Sodium Dodecyl Sulfate System Research Articles

Comparative solubilization of Gliclazide in solutions of two anionic micelles with asymmetrical hydrophobic chain length: An experimental and theoretical analysis

Gliclazide (GCL) is used widely for reducing hyperglycemia in diabetic patients. It has poor solubility which leads to low oral bioavailability because of significant first-pass metabolism. In this work, we have employed two anionic micellar solutions of different hydrophobic chain lengths to solubilize GCL. They are sodiumtetradecyl sulfate (STS) and sodiumdodecyl sulfate (SDS). Our results reveal that longer hydrophobic chain was better suited for solubilizing GCL. The drug-surfactant interactions were assessed through FT-IR, conductivity, UV-Spectrophotometry, dynamic light scattering and antioxidant study. The results were compared with computational studies. There was negative free energy of micellization and positive entropy of micellization GCL + STS and GCL + SDS systems predicting spontaneity of the processes as calculated from the conductivity experiments. From the UV spectral studies, using Benesi-Hildebrand (B-H) equation, the binding constants demonstrated higher value for GCL + STS (0.286 M−1) compared to GCL + SDS (0.0231 M−1). The antioxidant properties of the above two combinations show that STS (93.14 %) has higher radical scavenging activity (RSA %) compared to SDS (77.45 %). Protein binding studies too indicated higher binding constant for STS than SDS with the drug. The docking model also supported the above findings. The longer hydrophobic chain length facilitated the solubilization of GCL with improved properties. This study offers a novel drug formulation for widely used drug GCL.

Effect of Different Concentrations of NiMnGa Micro/Nanoparticles on the Kinetics of Natural Gas Hydration

To improve gas hydrate storage and transportation technology, ferromagnetic intermetallic compound NiMnGa particles with martensitic transformation endothermics were used to form micro/nanofluids with sodium dodecyl sulfate (SDS) to further strengthen the gas hydration process. In this work, the kinetic process of gas hydration in NiMnGa fluids with different concentrations (0, 0.1, 1, 2, and 3 wt.%) was investigated using a rotating magnetic field gas hydration separation experimental setup. The results show that the induction time of the 3 wt.% NiMnGa system was shortened by 98.3%, the gas consumption was increased by 50.5%, and the gas consumption rate was increased by 351.9% compared with the SDS system. Therefore, it is inferred from the mass transfer that NiMnGa micro/nanofluids can accelerate the formation of hydrates.

Effect of molar ratio and alkyl chain length on the aggregation behavior of imidazolium-based ionic liquid surfactants/SDS systems

In our previous publication (https://doi.org/10.1016/j.jcis.2019.04.023), the volumes and concentrations of syringe and sample cell in Isothermal titration calorimetry (ITC) limit the molar ratios and concentrations during the titration process. The molar ratios and concentrations of sodium dodecylsulfate (SDS) are almost higher than those of the ionic liquids (ILs) throughout the titration process. From the perspective of SDS molar ratios and concentrations, when the molar ratios and concentrations of the imidazolium-based ILs exceed those of SDS, the research remains unexplored. This aspect of the research has been consistently neglected, yet it is crucial for a fundamental understanding of self-assembly structure transitions. For these mixed systems, the phase behavior, zero-shear viscosity, and dynamic viscoelasticity of the system do not increase with the increasing carbon chain length of imidazolium ILs. The variation in carbon chain length exhibits an optimal value (1-octyl-3-methylimidazolium chloride ([OMIM]Cl)/SDS system), which may be related to the balance between the electrostatic attraction among headgroups and the hydrophobic interactions among hydrophobic chains. To enhance a deeper comprehension of the variations in macroscopic properties across the entire range of mole ratios, enthalpy changes and cryogenic Transmission Electron Microscopy (cryo-TEM) were employed to study the mixed systems. When 100.0 mM imidazolium-based ILs were titrated into 12.5 mM SDS solution, the titration curves consistently exhibited a plateau. During this plateau, SDS micelles undergo disassembly and reassemble into vesicle structures of different sizes. The formation of vesicles is a continuous process until the imidazolium ILs is completely consumed. We propose a straightforward and feasible method to determine the molecular ratios of surfactants responsible for constructing vesicle structures in different alkyl chain lengths systems by fitting the enthalpy changes at different stages. Through this approach, the molecular ratios of SDS and 1-Hexyl-3-methylimidazolium chloride ([HMIM]Cl), 1-Octyl-3-methylimidazolium chloride ([OMIM]Cl), and 1-Dodecyl-3-methylimidazolium chloride ([DMIM]Cl) in the vesicle structures are 1:1, 4:5 and 7:10, respectively.

Effect of anionic surfactants on the heavy metal ions removal by adsorption onto ion exchangers - batch and column studies

Adsorption of heavy metals by various sorbents has been widely studied by many scientists due to the processes of industrialization as well as the great concentration of these toxic and dangerous pollutants in the environment the elimination of which is significant important. The ion exchangers Lewatit MonoPlus SR7, Lewatit MonoPlus TP220, Purolite A830 and Lewatit AF5 were used as adsorbents to remove heavy metal ions (M(II)) such as zinc (Zn(II)), nickel (Ni(II)) and copper (Cu(II)) (especially Cu(II)) in the presence of anionic surfactants to examine the adsorption efficiency in such systems. The main objective of this paper were the kinetic, equilibrium, thermodynamic and column studies in the HCl–M(II)–anionic surfactant (AS) such as SDS (Sodium Dodecyl Sulfate), ABS (Dodecylbenzene Sulfonic Acid) or ABSNa50 (Sodium Dodecylbenzene Sulfonate) systems. The largest adsorption capacities were obtained in the HCl–M(II)–AS systems for Lewatit MonoPlus TP220 (Cu(II): 9.9–10 mg/g; Zn(II): 8.5–8.9 mg/g and Ni(II): 7.3–9.2 mg/g) compared to the other ion exchangers. Therefore, after the first selection, Lewatit MonoPlus TP220 and the systems containing Cu(II) were further examined. The isotherms models were applied in the experimental data analysis and show that the Langmuir (determination coefficient, R2 > 0.993) and Temkin (R2 = 0.948–0.965) isotherm models exhibit the best fitting. The results of the temperature-dependent adsorption of Cu(II) in the presence of SDS on Lewatit MonoPlus TP220 suggested that the adsorption was spontaneous, thermodynamically favourable, and exothermic in nature (the enthalpy, ∆H° = −7.19 kJ/mol (↓CMC) and −7.03 kJ/mol (↑CMC). The largest working ion exchange capacities of the anion exchange resin were obtained for the ABS surfactant (Cw = 30 g/L (↓CMC) and 12 g/L (↑CMC)). As follows from the current investigations Lewatit MonoPlus TP220 has a great potential for the removal of Cu(II) in the presence of ABS and SDS. For comparison, Cu(II) ions removal by the micellar enhanced ultrafiltration process was also presented and exhibits 54–73.88 % Cu(II) removal efficiency in the presence of SDS and ABS.

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.

Insights on CO2 Hydrate Formation and Dissociation Kinetics of Amino Acids in a Brine Solution

CO2 sequestration as hydrates has captured enormous research interest in recent years due to its high storage capacity. However, the slow hydrate formation kinetics poses a strong challenge in its applicability and urges the need for additives (kinetic promoters) to accelerate the hydrate formation kinetics. This study investigates the performance of amino acid solutions in brine (3.3 wt % NaCl) on CO2 hydrate formation and dissociation kinetics. The kinetics of hydrate formation and dissociation was evaluated at varying concentrations (0.2, 0.5, 0.8, and 1 wt %) of l-methionine, l-isoleucine, and l-threonine solutions in brine using a high-pressure hydrate reactor at 4 MPa, and formation temperature of 274.15 K, and a dissociation temperature of 277.15 K. CO2 hydrate formation and dissociation experiments were also conducted using sodium dodecyl sulfate (SDS), pure water, and brine systems as standards for comparison. The findings show that all the studied amino acid systems show hydrate inhibition as compared to the pure water system with 35–41% reduction in CO2 storage capacity. Further, l-methionine exhibited an optimum performance with a slight promotional effect at 0.2 wt % with the lowest induction time (35.6 min) and the highest CO2 uptake (42.08 mol/mmol) among the studied amino acid systems. However, comparing l-methionine with SDS shows less induction time for SDS (28.48 min), indicating kinetic promotion of SDS over l-methionine in the presence of brine. The dissociation kinetics findings reveal the lowest dissociation rate for l-methionine and a prolonged time of CO2 release compared to l-threonine and l-isoleucine, respectively. Nevertheless, all the considered amino acid systems exhibit more inhibition or stability for hydrate dissociation as compared to the pure water system. However, compared to SDS and brine systems, the amino acids l-methionine and l-isoleucine show a slight promotion effect, unlike l-threonine which exhibits strong kinetic inhibition. The results thus suggest that amino acid solutions in brine stabilize hydrate dissociation; however, the CO2 hydrate formation inhibition in brine is quite discouraging for CO2 storage purposes. Instead, applying amino acids in flow assurance could be an additional advantage due to the presence of brine in practical reservoir fluids during production.

Synergistic enhancement of coalbed methane hydration process by magnetic field and NiMnGa micro-nano fluid

Coalbed methane is an important renewable energy source. Gas hydration technology is a new method for enhancing the utilization of coalbed methane and reducing environmental pollution. Long induction periods, sluggish formation rates, low hydrate yields, and difficulty removing heat during hydrate formation are all issues with gas hydration technology. In this paper, 3 wt% NiMnGa (NMG) phase-change micro/nanoparticles and 0.05% sodium dodecyl sulphate (SDS) were compounded, and gas hydration experiments were conducted under various initial pressures and gas sample conditions to investigate. The findings revealed that NMG has efficient mass transfer properties as well as phase-change heat absorption properties, which significantly improved the kinetic process of the gas hydrate by mass and heat transfer, shortened the induction time, increased gas consumption, and increased the gas consumption rate during the rapid hydrate growth period. When the initial pressure was 6.2 MPa, the induction time was reduced by 89.26%, 92.48%, and 95.64%, and the maximum gas consumption rate was increased by 238.18%, 175.55%, and 113.60%, respectively, when using different concentrations of methane in the NMG-SDS system compared to the pure SDS system. The NMG used in this paper showed potential for future use in mixed gas hydration technology.

Electrochemically tracking interactions between molecular ions of sodium dodecyl sulphate and the selected amino acid at the electrode-electrolyte interface

Surfactant assisted electrode–electrolyte (E-E) interface is a fascinating research topic that has been employed in different fields such as biosensing, energy devices, surface technology, etc. This work explores the electrochemical properties of sodium dodecyl sulphate (SDS) in the presence of essential amino acid (AA) i.e., l-Threonine (THR), dl-Methionine (MET), and l-Phenylalanine (PHE) at the E-E interface through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). For the electrochemical study of SDS at its premicellar and post micellar concentration in presence of AA ions, the three-electrode configuration consisting of glassy carbon (GC) as the working electrode, Ag/AgCl as reference electrode, and Pt wire as the counter electrode, have been used. Briton Robinson buffer (pH, 2) was utilized as the supporting electrolyte. The effect of AA ions on faradic properties of electroactive ions in the SDS system was studied by CV measurement. The scan rate effect was used to calculate the kinetic parameters such as maximum surface adsorbed concentration (Г, mol/cm2), diffusion coefficient (D, cm2/s), and capacitance of electrode surface (C, F/cm2). EIS measurements were applied to study the capacitive and resistive properties of the electric double layer (EDL) that developed at the E-E interface. The double-layer capacitance (Cdl) of EDL was extracted from the equivalent circuit diagram. The results from electrochemical measurements suggested that the electrochemical properties of SDS such as the faradaic process of electroactive ions and their kinetics through the SDS channel and charge storage performance of electrified surface were strongly affected by AA ions at the E-E interface through electrostatic interactions between oppositely charged ions. This work contributed to the understanding of the electrochemical interaction of biomolecular ions at the surfactant-assisted E-E interface. It will diversify the application of surface-active agents in biology and biotechnology.

Effects of silica gel nanopores and surfactants on CO2 hydrate formation kinetics—An experimental and modeling study

The carbon dioxide (CO2) hydrate formation kinetics in silica gel (SG) nanopores with the addition of surfactants are studied both experimentally and numerically. SGs with pore sizes of 50 and 100 nm are used as frameworks for hydrate formation in pores. Sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium chloride (DTAC) are used as kinetics promoters which can greatly enhance gas–water mass transfer. An advanced shrinking core model considering CO2 solubility, pore size, surfactants, and capillary effect is established. The results reveal that the reaction rate constant is increased in large pores or in the presence of surfactants, saving up to 49.3 % time to achieve the same amount of gas uptake in 100-nm SG with 500-ppm SDS. The effective diffusion coefficient controlled by a reduction factor drops dramatically due to the enlargement of the reduction factor in small pores and more surfactants, thus hindering the gas diffusion through the formed hydrate shell. The initial water consumed by capillary effect is more prominent in smaller pores and with the addition of surfactants. The initial proportion of water consumed by capillary effect to the total water consumption is only 1%–26.6% without surfactants, but can be up to 74.9% in 50-nm SGs with 500-ppm SDS. This proportion is overall higher in SDS systems than that in studied DTAC systems, but it is not obviously affected by surfactant concentrations. The higher proportion of water consumed by capillaries is speculated to be due to the more capillary tubes with larger radii formed initially in the presence of surfactants. The modeling strategies in this work can be applied to hydrate formation mechanisms in other porous materials.

PH-sensitive particles of polymer-surfactant complexes based on a copolymer of N,N′-diallyl-N,N′-dimethylammonium chloride with maleic acid and sodium dodecyl sulfate

The complex formation of copolymer of DADMAC-MA (N,N′-diallyl-N,N′-dimethylammonium chloride with maleic acid) and SDS (sodium dodecyl sulfate) were studied. Complexes self-assemble into dispersion of particles of polymer-surfactant complexes (PSC) in aqueous solutions, with a change in the concentration of NaCl and the amount of neutralized carboxyl groups of DADMAC-MA macromolecules by alkali. The DADMAC-MA/SDS complexes were characterized by spectroscopy (SEM, NMR, FT-IR, and UV), thermal analysis (TGA and DSC), and laser light scattering. The average particle sizes of PSC dispersions, depending on the composition of the reaction mixture and the neutralization degree of the DADMAC-MA carboxyl groups (f), vary in the range from 170 to 600 nm. The values of the critical concentration of SDS aggregation in the presence of DADMAC-MA are determined at different f. The possibility of influencing the phase transitions of the DADMAC-MA / SDS system by changing the ionic strength of the solution and the neutralization degree of DADMAC-MA carboxyl groups is shown. The ability of PSC particles to solubilize molecules of substances poorly soluble in water has been evaluated.

Coarse-Grained Model Incorporating Short- and Long-Range Effective Potentials for the Fast Simulation of Micelle Formation in Solutions of Ionic Surfactants.

A coarse-grained model comprising short- and long-range effective potentials, parametrized with the iterative Boltzmann inversion (IBI) method, is presented for capturing micelle formation in aqueous solutions of ionic surfactants using as a model system sodium dodecyl sulfate (SDS). In the coarse-grained (CG) model, each SDS molecule is represented as a sequence of four beads while each water molecule is modeled as a single bead. The proposed CG scheme involves ten potential energy functions: four of them describe bonded interactions and control the distribution functions of intramolecular degrees of freedom (bond lengths, valence angles, and dihedrals) along an SDS molecule while the other six account for intermolecular interactions between pairs of SDS and water beads and control the radial distribution functions. The nonbonded effective potentials between coarse-grained SDS molecules extend up to about 12 nm and capture structural and morphological features of the micellar solution both at short and long distances. The long-range component of these potentials, in particular, captures correlations between surfactant molecules belonging to different micelles and is essential to describe ordering associated with micelle formation. A new strategy is introduced for determining the effective potentials through IBI by using information (target distribution functions) extracted from independent atomistic simulations of a micellar reference system (a salt-free SDS solution at total surfactant concentration cT equal to 103 mM, temperature T equal to 300 K, and pressure P equal to 1 atm) obtained through a multiscale approach described in an earlier study. It employs several optimization steps for bonded and nonbonded interactions and a gradual parametrization of the short- and long-range components of the latter, followed by reparametrization of the bonded ones. The proposed CG model can reproduce remarkably accurately the microstructure and morphology of the reference system within only a few hours of computational time. It is therefore very promising for future studies of structural and morphological behavior of various liquid surfactant formulations.

Pluronic based neutral-ionic binary micellar surfactant systems for solubilizing the cationic methylene blue dye

The interaction of cationic methylene blue (MB) dye with binary micellar systems of non-ionic Pluronic®L-81 containing anionic sodium dodecyl sulfate (SDS) or cationic cetyl trimethyl ammonium bromide (CTAB) surfactants were probed through conductivity, uv-visible, FTIR, DLS, and zeta potential measurements with an objective to identify better solubilizing system at room temperature. The CMC of both SDS and CTAB was lowered in MB+L-81+SDS or CTAB systems. The absorption spectrum of MB showed a slight blue-shift with enhanced intensity upon increasing the concentration of anionic SDS and cationic CTAB, reflecting the strong electrostatic interaction and formation of micelles due to the solubilization of MB by L-81+SDS/CTAB systems. The higher negative value of ΔGm for L-81+SDS (-24.18 kJ/mol) than L-81+CTAB, (-17.07 kJ/mol) indicated better stability of MB in SDS system than CTAB. This could be attributed to the electrostatic attraction between dissimilarly charged MB (cationic) and SDS (anionic) in the ternary (MB+L-81+SDS) system and repulsive steric interaction between positively charged MB and CTAB. This was confirmed from micellar size analysis using dynamic light scattering (DLS) measurements and binding constant values. The estimated CMC values were comparable with the literature data. Hence, based on these results we propose that L-81+SDS binary system can be applied as a potential medium for removal of MB from the industrial effluents.

Effects of Composite Accelerators on the Formation of Carbon Dioxide Hydrates.

To improve the rate of formation of carbon dioxide hydrates, tetra-n-butylammonium bromide (TBAB) was compounded with different concentrations of sodium dodecyl sulfate (SDS) and nanographite, and the effects of these mixtures on carbon dioxide hydrate formation were studied. The addition of TBAB alone, as well as mixtures of TBAB and SDS or nanographite, shortened the induced nucleation time, and the induction times of the TBAB–2.5 g/L nanographite and TBAB–0.24 g/L SDS systems were the shortest and longest, respectively. Further, on mixing TBAB and SDS, the induced nucleation time first increased and then decreased with the increase in the SDS concentration. When TBAB and nanographite were mixed together, the induced nucleation time first decreased, then increased, and again decreased with the increase in the nanographite concentration. In addition, the hydrate formation rate and conversion were highest for the TBAB–0.48 g/L SDS system and lowest for the TBAB–0.06 g/L SDS system; in the first 35 min, from the end of gas charging, the TBAB–10 g/L nanographite and TBAB–5 g/L nanographite systems yielded the highest and lowest hydrate formation rates and conversions, respectively. For the composite systems, obvious effects were observed in the initial stages of reaction, but the effects varied over the course of the reaction. Overall, the use of different accelerators resulted in little differences in the total production, conversion, and formation rate of carbon dioxide hydrates over the course of the reaction.

Investigating the effects of MWCNT-HB on gas storage performance of CO2 hydrate

The technology of capturing CO2 using hydrate has attracted wide attention. In this study, the effects of two carbon nanomaterials, original multiwalled carbon nanotube (MWCNT) and modified herringbone carbon nanotube (MWCNT-HB), on the gas storage performance of CO2 hydrate were investigated under static conditions. Compared with the MWCNT system, the MWCNT-HB system showed a stronger ability to improve gas storage performance. Secondary formation of hydrate in the MWCNT-HB system was observed, and the final gas storage capacity could be increased by 119.2% compared to the pure water system. Due to the long stationary period between the two hydrate formation processes, MWCNT-HB was used in combination with tetrahydrofuran (THF) and sodium dodecyl sulfate (SDS) respectively. It was found that the MWCNT-HB/THF system inhibited the hydrate formation owing to a film formed on the suspension surface. In the MWCNT-HB/0.2% SDS system, the coupling effect of the two materials further enhanced the heat and mass transfer. The gas storage rate could reach 1.25 m3·m−3·min−1, the gas storage capacity also increased to about 85 m3·m−3, and the induction time was only 5.1 min. The compound system not only enhanced the gas storage performance of CO2 hydrate but also effectively improved the phase equilibrium conditions. To further investigate the promotion mechanism, the thermal conductivity of the experimental materials, the surface tension of the solution, and the exothermic process of hydrate formation were measured and analyzed.

Microencapsulation of camphor using trimethylsilylcellulose

Microencapsulation of camphor by trimethylsilylcellulose was performed using oil-in-water emulsion method. Trimethylsilylcellulose (TMSC) with the DS value of 2.41 (CHN analysis) was synthesized by dissolving commercial cellulose in N, N-dimethylacetamide/LiCl followed by reacting with hexamethyldisilazane. Sodium dodecyl sulfate (SDS) in acidic aqueous solution and tetramethylammonium chloride (TMACl) in water were attempted as emulsifiers. The oil phase composed of TMSC and camphor in ethyl acetate was dispersed in emulsifier solution. The mass ratio of TMSC to camphor and emulsifier concentration were optimized to produce high quality microcapsules. Using the mass ratio of 3:7 and 1% (w/v) SDS solution gave well separated microcapsules of TMSC_C_SDS (1). The diameter size in the micron range (10–110 mm) and high camphor content (∼21.07%) were obtained from this sample. The larger size of the capsules obtained from TMACl system indicated the coalescence of the oil droplets. The hydrolysis of the external surface of the microcapsules was observed in the SDS system. However, this caused a minor effect on the cellulose stability in TMSC_C_SDS (1). The freshly prepared microcapsules of TMSC_C_SDS (1) showed the fast release of camphor during first 2 h and reached the equilibrium after 7 h.

Exploring the effects of selected essential amino acids on the self-association of sodium dodecyl sulphate at different temperatures

Sodium dodecyl sulphate (SDS) has well established biological applications in the determination of molecular weights and structure determination of proteins, peptides etc. Due to these reasons, the study of SDS interactions with essential amino acids (AAs) can be valuable as they can diversify the use of SDS in applications of importance in biology and drug delivery designs etc. The aggregation process of SDS and its detailed physiochemical properties in aqueous system, in the presence and absence of three essential amino acids L-Threonine (THR), DL- Methionine (MET) and L-Phenylalanine (PHE), is studied in a temperature range of 293 K-323 K using conductivities, surface tension (γ), particle size and zetapotential measurements using dynamic light scattering (DLS) technique. From conductivity measurements, critical micelle concentration (CMC), counterion binding (β) and thermodynamic parameters such as standard free energy change of micellization (ΔGmo), standard enthalpy change of micellization (ΔHmo), standard entropy change of micellization (ΔSmo) etc., are calculated. The surface properties and interfacial parameters of SDS systems are studied using surface tensiometery. Results established that the presence of amino acids (AAs) reduced the CMC of SDS. The electrostatic interaction of AAs with charged micellar surface were also observed. The micellization process of SDS was found thermodynamically feasible in the aqueous amino acid (AAA) system. From the surface tension data, interfacial parameters such as Гmax, Amin,pC20 , and surface effectiveness of SDS in aqueous and AAA system have been calculated and compared. It was revealed that surface adsorption and rearrangement of SDS molecular ion at their micellar concentration at air/liquid interface are significantly affected by AA addition. Hydrodynamic diameter (Dh) and zetapotential (ζ) of aqueous SDS solution helped to check the effect of amino acid additives on the colloidal size and stability of SDS aggregates. The results from different techniques were consistent to establish the feasibility of SDS micellization process in aqueous as well as aqueous AA solution.

Impact of ethanol and NaCl on the acid yellow dye mediated self-aggregation of sodium dodecyl sulfate: A combined investigation by conductivity and molecular dynamics simulation

Herein, we report the micellization behavior of the mixture of sodium dodecyl sulfate (SDS), and acid yellow (AY) dye in water, water + ethanol, and water + NaCl media. The degree of interaction between SDS and AY has been assessed quantitatively from the estimated values of critical micelle concentration (cmc). Three cmc values were observed for the AY + SDS systems at each temperature and solvents utilized, which exhibit a reversed U-shaped variation with respect to the change of temperature in aqueous/NaCl solution while increased monotonically in ethanolic medium almost in all cases. The extent of micellization was found to be disfavored in presence of AY dye. The micellization was also found to be disfavored up to 15% ethanol and favored in the addition of electrolyte species. The values of counterion binding were found to be temperature dependent. The Gibbs free energy (ΔGmo), which was found negative, reveal a spontaneous micellization of AY + SDS system. The other thermodynamic parameters, like enthalpy (ΔHmo) and entropy (ΔSmo) of micellization along with different transfer energies, were also assessed to have an insight on the mode of interaction of surfactant and dye assemblies. The molecular level interaction between SDS and AY has been unveiled by Molecular Dynamics (MD) simulation and exhibits good agreement with experimental results.

Renewable biosurfactants for energy-efficient storage of methane: An experimental and computational investigation

The continuously increasing demand for natural gas as an available and clean energy source indicates an inevitable transition to develop more promising technologies such as solidified natural gas (SNG) storage. Herein, we present a comprehensive experimental and computational study of the utilization of sunflower oil as a renewable biomass source to design highly efficient promoters based on the properties of sodium dodecyl sulfate (SDS) for methane hydrate formation. The effect of sunflower oil-based promoters (SFOPs) on methane hydrate kinetics was investigated theoretically via molecular dynamics (MD) simulation and experimentally under both dynamic (stirred reactor) and static (in the presence of porous media) conditions. SFOP1 considerably reduced induction time and overall time of the hydrate formation process compared to SDS under both conditions. In addition, SFOP1 significantly enhanced the kinetic constant of hydrate formation by 13.5 times, 3.7 times, and 2.5 times compared to pure water, SFOP2, and SDS systems, respectively, (in dynamic conditions). Moreover, both SFOPs improved the number of moles of gas consumed up to 450 mM in dynamic and 200 mM in static conditions compared to the pure water test. In contrast to the SDS solution, no foam formation was observed in the solution containing SFOPs. The MD results revealed that the SFOPs increased the transfer of methane molecules to the growing hydrate surface, which lead to enhance the kinetics of methane hydrate formation. Besides, more hydrate was formed by the addition of SFOP1 because of the improvement in the hydrogen bonds between water-water molecules in comparison with SFOP2. These findings clearly confirm that sunflower oil can be used for the development of green and more efficient promoters than SDS for methane hydrate formation without foam generation during the process.

Promoting methane hydrate formation with expanded graphite additives: Application to solidified natural gas storage

Solidified natural gas storage (SNG) using hydrate can provide environmentally friendly, highly compact and non explosive mode of NG storage at mild storage conditions. The efficient and rapid formation of natural gas hydrate is of great significance to the industrial application of SNG. In this work, in order to improve the gas storage capacity and absorption rate of CH4 hydrate, experiments were carried by adding expanded graphite (EG) with sodium dodecyl sulfate (SDS) with a pressure range of 5.0–8.0 MPa and a temperature of 273.2 K. The results indicate that EG can not only promote the formation of hydrate by promoting the nucleation of hydrate, but also accelerated the growth of hydrate by enhancing hydration heat transfer. EG system (0.05 wt%, 0.08 wt%, and 0.10 wt%) enabled faster hydrate formation than a liquid water system, with a content of 0.08 wt% optimal for the enhancement of hydrate formation. In the combination of EG (0.08 wt%) and SDS solution, EG + 0.03 wt% SDS system can improve the kinetics of hydrate formation to the greatest extent; the maximum gas storage capacity reached 190.4 STP/g H2O, and the maximum gas storage speed reached 20.84 cm3·g−1·min−1 at 273.2 K and 6 MPa. Compared with the SDS system, the maximum methane uptake and rates of EG + 0.03 wt% SDS system increased by 11.90% ~ 26.18% and 15.09% ~ 51.67% under different pressures respectively. At relatively low pressure, the hydrate can achieve a saturation of ~90% in EG + 0.03 wt% SDS system. On the other hand, compared with other carbon materials such as graphite and carbon nanotubes, the gas storage capacity and average gas storage rate of EG system were 1.12–1.37 times and 1.67–30.17 times higher, respectively, under similar temperature and pressure conditions. Therefore, a collaborative mode of enhancing gas concentration, nucleation site and heat transfer efficiency at the gas–liquid interface of hydrate reaction with only one material (EG) was proposed to promote the formation of hydrate. Further study on the promotion mechanism of EG and amplification experiments are expected to provide an effective way for the commercial application of SNG process in future work.

Microemulsions for luminescent solar concentrator application

Luminescent Solar Concentrators (LSC) are devices designed to concentrate solar radiation into photovoltaic (PV) cells. Compared to the extensively studied solid ones, Liquid LSCs offer the advantage of easy replacement of the photoactive component but the main drawback, in perspective of large-scale applications, of the presence of solvents. We propose aqueous photoactive microemulsions as original active materials to overcome this limit.Both photophysics and microstructure of samples in the microemulsion area of the pseudo-ternary system Sodium Dodecyl Sulphate (SDS)/1-butanol/water/DTB (4,7-Dithien-2-yl-2,1,3-benzothiadiazole) in toluene has been investigated. We detected a matrix structuring consistent with the dye-free microemulsions for scattering, conductivity, viscosity. The fluorophore does not alter the well-known self-assembling properties and thermodynamic stability.The impact of formulation on photoactivity, disclosed by fluorescence quenching, involves dye localization. The decrease in electrical efficiency when water content in microemulsions increases is lower than expected based on the reduction in the refractive index. The device performance results from the balance of many parameters. Hence the opportunity to produce more environmentally friendly liquid LSC’s.Finally, the relevance of the key factors contributing to whole efficiency is addressed, within the limits of the small size device used in this study. A substantial prevalence of the photoluminescence quantum yield is observed, while the photon transport efficiency parameter results to be the least impacting parameter.The present study has given us the means to effectively control the formulation of microemulsion for LSC, identifying the parameters and the analytical techniques that are the most effective in their design phase.