Decyltrimethylammonium Bromide Research Articles

Impact of surface-active ionic solutions on the structure and function of laccase from trametes versicolor: Insights from molecular dynamics simulations

Many protein-ionic liquid investigations have examined laccase interactions. Laccases are a class of poly-copper oxidoreductases that retain significant biotechnological relevance owing to their notable oxidative capabilities and their application in the elimination of synthetic dyes, phenolic compounds, insecticides, and various other substances. This study investigates the impact of surface active ionic liquids (SAILs), namely, decyltrimethylammonium bromide [N10111][Br] and 1-decyl-3-methylimidazolium chloride [C10mim][Cl] as cationic surfactant ionic liquids and cholinium decanoate [Chl][Dec], an anionic surfactant ionic liquid, on the structure and function of laccase from the fungus Trametes versicolor (TvL) by the molecular dynamics (MD) simulation method. In summary, this study showed that laccase solvent-accessible surface area increased in the ionic liquid [Chl][Dec] while it decreased in the other two ionic liquids. Interestingly, [Chl][Dec] ionic liquid components formed hydrogen bonds with laccase, while [N10111][Br] and [C10mim][Cl] components were unable to form hydrogen bonds with laccase. The quantity of hydrogen bonds formed between water molecules and the enzyme was also diminished in the presence of [Chl][Dec] in comparison to the other two ionic liquids. especially at a concentration of 250 mM. In 250 mM concentrations of [N10111][Br] and [C10mim][Cl], clusters of long-chain cations are likely to form near the copper T1 site. However, even at low [Chl][Dec] concentrations, long [Dec]- chains were observed to penetrate the enzyme near the copper T1 site, and at 250 mM [Chl][Dec], a large cluster of anions occupied the opening of the active site. The results of the analysis also show that the interaction between the [Dec]- anion and the enzyme is stronger than the interaction between [N10111]+ and [C10mim]+ with laccase; in addition, the [Dec]- anion, compared to [Br]- and [Cl]- has a much greater tendency to bind with the enzyme residues.

Imidazolium surface-active ionic liquids as antifungal agents in wood protection

This research focuses on five newly surface-active ionic liquids (SAILs) whose commitment to sustainable chemistry allows for their utilization as effective wood protection agents alternatives to traditional surfactants. The synthesis yields were above 93 %, while the purity ranged from 97 to 99 %. Also, a series of properties such as surface activity, wettability, antifungal properties were studied. The demonstrated relationship between critical micelle concentration (CMC) and elongation on alkyl chain length of the investigated imidazolium SAILs aligns with expectations. Moreover, it was shown that all tested SAILs exhibited lower CMC values (ranged from 0.34 to 8.46 mmol⋅L−1) than conventional surfactants such as didecyldimethylammonium chloride (DDAC) and decyltrimethylammonium bromides (CTAB) proving that the synthesized compounds can serve as substitutes for surfactants. 3-Decyloxymethyl-1-methylimidazolium dicyanamide (SAIL-3) showed the best antifungal properties, which does not translate into contact angle (CA) values. The mechanical properties measured for the impregnated wood samples were consistently inferior to those of the control wood samples. However, wood treated with SAIL-3, in contrast, exhibited a reduced uptake of free water compared to the untreated control wood. The results presented validate our hypothesis regarding the distinctive nature of SAILs and affirm their suitability for wood impregnation.

In English

Silicas of MCM-41‑type with reactive functional groups are widely used as starting substrates in large variety of post‑synthetic chemical modification pathways. Therefore, variation of their structural characteristics in the process of templated sol‑gel synthesis or post-synthetic treatment is of great importance. The aim of this work was to elucidate the influence of template agent selection on structural features of MCM-41‑type materials with surface silanol and 3‑chloropropyl groups. For this purpose, template-assisted sol-gel condensation of structure forming silanes (tetraethyl orthosilicate and 3‑chloropropyltriethoxysilane) was carried out in the presence of decyltrimethylammonium bromide as structure-directing agent. The capability of cyclic oligosaccharide (β-cyclodextrin) to interact with surfactant micelles in the process of hydrothermal sol-gel synthesis and to influence the formation of mesoporous structure of silica materials was studied. The IR spectroscopy was applied to carry out control under the complete removal of template moieties from pores by extraction procedure and to confirm introduction of 3‑chloropropyl groups into the surface layer of synthesized silicas. Arrangement of mesoscale pores and structural parameters were estimated from the results of X‑ray diffraction and low-temperature adsorption-desorption of nitrogen. It has been found that β‑cyclodextrin as component of hybrid template has positive effect on porous structure of 3-chloropropyl-functionalized MCM-41-type silica causing increase of surface area accompanied with preservation of pore ordering. Moreover, both ionic surfactant and oligosaccharide components of hybrid template act as porogens during sol-gel condensation of structure forming silanes enable to prepare silica materials with micro-mesoporosity. Proposed approach can be useful in synthesis of MCM‑41‑type silicas with surface linker groups and controlled structural characteristics (pore size, geometry and ordering), which have great potential as substrates in design of sophisticated materials.

A comprehensive study on the effect of rock corrosion and CO2 on oil-water interfacial tension during CO2 injection in heavy oil reservoirs

This study is focused on addressing issues related to the interaction mechanism between reservoir rocks and fluids during CO2 injection in heavy oil reservoirs. The results indicate that the carbonated water formed after high-pressure CO2 injection is causing corrosion in the core structure. Furthermore, the average corrosion rate increases from 0.358% as pressure increases from 8 MPa to 16 MPa to 0.742%. The core slices exhibit corrosion pits and cracks on their surface, as well as surface particles flaking and dissolving. The dynamic IFT between decyl trimethyl ammonium bromide solution and crude oil exhibited slower stabilization and less change without CO2 injection. However, with increasing pressure post CO2 injection, the dynamic IFT decreased at a more rapid rate. Furthermore, positive correlation between equilibrium IFT and temperature was observed with low-pressure CO2. In contrast, the surfactant played a more dominant role in reducing IFT with high-pressure CO2. The findings of this study can help for better understanding of the mechanism of microscopic action on reservoir rock and oil-water interface after CO2 injection, and offer theoretical basis and reference for CO2 injection in heavy oil reservoirs to enhance the recovery rate.

Towards compartmentalized micelles: Mixed perfluorinated and hydrogenated ionic surfactants in aqueous solution

HypothesisAqueous solutions of mixtures of hydrogenated and perfluorinated ionic surfactants are known to display anomalous aggregation behavior due to the mutual phobicity between hydrogenated and perfluorinated chains. Despite all efforts, different experimental limitations prevented so far a definite interpretation of the existing experimental results: both intermicellar and intramicellar segregation remain acceptable possibilities. MethodThe potential for segregation of mixtures of fluorinated and hydrogenated ionic surfactants in water was assessed using atomistic molecular dynamics simulations. Aqueous mixtures of hydrogenated and perfluorinated ionic surfactants were studied: mixtures of anionic surfactants (sodium dodecylsulfate (SDS) + sodium perfluoro-octanoate (SPFO)) and catanionic surfactants (decyltrimethylammonium bromide (DeTAB) + SPFO) were simulated. FindingsThe mixture of anionic surfactants, SDS + SPFO, exhibits clear intramicellar segregation between fluorinated and hydrogenated chains, displaying hydrogenous-rich and fluorous-rich regions. Compartmentalized micelles are thus clearly formed. The simulation results also suggest the possibility of intermicellar segregation. Conversely, catanionic mixtures of DeTAB and SPFO in water solution assemble into a large oblate structure, containing all available molecules in the simulation box, resembling a double layer membrane or a vesicle wall. In this case mixing between fluorinated and hydrogenated surfactants is dictated by charge alternation.

Cationic surfactants influencing the enhancement of energy efficiency for perfluorooctanoic acid (PFOA) removal in the electrocoagulation-flotation (ECF) system

From an environmental perspective, approaching sustainability requires a fundamental conceptual shift from the wastewater treatment process toward integrated treatment systems that consider efficient and effective utilization. This study aims to investigate the effects of different surfactants on the removal of perfluorooctanoic acid (PFOA). We used cationic surfactants as both frothers and collectors in the electrocoagulation-flotation (ECF) method to improve the removal efficiency of PFOA. The results showed that, under a monopolar aluminum electrode and with an initial PFOA concentration of 0.25 mM, the ECF method with decyl-trimethyl-ammonium bromide (DTAB) was able to remove over 98% of PFOA within 10 min. Cationic surfactants with a similar linear alkyl chain shape to PFOA, but a longer chain length, are more effective at removing PFOA through the ECF process. The removal mechanism is thought to involve co-precipitation with aluminum hydroxides through Al–F bonding, co-flotation with cationic surfactants, and mixed micelle formation with cationic surfactants. The optimal conditions were tested in both synthetic and realistic wastewater matrices and produced similar results. It has the potential for real wastewater application. The energy yield (G50) of ECF with 5 mM DTAB is 497 g·kWh−1, superior to other treatments, and is an extremely energy-effective method for separating PFOA from wastewater.

A Porous Ni@SiO2 Nanocatalysts for CO2 Methane Reforming

AbstractPorous Ni@SiO core‐shell catalysts (Ni@SiO2‐xC10) were modified by selective etching in a mild alkaline solution using decyltrimethylammonium bromide (C10TAB). The effects of C10TAB concentration on the Ni@SiO2 nanoparticles were explored and used in the dry reforming of methane. It can change the physicochemical properties of Ni@SiO2, and the modified Ni@SiO2‐xC10 exhibits better catalytic performance than Ni@SiO2. TEM, N2‐isotherm, and H2‐TPR results show that Ni@SiO2‐xC10 modified with a sufficient concentration of C10TAB has a mesoporous core‐shell structure, which not only increases the pore volume and surface area but also enhances the metal‐support interaction; XPS and TEM results indicate that Ni nanoparticles are confined within the mesoporous core‐shell, which inhibits the migration of Ni nanoparticles at high temperature. The Ni@SiO2‐2C10 catalyst showed optimal catalytic performance under reaction conditions of 800 °C, N2 : CH4 : CO2=1 : 1 : 1, and WHSV of 126000 mLgcat−1 h−1 with increased conversion of CH4 (>79 %) and CO2 (>84 %) within 50 h.

Effect of 1,2-propanediol on the Critical Micelle Concentration of Decyltrimethylammonium Bromide at Temperatures from 293.15 K to 308.15 K.

It is well known that polar organic compounds, such as alcohols and polyols, exert an appreciable influence on water structure and thus have important effects on surfactant micellization. These substances are often used to modify the properties of surfactants in aqueous solutions, increasing the practical applications they have in diverse industries. In this work, the critical micelle concentration (CMC) of decyltrimethylammonium bromide (C10TAB) in water and in 1,2-propanediol aqueous solutions was determined from both sound velocity and surface tension measurements as a function of surfactant concentration in the temperature range of (293.15 to 308.15) K. The critical micelle concentration of the surfactant increases as the concentration of 1,2-propanediol becomes higher, while the effect on temperature does not show important changes within the range considered. At the selected temperatures, the standard thermodynamic parameters of micellization suggests that the addition of 1,2-propanediol makes the micellization process less favorable. Thermodynamic analysis suggests that the micelle formation of C10TAB is an entropy-driven process at the temperatures considered in this study.

Enhancement of polypyrrole electrochemical performance with graphene quantum dots in polypyrrole nanoparticle/graphene quantum dot composites

• The synthesis of polypyrrole decorated with GQDs in a form of spherical nanoparticles by chemical polymerization in the presence of a surfactant. • The optimization of the polymerization time and amount of GQDs added during the polymerization. • The influence of these factors on the size, dispersibility, textural parameters, and electrochemical properties of composite nanoparticles. • Voltammetric and theoretical studies on the actual influence of GQDs on the electrochemical behavior of polypyrrole nanoparticles. The influence of graphene quantum dots (GQDs) on the physicochemical properties of polypyrrole nanoparticles (PpyNPs) was investigated experimentally and theoretically. The synthesis of the non-covalent PpyNPs/GQDs material was based on the known procedure of chemical pyrrole polymerization in the presence of a strong oxidant (ammonium persulfate, APS) and a surfactant (decyltrimethylammonium bromide, DeTAB). The obtained hybrids were in the form of spherical polymeric particles coated with GQDs with a diameter depending on the polymerization time and the amount of GQDs added during the synthesis. The morphology and porosity of the obtained materials were also influenced by the polymerization conditions, namely, composites with a higher GQD content showed higher BET specific surface area. On the other hand, the greatest attention was paid to the study of electrode processes taking place on the electrode modified with the PpyNPs/GQDs composite compared to the modification with pristine PpyNPs. GQDs incorporated into the polymeric network significantly change the energy level distribution at the interphase between Ppy and GQDs. Electronic interaction between both components results in GQDs participation in the Ppy-involved charge transfer processes. In consequence, oxidation of the mixed PpyNPs/GQDs system is much easier compared to the polymer itself. The charge transfer processes involving PpyNPs/GQDs composites are also much faster than those involving electroactive films formed only from PpyNPs. Additionally, a significant increase in the double-layer capacitance current is observed for composite materials. In conclusion, a clear improvement in the electrochemical behavior of polypyrrole in the composite material was observed, which was undoubtedly the result of the introduction of GQDs.

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.

Evaluation of the inhibitory efficacy of quaternary ammonium compounds on in vitro growth of Theileria equi parasite in MASP culture

Equine piroplasmosis has become a global problem of the equine husbandry sector. Haemoprotozoans evolved very quickly and developed resistance against most of the current available drugs. Phospholipid membrane synthesis by choline kinase enzyme is vital for propagation of intra-erythrocytic protozoa parasites. This pathway was targeted in the present study. Quaternary ammonium salts (QAS) and their analogues act against choline and hamper the biosynthesis process for phosphatidylcholine. We analysed anti-T. equi activity of three QAS - decamethonium bromide (DMB), decyl trimethyl ammonium bromide (DTAB) and dodecyl trimethyl ammonium bromide (DDTAB). Theileria equi parasites in vitro treated with different concentrations of DMB, DDTAB and DTAB. Drug treated T. equi failed to multiply further in the viability test. The IC50 value of DMB, DDTAB and DTAB for growth inhibition of T. equi was 14.0 μM, 469.51 nM and 558.40 nM, respectively. DMB, DDTAB and DTAB treated T. equi parasites were observed to be devoid of internal structures, showing pyknotic and degenerative appearances. Various concentration of DMB, DDTAB and DTAB were analysed for their cytotoxicity and haemolytic activity on horse's PBMCs and RBCs. DMB was less than 10% cytotoxic to PBMCs, while DDTAB and DTAB were 40%–50% cytotoxic at 1000 μM concentrations. The respective CC50 values were 7202.96 μM, 1026.26 μM and 1263.95 μM. DMB and DTAB showed least haemolytic activity (<3%); whereas DDTAB was more haemolytic to RBCs at highest concentration of 2000 μM. The respective CC50 values of these drugs were 224495.3 μM, and 39101.35 μM; 713.54 μM. Specific selective index for DMB, DDTAB and DTAB values with respect to host's PBMC and RBC cells, were 514.50, 2185.81, 2263.52 and 16035.38, 1519.75, 70023.91, respectively. These data indicated its non-toxicity to host's cells and selective potential of anti-T. equi in vitro activity.

Studies of radial distribution function and second virial coefficient for surfactant decyltrimethylammonium bromide in aqueous solutions at 298.15 K: Evidence for cation–cation hydrophobic interactions effect

Excess internal pressure of solution and excess partial molar volume of solute data embedded in the parameter reversible isothermal work (W) have been used to calculate the ion–ion pair correlation functions (gij(r), r being distance) and the thermodynamic properties of aqueous solutions of decyltrimethylammonium bromide (C10TAB) in concentration range 0.01 – 0.14 mol∙kg–1. It is observed that gij(r) exhibits a peak at critical micelle concentration (cmc), while the virial coefficient term (gij(r) – 1) also goes through a maximum. Using Friedman's methodology and McMillan–Mayer theory of solutions, these results have been examined. With the help of concept of Gurney cosphere around the ions, the overlap of solvation shells (water molecules) as the concentration of ions increases have been used to probe water– structure effects as water–structure making/breaking. Coefficients Aij are estimated (Coulombic term, a core repulsive term, a cavity formation term and overlap of cosphere term) at various concentrations of ionic surfactant and at a radial distance of 20 Å for a micellar entity. Further analysis indicates that gij parameter (that is, representing cation–cation interaction g++) dominate over g+– (representing ion–solvent interaction) in solution phase. Thus for a self–assembly process (formation of micelle with aggregation number) in a solution phase is being characterized by a peak in gij(r) function at cmc and aggregation number of ≈ 38, area under the peak, while the virial coefficient variation indicates a dominance of cation–cation interaction and cosphere water–structural effects. It is emphasized that the approach adopted by us to use excess PV work to estimate gij(r) is better to understand the thermodynamic process involved in self–assemblies and micelle formation.

Pool boiling heat transfer enhancement of aqueous solution with quaternary ammonium cationic surfactants on copper surface

Pool boiling is a widely encountered heat transfer phenomenon and the enhancement of boiling heat transfer performance is of vital importance for real applications. Adding surfactant into distilled water is regarded to be a promising and effective approach for heat transfer improvement. The present study selected four kinds of quaternary ammonium cationic surfactants with an increased molecular weight, namely, decyltrimethylammonium bromide (DeTAB), dodecyltrimethylammonium bromide (DoTAB), myristylmethylammonium bromide (MTAB) and cetyltrimethylammonium bromide (CTAB), to investigate the pool boiling performance of their aqueous solutions on a copper heater with and without electric field under different concentrations. Their dynamic surface tensions and viscosities were also measured. The bubble dynamics during pool boiling and apparent contact angle on copper surface before and after boiling test were evaluated. Experimental results reveal that the aqueous surfactant solution can significantly enhance the heat transfer coefficient (HTC) compared with distilled water. The HTC exhibits an increment with concentration until critical micelle concentration (CMC) and then levels off. The maximum relative HTC enhancement can reach up to 209.3%, which is ascribed to the increased nucleate site and bubble departure frequency. In addition to the reduction in surface tension, a repulsion force caused by electrostatic interaction is also responsible for the changes in nucleate site and bubble departure frequency. However, the critical heat flux (CHF) shows a continuous decrement with surfactant concentration. In a low concentration surfactant solution, the CHF is even slightly higher than that of water, which is caused by an improvement in surface wettability after boiling test. The CHF in moderate and high surfactant concentration will be lower. The surfactant with a smaller CMC tends to have a higher HTC and a lower CHF under a low concentration. However, for a relatively high concentration comparative to CMC, the four kinds of quaternary ammonium cationic surfactant solutions tend to have pretty similar boiling curves. The electric field is found to have a negligible influence on the pool boiling performance in aqueous surfactant solutions. Results in present study can provide valuable guidance for surfactant selection during the design of highly effective heat exchangers.

Improved cold‐water detergency of malodourous soil correlating with hydrophilic–lipophilic deviation concept

AbstractThe persistence of sebum after low‐water‐temperature washing can contribute to malodor and microbial growth during subsequent use; thus, this work focuses on improved sebum removal. The detergency of sebum at various hydrophobic–lipophilic deviation (HLD) values was performed using 0.1 w/v% C12‐13‐8PO‐SO4Na and C8‐4PO‐1EO‐SO4Na at 1:1 molar ratio. The detergency of synthetic sebum on 87/13 polyester/spandex was relatively poor (70% removal) at HLD = 0. Various additives (heptanol, dipropylene glycol n‐butyl ether, decyltrimethyl ammonium bromide or sodium benzoate) were explored and it was found that none of them could facilitate sebum removal on the 87/13 polyester/spandex surface. On the other hand, adding low molecular weight primary amines (ethylene diamine, or monoethanolamine [MEA]) in the surfactant system without salt showed sebum removal of 70%–80% depending on the amine molecule. Adding MEA as a detergency additive with salt appeared to achieve good detergency (&gt;80% removal) at all studied HLD numbers between −1.0 and 1.1 and the maximum detergency (approximately 90% removal) was observed at the optimum formulation (HLD = 0). The formulation pH with added MEA decreased from 11 to roughly 9. Detergency performance with added MEA was not dependent on pH within the studied basic conditions. The principal cold water sebum removal mechanism was found to be detachment of solid sebum fractions, dispersed in the detergent bath or floating on the bath surface.

Influence of cetyltrimethylammonium bromide and hydroxide ions on the interfacial tension and stability of emulsions of dodecane in aqueous silicate solutions

This manuscript provides an understanding of the emulsification mechanisms of a model alkane (dodecane) in concentrated aqueous sodium silicate solutions, for e.g. formulating alkane/geopolymer composites for varied applications. To this purpose, we assume that silicate oligomers stabilize the emulsion by positioning themselves at the interface between alkane/aqueous solution. Moreover, the addition of an alkyltrimethylammonium, which interacts with silicate oligomers, is assumed to favor their positioning at the interface to increase the stability of the emulsion by Pickering effect. First, we study the influence of sodium silicate and hydroxide concentrations with up to 6 mol⋅L -1 (NaOH and SiO 2 ) on the interfacial tension (γ) between dodecane and water. Secondly, we study the effect of CetylTrimethyl Ammonium Bromide (CTAB) and DecylTrimethylAmmonium Bromide (DeTAB) on the interfacial tension and the stability of the emulsion. Adding CTAB surfactant leads to partial precipitation but significantly decreases the interfacial tension to less than 4 mN.m -1 . These effects that are not observed with DeTAB. The precipitate corresponds to CTAB-silicates and seems to contribute to the stabilization of the water/dodecane system, presumably through Pickering effect. Moreover, emulsion stability is shown to be related to the condensation/decondensation state of silicate species.

Studies of thermodynamics of micellization and pattern of self-association of decyltrimethylammonium bromide in aqueous solutions at 298.15 K

Using recently reported density, thermal coefficient of expansion and internal pressure data along with the literature osmotic coefficient and enthalpy data and adopting Mass–action model, the properties of decyltrimethylammonium bromide (C10TAB) in water are studied at 298.15 K. The number density, aggregation number, equilibrium constant, standard free energy changes due to micellization, standard entropy changes due to micellization and mean ionic activity coefficient are calculated in pre–micellar and post–micellar regions of concentration assuming that the cationic surfactant C10TAB is fully dissociated in water. Characteristic pattern of association are examined through the models/concepts developed by Tanford, Mukerjee as well as by O. P. Ts’o and noted that hydrophobic interactions between the non–polar chains and water structural effects (in the form of ion–solvent and ion–ion interactions) govern the equilibrium properties of such solutions. The critical micelle concentration (cmc) value and aggregation number value agree with the literature data. It has been observed that aggregation number value decreases slightly, equilibrium constant value goes through a minimum, standard free energy changes due to micellization parameter go through a maximum while positive magnitude of entropy changes due to micellization are observed as a function of concentration of C10TAB. The variation of mean ionic activity coefficient of the salt ions with concentration indicates deviation from ideal–associative solution behaviour. All these results are interpreted on the basis of monomer–micelle equilibria existing in solution phase, affecting the solution properties through electrostatic, hydrophobic solvation and hydrophobic interaction effects.

Studies of internal pressure in aqueous solutions of a surfactant (decyltrimethylammonium bromide) at 298.15 K: Understanding and use of Gibson−Tait equation

Recently reported literature density (ρ), thermal coefficient of expansion (α) data for aqueous solutions of decyltrimethylammonium bromide (C10TAB) in limiting concentration range (0.01 to 0.15 mol kg−1 comprising both pre-micellar and post-micellar regions) have been used and combined with literature density, adiabatic compressibility (βS) and specific heat capacity data (Cp), to calculate isothermal compressibility (βT) and internal pressure (Pi) properties of solutions. The variations of apparent molar adiabatic compressibility (Kϕs) of solute, apparent molar isothermal compressibility (KϕT) of solute and internal pressure (Pi) of solutions are studied and used to obtain infinite dilution parameters such as limiting apparent molar adiabatic compressibility (KϕS0) of C10TAB. The Tammann−Tait−Gibson (TTG) model is applied to calculate the excess volume change for the electrolyte (ΔV¯2E) and intrinsic volume (Vint.) of the cationic surfactant both in pre-micellar and post-micellar regions of concentration. A new method based on internal pressure of solutions and an approach by Tanford incorporating alkyl chain volume, length and head group is developed and used to obtain radius of the micelle and aggregation number. From these data, it is concluded that the micelles are small, spherical and incorporating the surface area of the head group. Our proposed method provides a framework for examining the thermodynamic properties of surfactant in terms of equilibria of the monomer (in limiting range of concentration) and the micelle aggregates after critical micelle formation (cmc) (post-micellar region). In pre-micellar region, water structural changes are important and the hydration of the cations is determined by hydrophobic van der Waal's forces, of which extent increases after cmc, resulting in self-assembly in the form of micelle. Volume changes due to transfer of an electrolyte C10TAB from a liquid hydrocarbon like environment to aqueous solutions and to interior of micelle are also estimated and found to be of positive magnitude.

Prediction of oil/water interfacial tension containing ionic surfactants

This study introduces a new approach to predict interfacial tension (IFT) at oil/water interfaces in the presence of ionic surfactants. Experimental data for sodium dodecylsulphate (SDS), decyltrimethylammonium bromide (C10TAB) and dodecyltrimethylammonium bromide (C12TAB) at hydrocarbon/water interfaces are used to validate the new approach. The model parameters, including molar surface area (ω) and bulk-surface distribution coefficient of surfactant (KS) are obtained by fitting the proposed equation to the literature data. The change of model parameters at different interfaces is discussed. In all cases investigated, the deviation of results for the suggested equations is less than previous work. A good agreement between results and experimental data is obtained in the concentration region below and near the critical micelle concentration.

Improved catalytic performance of mesoporous ZSM-5 nanocrystalline zeolite prepared by the cationic surfactant-ammonium salt mixed agent method in the methanol to gasoline reaction

A mixed organic agent system was employed to achieve mesoporous highly crystalline ZSM-5 zeolite. Decyltrimethylammonium bromide (DeTAB) and tetramethyl ammonium hydroxide (TMAOH) were used as the mesogenous and molecular templates respectively in the synthesis gel with a composition of 60SiO2: 1Al2O3:12Na2O:3150H2O:xDeTAB:8TMAOH. The sole presence of DeTAB as the mesogenous template in the synthesis gel led to the high degrees of mesoporosity in the ZSM-5/xD samples but negatively affected the intrinsic properties of zeolites. At the high concentration of DeTAB (x = 0.7), the mesopore volume dramatically increased while the relative crystallinity and the total acid sites critically decreased. By adding the TMA+ ions as a microporous template to the ZSM-5/0.7D synthesis gel, not only a zeolite with well-developed mesoporosity was obtained but also its crystal structure and the intrinsic acidity were preserved. The catalyst samples were characterized by FESEM, TEM, XRD, FT-IR, nitrogen adsorption–desorption isotherms, NH3-TPD and TGA techniques. The ZSM-5/0.7D/T exhibited higher surface area, higher mesopore volume, higher crystallinity and more acid sites than the ZSM-5/0.7D. The catalytic conversion of methanol to gasoline was conducted in a fixed bed reactor at T = 390 °C and WHSV = 4.74 h−1. In ZSM-5/0.7D/T catalyst the mesoporosity formation without severely damaging the crystal structure and the acidity of the zeolite led to the best catalytic performance including the highest liquid hydrocarbon yield, most stable catalytic performance and longest catalytic lifetime.

Improvements in the enzymatic degradation of textile dyes using ionic-liquid-based surfactants

The intensive use of water containing dyes by the textile industry, and consequently the contamination of soils and water, represents serious environmental concerns. Amongst the several processes applied in the treatment of textile effluents, biological-based processes, if designed to be cost-effective and ecofriendly, are promising alternatives to decolorize textile effluents. In this work we investigate and propose the novel use of ionic liquids (ILs) with surfactant characteristics to improve the degradation of the largely used and highly hydrophobic textile dye indigo carmine (IC) by laccase. An initial screening on the activity of laccase in aqueous solutions of twelve surfactant-based ILs from three different families, namely tetraalkylammonium- and imidazolium-based cationic surfactants and cholinium-based anionic surfactants, at different concentrations, was carried out. Significant improvements in the activity of laccase were observed with decyltrimethylammonium bromide, [N10111]Br, and 1-decyl-3-methylimidazolium chloride, [C10mim]Cl, at 75 mM (above the critical micellar concentration of each IL). These ILs were then investigated in aqueous solutions to simultaneously encapsulate laccase and IC for the in situ enzymatic biodegradation of the dye. The use of ILs remarkably increases the degradation rate of the dye and decolorization efficiency; a degradation efficiency of IC of 82% is attained in 0.5 h using aqueous solutions of [N10111]Br, whereas without IL only 6% of IC is degraded. Furthermore, 93% of the dye decolorization was achieved with [N10111]Br. The overall gathered results show that it is possible to significantly improve the degradation of hydrophobic dyes by enzymes using appropriate surfactant-based ILs, while foreseeing the use of the treated water by the same textile industries in new dyeing steps and thus contributing to a substantial decrease of the economic input and environmental footprint of these industries.