Aqueous Solutions Of Sodium Dodecyl Sulfate Research Articles

The Effect of Aniline Hydrochloride Hydrotrope on the Phase Behavior of SDS/Water System

AbstractThe aim of this work was to determine the detailed phase behavior of the sodium dodecyl sulfate/aniline hydrochloride/water system as a function of concentration of sodium dodecyl sulfate (SDS), aniline hydrochloride (AHC) to sodium dodecyl sulfate molar ratio (R = [AHC]/[SDS]) and temperature. Phase behavior information was obtained via polarizing microscopy, differential scanning calorimetry (DSC), cryo‐scanning electron microscopy (Cryo‐SEM) and oscillatory linear rheological measurements with good agreement among these techniques. It is well known that SDS in water forms spherical micelles at concentrations lower than 40 wt% and temperatures above its Krafft temperature (Tk = 16–21 °C). In this region, the SDS/water system exhibits Newtonian rheological behavior, which is characteristic of spherical micellar solutions. The addition of the hydrotrope, aniline hydrochloride, to SDS aqueous solutions produces a viscosity increase in this system as R augments, and a maximum of about five orders of magnitude was found at R = 0.47 for 5 wt% SDS at 20 °C. Moreover, the system shows a transition from viscous to strong viscoelastic behavior. These changes in the rheological behavior are produced by the transitions from sphere to rodlike micelles, which are induced by the hydrophobicity of AHC causing it to be absorbed into the core and the hydrophilic interface of the micelles, which screens the repulsions between the charged head groups.

Promotion Effect of Carbon Nanotubes-Doped SDS on Methane Hydrate Formation

To achieve greater performance of a low concentration of sodium dodecyl sulfate (SDS) in methane hydrate formation, SDS solutions were doped with pristine carbon nanotubes (pCNTs) and the oxidized forms (OCNTs). With nanotubes as the predominant accelerant in the mixed promoters, the nucleation stage could be shorten efficiently due to the continuous Brownian motion of more nanoparticles. The mixed promoters exerted more pronounced influence on the methane hydrate growth rate compared to the pure SDS, with the OCNTs-SDS system performing slightly better owing to the high dispersion and stability of the OCNTs in the aqueous SDS solutions. Nevertheless, the promotion effects of highly concentrated pCNTs or OCNTs could be weakened possibly due to the aggregation of nanotubes.

Adsorption kinetics of sodium dodecyl sulfate on perturbed air-water interfaces

A pendant bubble tensiometer was used to measure the relaxation of the surface tensions of aqueous sodium dodecyl sulfate (SDS) solutions for four different perturbed air-water interfaces under surface rinsing, sudden surface compression, continuous surface expansion and compression. The complete set of surface tension (ST) relaxations was monitored to study the adsorption kinetics of SDS. The ST increased in the surface rinsing experiment, and this increase indicated that the SDS that was adsorbed at the air-water interface desorbed from the interface. The ST relaxed continuously after sudden surface compression, and this continuous ST relaxation indicated that the desorption rate of SDS molecules was faster than the surface compression rate. The ST remained a constant value during the continuous surface expansion and surface compression, and this constant ST data indicated that the adsorption and desorption rates were faster than the surface perturbation rate in this study.

Kinetics of Methane Hydrate Formation in an Aqueous Solution with and without Kinetic Promoter (SDS) by Spray Reactor

Hydrate formation apparatus reported so far was mainly concentrated in stirred-tank batch environments. It was difficult to produce the high gas storage hydrate efficiently. Some nonstirred technology has been attracting more attention by researchers. This work proposed a new apparatus for hydrate formation by spraying water into a gaseous phase with a fine nozzle. It can get sufficient contact surface area for gas-liquid reaction. Methane hydrate formation experiments have been conducted using pure water and sodium dodecyl sulfate (SDS) aqueous solution for comparison at 277.15 K. The experiments were conducted at 7.0 and 6.0 MPa, respectively. Kinetics of methane hydrate formation have been investigated by methane consumption per mole of water and reaction rate. The mechanism of hydrate formation and kinetics property by spraying atomization were studied with the theory of crystal chemistry.

Optimisation of DNA hybridisation and toehold strand displacement from magnetic bead surfaces

Here, we present work on the improved hybridisation and release of specially designed pegylated double stranded DNA strands with a pendant toehold. For this forensically relevant DNA namely amelogenin (AMEL) (a sex determination gene) and the human c-fms (macrophage colony-stimulating factor) proto-oncogene for the CSF-1 receptor (CSF1PO) short tandem repeat (STR) were employed. Magnetic beads functionalised with oligonucleotide capture probes with complementarity to the dsDNA PCR product toehold were fabricated. Characterisation of the beads was achieved through dynamic light (DLS) scattering and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy showing successful attachment of the oligonucleotides. The time frame of hybridisation between the dsPCR product toehold and the oligonucleotide modified beads was decreased from 6 h to 10 min by pre-incubation of the oligonucleotide functionalised magnetic beads in 2% aqueous sodium dodecyl sulphate (SDS) solution. Fluorescent microscopy was used to determine the time of toehold mediated strand displacement of the captured dsPCR product from the magnetic bead. Initially, displacement was achieved within 6 h. This was subsequently reduced to 3 h by the addition of a rate accelerator, PEG6000 at 10% v/v.

Effects of SDS and SDBS on CO2Hydrate Formation, Induction Time, Storage Capacity and Stability at 274.15 K and 5.0 MPa

AbstractThe CO2 hydratetechnology is growing in relative to CO2 capture, storage and transportation processes. An experimental investigation on CO2 hydrate formation in case of SDS (Sodium dodecyl sulfate) and SDBS (Sodium dodecyl benzene sulfonate) with seven concentrationsi. e.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 g/L was conducted at temperature of 274.15 K and initial pressure of 5.0 MPa. It was found that SDS and SDBS surfactants havelittleinfluence on the total moles of gas consumed in the stirred reactor. The induction time of CO2hydrate formation was approximately 35 minsinboth of 0.5 g/L SDS and 0.3 g/L SDBS solution,while that was 50 minsin pure water. Although the surfactantsreduced the CO2hydrate induction time significantly, they did not show clear influence on the gas storage capacities. The maximum gas storage capacities of CO2 hydrate in pure water, SDS and SDBS aqueous solutions are 89.62, 92.67, 92.62 V/VH, respectively. The difference in decomposition time of CO2 hydrate formed in pure water, SDS and SDBS solutions indicates that SDS and SDBScan greatly enhance the stability of CO2 hydrate.

Rapid formation of dry natural gas hydrate with high capacity and low decomposition rate using a new effective promoter

In this research, the effects of sulfonated Lignin (SL) on formation rate, capacity and stability of natural gas hydrate have been investigated and the results compared with those of hydrate formation in pure water and Sodium dodecyl sulfate (SDS) aqueous solution. Experimental results verified that the reactor pressure is reduced by 63.8% after 15h when hydrate is formed in 500ppm SL aqueous solution, while when using the same amount of SDS it is reduced no more than 57.8% after the same duration of time. It was also noticed that the formed hydrate when using SL had a lower decomposition rate than that of SDS aqueous solution. The reactor pressure increased 0.66MPa during dissociation of SL natural gas hydrate after 70h while in the case of SDS solution, at similar conditions this amount was 0.94MPa. On the other hand, SL solution does not spume and so the formed hydrate is quite dense, brittle and dry which can be easily converted to powder while the hydrate formed in the SDS solution is foamy.

Cholesteric Liquid Crystal Droplets for Biosensors

By utilizing a microfluidics approach, we prepared uniformly sized cholesteric liquid crystal (CLC) droplets from MLC-2132 doped with a chiral dopant (S)-4-cyano-4'-(2-methylbutyl)biphenyl (CB15). We studied the helical structures and reflecting color patterns of high- and low-dopant CLC droplets coated with poly(vinyl alcohol) (PVA) and sodium dodecyl sulfate (SDS). One central large spot with reflecting color in the CLC droplets (initially coated with PVA for planar anchoring) changed to many small spots with the same reflecting color (chicken-skin pattern) when an SDS aqueous solution was introduced to increase the homeotropic anchoring power. These small spots subsequently merged into several spots (flashlight pattern) with time. The CLC droplets coated with poly(acrylic acid)-b-poly(4-cyanobiphenyl-4'-oxyundecyl acrylate) (PAA-b-LCP) (CLCPAA droplets) were pH-responsive. Their helical structure and the reflecting color pattern changed because of protonation (at low pH) and deprotonation (at high pH) of the carboxylic group of PAA, which causes the planar (tangential) and perpendicular (homeotropic) orientations, respectively. The CLCPAA droplets immobilized with glucose oxidase (GOx) and cholesterol oxidase (ChO) (CLCPAA-GOx and CLCPAA-ChO droplets, respectively), for glucose and cholesterol detection, exhibited high sensitivity (0.5 and 2.5 μM for the CLCPAA-GOx and CLCPAA-ChO droplets, respectively), good selectivity, and fast response (≤4 s). Further optimization will enhance their performance as biosensors. With this novel approach, detection is possible by observing the coloring pattern of CLC droplets, without the crossed polarizers that are necessary for nematic LC biosensor systems.

Surfactant Effects on Crystal Growth Dynamics and Crystal Morphology of Methane Hydrate Formed at Gas/Liquid Interface

This paper presents visual observations aiming to clarify the underlying physics of surfactant effects on clathrate hydrate crystal growth at the interface between methane gas and water with surfactant. Sodium dodecyl sulfate (SDS), which is commonly used in industrial processes, was used in this study. Various SDS mass fractions from 0 to wSDS = 100 ppm with a step of size 10 ppm were examined, where wSDS represents the mass fraction of SDS aqueous solution. The crystal growth behavior and the crystal morphology of the methane hydrate at the interface varied depending on surfactant concentration and ΔTsub. In systems with wSDS ≤ 20 ppm, the nucleation occurred on the droplet surface (gas/liquid interface), then grew laterally, and finally covered the whole droplet surface. On the contrary, at wSDS ≥ 30 ppm, the droplet shape was not maintained and enhanced hydrate crystal growth was observed compared to those systems with wSDS ≤ 20 ppm. Individual hydrate crystals at wSDS = 20 ppm were observed to be sma...

Construction and Optimization of the Dye Sensitization Solar Cell Using a Au Particle and a Natural Vegetable Pigment

Light of the sun is inexhaustible and clean. The study of the solar cell using light of the sun is currently conducted. Dye sensitization solar cell (DSSC) uses a metal complex having rare and expensive ruthenium (Ru), or organic dye. Therefore, in this study, a pigment from a naturally occurring plant for cost reduction was extracted and was used for sensitizing dye. However, the conversion efficiency of DSSC made using a nature plant pigment is low. Therefore, with reinforced light electric field occurred by the plasmon absorption of metal nanoparticles, the improvement of the conversion efficiency of DSSC using the natural plant pigment was tried. In this session, current density-voltage (i-V) characteristics is reported with construction of DSSC which put Au nanoparticles and the natural plant pigment together.In a 100 mL measuring flask, HAuCl4·4H2O, trisodium citrate dihydrate, and NaBH4 was added to this order to become 0.2 mM, 0.7 mM and 0.3 mM each. Au nanoparticles dispersion liquid was prepared in this way, and was added for triethylene glycol to become 30 vol%. In addition, polyethylene glycol, TiO2, and the sodium dodecyl sulfate aqueous solution were added for this Au nanoparticles dispersion liquid. Resulted mixture was sonicated. The paste, which was prepared by the method mentioned above, was applied on conductive face of an ITO substrate by the squeegee method. Substrate casted was calcined at 500 degrees Celsius for 1 hour. A layer prepared on ITO substrate was assumed as AuTiO2 film. On the other hand, after crushing a grape pericarp or 5 g of Phytolacca americana fruit in the mixer with "an aqueous solution which included 0.993 % by volume TFA in methanol 63.8 % by volume (63.8 vol% acidization methanol)", resulting mixture was filtered, centrifuged, and supernatant solution was provided with pigment solution. TiO2 film on ITO substrate was immersed in the pigment solution which was extracted, and was left at rest in a cool incubator of 5 degrees Celsius for 1 day. After dipping for 1 day, a substrate was washed in ultra-pure water and was dried in air. TiO2 film which was manufactured from the paste which did not include Au nanoparticles dispersion liquid. The AuTiO2 film and the TiO2 film modified with pigment were used as a working electrode. The ITO substrate which sputtered Pt was used as a counter electrode. Using these working and counter electrode, i-V characteristics was measured under the halogen bulb irradiation that transmitted a UV cut filter and a heat-rays absorption filter.By the UV-vis absorption spectrum in the pigment solution which was extracted from Phytolacca americana fruit and Kyoho grape pericarp, the maximum absorption wavelengths was confirmed about two pigment solution in a visible light region of 541 nm and 532 nm, respectively. In addition, in DSSC using the pigment that was extracted from Phytolacca Americana, as a result of i-V characteristics measurement, Light energy conversion efficiency and short circuit photocurrent density of approximately 2.4 times of DSSC using the pigment extracted from Kyoho grape were confirmed. As for this, a hydroxyl group of the TiO2 surface and one of the anthocyanin-based pigment forms hydrogen bonding in DSSC using Kyoho grape pigment, but it is thought that this is because electron transfer from the pigment to TiO2 was performed more effectively than a case of Kyoho grape because the carboxy group of the Betalain series dye and the hydroxyl group of the TiO2surface form ester bond in DSSC using the Phytolacca americana pigment. At present, to identify a nature pigment, structure analysis are being examined.Au nanoparticles dispersion liquid and the Phytolacca Americana pigment solution respectively showed the maximum absorption wavelength of 526 nm and 549 nm by UV-vis absorption spectrum. The conversion efficiency of DSSC which was assembled with AuTiO2 film and TiO2 film was respectively 0.05287 % and 0.01669 %. The difference in this conversion efficiency depends on magnitude relation of the short circuit photocurrent density. Charge transfer resistance decreases by adding the Au nanoparticles which are a metal to TiO2 which is a semiconductor, and it is thought that short circuit photocurrent density increased. In addition, it is thought that this is because the excitation of the pigment became easy to happen by reinforced light electric field occurred by the plasmon absorption of metal nanoparticles. The improvement of the conversion efficiency was confirmed, but performance is largely low in comparison with general DSSC. Therefore, by ac impedance measurement, the resistance ingredient in the cell is identified and the construction condition of the cell is being examined.

Transport of a partially wetted particle at the liquid/vapor interface under the influence of an externally imposed surfactant generated Marangoni stress

Marangoni flows offer an interesting and useful means to transport particles at fluid interfaces with potential applications such as dry powder pulmonary drug delivery. In this article, we investigate the transport of partially wetted particles at a liquid/vapor interface under the influence of Marangoni flows driven by gradients in the surface excess concentration of surfactants. We deposit a microliter drop of soluble (sodium dodecyl sulfate) aqueous surfactant solution or pure insoluble liquid (oleic acid) surfactant on a water subphase and observe the transport of a pre-deposited particle. Following the previous observation by Wang et al. [1] that a surfactant front rapidly advances ahead of the deposited drop contact line and initiates particle motion but then moves beyond the particle, we now characterize the two dominant, time- and position-dependent forces acting on the moving particle: (1) a surface tension force acting on the three-phase contact line around the particle periphery due to the surface tension gradient at the liquid/vapor interface which always accelerates the particle and (2) a viscous force acting on the immersed surface area of the particle which accelerates or decelerates the particle depending on the difference in the velocities of the liquid and particle. We find that the particle velocity evolves over time in two regimes. In the acceleration regime, the net force on the particle acts in the direction of particle motion, and the particle quickly accelerates and reaches a maximum velocity. In the deceleration regime, the net force on the particle reverses and the particle decelerates gradually and stops. We identify the parameters that affect the two forces acting on the particle, including the initial particle position relative to the surfactant drop, particle diameter, particle wettability, subphase thickness, and surfactant solubility. We systematically vary these parameters and probe the spatial and temporal evolution of the two forces acting on the particle as it moves along its trajectory in both regimes. We find that a larger particle always lags behind the smaller particle when placed at an equal initial distance from the drop. Similarly, particles more deeply engulfed in the subphase lag behind those less deeply engulfed. Further, the extent of particle transport is reduced as the subphase thickness decreases due to the larger velocity gradients in the subphase recirculation flows.

Kinetic study of oxidation of paracetamol by water-soluble colloidal MnO2 in the presence of an anionic surfactant

The kinetics of the oxidation of paracetamol [PCM] by water-soluble colloidal MnO2 was investigated spectrophotometrically at 298 K in the absence and presence of an anionic surfactant, sodium dodecyl sulphate (SDS), in aqueous solution. The reaction was first order with respect to [MnO2], [PCM] and [H2SO4]. The effects of [Mn(II)], [salt], dielectric constant and ionic strength of the medium on the kinetics of the reaction have also been examined. Micelles of SDS in aqueous solution accelerated the reaction rate, and partitioning of MnO2 in favour of the micellar pseudophase was remarkable. The catalytic effect of SDS in aqueous solutions has been treated by well-defined mathematical (Tuncay), Menger and Portnoy, and Piszkiewicz models. The binding constant (7.59 × 10−2 mol−1 dm3), dissociation constant (32.43), rate constant in the micellar phase (5.15 × 104 s−1), cooperativity index (1.98) and various thermodynamic activation parameters have been evaluated, and on the basis of the observed kinetic data, possible reaction mechanism and rate law have been proposed.

Submicellar aggregates in aqueous sodium dodecyl sulphate solutions: Investigations by dynamic light scattering and water penetration through porous media

Aqueous solutions of sodium dodecyl sulphate (SDS) are investigated by dynamic light scattering (DLS) and water penetration/wettability in porous hydrophobic chalk. The polydispersity index (PDI) and wettability are correlated with change in the population density of submicellar fragments. It is concluded that the number of submicellar fragments in aqueous surfactant solution is significantly reduced as a function of SDS concentration and in presence of different additives, namely sodium chloride (NaCl), dodecanol (C12OH) and dodecyl trimethyl ammonium bromide (C12TAB). The decrease in wettability and changes in polydispersity index (PDI) of micelles is correlated with the concentration of submicellar aggregates in aqueous solutions. The decrease in PDI as observed by DLS is a result of formation of stable micelles and subsequent reduction in population of submicellar aggregates. The water penetration in dustless chalk is primarily controlled by the rate of diffusion and subsequent adsorption of submicellar aggregates to the porous capillaries. With formation of stable micelles and reduction in number of submicellar aggregates, a peculiar reduction in water penetration is noted. The observed trend is described in terms of concentration of submicellar fragments under different conditions of surfactant solution.

Prediction of thermodynamic properties of sodium dodecyl sulfate aqueous solutions through the hetero-SAFT equation of state

A special version of statistical associating fluid theory (SAFT), the so-called hetero-segmented SAFT equation of state, has been extended to calculate the thermodynamic properties of sodium dodecyl sulfate aqueous solutions. The predicted properties were included the vapor pressure as well as second thermodynamic properties, such as speed of sound. Evaluation of the model has been done through comparison of the calculated vapor pressure with experimental data in the range of 298.15–313.15 K. The hetero-SAFT model is found to be able to correctly describe the thermodynamic derivative properties as well as pVT and VLE properties of ionic surfactant solutions.

The influence of highly charged Ce4+-cations on aqueous solutions of SDS

The surface dilatational modulus E is a fundamental system parameter of aqueous surfactant solutions which plays an important role in the physic of foams. In this contribution, we study the influence of highly charged Cerium-ions (Ce4+)-on the surface dilatational modulus E of aqueous sodium dodecyl sulfate (SDS) solutions. The E-modulus has been determined at two concentrations below the critical micellar concentration (cmc) in the frequency range from 3Hz to 500Hz using the oscillating bubble technique. The presence of Ce4+-ions increases the surface activity of the surfactant leading to a shift of the equilibrium surface tension isotherm to lower concentrations. The cmc is reduced to 2×10−3molL−1. Adsorption layers of aqueous SDS solutions exhibit a surface visco-elastic behavior. The magnitude and the phase of the complex dilatational modulus E increase in a continuous fashion with the frequency indicating a dissipative process within the adsorption layer. The presence of the electrolyte modifies the frequency characteristics of the complex modulus towards the features of a surface elastic system. Furthermore there are pronounced changes in the stability of the corresponding foams. The lifetime of wet foam lamella is significantly reduced by the presence of the Ce4+-ions. The results provide evidence for the decisive impact of surface visco-elastic properties on foam stability of aqueous surfactant solutions.

Encapsulation of octadecane in poly(divinylbenzene-co-methyl methacrylate) using phase inversion emulsification for droplet generation

Octadecane (OD), a heat storage material, was encapsulated into poly(divinylbenzene-co-methyl methacrylate) or P(DVB-co-MMA) matrix via the microsuspension polymerization. The oil droplets were first generated by using the phase inversion emulsification, i.e., adding a sodium dodecyl sulphate (SDS) aqueous solution into an oil phase (monomers:OD = 1:1) containing various concentrations of poly(vinyl alcohol) (PVA). Results showed that 0.1 wt% of SDS in aqueous medium with the additional rate of 2 mL/min and 3 wt% of PVA in oil phase were the optimal conditions for the formation of nonspherical microcapsules. The smallest number- (dn) and weight- (dw) average diameters of P(DVB-co-MMA)/OD were, respectively, 3.1 and 3.2 µm with a narrow particle size distribution (dw/dn) of 1.02. The latent heats of the encapsulated OD increased with increasing MMA content of microcapsules. The heat of melting (ΔHm; 223 J/g-OD) and crystallization (ΔHc; 230 J/g-OD) of the OD encapsulated in microcapsules using DVB:MMA of 30:70 were higher than those using only PDVB (189 and 193 J g-OD for ΔHm and ΔHc, respectively) and comparable to those of bulk OD (233 and 234 J/g-OD for ΔHm and ΔHc, respectively). The obtained P(DVB-co-MMA)/OD microcapsules would be useful as high performance heat storage material.

Methane Hydrate Crystal Growth At the Gas/Liquid Interface in the Presence of Sodium Dodecyl Sulfate

This study reports the visual observation made of the formation and growth of clathrate hydrate on the surface boundary of a Sodium Dodecyl Sulfate (SDS) aqueous solution droplet and surrounding methane gas. The experimental temperature range was from 276 K to 282 K, under the pressure of 7.8 MPa, at pure water, wSDS = 10 ppm and wSDS = 100 ppm, where wSDS denotes the mass fraction of SDS in the aqueous solution. At pure water and wSDS = 10 ppm, the hydrate crystals were initially observed at the droplet surface, and followed by lateral growth at the droplet surface. However, at wSDS = 100 ppm, it was observed that hydrate growth behavior greatly changed compared to pure water system. At wSDS = 100 ppm and ΔTsub < 6.0 K, the structure of the droplet was not maintained and hydrate crystals grew horizontally on to the stage. We defined the subcooling, ΔTsub, the difference between the system temperature and the equilibrium temperature of methane hydrate as driving force index for crystal growth. At wSDS = 100 ppm and ΔTsub ≥ 6.0 K, the hydrate grew perpendicularly to the stage. At wSDS = 100 ppm and each ΔTsub, the amount of hydrate produced increased compared to pure water system.

Thermodynamics of self-assembling of mixture of a cationic gemini surfactant and sodium dodecylsulfate in aqueous solution: Calorimetry, conductivity and surface pressure measurements

The thermodynamics and phase behavior of mixtures of cationic gemini surfactant decanediyl-α,ω-bis(dodecyldimethylammonium bromide) (12-10-12) and sodium dodecylsulfate (SDS) were studied in the dilute SDS-rich region. The enthalpy of interaction between both surfactant monomers before the critical micelle concentration for the mixture (cmcmix) was determined by isothermal titration calorimetry (ITC). After the cmcmix, ITC results exhibited a first process associated with a large endothermic enthalpy change followed by a second one with a very small exothermic enthalpy change. In the same regions, the conductivity curves show an increase in slope after the break, followed by a plateau region, respectively for the two processes. The combined results from the various methodologies used lead us to propose that the first process reflects the formation of non-spherical micelles and the second one the vesicle formation. The area per catanionic complex was obtained through surface pressure measurements, leading to an apparent packing parameter ⩾1. The observed behavior may be rationalized on the basis of the hypothesis that both surfactants distribute asymmetrically in the vesicle bilayers and unevenly in the non-spherical micelle. In order to get structural information Cryo-TEM experiments were performed, which provided images that support this interpretation. From all the information gathered a phase diagram was mapped, including three one-phase regions of spherical micelles, non-spherical micelles and vesicles.

Molecular dynamics study of salt influence on transport and structural properties of SDS micellar solutions

The results of all-atom molecular dynamics simulations of micellization in the salt-free sodium dodecyl sulphate (SDS) aqueous solution and in the solution with added 1:1 salt (sodium chloride) are reported. Micellar systems of different size are considered in order to study size effects. The influence of added salt on transport and structural properties of the SDS micellar solutions is investigated. The formation of a larger aggregate in the presence of the salt, compared to the salt-free surfactant solution, is observed. With the increase of the salt concentration the diffusion coefficients of coions, counterions, and water molecules decrease. The diffusivity of a premicellar aggregate demonstrates the non-linear dependence on the salt concentration, while the size of the aggregate remains constant. Along with transport properties, we also studied structural properties of the SDS micellar solution: aggregation numbers and sizes of surfactant aggregates, radial distributions of ions and various atoms.

Timesaving Washing of Textiles Utilizing 38 kHz Ultrasound

AbstractFrom the viewpoints of prevention of garment damage as well as saving of electric energy and processing time in laundering, the possibility of time reduction by applying ultrasound has been discussed. The shake washing of polyester and cotton fabrics soiled with model oily and/or particulate contaminants together with their original fabrics was performed in an aqueous sodium dodecyl sulfate solution (SDS) without and with ultrasound. The soil removal and redeposition were evaluated from the change in the Kubelka-Munk function of the soiled and non-soiled fabric surfaces due to the washing. In the presence of ultrasound, the removal of oleic acid and carbon black from the polyester spun fabric was remarkably promoted, especially in the initial stage of the washing process. On the other hand, the soil redeposition gradually increased with wash time, especially for carbon black. Therefore, the removal and redeposition were compared between wash time 1 min and 5 min using some soils and fabrics. The soil removal was slightly larger for the 5 min-washing, whereas the soil redeposition was considerably prevented for the 1 min-washing. Comparing with a conventional washing with a drum type washer, the 1 min-shake/ultrasound combination washing had little impact damage in spite of having similar detergency power.