Surfactant Fraction Research Articles

Asphalt emulsion formulation: State of the art of formulation, properties and results of HIPR emulsions

Abstract As a way to make pavements more economic, less polluting, and with lower energy consumption bitumen emulsions can be used. The formulation of bitumen emulsions is a complex task and they are usually produced using colloid mills. This method presents several limitations; the maximum bitumen concentration of the dispersed phase, 69%, being the most significant. The HIPR (High Internal Phase Ratio) method must be used for higher bitumen concentrations. With this second method, apart from it being possible to obtain concentrated emulsions, with a volume fraction higher than 70%, it is possible to control the distribution and average droplet diameter of the emulsion. This control is achieved by changing variables such as the volume fraction, the concentration and type of surfactant and the temperature of the dispersed phase, the type of bitumen used, and mechanical variables such as the rotational speed and time employed. The current study aims to review the state-of-the-art of the manufacture of bitumen in water emulsions, with a special emphasis on the concentrated bitumen emulsions manufactured following the HIPR method.

Вплив рН і йонної сили розчину на колоїдно-хімічні властивості бінарних сумішей поверхнево-активних речовин

Досліджено вплив рН і йонної сили розчину на міцелоутворення і адсорбцію бінарних сумішей гексадецилпіридиній броміду (ГДПБ) і тритону Х-100 (ТХ-100.).З використанням моделі фазового поділу (підхід Рубіна-Розена) розраховані склад змішаних міцел і адсорбційних шарів, параметри взаємодії в міцелах β m і адсорбційних шарах β σ , а також надлишкові вільні енергії міцелоутворення та адсорбції. Розрахунки складу змішаних адсорбційних шарів показали, що адсорбційний шар на межі розділу розчин – повітря у всьому інтервалі досліджених об'ємних співвідношень збагачений молекулами нейонної поверхнево-активної речовини (ПАР), що має вищу поверхневу активність. Встановлено, що збільшення йонної сили розчину призводить до зниження сили взаємодій ПАР в змішаному адсорбційному шарі. Це підтверджує електростатичну природу взаємодій у сумішах катіонних і нейонних ПАР. Ключові слова : поверхнево-активні речовини, адсорбція, бінарні суміші, міцелоутворення, адсорбційний шар

Online monitoring and mass transfer modelling of the growth of Ni‐B nanoparticles in a reverse micelle system

AbstractThe growth of Ni‐B nanoparticles by chemical reduction of nickel acetate tetrahydrate (0.3M) using sodium borohydride (B/Ni = 2.5 molar ratio) in CTAB/n‐hexanol/water ternary reverse micelles was investigated. SEM studies showed that the synthesized nanoparticles within the reverse micelle range are more favourable in terms of microstructure and morphology. Nanoparticle growth has been controlled in the range of 0.83–5.59 nm · h−1 by the precise adjustment of mass fraction of surfactant in the oil phase (0.22–0.47 wt%) and the overall mass fraction of the aqueous phase (0.1–0.3 wt%) values. Particle growth was measured in situ using time resolved UV‐vis absorbance spectroscopy. In addition, a new correlation based on characteristic absorbance peaks of Ni‐B nanoparticles at wavelengths of 285 and 230 nm has been derived for this purpose. An accuracy of about 9 % on the nanoparticle average sizes with respect to sizes measured by dynamic light scattering (DLS) was found (R2 = 0.98). A diffusion controlled growth model involving effective diffusivity of reverse micelles (Deff − RM = 9.60 × 10−11 − 1.17 × 10−8 m2 · s−1) andripening parameter (K = 4.57 × 10−21 − 1.54 × 10−20 m2 · s−1) was developed to describe the growth behaviour of the nanoparticles. The experimental results were very close to the experimental results with slight errors (7–10 %). Finally, TEM micrographs of Ni‐B nanoparticles showed that particle growth as well as agglomeration can be effectively controlled by precise adjustment of each component in the reverse micelle technique.

Lightweight structural eco-mortars made with polyurethane wastes and non-Ionic surfactants

The properties of structural lightweight mortars obtained with recovered foam polyurethane wastes have been studied, containing a low fraction of soluble non-ionic surfactant. The characterisation of mechanical properties, bulk density, microstructure and porosity highlights two types of behaviour according to the composition (e.g. hydrolysis grade) of the non-ionic surfactants. By using additives with low hydrophilic–lipophilic balance (HLB) values, the lightweight mortars show more and more high mechanical properties according to the increase of the substitution rate of sand by PU wastes. These non-ionic surfactants seem to promote a homogeneous microstructure and improve the adhesion between PU wastes and cement paste. On the other hand, the mortars mixed with additives showing high HLB values, are more lightweight and macroporous, due to the increase of air entrained driven by the substitution rate of sand by PU wastes.

Ultrasonication assisted formation and stability of water-in-oil nanoemulsions: Optimization and ternary diagram analysis

An energy efficient and scalable method designed to form stable and transparent water-in-oil (W/O) nanoemulsion can be attained by optimization of process parameters and study of ternary diagram. Application of high energy in addition to the low energy at the optimized conditions have been targeted to make the process energy efficient, since later part is applied to droplets formed at less energy. In the present work, formation of combined energy mixed surfactant nanoemulsion was achieved by combined approach of isothermal low energy followed by ultrasonication that could be used as a fuel in compression ignition engine free from NOx and particulate matter emissions. A mixture of two functional groups (ether and ester) non-ionic surfactants was used at optimized ratio of 0.71/0.29 (Span 80/TX-100; w/w). Optimization of ultrasonicated parameters resulted in 25% amplitude, 0.5 pulse mode factor and 8.5 min of sonication time. A ternary diagram study was performed to recognize the compositions accountable for the formation of transparent, translucent and opaque emulsions in the bounded range of water fraction 0.02 to 0.11 and surfactant fraction 0.10 to 0.20. Surfactant-to-water (β) ratio found applicable for the production of nano-sized droplets in the range of 2 ≤ β ≤ 3. A minimum droplet size of 25 ± 1 nm was attained in the present study. An increase in surfactant fraction decreased average droplet size, whereas, increase in water fraction increased average droplet size. Reduction in droplet size was prominently found in the range of energy density from 15.23 J.ml−1 to 40 J.ml−1 thereafter, it decelerated up to 160 J.ml−1. Prediction of average droplet size modeled with energy density fitted well and could be used for scaling up and tuning the droplet size. Resultant nanoemulsion samples displayed kinetic stability whereas long term stability (45 days) assessed using Ostwald ripening model showed stability in the order of β = 2.0 > β = 2.5 > β = 3.0 > β = 4.0.

Study on Variation of Physicochemical Parameters of the Polymer/Surfactant Binary Multisystem in Porous Media

The sulfonate Gemini surfactant and hydrophobic associating polymers were prepared with different ratio in multisystem, and we measured viscosity and interfacial tension of the solution before pour it into the core. The multisystem with different ratio was poured into the core, we measured the produced liquid viscosity, interfacial tension, the concentration of polymer and surfactant at core outlet with different injection stage and at different locations after stable, calculated the dynamic adsorption capacity of the binary multisystem, and measured the static adsorption capacity of binary multisystem with different ratio on natural oil sand in Suizhong 36-1 Oilfield. Experimental results show that the stable viscosity of the produced liquid of multisystem increased with increase of polymer concentration, and decreased with the increase of the distance flowed through the core, and these changes concentrated on the first 1/3 of core; the interfacial tension decreased with the increase of mass fraction of surfactant, the stable interfacial tension value after passed through the core was about 7-10 times before solution injected; Multisystem has the chromatographic fractionation in rock.

Modulating the interfacial concentration of gallates to improve the oxidative stability of fish oil-in-water emulsions

Distributions of a homologous series of gallic acid (GA) derivatives of increasing lipophilicity were determined in stripped fish oil-in-water emulsions. The distribution was determined by employing a kinetic method based on the reaction between the hydrophobic 4-hexadecylbenzenediazonium ions (16-ArN2+) and the antioxidants (AOs), that allows to determine the partition constants between the oil-interfacial, POI, and water-interfacial, PWI, regions of the emulsion. Results showed that the antioxidant activity of gallic acid and its derivatives was positively correlated with the percentage of AO at the interface. The percentage of butyl, octyl and dodecyl gallates in the interfacial region is similar but much higher than that of the other derivatives, showing the highest AO efficiency. When increasing the surfactant fraction, the percentage of all compounds at the interface increased but the emulsion stability decreased due to the dilution of AO at the interface region. Both butyl and octyl gallates were found the most suitable AOs to carry out fish oil-in-water emulsions protection. For maximum effectiveness, butyl and octyl gallate should be used with the lowest emulsifier volume fraction necessary to physically stabilize emulsions.

Association of imidazolium surfactants with poly(N-isopropylacrylamide)

Most investigations about polymer and surfactant interactions are related to standard surfactants, while the scope of literature using imidazolium surfactants is limited. In this work, conductometric and calorimetric techniques have been combined to determine the interaction of poly(N-isopropylacrylamide) with two surfactants: 1-tetradecyl-3-methylimidazolium chloride and 1-hexadecyl-3-methylimidazolium chloride. The critical aggregation concentration and the polymer saturation point have been determined as a function of the polymer concentration. To explain the conductivity results, a new model has been proposed that considers the possibility of formation of free micelles before the polymer saturation. This model allows estimating the fraction of surfactant molecules aggregated to the polymer and the ionization degree of them, as well as the fraction of surfactant in the form of free micelles. Isothermal titration calorimetry results reveal that the interaction between the polymer and both surfactants is driven by entropic processes and that the aggregation process is non-cooperative at the initial stages.

Analysis and optimization of water-based printing ink formulations for polyethylene films

Water-based ink formulations containing wax, surfactant, and defoamer additives were prepared and printed on polyethylene film substrates. Standard test methods for adhesion, rub resistance, and gloss were done on the printed polyethylene films. Quantitative methods for the assessment and evaluation of the three print properties were developed. Image analyses were done to quantify adhesion and rub resistance. Quantitative measurement was done to quantify gloss. Data were analyzed using mixture design modelling and optimization. Modelling results show that adhesion and gloss are described by special cubic model equations, while rub resistance is described by a linear model equation. Contour plots and 3D surface graphs were generated showing the response surfaces of the print properties. The effects of varying the mass fractions of wax, surfactant, and defoamer on adhesion, rub resistance, and gloss were determined. It was found that increasing wax increases rub resistance, while increasing surfactant increases gloss, and increasing defoamer increases adhesion. There is dependency found between the mass fraction of wax, surfactant and defoamer with respect to the rub resistance, adhesion and gloss. Multi-objective optimization revealed that optimum adhesion, rub resistance, and gloss is obtained by a formulation containing equal mass fractions of wax and surfactant but no defoamer.

Physicochemical Investigation on the Pulmonary Surfactant of Some Vertebrates

<p>Large aggregate (LA) fraction of the pulmonary surfactant (PS) isolated from five different animals of the vertebrate group, lungfish, chicken, crocodile, stumpie lizard and guinea pig were isolated and characterized. Active pulmonary surfactant components were obtained by chloroform-methanol extraction of the saline suspended LA fraction. Total phospholipid (PL) and protein content were estimated biochemically by standard enzymatic methods. A systematic progression in the PL and protein content was noticed with the developmental sequence of the animals, except the crocodile, which could be due to the difficulty in the PS isolation procedure. <em>In vitro</em> functionality of the solvent spread film was carried out in a Langmuir surface balance by way of surface pressure (π)-area (A) measurements. PS from all the species exhibited reversible compression and expansion cycles. A clear correlation between the maximum attainable surface pressure (π<sub>max</sub>), also known as the collapse pressure (π<sub>c</sub>) and the developmental sequence, with some exceptions, could have been established. Langmuir-Blodgett deposits, transferred onto freshly cleaved mica, were imaged by atomic force microscopy for the five different species. DPPC enriched domains showed different dimensions for the five different species. The comprehensive set of studies shed light on the composition, film functionality and structure of the pulmonary surfactants of the vertebrates where a correlation with the evolution sequence is observed.</p>

Recovery of phenolic compounds from wastewaters through micellar enhanced ultrafiltration

In this research work, the efficiency of Micellar Enhanced Ultrafiltration (MEUF) was evaluated for recovery of polyphenols from aqueous solution, using three surfactants, namely Esterquat, Dodecylbenzenesulfonic acid sodium (DBSS) and Lutensol AO 7 (cationic, anionic and non-ionic surfactants, respectively). Firstly, the critical micellar concentration (CMC) was experimentally determined for each surfactant. CMC values of DBSS was almost 4 orders of magnitude higher than Esterquat and around 200 orders higher than Lutensol A07, indicating the high efficiency of micellization for Esterquat and Lutensol A07. On the other hand, the effect on the polyphenols retention percentage of several factors in the practical application of MEUF was investigated including transmembrane pressure, nature of surfactant, feed surfactant concentration, mole fraction of non-ionic surfactant as well as initial pH value. Results showed that the permeate flux increased with increasing transmembrane pressure. It was concluded that the highest retention efficiency was obtained for the cationic surfactant during the first filtration minutes (higher than 90%). Moreover, the surfactant concentration of 5 CMC gives the best rejection percentage. There was no significant improvement with addition of non-ionic surfactant. Regarding the influence of initial pH, polyphenols rejection percentage slightly increased with an increase in the pH up to a value equal to 3 (from 93 to 95%), but higher pH values resulted in lower polyphenols retention percentage. The results demonstrate the high efficiency of MEUF system under optimal conditions for the treatment of polyphenols-contaminated wastewaters and for the concentration and recovery of these phenolic compounds.

Modulation of Polyelectrolyte–Micelle Interactions via Zeta Potentials

The onset of soluble complex formation between polycations and nonionic/anionic mixed micelles was found to occur at well-defined micelle surface charge density, σc, which could be modulated via Y, the mole fraction of anionic surfactant in the mixed micelle. Critical values of Y were detected by precision turbidimetry for two polycations, each combined with any of the four mixed micelles formed from two anionic and two nonionic surfactants. The values of Yc observed for each of the resultant eight ternary polycation/anionic–nonionic combinations were used as surrogates for polycation binding affinity: for a given polycation and a given value of Y, micelles with Yc Y will not. The polycation affinity of micelles correlated with their “zeta potentials” (ζ), measured by electrophoretic light scattering, and their average surface potentials (ψ0), measured by potentiometric titration of a comicellized probe. For a given polycation at a fixed ionic strength, we found that t...

Mixed micellization study of ibuprofen (sodium salt) and cationic surfactant (conventional as well as gemini)

AbstractHerein, we have studied the interaction between cationic surfactant (conventional [myristyltrimethylammonium bromide, MTAB] as well as gemini surfactant 1, 4‐butanediyl‐α, ω‐bis(dimethyltetradecylammonium bromide) (14‐4‐14)) and anti‐inflammatory sodium salt of ibuprofen (IBU) drug in aqueous solutions by using tensiometry method at 298.15 K. The means of the interaction of drugs by added foreign materials is of paramount importance in the drug delivery. Ibuprofen is used for the relief of pain, fever, and swelling. From this study we have evaluated different parameters, for example, critical micelle concentration (cmc), micellar mole fraction of mixed micelles/mixed interface (X1m/X1σ), micellar/surface interaction parameter (βm/βσ), activity coefficients (f1m/f1σ and f2m/f2σ) of the mixed micelles/mixed interface, excess Gibbs free energy of mixed monolayer/mixed micelle formation ( / ), surface excess concentration (Γmax) etc. and discussed in detail. The micellar interaction parameter (βm) was determined from the critical micelle concentration values of the pure surfactant (MTAB/14‐4‐14) and IBU (cmc1 and cmc2) and the mixed system (cmc) using the Rubingh's model. In addition to this, various other parameters such as packing parameters of amphiphiles in the micelles (P), volume contribution of the hydrophobic chain (V0), and its effective length (lc), have also been calculated. The value of micellar mole fraction ( ) is found to be more for IBU + 14‐4‐14 mixtures as compared to IBU + MTAB mixtures at lower mole fraction and vice versa at a higher mole fraction of surfactant. The ΔGom and ΔGoads values for all studied systems were found out to be negative, ie, micellization, as well as adsorption processes, are found to be energetically favorable.

Synergistic Interaction between Nonionic Octylphenol Polyoxyethylene Ethers and Effect of Hydrophilic Chain

AbstractThe micellization of binary mixture composed of nonionic octylphenol polyoxyethylene ether (OP‐n, n is the average number of oxyethylene unit) and its homologues, as well as the effect of hydrophilic chain were investigated. The tensiometry was adopted to determine the critical micelle concentration of binary surfactant mixture. According to the regular solution theory, some thermodynamic models were used to predict the parameters of micellization and the thermodynamic parameters. For all the three binary mixtures of nonionic/nonionic surfactants, each of which shows a nonideal mixing and can behave synergistically in aqueous solution. For both the mixture of OP‐10/OP‐7 and the mixture of OP‐10/OP‐4, the positive deviation of the mole fraction of surfactant in mixed micelle from its ideal value coexists with the negative deviation in the entire range of compositions in aqueous solution, while for the mixture of OP‐7/OP‐4, it only shows a positive deviation. Thermodynamic data indicate that for all the three binary surfactant mixtures, the process of micellization is entropically spontaneous, and the change of hydrophilic chain results in the difference in the stability of mixed micelle. The results can be explained by the steric effect, the hydrogen bonding and the hydration. The work helps with understanding the interaction between molecules and properties for some industrial products constituted by nonionic surfactant and its homologues.

Method for controlling mean droplet size in the manufacture of phase inversion bituminous emulsions

The most important factors related to the manufacture of phase inversion bitumen in water emulsions are discussed in this paper. The distribution and average droplet diameter of an emulsion depends on formulation variables such as the volume fraction, the concentration and type of surfactant and the temperature of the dispersed phase employed, the type of bitumen used, and mechanical variables as the rotational speed and time used. The emulsions for this study are prepared according to the High Internal Phase Ratio (HIPR) procedure, which requires that the initial dispersion is conducted with internal phase fractions higher than the critical packing (φ>0.74). The bitumen used in this paper are 15/25, 35/50, 50/70 and 70/100. This procedure allows the manufacture of high concentration emulsions, with a small average droplet size, and narrow particle size distribution. Results show that both the droplet size and the particle size distribution obtained can be controlled by changing the parameters of the formulation. Specially one of the most important parameters to consider in the emulsion formulation if we want to obtain the smallest mean droplet size is the penetration grade bitumen used, such as the results presented in this paper.

Effect of anionic surfactant and temperature on micellization behavior of promethazine hydrochloride drug in absence and presence of urea

The interaction between promethazine hydrochloride (PMH) drug and sodium dodecyl sulfate (NaDS) have been carried out conductometrically at various temperatures and concentration to examine the monomeric as well as micellar phases of aqueous solutions of mixed systems in absence and attendance of urea (NH2CONH2). PMH is belonged to the group of drugs called phenothiazines and is employed to care for allergy symptoms. Urea increases the cmc value because of enhancement in the surface charge of the micelles/mixed micelles. Relevant parameters were evaluated using the various theoretical models for binary mixed systems. The values of micellar mole fraction (X1m) and the ideal micellar mole fraction (X1id) were found to higher than the corresponding mole fraction (α1) of surfactant. The micellar interaction parameters (β), were determined from the critical micelle concentration (cmc) values using the approach of Rubingh's regular solution theory. Clint's model was also used to explain the nonideal behavior of the systems. In presence of urea the interaction between the studied components decreases. The evaluated excess free energy (ΔGexRub) explains the more stability of mixed micelles in comparison to micelles of the pure component; the stability decreases in attendance of urea. Also, activity coefficients (f1 and f2) are always less than unity suggesting non-ideality in the mixed solution. The ΔG0m for all studied systems were found out to be negative i.e., micellization processes are energetically favourable.

Comparative Study to Determine the Biodegradability of Dispersants at Environmentally Relevant Concentrations

ABSTRACTChemical dispersant agents reduce the interfacial tension between oil and water, and increase the surface area to volume ratio of oil droplets thus facilitating the biodegradation of spilled oil. Dispersants are composed of surface active molecules known as surfactants and various commercial products contain Dioctyl Sulfosuccinate (DOSS) as the active surfactant ingredient. Since previous laboratory studies were conducted at oil and dispersant concentrations significantly higher (~0.7 g/L oil with Dispersant to Oil Ratio (DOR) of 1:25) than those typically found in field conditions, experiments were conducted at low levels of oil and dispersant (28 μg/L oil with DOR of 1:25) in order to determine the degradation trends at environmentally relevant concentrations. Experiments were conducted using two crude oils (Alaskan North Slope (ANS) and Endicott) and two dispersant products (Corexit 9500 and Finasol OSR 52) to study the biodegradation of dispersants and dispersed oil and oil alone samples were used as controls. Two oil degrading cultures, isolated from the surface (meso) and deep sea (cryo) of the Gulf of Mexico, were enriched on crude oil at 25 and 5 °C and were used as the inocula. The biodegradation experiments were performed at 5 °C for 56 days and at 25 °C for 48 days using sterile GP2 artificial seawater as the media. The time series concentration of DOSS, the primary surfactant in the dispersants was monitored using LC-MS/MS in addition to the oil concentration which was measured using GC-MS/MS. Although the initial concentration of DOSS in Finasol OSR 52 was 20% higher than in Corexit 9500, over 95% of the anionic surfactant fraction was metabolized for both types of dispersant products by the end of the experiment at 25 °C while it persisted at 5 °C. The effect of dispersant and oil type on microbial community structure was also analyzed using PCR analysis. Results indicated that the abundance of Thalassospira correlated well with hydrocarbon degradation trends. The results from this study significantly expands on our understanding of biodegradation of DOSS, dispersed, and non-dispersed oil and also provides information regarding bacterial community composition.

An experimental investigation of the interfacial tension between liquid-liquid mixtures in the presence of surfactants

The property interfacial tension between liquid-liquid interfaces is a crucial quantity on the study and characterization of emulsion flow rheology. The use of surfactant molecules on a membrane avoids for instance coalescence of the oil droplets by reducing the interfacial tension of the mixture. A transient effect occurs due to the redistribution of the surfactant molecules at the liquid-liquid interface. The present work carries out interfacial tension measurement as a function of the continuous phase components volume fraction which is equivalent to a liquid-liquid interface of different viscosity ratios. The dependence of the interfacial tension on the volume fraction of surfactants is also examined. The experiments are carried out in a drop volume tensiometer, based on the balance between buoyancy and capillary forces on a drop that is detached from the edge of a capillary tube. The interfacial tension between mineral oil drop and a glycerol/water solution is then measured for several values of glycerol volume fractions. The interfacial tension between an oil drop and water is also measured for various concentrations of the Span 80 (i.e. lipophilic surfactant) and Tween 80 (i.e. hydrophilic surfactant). Correlation functions are proposed in order to fit the experimental data. The equilibrium time of the surfactant distribution by the mechanisms of adsorption and by the Marangoni stresses resulting from the flow-induced surface tension gradients on the drop surface and the corresponding equilibrium interfacial tension are used as parameters of the correlations. The results show that the relaxation time for the surfactant distribution reaching steady state decreases with surfactant volume fraction. We determine experimentally the critical value of the surfactant volume fraction and its associated relaxation time. We obtain the minimum surfactant concentration to be used in order to guarantee a faster relaxation of the interfacial tension. The surfactant interfacial properties are estimated and related to their structure.

Functional and Structural Characterization of Pulmonary Surfactant Fractions Obtained from Bronchoalveolar Lavages

The alveolar surface of the lung is protected by a lipophilic material, the pulmonary surfactant, mainly composed by lipids and a few specific proteins: SP-A, SP-B, SP-C and SP-D. The main function of pulmonary surfactant is to reduce the surface tension of the thin aqueous layer covering the alveolar epithelium, avoiding the collapse of the smaller alveoli during the expiration. To achieve this function, surfactant lipids form an interfacial film at the air-liquid interface of this aqueous lining layer. Nevertheless, pulmonary surfactant is synthetized, packed and secreted by type II alveolar pneumocytes as tightly packed membranes assembled in specialized organelles, the lamellar bodies. Currently, the molecular mechanisms that let pulmonary surfactant be transformed from the bilayers of lamellar bodies into the functional interfacial film remain unclear. This is in part because most of the previous studies were made using surfactants obtained from bronchoalveolar lavages, a complex mixture that likely combines freshly secreted surfactant and surfactant that has been already exposed to respiratory dynamics and can be at least partially deactivated. In this work, we have characterized different fractions obtained by density gradient ultracentrifugation of pulmonary surfactant purified from bronchoalveolar lavages of porcine lungs. The analysis of these fractions by transmission electron microscopy showed a heterogeneous mixture of membranous structures. With regard to composition, each fraction showed important differences in cholesterol and the content of surfactant proteins. All fractions presented a relatively good surface activity when analyzed in the captive bubble surfactometer, except for some minority fraction. These results indicate that surfactant from bronchoalveolar lavage is composed by a heterogeneous mixture of membranes differing in composition and structure. We propose that some of these structures could be associated with different stages of surfactant dynamics, including freshly secreted material, interfacial structures and recycled membranes.

Interaction between antidepressant drug and anionic surfactant in low concentration range in aqueous/salt/urea solution: A conductometric and fluorometric study

Abstract Aqueous/salt/urea micellar solutions of amphiphilic antidepressant drug amitriptyline hydrochloride (AMT) and anionic surfactant sodium dodecylbenzenesulfonate (SDBS) have been examined by conductivity and fluorescence measurements at different temperatures and composition. From the conductometric study, values of critical micelle concentration ( cmc ) of drug have been evaluated and analyzed in terms of effect of surfactant on the hydrophobic nature of AMT–SDBS complex. The values of critical micelle concentration ( cmc ) and other aggregation parameters, micellar mole fraction ( X 1 ) and interaction parameters ( β ) were obtained and discussed in detail. In mixtures of AMT and SDBS, the synergistic interactions in mixed micelles formation increases with the raise in mole fraction of surfactant in absence and attendance of salt/urea. Thermodynamic parameters of the mixtures in aqueous as well as in salt/urea solution have been evaluated by means of a pseudo-phase model. The effect of NaCl shows the salting-out effect, which promotes aggregate formation of AMT and SDBS as well as their mixed systems at lower concentration relative to aqueous solution. The micelle aggregation number ( N agg ) of drug increases with the raise in surfactant mole fraction in mixtures. N agg value of individual and mixed amphiphiles rises in the presence of electrolyte while reduces in the occurrence of urea.