Presence Of Ionic Surfactants Research Articles

Spectroscopic and interfacial investigation on the interaction of hemoglobin with conventional and ionic liquid surfactants

A comprehensive investigation on the interactions between equine heart hemoglobin and different surface active agents including ionic liquid surfactants (ILs) was performed in aqueous buffer (pH = 7.4) by ultraviolet-visible and fluorescence spectroscopic techniques coupled with tensiometry. The surface active agents include a cationic surfactant cetyltrimethylammonium bromide (CTAB), two cationic ILs 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl), 1-butyl-3-methylimidazolium octyl sulfate (C4MeImOS), three anionic surfactants sodium N-dodecanoyl sarcosinate (SDDS), sodium dodecylbenzene sulfonate (SDBS), sodium cholate (NaC), and a non-ionic surfactant N-decanoyl-N-methylglucamine (Mega 10). In particular, surfactant-induced conversion of the iron coordination and spin states of hemoglobin was monitored by the shifts of the Soret peak. Fluorescence studies indicated exposure of the tryptophan and tyrosine residues of hemoglobin to polar environment when surface active agents were introduced, the relative contributions of these amino acids to the fluorescence intensity being different for different surfactants. Hemoglobin was found to be unfolded in surfactant solutions. Unfolding of hemoglobin was found to be more pronounced in presence of ionic surfactants than in presence of the non-ionic one.

Prediction of oil/water interfacial tension containing ionic surfactants

This study introduces a new approach to predict interfacial tension (IFT) at oil/water interfaces in the presence of ionic surfactants. Experimental data for sodium dodecylsulphate (SDS), decyltrimethylammonium bromide (C10TAB) and dodecyltrimethylammonium bromide (C12TAB) at hydrocarbon/water interfaces are used to validate the new approach. The model parameters, including molar surface area (ω) and bulk-surface distribution coefficient of surfactant (KS) are obtained by fitting the proposed equation to the literature data. The change of model parameters at different interfaces is discussed. In all cases investigated, the deviation of results for the suggested equations is less than previous work. A good agreement between results and experimental data is obtained in the concentration region below and near the critical micelle concentration.

Regulation of interphase processes by surfactants and their compositions in the development of oil recovery technology

Physicochemical aspects of the regulation of interfacial processes occurring at the oil-water-rock interface in the presence of ionic surfactants and their compositions are considered with the goal of developing efficient, scientifically grounded innovative technologies ensuring enhanced oil recovery and refining. A complex of studies of surface phenomena in the presence of ionic surfactants made it possible to identify criteria for evaluating the effectiveness of their action at the oil-water-rock interface, which makes it possible to predict the behavior of surfactants in real conditions of oil production and to use them purposefully in various enhanced oil recovery technologies.

Micellization Behavior of Ionic Surfactants in Presence of Butanol Isomers in Non-aqueous Solutions

.

Heterocoagulation of shale particles and bubbles in the presence of ionic surfactants

Adsorption of surfactants is one of the important feature governing interactions between particulate matters. When interactions occur between two particulates, which differ from each other, heterocoagulation takes place. This paper explains heterocoagulation of bubbles and carbonaceous metal-bearing shale particles. Heterocoagulation was experimentally studied using zeta potential, adsorption and contact angle tests. The results indicated that heterocoagulation in the presence of ionic (anionic sodium dodecyl sulfate SDS, and cationic dodecylamine hydrochloride DDA) surfactants was feasible. Based on the results, the heterocoagulation mechanism was evaluated, and thus the mechanism of shale flotation in the presence of ionic surfactants was elucidated.

Clouding Behaviour of Polysorbate 80: Effect of Additives

AbstractPolysorbate 80 and sodium lauryl ether sulphate mixtures are often used in personal care products especially in shampoo formulations. In this paper, the combined effect of sodium lauryl ether sulphate and salts (Na2SO4, NaCl, CaCl2) and sodium lauryl ether sulphate and alcohols having different chain length on the cloud point of polysorbate 80 has been studied. The cloud point of a nonionic surfactant is influenced by the presence of additives. In the current system, a rise in the cloud point of polysorbate 80 was observed in the presence of ionic surfactant, sodium lauryl ether sulphate (0.010–0.050 mM) which is interpreted as increase in the surface charge of micelle. The cloud point of the sodium lauryl ether sulphate-polysorbate 80 mixture decreased with the addition of inorganic salts. The presence of short chain alcohols (C1–C3) was found to increase the cloud point of polysorbate 80-sodium lauryl ether sulphate mixtures whereas, long chain alcohols (C4, C5) were found to decrease the cloud point of polysorbate 80-sodium lauryl ether sulphate mixtures depending on their solubility in water.

Aggregation and conformational stability evaluation of myoglobin in the presence of ionic surfactant

Sodium lauroyl sarcosinate (SLS) is frequently used for the solubilization of inclusion bodies in vitro due to its structural similarity to lipid plasma membrane. There are many factors that could influence protein aggregation propensity, including overall protein surface charge and hydrophobicity. Here, the aggregation pathway of myoglobin protein was studied under different conditions (pH 3.5 and 7.4) in the presence of varying concentrations of SLS to evaluate the underlying forces dictating protein aggregation. Data obtained from Rayleigh light scattering, ThT binding assay, and far-UV CD indicated that SLS have different effects on the protein depending on its concentration and environmental conditions. In the presence of low concentrations of SLS (0.05–0.1 mM), no aggregation was detected at both pH conditions tested. Whereas, as we reach higher SLS concentrations (0.5–10.0 mM), myoglobin started forming larger-sized aggregates at pH 3.5 and not pH 7.4. These results suggest that electrostatics interactions as well as hydrophobic forces play an important role in SLS-induced myoglobin aggregation.

Electrocatalytic Hydrogenolysis of Chlorophenolic Compounds by Modified Electrodes in Aqueous Medium in the Absence and the Presence of Ionic Surfactant

AbstractThe electrocatalytic hydrogenolysis of different chlorophenolic compounds, namely 2-chlorophenol (2CP) and pentachlorophenol (PCP) was performed on nickel-silica (Ni-SiO2) and nickel-clay (Ni-CY) electrode catalyts. The influence of the catalytic support and the surfactant agent was studied in aqueous media at different pH. Results demonstrated that different regioselectivities were observed according to the used catalytic support. The cyclohexanone was obtained as the major product. In presence of ionic surfactants (SDS and CTAB), the investigated electrodes exhibited a promising dechlorination and hydrogenation potential of aromatic halides with high electrocatalytic activity and good stability.

Extraction, Preconcentration, and Quantification of Low Levels of Free Formaldehyde from Some Beverage Matrices by Combination of Ultrasound-Assisted-Cloud Point Extraction with Spectrophotometry

In the present study, due to use of formaldehyde (FA) as a food additive as well as its endogenous and natural occurrence in aquatic products, a new preconcentration method for the quantification of free formaldehyde (FA) in beverages was developed before analysis by spectrophotometry at 538 nm. The method is based on spontaneously Cannizzaro disproportionation of FA with Variamine blue (VBH2) in the presence of ionic surfactant, sodium dodecylsulfate (SDS) as both sensitivity enhancer and counter ion at pH 7.0, and then extraction of the formed ion-pairing complex into the nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114). The effect of analytical variables was evaluated in detail, and the optimal working conditions were established. There was a rectilinear relationship in the range of 2–400 μg L−1 with changing sensitivity. The limits of detection and quantification of the method with a sensitivity enhancement of 65 after preconcentration were 0.53 and 1.76 μg L−1, respectively. The accuracy was validated by using two spiked quality control samples in linear working range and by comparing the results obtained from the samples with those of independent method, which is known as a slight modified acetylacetone method. It has been observed that the results obtained by both methods are statistically compatible with a t value ranging from 0.09 to 0.65 (t critical 2.31). The intra-day and inter-day precisions as a result of stabilization of mixed micellar system were lower than 4.9% (as RSD%, n 5), and the recoveries were quantitatively higher than 95% for the two quality control samples spiked with 10, 25, and 50 μg L−1 with satisfactory results. The method was successfully applied to the quantification of low levels of free FA in selected beverage matrices.

Dextran Nanoparticles Cross‐Linked in Aqueous and Aqueous/Alcoholic Media

The attractiveness of the dextran nanoparticle application in medicine and pharmacology results from biocompatibility, biodegradability, and nontoxicity of the polymer. However, it still remains a challenge to prepare such nanoparticles in an aqueous medium due to dextran hydrophilicity. Here, the technique of dextran nanoparticle synthesis with the average diameter of 140–450 nm in aqueous and aqueous/ethanolic media is described. The chemical structure of cross‐linker used for the dextran nanoparticle stabilization is demonstrated to influence the dextran nanoparticle diameter, size distribution, and ζ‐potential. As shown the regulation of the nanoparticle diameter and ζ‐potential is possible through the surfactants and/or dextran nonsolvent (ethanol) addition into the reaction medium. Due to the additional steric stabilization, the dextran nanoparticles of minimum diameter are formed in the presence of ionic surfactants in the aqueous/ethanolic medium. The nanoparticle shape and diameter are analyzed by dynamic light scattering, transmission electron microscopy, and scanning electron microscopy; the composition is investigated by 1H NMR spectroscopy. image

Graphene-based LbL deposited films: further study of electrical and gas sensing properties

Graphene-surfactant composite materials obtained by the ultrasonic exfoliation of graphite powder in the presence of ionic surfactants (either CTAB or SDS) were utilised to construct thin films using layer-by-layer (LbL) electrostatic deposition technique. A series of graphene-based thin films were made by alternating layers of either graphene-SDS with polycations (PEI or PAH) or graphene-CTAB with polyanions (PSS). Also, graphene-phthalocyanine composite films were produced by alternating layers of graphene-CTAB with tetrasulfonated nickel phthalocyanine. Graphene-surfactant LbL films exhibited good electric conductivity (about 0.1 S/cm) of semiconductor type with a band gap of about 20 meV. Judging from UV-vis spectra measurements, graphene-phthalocyanine LbL films appeared to form joint π-electron system. Gas sensing testing of such composite films combining high conductivity of graphene with the gas sensing abilities of phthalocyanines showed substantial changes (up to 10%) in electrical conductivity upon exposure to electro-active gases such as HCl and NH 3 .

Characterisation of thin films of graphene-surfactant composites produced through a novel semi-automated method.

In this paper we detail a novel semi-automated method for the production of graphene by sonochemical exfoliation of graphite in the presence of ionic surfactants, e.g., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). The formation of individual graphene flakes was confirmed by Raman spectroscopy, while the interaction of graphene with surfactants was proven by NMR spectroscopy. The resulting graphene–surfactant composite material formed a stable suspension in water and some organic solvents, such as chloroform. Graphene thin films were then produced using Langmuir–Blodgett (LB) or electrostatic layer-by-layer (LbL) deposition techniques. The composition and morphology of the films produced was studied with SEM/EDX and AFM. The best results in terms of adhesion and surface coverage were achieved using LbL deposition of graphene(−)SDS alternated with polyethyleneimine (PEI). The optical study of graphene thin films deposited on different substrates was carried out using UV–vis absorption spectroscopy and spectroscopic ellipsometry. A particular focus was on studying graphene layers deposited on gold-coated glass using a method of total internal reflection ellipsometry (TIRE) which revealed the enhancement of the surface plasmon resonance in thin gold films by depositing graphene layers.

Application of Group Contribution–NRTL Model with Closure to Predict LLE Behavior of an Oil/Brine/Surfactant System

Distribution of surfactants in an aqueous/nonaqueous two phase system is of the great importance especially in enhanced oil recovery (EOR) processes. In this paper, the application of genetic algorithm to estimate the binary interaction parameters of the nonrandom two liquid (NRTL) activity coefficient model for a brine/oil/ionic surfactant system has been investigated. The presence of ionic surfactant in the system has been taken into account by employing the modified Debye–Huckel model. Moreover, the binary interaction parameters used in NRTL activity coefficient model were found to be interdependent and related to each other by a set of linear equations known as closure equations. These equations were considered as constraints to the optimization calculations. On the other hand, when experimental data were not available, the LLE data were estimated primarily through the Scatchard–Hildebrand activity coefficient model. These data were used to evaluate the GC–NRTL model parameters and calculate equilibri...

Water Dispersible, Positively and Negatively Charged MoS2 Nanosheets: Surface Chemistry and the Role of Surfactant Binding.

Stable aqueous dispersions of atomically thin layered MoS2 nanosheets have been obtained by sonication in the presence of ionic surfactants. The dispersions are stabilized by electrostatic repulsion between the sheets, and we show that the sign of the charge on the MoS2 nanosheets, either positive or negative, can be can be controlled by the choice of the surfactant. Using techniques from solution NMR, we show that the surfactant chains are weakly bound to the MoS2 sheets and undergo rapid exchange with free surfactant chains present in the dispersion. In situ nuclear Overhauser effect spectroscopic measurements provide direct evidence that the surfactant chains lie flat, arranged randomly on the basal plane of the MoS2 nanosheets with their charged headgroup exposed. These results provide a chemical perspective for understanding the stability of these inorganic nanosheets in aqueous dispersions and the origin of the charge on the sheets.

Interfacial equation of state for ionized surfactants at oil/water interfaces.

A new mathematical approach has been developed for describing the interfacial behaviour of oil/water interfaces in the presence of ionic surfactants. The approach relies on the ideal behaviour of ionized surfactants at oil/water interfaces, which is previously demonstrated by Lucassen-Reynders (J. Phys. Chem., 1966, 70, 1777-1785). The new derived equation simply relates the interfacial tension to the surfactant molecular size and the cmc value of the surfactant in the aqueous phase. The predicted values are in a reasonable agreement with the measured experimental data. Formation of complex multi-layers is considered and the related development is performed. It is shown that, assuming a multi-layer interface, the proposed model gives an area per surfactant molecule similar to the values obtained by techniques such as neutron reflectivity (NR), while a monolayer assumption yields about half the value. The discussion describes the impact of dissolved oil and ionic components on the interfacial tension of the ionized surfactants at oil/water interfaces.

Application of chemometrics in determination of the acid dissociation constants (pKa) of several benzodiazepine derivatives as poorly soluble drugs in the presence of ionic surfactants

In this study, the acid dissociation constants (pKa) of some benzodiazepine derivatives including chlordiazepoxide, clonazepam, lorazepam, and oxazepam in aqueous micellar solution were determined spectrophotometrically at an ionic strength of 0.1M at 25°C.The effect of cetyl trimethylammonium bromide (CTAB) as a cationic and sodium n-dodecyl sulfate(SDS) as an anionic surfactant on the absorption spectra of benzodiazepine drugs at different pH values were studied. The acidity constants of all related species are estimated by considering the surfactant concept and the application of chemometric methods using the whole spectral fitting of the collected data to an established factor analysis model. DATAN® software (Ver. 5.0, Multid Analyses AB, and Goteborg, Sweden) was applied to determine the acidity constants. In this study, a simple and fast method to determine the ionization constant (pKa) of poorly soluble drugs was developed using surfactants. The acidity constant (i.e. pKa) for chlordiazepoxide, clonazepam, lorazepam, and oxazepam were reported as 4.62, pKa1 value of 1.52 and pKa2 value of 10.51, pKa1 value of 1.53 and pKa2 value of 10.92 and pKa1 value 1.63 and pKa2 value of 11.21 respectively. The results showed that the peak values in the spectrophotometric absorption spectra of drugs are influenced by the presence of anionic and cationic surfactants. According to the results, by changing the SDS concentration from 0 to 0.05M, the pKa of chlordiazepoxide was increased to 5.9, the pKa1 of lorazepam was decreased to 0.1 while the pKa2 was increased to 11.5. Increase in SDS concentration has not shown significant alteration in pKa of clonazepam and oxazepam.Results indicate that by Changing the CTAB concentration from 0 to 0.05M, the pKa of chlordiazepoxide was reduced to 4.4, the pKa1 of clonazepam was decreased to 0.1 and the pKa2 was decreased to 9.1, the pKa1 of lorazepam was decreased to 0.4 and the pKa2 was decreased to 9.4, the pKa1 of oxazepam was decreased to 0.3 and the pKa2 was decreased to 9.7.Based on the results obtained from the study, charge of anionic and cationic surfactants leads to an electrostatic interaction between surfactant and the protonated form of the drug molecule. The electrostatic interactions can be attractive or repulsive forces and influence of separation of protons and consequently increase or decrease the acidity constants.

ELECTRICAL PROPERTIES OF SILICONE OIL-WATER INTERFACE IN THE PRESENCE OF IONIC SURFACTANTS AND SALT: IMPORTANCE IN THE STABILITY OF OIL-IN-WATER EMULSIONS

Silicone oil emulsions are used in a variety of industries. Electrical properties of the oil-water interface play a very important role in the stability of these emulsions. This work reports studies on the stability of silicone oil-water emulsions in the presence of ionic surfactants and salt. It was found that the addition of salt has a profound effect on the electrical properties of the interface. The kinetics of the growth of oil droplets in the emulsion was studied in emulsions containing a low volume fraction of silicone oil. The growth of droplets followed second-order kinetics commensurate with binary coalescence of droplets. It was found that the surfactant concentration and the presence of salt had a significant effect on the size of the droplets as well as their rate of growth. The stability of emulsions was correlated with the electrical properties of the oil-water interface and adsorption of surfactant molecules at the interface.

Effects of ionic surfactants on methane hydrate formation kinetics in a static system

This paper reports an experimental study of the kinetics of methane hydrate formation in the presence of ionic surfactants with equal carbon chain length, such as sodium dodecyl sulfate (SDS), dodecylamine hydrochloride (DAH), dodecyltrimethylammonium chloride (DTAC) and N-dodecylpropane-1,3-diamine hydrochloride (DN2Cl). Methane hydrates were formed at 274K with incipient gas pressure of 15MPa in an unstirred isochoric/isothermal reactor containing aqueous solutions at different initial surfactant loadings. It was found that addition of DTAC had little effect on methane hydrate formation whereas SDS, DAH, and DN2Cl had pronounced promoting effects. This result coincides with the fact that the Krafft point of DTAC is below 273K and those of SDS, DAH, and DN2Cl are near room temperature. At a given initial surfactant loading, the effectiveness of the surfactants for reducing the induction time of methane hydrate formation followed the order of SDS>DAH>DN2Cl. SDS also gave higher hydrate growth rates than DAH and DN2Cl. At 1000 and 2000ppm, however, DN2Cl gave slightly higher final methane uptake than SDS. It was also found that during the nucleation or induction period, addition of SDS, DAH and DN2Cl instead of DTAC, considerably reduced methane mole fraction in the liquid phase. Possible promotion mechanisms of surfactants during the hydrate nucleation period were discussed.

Self-association of sodium deoxycholate with EHEC cellulose cooperatively induced by sodium dodecanoate

Some aspects of ethyl (hydroxyethyl) cellulose (EHEC) aqueous behavior in the presence of ionic surfactants are described in the literature; however, most of the studies reported address moderately concentrated solutions. Few studies have been carried out in the dilute regime using mixtures of biosurfactants. The main purpose of this work is to investigate the interaction of EHEC in the dilute regime and to verify the mixture of two surfactants: sodium deoxycholate (NaDC) and sodium dodecanoate (SDoD). The parameters of the surfactant to polymer association processes such as the critical aggregation concentration (cac) and saturation of the polymer by surfactants (psp) were determined from the plots of surface tension and specific conductivity versus surfactant concentration in basic conditions. The cmc of NaDC–SDoD mixtures showed non-ideal behavior. However, EHEC added to mixtures of SDoD and NaDC acts as a stabilizer for the mixed aggregate during the association process.

Influence of Micellar Propinquity on Dynamics of Ce(IV)‐Catalyzed BZ Oscillatory Reaction under Stirred Conditions

ABSTRACTOscillating reactions often employed to mimic and understand complex dynamics in biological systems are known to be affected in aggregated host environments. The dynamic evolution of the oscillatory Belousov–Zhabotinsky (BZ) reaction upon addition of increasing amounts of anionic (sodium dodecylbenzenesulfonate; SDBS), cationic (hexadecyltrimethylammonium bromide; CTAB), nonionic (polyoxyethylene(20) cetyl ether; Brij58), and binary mixtures (CTAB + Brij58 and SDBS + Brij58) of surfactants was monitored using potentiometry at 25 and 35°C under stirred batch conditions. The experimental results reveal that the oscillatory parameters of the Ce(IV)‐catalyzed BZ reaction are significantly altered depending on the concentration and nature of restricted micellar host environments. In the presence of ionic surfactants, it is proposed that the evolution of the oscillatory BZ system may be due to atypical proficiency (related to hydrophobic and electrostatic interactions) of such organized self‐assemblies to affect the reactivity by selectively confiscating some key reacting species. However, the response of the BZ system to nonionic Brij58 was attributed to the reaction among the alcoholic functional groups of the surfactant with some vital species of the BZ reaction. Moreover, the nonionic + ionic binary surfactant systems exhibited behaviors representative of both the constitutive single surfactant systems.