Cationic Surfactants In Water Research Articles

Thermo-Responsive Polyion Complex of Polysulfobetaine and a Cationic Surfactant in Water

Poly(4-((3-methacrylamidopropyl)dimethylammonium)butane-1-sulfonate) (PSBP) was prepared via controlled radical polymerization. PSBP showed upper critical solution temperature (UCST) behavior in aqueous solutions, which could be controlled by adjusting the polymer and NaCl concentrations. Owing to its pendant sulfonate anions, PSBP exhibited a negative zeta potential of −7.99 mV and formed a water-soluble ion complex with the cationic surfactant cetyltrimethylammonium bromide (CTAB) via attractive electrostatic interaction. A neutral PSBP/CTAB complex was formed under equimolar concentrations of the pendant sulfonate group in PSBP and the quaternary ammonium group in CTAB. Transmittance electron microscopic images revealed the spherical shape of the complex. The stoichiometrically neutral-charge PSBP/CTAB complex exhibited UCST behavior in aqueous solutions. Similar to PSBP, the phase transition temperature of the PSBP/CTAB complex could be tuned by modifying the polymer and NaCl concentrations. In 0.1 M aqueous solution, the PSBP/CTAB complex showed UCST behavior at a low complex concentration of 0.084 g/L, whereas PSBP did not exhibit UCST behavior at concentrations below 1.0 g/L. This observation suggests that the interaction between PSBP and CTAB in the complex was stronger than the interpolymer interaction of PSBP.

Phase Behavior and Aggregate Transition in Aqueous Mixtures of Negatively Charged Carbon Dots and Cationic Surfactants

To prepare supramolecular structures with interesting dimensions and morphologies using nanometer-sized building blocks is highly challenging. Herein, negatively charged carbon dots (n-CDs), which bear carboxy and hydroxyl groups on the surfaces, are mixed, respectively, with two cationic surfactants in water, i.e., 1-tetradecyl-3-methylimidazolium bromide (C14mimB) and tetradecyltrimethylammonium bromide (TTAB). The phase behavior and aggregate transition in n-CDs/C14mimB and n-CDs/TTAB mixtures were investigated in detail. At a fixed concentration of n-CDs (cn-CDs, 0.1 mg·mL–1), both systems exhibit a phase sequence of an isotropic phase (I1), a turbid phase (T1), a precipitated phase (P), a second turbid phase (T2), and a second isotropic phase (I2) with increasing concentration of the surfactant (cs). While only vesicles were observed in the T1 phase, hexosomes were also detected in the T2 phase in addition to vesicles. The phase transition obtained by the experiments gains solid support from computer simulations using a dissipative particle dynamics method, which give structural details of the hexosomes and evidence of anion−π interaction in an n-CDs/C14mimB system. The results obtained in the current study reinforce the conclusion that CDs/surfactant is a good combination for facile construction of supramolecular structures. The aggregates with diverse morphologies open up the possibility of a variety of future applications.

Rapid analysis of anionic and cationic surfactants in water by paper spray mass spectrometry.

The discharge of wastewater containing surfactants and other industrial pollutants is contaminating the world's water resources which should be taken seriously. This paper describes a paper spray mass spectrometric (PS-MS) method for rapid and quantitative analysis of anionic and cationic surfactants in water samples. Eight cationic surfactants and four anionic surfactants can be simultaneously determined in positive or negative mode without sample pretreatment and chromatographic separation. The PS-MS analysis time was only 10 s. Under optimized conditions, the method presented a suitable linear range (1-80 μg mL-1, linear regression coefficients (R2) higher than 0.995 for cationic surfactants, R2 higher than 0.990 for anionic surfactants), a low limit of detection (0.05-0.35 μg mL-1 for cationic surfactants and 0.20-0.35 μg mL-1 for anionic surfactants), and satisfactory recovery values (97.3-106.1%). The method validation indicated that the method precision and accuracy were satisfactory. The results demonstrated that PS-MS is especially suitable for the high-throughput analysis of surfactants in water samples.

Stimuli-Responsive Biomass Cellulose Particles Being Able to Reversibly Self-Assemble at Fluid Interface.

Stimuli-responsive surface-active microcrystalline cellulose (MCC) particles are obtained by interaction with conventional cationic surfactants such as cetyltrimethylammonium bromide (CTAB) in aqueous media, where MCC are in situ hydrophobized by adsorption of the cationic surfactant in water via electrostatic interaction and with the in situ hydrophobization removed by adding an equimolar amount of an anionic surfactant such as sodium dodecyl sulfate (SDS). The trigger is that the electrostatic interaction between the oppositely charged ionic surfactants is stronger than that between the cationic surfactant and the negative charges on particle surfaces, or the anionic surfactant prefers to form ion pairs with the cationic surfactants and thus making them desorbed from surface of MCC. Reversible O/W Pickering emulsions can then be obtained by using the MCC in combination with trace amount of a cationic surfactant and an anionic surfactant, and the anionic surfactant with a longer alkyl chain is more efficient for demulsification. With excellent biocompatibility, biodegradability, and renewability, as well as low toxicity, the biomass cellulose particles that can be made stimuli-responsive and able to reversibly self-assemble at fluid interface become ideal biocompatible particulate materials with extensive applications involving emulsions and foams.

Adsorption of dodecylamine hydrochloride on graphene oxide in water

Cationic surfactants in water are difficult to be degraded, leading to serious water pollution. In this work, graphene oxide (GO) was used as an adsorbent for removing Dodecylamine Hydrochloride (DACl), a representative cationic surfactant. X-ray diffraction (XRD), FT-IR spectroscopy and atomic force microscope (AFM) were used to characterize the prepared GO. The adsorption of DACl on GO have been investigated through measurements of adsorption capacity, zeta potential, FTIR, and X-ray photoelectron spectroscopy (XPS). The experimental results have shown that the adsorption kinetics could be described as a rate-limiting pseudo second-order process, and the adsorption isotherm agreed well with the Freundlich model. GO was a good adsorbent for DACl removal, compared with coal fly ash and powdered activated carbon. The adsorption process was endothermic, and could be attributed to electrostatic interaction and hydrogen bonding between DACl and GO.

Responsive Aqueous Foams Stabilized by Silica Nanoparticles Hydrophobized in Situ with a Conventional Surfactant.

In the recent past, switchable surfactants and switchable/stimulus-responsive surface-active particles have been of great interest. Both can be transformed between surface-active and surface-inactive states via several triggers, making them recoverable and reusable afterward. However, the synthesis of these materials is complicated. In this paper we report a facile protocol to obtain responsive surface-active nanoparticles and their use in preparing responsive particle-stabilized foams. Hydrophilic silica nanoparticles are initially hydrophobized in situ with a trace amount of a conventional cationic surfactant in water, rendering them surface-active such that they stabilize aqueous foams. The latter can then be destabilized by adding equal moles of an anionic surfactant, and restabilized by adding another trace amount of the cationic surfactant followed by shaking. The stabilization-destabilization of the foams can be cycled many times at room temperature. The trigger is the stronger electrostatic interaction between the oppositely charged surfactants than that between the cationic surfactant and the negatively charged particles. The added anionic surfactant tends to form ion pairs with the cationic surfactant, leading to desorption of the latter from particle surfaces and dehydrophobization of the particles. Upon addition of another trace amount of cationic surfactant, the particles are rehydrophobized in situ and can then stabilize foams again. This principle makes it possible to obtain responsive surface-active particles using commercially available inorganic nanoparticles and conventional surfactants.

Topology, length scales, and energetics of surfactant micelles.

We study the morphology, energetics, and kinetics of a self-associating model cationic surfactant in water using large-scale coarse-grained molecular dynamics simulations over time scales that allow for probing micelle recombination dynamics. We develop an algorithm to track micelle contours and quantify various microstructural features such as contour length distribution, persistence length, and mesh size. We predict reliably the end-cap energy and recombination time of micelles, directly from molecular simulations for the first time. We further consider the variation of solution viscosity as a function of salt concentration and show that branched and multiconnected structures govern the experimentally observed anomalous dependence of zero-shear viscosity on salt concentration. Overall, simulation predictions are in good agreement with experiments.

Preconcentration of Total Mercury from River Water by Anion Exchange Mechanism

A simple and cheap analytical technique was developed for the measurement of total mercury in river water samples using inductively coupled plasma-mass spectrometry (ICP-MS). It is based on the direct complexation of mercury ions using iodide and a cationic surfactant in water for its subsequent solid-phase extraction. Mercury ions are retained on the silica phase as ion pairs in the presence of iodide ions and dodecyltrimethylammonium bromide. Parameters having influential influence on the retention of Hg(II) were investigated: sample flowrate, eluent type, sample volume, iodide and surfactant concentrations. The retained mercury ions are stripped off from silica phase using 10 mL of 8 mol L(-1) HNO3 and quantified by ICP-MS. An enrichment factor of 50 was achieved with a maximum adsorption capacity of 718 μg Hg(II) g(-1). The limit of detection of Hg(II) was 8 pg mL(-1). The developed method was applied for the determination of total mercury in river and tap-water samples.

Pressurized photo-reactor for the degradation of the scarcely biodegradable DPC cationic surfactant in water

The photocatalytic processes studied for the water depollution can be influenced by the operating pressure, being this parameter strictly correlated, by the Henry law, with the solubility of gas in the liquid phase. A proper reactor was built on purpose to investigate the influence of pressure on both photolysis and photocatalysis processes by using commercial nano-TiO2 sample. The degradation of a cationic surfactant, dodecyl pyridinium chloride (DPC) was investigated in a pressure range between 1 and 15bar and using three different gases (O2, He, Ar) in the headspace of the reactor. Oxygen is a reactant of the oxidizing process, while argon and helium are two inert gases (the first one with a solubility in water similar to oxygen and the second with a much lower solubility) used to verify the role of simple pressure action in the surfactants degradation. If oxygen is used as pressurizing gas, the mineralization degree of the pollutant is greatly enhanced with working pressure by both simple photolysis and also nanopowders assisted processes. The degradation mechanism appears to be fully comparable with the ones reported in the literature; the increased oxygen amount promotes only the rate and not the formation of reaction intermediates.

Direct Measurement of Contact Angles of Silica Particles in Relation to Double Inversion of Pickering Emulsions

In an alkane-water system containing submicrometer silica particles at high pH, double emulsion inversion from oil-in-water (o/w) to water-in-oil (w/o) to oil-in-water can be effected by increasing the concentration of a dichain cationic surfactant in water. The contact angle θ of the particles at the planar oil-water interface has been measured directly using freeze-fracture shadow-casting cryo-scanning electron microscopy, enabling single-particle measurements of high accuracy. θ passes through a maximum with respect to surfactant concentration. It is shown that particles undergo a hydrophilic-hydrophobic-hydrophilic transition corresponding closely to the o/w-w/o-o/w transformation observed in emulsions. These results unequivocally link the single-particle contact angles to the type of particle-stabilized emulsion, confirming macroscopic emulsion inversion on the microscopic level.

Electromotive force study on interaction between a triblock copolymer and cationic surfactants in water

The interaction between a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer F127 and three cationic surfactants with varying alkyl chain length in water were investigated in detail by electromotive force (EMF) studies. The cationic surfactants investigated are hexadecyltrimethylammonium bromide (HTAB), myristytrimethylammonium bromide (MTAB), and lauryltrimethylammonium bromide (LTAB) which have carbon numbers of 16, 14, and 12 in the alkyl chain, respectively. Obvious binding was detected by EMF measurements between F127 and HTAB. For MTAB, the binding has also been detected with a weaker strength than that of HTAB. The LTAB/F127 mixed system exhibits the weakest binding, presumably due to the too short alkyl chain. This indicates that the binding between cationic surfactants and F127 is mainly dominated by the hydrophobic/hydrophobic interaction. In addition, the interaction also shows considerable dependence on the concentration of F127 and solution parameters such as the salinity.

Effect of 1-alkanols/salt on the cationic surfactant micellar aqueous solutions—A dynamic light scattering study

The effect of 1-alkanols viz., ethanol, 1-butanol and 1-hexanol on five quaternary salts based cationic surfactants in water and in presence of 0.1 M salts has been systematically investigated by viscosity and dynamic light scattering (DLS) technique. The concentration for surfactant varying in non-polar tail, polar head and counterion was kept constant (∼50 mM) throughout. The viscosity data are less detailed, but confirm the general trend of micellar growth and transitions. Influence of 1-butanol on critical micelle concentration (CMC) and degree of counterion dissociation ( () was also investigated conductometrically. These measurements were done to supplement the role of counterions in exploring the binding phenomenon due to the effect of salt and alcohol during micellization. The effect of 1-alkanols upon the viscosity and micelle hydrodynamic diameter ( D h) of micelles in the presence of salt at varying concentration and temperature was also examined in detail to explain the hydrophobic interactions and electrostatic effects.

Coarse-Grained Molecular Dynamics Simulation of the Aggregation Properties of Multiheaded Cationic Surfactants in Water

The aggregation property of multiheaded surfactants has been investigated by constant pressure molecular dynamics (MD) simulation in aqueous medium. The model multiheaded surfactants contain more than one headgroup (x = 2, 3, and 4) for a single tail group. This increases the hydrophilic charge progressively over the hydrophobic tail which has dramatic consequences in the aggregation behavior. In particular, we have looked at the change in the aggregation property such as critical micellar concentration (cmc), aggregation number, and size of the micelles for the multiheaded surfactants in water. We find with increasing number of headgroups of the multiheaded surfactants that the cmc values increase and the aggregation numbers as well as the size of the micelles decrease. These trends are in agreement with the experimental findings as reported earlier with x = 1, 2, and 3. We also predict the aggregation properties of multiheaded surfactant with four headgroups (x = 4) for which no experimental studies exist yet.

Interaction of Reactive Brilliant Red with Cetylpyridinium and Application to Determination of Cationic Surfactant in Water

AbstractThe microsurface adsorption‐spectral correction technique and light adsorption ratio variation approach were jointly applied to characterization of the interaction of reactive brilliant red (RBR) with cetylpyridinium chloride (CPC) at pH 3.67. The interaction responded with the Langmuir isothermal adsorption. The saturated binding ratio of RBR to CPC is (1.2 ± 0.1): 1, and the bind constant of the RBR‐CPC complex was calculated to be (1.15 ± 0.05) × 105 1/mol. The interaction was applied to the determination of cationic surfactant in water by the light adsorption ratio variation approach with satisfactory results.

Revised Implicit Solvent Model for the Simulation of Surfactants in Aqueous Solutions. 2. Modeling of Charged Headgroups at Oil-Water Interface.

The revised implicit solvent model (ISM-2) for the simulation of cationic surfactants in water was proposed in the previous study (J. Phys. Chem. B 2005, 109, 11762): no water molecules of the solvent are explicitly treated, and their effects are incorporated using the solvent-averaged interactions between the surfactant segments in water, where the interactions between the hydrocarbon sites of the surfactants are allowed to vary depending on their surroundings. In the present study, the representation of a charged headgroup at the liquid-liquid interface between the hydrocarbon oil and the implicit water has been improved, where the free energy change due to the transfer of the charged headgroup across the interface is taken into account. The present model (ISM-3) has been applied to the molecular dynamics simulations of (i) the single preformed micelle of 30 n-decyltrimethylammonium chloride (C10TAC) cationic surfactants in water and (ii) 343 C10TAC surfactants uniformly dispersed in water, where the corresponding systems are also simulated using the ISM-2 for comparison. The first simulations showed that the ISM-3 as well as the ISM-2 is applicable to the simulation of the preformed micelle of the average aggregate size for C10TAC. The second simulations demonstrated that the ISM-3 can represent the surfactant self-assembling plausibly, while the ISM-2 fails to do so because of the rude treatment of the charged headgroups at the interface. The results will be compared with those from experiments and atomistic model simulations.

A multicommuted stop-flow system employing LEDs-based photometer for the sequential determination of anionic and cationic surfactants in water

It has been developed an automatic stop-flow procedure for sequential photometric determination of anionic and cationic surfactants in a same sample of water. The flow system was based on multicommutation process that was designed employing two solenoid micro-pumps and six solenoid pinch valves, which under microcomputer control carry out fluid propelling and reagent solutions handling. A homemade photometer using a photodiode as detector and two light emitting diodes (LEDs) with emission at 470 nm (blue) and 650 nm (red) as radiation sources, which was tailored to allow the determination of anionic and cationic surfactants in waters. The procedure for anionic surfactant determination was based on the substitution reaction of methyl orange (MO) by the anionic surfactant sodium dodecylbenzene sulfonate (DBS) to form an ion-pair with the cetyl pyridine chloride (CPC). Features such as a linear response ranging from 0.35 to 10.5 mg L −1 DBS ( R = 0.999), a detection limit of 0.06 mg L −1 DBS and a relative standard deviation of 0.6% ( n = 11) were achieved. For cationic surfactant determination, the procedure was based on the ternary complex formation between cationic surfactant, Fe(III) and chromazurol S (CAS) using CPC as reference standard solution. A linear response range between 0.34 and 10.2 mg L −1 CPC ( R = 0.999), a detection limit of 0.05 mg L −1 CPC and a relative standard deviation of 0.5% ( n = 11) were obtained. In both cases, the sampling throughput was 60 determinations per hour. Reagents consumption of 7.8 μg MO, 8.2 μg CPC, 37.2 μg CAS and 21.6 μg Fe(III) per determination were achieved. Analyzing river water samples and applying t-test between the results found and those obtained using reference procedures for both surfactant types provide no significant differences at 95% confidence level.

A spectrophotometric flow procedure for the determination of cationic surfactants in natural waters using a solenoid micro-pump for fluid propulsion

An automatic flow-analysis procedure for spectrophotometric determination of cationic surfactants in surface water using a solenoid micro-pump for propelling solutions of reagents and sample is described. The proposed method is based on a ternary formation complex between chromazurol S, the Fe(III) ion, and the cationic surfactant. The flow network comprised four solenoid micro-pumps controlled by a microcomputer, which performed the sampling step by loading a reaction coil with sample and reagent solutions and displacing the sample zone through the analytical path. The system is simple, easy to operate, and very flexible, with sufficient sensitivity to determine cationic surfactants in water without any pre-concentration or separation step. After determining the best operational conditions, favourable features such as a linear response between 0.34 and 10.2 mg L−1 of surfactant (R = 0.999), a relative standard deviation of 0.6% (n = 11) for a sample containing 3.4 mg L−1 of surfactant, a detection limit of 0.035 mg L−1 of surfactant, and a sampling throughput of 72 determinations per hour were achieved. The system was used to determine cationic surfactant in river-water samples, and recovery values between 91 and 106% were achieved.

The properties of mixtures of two cationic surfactants in water at water/air interface

Surface tension and conductivity measurements were carried out for systems containing mixtures of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPyB). The obtained results of the surface tension measurements were compared with those calculated from the relations derived by Joos, Miller and co-workers. From the comparison it appeared that using the modified adsorption isotherm derived by Joos the adsorption behavior of CTAB and CPyB mixture can be predicted satisfactorily, particularly at a low concentration of the mixture; however, the values of the surface tension of aqueous solutions of these mixtures can be predicted in the whole range of the mixture concentrations by the simple relationships of Miller et al. On the basis of the results obtained from measurements and calculations it was found that there is a linear relationship between the surface tension and composition of two cationic surfactant mixtures at their low concentration, however, at a concentration close to the critical micelle concentration (CMC) positive deviation from the linear relationship is observed. There can also occur positive deviation from linear relationships between CMC and the degree of surfactants ionisation in micelles and mole fraction of CTAB ( α) in mixture. In the case of excess concentration of CTAB and CPyB mixtures it was found that the maximal concentration of the mixture was somewhat higher than that for individual surfactants in the saturated monolayer. It was concluded that maximum adsorption probably results from changes of structure of the CPyB molecules in the mixed monolayer in comparison to their structure in the bulk phase and in the saturated monolayer of the individual surfactants.

Aggregation of a Dye on a Surfactant: Interaction of Coomassie Brilliant Blue G250 with Cetyltrimethylammonium Bromide and Determination of the Cationic Surfactant in Water

The interaction of Coomassie brilliant blue G250 (CBBG) with cetyltrimethylammonium bromide (CTAB) has been investigated at pH 9.50 by the microsurface binding‐spectral correction (MSASC) technique. The experiments confirmed that the aggregation of CBBG on CTAB obeys the Langmuir isothermal adsorption. The aggregate was characterized. Results showed that the monomer aggregate, CBBG2CTAB was formed at 30°C with a binding constant of 6.46 × 103. The aggregation was applied to the quantitative determination of the cationic surfactant in water samples with satisfactory results.

Sorption-Photometric Determination of Cationic Surfactants with the Use of Silica Gel and Dyes (Zincon and Thiazine Red)

Conditions were determined for the formation of colored ion-pair complexes of cationic surfactants with Zincon and Thiazine Red in aqueous solutions and at the surface of silica gel. A photometric method using Zincon with a detection limit of 1 mg/L and a sorption–spectrometric method using Thiazine Red with a detection limit of 2–3 μg/L were developed for the determination of trace cationic surfactants in water. The relative standard deviations of the results of analysis in both cases were no more than 10%. A test method with the use of indicator tubes filled with silica gel and Zincon as the reagent is proposed; the detection limit of cationic surfactants is 0.5 μg/L (RSD < 25%).