Hexadecyltrimethylammonium Bromide Molecules Research Articles

SIMULTANEOUS ADSORPTION AND ANTIBACTERIAL ACTIVITIES OF SURFACTANT-MODIFIED KAOLINITE

Water contamination problems caused by various contaminants (i.e. anionic and cationic compounds, and pathogenic bacteria) necessitate the advanced material development for simultaneous adsorption and antibacterial actions. In this study, kaolinite (Kao) was modified with surfactant hexadecyltrimethyl ammonium bromide (HDTMA-Br) (0.1, 1.0 and 4.0 mM) and they were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and dispersion behaviour. No structural changes occurred after the adsorption of HDTMA-Br molecules on the Kao. In the simultaneous action study, the samples were tested for their adsorption capacity for cationic (methylene blue, MB) and anionic dyes (acid orange 7, AO7), and for antibacterial activities against Gram-negative (Escherichia coli ATCC11229) and Gram-positive bacteria (Staphylococcus aureus ATCC6538). HDTMA-modified Kao enhanced the adsorption of AO7 and the trend was correlated with the HDTMA adsorbed on Kao. The modified Kao with the highest HDTMA-Br concentration (KaoH4.0) showed 100% removal capacity for both dyes (AO7 and MB) and reduced the highest amount of both bacterial colonies. Therefore, the kaolinite modified with surfactant simultaneously enhanced the adsorption capacity of both positive and negative compounds, and increased the antibacterial activities against a wide spectrum of bacteria.

Research of structure and sorption properties of montmorillonite modified with hexadecylthymethylammonium bromide

The object of research is a natural layered silicate – montmorillonite of the Cherkasy deposit (Ukraine) with the general formula (Ca,Na)(А1,Mg,Fe)2(OH)2[(Si,А1)4О10]×nH2O. The chemical composition of the mineral: SiO2 – 51.9 %, Аl2O3 – 17.10 %, Fe2O3 – 7.92 %, MgO – 1.18 %, Na2O, K2O and CaO up to 2 % and Н2О – 8.78 %. Montmorillonite is characterized by a significant dispersion of particles and the presence of a large number of sorption centers on its surface is capable of cation exchange. One of the most problematic places is that montmorillonite is practically incapable of removing pollutants present in water as anions. In order to obtain sorbents capable of removing heavy metal anions, the surface of montmorillonite was modified with the cationic surfactant hexadecyltrimethylammonium bromide.During the study, X-ray diffraction analysis, scanning electron microscopy, infrared spectroscopy, and thermal analysis were used to study the structure of the initial montmorillonite and its organomodified forms. The spectrophotocolorimetric method is used to study the sorption properties of composites.The work confirms that hexadecyltrimethylammonium bromide molecules are sorbed not only on the outer surface of the particles, but also migrate between the aluminosilicate packets of the layered structure of montmorillonite. Sorption studies have confirmed that the use of organomodified forms of montmorillonite has increased the degree of extraction of chromium (VI) ions from 32 % to 96 %. The resulting sorbents make it possible to purify contaminated water with a chromium (VI) concentration of 1 mg/dm3 to the maximum permissible concentrations. This is due to the fact that the organomodification of the surface of montmorillonite has a number of features and allows to change the structure of the original mineral, as well as recharge the clay surface from negative to positive. This makes it possible to use organoclay to remove inorganic toxicants in anionic forms. Compared with similar known ones, the obtained composites provide the removal of even trace amounts of heavy metal anions from aqueous media.

Interfacial and Aggregation Behavior of Dicarboxylic Amino Acid-Based Surfactants in Combination with a Cationic Surfactant.

The interfacial and micellization behavior of three dicarboxylic amino acid-based anionic surfactants, abbreviated as AAS (N-dodecyl derivative of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) were investigated by surface tension, conductance, UV-vis absorption/emission spectroscopy, dynamic light scattering (DLS), and viscosity studies. Critical micelle concentration (CMC) values of the surfactant mixtures are significantly lower than the predicted values, indicating associative interaction between the components. Surface excess, limiting molecular area, surface pressure at the CMC, and Gibbs free energy indicate spontaneity of the micellization processes compared to the pure components. CMC values were also determined from the sigmoidal variation in the plot of micellar polarity and pyrene UV-vis absorption/emission intensities with surfactant concentration. The aggregation number, determined by static fluorescence quenching method, increases with decreasing mole fraction of the AAS (αAAS), where the micelles are mainly dominated by the HTAB molecules. The size of the micelle increases with decreasing αAAS, leading to the formation of larger and complex aggregates, as also supported by the viscosity studies. Micelles comprising 20-40 mol % AAS are highly viscous, in consonance with their sizes. Some of the mixed surfactant systems show unusual viscosity (shear thickening and increased viscosity with increasing temperature). Such mixed surfactant systems are considered to have potential in gel-based drug delivery and nanoparticle synthesis.

Simultaneous action of surfactant modified clinoptilolite: Adsorbent of dyes and antibacterial agent

In this study, the simultaneous action of surfactant modified clinoptilolite (SMC) as adsorbent for dyes and its antibacterial activity was investigated. Methylene blue (MB) and acid orange 7 (AO7) represent cationic and anionic dyes, respectively were used as adsorbate in this study and the antibacterial activity was studied against Gram-negative (Escherichia coli ATCC 11229) and Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 2921). Initially, natural zeolite clinoptilolite was modified with 3 different concentrations (0.1, 1.0 and 4.0 mM) of cationic surfactant hexadecyltrimethyl ammonium bromide (HDTMA-Br). The SMC samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), amount of HDTMA adsorbed and dispersion behaviour. Result from XRD shows that the HDTMA-Br molecules caused no effect on primary structure of the clinoptilolite since the clinoptilolite structure remained the same after modification with HDTMA-Br. Compared to the unmodified clinoptilolite, FTIR spectra of the SMC shows peak corresponds to C-H stretches which proved the attachment of HDTMA onto the clinoptilolite surfaces. In the dispersion behaviour study, SMC samples were located at the adjacent phase between the water and oil mixture. The amount of HDTMA-Br adsorbed onto the clinoptilolite increased with the increasing concentrations of the surfactant. The use of SMC as adsorbent and antibacterial agent were further studied against the ionic dyes and bacteria simultaneously. The results show that the adsorption capacity of SMC towards both ionic dyes increase with the increasing HDTMA-Br concentration. While for the antibacterial activity, the number of colony forming unit of bacteria seem to be highly reduced at the highest concentration of the HDTMA (4.0 mM) attached on the clinoptilolite. Hence, this study had shown that SMC has high adsorption capacity towards the ionic dyes at the same time reducing the growth of both Gram positive and negative bacteria in aquoes solution.

Adsolubilization-induced structural change in adsorbed surfactant aggregates: Equilibrium and kinetics monitored by AFM and QCM-D

Organic solutes with low water-solubility are solubilized into surfactant aggregates formed at solid/aqueous solution interfaces by the process of adsolubilization. In this study, we have characterized the adsolubilization of 1-hexanol (C6OH) into hexadecyltrimethylammonium bromide (HTAB) aggregates adsorbed on a silica surface, by means of atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D) techniques. The adsolubilization reduces electrostatic head-to-head repulsion between HTAB molecules forming the surface aggregates, along with additional adsorption of HTAB molecules at the solid/aqueous solution interface. At an HTAB concentration above the critical micelle concentration (cmc), the adsolubilization led to (i) a greater magnitude of repulsive interactions in the AFM force-distance data, (ii) a morphological change of the surface aggregates from a spherical or partially wormlike assembly into a flat bilayer, and (iii) an increased energy dissipation, reflecting an increased elasticity of the adsorbed aggregates. The kinetics of the adsolubilization-induced structural change was also studied at an HTAB concentration below the cmc; the increased C6OH concentration resulted in increased initial responses in frequency and dissipation. It seems likely that the kinetics is primarily driven by the diffusion of HTAB and C6OH molecules toward the silica surface, and the molecular reorganization within the adsorbed aggregates may also contribute to the kinetics especially at a low C6OH concentration.

Adsorption of Hexavalent Chromium and phenol onto Bentonite Modified With HexaDecylTriMethylAmmonium Bromide (HDTMABr)

The efficiencies of Hexadecyltrimethylammonium bromide (HDTMABr) modified bentonite (HDTMABt) for phenol and chromium removal from aqueous solutions were studied in batch experiments at pH = 9 and pH = 2 values, respectively. FTIR, SEM, XRD and BET analyses indicated that the HDTMABr molecules were intercalated in the interlayer and at the external surface of initially Na-bentonite (NaBt). Adsorption experiments showed that the HDTMABt was more efficient than the initial NaBt for the removal of phenol and chromium, simultaneously, the extent of the enhancement differed among these pollutants depending on their affinity towards these samples. The kinetic study revealed a rapid adsorption onto HDTMABt of the pollutants during the initial stage (teq < 1h). The pseudo-second-order equation fitted well to the experimental data. Phenol adsorption on NaBt and HDTMABt could be described by a linear Freundlich equation while Langmuir and Freundlich models were the most suitable for Cr(VI) adsorption on both samples.

Síntese e caracterização de zeólita de cinzas de carvão modificada por surfactante catiônico

Zeólita sintetizada a partir de cinzas leve de carvão foi modificada com diferentes concentrações (2 e 20 mmol.L-1) de brometo de hexadeciltrimetilamônio (HDTMA-Br). A zeólita não modificada (ZNM) e as zeólitas modificadas por surfactante (ZMS) foram caracterizadas por fluorescência de raios X, difração de raios X, espectroscopia no infravermelho com transformada de Fourier (FTIV), microscopia eletrônica de varredura, análise termogravimétrica, entre outros. As ZMS apresentaram carga negativa provavelmente devido à formação de bicamada parcial de HDTMA sobre os sítios ativos trocáveis na superfície externa da ZNM. Um decréscimo da área superficial foi observado para ZMS quando comparada com ZNM, indicando cobertura da superfície da zeólita com moléculas do HDTMA-Br. A natureza cristalina da zeólita permaneceu intacta após a adsorção do surfactante e o aquecimento para secagem. A análise de FTIV indicou que não houve mudanças significativas na estrutura da zeólita após a adsorção do surfactante.

Spectrophotometric studies on the interactions of C.I. Basic Red 9 and C.I. Acid Blue 25 with hexadecyltrimethylammonium bromide in cationic surfactant micelles

Interactions between cationic dye–cationic surfactant and anionic dye–cationic surfactant systems were investigated in aqueous solutions using spectrophotometric method at 288.15, 298.15, 308.15 and 318.15K. C.I. Basic Red 9 (BR9) and C.I. Acid Blue 25 (AB25) were used as cationic and anionic dyes, respectively, and hexadecyltrimethylammonium bromide (HDTMABr) was selected as cationic surfactant in this study. Although there was an interaction between the AB25 and the HDTMABr molecules, an interaction between the BR9 and HDTMABr did not occur due to the electrostatic repulsion forces. Binding constants and partition coefficients between the micellar and the bulk water phases for the AB25–HDTMABr system were calculated from the changes in absorbance values and the critical micelle concentrations at different temperatures. It was found that the values of binding constant and partition coefficient decreased with increasing temperature. Thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were determined for the binding and partition processes of AB25–HDTMABr system. It was concluded from ΔG0 values that the binding of AB25 to HDTMABr occurred spontaneously. In addition, the binding and partition processes were exothermic.

Long Nanofibers Arrays Through Surfactant Self-Assembly

Self assembly of molecules can be a simple and versatile approach that may lead to nanostructures. Here we report the formation of arrangements of exceptionally long nanofibers of cationic surfactant hexadecyltrimethylammonium bromide molecules with highly defined spatial and parallel ordering. Arrangements of approximately 1 microm long nanofibers were observed by non-contact atomic force microscopy. The long nanofiber patterns form structures in approximately 5 x 5 microm2 regions and consist of approximately 6 nm wide lines. The formation mechanism of the fibers is shown to be the coalescence of isolated surfactant micelles (approximately 3.2 nm diameter in solution) in the convection stream of the surfactant solution drop close to the pinned contact-line region during drying. The size of micelles formed in solution determines the diameter of the deposited fibers. New deposition schemes of micelles forming nanorods on bare silicon previous to the formation of surfactant bilayers are now being investigated based on the data obtained in this work.

Sorption of perfluorooctane sulfonate on organo-montmorillonites

Perfluorinated compound as one of the emerging pollutants has caused great attention in recent years. In this study, the organo-montmorillonites (organo-Mts) with different amounts and arrangements of hexadecyltrimethylammonium bromide (HDTMAB) were prepared as effective sorbents for PFOS removal from water. Batch sorption experiments including sorption kinetics, sorption isotherm as well as effect of solution pH were studied. The Elovich and pseudo-second-order models were selected to fit the kinetic data and the latter described the sorption kinetic better. Sorption isotherms showed that the sorption amount of PFOS increased with increasing amount of HDTMAB loaded in the montmorillonites, indicating that hydrophobic interaction played an important role in the sorption process. Comparative sorption of other perfluorinated compounds (PFCs) with different length of C–F chains and different functional groups further verified that hydrophobic interaction was the main force for the sorption of PFCs on the organo-Mts. X-ray diffraction (XRD) analysis demonstrated the significant decrease of interlayer distance after PFOS sorption, suggesting that the HDTMAB molecules were rearranged in the interlayer of organo-Mts. The PFOS molecules first diffused into the organo-Mts via hydrophobic interaction, and then the rearrangement occurred through electrostatic interaction between the two surfactants, resulting in the microstructure change within the organo-Mts.

The synergistic inhibition between hexadecyl trimethyl ammonium bromide (HTAB) and NaBr for the corrosion of cold rolled steel in 0.5 M sulfuric acid

The synergistic effect of the mixture of hexadecyl trimethyl ammonium bromide (HTAB) and various concentrations of NaBr on the corrosion of cold rolled steel in 0.5 M sulfuric acid has been investigated using weight loss method and polarization method. The results reveal that the corrosion of cold rolled steel has been efficiently inhibited by HTAB in the presence of NaBr in sulfuric acid, and inhibition efficiency increases with increasing concentration of NaBr at the same temperature. A synergistic effect has been observed for HTAB with NaBr at every experimental temperature. The polarization curves show that the complex of HTAB and NaBr is a mixed-type inhibitor. The experimental results suggest that the presence of bromide ion in the solution stabilizes the adsorption of HTAB molecules on the metal surface and improves the inhibition efficiency of HTAB. Langmuir adsorption isotherm equation was obeyed at all the temperatures studied. The synergism parameters have been calculated and discussed. The results obtained from weight loss method and polarization method are in good agreement.

Effect of molecular packing on adsorption and micelle formation of a homologous cationic surfactant mixture of hexadecyltrimethylammonium bromide and dodecyltrimethylammonium bromide

The surface tension of an aqueous solution of a hexadecyltrimethylammonium bromide (HTAB) and dodecyltrimethylammonium bromide (DTAB) mixture was measured as a function of the total molality and the composition of DTAB at 298.15 K under atmospheric pressure. The phase diagrams of adsorption and micelle formation were constructed and the excess Gibbs energy was evaluated by analyzing the phase diagrams thermodynamically. Both the excess Gibbs energy in the adsorbed film and the excess surface area are negative; therefore the mutual interaction between HTAB and DTAB is said to be stronger than that between the same species and is enhanced with increasing adsorption. By combining the results with those obtained in previous studies, we claimed that DTAB molecules can use effectively the space among the hydrocarbon chains of HTAB molecules and their polar head groups take a staggered arrangement at the surface so as to reduce the electrostatic repulsion. Consequently the dispersion force between hydrophobic chains becomes stronger. Furthermore, the comparison of the excess Gibbs energy in the adsorbed film with that in the micelle shows that the staggered arrangement of molecules is not necessary in the spherical micelle.

The Interaction between an Anthraquinoid Acidic Dye and Cationic Surfactant

The interaction between an anthraquinoid acidic dye and hexadecyltrimethylammonium bromide (HTAB) was studied spectrophotometrically.Three types of interactions were turned out; (1) The dye formed insoluble 1 : 1 salt with HTAB in the presence of excess dye. In this case, most of the added HTAB was consumed for the salt-formation. (2) The resolution of dye-surfactant salt was brought about in the presence of excess HTAB over the dye concentration. This was explained as the result of complex formation. The complex was estimated to consist of a single dye and three HTAB molecules. The complexed dye was surrounded with the rather hydrophilic environment in this case. (3) In the region of micelle formation of the surfactant, some of dye complexes penetrated into micelles. The cmc of this system was calculated to be 0.49mM from the absorbance measurement. Above cmc, the dyes were distributed to both the complex and the micelle ; the distribution coefficient (K) was 1.02×102. The standard free energy change of dye penetration (G0p) was determined to be -0.30kcal·mol-1. The number of penetrated dye molecules into a single micelle was calculated.