Sodium Dodecylbenzenesulfonate Micelles Research Articles

Effective treatment of high-concentration SDBS solution by developing a novel integrated technology of foam separation and photocatalysis

With the rapid increasing drainage of industrial sewage, the problems arising from sewage containing high-concentration surfactant become more urgent. In order to purify the high-concentration surfactant solution, a novel integrated technology of foam separation and TiO2 photocatalysis was developed. An anionic surfactant of sodium dodecyl benzene sulfonate (SDBS) was used as the model surfactant and its initial concentration in the simulated solution was 0.5 g/L. First, foam separation had been performed to primitively reduce SDBS concentration in the simulated solution. Based on the results of independent factor test, a five-level-three-factor central composite design (CCD) based on response surface design (RSM) was used to predict the optimal experimental conditions. Under above conditions, the enriching proportion and removing percentage of SDBS were 4.69 ± 0.14 and 84.85 ± 0.71 %, respectively. The surface tension and foam stability of the residual solution after foam separation had been measured using pulling ring method and bubbling method, respectively. The residual solution after foam separation possessed a higher surface tension and weaker foam stability compared with those of freshly prepared SDBS solution. Extrinsic fluorescence spectra using pyrene showed that interfacial adsorption had led to the generation of hydrophilic SDBS micelles. In order to perform TiO2 photocatalysis, the adsorption capacity of SDBS on TiO2 nanoparticles had been studied. The adsorption of SDBS on TiO2 nanoparticles obeyed Pseudo-second-order dynamics model and Freundlich isotherm model. Based on the unique optical property and particle entrainment capacity of foam, a coupling operation of foam separation and TiO2 photocatalysis was proposed to degrade SDBS in the residual solution. The suitable operating conditions were identified and the maximum degradation percentage of SDBS reached 94.86 ± 1.06 %. The total SDBS removing percentage of developed technology was 99.38 ± 0.10 %. Total organic carbon (TOC) concentrations of SDBS solution before and after treatment were measured using combustion oxidation coupled nondispersive infrared absorption method. Finally, the economic analysis was carried out to assess the cost effectiveness of the integrated technology of foam separation and TiO2 photocatalysis.

Optical fiber optofluidic laser based on surfactant solubilization of rhodamine B gain in an aqueous solution.

We report a whispering gallery mode (WGM)-based fiber optofluidic laser (FOFL), in which rhodamine B (RhB) in an aqueous surfactant solution of sodium dodecylbenzene sulfonate (SDBS) is used as the laser gain medium. Here, the role of SDBS is to scatter the RhB dye molecules to effectively prevent its self-association in the aqueous solution. Therefore, the fluorescence quantum yield of the used RhB dye is improved due to the enhanced solubilization, which results in a low lasing threshold of ∼2.2 µJ/mm2 when the concentration of SDBS aqueous solution reaches up to 20 mM, on par with or even better than most of the optofluidic dye lasers using RhB as the gain medium in an organic solution. We then establish a model of solubilization capacity of SDBS micelles, which successfully addresses the mechanisms of dye-surfactant interactions in the proposed FOFL system. We further apply this FOFL platform to the case of concentration sensing of the used SDBS, which exhibits a 2-order-of-magnitude improvement in sensitivity compared to the fluorescence measurement due to the signal amplification inherent to the lasing process. The proposed FOFL platform in combination with surfactant solubilization gain medium in an aqueous solution promises to enable chip-scale coherent light sources for various environmental and bio-chemical sensing applications.

Utilization of amphiphilic antihistamines drugs to enhance micellization of anionic surfactant and improve the binding and solubility of Itraconazole drug

Many salt-based medicines are used in pharmaceutical formulations as active components. Excipients performance can be improved by using these medicines. The use of amphiphilic antihistamine medications (diphenhydramine hydrochloride (DPC) and cetirizine hydrochloride (CTZ)) to improve sodium dodecylbenzene sulfonate (SDBS) micellization is demonstrated in this work. DPC/CTZ considerably lowered the critical micelle concentration (CMC) of SDBS in aqueous media by measuring conductivity. SDBS micelles demonstrated a greater electrostatic interaction with CTZ than DPC micelles, based on counterion binding (βc and B) and binding constant (Kb) values. The DPC/CTZ mean ion occupancy (i0) per SDBS micelle was also calculated using the UV spectroscopy experiment. For SDBS micelles, we observed that DPC and CTZ had i0 values of 1.700 and 2.622, respectively. The electrostatic interaction between the medication and the surfactants was shown to be controlling the i0 levels. The medicine Itraconazole (ITZ), which is poorly water-soluble, was found to be more soluble in SDBS micelles containing CTZ than in DPC combinations. At 0.002 mol L-1 in the aqueous medium, the greatest i0 values of ITZ were 185 in SDBS + DPC and 203 in SDBS + CTZ. The CMC and the binding behaviour of drug-micelles were found to be critical determinants in controlling ITZ drug solubilization. Finally, we concluded that the above formulation might be used in the pharmaceutical industry to improve multi-drug delivery systems.

Oil solubilization in sodium dodecylbenzenesulfonate micelles: New insights into surfactant enhanced oil recovery

HypothesisThe current mechanism of surfactant enhanced oil recovery (EOR) mainly relies on forming middle-phase microemulsions to get ultra-low oil-water interfacial tension. However, residual oil can also be recovered using low concentration surfactant solutions without microemulsion formation, and the interaction between the surfactant solution and crude oil at very early contact has not been studied yet. We hypothesize micelle solubilization of oil as an alternative EOR mechanism. ExperimentsSodium dodecylbenzenesulfonate (SDBS), anisole and 1-hexene were used as a model surfactant and model polar and nonpolar compounds in crude oil, respectively. The interaction between SDBS micelles and these two additives was investigated with dynamic light scattering, UV–Vis spectroscopy, 1H NMR spectroscopy, cryogenic transmission electron microscopy, confocal microscope and small angle neutron scattering. FindingsSDBS micelles become larger upon increasing additive concentration to transfer into swollen micelles. 1-Hexene is localized in the micelle core, and retains the spherical micelle shape, while anisole resides in the palisade layer and weakens the electrostatic repulsions among surfactant headgroups, inducing a sphere–rod transition. No emulsion droplets were observed for 0.2 wt% SDBS solution until 1.5 wt% anisole or 1-hexene was introduced. These findings help understanding the role surfactant micelles in EOR and propose a new mechanism for surfactant EOR processes.

Adsorption of Cu(II) by phosphogypsum modified with sodium dodecyl benzene sulfonate

Phosphogypsum (PG) is a solid waste generated during the wet production of phosphoric acid, and stockpiling PG causes serious pollution to the environment. Therefore, we prepared an adsorption material modified with sodium dodecyl benzene sulfonate (SDBS) based on PG (SDBS@PG). SDBS@PG can be regenerated and used in several adsorption-desorption cycles. The optimum conditions for Cu(II) removal are as follows: the Cu(II) concentration is 10 mg/L, the amount of adsorbent is 1.6 g/L, the pH is 6, and the contact time is 60 min. Under these conditions, the removal rate is 99.23 %. The kinetic data of adsorption conform to the pseudo-second-order model. The equilibrium isotherm results are consistent with the Langmuir isotherm equation. Furthermore, plausible mechanisms were proposed: PG was modified with SDBS, which greatly improved the adsorption of Cu(II) onto PG. The main reason is that SDBS is adsorbed on the surface of PG by chemical action in the form of micelles and then Cu(II) is adsorbed on the anionic SDBS micelles of SDBS@PG due to chemical and electrostatic interactions. This work indicates that SDBS@PG can be used for the removal of Cu(II) and is qualified for practical application.

Laccase-Mediator Systems as a Tool for the Development of Antistatic/Anticorrosion Protective Coatings Based on Conducting Polyaniline

Template polymerization of aniline was performed using a laccase-mediator system. The high redox-potential laccase from the basidiomycete fungus Trametes hirsuta was a catalyst for polymerization. The aniline dimer served as the redox mediator; atmospheric oxygen served as the oxidant. Sodium dodecylbenzenesulfonate micelles were used as a “soft” template. The biocatalytic polymerization of aniline resulted in conducting polyaniline/sodium dodecylbenzene sulfonate complex that was tested as a protective coating. The efficiency of the inhibition of copper corrosion by the complex was 86–87%, and the dissipation rate of positive and negative charges from cotton fabrics increased by 56 and 27 times, respectively.

(Invited) Microenvironment Effects on Photoluminescent Doped Sites of Locally Functionalized Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) with semiconducting features emit photoluminescence (PL) in near infrared (NIR) regions. Owing to their unique one dimensional nanostructures, strong quantum confinement and weak dielectric screening affect Coulombic interactions between electron and electron or hole and, therefore, the PL properties are sensitively changed by effects of microenvironments that are composed of surrounding surfactants and solvent molecules. [1] Recently, defect doping to SWNTs by local chemical functionalization is gathering great attention due to emergence of new PL properties. Namely, in the locally functionalized SWNTs (lf-SWNTs), additional PL (E 11*) appears with redshifted wavelengths and enhanced quantum yields compared to original PL (E 11) of pristine SWNTs.[2-9] Moreover, it is found that chemical structures of the modified molecules on the doped sites play an important role to determine and modulate the E 11* PL wavelengths.[4-9] Thus, their molecularly-tunable properties of the doped sites need to be clarified not only for fundamentals but also for advanced optical applications using the NIR PL. Here, we examine microenvironment effects on the E 11* PL of lf-SWNTs for characterization of the doped site properties by comparing those of the pristine sites. Nitroaryl-functionalized lf-SWNTs (lf-SWNTs-NO2) were synthesized using diazonium chemistry, which were solubilized in D2O containing sodium dodecylbenzenesulfonate (SDBS). For microenvironment creation using organic solvents[10], water immiscible organics such as o-dichlorobenzene (oDCB) was added and mixed in order to inject the organic solvent into the hydrophobic domains between the lf-SWNTs-NO2 and the coating SDBS micelles. In PL spectrum of lf-SWNTs-NO2 after the treatment using oDCB, PL peaks of E 11* and E 11 were redshifted from 1.085 eV and 1.269 eV to 1.069 eV and 1.257 eV, respectively. Other organic solvents also induced different spectral redshifts depending on their chemical structures. Importantly, the shifted energy values of the E 11* PL were larger than those of the E 11 PL when aromatic solvents were used. The energy shifts were analyzed by using a solvent parameter and a linear correlation was found. Details of these results will be discussed in this presentation together with effects of molecular structure differences in the doped sites of lf-SWNTs.

Effect of Template Type on the Trametes versicolor Laccase-Catalyzed Oligomerization of the Aniline Dimer p-Aminodiphenylamine (PADPA).

Many previous studies have shown that (i) the oxidation of aniline or the aniline dimer p-aminodiphenylamine (PADPA) in a slightly acidic aqueous solution can be catalyzed with heme peroxidases or multicopper laccases and that (ii) subsequent reactions lead to oligomeric or polymeric products, which resemble chemically synthesized polyaniline in its conductive emeraldine salt form (PANI-ES), provided that (iii) an anionic “template” is present in the reaction medium. Good templates are anionic polyelectrolytes, micelles, or vesicles. Under optimal conditions, their presence directs the reactions in a positive way toward the desired formation of PANI-ES-type products. The effect of four different types of anionic templates on the formation of PANI-ES-like products from PADPA was investigated and compared by using Trametes versicolor laccase (TvL) as a catalyst in an aqueous pH 3.5 solution at room temperature. All four templates contain sulfonate groups: the sodium salt of the polyelectrolyte sulfonated polystyrene (SPS), micelles from sodium dodecylbenzenesulfonate (SDBS), vesicles from a 1:1 molar mixture of SDBS and decanoic acid, and vesicles from sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Although with all four templates, stable, inkjet-printable solutions or suspensions consisting of PANI-ES-type products were obtained under optimized conditions, considerably higher amounts of TvL were required with SDBS micelles to achieve comparable monomer conversion to PANI-ES-like products during the same time period when compared to those with SPS or the two types of vesicles. This makes SDBS micelles less attractive as templates for the investigated reaction. In situ UV/vis/near-infrared, electron paramagnetic resonance (EPR), and Raman spectroscopy measurements in combination with an high-performance liquid chromatography analysis of extracted reaction products, which were deprotonated and chemically reduced, showed seemingly small but significant differences in the composition of the mixtures obtained when reaching reaction equilibrium after 24 h. With the two vesicle systems, the content of unwanted substituted phenazine units was lower than in the case of SPS polyelectrolyte and SDBS micelles. The EPR spectra indicate a more localized, narrower distribution of electronic states of the paramagnetic centers of the PANI-ES-type products synthesized in the presence of the two vesicle systems when compared to that of the similar products obtained with the SPS polyelectrolyte and SDBS micelles as templates. Overall, the data obtained from the different complementary methods indicate that with the two vesicle systems structurally more uniform (regular) PANI-ES-type products formed. Among the two investigated vesicle systems, for the investigated reaction (oxidation of PADPA with TvL and O2), AOT appears a somewhat better choice as it leads to a higher content of the PANI-ES polaron form.

Effect of surfactants on the treatment of radioactive laundry wastewater by direct contact membrane distillation

AbstractBACKGROUNDDirect contact membrane distillation (DCMD) was applied to treat the radioactive laundry wastewater produced from nuclear power plants (NPPs), with surfactants.RESULTSThe experimental results show that when 0.08 mmol L‐1 surfactants was added into feed solution, the permeate flux reduced sharply by 3–30% in 1 h, and the largest reduction was found in the case with non‐ionic surfactant. The decontamination factors (DF) of Sr(II), Co(II), and Cs(I) were correspondingly decreased 10–100 times within 4–8 h. Compared with the no salt‐added case, the addition of high concentration salt (100–300 g L‐1) slowed down the reduction rate of the permeate flux caused by sodium dodecyl benzene sulfonate (SDBS). The wetting of membranes by surfactants mainly results from the spontaneous adsorption of surfactant molecules onto the membrane surface and the reduction of solution surface tension. However, the high concentration of NaNO3 in SDBS solution decreases the critical micelle concentration (CMC) of SDBS to less than 0.06 mmol L‐1, and thus SDBS micelles formed, which were hard for the membrane surface to absorb.CONCLUSIONThe study shows that surfactants could cause serious reduction in permeate flux and rejection of nuclides, and thus they should be removed from the feed solution of DCMD process. © 2018 Society of Chemical Industry

Capillary electrophoresis investigation on equilibrium between polymer-related and surfactant-related species in aqueous polymer-surfactant solutions

It was inferred from aqueous solution behavior of nonionic polymers and anionic surfactants that the formation of charged polymer-bound surfactant micelle above critical aggregation concentration (cac) and the formation of free surfactant micelle beyond polymer saturation point (psp), but there was still a lack of direct experimental evidence for the considered equilibrium chemical species. Three modes of capillary electrophoresis are applied in this paper to study the complexation between nonionic polymers, polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG), and sodium dodecylbenzenesulfonate (SDBS) by successfully distinguishing the imaginary charged polymer-bound SDBS micelle from nonionic polymer and SDBS molecule. Perhaps even more important, it is the action of SDBS as both a main surfactant and a UV probe that makes the free surfactant micelle emerged in electropherogram beyond psp, and thus makes it possible for the first time to provide the equilibrium relationship of the polymer-related and the surfactant-related species in the concentration regions divided into by cac and psp.

Micelle-vesicle-micelle transition in aqueous solution of anionic surfactant and cationic imidazolium surfactants: Alteration of the location of different fluorophores

The presence of different surfactants can alter the physicochemical behaviors of aqueous organized assemblies. In this article, we have investigated the location of hydrophobic molecule (Coumarin 153, C153) and hydrophilic molecule (Rhodamine 6G perchlorate, R6G) during micelle-vesicle-micelle transition in aqueous medium in presence of anionic surfactant, sodium dodecylbenzenesulfonate (SDBS) and cationic imidazolium-based surfactant, 1-alkyl-3-methylimidazolium chloride (CnmimCl; n=12, 16).Initially, the physicochemical properties of anionic micellar solution of SDBS has been investigated in presence of imidazolium-based surfactant, CnmimCl (n=12, 16) in aqueous medium by visual observation, turbidity measurement, zeta potential (ζ), dynamics light scattering (DLS), and transmission electron microscopy (TEM). Zeta potential (ζ) measurement clearly indicates that the incorporation efficiency of C16mimCl in SDBS micelle is better than the other one due to the involvement of strong hydrophobic as well as electrostatic interaction between the two associated molecules. Turbidity and DLS measurements clearly suggest the formation of vesicles over a wide range of concentration.Finally, the rotational motion of C153 and R6G has also been monitored at different mole fractions of CnmimCl in SDBS-CnmimCl (n=12, 16) solution mixtures. The hydrophobic C153 molecules preferentially located in the bilayer region of vesicle, whereas hydrophilic R6G can be solubilized at surface of the bilayer, inner water pool or outer surface of vesicles. It is observed that rotational motion of R6G is altered significantly in SDBS-CnmimCl solution mixtures in presence of different mole fractions of CnmimCl. Additionally, the translational diffusion motion of R6G is monitored using fluorescence correlation spectroscopy (FCS) techniques to get a complete scenario about the location and translational diffusion of R6G.

Direct Observation of Coupling between Structural Fluctuation and Ultrafast Hydration Dynamics of Fluorescent Probes in Anionic Micelles.

The coupling of structural fluctuation and the dynamics of associated water molecules of biological macromolecules is vital for various biological activities. Although a number of molecular dynamics (MD) studies on proteins/DNA predicted the importance of such coupling, experimental evidence of variation of hydration dynamics with controlled structural fluctuation even in model macromolecule is sparse and raised controversies in the contemporary literature. Here, we have investigated dynamics of hydration at the surfaces of two similar anionic micelles sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS) as model macromolecules using coumarin 500 (C500) as spectroscopic probe with femtosecond to picosecond time resolution up to 20 ns time window. The constituting surfactants SDS and SDBS are structurally similar except one benzene moiety in the SDBS may offer additional rigidity to the SDBS micelles through π-stacking and added bulkiness. The structural integrity of the micelles in the aqueous medium is confirmed in dynamic light scattering (DLS) studies. A variety of studies including polarization gated fluorescence spectroscopy and quasielastic neutron scattering (QENS) have been used to confirm differential structural fluctuation of SDS and SDBS micelles. We have also employed femtosecond-resolved Förster resonance energy transfer (FRET) in order to study binding of a cationic organic ligand ethidium bromide (EtBr) salt at the micellar surfaces. The distance distribution of the donor (C500)-acceptor (EtBr) in the micellar media reveals the manifestation of the structural flexibility of the micelles. Our studies on dynamical coupling of the structural flexibility with surface hydration in the nanoscopic micellar media may find the relevance in the "master-slave" type water dynamics in biologically relevant macromolecules.

Rough glass surface-mediated transition of micelle-to-vesicle in sodium dodecylbenzenesulfonate solutions.

In this paper, we report a micelle-to-vesicle transition in aqueous solution of the anionic single-tailed surfactant (STS) sodium dodecylbenzenesulfonate (SDBS), with the mediation of a rough glass surface (RGS) in the absence of cosurfactants or additives. This transition produced a mixed solution of vesicles and micelles. Interestingly, the obtained SDBS vesicles in the solution displayed good stability during a long-term storage (at least 6 months at room temperature), exposure to high temperature (80 °C for 2 h), and freeze-thawing (-20 or -196 °C for 2 h to approximately 25 °C) after the RGS was removed. Our results confirmed that SDBS could adsorb on the RGS to form bilayers, in which the molecular packing parameter of SDBS was in the range of 1/2-1. The bilayer adsorption and the roughness of the solid surface played an important role in the vesicle formation. In addition, we propose a possible mechanism for the RGS-mediated transition of micelle-to-vesicle in SDBS solutions: SDBS micelles and molecules adsorb on the RGS to form curved bilayers; the curved bilayers detach from the RGS, and then close to form vesicles.

Cleaning ceramic membranes used in treating desizing wastewater with a complex-surfactant SDBS-assisted method

Ceramic ultrafiltration membranes were used to treat desizing wastewater for recycling. Both the fouling mechanisms and the regeneration of fouled membranes obtained from an industrial park were studied. The fouling was mainly caused by polymethyl acrylate (PMA) deposition on membrane surface and blockage in membrane pores. A cleaning strategy and solution composed of NaOH and sodium dodecyl benzene sulfonate (SDBS) were developed based on analysis of fouling resistance and interaction between cleaning agents and foulants, respectively. The hydrolysis of NaOH and solubilization of SDBS micelles, which decreased the adhesion between foulants and membrane surface, played an important role during the cleaning. The flux of the membrane could be well recovered with the cleaning solution. The cleaning efficiency was sensitive to the concentration of SDBS (CSDBS) and temperature (T), and was also affected by transmembrane pressure (TMP), crossflow velocity (CFV) and operation time of the permeate line (OTPL). The optimized cleaning condition was CSDBS=0.30wt.%, TMP=0.10MPa, CFV=3m/s, T=60°C, and OTPL=80min. The dynamic and chemical interaction between chemical agents, foulants and the membrane was also studied in this research. The methods were successfully applied to the industry.

Preparation of Nd2O3 nanorods in SDBS micelle system

Well-crystallized Nd2O3 nanorods were prepared in the aqueous solution containing neodymium nitrate, sodium hydroxide (dissolved in ethanol) and sodium dodecyl benzene sulfonate (SDBS). One dimensional nanorods of neodymium hydroxide were synthesized first, which was then placed at different temperatures (600 and 800 °C) in a calcar for 10 h to form Nd2O3 nanorods. The morphology and crystal structure of the products were investigated by X-ray diffraction, transmission electron microscopy, field emission transmission electron microscopy, Fourier transform infrared spectroscopy and fluorescence spectrometry. By using SDBS micelles as a template, this method manufactured uniform morphology of hexagonal one-dimensional neodymium oxide nanorods with a diameter ranging from 20 to 70 nm. The length of the nanorods increased with prolonged reaction time.

Improved antifouling of anion-exchange membrane by polydopamine coating in electrodialysis process

The fouling, in particular the organic fouling of anion exchange membranes (AEMs), is a serious problem in electrodialysis (ED). In this paper, we attempted to improve the antifouling potential of AEM by surface modification with polydopamine (PDA). The antifouling potential was evaluated by the transition time, i.e. the time elapsed before fouling took place, using sodium dodecyl benzene sulfonate (SDBS) as a model foulant. The negative surface charge density, hydrophilicity and roughness of the membrane surface were increased with increasing dopamine concentration in the modification solution. The increases in negative surface charge density and hydrophilicity increased the antifouling potential, while the increase in surface roughness decreased the antifouling potential. Consequently, the optimum modification condition was the immersion into a 0.1kg/m3 dopamine aqueous solution at pH8.8 for 24h. Under this condition, the antifouling potential of AEM was sufficiently improved. It was shown by theoretical analysis of the fouling data that the surface modification with PDA prevented the adsorption of SDBS micelles and improved the antifouling potential. Furthermore, it was experimentally confirmed that the modified membrane was highly stable.

Dynamics in Anionic Micelles: Effect of Phenyl Ring

Micellar dynamics in sodium dodecyl benzene sulfonate (SDBS) is studied using quasi-elastic neutron scattering (QENS) technique. Results are compared with sodium dodecyl sulfate (SDS), a very similar surfactant except for the presence of a phenyl ring in SDBS. SDBS is a very important system for various industrial usages and variety of other applications. The aim here is to investigate the effect of molecular architecture of the surfactant molecule on micellar dynamics. Analysis of the QENS data showed that there exists two distinct motions in both of the micellar systems: whole micellar motion or global motion and the internal motion of the monomer within the micelles. The global diffusion associated with the whole micelle is found to be Fickian in nature. The diffusion coefficient corresponding to the global motion is found to be significantly lower for SDBS than SDS micelles. As far as internal motion is concerned, the structure factor indicates that the alkyl chains are more flexible in SDS compared with SDBS. Similar behavior is also reported in a recent molecular-dynamics simulation study. Detailed analysis showed that a localized translational diffusion model in which the hydrogen atoms undergo diffusion within a sphere could describe the internal motions in both the micelles. Diffusion coefficients corresponding to internal motions is found to be lower in the case of SDBS micelles compared with SDS micelles, implying that internal motions in SDBS micelles are relatively hindered vis-a-vis SDS micelles. This could be understood in terms of denser packing in SDBS micelles due to the presence of π-stacking.

Improvement of the antifouling potential of an anion exchange membrane by surface modification with a polyelectrolyte for an electrodialysis process

Membrane fouling by organic solutes during electrodialysis is a well-known problem, especially during water treatment. Fouling causes an increase in membrane electrical resistance, leading to shortened membrane life and increased energy consumption. This article describes an improvement to the antifouling potential for an anion exchange membrane (AEM) by surface modification with poly(sodium 4-styrene sulfonate) (PSS). The antifouling potential of the AEM was evaluated by the transition time, i.e. the time elapsed before the fouling took place, using sodium dodecylbenzene sulfonate (SDBS) as a model organic foulant. It was shown that the antifouling potential of the AEM was considerably improved by surface modification with PSS. A mechanism for fouling by SDBS is also theoretically discussed and it is concluded that adsorption of SDBS micelles on the AEM surface was prevented by surface modification with PSS and the antifouling potential was improved because both hydrophilicity and the negative charge density were increased on the modified membrane surface. Additionally, it was confirmed that surface modification with PSS scarcely affects the performance of AEM during electrodialysis.

Vesicles Formation Induced by Layered Double Hydroxides in Mixture of Lauryl Sulfonate Betaine and Sodium Dodecyl Benzenesulfonate

AbstractThis paper reports that structurally positively charged layered double hydroxides (LDHs) nanoparticles induce the vesicle formation in a mixture of a zwitterionic surfactant, lauryl sulfonate betaine (LSB), and an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS). The existence of vesicles was demonstrated by negative‐staining (NS‐TEM) and freeze‐fracture (FF‐TEM) transmission electron microscopy and confocal laser scanning microscopy (CLSM). The size of vesicles increased with the increase of volume ratio (Q) of Mg3Al‐LDHs sol to the SDBS/LSB solution. A new composite of LDHs nanoparticles encapsulated in vesicles was formed. A possible mechanism of LDHs‐induced vesicle formation was suggested. The positive charged LDHs surface attracted negatively charged micelles or free amphiphilic molecules, which facilitated their aggregation into a bilayer membrane. The bilayer membranes could be closed to form vesicles that have LDHs particles encapsulated. It was also found that an adsorbed compound layer of LSB and SDBS micelles or molecules on the LDHs surface played a key role in the vesicle formation.

Ultrasmall Copper Nanoparticles from a Hydrophobically Immobilized Surfactant Template

Ultrasmall copper nanoparticles are produced by N,N,N',N'-tetramethyl-p-phenylenediamine (TMPDA) reduction of aqueous Cu(2+) on a hydrophobically immobilized sodium dodecylbenzenesulfonate (SDBS) surfactant template in the presence of sodium citrate at room temperature. Single-walled carbon nanotubes (SWNTs) act as a scaffold controlling the size of the SDBS micelle, which in turn confines a limited number of copper ions near the nanotube surface. TMPDA reduction forms copper nanoparticles as confirmed by X-ray photoelectron spectroscopy and electron diffraction, whose size was determined by atomic force microscopy and transmission electron microscopy to be approximately 2 nm. Particles formed in the absence of the SWNT immobilizer range from 2 to 150 nm.