Octyltrimethylammonium Bromide Research Articles

Thermodynamics of micellization of octyltrimethylammonium bromide in 1,2-propanediol-water mixtures at temperatures from (293.15 to 308.15) K

The micellar properties of octyltrimethylammonium bromide (C8TAB) in both water and aqueous solutions of 1,2-propanediol have been investigated using accurate measurements of density, sound velocity, and surface tension in the temperature range between 293.15 and 308.15 K. The critical micelle concentration, CMC, the ionization degree, β, the standard thermodynamic parameters of micellization: free energy, ΔmicG°, enthalpy, ΔmicH°, entropy, ΔmicS° and the free energy of transfer, ΔtrG°, of the surfactant octyltrimethylammonium bromide in both water and 1,2 propanediol aqueous solution were evaluated from the experimental results.The CMC of the surfactant increases as the concentration of 1,2-propanediol increases, while the temperature does not exert important changes within the range considered.The value of the micellization thermodynamic parameters suggests that adding 1,2-propanediol makes the micellization process less favorable.The thermodynamic functions of transfer were calculated. The values of the free energy of transfer are small and positive and increase as the diol concentration increases confirming that the transfer of the surfactant from the bulk into the micelle is less favorable.

Label-free detection of platelet-derived growth factor-BB via liquid crystal/aqueous interface functionalized using a double-stranded DNA probe

A liquid crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with cationic surfactant octyltrimethylammonium bromide (OTAB) and adsorbed with a double-stranded deoxyribonucleic acid (dsDNA) probe at the LC/aqueous interface (TEMOTAB/DNA) was utilized for the highly specific detection of platelet-derived growth factor (PDGF-BB). Upon adsorption of the OTAB-coated 4-cyano-4′-pentylbiphenyl (5CB) on the TEM grid (TEMOTAB) and subsequent adsorption of the dsDNA probe, a homeotropic orientation was observed. Subsequently, the TEMOTAB/DNA biosensor was exposed to PDGF-BB, which induced a homeotropic-to-planar configurational change in 5CB, as observed using polarized optical microscopy with crossed polarizers. The optimized adsorption density of the dsDNA probe facilitated the detection of 2.63 pg mL−1 PDGF-BB in the detection range of 5–200 pg mL−1. Remarkably, this LC-based biosensor discriminated PDGF-BB from bovine serum albumin, immunoglobulin G, hemoglobin, carcinoembryonic antigen, epidermal growth factor, PDGF-AA, and PDGF-AB. The application potential of this sensor was further demonstrated by its effective performance in detecting PDGF-BB in both human serum and synthetic urine samples. Because of its high specificity, sensitivity, and label-free detection capabilities, this biosensor has potential applications in cancer detection.

Investigations of synergistic effect of surfactants as corrosion inhibitor on steel

The inhibition performances of the inhibitors C8TAB-MP (a mixture of octyltrimethylammonium bromide (C8TAB) and 4-mercaptopyridine (4MP)), C8TAB and 4MP toward A3 steel in 0.5 M hydrochloric acid solution were studied at 25°C. The studied inhibitors worked in a hybrid form, mainly controlling the cathodic reaction. Their adsorption follows the Langmuir isotherm, and the compositional combination is superior to the sum of their individual properties. The highest inhibition efficiency of C8TAB-MP was 99.4% at a concentration of 200 mg/l. The surface morphologies of samples were obtained from atomic force microscopy tests. The synergistic effect between C8TAB and 4MP was due to the C8TAB molecules donating electrons and the 4MP molecules accepting electrons.

Influence of tetraalkylammonium salts on the adsorption kinetics of bovine serum albumin in aqueous solutions at the air-liquid interface

Bovine serum albumin adsorption dynamics in water and in aqueous solutions of tetramethylammonium bromide, hexyltrimethylammonium bromide octyltrimethylammonium bromide, decyltrimethylammonium bromide, and dodecyltrimethylammonium bromide at the air-liquid interface was studied at a temperature of 298.15 K.The kinetics of the adsorption process of the biomolecule in water and in the aqueous alkylammonium solutions was investigated following the changes in surface tension with time. The measurements were performed on a high-precision drop volume tensiometer.The surface pressure data were adjusted with two of the most used semi-empirical kinetic models that describe the process of adsorption and allow the determination of the equilibrium adsorption parameters.The results in water and in the aqueous solutions containing tetraalkylammonium salts show that the adsorption kinetics is well described by a model consisting of three steps in which the transport of the protein in the initial stage is diffusion controlled. After some time, the rate is determined by the adsorption and the penetration of the protein at the air-liquid interface and the rearrangement of the protein at the interface; the evolution of both processes is described by steps that follow first-order rate equations.The results indicate that the overall adsorption process of bovine serum albumin BSA in water and the aqueous alkylammonium salts solutions is controlled by the second step which is the slowest of the three steps; it corresponds to the adsorption and penetration of the biomolecule at the air-liquid interface.

Magnetic deep eutectic solvent-based dispersive liquid–liquid microextraction for enantioselectively determining chiral mefentrifluconazole in cereal samples via ultra-high-performance liquid chromatography

A simple, rapid, and efficient pretreatment method of mefentrifluconazole enantiomers in cereal samples was established by dispersive liquid–liquid microextraction coupled with ultra-high-performance liquid chromatography-diode array detector (UHPLC-DAD). In this study, a novel ternary magnetic deep eutectic solvent (MDES) [octyltrimethylammonium bromide][cobalt chloride][acetic acid] was synthesized as the extractant. Acetic acid was used as the dispersant to promote the in situ dispersion of binary MDES [octyltrimethylammonium bromide][cobalt chloride]. The microdroplets of binary MDES containing mefentrifluconazole were separated by an external magnet. Device-assisted dispersion and time-consuming centrifugation steps were eliminated to ensure simplicity and rapidity of the pretreatment. Good linearity ranging from 0.01 μg g−1 to 2 μg g−1 was obtained. The extraction recovery varied from 82.9 to 95.0%. The limit of detection was 0.003 μg g−1. Finally, this established approach has been applied for the enantioselective detection of chiral mefentrifluconazole in corn, rice, wheat, millet, and sorghum samples.

Scission energy and topology of micelles controlled by the molecular structure of additives.

We employ coarse-grained (CG) molecular dynamics simulations (MD) to investigate the effects of the molecular structure of additives on the scission energy and morphology of charged micelles. Considering sodium dodecyl sulfate (SDS) as a representative charged surfactant and taking trimethylphenylammonium chloride (TMPAC) and octyltrimethylammonium bromide (OTAB) as oppositely charged additives, we show that the scission energy and topology of micelles vary significantly depending on the molecular structure of the hydrophobic part of the additives. The cyclic aromatic tail of the TMPAC disrupts the core structure of the SDS micelle and hence decreases the micelle scission energy, whereas the linear alkyl tail of the OTAB packs very well with the micelle core and increases the scission energy. Although both the additives have similar head structures, they lead to very different micelle morphologies because of the difference in the shape of their tail structures; ring-like or toroidal shaped micelles are formed in SDS/TMPAC solution whereas bicelle-like structures are formed in SDS/OTAB solution when the additive to surfactant ratio is higher than a certain value.

Integrating nanoclay intercalated with interlayers of cationic surfactant into thin-film nanocomposite nanofiltration membranes to improve performance and antifouling property

We fabricated thin-film nanocomposite (TFN) polyamide membrane for the treatment of brine solutions. Different surfactant-modified nanoclay (montmorillonite, MMT) were embedded separately into polyamide layer through interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). These cationic surfactants are: trimethyloctylammonium bromide (OTAB), hexadecyltrimethlammonium bromide (CTAB); and dimethyldioctadecylammonium bromide (DDAB). The cationic surfactants have different chemical structure, which can alter the d-spacing of the nanoclay. The surfactants can also facilitate the dispersion of the nanoclay in TMC/n-hexane solution. Among the surfactants, DDAB has the longest alkane chain on its chemical structure, thus adjusting the d-spacing of the nanoclay at most. TFNDDAB-MMT had the most uniformly dispersed nanoclays on the membrane surface compared to other membranes. The pure water flux of the membranes at 6 bar follows a decreasing order: TFNDDAB-MMT (66.02 ± 5.65 L m−2 h−1) > TFNOTAB-MMT (43.74 ± 3.88 L m−2 h−1) ≈ TFNNa-MMT (45.03 ± 2.80 L m−2 h−1) > TFNCTAB-MMT (41.69 ± 3.00 L m−2 h−1) ≈ TFC (40.93 ± 2.72 L m−2 h−1). Furthermore, it also enhanced the membrane antifouling property with a good stability in wide range of operating condition.

Preparation of Core-Shell Silica Microspheres with Controllable Shell Thickness for Fast High Performance Liquid Chromatography Separation of Alkyl Benzenes and Intact Proteins.

As it is difficult to prevent secondary nucleation and agglomeration during the preparation of core-shell silica microspheres, these issues have been successfully resolved in this study using template-dissolution-induced redeposition. The non-porous particles are transformed into core-shell silica microspheres (CSSMs) in the presence of cetyltrimethylammonium bromide and octyltrimethylammonium bromide under basic conditions. The shell thickness and pore sizes of the CSSMs are controlled by adjusting the etching time and molar ratio of the template, respectively. The CSSMs are modified using octadecyltrimethylammonium chloride to separate the mixture of alkyl benzenes, and a high column separation efficiency is achieved within two minutes. The CSSMs are used for the separation and analysis of proteins and the digests of bovine serum albumin. The chromatographic column packed with core-shell particles affords a significantly higher separation efficiency than the commercial column. Therefore, as a chromatographic stationary phase, these core-shell particles can potentially be used for the fast separation of proteins, small solutes, and complex samples.

Enhancing Lignin Dissolution and Extraction: The Effect of Surfactants.

The dissolution and extraction of lignin from biomass represents a great challenge due to the complex structure of this natural phenolic biopolymer. In this work, several surfactants (i.e., non-ionic, anionic, and cationic) were used as additives to enhance the dissolution efficiency of model lignin (kraft) and to boost lignin extraction from pine sawdust residues. To the best of our knowledge, cationic surfactants have never been systematically used for lignin dissolution. It was found that ca. 20 wt.% of kraft lignin is completely solubilized using 1 mol L−1 octyltrimethylammonium bromide aqueous solution. A remarkable dissolution efficiency was also obtained using 0.5 mol L−1 polysorbate 20. Furthermore, all surfactants used increased the lignin extraction with formic acid, even at low concentrations, such as 0.01 and 0.1 mol L−1. Higher concentrations of cationic surfactants improve the extraction yield but the purity of extracted lignin decreases.

Octyltrimethylammonium bromide-assisted synthesis of maghemite powder by thermal decomposition of ferric nitrate and its properties

Maghemite (γ-Fe2O3) powder was prepared by one-step thermal decomposition of ferric nitrate (Fe(NO3)3⋅9H2O) with the aid of octyltrimethylammonium bromide (OTAB). The effect of OTAB on the formation of γ-Fe2O3, structural properties and magnetic properties of the γ-Fe2O3 powder has been studied by X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, magnetic measurements and nitrogen adsorption–desorption. It is found that OTAB has a great influence on the thermal decomposition products of Fe(NO3)3⋅9H2O. With no OTAB addition, the thermal decomposition of Fe(NO3)3⋅9H2O produces only hematite (α-Fe2O3). In contrast, when OTAB is added to Fe(NO3)3⋅9H2O, a pure γ-Fe2O3 is formed, and its crystallite size can be controlled from 7.4 to 27.8 nm by varying the calcination temperature. Magnetic properties of γ-Fe2O3 powder are found to be strongly dependent on the calcination temperature. The saturation magnetization of γ-Fe2O3 powder increases from 28.6 to 67.5 emu g−1, when the calcination temperature increases from 160 to 200 °C. The sample obtained at 200 °C is nearly flake-like in shape and possesses a mesoporous structure with a Brunauer–Emmett–Teller surface area of 121.3 m2 g−1.

Potentiometric Study of Carbon Nanotube/Surfactant Interactions by Ion-Selective Electrodes. Driving Forces in the Adsorption and Dispersion Processes.

The interaction (adsorption process) of commercial ionic surfactants with non-functionalized and functionalized carbon nanotubes (CNTs) has been studied by potentiometric measurements based on the use of ion-selective electrodes. The goal of this work was to investigate the role of the CNTs’ charge and structure in the CNT/surfactant interactions. Non-functionalized single- (SWCNT) and multi-walled carbon nanotubes (MWCNT), and amine functionalized SWCNT were used. The influence of the surfactant architecture on the CNT/surfactant interactions was also studied. Surfactants with different charge and hydrophobic tail length (sodium dodecyl sulfate (SDS), octyltrimethyl ammonium bromide (OTAB), dodecyltrimethyl ammonium bromide (DoTAB) and hexadecyltrimethyl ammonium bromide (CTAB)) were studied. According to the results, the adsorption process shows a cooperative character, with the hydrophobic interaction contribution playing a key role. This is made evident by the correlation between the free surfactant concentration (at a fixed [CNT]) and the critical micellar concentration, cmc, found for all the CNTs and surfactants investigated. The electrostatic interactions mainly determine the CNT dispersion, although hydrophobic interactions also contribute to this process.

Structural, optical and photocatalytic properties of cuboid ZnO particles

Zinc oxide (ZnO) powders were prepared by solution combustion method using trimethyloctylammonium bromide (OTAB) and a mixture of OTAB and citric acid as fuel. Single phase ZnO powders with wurtzite structure were directly formed at high fuel contents (φ ≥ 1). The porous microstructure of combusted ZnO powders by mixed fuels had the specific surface area in the range of 73–416 m2/g in which increased with the increase of amount of fuels. The ZnO powders synthesized by single OTAB fuel were composed of the compacted agglomeration particles with cuboid-like morphology. The optical and photocatalytic properties of ZnO powders were determined as a function of fuel type and contents by diffuse reflectance spectroscopy and photoluminescence spectroscopy techniques. The ZnO powders obtained by OTAB-citric acid mixed fuel at φ = 1.5 showed the highest adsorption (53%) and photodegradation (95%) efficiency of MB dyes during 90 min under ultraviolet (UV) light irradiation.

Interconnected polyaniline nanostructures: Enhanced interface for better supercapacitance retention

Polyaniline and its nanocomposites have emerged as desirable electrode materials for supercapacitors. However, achieving specific capacitance with long-term cyclic stability is still a challenge. The present study reports on novel hierarchically porous and cross-linked polyaniline synthesized by a method employing aniline (monomer) and phytic acid (dopant acid) in the presence of octyltrimethyl ammonium bromide (OTAB) surfactant. The electrochemical performance of the phytic acid doped sample has been compared with HCl doped samples, the former being superior, i.e., a specific capacitance of 523 and 325 F g-1 at current densities of 0.25 and 10 A g-1, respectively. Additionally, the same possess excellent cycling stability with retention of ~88% of its initial capacitance over 10,000 charge-discharge cycles. Further, the phytic acid doped sample exhibited a lower equivalent series resistance (0.98 Ω cm2) than the HCl doped sample (1.26 Ω cm2). These results reveal the capability of the phytic acid doped hierarchical polyaniline sample as a promising active material for electrochemical applications.

Synthesis of fully porous silica microspheres with high specific surface area for fast HPLC separation of intact proteins and digests of ovalbumin.

Fully porous silica microspheres (FPSM) with high specific surface area and hierarchical pore as matrix for HPLC were prepared. First, the porous silica nanospheres with controllable particle size and pore diameter were successfully synthesized using a dual-templating approach, the pore size of nanospheres can be increased to 18.4nm by changing the molar ratios of octyltrimethylammonium bromide (TOMAB) and cetyltrimethyl ammonium bromide (CTAB), which is suitable for separation and analysis of biomolecules without pore enlargement. Then, the micron FPSM with hierarchical pore were synthesized by polymerization-induced colloid aggregation (PICA) using the porous nanospheres as a silicon source, which has alarge mesoporous structure (35.2nm) and high specific surface area (560m2g-1). Subsequently, the FPSM modified with octadecyltrichlorosilane were studied as stationary phase for separation of cytochrome C, lysozyme, ribonuclease A, and ovalbumin, bovine serum albumin, and the baseline separation of five proteins was achieved within 1min. The prepared column was also applied to the fast separation of digests of ovalbumin, and more chromatographic peaks were obtained compared to acommercial column under the same gradient elutionconditions. In addition, the static-binding capacity of the functionalized FPSM for bovine serum albumin (BSA) was measured to be 276mgg-1, which was nearly twice the static adsorption given inliterature. Therefore, these FPSM with high specific surface area and hierarchical pore structure are expected to have great potential for the separation of complex biological samples using HPLC. Graphical abstract A synthetic strategy was provided towards FPSM with hierarchical pores and high specific surface area using porous nanospheres as silicon source. The outstanding performance of the FPSM is that it has a high specific surface area while maintaining a large mesoporous size, which overcomes the disadvantage of sacrificing the specific surface area when increasing the pore size of porous silica microspheres prepared by using the traditional PICA method.

Green Synthesis of Silver Nanoparticles Using Tea Leaves from Three Different Elevations

AbstractGreen synthesis of nanoparticles offers numerous advantages over the conventional methods. This work provides a comprehensive understanding on the effect of tea cultivation elevation on the formation of silver nanoparticles (AgNPs) using green tea (Camellia Sinensis) leaves. The green tea leaves were collected from three different elevations: 86, 1700, and 2000 m above sea level in eastern Nepal. We found that AgNPs synthesized using tea leaves from 1700 m were homogeneously dispersed and smallest size, when compared to AgNPs synthesized using tea leaves from remaining two elevations. All aqueous dispersed AgNPs were sensitive towards mercury (II) ion over a range of other metal ions tested. However, the AgNPs synthesized using tea leaves from 1700 m resulted in better detection limit of 9.79 μM for sensing mercury (II) ions. Interestingly, the nanoparticles when additionally stabilized in aqueous trimethyloctylammonium bromide, a cationic surfactant among seven other surfactants tested, improved the detection limit to 0.71 μM.

Promising Route for the Development of a Computational Framework for Self-Assembly and Phase Behavior Prediction of Ionic Surfactants Using MARTINI.

Surfactants are amphiphilic molecules with multiple uses and industrial applications as detergents, wetting agents, emulsifiers, and so forth. They can be divided into three main categories: nonionic, ionic, and zwitterionic. The development of a universal computational framework able to predict key properties such as their critical micelle concentration (cmc) and the size of the micelles they form and to ultimately extract phase diagrams for their aqueous solutions, possibly in the presence of salts and oils, using their chemical constitution as input, would provide valuable information for the design and the production of these materials. In this work, we focus on ionic surfactants and investigate a possible route toward the development of such a framework based on coarse-grained simulations using the MARTINI forcefield in two versions: its implicit solvent version, called Dry MARTINI, and its explicit solvent version, called Wet MARTINI. The surfactants considered in our efforts are the anionic sodium dodecyl sulfate (SDS) and the three cationic cetyl, dodecyl, and octyl trimethyl ammonium bromide (CTAB, DTAB, and OTAB, respectively). First, we choose their mapping onto coarse-grained MARTINI beads. Next, we estimate their cmc's, their peak aggregation numbers, Nagg, and in the case of SDS, its small angle neutron scattering pattern at low concentrations, applying the Dry MARTINI forcefield. With a single modification to the Lennard-Jones energy parameter between hydrophobic beads and invoking Ewald summation with a physically meaningful dielectric constant for electrostatic interactions, our estimates are in very good agreement with experimental results. Furthermore, we predict the phase behavior of SDS/water and CTAB/water binary solutions using Wet MARTINI and find semiquantitative agreement with experimental phase diagrams. We conclude that the MARTINI forcefield, with careful treatment of electrostatic interactions and appropriate modification of parameters for some key functional groups, can be a powerful ally in the quest for a universal computational framework for the design of new surfactants with improved properties.

Organophilic Clay-Based Drilling Fluids for Mitigation of Unconventional Shale Reservoirs Instability and Formation Damage

High-performance drilling fluid was designed for unconventional reservoirs to minimize the formation damage and borehole instability using organophilic clay treated with trimethyloctylammonium bromide, novel in-house synthesized gemini surfactant, and a high-molecular weight polymer. This gemini surfactant has not been reported in the literature for drilling fluid applications. The performance of designed drilling fluid was evaluated and compared with the base drilling fluid (4 w/v.% bentonite dispersion water). Shale dispersion, linear swelling, filtration, and rheological experiments were performed to investigate the effect of drilling fluids on borehole stability and formation damage. The combined use of organophilic clay and surfactant in the drilling fluid formulation reduced the shale dispersion up to 89%. The linear swelling experiment of shale sample shows 10% swelling of the core in the modified drilling fluid while in base fluid 13% swelling of shale was observed. It was found that modified drilling fluid interactions with shale were greatly reduced using a surfactant and associative polymer in the drilling fluid formulation. Rheological properties of drilling fluids were stable, and filtration characteristics showed that the filtrate volume was within the acceptable limit. The designed drilling fluid made a thin and impermeable filter cake that prevents the invasion of drilling fluid into the formation. This study opens a new direction to reduce the formation damage and borehole instability using organophilic clay, surfactant and high-molecular weight additive in water-based drilling fluid.

One-pot synthesis of SiO2@SiO2 core-shell microspheres with controllable mesopore size as a new stationary phase for fast HPLC separation of alkyl benzenes and β-agonists.

Monodisperse SiO2@SiO2 core-shell silica microspheres (CSSM) with enlarged mesopores perpendicular to the particles surface were prepared using a dual-templating approach. With cetyltrimethyl ammonium bromide as the template and octyltrimethyl ammonium bromide as an auxiliary chemical, the pore size can be enlarged from 2.6 to 10.6nm. The average shell thickness can be increased from 31nm to 97nm by adjusting the concentrations of the surfactants under continuous addition of tetraethyl orthosilicate. After coating twice, the resulting CSSM has a uniform mesoporous shell of about 198nm thickness and a narrow pore size distribution. The CSSM were then modified with octadecyltrichlorosilane to give a material referred to as CS-C18. It was evaluated by separating the mixture of methylbenzene (toluene), ethylbenzene, n-propylbenzene, n-butylbenzene, n-amylbenzene and hexylbenzene. The baseline separation of the six alkyl benzenes is achieved within 2min. Compared to a commercial column of type BEH-C18, CS-C18 shows a faster and better separation even at lower back pressure. It was also applied to the fast separation of benzo[a]pyrene, salbutamol, ractopamine and clenbuterolin residues in pork samples. The high column efficiency and better reproducibility suggest that the CSSM can be used as a matrix for fast separation and analysis of several kinds of small analytes. Graphical abstract A dual-templating approach was utilized to produce the core shell microsphere with controllable mesopore channels by using hexadecyltrimethylammonium bromide (CTAB) as the template and trioctylmethylammonium bromide (TOMAB) as an auxiliary chemical to enlarge the size of CTAB micelles.

Tetrodotoxin, Epinephrine, and Chemical Permeation Enhancer Combinations in Peripheral Nerve Blockade.

Chemical permeation enhancers (CPEs) have the potential to improve nerve blockade by site 1 sodium channel blockers such as tetrodotoxin (TTX). Here, we investigated the efficacy and toxicity of CPE-enhanced nerve blockade across a range of TTX concentrations using 2 CPEs (sodium octyl sulfate and octyl trimethyl ammonium bromide). We also tested the hypothesis that CPEs could be used to reduce the concentrations of TTX and/or of a second adjuvant drug (in this case, epinephrine) needed to achieve prolonged local anesthesia METHODS:: Sprague-Dawley rats were injected at the sciatic nerve with combinations of TTX and CPEs, with and without epinephrine. Sensory and motor nerve blockade were assessed using a modified hot plate test and a weight-bearing test, respectively. Systemic and local toxicities of the different combinations were assessed. Addition of increasing concentrations of TTX to fixed concentrations of CPEs produced a marked concentration-dependent improvement in the rate of successful nerve blocks and in nerve block duration. CPEs did not affect systemic toxicity. At some concentrations, the addition of sodium octyl sulfate increased the duration of block from TTX plus epinephrine, and epinephrine increased that from TTX plus CPEs. The addition of epinephrine did not cause an increase in local toxicity, and it markedly reduced systemic toxicity. CPEs can prolong the duration of nerve blockade across a range of concentrations of TTX. CPEs could also be used to reduce the concentration of epinephrine needed to achieve a given degree of nerve block. CPEs may be useful in enhancing nerve blockade from site 1 sodium channel blockers.

Cationic surfactant as methane–water mass transfer enhancer for the fermentation of Methylosinus trichosporium OB3b

Abstract In this paper, we conducted an investigation into the use of bubbles modified with cationic surfactants in bubble coalescence inhibition and enhancement of methane-water volumetric mass transfer rate. Various cationic surfactants including hexyltrimethylammonium bromide (HTAB), octyltrimethylammonium bromide (OTAB), dodecyltrimethylammonium bromide (DTAB), and hexadecyltrimethylammonium bromide (HDTAB) were added to aqueous solution and the methane-water volumetric mass transfer coefficient (k L a) values were determined for each of the solutions. Enhancement of methane-water k L a was observed from 14 h −1 to 69 h −1 , depending on the cationic surfactant type and concentration. Enhanced methane-water k L a in aqueous solution by addition of cationic surfactants was employed for the fermentation of methanotroph ( Methylosinus trichosporium OB3b), and cell growth rate and maximum optical density was increased by 391% and 498%, respectively.