS-PPV and only affects the fluorescent properties of DAB at a higher SLE3S concentration. With the addition of BEO, SLE3S and BEO form gemini-like surfactant (SLE3S)2-BEO. When the BEO/SLE3S molar ratio is fixed at 0.25, with increasing the BEO/SLE3S concentration, the BEO/SLE3S mixture forms large, loosely arranged aggregates and then transforms to closely packed spherical aggregates and finally to long thread-like micelles. The photoluminescence (PL) intensity of MPS-PPV varies with the morphologies of the BEO/SLE3S aggregates, while the PL intensity of DAB is almost independent of the aggregate morphologies. The results demonstrate that gemini-like surfactants formed through intermolecular interactions can effectively adjust the fluorescent properties of conjugated polyelectrolytes.

Solubility limits and phase diagrams for fatty alcohols in anionic (SLES) and zwitterionic (CAPB) micellar surfactant solutions

By analysis of experimental data, a quantitative theoretical interpretation of the solubility limit of medium- and long-chain fatty alcohols in micellar solutions of water-soluble surfactants is presented. A general picture of the phase behavior of the investigated systems is given in the form of phase diagrams. The limited solubility of the fatty alcohols in the micelles of conventional surfactants is explained with the precipitation of their monomers in the bulk, rather than with micelle phase separation. The long chain fatty alcohols (with n=14, 16 and 18 carbon atoms) exhibit an ideal mixing in the micelles of the anionic surfactant sodium laurylethersulfate (SLES) and the zwitterionic surfactant cocamidopropyl betaine (CAPB) at temperatures of 25, 30, 35 and 40°C. Deviations from ideality are observed for the alcohols of shorter chain (n=10 and 12), which can be explained by a mismatch with the longer chains of the surfactant molecules. Using the determined thermodynamic parameters of the systems, their phase diagrams are constructed. Such a diagram consists of four domains, viz. mixed micelles; coexistent micelles and precipitate (dispersed crystallites or droplets); precipitate without micelles, and molecular solution. The four boundary lines intersect in a quadruple point, Q. For ionic surfactants (like SLES), a detailed theory for calculating the boundary lines of the phase diagrams is developed and verified against data for the positions of the kinks in surface tension isotherms. The theory takes into account the electrostatic interactions in the micellar solutions and the effect of counterion binding. The results can be useful for a quantitative interpretation and prediction of the phase behavior of mixed solutions of two (or more) surfactants, one of them being water soluble and forming micelles, whereas the other one has a limited water solubility, but readily forms mixed micelles with the former surfactant.

Foam-Assisted Delivery of Nanoscale Zero Valent Iron in Porous Media

AbstractFoam is potentially a promising vehicle to deliver nanoparticles for vadose-zone remediation because foam can overcome the intrinsic problems associated with solution-based delivery, such as preferential flow and contaminant mobilization and spreading. In this work, the feasibility of using foam to deliver nanoscale zero valent iron (nZVI) in unsaturated porous media was investigated. Foam generated using the surfactant sodium lauryl ether sulfate (SLES) showed excellent ability to carry nZVI. SLES and nZVI concentrations in the foaming solutions did not affect the percentages of nZVI concentrations in foam relative to nZVI concentrations in the solutions. When foams carrying nZVI were injected through the unsaturated columns, the fractions of nZVI exiting the column were much higher than those when nZVI was injected with liquid. The enhanced nZVI transport implies that foam delivery could significantly increase the radius of influence of injected nZVI. The type and concentrations of surfactants a...

Solubility limits and phase diagrams for fatty acids in anionic (SLES) and zwitterionic (CAPB) micellar surfactant solutions

The limiting solubility of fatty acids in micellar solutions of the anionic surfactant sodium laurylethersulfate (SLES) and the zwitterionic surfactant cocamidopropyl betaine (CAPB) is experimentally determined. Saturated straight-chain fatty acids with n=10, 12, 14, 16, and 18 carbon atoms were investigated at working temperatures of 25, 30, 35, and 40°C. The rise of the fatty acid molar fraction in the micelles is accompanied by an increase in the equilibrium concentration of acid monomers in the aqueous phase. Theoretically, the solubility limit is explained with the precipitation of fatty acid crystallites when the monomer concentration reaches the solubility limit of the acid in pure water. In agreement with theory, the experiment shows that the solubility limit is proportional to the surfactant concentration. For ideal mixtures, the plot of the log of solubility limit vs. the chainlength, n, must be a straight line, which is fulfilled for n=14, 16, and 18. For the fatty acids of shorter chains, n=10 and 12, a deviation from linearity is observed, which is interpreted as non-ideal mixing due to a mismatch between the chainlengths of the surfactant and acid. The data analysis yields the solubilization energy and the interaction parameter for the fatty acid molecules in surfactant micelles. By using the determined parameter values, phase diagrams of the investigated mixed solutions are constructed. The four inter-domain boundary lines intersect in a quadruple point, whose coordinates have been determined. The results can be applied for the interpretation and prediction of the solubility, and phase behavior of medium- and long-chain fatty acids and other amphiphiles that are solubilizable in micellar surfactant solutions, as well as for determining the critical micellization concentration (CMC) of the respective mixed solution.

Degradation of anionic surfactants by Citrobacter braakii

Anionic surfactants, as core components of detergent and cosmetic products formulations, contribute significantly to the pollution profile of sewage and wastewaters of all kinds. In Tunisia more than 100 000 m 3 per year of surfactant containing wastewater are released. Treatment by conventional processes such as activated sludge is problematic due to the low kinetics of degradation by unsuitable consortia and to foam production. Bioremediation involves the isolation of suitable microorganisms, adequate process development and in situ biodegradation. The objective of this work was to develop a high performance process for the treatment of anionic surfactant containing wastewater. Screening of bacteria degrading the anionic surfactant sodium lauryl ether sulfate (SLES) was carried out by a conventional enrichment-culture technique. A Citrobacter braakii strain degrading many anionic surfactants was isolated and tested in bioaugmentation for industrial wastewater treatment. It was used for the continuous degradation of highly concentrated SLES synthetic medium and cosmetic industry wastewater. By testing several dilution rates, it was concluded that C. braakii is able to degrade up to 0.065 g l −1 h −1. The hydraulic retention time (HRT) was nearly 20 h. This process was improved by coupling the bioreactor to a mineral microfiltration membrane. This allowed an increase in the SLES elimination rate from 0.065 to 0.15 g l −1 h −1 and to reduce the HRT from 20 to 5 h. Moreover, this integrated system generates microorganism and surfactant free wastewaters able to be rejected without public menace or reused in situ in the industrial process.

Determination of Surfactant Sodium Lauryl Ether Sulfate by Ion Pairing Chromatography with Suppressed Conductivity Detection

Abstract A method for the determination of the anionic Steol CS-330 surfactant is described. CS-330 is a complex mixture of oligomers due to the various sizes of fatty alcohols and the number of moles of the ethoxylation. The main component of CS-330 is sodium lauryl ether sulfate (SLES). Since a SLES molecule has a hydrophilic sulfate head and a hydrophobic alkyl ethoxyl tail, it is very difficult to separate these molecules with conventional reverse phase chromatography or ion exchange chromatography. This work uses ion pairing chromatography with suppressed conductivity detection. The separation of oligomers in CS-330 is achieved. SLES does not have UV-absorbing chromophores, therefore an optical detector is not very sensitive. Suppressed conductivity detection technique significantly increases sensitivity and a quantitation limit of 56.60 ppm is achieved.