Critical Micelle Concentration Of Sodium Dodecyl Sulfate Research Articles

Application of Alcohols to Inhibit the Formation of Ca(II) Dodecyl Sulfate Precipitate in Aqueous Solutions.

The presence of alkaline earth cations, in particular, Ca2+ and Mg2+ ions in brine, causes undesired effects in solutions containing anionic surfactants because of precipitate formation. In the present study, an anionic surfactant, sodium dodecyl sulfate (SDS), was investigated, focusing on the determination of various properties (surface tension, critical micelle concentration, micelle size, turbidity) in the presence of alcohols and, in particular, the inhibition of the precipitation of SDS with calcium ions. The calcium ions were added to the surfactant in increasing concentrations (3.0-10.0 g/L), and short-carbon-chain alcohols (methanol, ethanol, n-propanol and n-butanol) were used to shift the onset of precipitate formation. The critical micelle concentration (CMC) of SDS in the presence of alcohols was also determined. It was established that among these alcohols, methanol and ethanol did not exert significant effects on the solubility of the Ca(DS)2 precipitate, while n-propanol and n-butanol were found to be much more efficient inhibitors. In addition, all the alcohols in the applied concentration range (up to 20 V/V%) were found to decrease the critical micelle concentration of SDS.

Interaction of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine drug in aqueous solution: Conductometric and molecular dynamics studies

In the present work, the interaction of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine drug in aqueous solutions was studied using conductometric measurements and molecular dynamic simulation. Conductometric data were used to determine the critical micelle concentration (CMC) values of surfactants on various amantadine aqueous solutions at T= (300.2, 310.2 and 320.2) K and 0.1 MPa. The effect of amantadine concentration (m = 0.0005, 0.0010, 0.0015 and 0.002 mol.kg−1) on CMC of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants was investigated. It was observed the CMC value of sodium dodecyl sulfate surfactant increases with increasing of amantadine concentration whereas the CMC values of cetyl trimethyl ammonium bromide surfactant decrease with increasing of amantadine concentration at the same temperature. Then, the thermodynamic properties such as standard Gibbs free energy, enthalpy, and entropy for micellization in aqueous solutions were determined. In addition, molecular dynamic simulation was carried out to understand the interaction sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine at the molecular level and microscopic interactions. The root-mean-square deviations and electrostatic, hydrogen binding and hydrophobic interactions were determined by MD simulations. It was seen, the electrostatic and hydrogen bonding interactions play a crucial role in sodium dodecyl sulfate and amantadine aqueous system. The obtained results showed the simulation and experimental data are in agreement with each other.

Quick nozzle mixing technology for 3D printing foam concrete

Foam concrete has begun to be combined with 3D printing technology considering multiple advantages, including fire resistance, thermal insulation, sound absorption, and environmental friendliness. However, the traditional production and pumping processes could be challenging. This study attempted to simplify the foaming process using the Quick Nozzle Mixing technology (QNM) with Sodium dodecyl sulfate (SDS) as a foaming agent. First, the surface tension of mixing water with varying dosages of SDS was evaluated. Secondly, the effects of mixing methods on the wet density, flowability, foaming efficiency, and compressive strength of concrete with SDS were investigated. Results show that QNM is a feasible approach directly to producting and printing foam concrete with a low wet density of 1500 kg/m3 and printed compressive strength of 3.5 MPa. Regardless of mixing methods, the critical micelle concentration of SDS dominated the development of flowability, wet density and compressive strength. When the SDS dosage was beyond the critical value, these properties notably changed with increasing SDS dosages. Regarding the Quick Mixing Method, the mixing duration regulated the foaming effect of SDS in concrete. The compressive strength decreased with mixing duration; this effect became more pronounced by increasing SDS dosages. Finally, a relationship was found between compressive strength and wet density that held regardless of mixing method and SDS concentration.

Understanding the effect of moderate concentration SDS on CO2 hydrates growth in the presence of THF

HypothesisAdditives like Tetrahydrofuran (THF) and Sodium Dodecylsulfate (SDS) improve Carbon Dioxide (CO2) hydrates thermal stability and growth rate when used separately. It has been hypothesised that combining them could improve the kinetics of growth and the thermodynamic stability of CO2 hydrates.Simulations and ExperimentsWe exploit atomistic molecular dynamics simulations to investigate the combined impact of THF and SDS under different temperatures and concentrations. The simulation insights are verified experimentally using pendant drop tensiometry conducted at ambient pressures and high-pressure differential scanning calorimetry.FindingsOur simulations revealed that the combination of both additives is synergistic at low temperatures but antagonistic at temperatures above 274.1 K due to the aggregation of SDS molecules induced by THF molecules. These aggregates effectively remove THF and CO2 from the hydrate-liquid interface, thereby reducing the driving force for hydrates growth. Experiments revealed that the critical micelle concentration of SDS in water decreases by 20% upon the addition of THF. Further experiments in the presence of THF showed that only small amounts of SDS are sufficient to increase the CO2 storage efficiency by over 40% compared to results obtained without promoters. Overall, our results provide microscopic insights into the mechanisms of THF and SDS promoters on CO2 hydrates, useful for determining the optimal conditions for hydrate growth.

A comprehensive assessment of interfacial and bulk properties of sodium dodecylsulfate via addition of competitive Hofmeister ions in presence of Cosolvent: A combined experimental and theoretical study

The synergistic interaction of sodium dodecyl sulphate (SDS) and added electrolyte in presence of cosolvent is investigated by determining the critical micelle concentration of SDS. The present system is carried out with two different types of counterions from Hofmeister series where Hofmeister chaotropic ion i.e. NH4+ is attracted more towards the negatively charged chaotropic dodecyl sulphate headgroup of SDS than the kosmotropic ion. To understand the thermodynamic behavior of SDS micelle, counterion binding constant values are measured using the well-established Corrin-Harkins or modified Corrin-Harkins equations. Various assessments of aggregation and adsorption phenomena of SDS micelle are established from both experimental and theoretical concepts. The exchange of counterion i.e. Na+ ion by NH4+ ions can occur at a particular electrolyte concentration where SDS micelle leads to the formation of ammonium dodecyl sulphate (AmDS) in the present cosolvent media. Therefore, the Hofmeister chaotropic ion (NH4+) is found to be a competitive ion. In addition to that, solvophobicity of the cosolvent mixture is another important parameter which could influence SDS micellization differently.

Synergy in the Microbial Cyclic Lipopeptide/Petroleum-Derived Surfactant Mixture Can Reduce the Total Surfactant Consumption

We report the synergistic effect of the addition of a microbial cyclic lipopeptide, surfactin (SF), to the most common petroleum-derived surfactant, sodium dodecyl sulfate (SDS). The addition of a small amount of SF (0.1 mol %) to an aqueous solution of SDS reduces the critical micelle concentration (CMC) of SDS from 10–3 to 10–6 M order. The addition of SF to SDS at various ratios lowered the surface tension at the CMC of SDS, indicating CMC reduction and, thus, the minimization of total SDS consumption without loss of surface activity. Surface tension measurement and nuclear magnetic resonance spectroscopy were conducted to analyze the synergy between SDS and SF in aqueous solutions as a function of composition. The interaction parameters of the mixed monolayer and mixed micelles were negative, indicating the occurrence of attractive interactions between SDS and SF, which were stronger than those among the individual surfactants. Moreover, the surface tension at the CMC, area occupied per surfactant molecule, difference in the interaction parameter, and 1H NMR chemical shift values of the SDS/SF mixtures as a function of their composition exhibited an extremum at a mole fraction of 0.7. These results suggest that SF has the peculiarities of encapsulation of the anionic surfactant of SDS within the inner cavity and can screen the electrostatic repulsion of SDS via the formation of their inclusion complex at SDS:SF = 2:1, which facilitates the formation of mixed monolayers and micelles in a more stable state.

Mixed micelle formation by sodium dodecylsulfate and dodecyltrimethylammonium bromide in aqueous ionic liquid media

Surfactant self-aggregation within ionic liquid (IL) - based media has been investigated to compare and contrast the role of such media with that of water. Behavior of a surfactant mixture constituting of two surfactants with oppositely charged head groups, namely anionic sodium dodecylsulfate (SDS) and cationic n-dodecyltrimethylammonium bromide (DTAB), is assessed in aqueous IL media. Contrary to what is observed in water, it is shown earlier that effective charge screening of the surfactant headgroups by IL ions in a typical IL 1-ethyl-3-methylimidazolium ethylsulfate ([C2C1im][EtSO4]) results in formation of (SDS + DTAB) mixed micelles with critical micelle concentrations (CMCs) ranging between those of SDS and DTAB, respectively. The miscibility of (SDS + DTAB) mixture in aqueous [C2C1im][EtSO4] reveals that as the content of IL [C2C1im][EtSO4] is increased, the miscibility of the surfactant mixture improves indicating increased charge screening involving ions of the IL and the surfactant headgroups. For water mole fraction (XW) ≤ 0.90, (SDS + DTAB) surfactant mixture is miscible in aqueous [C2C1im][EtSO4] system in all proportions. For 1.00 ≥ XW≥ 0.90, while synergism persists due to the presence of attractive electrostatic attraction between SDS and DTAB headgroups leading to mixture CMCs below the CMCs of SDS and DTAB, respectively, the extent of synergism diminishes with increase in IL [C2C1im][EtSO4] in the solution. For XW = 0.80, the (SDS + DTAB) mixture exhibits CMC values that are closest to the values estimated assuming ideal behavior. For 0.70 ≥ XW ≥ 0.30, the (SDS + DTAB) exhibits antagonistic trend with CMC values higher than those estimated for ideal solution; the antagonistic trend gradually decreases with increase in [C2C1im][EtSO4] and again attains close to ideal behavior in neat IL [C2C1im][EtSO4]. This trend is subsequently manifested in the composition of the mixed micelles as well as in the net interaction parameter, β. Addition of small proportion of IL to water helps in solubilization of surfactant mixture of oppositely charged surfactants due to effective charge screening of the surfactant headgroups and results in formation of mixed micelles in aqueous IL media over complete composition range.

Critical micelle concentration of SDS through DPD simulations using COSMO-RS–based interaction parameters, the thermal effects

In order to obtain the critical micellar concentration (CMC) for sodium dodecyl sulfate (SDS) in water at 288.15, 293.15, 298.15, 303.15 and 308.15 K, two approaches were employed: the first, consisting of experimental Isothermal Calorimetric Titration (ITC) and the second by using Dissipative Particle Dynamics (DPD) simulations. To determine the experimental CMC the calorimetric signal was treated with the software D/STAIN, obtaining values between 8.24 and 9.22 mM, which are in good agreement with other experimental determinations. Also the SDS micellization enthalpies found agree with previous experimental reports. The pairwise aij DPD interaction parameters, needed to run the simulations, were obtained from quantum chemistry calculations under the application of the COSMO-RS solvation scheme jointly with the Flory-Huggins theory. A series of systems with variable concentration of SDS in water were simulated for each temperature. Then, the analysis of the percentage of aggregation of SDS molecules at each temperature, enable to visualized the theoretical aggregation isotherms. By delimiting an experimental CMC window, the DPD aggregation isotherms were used to identify the concentration where either the monomeric or micellar states domain. Intersection of linear fits, in the monomeric and in the micellar regime produced theoretical CMCs values from 8.1 to 8.9 mM. These results compare favorably with the experimental determinations at each temperature.

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.

Micellization, interaction and thermodynamics behavior of BSA + SDS mixture in aqua-organic mixed solvent: Influences of temperature and solvent composition

The interaction of bovine serum albumin (BSA) with sodium dodecyl sulphate (SDS) in aqueous medium as well as aqua-organic mixed media has been performed using the conductivity measurement technique at several temperatures. The experiments were performed in the temperature ranges of 298.15–313.15 K with a gap of 5 K. The critical micelle concentration (CMC) and the degree of micelle ionization (α) have been computed from the specific conductivity versus the surfactant concentration plot. The CMC values achieved in the present study are dependent on the concentration of BSA, composition of the mixed solvent, and a variation of experimental temperature. For SDS + BSA mixture, an increase of BSA concentration causes a decrease in the values of CMC. Also, the values of CMC of SDS + BSA system in water-organic solvents were found to follow the order: CMCwater-DMF > CMCwater-AN > CMCwater-DMSO > CMCwater. In every case examined, the association of SDS + BSA mixture was spontaneous (negative ΔG0m). On the basis of observed ΔH0m and ΔS0m values for the SDS + BSA mixed system, it is expected that an electrostatic, hydrophobic, and ion–dipole interactions are in effect between SDS and BSA species, whereas the hydrophobic interaction is believed to be the main driving force for the aggregation process. In each of the case thoroughly detected, a linear relationship between ΔH0m and ΔS0m values was viewed, which is a strong indication in favor of the presence of enthalpy–entropy compensation phenomenon in the overall interaction process.

Spectrophotometric study of the sodium dodecyl sulfate in the presence of methylene blue in the methanol–water mixed solvent system

The methylene blue (MB) dye is very sensitive to changes in the polarity of its surroundings. The interaction of MB with sodium dodecyl sulfate (SDS) was studied spectrophotometrically in 0.1, 0.2, 0.3 and 0.4 vol fractions of methanol in an aqueous medium. The dielectric constant value decreases with the addition of methanol in the water and hence there is the lower stabilization of the lowest unoccupied molecular orbital which results in the hypsochromic shift in the monomeric form of methylene blue. In a 0.1 vol fraction of methanol, the peaks are seen at 665 and 612 nm, which are monomeric and dimeric MB peaks, respectively. The dimerization of MB is reduced with the increasing volume fraction of methanol in the solvent and ceases at/above 0.3 vol fraction of methanol. In the 0.4 vol fraction of methanol, the turbidity appears with the addition of SDS and there were no significant changes in the absorbance. In the presence of methanol, MB prefers to stay with the sulfate groups of SDS at the peripheral regions of the premicelle and micelle. At very low surfactant concentrations, far below their critical micelle concentration (CMC), the formation of MB-MB dimers and/or MB-SDS ion pairs or clusters occurs, and a corresponding shift in absorption and decrease in absorbance is observed. On increasing the concentration of SDS, micellization occurs, which disrupts the MB-MB dimers and MB-SDS ion pairs are incorporated with the micelles. On further addition of SDS, lone MB monomers become associated with these micelles and the absorbance increases slightly higher than those of the original dye in the solvent. This is the case of dye solubilization where monomers are completely incorporated or bounded by micelles. The CMC of SDS decreases in the presence of dye suggesting the strong interaction between the oppositely charged dye-surfactant ion pairs. The value of binding constant and partition coefficient decreased with the increasing volume fraction of methanol. The negative value of ΔGb indicates that the interaction between SDS and MB is spontaneous but the negative values of ΔGb decreased with the increasing volume fraction of methanol.

Ability of Sodium Dodecyl Sulfate (SDS) Micelles to Increase the Antioxidant Activity of α-Tocopherol.

As emulsifiers become saturated on the surface of an emulsion droplet, any additional emulsifier migrates to the aqueous phase. Continuous phase surfactants have been shown to increase α-tocopherol efficacy, but it is unclear if this is the result of chemical or physical effects. The addition of α-tocopherol to an oil-in-water emulsion after homogenization resulted in a 70% increase of α-tocopherol in the continuous phase when sodium dodecyl sulfate (SDS) was at levels that were greater than the SDS critical micelle concentration. Conversely, when α-tocopherol was dissolved in the lipid before emulsification, continuous phase SDS concentrations did not increase. When SDS concentration led to an increase in the aqueous phase α-tocopherol, the oxidative stability of oil-in-water emulsions increased. Data indicated that the increased antioxidant activity was the result of surfactant micelles being able to decrease the prooxidant activity of α-tocopherol. Considering these results, surfactant micelles could be an important tool to increase the effectiveness of α-tocopherol.

The removal selectivity of heavy metal cations in micellar-enhanced ultrafiltration: A study based on critical micelle concentration

Micellar enhanced ultrafiltration (MEUF) is a process to remove heavy metal by complexing it with the counterionic surfactant micelle, and the complex formed was subsequently removed using ultrafiltration. The surfactant is usually added in excess, which renders high rejection (low selectivity) for all metal cations in the mixture. This work emphasises MEUF conducted at surfactant dosage around the critical micelle concentration (CMC). Few studies revealed that the presence of counterions could lower the CMC of a charged surfactant. The magnitude of reduction depends on the strength of electrostatic interaction between the counterions and surfactant. Such observation suggests that the MEUF process's selectivity could be altered based on the dosage of surfactant and the types of cations presented in the solution. This work started with determining CMC of sodium dodecyl sulfate (SDS) in the presence of single or binary metal cations at varying pH (pH 3, pH 10 and without pH adjustment). The lowest CMC (4.00 mM) was obtained in the solution containing 100 ppm copper (II) at pH 3, about 42% lower compared to CMC of SDS obtained in pure water without pH adjustment (7.00 mM). Then, the filtration was performed using 7 mM of SDS, under varying pH (pH 3, pH 10 and no pH adjustment), initial metal concentration of 100 mg/L, pressure of 2.5 bar using polyethersulfone (PES) membrane of 10 k Da molecular weight cut-off (MWCO). Overall, the highest metal rejection was obtained at pH 10, with 66% of copper and 26% of chromium (III) was rejected. The highest selectivity of copper (II) over chromium (III) was observed at neutral pH. Such findings could be due to the higher diffusivity of copper cations over chromium cations in aqueous since copper cations can reach the micelle surface and form metal-micelle complex faster than chromium cations.

Physicochemical Studies on the Interaction between Sodium Dodecyl Sulfate and Methylene Blue in Methanol-Water Mixed Solvent Media

The surface activity and the process of micellization of sodium dodecyl sulfate (SDS) with methylene blue (MB) in a methanol-water mixed solvent system were investigated by tensiometry and conductometry at 298.15 K. The measurements of surface tension and conductivity of SDS-MB complex were carried up to 0.3 volume fractions of methanol because the resulting complex appeared turbid above 0.3 volume fractions of methanol. The critical micelle concentration (CMC) of the SDS was determined from both tensiometry and conductometry. The CMC of SDS increased with the increasing volume fraction of methanol due to the inclusion of methanol in the micelles and decreased in the presence of methylene blue due to the reduction of electrostatic repulsion within the anionic moiety of SDS by the positive charge of the added dye. Different properties like surface excess concentration Γ max , minimum surface area A min , Gibbs free energy of micellization Δ G m o , surface pressure ( π CMC ), efficiency of a surfactant ( p C 20 ), packing parameter P , and standard free energy interfacial adsorption Δ G ads o of SDS in the absence/presence of MB were calculated. On the basis of Δ G m o values, it was noticed that the increasing volume fraction of methanol disfavors the micellization of SDS, while the presence of MB increased the efficiency of SDS making the micellization process more spontaneous.

Change in interfacial behavior by variation of amphiphilic nanosheets/anionic surfactant ratio using dynamic tensiometry

Nanoparticles/surfactant interplays can robustly manipulate interfacial properties, while it is still unclear how their interactions affect interface behavior. This research recap unprecedented research for determination of dynamics of adsorption and dynamic surface properties of amphiphilic sheet-like nanoparticles in anionic surfactant mixtures and generalizing their characteristics in industrial and macroscopic applications by controlling microscopic active mechanism, particularly tuning foam properties and controlling its behavior. Amphiphilic nanosheets are surface-active particles which tend to self-assemble at the air-water interface. In this study, a system of an anionic surfactant (sodium dodecylsulfate (SDS)) and an amphiphilic nanoparticle (Graphene oxide (GO)) is studied at different ratios. It appears that there is a critical value for the minimum number of surfactants per nanosheets (> 160) to make the amphiphilic nanoparticle more hydrophilic. The results set out that below this critical ratio, the amphiphilic nanoparticles are partially hydrophobic and they are surface-active enough to be adsorbed considerably at the air-water interface. The nanoparticle adsorption causes an increase in surface elasticity and a decrease in surface tension (ST). As SDS/GO ratio increases, GO particles are heavily surrounded by SDS molecules rendering them hydrophilic particles. The hydrophilic GO particles start traveling back into the bulk, drastically decreasing elasticity and increasing the ST. When SDS concentration approaches the pure SDS critical micelle concentration (CMC), there appears that some of GO/SDS complexes are still on the air-water interface to slow down the dynamics of ST. The presence of GO/SDS complexes at the interface also decreases ST to lower values compared to the pure SDS near the CMC. The hydrophilic transition of GO nanoparticles is also confirmed by ζ potential and DLS measurements. This suggests a simple way to tune foam properties and behavior by selecting proper nanoparticle/surfactant ratio.

Conductometric Study of Influence of Urea on Interactions of Sodium Dodecyl Sulfate with Cefradine

Interaction of anionic surfactant, sodium dodecyl sulfate (SDS) with antibiotic drug cefradine monohydrate (CFD) were carried out in H2O/low concentration urea medium through conductivity measurement. The variation of critical micelle concentration (CMC) of SDS with the addition of drug (CFD) discloses the presence of interaction between SDS and CFD. The CMC of SDS were attained to dwindle in the presence of CFD. The attained values of CMC show U-shaped behavior as a function of temperature. The effect of urea on the CMC values was observed to be reduced as compared to aqueous medium which is different from the most of the reports mentioned in the literature. The estimated negative values of Gibbs free energy of micellization (∆$$G_{{\text{m}}}^{^\circ }$$) express that micellization is thermodynamically spontaneous within the entire systems investigated. The magnitudes of CFD mediated enthalpy of micellization (Δ$$H_{{\text{m}}}^{^\circ }$$) as well as entropy of micellization (Δ$$S_{{\text{m}}}^{^\circ }$$) for SDS were achieved and clarified in details.

Features of self-organization of sodium dodecyl sulfate in water-ethanol solutions: Theory and vibrational spectroscopy

In this work, experimental and theoretical studies of the micelle formation processes of sodium dodecyl sulfate in water-ethanol solutions with different ethanol content - 0% by volume, 8% by volume, 15% by volume, 30% by volume were carried out. For the first time, the manifestation in the vibrational spectra of the features of self-organization of sodium dodecyl sulfate (SDS) molecules in water-ethanol solutions was found. In the studied concentration ranges of ethanol and SDS it was found that in the presence of SDS, the strengthening of hydrogen bonds in solutions is observed in a wider range of changes in the concentration of ethanol than in the absence of SDS. The behavior of the band at 1060 cm−1 at low concentrations of ethanol (8%) indicates the dual behavior of ethanol molecules as a co-surfactant and co-solvent in the process of micelle formation. The obtained experimental data are confirmed by theoretical calculations. For the first time, a contactless express method was proposed for determining the critical micelle concentration of SDS in water-ethanol solutions with different ethanol content from Raman spectra. The measured values of SDS critical micelle concentration are in good agreement with the literature data.

Critical micelle concentration, composition and thermodynamic properties of n-octyl-β-d-glucopyranoside and sodium dodecylsulfate mixed micelles

The measurements of density and viscosity of the aqueous solution of n-octyl-β-d-glucopyranoside (OGP) and sodium dodecylsulfate (SDDS) mixtures were made. On the basis of the results and those of surface tension obtained earlier the critical micelle concentration (CMC) as well as values of apparent and partial molar volume of OGP and SDDS were determined. Their partial molar volume was compared to that calculated using the bond length between the atoms in the OGP and SDDS molecules, the angle between the bonds and the average distance between the surfactant molecules and those of water. From the analysis of the CMC values it appeared that there is no ideal mixing of OGP and SDDS in the micelle and therefore the composition of mixed micelles, the activity coefficient of their components and the parameter of intermolecular interactions were determined. On the basis of the parameter of intermolecular interactions and CMC of SDDS and OGP, the synergetic effect in the mixed micelle formation was analyzed. In turn, using the mole fraction of OGP and SDDS in the micelle and their activity coefficient the standard Gibbs free energy of OGP and SDDS micellization was calculated. Next, the values obtained from this calculation were used for determination of the standard Gibbs free energy of SDDS and OGP mixture micellization. This energy was compared to that evaluated directly based on CMC of the SDDS and OGP mixture. It proved that there are differences between the values of the standard Gibbs free energy of SDDS and OGP mixture micellization calculated in these two ways which at the first approximation were close to the Gibbs free energy of OGP and SDDS mixing in the micelles determined based on their mole fraction and activity coefficient in the micelles.

Experimental investigation of self-hardening foam-sol for controlling diffusion of static coal dust

In this work, a self-hardening foam-sol (SHF) is proposed to control the diffusion of static coal dust. The SHF was mainly synthesized by a foaming solution (composed of 1 g/L polyethylene oxide (PEO), 25 g/L sodium dodecyl sulfate (SDS), 100 g/L sodium silicate and 874 g/L water) and organic acid with a concentration range of 10 to 13 g/L. Based on fluorescence spectrophotometry, drop shape analysis, X-ray photoelectron spectroscopy and scanning electron microscopy, several conclusions could be found. The critical micelle concentration of SDS was 25 g/L, when most of the pyrene pendants were solubilized into the SDS micelles to form the hydrophobic mixed micelles, and excimer formation began to reach a maximum. The SHF had optimal wetting ability with the smallest contact angle of 17o, due to PEO-bonded water and SDS forming hydrogen and a dual adsorption layer, which could enhance the wetting ability of the SHF on coal dust surfaces. The SHF had the best accepted loss of liquidity time (180–86 s) and self-hardening time (236–121 s) via the reaction of sodium silicate and organic acid. The pores and cracks among dust particles could be linked closely by SHF via the solid bridge force. The primary components were silica and sodium carbonate with crystal water and hydrophilic CO and CO or O–C–O functional groups. Based on the dust suppression experiment, the dust suppression efficiency was almost 100% at airflow speeds below 12 m/s. Obviously, the dust particles could be controlled via their surfaces being covered by a layer of SHF, since the SHF has strong hydrophilic properties and the solid bridge force. In addition, vehicle-mounted SHF preparation equipment was designed.

A MICELLAR DECONTAMINATION STRATEGY FOR REMOVING POLYCYCLIC AROMATIC HYDROCARBONS FROM THE ENVIRONMENT

Environmental decontamination requires strategies for removing organic contaminants from the ecosystem. Polycyclic aromatic hydrocarbons (PAHs) with toxic and carcinogenic properties are potentially hazardous pollutants. One suitable method for PAHs removal is their solubilization by micelles. This paper evaluates the effect of borax upon the aggregation ability of sodium dodecyl sulfate (SDS) with consequence over the micellar solubilization of naphthalene. Various techniques, such as micellar electrophoretic chromatography (MEKC), surface tension, UV-Vis and steady-state fluorescence were used to assess the micelle formation. The results show that borax decreases the critical micelle concentration of SDS and enhances the naphthalene solubilization. The work recommends borax as an efficient booster in the micellar decontamination strategy of PAHs.