Presence Of Ionic Surfactants Research Articles

Naphthalene degradation in the presence of natural–synthetic surfactants mixture by mixed bacterial cultures

Biosurfactants are the most probable future candidates to substitute the synthetic surfactants in the area of applied surfactants research. Herein we focused on the natural plant based surfactant (Reetha) extracted from the pod of Sapindus mukorossi and its substitution potential with synthetic surfactants (TX-100, CTAB, and SDBS). Mixture of Reetha and synthetic surfactants was tested for the biodegradation of naphthalene. The biodegradation efficiency of surfactants against two mixed bacterial cultures viz., defined or known culture (KC) and mining waste water culture (WWC) was investigated. Addition of Reetha in the presence of ionic surfactants has increased the degradation efficiency of naphthalene. Degradation rate constants (K) and zeta potential assessments revealed that WWC has more potential than KC with surfactant mixtures (especially CTAB-Reetha). The highest degradation potential (K value=0.31) was identified with WWC having 0.5mol fraction of Reetha in CTAB-Reetha combination. The results suggested that the use of Reetha in combination with ionic surfactants has an enormous potential to make the biodegradation process more eco-friendly and economical by decreasing the surfactant cost.

Effect of Furosemide on denaturation of lysozyme in the presence of ionic surfactant at different temperatures

The thermodynamics of Furosemide–lysozyme interaction has been studied using conductivity in combination with viscosity, density and speed of sound measurements. Lysozyme binds preferentially with Furosemide in the presence of surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). A number of physico-chemical parameters viz. critical micelle concentration (CMC), standard enthalpy of micellization (ΔHm°), standard entropy of micellization (ΔSm°), standard free energy of micellization (ΔGm°), apparent molar volume (ϕv), apparent molar adiabatic compressibility (ϕk) and relative viscosity (ηr) have been calculated from experimentally measured conductivity (κ), density (d), speed of sound (v) and viscosity (η). The critical micelle concentration data were found to pass through a broad minimum at 303K, which tends to become sharp with the increase in the [lysozyme] in case of SDS. Whereas for CTAB, CMC values, in general increase with the temperature and decrease with the increase in concentration of lysozyme. Experiments at different lysozyme concentrations and in the presence of surfactants suggest the predominant involvement of electrostatic interactions in the complexation process of Furosemide with lysozyme in the presence of SDS which induce unfolding of lysozyme as the surfactant concentration approaches its critical micelle concentration value, and non-specific interaction behaviour of Furosemide with lysozyme in the presence of CTAB.

Effect of electrolytes on wettability of glass surface using anionic and cationic surfactant solutions

Wetting behavior of a flat glass surface using pure nonionic, anionic, and cationic surfactants solutions has been studied by the dynamic contact angle (Wilhelmy plate) measurement technique. The advancing contact angle increases with the increasing concentration of surfactant and the value is maximum in the presence of cationic surfactant CTAB. The effect of different electrolytes in the presence of ionic surfactants was also studied to see the wetting behavior in the presence of electrolytes. The presence of electrolytes on ionic surfactant solutions significantly enhance the contact angle at very low concentration, which in turn lead to reduction in ionic surfactant requirement by more than 90% to achieve a particular contact angle. The effectiveness of electrolyte highly depends on the valance of counter ion. The reduction of ionic surfactant requirement is mostly useful for different applications such as flotation, and colloidal stability to reduce the production cost as well as environmental pollution.

Gas–liquid mass transfer in the presence of ionic surfactant: effect of counter‐ions and interfacial turbulence

This work investigated the effect of counter‐ions and interfacial turbulence on oxygen transfer from gas to liquid phase containing ionic surfactant, and experiments were performed in a mechanically stirred reactor with flat gas–liquid interface. Counter‐ions in terms of hydration ability and polarizability influence the interfacial coverage of ionic surfactants (i.e. cetytrimethylammonium bromide (CTAB) and cetytrimethylammonium chloride) with the same hydrocarbon chain length, producing hindrance but in different extent on oxygen transfer. The addition of electrolyte (NH4Br) substantially reduced the interfacial tension and surface charge of micelles (zeta potential) in CTAB system, and this salt effect greatly compressed interfacial double layer leading to gas transfer inhibition. The surface charge, aggregation number as well as stability of micelles formed above the critical micelle concentration could also alter interfacial configuration of surfactant layer reflected by gas absorption rate. Liquid turbulence was analyzed to decide the role of surfactant present in water on gas–liquid mass transfer, since Marangoni instability effect playing positive role should be taken into consideration under moderate liquid flow, while in turbulent system, contribution of Marangoni effect became overshadowed and consequently surfactant pose ‘barrier’ effect on gas transfer due to its surface active nature. Copyright © 2013 John Wiley & Sons, Ltd.

Electrochemical Instability in Liquid–Liquid Two-Phase Systems

Abstract On the basis of the dependency of adsorption and partitioning of ionic surfactant on the phase-boundary potential (Δ OWφ ), it is possible to understand in a unified manner various instability phenomena at the liquid|liquid interface in the presence of ionic surfactants, such as spontaneous emulsification, oscillation of Δ OWφ and interfacial tension, and irregularly increased currents on voltammograms of the transfer of surface-active ions across the interface. These instabilities are associated with the electrochemical instability, which defines a thermodynamically unstable condition at the liquid|liquid interface in terms of Δ OWφ and is a fundamental concept to understand the instabilities in the presence of ionic surfactants. The characteristic manifestations of the electrochemical instability, that is, the irregularly increased current on voltammograms in the transfer of surface-active ions, the spontaneous emulsification, and the spontaneous oscillation of Δ OWφ can be designed based on the criterion of the electrochemical instability.

Influence of the Type of Surfactant on the Mobility of Flushing Fluids for Electro-Remediation Processes

The mobility of four flushing fluids in an electro-remediation process has been studied. A mock-up plant with two rows of three electrodes positioned in semipermeable electrolyte wells was used in this study. Two different cases were considered: first an initial state when the soil was wet with water and the addition of surfactant starts, and second a second state when the surfactant front had passed through the soil. The results show that the electro-osmotic flux strongly depends on the nature of the flushing fluid and on the voltage gradient applied between electrode rows. The presence of ionic surfactants (both cationic and anionic) led to lower electro-osmotic flow-rates. The concentration of surfactants in the drain tanks increased in the case of the flushing fluid with the non-ionic surfactant because the surfactant transport was more efficient. Conversely, the anionic surfactant accumulated more in the injection well. This finding is related to the effect of migration, which in the reception wells was opposite to the electro-osmotic flux.

An Ion-Exchange Approach to the Crystal Design of Barium Sulfate in the Presence of Ionic Surfactants

Chemical reaction occurring between an insoluble solid and a saltwater solution relates to an exchange of ionic components and is therefore referred to as ion-exchange reaction. In this paper, we used the ion-exchange reaction of solid-state barium carbonate (BaCO3) and aqueous sodium sulfate (Na2SO4) for the crystal design of barium sulfate (BaSO4). This anionic ion-exchange, driven by the solubility discrepancy between BaCO3 and BaSO4, was rate-limited chemical transformation owing to the slow release of barium ions, resulting in the unusual BaSO4 crystallite with the bounded (200), (002), and (210) faces. Therein, cationic surfactant of cetyltrimethylammonium bromide (CTAB) exerted almost no influence on the morphological control of crystalline products. In a striking contrast to this, the similar cationic surfactant of CTAOH (i.e., cetyltrimethylammonium hydroxide) promoted the crystal growth along the [020] direction. Surprisingly, the addition of anionic sodium dodecyl sulfate (SDS) enhanced the sur...

Association of anionic surfactant mixed micelles with hydrophobically modified ethyl(hydroxyethyl)cellulose

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 deal with moderately concentrated solutions. Few studies have been carried out in the dilute regime using mixtures of anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecanoate (SDoD). The main proposal of this work is to investigate the interaction of EHEC in diluted regime and to verify the mixtures of the surfactants SDS and SDoD. Mixtures of EHEC and SDoD were investigated using surface tension, conductivity and transmittance measurements. Parallel experiments with EHEC in mixtures with SDS were carried out. The formation of micelles of SDoD mixed with SDS in the absence and presence of EHEC was also investigated. The transmittance vs. [SDS] and [SDoD] profiles exhibit bands that, in conjunction with conductivity and surface tension data, aid a better understanding of the behaviors of EHEC–SDS–SDoD–water solutions.

Breakup of an electrified viscous thread with charged surfactants

The dynamics and breakup of electrified viscous jets in the presence of ionic surfactants at the interface are investigated theoretically. Axisymmetric configurations are considered and the jet is surrounded by a concentrically placed cylindrical electrode, which is held at a constant voltage potential. The annular region between the jet and the electrode is taken to be a hydrodynamically passive dielectric medium and an electric field is set up there and drives the flow, along with other physical mechanisms including capillary instability and viscous effects. The jet fluid is taken to be a symmetric electrolyte and proper modeling of the cationic and anionic species is used by considering the Nernst–Planck equations in order to find the volume charge density that influences the electric field in the jet. A positively charged insoluble surfactant is present at the interface, and its evolution, as well as the resulting value of the local surface tension coefficient, is coupled with the voltage potential at the interface. The resulting coupled nonlinear systems are derived and analytical progress is made by carrying out a nonlinear slender jet approximation. The reduced model is described by a number of hydrodynamic, electrical, and electrokinetic parameters, and an extensive computational study is undertaken to elucidate the dynamics along with allied linear properties. It is established that the jet ruptures in finite time provided the outer electrode is sufficiently far away, and numerous examples are given where the dimensionless parameters can be used to control the size of the satellite drops that form beyond the topological transition, as well as the time to break up. It is also shown that pinching solutions follow the self-similar dynamics of clean viscous jets at times close to the breakup time. Finally, a further asymptotic theory is developed for large Debye layers to produce an additional model that incorporates the effects of surface charge diffusion. Numerical solutions establish that the presence of electrostatic and electrokinetic effects increases the sizes of satellites but have a rather weak influence on the time to rupture.

Statistics of rupture in relation to the stability of thin liquid films with different size

We study the stability and the thinning behavior of foam films in the presence of ionic surfactant. Using the method of capillary cell at low pressures (20–50 Pa), combined with interference microscopy, we measured the film thickness vs. time, the critical thickness of rupture, and the lifetime of films with different sizes. The film behavior is characterized by two separate stages: at first, there is a hydrodynamic thinning without rupture; afterwards, film rupture occurs as a stochastic process. The measured lifetimes in an ensemble of films are scattered in a certain range. We found that this statistical behavior is well described by a specific distribution, with cumulative probability 1 − exp(− βt 2/2). By means of theoretical considerations, this distribution is derived from the time dependent differential probability for film rupture. Fitting of experimental data for the statistics of the film lifetimes is performed. This permits one to find the average transient lifetime at the stochastic stage; thus, thinning and rupture are distinguished. The size dependence of the drainage time is shown to comply with theories which describe the behavior of films with irregular thickness. The time for thinning, and the inverse drainage rate coefficient, scale with the film radius as r f 4 / 5 . This work may be relevant to understanding the stability of fluid dispersions in dependence of the particle size.

Dynamics of Formation of Vesicles Studied by Highly Time-resolved Stopped-flow Experiments

Abstract Phase behaviour and static structure of surfactant systems have been studied in much detail, but this applies much less so to their dynamic properties. Structural transitions in amphiphilic systems can be triggered by mixing different amphiphiles. Employing the stopped-flow technique we have studied the kinetics of formation of multilamellar vesicles starting from a micellar solution and a microemulsion containing a semipolar oil. This process has been investigated for various starting conditions and as a function of the charging of the amphiphilic system. The formation process is the faster the closer the starting solution is in composition to the final state and can be slowed down by the presence of ionic surfactant.

Exploration for Micelles Driving Force from Determination of Critical Micelle Concentration of Ionic Surfactants in Presence of Hydrocortisone Acetate

It is well known that the hydrophobic group of surfactants is the main driving force for forming micelles. Chemists some times suspect by this phenomenon and, therefore, it requires further confirmations. The hydrophobic characteristics of hydrocortisone acetate (HA) may aid for understanding the latter phenomenon when use it as an additive in determinations of critical micelle concentrations (CMC) of surfactants. The effect of HA as an additive on the CMCs of anionic (sodium dodecyl sulfate, SDS, and cationic cetyltrimethylammonium bromide, CTAB) surfactants at different pH and temperatures using electrical conductivity has been investigated. It was found that the CMCs of anionic and cationic surfactants increased with increasing HA concentration at their natural media. This phenomenon is opposite to that found in the recent investigations using polar amino substituents as additives. Interestingly, it has been found that the presence of HA changes the negative sign of standard enthalpy of micellization (ΔH o ) of anionic SDS to positive. It has been concluded that the addition of HA causes unfavorable factor for micellar formation and the hydrophobic interactions should not be considered as the main driving force for micellization process.

Interaction of bovine serum albumin (BSA) with ionic surfactants evaluated by electron paramagnetic resonance (EPR) spectroscopy

EPR spectra of 5- and 16-doxyl stearic acid nitroxide probes (5-DSA and 16-DSA, respectively) bound to bovine serum albumin (BSA) revealed that in the presence of ionic surfactants, at least, two label populations coexist in equilibrium. The rotational correlation times ( τ) indicated that component 1 displays a more restricted mobility state, associated to the spin labels bound to the protein; the less immobilized component 2 is due to label localization in the surfactant aggregates. For both probes, the increase of surfactant concentration leads to higher motional levels of component 1 followed by a simultaneous decrease of this fraction of nitroxides and its conversion into component 2. For 10 mM cethyltrimethylammonium chloride (CTAC), the nitroxides are 100% bound to the protein, whereas at 10 mM N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and sodium dodecyl sulfate (SDS) the fractions of bound nitroxides are reduced to 18% and 86%, respectively. No significant polarity changes were observed in the whole surfactant concentration range for component 1. Moreover, at higher surfactant concentration, component 2 exhibited a similar polarity as in the pure surfactant micelles. For 16-DSA the surfactant effect is different: at 10 mM of HPS and CTAC the fractions of bound nitroxides are 76% and 49%, respectively, while at 10 mM SDS they are present exclusively in a micellar environment, consistent with 100% of component 2. Overall, both SDS and HPS are able to effectively displace the nitroxide probes from the protein binding sites, while CTAC seems to affect the nitroxide binding to a significantly smaller extent.

Effect of Ionic Surfactants on the Hydration Behavior of Triblock Copolymer Micelles: A Solvation Dynamics Study of Coumarin 153

Dynamic fluorescence Stokes shift measurements of coumarin 153 (C153) have been carried out to study the influence of ionic surfactants (sodium dodecyl sulfate, SDS and hexadecyltrimethylammonium chloride, CTAC) on the hydration behavior of aqueous poly(ethylene oxide)(20)-poly(propylene oxide)(70)-poly(ethylene oxide)20 (P123) block copolymer micelles. Increase in SDS or CTAC concentration at a fixed P123 concentration induces the steady-state emission spectra of C153 to shift gradually toward lower energy. This is attributed to an increase in polarity (due to enhanced hydration) experienced by the probe as a consequence of incorporation of ionic head groups in the Corona region. The observed dynamic fluorescence Stokes shift value decreases more in mixed micellar systems than in pure copolymer micelles and the trends are quite similar in the presence of SDS and CTAC. The spectral shift correlation functions were observed to be nonexponential in nature. Critical analysis of the spectral shift correlation function indicates a fast solvation component (<0.2 ns) in P123 micelles, which was absent in the presence of ionic surfactants. Due to increased hydration in the presence of ionic surfactants, the initial fast solvation event was elusive in mixed copolymer-surfactant systems, reflecting the absence of faster solvation component and reduced observed Stokes shift in mixed systems. It has been argued that in the low surfactant concentration region, increase in hydration with the incorporation of ionic head groups in the Corona region is mainly due to increase in mechanically trapped water content. However, at higher surfactant concentrations, bound water content dominates and leads to slower solvation dynamics. The present results also indicate that though CTAC alters the Corona hydration more efficiently than SDS, the overall influence of ionic surfactants on the Corona hydration is grossly similar irrespective of the cationic or anionic nature of the surfactants. Interaction of SDS and CTAC with poly(ethylene oxide)(100)-poly(propylene oxide)(70)-poly(ethylene oxide)(100) (F127) block copolymer micelles has also been studied to comprehend the effect of copolymer composition. The overall trends in dynamic fluorescence Stokes shift and solvation times are similar in both the copolymer micelles.

Binary Coalescence of Water Drops in Organic Media in Presence of Ionic Surfactants and Salts

Binary coalescence of water drops in o‐xylene and toluene, and ethylene glycol drops in toluene were studied in this work. The effects of cationic and anionic surfactants on coalescence time were studied. Cetyl trimethyl ammonium bromide (CTAB) and cetyl pyridinium bromide (CPyBr) were used as cationic surfactants. Sodium dodecyl benzene sulfonate (SDBS) was used as the anionic surfactant. The effects of salts (NaCl and CaCl2) containing monovalent and divalent ions on coalescence were investigated. The coalescence time was found to follow distributions in each of these experiments. The minimum and maximum values of the distributions were largely different. The stochastic model developed earlier by us was used to fit the distributions. The effects of the physical properties of the system (such as density, size of the drops, interfacial tension, and surface excess of adsorbed surfactant) on the model parameters were discussed.

Cationic surfactant adsorption in the presence of divalent ions

The effect of divalent sulphate SO 4 2− anions and monovalent hydrosulphate HSO 4 − anions, which are simultaneously present in solution due to dissociation equilibrium, on the surface tension of cethyltrimethyl ammonium salts C 16TABr (CTABr) and C 16TAHSO 4 (CTAHSO 4), was investigated. The surface tension was determined by the pendant drop-shape analysis method. The previously proposed “surface quasi two-dimensional electrolyte” (STDE) model of ionic surfactant adsorption, based on the assumption that the surfactant ions and counterions can undergo non-equivalent adsorption within the Stern at layer at air/solution interface, was extended for the description the adsorption of ionic surfactants in presence of multivalent electrolytes. The results indicate that a very good description of experimental data by the developed model can be achieved. They show that monovalent anions like Br −, Cl − or HSO 4 − ions decrease more effectively the surface tension of investigated surfactant than SO 4 2− ions if the solutions of the same ionic strength are compared. That can be explained in terms of low ability of divalent SO 4 2− ions to penetrate the surface layer due to their strong hydration. The ability to decrease the surface tension of cationic surfactants by SO 4 2− follow the place taken by this anion in the Hofmeister series.

Large-Scale Hierarchical Self-Assembly Structures from Gold Nanoparticles

ABSTRACTMetallic nanoparticles may form hierarchical dendrites in the presence of ionic surfactant through self-assembly upon solvent drying at room temperature. With nanoparticle density varying in the drying area on the supporting solid substrate, the morphology and relevant size of the dendrites evolve in different structures. At the region where the nanoparticle density is high, the large dendrite can develop with manifest crystal symmetry. At the low density region, many small sizes of compact crystals can be found, indicating that particle nucleation dominates over the long-range crystal growth. SEM image reveals the ordered stacking of gold nanoplates over the long dendrite branches, resembling the liquid crystal array. We present the possible physical origins to explain the various structures of the assembled dendrites during the solvent evaporation at the interface of solid and air.

Effect of Ionic Strength on Oil Removal from Stainless Steel in the Presence of Ionic Surfactant

Contact angles of oil droplets on solid surfaces provide useful insight into surfactant cleaning behavior. Contact angles of hexadecane and MAR‐TEMP® 355, an industrial quench oil, on stainless steel were measured for ionic surfactant solutions as a function of ionic strength. The ionic strength of sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) solutions was modified by the addition of sodium chloride. Increases in the contact angle with additions of 1.0 mM and 2.5 mM NaCl were observed for the two oils in SDS and for hexadecane in CTAB. For the industrial quench oil, detachment occurred in CTAB concentrations above the critical micelle concentration; as a result, the equilibrium contact angle measurements were not measured. The critical concentration of CTAB decreased with increasing NaCl concentration. Oil‐removal studies indicate that increasing ionic strength by as little as 2.5 mM can result in improved cleaning. A theoretical insight previously used to explain contact‐angle behavior for a hexadecane‐gold system is used to describe the results obtained with the current system. Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.

Coalescence of Air Bubbles in Aqueous Solutions of Ionic Surfactants in Presence of Inorganic Salt

This work presents a study on adsorption characteristics of two anionic (SDS and SDBS) and one cationic (CTAB) surfactants at air–water interface in presence of inorganic salt (NaCl). Coalescence of air bubbles in these solutions is studied by measuring the rest time of air bubbles at flat air–water interface. Significant effects of salt on surface tension and coalescence are observed. Surface tension is reduced in presence of salt and rest time is increased. The stochastic model developed earlier by Ghosh and Juvekar (2002; Chem Eng Res Des, 80: 715–728) fits the rest time distributions very well. A comparison of seven film-drainage models with the mean values of these distributions is presented. It is observed that these models, within the limitations of the simplifying assumptions behind their development, can not predict the values of rest time accurately.

Physicochemical Behavior of Mixed Nonionic‐Ionic Surfactants in Water and Aqueous Salt Solutions

Cloud point, viscosity, and ultrasonic velocity of aqueous solutions of nonionic surfactants (Triton X‐114 and Triton X‐100) in the presence of ionic surfactants (anionic: sodium alkyl sulfate and cationic: alkytrimethylammonium bromides) are reported. The addition of ionic surfactant (at concentrations much less than CMC) to the salt‐free solution of nonionic surfactants increases the cloud point of nonionic surfactants. Such cloud point increase was dependant on the type and hydrophobic tail of surfactants and has been explained in terms of mixed micelles formation. However, in the presence of NaCl (≥0.3 M), the cloud point curve shows a deep minimum as a function of anionic surfactant concentrations. Such minima were not observed in lower concentrations of NaCl in the case of anionic surfactants and in the presence of cationic surfactants. It was seen that the stronger effect was obtained for anionic surfactant. The relative viscosity of this system increased markedly with the variation of the concentration of NaCl, which may be due to shape transition of the micelles. The relative sound velocity results are found to be in agreement with the viscosity results.