Mixtures Of Sodium Dodecyl Sulfate Research Articles

Surfactant foam injection for remediation of diesel-contaminated soil: A comprehensive study on the role of co-surfactant in foaming formulation enhancement

Aqueous foam injection is a promising technique for in-situ remediation of soil and aquifers contaminated by petroleum products. However, the application efficiency is strongly hindered by foam's instability upon contact with hydrocarbons. Addressing this, we propose a new binary surfactant mixture of Sodium Dodecyl Sulfate (SDS) and Cocamidopropyl Hydroxysultaine (CAHS). This study investigates CAHS's role as a co-surfactant in enhancing foam stability against antifoaming diesel oil under static and dynamic conditions. Using a dynamic foam analyzer (DFA-100), we assessed static foam's stability by monitoring decay profiles and bubble growth over time. The results revealed that the highest stability can be reached at a CAHS to SDS ratio of 50:50, increasing the half-life of the foam by 7.7 times. Remarkably, our analyses at bulk and bubble scales also elucidated the mechanisms behind the enhanced foam stability of the proposed binary surfactant mixture in the absence and presence of diesel. Additionally, in a 1D sand column, the SDS-CAHS mixture demonstrated more than twofold improvement of the Resistance Factor, attributed to the better survival of the lamellae due to the reduced rate of their destruction. This formulation also yielded a recovery improvement of >10 % compared to SDS foam. The significant improvements in stability and performance of the SDS-CAHS (50:50) mixture were credited to a robust pseudo-emulsion film formation, creating a higher oil entry barrier. This reinforcement and the surfactant molecules' synergistic interactions at the gas-liquid-oil interface significantly contributed to the overall effectiveness.

Preparation of biodegradable polymer nanoparticles stabilized with the poly (vinyl alcohol)-sodium dodecyl sulfate mixture: Effect of the lactide/glycolide molar ratio

Preparation of biodegradable polymer nanoparticles stabilized with the poly (vinyl alcohol)-sodium dodecyl sulfate mixture: Effect of the lactide/glycolide molar ratio

Study on the stability of high solid content polyether‐ether‐ketone aqueous suspension

AbstractCarbon fiber (CF) reinforced polyether‐ether‐ketone (PEEK) composite is found extensive application in various industries. Efforts have been made to enhance the interfacial binding between the resin and fibers. Herein, we report a green CF surface modification suspension coating method that could resist high process temperature by optimizing the stability of the aqueous suspension, which contains PEEK resin particles and a mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol monostearate (stPEG). The optimized suspension (PEEK: SDS mass ratio= 5:1) that can meet around 500°C process requirement was then used to improve the physical interfacial binding between CF and PEEK. Based on the suspension colloidal stability, the process was optimized by tensile tests of the CF/PEEK monofilaments. The results show that the colloidal stability of the PEEK aqueous suspension with a total solid content of 20 wt.% containing stPEG‐SDS (stPEG: SDS mass ratio= 1:2) surfactant blend (PEEK: stPEG‐SDS mass ratio= 5:1) reached the optimum at a stirring rate of 750 rpm. The maximum tensile strength of the CF/PEEK monofilaments reached ~4.968 GPa at a coating diameter of 8.54 μm. This PEEK aqueous suspension provides a non‐toxic, environmentally friendly and high temperature resistant aqueous material to produce high‐performance fiber reinforced PEEK composites.

High Interfacial Viscoelasticity of Aqueous Mixed Dodecyltrimethylammonium Bromide-Sodium Dodecyl Sulfate Surfactants Forming Inclusion Complexes with α-Cyclodextrin.

Mixtures of anionic-cationic surfactants have shown high synergistic effects in the bulk solution and at the liquid/air interface. These studies have been limited to a reduced concentration range, where there is no formation of aggregates or precipitates. The addition of host molecules, such as cyclodextrins, to these systems reduces the effects of precipitation by forming inclusion complexes and also modifies the values of other surfactant properties, like the Krafft temperature and the critical aggregation concentration (CAC). We studied the interfacial synergistic effects promoted by electrostatic interactions, using the Rosen model to calculate an interaction parameter for mixtures of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) in the presence of α-cyclodextrin (αCD), in aqueous solutions. We measured the CAC of SDS-DTAB-αCD mixtures using a pendant drop tensiometer, with the αCD concentration fixed at 10 mM and at 283.15 K. We performed rheological measurements on the mixtures where the surfactant total concentration is fixed below the measured CAC, varying the αCD concentration and temperature. We found that the dilatational modulus shows a clear correlation with the interaction parameter. It appears that the attractive interactions within the film are those due to the inclusion complexes formed by two αCD and one surfactant molecule, which according to the previous studies, is the dominant species in both the bulk and liquid/air interface. The synergistic effect observed here for SDS-DTAB surfactant mixtures with αCD can be applied to systems and processes (drop emission, drug delivery methods, stabilization of viral capsids and bacterial membranes, and emulsification) where interfacial processes require specific viscoelastic properties.

Spotlight on reversible emulsification and demulsification of tetradecane-water mixtures using CO2/N2 switchable surfactants: Molecular dynamics (MD) simulation

CO2/N2 switchable surfactants have recently attracted significant attention in enhanced oil recovery. Their environmental and economic benefits are the main driving forces for their application in the oil and gas industry. This study evaluated mixtures of sodium dodecyl sulfate (SDS), C18 naphthalene sulfonate (C18PS), and CO2-switchable acetamidine surfactant N′-dodecyl-N, N-dimethylacetamidine (C12DMAA) in water/dodecane systems by using molecular dynamics (MD) simulation. The effects of the molecular structure of anionic surfactant and surfactant concentration on switchable emulsification and demulsification in an oil/water/SDS or C18PS/C12DMAA system triggered by CO2/N2 injection were investigated. The molecule mobility, hydration behavior, density field analysis, diffusion coefficient, radial distribution functions (RDFs), and the density profiles of various systems were thoroughly examined. Based on MD simulation outputs, increasing surfactant concentration can intensify a demulsification process and create a clear phase separation between water and tetradecane. On the other hand, during an emulsification process, adding more surfactant monomers improved a hydration layer around oil droplets and increased hydrogen bonds; however, the contribution of hydrogen bonds between water and N′-dodecyl-N, N-dimethylacetamidinium (C12DMAAH+) compared to SDS and C18PS is limited. MD simulations proved the switchability of SDS/C12DMAA and C18PS/C12DMAA for emulsification and demulsification processes. The results of the current study will be beneficial for developing and optimizing the switchable surfactant structures for further use in the oil and gas industry through surfactant injection.

Characterization and stabilization of iron ore suspension and influence of the mixture of natural additive Sapindus mukorossi and SDS on the slurryability

The traditional way of transporting iron ore from mine to end-use plants often causes the industry significant economic hardship and degradation of the ecological system. Hydrotransportation of slurry through a pipeline is a remarkably viable strategy for effectively transporting iron ore in terms of economics, dependability, and safety, with minimal environmental impact. In the present investigation, a blend of bimodal samples is prepared by mixing medium and coarse particles of Indian iron ore of size 38–75 (I-2) and 75–106 (I-3) µm, respectively, with finer particles of size <38 µm (I-1) in 10–40% (by weight) proportion. Rheological characterization of the blend samples is done to finalize the optimum particle size. To enhance the flowability and stability of the concentrated iron ore samples, they are amalgamated with a mixture of plant-based nonionic saponin extracted from Sapindus mukorossi (Ritha) and the anionic sodium dodecyl sulfate (SDS) surfactants. The correct proportion of SDS in saponin is obtained through a thorough analysis of critical micellar concentration, zeta potential, and rheological parameters. Finally, the stability and slurryability of iron ore suspension with a Saponin–SDS mixture are established through rheological properties, dispersant concentration, and stabilization mechanisms. It is found that the optimum proportion of a mixture of saponin–SDS significantly improved the slurryability and stability of iron ore suspension and the maximum iron ore loading was enhanced by up to 81% by weight. The head loss and specific energy consumption analysis successfully evidence the significance of the surfactants in transporting the slurry through pipelines.

Observation of Strong Synergy in the Interfacial Water Response of Binary Ionic and Nonionic Surfactant Mixtures.

Interfacial vibrational footprints of the binary mixture of sodium dodecyl sulfate (SDS) and hexaethylene glycol monododecyl ether (C12E6) were probed using heterodyne detected vibrational sum frequency generation (HDVSFG). Our results show that in the presence of C12E6 at CMC (70 μM) the effect of SDS on the orientation of interfacial water molecules is enhanced 10 times compared to just pure surfactants. The experimental results contest the traditional Langmuir adsorption model predictions. This is also evidenced by our molecular dynamics simulations that show a remarkable restructuring and enhanced orientation of the interfacial water molecules upon DS- adsorption to the C12E6 surface. The simulations show that the adsorption free energy of DS- ions to a water surface covered with C12E6 is an enthalpy-driven process and more attractive by ∼10 kBT compared to the adsorption energy of DS- to the surface of pure water.

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing Trans / Cis Isomers

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing <i>Trans</i> / <i>Cis</i> Isomers

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.

Foam injection for enhanced recovery of diesel fuel in soils: Sand column tests monitored by CT scan imagery

The use of surfactant foam for the remediation of diesel fuel, a Light Non-Aqueous Phase Liquid (LNAPL), was investigated in sand column experiments using X-ray Computed Tomography (CT). A preliminary series of tests were carried out on six surfactant candidates in order to measure their physical properties, including critical micelle concentrations and interfacial tensions (IFT) with the LNAPL. Batch tests for foam stability were carried out with and without added LNAPL, in order to measure the half-life of foam columns produced with each surfactant candidate. Foam flow-rate co-injection tests were carried out for each surfactant candidate in 405 cm3 sand columns contaminated with LNAPL at residual saturation. These tests revealed that a 1:1 mixture of sodium dodecyl sulfate and cocamidopropyl betaine, injected at a total volumetric flow-rate (Qfoam) of 45 mL/min, resulted in successful generation and propagation of foam within the contaminated porous medium. Finally, two sand column tests, carried out respectively under high- and low-pressure conditions, were imaged with a CT-scanner in order to compare and contrast foam morphology evolution as well as the LNAPL desaturation dynamics involved in both scenarios. The saturation profiles extracted from CT images provided valuable new insights.

Monitoring the Cd2+ release from Cd-containing quantum dots in simulated body fluids by size exclusion chromatography coupled with ICP-MS.

Quantification of Cd2+ release from Cd-containing quantum dots (QDs) is of fundamental importance to elucidate its toxicity to organisms, but remains a great challenge due to the lack of appropriate analytical method. Herein, a facile method based on size exclusion chromatography (SEC) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for separating and quantifying the QDs and counterpart ions. By using the mixture of sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid tetrasodium salt (EDTA) as the mobile phase, the defect of QD and ion adsorption onto the SEC column was overcome, thus realizing the accurate quantification of ionic species. Besides, the concentration of QDs was achieved through subtracting the ion concentration from the total concentration. Selecting CdSe@ZnS as the typical QDs, the Cd2+ release process in four typical simulated body fluids, namely, simulated gastric fluid, simulated sweat, Gamble's solution, and artificial lysosomal fluid, was monitored using the developed SEC-ICP-MS method. The media pH is identified as the decisive factor which controls the dissolution of ZnS shells and also the Cd2+ release kinetics and final concentration. Our results suggest that the oral pathway for QD uptake poses the biggest risk to human health.

Effect of Adding Hydrogen Peroxide (H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;) and Sodium Dodecyl Sulphate (SDS) to the Properties of Fly Ash (FA)-Based Geopolymer Mortar

Geopolymer is an alternative cementitious material produced by rich aluminosilicate mineral materials (Si-Al) combine with an alkaline activator. The objectives of this study are to study the effect of adding hydrogen peroxide (H2O2) and sodium dodecyl sulphate (SDS) as foaming and stabilizing agents, respectively to the fly ash (FA)-based geopolymer mortar properties. The geopolymer mortars were synthesized with a mixture of FA, alkaline activator and SDS with different H2O2 content. The geopolymer mortars were analyzed using compressive strength test, porosity test and Scanning Electron Microscopy (SEM) analysis. Geopolymer mortar with 1 wt% H2O2 content and 0.5 wt% SDS has the lowest compressive strength (8.67 N) compare to the other geopolymer mortar composition. As H2O2 content increase with presence of SDS, the formation of the pores also increased hence resulting in the low compressive strength of geopolymer mortar.

Surfactant Penetration into Human Skin from Sodium Dodecyl Sulfate and Lauramidopropyl Betaine Mixtures.

Surfactant mixtures are used in a variety of personal care and cosmetic applications but are known to be harsh on the skin. The purpose of this study was to examine anionic surfactant penetration into human skin from nonideal surfactant mixtures under short-time exposure conditions that are relevant to realistic exposure scenarios. This was done by measuring the penetration of a radiolabeled probe (14C-SDS) into human cadaver skin in Franz diffusion cells in vitro from the mixtures of sodium dodecyl sulfate (SDS) and lauramidopropyl betaine (LAPB). Monomer and micelle concentrations in the SDS/LAPB/14C-SDS mixtures were predicted using a regular solution theory approximation. We confirmed that the mixtures of SDS and LAPB exhibit nonideal behavior with a net attraction between the two surfactants. Penetration of 14C-SDS into excised human skin from the mixtures of SDS and LAPB was found to decrease in a log-linear manner with increasing mole fraction of LAPB in the bulk solution (R2 = 0.97, p < 0.001). Additionally, the penetration of 14C-SDS into excised human skin from the mixtures of SDS and LAPB was found to correlate linearly and strongly with the predicted values of 14C-SDS monomer concentration in SDS/LAPB/14C-SDS mixtures (R2 = 0.95, p < 0.01). 14C-SDS penetration from the mixed surfactant composition could be quantitatively reconciled with that from an SDS-only composition by postulating a secondary, positive contribution from LAPB related to its own penetration and binding to skin components that increased SDS penetration at low concentrations. This research therefore supports a monomer penetration theory of surfactant penetration into the skin, combined with a measurable impact of favorable surfactant interactions within the tissue.

Effect of thickness on charge transfer properties of conductive polymer based PEDOT counter electrodes in DSSC

Poly(3,4-propylenedioxythiophene (PEDOT) counter electrodes are considered to be one of the most promising alternatives to expensive Pt-based counter electrodes in dye sensitized solar cells (DSSC). In the present study, we prepared PEDOT counter electrodes with various thicknesses through scalable electropolymerization technique using a nontoxic mixture of sodium dodecyl sulfate (SDC) in water medium, which provides the opportunity for scale up and commercialization. The time scale for electropolymerization was varied systematically to tune the thickness and uniformity of PEDOT film. The PEDOT films and their interaction with conventional iodide/triiodide​ (I−/I3−) electrolyte was studied using various electrical and optical characterization techniques. The catalytic activity of porous PEDOT films were found to be decreasing with an increase in thickness. DSSCs fabricated using PEDOT counter electrodes having lower thickness of 33 nm (deposited with 5 s polymerization time) showed superior power conversion efficiency of 10.39%, followed by PEDOT counter electrodes having 65 nm and 120 nm thickness deposited with polymerization time of 10 s and 15 s delivering power conversion efficiencies of 8.11% and 7.45% respectively. Electrochemical Impedance Spectroscopy (EIS) was used to investigate the role of variation in PEDOT thickness with various charge transfer processes at the electrolyte/counter electrode interface influencing PV performance.

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.

Inhibitory Effects of Ternary Mixtures of Sodium Dodecyl Sulfate and Heavy Metals to Acinetobacter seifertii from Otamiri River Sediment in Southeastern Nigeria

Toxicities of sodium dodecyl sulfate (SDS) and heavy metals, Pb(II), Cd(II), Ni(II), Zn(II) and Co(II), as individuals and ternary mixtures of two heavy metals and SDS to Acinetobacter seifertii isolated as preponderant bacterium from Otamiri river sediment, were assessed, using inhibition of dehydrogenase activity as end point. Among the individual toxicants, the EC50S observed ranged from 0.011 ± 0.000 mM for Cd(II) to 2.810 ± 0.140 mM for SDS. The EC50S of the toxicants were statistically different from one another and the order of increasing toxicities were SDS &gt; Ni(II) &gt; Pb(II) &gt; Zn(II) &gt; Co(II) &gt;Cd(II). The responses of the bacterium were concentration -dependent. Arbitrary (ABCR) and EC50 equieffect (EECR) fixed ratio mixtures were used to evaluate the combined toxicities of the toxicants. The concentration-response relationships of all mixtures and individual toxicants were sigmoidal and fitted with logistic function. The observed toxicities (EC50S) were compared with toxicities predicted from concentration addition (CA) and independent action (IA) models. In ABCR1 and ABCR3 mixture ratios of SDS+Ni(II)+Cd(II) and SDS+Co(II)+Cd(II) ternary mixtures, both CA- and IA-predicted EC50S were not statistically different from each other. Furthermore, in all ternary mixtures, both models underestimated the mixture toxicities to A. seifertii, except in ABCR1 of SDS+Ni(II)+Cd(II) mixture, where both models almost correctly predicted the toxicities. Basically, synergistic interaction of the mixture components observed against A. seifertii, indicates their possible toxicological effects on the bacterial population of the aquatic ecosystems.

Synthesis of a dual-microcapsule system comprising 2-ethyl hexyl acrylate monomer and benzoyl peroxide initiator and study of their application in capsular adhesives

Adhesives containing microcapsules filled with active resin materials are considered intelligent and promising systems. In this work, dual-component polyurethane/urea-formaldehyde (PU/UF) microcapsules comprising 2-ethyl hexyl acrylate monomer (EHA) and benzoyl peroxide (BPO)-filled gelatin-gum-Arabic/polyurea-formaldehyde (Gel-GA/PUF) microcapsules were synthesized. PU/UF-microcapsules containing EHA were made in an oil-in-water emulsion via in-situ and interfacial polymerizations at 1000 and 1200 rpm agitation speeds and with core-to-shell ratios of 75:25 and 85:15. The Gel-GA/PUF microcapsules were prepared in the presence of a mixture of sodium dodecyl sulfate and polyvinyl alcohol (SDS/PVA), or polyethylene maleic anhydride (EMA) at stirring rates of 500 and 700 rpm with core-to-shell ratios of 55:45 and 65:35 via consecutive complex coacervation and in-situ polymerization. The results showed that the BPO-filled Gel-GA/PUF-microcapsules synthesized at stirring speeds of 1000 and 1200 rpm were spherical with no inter-adherence and with an average diameter (dm) of 135 and 94 µm, respectively. Similarly, EHA-filled PU/UF-microcapsules synthesized in the presence of SDS/PVA at stirring speeds of 500 and 700 rpm formed free-flow powders consisting of spherical particles with a dm of 242 and 165 µm, respectively. Furthermore, adhesive formulations containing neat and microencapsulated EHA with 2.0 wt% BPO showed the best shear strength of 2.23 MPa and 1.95 MPa, respectively. These results reveal the efficacy of the EHA and BPO filled dual-component microcapsules in a capsular adhesive formulation.

Adsorption and Aggregation Behavior of Mixtures of Quaternary-Ammonium-Salt-Type Amphiphilic Compounds with Fluorinated Counterions and Surfactants.

The surface adsorption and aggregation behavior of a mixture of quaternary-ammonium-salt-type amphiphilic monomeric compounds (C4 FSA, C8 FSA, and C4 NTf2) or gemini compounds (C10-2-C4 FSA) and various surfactants (nonionic hexaoxyethylene dodecyl ether (C12EO6), anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethylammonium bromide (C12TAB), and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12Sb)) was investigated. Both types of compounds contained alkyl chains of nonidentical lengths that used bis(fluorosulfonyl)imide (FSA-) or bis(trifluoromethanesulfonyl)imide (NTf2-) as counterions. The mixtures were analyzed for surface tension, viscosity, electrical conductivity, and pyrene fluorescence, in addition to evaluation by cryogenic transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. Our results showed that the surface tension depended on the surfactant structure. For the mixture of C8 FSA and SDS, as the SDS concentration increased, the surface tension first decreased and became constant at the critical micelle concentration (CMC). In this concentration range, C8 FSA and SDS were approximately equimolar (2.5 mmol dm-3), the mixture adsorbed efficiently at the air-water interface, and vesicles and linear-type micelles were formed in the solution owing to the decreased electrostatic repulsion between the hydrophilic groups. As the SDS concentration further increased, the surface tension increased and reached another constant value. The C8 FSA at the interface was replaced by SDS and the aggregates transformed into spherical micelles. The surface tension plot of the mixture of the amphiphilic compounds and C12Sb showed a minimum at the CMC. The lowest CMC and surface tension were observed for C10-2-C4 FSA, indicating that the gemini compounds offer excellent adsorption and orientation at the air-water interface. It was revealed that the quaternary-ammonium-salt-type amphiphilic compounds in this study acted as ionic liquids on their own and as surfactants in aqueous solution. Further, they could improve the surface activity of conventional ionic surfactants.

Conductivity and cloud point studies of the interaction of lomefloxacin hydrochloride with anionic and nonionic surfactants in electrolytes solution

The interaction of lomefloxacin hydrochloride (LMFH) drug (utilized to treat different bacterial infections) with anionic (sodium dodecyl sulfate (SDS)) and nonionic (triton X-100 (TX-100)) surfactants in electrolytes media has been carried out applying the conductometric and cloud point (CP) measurement methods. SDS is very useful to prohibit different viral infections and to extract DNA/RNA. Two critical micelle concentrations (cmc) were observed for LMFH + SDS mixtures within the investigated surfactant concentration. The cmc values of SDS increase monotonically with the increase of the LMFH concentration. The cmc values of LMFH + SDS mixtures were reduced as the ionic strength of electrolytes increases. In the case of the LMFH + SDS mixture, the cmc values showed reverse U-shaped change with the augmentation of temperature in the electrolyte medium. The extent of counterion binding (β) varies significantly with the change of ionic strength of the electrolytes and concentration of the drug. The CP values of the LMFH + TX-100 mixture was increased and decreased with the enhancing of LMFH and electrolyte concentrations respectively. The standard Gibbs free energy changes both for first and second micellization (ΔG1,mo &ΔG2,mo) were attained to be negative throughout the study suggesting spontaneous micellization of LMFH + SDS mixture in all the cases. The ΔG1,mo &ΔG2,mo values increase with the increase of temperature. Again, ΔG2,mo > ΔG1,mo signify that second micellization is more spontaneous. The positive free energy changes of the LMFH + TX-100 mixture reveal the nonspontaneous nature of the clouding process. The non-spontaneity of clouding experiences a reduction with the rise of TX-100 concentration. The other thermodynamic parameters, transfer properties as well as entropy-enthalpy compensation parameters of micellization and clouding processes have been assessed. The intrinsic enthalpy (ΔHmo,∗) values reveal that micelle is more stable in electrolyte media.

A detailed morphology investigation on the effects of mixed anionic and nonionic surfactants on methane hydrate formation and dissociation

Foam generation from the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter in methane hydrate formation can be potentially reduced by using mixed surfactants. Mixtures of SDS with nonionic surfactants were proposed to solve this problem. Polyoxyethylene (n) lauryl ether (EO3 and EO5) and alkyl poly glycol ether (APG) were chosen to mix with SDS in different concentrations at 8 MPa and 4 °C in the quiescent system for both kinetics and morphology studies. The result showed that the addition of EO3 resulted in the slight increase for the induction time but no change in the formation rate. Adding EO5 showed the stochastic phenomenon on hydrate formation kinetics. In the presence of APG, the induction time increased up to ten times and lowered the hydrate formation rate compared to only 0.25 wt% SDS. The methane uptakes were about the same with all conditions. The morphology showed similar hydrate formation and dissociation patterns with all investigated solutions. Interestingly, the mixture of nonionic surfactants with SDS decreased the foam formation compared with the system with only SDS. The addition EO3 showed the gradual decrease in the foam height with the higher concentration of EO3. Adding the highest EO5 concentration showed the optimum foam reduction compared with all conditions. Moreover, the presence of APG showed the similar effects of foam reduction with EO5.