Surfactant Concentration Ratio Research Articles

Dodecyltrimethylammonium bromide-styrene microemulsion dielectric investigation in aqueous media

In this paper, we report the complex permittivity of aqueous microemulsions of N-dodecyltrimethylammonium bromide and styrene. The studies were carried out at 298.15 K while varying the styrene to surfactant concentration ratio, S0 (0.16 ≤ S0 ≤ 0.71) and the surfactant concentration, c (0.1032 ≤ c (mol·dm−3) ≤ 0.7806). The frequencies ranged from 100 MHz to 89 GHz. An analysis of a particular solution is conducted over the temperature range of 278.15–328.15 K to calculate the energy of the activation parameters. At 298.15 K, the spectra are fitted to a total of five Debye processes for concentration dependency series and three Debye processes for temperature dependence series. Br− surface and bulk diffusion surrounding the micelles best describes the two low-frequency dispersions, at 100 MHz and 0.8 GHz, respectively. These mechanisms were examined using Grosse theory. The Maxwell–Wagner relaxation process is equivalent to high-frequency micelle dispersion at 0.8 GHz. The thickness of the conducting shell of the micelle is determined by using the electrical conductivity of the particles and parameters taken from the Grosse theory, and the results are comparable to those from an examination of the Pauly and Schwan model. The Grosse model and solvent dispersion analysis were used to calculate the volume fractions of micelles. Both approaches were in agreement. The surfactant head group non-rotationally hydrates almost ∼7 ± 1 water molecules. Styrene addition allows for the non-rotationally bound accommodation of an additional ∼7 ± 1 water molecules.

Formulation and Evaluation of Multiple Emulation of Diclofenac Sodium

Abstract: Multiple emulsion is novel approach of drug delivery system for enhancement of bioavailability and pharmacological activity. It is important to prevent the problem of oral drugdelivery system and they are stabilized by using of combination of hydrophilic and lipophilic surfactant. The specific ratio of surfactant concentration is responsible for maintaining the stability of multiple emulsions, the importance of this study was to prepare multiple emulsion of Diclofenac sodium by using two step emulsification process, by using the non-ionic surfactant units. In multiple emulsion, the stability of multiple emulsion was evaluated, percent entrapment efficiency as well as in vitro studies are conducted. The objective of this study was to prepare multiple emulsion of Valsartan by two step emulsification using different nonionic surfactants, Tweens & Spans, and evaluate for stability,percentage drug entrapment, in vitro drug release.

Anisotropic growth of photoreduced silver nanostructures using surfactant-assisted ferroelectric templates for surface enhanced Raman spectroscopy

Photoreduction using ferroelectric templates is an emerging green technique for the production of noble-metal nanostructures by a reductant-free process. In this work, anisotropic growth of silver nanostructures is stimulated by a surfactant-assisted photoreduction process on ferroelectric templates. The preferential adsorption of surfactant (polyvinylpyrrolidone) on the specific facets of silver creates the anisotropic growth of nanostructures and thus the formation of silver nanoplates. The surfactant adsorption effects on the nanoparticle morphology and the nanoparticle properties are studied. Their influence levels depend on the ratio of surfactant concentration to precursor concentration. The produced silver nanostructures have superior SERS features, such as the limit of detection of <10−8 M, the enhancement factor of 2.2 × 109 and Raman intensity enhancement by 8.71 times. The study of anisotropic growth of photoreduced nanoparticles using ferroelectric templates provides a promising prospect to develop green production techniques for versatile anisotropic nanoparticles.

Breakup characteristics of aqueous droplet with surfactant in oil under direct current electric field

The breakup process of aqueous droplet with surfactant suspended in oil under direct current (DC) electric field is investigated in this paper. The characteristics of the breakup process, stretching, necking and breakup, are discussed quantitatively with the electric capillary number Ca and the dimensionless surfactant concentration C∗ which is the ratio of surfactant concentration to the critical micelle concentration. The results show that the presence of surfactant reduces the steady deformation of droplet and significantly decelerates the stretching process, resulting from the redistribution of surfactant molecules within the oil/water interface. The law of droplet stretching process when C∗≥1 indicates that the exchange of surfactant molecules between the bulk phase and the interface could not catch up with the increase of oil/water interfacial area. Ca and C∗ count a great deal to the necking position and the daughter droplet size. The daughter droplet size decreases with the increase of surfactant concentration. These results provide a mechanistic framework to promote the electrocoalescence efficiency of oil/water emulsion and to the application of electric emulsification.

Surfactant removal with multiwalled carbon nanotubes

The ability of multiwalled carbon nanotubes (MWCNTs) to remove a non-ionic surfactant, Triton X-100 (TX100), an anionic surfactant, sodium dodecylbenzenesulonate (SDBS), and a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB) from the aqueous phase was investigated. Untreated, OH-, and COOH-functionalized MWCNTs with different outer diameters and chemical composition were examined and compared. As both the concentrations of surfactants and MWCNTs initially added may affect removal efficiency of surfactants, a relationship between the initial concentration ratio of surfactants and MWCNTs (Rc) and the removal efficiency (E) was established. The results showed that for a given Rc (e.g., 0.8), removal efficiency of the tested surfactants by a specific MWCNT (e.g., the untreated one with outer diameter <8 nm) decreased in the following order: TX100 (52.3%) > SDBS (26.2%) > CTAB (3.8%). TX100 was more readily removed by MWCNTs than SDBS and CTAB, due to its longer aliphatic chain compared to SDBS and CTAB thus higher hydrophobicity, and stronger π-π interactions with the aromatic structure of the surfaces of graphite sheets relative to CTAB. Based upon the established relationship between Rc and E of surfactants by MWCNTs, the maximum removal efficiency and the most appropriate Rc of TX100 and SDBS by two MWCNTs (UT8 and OH8) were derived. It was interesting to notice that, except for the case to remove TX100 using UT8, even though a large quantity of UT8 or OH8 was added to the TX100 or SDBS removal systems, they cannot be completely removed, with the maximum removal efficiency in the range of 55.88–87.17%. This mostly resulted from strong aggregation of MWCNTs thus reducing their readily accessible surface area and porosity for sorption.

Synergistic Effect on Wettability of Mixtures of Amine Oxides, Alkylpolyglucosides, and Ethoxylated Fatty Alcohols

AbstractThe mixture proportions of three surfactants, i.e. an alkylpolyglucoside (APG), an ethoxylated fatty alcohol, and an amine oxide (AO), were optimized by applying Response Surface Methodology in order to achieve the surfactant ratio that produces the highest wetting power. The synergistic effect of the binary samples of AO with the other surfactants was firstly verified. An improvement in this synergistic effect on wettability was found in the ternary mixture. In the experimental range analyzed, the surfactant concentration ratio that produced the highest wettability was a composition with 19.3 % APG, 30.1 % ethoxylated alcohol, and 50.6 % lauramine oxide.

Flux decline analysis in micellar-enhanced ultrafiltration of synthetic waste solutions for metal removal

It is known that micellar-enhanced ultrafiltration (MEUF) is an efficient and economic process for the removal of trace metal ions and organics from aqueous media. In this work, flux decline behavior in MEUF of aqueous solutions containing trace Cu(II) (1.6–8 mM) and anionic surfactants sodium dodecyl sulfate (SDS) or sodium dodecyl benzene sulfate (SDBS) was studied at 25 °C in batch mode. An UF membrane that had average pore size comparable to those of Cu(II)-adsorbed micelles was adopted. All experiments were performed as a function of stirring speed (200–400 rpm), solution pH (3.0–5.0), molar concentration ratio of surfactant to metal (S/M, 2.5–12.7), and applied pressure (69–345 kPa). It was shown that more than 90% of Cu(II) could be removed at an S/M ratio of 12.7 and pH 5 using SDS. The blocking filtration law was used to identify the mechanism(s) of flux decline during the MEUF processes. Finally, the specific cake resistances in both SDS and SDBS systems were evaluated and compared.

Magneto-dielectric properties of polymer– [formula omitted] nanocomposites

The aim of this research is to elucidate the size effect of magnetic nanoparticles on the resultant magneto-dielectric properties of polymer nanocomposites at radio frequencies. The block copolymer of [styrene-b-ethylene/butylene-b-styrene] (SEBS) was utilized as a matrix for the templating of magnetic nanoparticles. Surfactant-modified iron oxide ( Fe 3 O 4 ) nanoparticles of various sizes were successfully synthesized by a seed-mediated growth method. The surfactant prevented Fe 3 O 4 aggregation and provided compatibility with the polymer matrix. The nucleation and growth of Fe 3 O 4 nanoparticles was controlled by changing the concentration ratio of surfactant to iron-precursor. The free iron ions present during synthesis are the major factor contributing to the growth of larger particles. The Fe 3 O 4 nanoparticle critical size for superparamagnetic to ferrimagnetic transition was determined to be near 30 nm at room temperature. The dielectric permittivity ( ɛ r ) of the polymer composite increased with increasing amount of Fe 3 O 4 doping, and was not influenced by nanoparticle size. However, the magnetic permeability ( μ r ) of the composites was significantly influenced by the size of Fe 3 O 4 nanoparticles templated within the block copolymer matrix due to thermal energy fluctuations from the nanoparticle surroundings.

The influence of a perfluorinated cationic surfactant on the electrodeposition of tin from a methanesulfonic acid bath

The influence of a perfluorinated, cationic surfactant on the electrodeposition of tin onto a copper surface was investigated. The electrolyte was 0.014 mol dm −3 SnSO 4, 0.005 mol dm −3 hydroquinone and 12.5 vol.% methanesulfonic acid (1.93 mol dm −3 MSA) at 296 K, containing a controlled concentration (0–2.4 vol.%) of DuPont™ ForaFac ® 1098 surfactant, corresponding to a concentration ratio of surfactant to stannous ions of 0–5.6. Cyclic (at static disc electrode) and linear sweep voltammetry (using the rotating disc electrode) were used to characterise the electrodeposition. The effects of potential sweep rate and electrode rotation speed are discussed. The influences of the surfactant on the region of complete mass transport control and hydrogen evolution are investigated. The effect of surfactant addition to the electrolyte was shown to be potential and flow-dependent. The absorption of surfactant on the electrode surface hindered the hydrogen evolution and resulted in a reduction in the peak and limiting current densities. The reduction of dissolved oxygen from the background electrolyte, in the presence or absence of surfactant, was also investigated. The morphology of electrodeposited tin is characterised; in the presence of surfactant, a compact surface morphology whereas rod-like deposits could be obtained at higher current densities.

In situ studies of order–disorder phenomena in the synthesis of mesoporous silica

The initial hydrolysis of a silicon alkoxide in the presence of a suitable structural directing agent (template) so as to form a mesoporous silica powder exhibiting long-range hexagonal ordering was monitored using in situ XRD (X-ray diffraction), SAXS (small angle X-ray scattering) and SANS (small angle neutron scattering). The non-ionic triblock copolymer P123 (EO20PO69EO20) was employed as the organic templating agent and tetramethoxysilane (TMOS) was used as the silica source in the presence of a water/acid catalyst. The synthesis method described herein is based around a high volume concentration ratio of surfactant to TMOS. The formation of a long-range mesoscopically ordered organic–inorganic hybrid that could be subsequently calcined to form a hexagonally structured mesoporous oxide material was monitored over 6 days using the characteristic (100) reflection. It was seen that during this ‘maturation’ period the reaction is not progressive and SANS and SAXS data together with XRD experiments show that there is an initial kinetically rapid organic ordering process which provides a template for the formation of an ordered metastable organic–inorganic oxide phase which then becomes progressively more disordered before a final kinetically slow stable long-range ordered phase is formed. Discussions of the origin of the unexpected order–disorder phenomena are made.

Modulation of Guest Partitioning Within Dendrimer–Surfactant Supramolecular Assemblies

ABSTRACT Electrostatic interactions are used to create a template-assisted supramolecular assembly consisting of a polymeric dendrimer at the core and amphiphilic substrates on the periphery. The dendrimer generation and the chemical structure of the amphiphiles are varied to construct multiple and distinct microenvironments within the dendrimer–ligand complex for encapsulation of small guest molecules. In particular, these investigations employ a guest molecule that is a neutral fluorescent probe that exhibits an emission wavelength with an extreme sensitivity to the polarity of its surroundings. Partitioning of the fluorophore within the various microregions of the dendrimer–surfactant supramolecular complex is distinguished by the characteristic emission wavelengths of the overlapping Gaussian functions comprising the overall fluorescence spectrum. The observed variations in the prodan emission spectrum suggest interaction of prodan at protonated amino groups (460-nm emission), within dendritic branches and surfactant tails (490-nm emission), and in interior regions of the dendrimer core (430-nm emission). We demonstrate that the positioning of the guest molecule within the supramolecular complex can be modulated through the selection of dendrimer generation, surfactant chain length, and dendrimer:surfactant concentration ratio.

Microemulsions in the Didodecyldimethylammonium Sulfate (Bromide)/Hydrocarbon/Water System. Microstructure and Specific Counterion Effects

The microemulsion phase in the didodecyldimethylammonium sulfate/hydrocarbon/water system was investigated with NMR self-diffusion, 2H NMR relaxation, and the time-resolved fluorescence quenching technique. From the NMR self-diffusion experiments, it was found that the diffusion of the surfactant and the hydrocarbon are equal for a certain range of surfactant to oil concentration ratios, indicating that in this range of composition the structure is one of discrete aggregates. Upon an increase of the surfactant to oil volume ratio, there is an onset of a network formation, as indicated by the fact that the surfactant self-diffusion is smaller than that of the hydrocarbon. Close to the lower values of the oil to surfactant concentration ratio for which the microemulsion exists, a bicontinuous micellar network is formed. Phase studies and self-diffusion experiments in mixtures of a microemulsion with normal curvature, that is, with sulfate as counterion, with a microemulsion with reversed curvature, that is,...

Unusual effects of counterion to surfactant concentration ratio on viscoelasticity of a cationic surfactant drag reducer

One-to-one molar ratio sodium salicylate (5 mM)/Arquad S-50 (5 mM) solution was investigated in comparison to the sodium salicylate (12.5 mM)/Arquad S-50 (5 mM) or 2.5:1 solution, which was previously reported to be drag reducing yet non-viscoelastic [9]. Results showed a dramatic influence of the counterion to surfactant concentration ratio on the viscoelasticity of the surfactant drag reducing systems. The 1:1 solution has normal surfactant drag reducer characteristics such as viscoelastic properties and thread-like micellar networks and branches. This is the first cationic surfactant/counterion drag reducing system found, for which excess counterion makes the solution non-viscoelastic, while the microstructure of thread-like micellar networks is apparently unchanged.

Response of fluoranthene-degrading bacteria to surfactants

A prerequisite for surfactant-enhanced biodegradation is that the microorganisms survive, take up substrate and degrade it in the presence of the surfactant. Two Mycobacterium and two Sphingomonas strains, degrading fluoranthene, were investigated for their sensitivity towards non-ionic chemical surfactants. The effect of Triton X-100 and Tween 80 above their critical micelle concentration on mineralization of [14C]-glucose and [14C]-fluoranthene was measured in shaker cultures. Tween 80 had no toxic effect on any of the tested strains. The surfactant inhibited fluoranthene mineralization by the hydrophobic Mycobacterium spp. slightly, but more than doubled that by the two less hydrophobic Sphingomonas strains. Triton X-100 inhibited fluoranthene mineralization by all strains, yet this was more pronounced for the Sphingomonas spp. Both surfactants caused cell wall permeabilization, as shown by transient colouring of surfactant-containing media. Inhibition of glucose mineralization, indicating non-specific toxic effects of Triton X-100, was observed only for the Sphingomonas strains and the toxicity was caused by micelle-to-cell interactions. These strains, however, appeared to recover from initial Triton X-100 toxicity within 50–500 h of exposure. The ratio of surfactant concentration to initial cell density was found to determine critically the bacterial response to surfactants. For both Sphingomonas and Mycobacterium strains, this work indicates that fluoranthene solubilized in surfactant micelles is only partially available for mineralization by the bacteria tested. However, our results suggest that optimal conditions for polycyclic aromatic hydrocarbon mineralization can be developed by selection of the proper surfactant, bacterial strains, cell density and incubation conditions.

Deactivation and conformational changes of cutinase in reverse micelles

Deactivation data and fluorescence intensity changes were used to probe functional and structural stability of cutinase in reverse micelles. A fast deactivation of cutinase in anionic (AOT) reverse micelles occurs due to a reversible denaturation process. The deactivation and denaturation of cutinase is slower in small cationic (CTAB/1-hexanol) reverse micelles and does not occur when the size of the cationic reverse micellar water-pool is larger than cutinase. In both systems, activity loss and denaturation are coupled processes showing the same trend with time. Denaturation is probably caused by the interaction between the enzyme and the surfactant interface of the reversed micelle. When the size of the empty reversed micelle water-pool is smaller than cutinase (at W0 5, with W0 being the water:surfactant concentration ratio) a three-state model describes denaturation and deactivation with an intermediate conformational state existing on the path from native to denaturated cutinase. This intermediate was clearly detected by an increase in activity and shows only minor conformational changes relative to the native state. At W0 20, the size of the empty water-pool was larger than cutinase and the data was well described by a two-state model for both anionic and cationic reverse micelles. For AOT reverse micelles at W0 20, the intermediate state became a transient state and the deactivation and denaturation were described by a two-state model in which only native and denaturated cutinase were present. For CTAB/1-hexanol reverse micelles at W0 20, the native cutinase was in equilibrium with an intermediate state, which did not suffer denaturation. 1-Hexanol showed a stabilizing effect on cutinase in reverse micelles, contributing to the higher stabilities observed in the cationic CTAB/1-hexanol reverse micelles. Copyright 1998 John Wiley & Sons, Inc.

Deactivation and conformational changes of cutinase in reverse micelles

Deactivation data and fluorescence intensity changes were used to probe functional and structural stability of cutinase in reverse micelles. A fast deactivation of cutinase in anionic (AOT) reverse micelles occurs due to a reversible denaturation process. The deactivation and denaturation of cutinase is slower in small cationic (CTAB/1-hexanol) reverse micelles and does not occur when the size of the cationic reverse micellar water-pool is larger than cutinase. In both systems, activity loss and denaturation are coupled processes showing the same trend with time. Denaturation is probably caused by the interaction between the enzyme and the surfactant interface of the reversed micelle. When the size of the empty reversed micelle water-pool is smaller than cutinase (at W0 5, with W0 being the water:surfactant concentration ratio) a three-state model describes denaturation and deactivation with an intermediate conformational state existing on the path from native to denaturated cutinase. This intermediate was clearly detected by an increase in activity and shows only minor conformational changes relative to the native state. At W0 20, the size of the empty water-pool was larger than cutinase and the data was well described by a two-state model for both anionic and cationic reverse micelles. For AOT reverse micelles at W0 20, the intermediate state became a transient state and the deactivation and denaturation were described by a two-state model in which only native and denaturated cutinase were present. For CTAB/1-hexanol reverse micelles at W0 20, the native cutinase was in equilibrium with an intermediate state, which did not suffer denaturation. 1-Hexanol showed a stabilizing effect on cutinase in reverse micelles, contributing to the higher stabilities observed in the cationic CTAB/1-hexanol reverse micelles. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:380–386, 1998.

Causes and remediation of reduced efficiency in micellar liquid chromatography

Broad peaks are obtained when purely aqueous micellar phases are used in micellar liquid chromatography (MLC). The causes of reduced efficiency in MLC are investigated. Slow solute mass-transfer kinetics between micelles, the aqueous phase and the surfactant covered stationary phase are the origins of the efficiency loss. Knox plots show that the reduced efficiency comes from A term increase and, for lipophilic solutes, A and C terms increases. Surfactant adsorption reduces the pore volume and surface area of the stationary phase changing the flow anisotropy (A term). The surfactant adsorbed layer slows down the mass transfer (C term). Three ways for efficiency loss remediation are known: flow-rate reduction, temperature increase and alcohol addition. Alcohols are known to change the micelle structure and to increase the kinetics of micelle formation-destruction. It is shown that the ratio of the alcohol chain length to surfactant alkyl chain length, Cn, OH/Cnm surf, should be equal or higher than 13 to produce the best efficiency enhancements in MLC. Also, the volume of alcohol to be added is not absolute but relative to the surfactant concentration. The alcohol to surfactant concentration ratio should be kept constant. Temperature increases and especially alcohol additions reduce the retention factors. Thermodynamic and kinetics of the micellar exchanges in MLC cannot be dissociated.

Sorption of two model alcohol ethoxylate surfactants to sediments

We have examined the sorption of two radiolabeled alcohol ethoxylate surfactants (AE) (C13 alcohols with exactly 3 or 9 moles of ethylene oxide (EO) per mole of alcohol) to natural sediments. Formalin was included in the sediment/surfactant/water mixtures to prevent biodegradation. Four sediments with 0.3 to 2.2 % organic carbon content were used in equilibrium experiments to determine the effect of various sediment properties and EO chain length on the sorption process. The equilibrium sorption isotherms were determined to be non-linear and described by the Freundlich model, and distribution ratios (ratio of surfactant concentration on sediment to aqueous concentration) at 1 mg/L surfactant ranged from 110 to 590 L/kg. These distribution ratios indicated that the AEs did not sorb strongly to the tested sediments. The amount of sorption was better correlated to the percent clay content of the sediment than to the percent organic carbon content of the sediment.

Sorption of an alcohol ethoxylate surfactant to natural sediments

AbstractU.S. consumer and industrial use of surfactants results in down the drain disposal and release after treatment in septic fields or sewage plants. Effluent may contain limited concentrations of surfactant, which may remain in receiving waters, and this residual surfactant could become associated with bottom sediments. To assess this phenomenon, we have examined the sorption of a radiolabeled alcohol ethoxylate (C15 alcohol with an average of 9 moles of ethylene oxide per mole of alcohol) to natural sediments under sterile conditions to assure that the surfactant was not biodegraded. Control experiments comparing sterilized systems with systems including 1% formalin indicated that formalin could be included in the sediment/surfactant/water mixture to prevent surfactant biodegradation yet not interfere in the sorption process. Four sediments with 0.3–2.2% organic carbon content were used in this study to determine the effect of various sediment properties on the sorption process. Equilibrium sorption was established in 2–4 h. The equilibrium sorption isotherms were determined to be nonlinear and described by the Freundlich model, and distribution ratios (ratio of surfactant concentration on sediment to aqueous concentration) at 1 mg/L surfactant ranged from 350 to 2,100 L/kg. The amount of sorption was better correlated to the percent clay content of the sediment than to the percent organic carbon content of the sediment.

SORPTION OF AN ALCOHOL ETHOXYLATE SURFACTANT TO NATURAL SEDIMENTS

U.S. consumer and industrial use of surfactants results in down the drain disposal and release after treatment in septic fields or sewage plants. Effluent may contain limited concentrations of surfactant, which may remain in receiving waters, and this residual surfactant could become associated with bottom sediments. To assess this phenomenon, we have examined the sorption of a radiolabeled alcohol ethoxylate (C15 alcohol with an average of 9 moles of ethylene oxide per mole of alcohol) to natural sediments under sterile conditions to assure that the surfactant was not biodegraded. Control experiments comparing sterilized systems with systems including 1% formalin indicated that formalin could be included in the sediment/surfactant/water mixture to prevent surfactant biodegradation yet not interfere in the sorption process. Four sediments with 0.3–2.2% organic carbon content were used in this study to determine the effect of various sediment properties on the sorption process. Equilibrium sorption was established in 2–4 h. The equilibrium sorption isotherms were determined to be nonlinear and described by the Freundlich model, and distribution ratios (ratio of surfactant concentration on sediment to aqueous concentration) at 1 mg/L surfactant ranged from 350 to 2,100 L/kg. The amount of sorption was better correlated to the percent clay content of the sediment than to the percent organic carbon content of the sediment.