Aqueous Bromide Solutions Research Articles

Solubility of Argon and Nitrogen in Aqueous Solutions of Dodecyltrimethylammonium Bromide (DTAB) from 283.15 to 298.15 K and 101325 Pa Partial Pressure of Gas

The solubility of nitrogen and argon in aqueous solutions of dodecyltrimethylammonium bromide (DTAB) were measured, using the drop pressure method, at temperatures between (283.15 and 298.15) K and partial pressure of 101325 Pa of gas in an instrument specially developed for this purpose. The gas solubility was calculated as Henry’s constant. The solubilities of argon and of nitrogen increase linearly with DTAB concentration and decrease as the temperature increases. Experimental results show that the increase in the solubility of argon and nitrogen in the DTAB micelles is between 59.0 and 83.5 higher than the solubility in pure water, reflecting the ability of DTAB micelles to increase the solubility of non-polar gases in water.

Polyoxometalate‐Based Metal–Organic Frameworks as Catalysts for the Selective Oxidation of Alcohols in Micellar Systems

AbstractA series of nanosized metal–organic frameworks (MOFs) encapsulating different polyoxometalates (POMs) including H3PW4O12, H5PMo12O40, H5PVMo10O40, H5PV2Mo10O40, and H5PV3Mo10O40 was synthesized and used in the selective oxidation of alcohols. The catalyst with a uniform size and morphology offered easy accessibility between substrates and catalyst. At the same time, the MOF ensured that the POM was encapsulated, which could dramatically prevent the assembly of the catalyst. Furthermore, the catalyst showed clear chemoselectivity, which was related to the size or accessibility of the substrates for surface pores. With cetyltrimethyl ammonium bromide aqueous solution as solvent, both improved reaction efficiency and simple recycling of the catalytic system were achieved to afford a green oxidation process.

Study of salt effects on the aggregation behavior of ionic liquid 1-dodecyl-3-methylimidazolium bromide in aqueous solution

The effect of organic electrolytes Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, Me4NCl and Me4NI on the aggregation behavior and thermodynamic properties of surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) in aqueous solution was studied by volumetric, compressibility and conductometric measurements at different temperatures. The results show that all the electrolytes investigated effectively reduce critical micelle concentration and therefore have a salting-out effect on the aggregation of [C12mim]Br in aqueous solutions. It was also found that the salting-out-inducing anions are predominately responsible for the observed effect, while the cations have a very smaller effect on the salting-out strength. The ability of the anions to promote the aggregation of SAIL decreases in the order of I−>Br−>Cl−; however all the investigated cations Me4N+, Et4N+, Pr4N+ and Bu4N+ have a similar salting-out strength. Changes in the apparent molar volumes and isentropic compressibilities upon micellization were derived and the infinite dilution apparent molar properties of the monomer form of [C12mim]Br were determined. Furthermore the effect of electrolyte on the degree of anionic binding and the thermodynamic parameters of aggregation for [C12mim]Br in aqueous solutions were determined.

Studies on deposition of gold atomic clusters on to polycrystalline gold electrode from aqueous cetyl trimethyl ammonium bromide solutions

Atomic (molecular) clusters, with less than 50–100 atoms (size ⩽1.5nm) are of special interest and exhibit novel and interesting properties due to quantum confinement of electrons and holes. These properties are quite different from those of gold nanoparticles and hence, understanding of electrochemical phase formation of gold atomic clusters assumes importance. In the present study, we report a detailed investigation of deposition of gold atomic clusters on to polycrystalline gold electrode from aqueous cationic surfactant solutions. The studies were undertaken over a wide range of potentials, covering both surface and bulk layer dissolution and deposition processes, by means of cyclic voltammetric and chronoamperometric techniques. Thus, gold atomic clusters are formed in both surface and bulk layer dissolution and deposition processes as evidenced by AFM, MALDI-TOF, XPS and DLS. Electrocatalytic activity has been performed by the electrochemical reduction of oxygen (O2) on AuAC modified gold electrode in 0.1M H2SO4.

Cellulose dissolution in aqueous lithium bromide solutions

A new all-aqueous process of the dissolution/regeneration of cellulose was developed. Cellulose was completely dissolved in the 54–60 wt% lithium bromide aqueous solutions in the temperature range of 110–130 °C within a dissolution time of 1 h. Then, the cellulose was directly regenerated from the solution by cooling down to approximately 70 °C and removing the salts with water, yielding a translucent gel. The cellulose gel was not significantly chemically decomposed even though some decrease of the degree of polymerization occurred during the dissolution/regeneration of cellulose. The X-ray diffraction analysis demonstrated that the dissolution/regeneration of cellulose induced a crystalline structural change from cellulose I to cellulose II, confirming the complete loss of the original cellulose structure. The cellulose gel had highly porous three-dimensional networks composed of fairly long cellulose fibrils interconnected with one another. The dissolution/regeneration of cellulose in aqueous lithium bromide solutions offers new and important options for cellulose-based materials.

Micellization behavior of the ionic liquid lauryl isoquinolinium bromide in aqueous solution

The micellization behavior of the ionic liquid lauryl isoquinolinium bromide ([C12iQuin]Br) in aqueous solution has been assessed using surface tension, electrical conductivity, and 1H nuclear magnetic resonance (NMR) measurements. The results reveal that the critical micelle concentration (CMC) and constant surfactant tension (γcac) are lower than that of butyl isoquinolinium bromide ([C4iQuin]Br), octyl isoquinolinium bromide ([C8iQuin]Br, and lauryl pyridinium bromide ([C12Pyr]Br). 1H NMR spectra show the evidence of paralleled π-stacking of adjacent isoquinoline rings. To elucidate the effect of the π–π interactions on the aggregation process, thermodynamic parameters such as the standard free energy, enthalpy, and entropy of aggregation have been discussed. These parameters are evaluated from the CMC with temperature by fitting these values to expressions derived from a micellization thermodynamic model. The enthalpy–entropy compensation phenomenon has been observed in the micellization process of [C12iQuin]Br in water, and the presence of isoquinoline cations is responsible for the decrease in the ΔHmic∗, compared with [C12Pyr]Br which has the same alkyl chain and counter-ion.

Effect of temperature and additives on the critical micelle concentration and thermodynamics of micelle formation of sodium dodecyl benzene sulfonate and dodecyltrimethylammonium bromide in aqueous solution: A conductometric study

Specific conductance of (0.3 to 3.0)mmol·kg−1 sodium dodecyl benzene sulfonate (SDBS) and (3.0 to 30.0)mmol·kg−1 dodecyltrimethylammonium bromide (DTAB) has been determined in water and in the presence of (0.01, 0.05 and 0.10)mol·kg−1 aqueous solution of glutamine/histidine/methionine at T=(293.15, 298.15, 303.15, 308.15 and 313.15)K. From the conductivity data, the critical micellar concentration (CMC) and thermodynamic parameters of micellization (ΔGmo,ΔHmo and ΔSmo) have been computed by applying the mass action model. Enthalpy–entropy compensation effect has also been observed. The effect of amino acid on the micellar properties of SDBS and DTAB depends upon their nature, concentration, as well as on temperature and has been used to study the interactions present in the micellar systems. There occurs a gradual increase in the value of CMC with temperature in case of SDBS while in case of DTAB, it passes through a broad minimum and then tends to increase with increase in temperature. Increase of amino acid concentration is found to decrease CMC in both the surfactants. The ΔGmo values are negative and the feasibility of the micellization is found to increase with rise in temperature. The magnitude of hydrophilic and hydrophobic dehydration determines whether the CMC values increase or decrease with rise in temperature.

Equilibrium Hydrate Formation Conditions of CO2 + N2 + SO2 Ternary Simulated Flue Gas in SO2 and Tetra-n-butylammonium Bromide Containing Aqueous Solutions

The equilibrium hydrate formation conditions for ternary simulated flue gas [CO2 (0.1368) + N2 (0.8547) + SO2 (0.0085)] with SO2 aqueous solutions, and SO2 + tetra-n-butyl ammonium bromide (TBAB) aqueous solutions were measured using the temperature search method, over the temperature and pressure range of (272.85 to 283.15) K and (1.20 to 5.09) MPa, respectively. The corresponding equilibrium gas compositions were analyzed. The effects of SO2 concentration and TBAB additive on the hydrate phase equilibrium were studied. For the flue gas and SO2 aqueous solution, the presence of SO2 reduces the hydrate formation pressure. The higher is the SO2 concentration in aqueous solution, the easier the hydrate forms, and the higher the SO2 concentration in equilibrium gas phase is. N2 mole fractions in equilibrium gas phase are higher than that in the feed flue gas, while CO2 is lower due to its relative high solubility. For a given system, the equilibrium hydrates formation pressure increases with the increase in temperature. Both SO2 and N2 mole fractions in equilibrium gas phase decrease with the increase in pressure, while the CO2 mole fraction increases. TBAB solution with w4 = 0.050 not only reduces the equilibrium hydrates formation pressure markedly, but also helps the dissolution of SO2 in aqueous solution. The SO2 concentrations in equilibrium gas phase for the TBAB addition system are much smaller than those without TBAB addition. The pressure reducing effect of the TBAB promoter for SO2 containing flue gas is dependent on the SO2 concentration and smaller than that for flue gas without SO2. A small amount of SO2 produces a synergy with TBAB to promote the hydrate formation, but the high SO2 concentration produces an inhibition on the hydrate formation, and causes the hydrate equilibrium pressure increase. The optimum SO2 mass fraction in solution is lower than 0.010.

Partially oxidized potato starches from bromide‐free TEMPO‐mediated reaction: characterization of monosaccharide composition

Partially oxidized starches were obtained by oxidation of water‐soluble potato starch with the NaOCl/2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) system in the absence of bromide in aqueous solutions at pH 10.2. Monosaccharide composition of the oxidized starches was studied by acid–base titration and NMR spectroscopy, and it was characterized by a content of B units with carboxyl groups (7–73 mol%), C units with C‐6‐aldehyde hydrate groups (5–37%), and non‐oxidized A units (20–88%). The feature of bromide‐free TEMPO‐mediated oxidation of starch was the formation of a significant amount of C units. In addition to monosaccharide composition, compositional heterogeneity of a starch sample with 73% of B units was described by the distribution of triad sequences BBB (54 mol%), ABA (20%), AAB + BAA (12%) and BAB (14%), which were quantified by NMR spectroscopy.

Thermodynamics of the interactions of some amino acids and peptides with dodecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide

The values of apparent molar volume V2,ϕ and apparent molar adiabatic compressibility KS,2,ϕ of amino acids glycine, l-alanine, dl-α-amino-n-butyric acid, l-valine, l-leucine and peptides glycyl-glycine, glycyl-glycyl-glycine and glycyl-leucine have been determined in aqueous solutions of cationic surfactants dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) by means of density and sound velocity measurements. The heat evolved or absorbed (q) during the course of interactions of amino acids and peptides with the aqueous solutions of surfactants were determined by isothermal titration calorimetry at T=298.15K. The values of standard partial molar volume V2,m0 and standard partial molar adiabatic compressibility Ks,2,m0 at infinite dilution were calculated from the values of V2,ϕ and KS,2,ϕ. Similarly the values of limiting enthalpies of dilution (ΔdilH0) of the amino acids/peptides were calculated from heat evolved or absorbed during calorimetric experiments. The standard partial molar quantities of transfer from water to aqueous surfactant solutions have been used to identify the interactions of amino acids and peptides with surfactants in terms of ionic–ionic, ionic–hydrophobic and hydrophobic–hydrophobic group interactions.

Synthesis and Properties of N,N′-Bis(Sodium Lauryl Acyl Proyl Acid) Ethylenediamine

Abstract The Gemini surfactant, N,N′-bis(sodium lauryl acyl proyl acid) ethylenediamine, was synthesized and symbolized as DLMC. The surface chemical properties and micellar behavior of DLMC with polyethylene oxide lauryl ether (C12E6) in 0.1 mol · L−1 sodium bromide aqueous solution were investigated by surface tention measurements at 298 K. The critical micelle concentration (cmc) of DLMC is 1.01 × 10−4 mol L−1, and the cmc values of the binary surfactant system are all lower than those of pure constituent surfactants. The interaction parameter β of the binary surfactant system was calculated, which indicates the existence of synergism in surface tension reduction efficiency, mixed micelle formation and surface tension reduction ability.

Heat Capacities of Four Promising Alternatives to Lithium Bromide Aqueous Solution in Absorption Refrigerators

Properly choosing additives to conventional lithium bromide aqueous solution to improve the performance is an important part in lithium bromide absorption refrigeration studies. Mixtures consisting of lithium bromide + triethylene glycol + water, lithium bromide + propylene glycol + water, lithium bromide + sodium formate + water, and lithium bromide + potassium formate + water were thought to be four promising alternatives to lithium bromide aqueous solutions. In the study, heat capacities of the four kinds of solutions were measured using a calvet type calorimeter at temperatures from 308.15 K to 348.15 K. The experimental data were regressed using a stepwise statistical method, and the corresponding equations for each kind of solution were given. The average absolute deviations between experimental and calculated values were no more than 0.12 % for all of the systems.

Photodecomposition of dodecyltrimethylammonium bromide in aqueous solutions in presence of hydrogen peroxide

It is established that the cationic surfactant (dodecyltrimethylammonium bromide, DTAB) efficiently decomposes in an aqueous solution in the presence of H2O2 upon exposure to UV radiation. The presence of bicarbonate ions decreases the rate of photodecomposition, which is due to the acceptance of OH radicals generated in the photochemical reaction. The rate constant of OH radicals and DTAB reaction equals ∼109 L mol−1 s−1. The kinetics of DTAB decomposition are described by the first-order reaction equation, and the effective rate constant is proportional to the H2O2 content in the solution.

Aqueous solutions of the double chain cationic surfactants didodecyldimethylammonium bromide and ditetradecyldimethylammonium bromide with Pluronic F68: Dynamic surface tension measurements

The adsorption kinetics of mixtures of the non-ionic copolymer Pluronic F68 with two double chain cationic surfactants didodecyldimethylammonium bromide (di-DDAB) and ditetradecyldimethylammonium bromide (di-TDAB) is studied with dynamic surface tension experiments. A time dependent synergy is observed, in most of the mixtures. In a few cases, hindrance effects are observed. Clusters are formed at concentrations well below the critical micelle concentration (cmc), at the critical aggregation concentration (cac). The presence of the copolymer stabilizes the electrostatic repulsion between the positively charged quaternary ammonium headgroups of di-DDAB and di-TDAB. The electrostatic repulsion between the polar parts of the same and adjacent surfactant molecules is minimized. We compare our results with recently published results, using mixtures of these double chain cationic surfactants with hydroxypropylmethylcellulose.

Self-assembly into temperature dependent micro-/nano-aggregates of 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin

Various nanostructures of 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin (H2TCPP) can be easily synthesized by a surfactant-assisted self-assembly (SAS) method at different temperatures. When the DMF solution of porphyrin monomer was injected into cetyltimethylammonium bromide (CTAB) aqueous solution by a syringe, diverse H2TCPP nanostructures dependent on the different temperatures, including hollow nanospheres, solid nanospheres and nanospheres with holes, were successfully obtained. As a result, the suitable concentration of the CTAB aqueous solution used to form nanostructues of porphyrin ranges from 0.15 to 0.2mM. The various morphologies of porphyrin nanostructures were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). UV–vis adsorption spectra showed that the micro-/nano-aggregate properties of porphyrin transformed from H-aggretates to J-aggregates during the process of self-assembly of porphyrin at different temperatures. Fluorescence spectra revealed a greater fluorescence quenching of various micro-/nano-aggregatess of porphyrin formed at different temperatures in aqueous solution, compared to the DMF solution of porphyrin monomer.

Enhanced Surface Partitioning of Nitrate Anion in Aqueous Bromide Solutions.

The proximity of nitrate anions to the air-water interface is thought to strongly influence their photodissociation quantum yield, due to a reduced solvent cage effect at the water surface. Although nitrate in aqueous solution exhibits little or no surface affinity, the release of gas phase NO2 (nitrate's primary photodissociation product) has been reported to be enhanced when halides, in particular bromide, are also present in solution. Here, we use glancing-angle Raman spectroscopy to investigate whether solutions containing both nitrate and halides show different propensities for nitrate at the air-water interface. We find that bromide enhances, and chloride has little effect on (or perhaps suppresses) the surface partitioning of nitrate anions.

Aqueous biphasic formation, volumetric and compressibility behaviour in tetrabutylammonium bromide-inorganic salts aqueous systems

Phase diagrams for several (salt+salt) aqueous biphasic systems containing tetrabutylammonium bromide and inorganic salts NaH2PO4, Na2HPO4, Na3PO4, Na2CO3, K3Cit and Na2SO4 were determined at T=(298.15, 308.15 and 318.15)K. The salting-out strength of the investigated kosmotropic salts on the tetrabutylammonium bromide (chaotropic salt) in aqueous solutions follows the well established Hofmeister series, as in the case of (polymer+salt) aqueous biphasic systems. In order to obtain further evidence about the salting-out effect in these systems, volumetric and compressibility behaviour of tetrabutylammonium bromide aqueous solutions were also determined in the absence and presence of the investigated inorganic salts at different temperature. It was found that there is a relation between the relative concentration of various salts to form two-phase system with tetrabutylammonium bromide and the apparent molar volume or isentropic compressibility of transfer of tetrabutylammonium bromide from water to aqueous solution of the investigated salts.

Water Structure Modification by Sugars and Its Consequence on Micellization Behavior of Cetyltrimethylammonium Bromide in Aqueous Solution

Water structure modification by sugars with a wide difference in stereoregular structures ranging from monosaccharide to trisaccharide and its consequence on the micellization behavior of cetyltrimethylammonium bromide (CTAB) in aqueous medium have been investigated. The characteristic variation in water absorption peaks in the presence of d(−)fructose has been studied by near-infrared spectroscopy. The analyses show that the hydrogen bonding capability of d(+)glucose, d(−)fructose, sucrose, trehalose and raffinose is mainly responsible for the variation in water-additive interactions. The critical micelle concentration determined by specific conductivity measurement and aggregation number determined by steady state fluorescence quenching method show significant variations in presence of additives for CTAB in aqueous solution. The sugars interact with the water structure to varying extents owing to differences in hydrogen bonding capability depending on the stereoregularity of the structure. This induces differences in the microenvironment for competition between the hydrophobic interaction and degree of hydration of the hydrophilic group of the surfactant to ultimately influence the micellization behavior in aqueous solution.

The Effect of NaCl on the Krafft Temperature and Related Behavior of Cetyltrimethylammonium Bromide in Aqueous Solution

AbstractThis paper presents the effect of NaCl on the Krafft temperature (TK), surface adsorption and bulk micellization of cetyltrimethylammonium bromide (CTAB) in aqueous solution. The critical micelle concentration (CMC) of CTAB in the presence of NaCl increased and then decreased with increasing temperature. Thus, the CMC–temperature data can be represented by a bell‐shaped curve. The micellar dissociation (fraction of counterion binding) and energetic parameters (free energy, enthalpy and entropy changes) of both adsorption and micellization were calculated. The processes were found to be both enthalpy and entropy controlled and appeared to be more and more enthalpy driven with increasing temperature. An enthalpy–entropy compensation rule was observed for both adsorption and micelle formation. The TK of the surfactant decreased significantly in the presence of NaCl, which is a sharp contrast to the usual behavior of the effect of electrolytes on the TK of classical ionic surfactants. The surface excess concentrations decreased with increasing temperature. However, the values were much higher in the presence of NaCl compared to the corresponding values in pure water. The solubilization behavior of a water‐insoluble dye, Sudan red B (SRB), in the micellar system was studied by the UV–visible spectrophotometric technique. The molar solubilization ratio in the presence of NaCl was found to be about three times higher than that in pure water, indicating that the solubilization of SRB in the CTAB micelles significantly increases in the presence of NaCl.

A novel approach for selective cross aldol condensation using reusable NaOH-cationic micellar systems

The efficiency of NaOH-cationic micellar systems was demonstrated for selective cross aldol condensation of benzaldehyde with n-heptanal (as model reaction, which involves cross and self condensation reactions) in equimolar amount to synthesize jasminaldehyde (cross product) with high selectivity. In comparison of biphasic reactions in NaOH aqueous solution (in absence of surfactant), the aldol reactions in NaOH-micellar solution were faster and selective to cross product without consumption of NaOH. The reaction rate and jasminaldehyde selectivity was observed to be influenced by surfactant concentration and reaction temperature. The equimolar reaction of both aldehydes in NaOH-cetyltrimethyl ammonium bromide (CTAB: 200mM) aqueous solution resulted to highest conversion of n-heptanal (99%) with 90% selectivity to jasminaldehyde within 4h. The reusability of NaOH-CTAB system was examined for five reaction cycles.