Aqueous Bromide Solutions Research Articles

Sound Velocities and Micellar Behaviour Studies of Dodecyltrimethylammonium Bromide in Aqueous Solutions at 295.15, 302.15 and 309.15 K

Speed of sound, u, of dodecyltrimethylammonium bromide (DTAB) aqueous solutions has been determined at 295.15, 302.15 and 309.15 K. The speeds of sound, u, data have been used to estimate isentropic compressibility, Ks, apparent molal isentropic compressibility, φk(s), acoustic impedance, Z, molal sound of speed, Rm, and relative association, RA, of DTAB in aqueous solution. These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and micellar behavior of DTAB.

LiBr passivation effect of porous nanocrystalline hydrogenated silicon

Nanocrystalline hydrogenated silicon (nc-Si:H) films were deposited on a p-type silicon substrate by plasma enhanced chemical vapor deposition (PECVD), using SiH4 and H2 as reactive gases. Porous (nc-Si:H) layers were afterward obtained and immersed in a lithium bromide (LiBr) aqueous solution in order to enhance their optical and electrical properties for a potential solar cells application. A decrease in the reflectivity to about 9% for Li/porous nc-Si:H layer deposited at 75 sccm against an increase in the minority carrier lifetime were obtained. We correlate these results to the change in crystalline characteristics and chemical composition of the layers in order to understand the effect of LiBr coating on nc-Si:H Through optical and electrical characterization we have demonstrated the possibility of using such LiBr treatment to improve the properties of porous nc-Si:H.

Thermal conductivity measurements of semiclathrate hydrates and aqueous solutions of tetrabutylammonium bromide (TBAB) and tetrabutylammonium chloride (TBAC) by the transient hot-wire using parylene-coated probe

The thermal conductivity of semiclathrate hydrates and aqueous solutions of tetrabutylammonium bromide (TBAB) and tetrabutylammonium chloride (TBAC) was measured for the first time in the temperature range from 223 to 303 K under atmospheric pressure. A transient hot-wire apparatus using a parylene-coated probe was employed for the measurements with an uncertainty of ±0.7%. The experimental results indicate that the thermal conductivity of two semiclathrate hydrates are smaller than those of two clathrate hydrates—about 80% of the THF hydrate and 60% of the CH4 hydrate—and are about a factor of 5.5 lower than that of ice Ih at temperatures near the melting point. In addition, the temperature coefficient of the thermal conductivity of semiclathrate hydrate show a weak negative, and the thermal conductivity is more sensitive to the molar mass of a guest molecule.

Surface tension between CO2 gas and tetra-n-butylammonium bromide aqueous solution

This paper reports experimental values of the surface tension between CO2 gas and tetra-n-butylammonium bromide (TBAB) aqueous solution measured by the pendant drop method. The experimental conditions were pressures from 1.00MPa to 4.00MPa, temperatures from 288.15K to 303.15K and wTBAB from 0.10 to 0.40, where wTBAB denotes the mass fraction of TBAB in the aqueous solution. These pressure–temperature-composition conditions partially fall into the stability zone of (CO2+TBAB) semiclathrate hydrate but all data were obtained without any hydrate in the system. Surface tension decreased with increasing wTBAB and pressure but temperature dependency was not observed. Compared to the air–TBAB aqueous solution system and CO2–water system, the values of the surface tension were smaller.

Functionalization of Titanium Alloy Surface by Graphene Nanoplatelets and Metal Oxides: Corrosion Inhibition.

Corrosion inhibition of metallic substrates is an important and crucial step for great economical as well as environmental savings. In this paper, we introduce an extra thin effective corrosion inhibitive material having layered structure designed for protection and functionalization of Ti Grade 5 alloy substrates. The coating consists of a first layer made of thin graphene nanoplatelets, on top of which a multilayer Al2O3 and TiO2 films is applied by low-temperature atomic layer deposition. The amorphous structure of the metal oxide films was confirmed by micro-Raman and X-ray diffraction analysis. Corrosion inhibition ability of the prepared coatings was analyzed by open circuit potential, potentiodynamic plot and by voltammetric analysis, in aqueous potassium bromide solution. The open circuit potential of the graphene-metal oxide coated substrate showed much passive nature than bare substrate or graphene coated or only metal oxide coated substrates. The localized corrosion potential of the graphene-metal oxide coated, only metal oxide coated, and bare substrates were found 5.5, 3.0, and 1.1 V, respectively. In addition, corrosion current density values of the graphene-metal oxide and only metal oxide coated substrates showed much more passive nature than the bare and graphene coated substrates. Long immersion test in the salt solution further clarified the effective corrosion inhibition of the graphene-metal oxide coated substrate. The analyzed results reflect that the graphene-metal oxide films can be used to prepare better and effective corrosion inhibition coatings for the Ti Grade 5 alloy to increase their lifetime.

Measurement of Latent Heat of Tetra-n-Butyl Ammonium Bromide Hydrate and Specific Enthalpy of Its Slurry

The specific heat of a tetra-n-butyl ammonium bromide (TBAB) aqueous solution, the latent heat of a TBAB hydrate, and the specific enthalpy of a TBAB hydrate slurry were measured to understand the thermal storage characteristics of TBAB hydrate slurry. A solution sample and the hydrate slurry were heated, the change in temperature was measured, and the specific heat of the TBAB aqueous solution and the specific enthalpy of the hydrate slurry were obtained from the change in temperature. Two types of TBAB hydrate form. Therefore, the hydrates were separated from the hydrate slurry formed from TBAB aqueous solution having several initial concentrations. The hydrate crystals were placed into solution, and the latent heats were obtained from the temperature change of the solution. The specific enthalpy of the hydrate slurry was estimated from the latent heats of the hydrate crystals and the specific heat of the solution under phase equilibrium conditions, and the measured and estimated values were compared.

Conductometric and spectroscopic studies of cetyltrimethylammonium bromide in aqueous solutions of imidazolium based ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate

The effect of the addition of the hydrophilic ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4] on the micellization of cetyltrimethylammonium bromide (CTAB) in aqueous solution was studied using electrical conductivity, density, speed of sound and spectroscopic techniques. From the CMC values and their temperature dependence, various thermodynamic parameters such as standard free energy (ΔGm0), enthalpy (ΔHm0) and entropy (ΔSm0) of the micellization were determined in the temperature range of 288.15K to 318.15K. Fourier transform infrared spectroscopy (FTIR) and UV–vis spectroscopy were employed to get information regarding the interaction between the surfactant and ionic liquid aggregates. The calculated thermodynamic parameters |ΔHm0| is smaller than |TΔSm0| which suggests that the micellization is entropy driven.

Experimental measurement and thermodynamic modelling of hydrate phase equilibrium conditions for krypton + n-butyl ammonium bromide aqueous solution

In this study, experimental hydrate dissociation data for krypton in the presence of aqueous solutions of TBAB at varying concentrations of 0, 0.05, 0.10 and 0.20mass fraction TBAB were measured. The measurements were undertaken in the temperature range of (274.1 to 297.1) K and pressures ranging from (0.22 to 11.97) MPa. In addition, semi-clathrate hydrate dissociation data for the TBAB+water system at a pressure of 99.8kPa and at various TBAB concentrations of 0.05, 0.10, 0.20 and 0.30mass fractions were measured. The isochoric pressure-search method was used to undertake the measurements. The purpose of this study was to investigate the effect of TBAB aqueous solution on krypton hydrates. The results reveal that the TBAB aqueous solutions with concentrations of 0.05, 0.10 and 0.20mass fractions show a drastic promotion effect on the krypton hydrate causing a shift of the P-T equilibrium line to lower pressures and higher temperatures. In addition, increasing the TBAB concentration increases its promotion effect. The hydrate dissociation conditions for krypton+water+TBAB system were represented using a model based on the work of Chen and Guo, (Chem. Eng. J. 71 (1998) 145–151) and Joshi et al. (J. Nat. Gas Chem. 21 (2012) 459–465). The model results show a satisfactory agreement with the experimental data, with an absolute relative deviation (ARD%) below 0.3%.

Experimental and modeling study on the phase equilibria for hydrates of gas mixtures in TBAB solution

Accurate calculation of equilibrium formation conditions of hydrates is important for gas storage and separation based on hydrate technology. In this work, the hydrate formation conditions of a synthesized gas mixture in tetra-n-butyl ammonium bromide (TBAB) aqueous solution were measured at temperature ranging from 278.1 to 286.2K. An inflection point in the P–T curve of hydrate phase equilibria was found. It is suggested that the hydrate structures transformed from semiclathrate hydrates to pure structure I hydrates with an increase in formation temperature. Then a thermodynamic model was proposed for calculating formation conditions of the semiclathrate hydrates formed from the gas mixtures+TBAB aqueous solution. The Patel–Teja equation of state was used to calculate the fugacity of gaseous hydrate former and several correlations were used to calculate the properties of TBAB. Ethylene molecules are supposed not to be able to occupy the dodecahedral small cages in the TBAB semiclathrate hydrates under the experimental P–T conditions. The presented model results show good agreement with the experimental data and the literature data.

Ionic liquid and aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of seven rare ginsenosides in Xue-Sai-Tong injection.

A method of ionic liquid salt aqueous two-phase extraction coupled with high-performance liquid chromatography has been developed for the analysis of seven rare ginsenosides including Rg6 , F4 , 20(S)-Rg3 , 20(R)-Rg3 , Rk3 , Rk1 , and Rg5 in Xue-Sai-Tong injection. The injection was mixed with ionic liquid 1-butyl-3-methylimidazolium bromide aqueous solution, and a mixture was obtained. With the addition of sodium dodecyl sulfate and dipotassium phosphate into the mixture, the aqueous two-phase mixture was formed after ultrasonic treatment and centrifuged. Rare ginsenosides were extracted into the upper phase. To obtain a high extraction factors, various influences were considered systematically, such as the volume of ionic liquid, the category and amount of salts, the amount of sodium dodecyl sulfate, the pH value of system, and the time of ultrasonic treatment. Under the optimal condition, rare ginsenosides in Xue-Sai-Tong injection were enriched and detected, the recoveries of seven rare ginsenosides ranged from 90.05 to 112.55%, while relative standard deviations were lower than 2.50%. The developed method was reliable, rapid and sensitive for the determination of seven rare ginsenosides in the injections.

Oil detachment from silica surface modified by carboxy groups in aqueous cetyltriethylammonium bromide solution

Using molecular dynamics simulations, we investigated the process of oil detachment from silica surface modified by carboxy groups in aqueous surfactant (cetyltriethylammonium bromide (CTAB)) solution. It is demonstrated that CTAB molecules promote the formation of water channel between oil molecules and silica surface, which is vital to the detachment of oil drop from silica surface. In this paper, the effects of temperature, surfactant concentration, and calcium ion concentration on the oil detachment from silica surface have been extensively examined. We find that appropriate temperature, surfactant concentration, and calcium ion concentration are crucial for improving oil detachment efficiency. Our study can provide a simple method to design and choose appropriate oil-displacing agents, which is important for its applications in oil recovery, ore floatation, detergency, printing fields, and so on.

Properties and Extraction for [Ni(NH3)6]2+ of ATPS-a Formed by Aqueous Cationic–Anionic Surfactant Mixtures

The properties and extraction for [Ni(NH3)6]2+ of anionic aqueous two-phase systems (ATPS-a) that formed in mixtures of cetyltrimethylammonium bromide (CTAB) and excess sodium dodecyl sulfate (SDS) aqueous solutions were investigated. The results showed that the properties and extraction effects were strongly affected by the surfactant concentration, the temperature of system, and the mole fraction of surfactants. The increase of temperature induces narrower phase region and larger phase volume ratio. In addition, [Ni(NH3)6]2+ was extracted into the surfactant-rich phase with higher distribution coefficient when the liquid crystal had the birefringent properties. Moreover, the distribution coefficient can be improved through reducing the concentration of surfactant from 0.15 to 0.05 mol · L−1 or increasing mole fraction of CTAB from 21.9% to 23.1%. The results showed that ATPS of cationic–anionic surfactants was efficient for [Ni(NH3)6]2+ extraction with distribution coefficients of 13.5 when the total surfactant concentration was 0.05 mol · L−1, mole fraction of CTAB was 21%, and temperature was 34°C.

Crystal Growth of Ionic Semiclathrate Hydrate Formed at the Interface between CO2 Gas and Tetra-n-butylammonium Bromide Aqueous Solution

Formation and growth of ionic semiclathrate hydrate crystals on the surface of a liquid droplet of tetra-n-butylammonium bromide (TBAB) aqueous solution exposed to CO2 gas have been visually observed. Experiments were conducted at a temperature range between 280 and 290 K under the pressure of 2.3 MPa at wTBAB = 0.10 and wTBAB = 0.40, where wTBAB is defined as the mass fraction of TBAB in the aqueous solution. It was found that the hydrate crystals initially grew in the liquid phase, instead of growing at the gas/liquid interface. Then the hydrate grew to form a polycrystalline film covering the droplet only at wTBAB = 0.40. The individual crystals that constitute the polycrystalline hydrate film were observed, and the morphology was classified according to the system subcooling ΔTsub (ΔTsub ≡ Teq – Tex, where Teq is the equilibrium temperature and Tex is the experimental temperature). In all ΔTsub at wTBAB = 0.40, hydrate crystals with step-shaped and thin polygonal-shaped morphologies were observed. The...

Volumetric properties of 1-butyl-3-methylimidazolium bromide in aqueous solutions of d(−)-ribose and d(−)-arabinose at different temperatures

In this work, we report the densities, ρ and apparent molar volumes of imidazolium based ionic liquid (1-butyl-3-methylimidazolium bromide, [Bmim]Br) in water and in aqueous solutions of two pentoses namely d(−)-ribose (Rib) and d(−)-arabinose (Arb) at different temperatures (288.15 to 318.15) K and at atmospheric pressure. The infinite dilution partial molar volume, V2° and empirical parameters (Sv and Bv) were evaluated by using Redlich-Mayer type of equation. The volume of transfer (ΔtV2°) for [Bmim]Br from water to aqueous monosaccharide solutions were found to be positive and decrease in the following order: Rib>Arb. The Sv, Bv ΔtV2° and other parameters such as expansion coefficients and interaction coefficients were discussed in terms of interactions occurring between monosaccharides and ionic liquid. Modulation of volumetric properties of BmimBr in mixed aqueous solutions has also been discussed in relation to the stereochemistry of monosaccharides.

Adsorption and wetting properties of cationic, anionic and nonionic surfactants in the glass-aqueous solution of surfactant-air system

The measurements of the advancing contact angle for water, formamide, glycerol, diiodomethane and aqueous solutions of Triton X-100 (TX-100), Triton X-165 (TX-165), sodium decylsulfate (SDS), sodium dodecylsulfate (SDDS), hexadecyltrimethylammonium bromide (CTAB) and hexadecylpyridinium bromide (CPyB) on the glass surface were carried out. Using the values of the contact angle of these liquids and solutions, the glass surface free energy as well as its components and parameters were determined. This energy, its components and parameters were used for interpretation of the glass wettability by the surfactants solutions in the light of the surfactants adsorption in the three-phase systems and the adhesion of the solution to the glass surface. It appeared that the surface free energy of glass determined from the contact angle of aqueous solution of surfactants on its surface is useful for the determination of the Gibbs surface excess concentration of surfactant at the glass–air and glass–solution interfaces and consequently, the Gibbs standard free energy of surfactant adsorption at these interfaces. It also appeared that by using the Neumann et al. and van Oss et al. equations, it is possible to predict the work of adhesion of aqueous solution of surfactant to the glass surface.

Investigation on the liquid contact angle and its influence for liquid desiccant dehumidification system

The liquid desiccant dehumidification system (LDDS) is promising by removing extra air moisture effectively with absorption. By significantly affecting the film wetted area, the desiccant contact angle of the liquid/air interface on the working plate is critical for the system performance. Its value accuracy also seriously impacts the prediction accuracy of theoretical models. However, previous research on the liquid desiccant contact angle was limited, and the results of current predictions were questionable. This paper tested the contact angle of commonly used desiccants, Lithium Chloride (LiCl) and Lithium Bromide (LiBr) aqueous solution, on the stainless steel plate, and developed empirical formulas for predicting the angle. For both desiccants, the contact angle increased with the solution mass concentration and decreased with temperature. With the increase of plate surface roughness, the angle first increased and then decreased. These parameters showed much obvious effects on the angle of LiCl. For the effect of roughness, the maximum changing rate of LiCl was 0.13°/nm compared with 0.07°/nm of LiBr. Errors between new formulas and experiment ones were acceptable, showing an average absolute error of 12.3% for LiCl and 9.4% for LiBr. Furthermore, the effects of contact angle on the film wetted area were investigated experimentally with a single channel regenerator. When the plate surface was hydrophilic, the initial film width was significantly enlarged, with a rate of −2.0×10−3m per degree, and film contraction along the flow direction was restrained due to the small contact angle. So, the film wetted area increased with an average changing rate of −9.7×10−4m2 per degree, and the mass transfer was effectively enhanced by 2–3 times. Effective measures to reduce the contact angle were also proposed.

Special Effect of Ionic Liquids on the Extraction of Flavonoid Glycosides from Chrysanthemum morifolium Ramat by Microwave Assistance.

A microwave-assisted extraction approach based on ionic liquids of different chain lengths was successfully applied to the extraction of ten flavonoid glycosides from the flowering heads of Chrysanthemum morifolium Ramat. The pretreated sample was quantified by HPLC-ESI-MSn. The main components were identified as flavonoid glycosides, including three luteolin glycosides, three apigenin glycosides, three kaempferide glycosides, and one acacetin glycoside according to the characteristics of the corresponding CID mass spectrometric patterns. Eight ionic liquids from the imidazolium family with different chain lengths, namely, 1-alkyl-3-methylimidazolium bromide, [Cnmim]Br, (n = 2–16) were studied as extraction medium in water. Results indicated that alkyl chain length had an irregular impact on the extraction efficiency. Moreover, the best extraction efficiency was achieved by 1-dodecyl-3-methylimidazolium bromide aqueous solution ([C12mim]Br). Besides the alkyl chain length of the cations, other factors influencing extraction efficiency were systematically investigated, including concentration of the IL solutions, extraction time, matrix-to-solvent ratio and irradiation power.

Experimental analysis of an internally-cooled/heated liquid desiccant dehumidifier/regenerator made of thermally conductive plastic

Internally-cooled dehumidifiers that use liquid desiccant are supposed to be superior to the adiabatic type in terms of solution flow rate, device volume, etc. In the present study, an internally-cooled dehumidifier made of thermally conductive plastic was designed, and it achieved superior corrosion resistance. Its performance was investigated both experimentally and through simulation. An experimental chamber was built for this internally-cooled dehumidifier, and the experimental results in different working conditions were obtained using a lithium bromide (LiBr) aqueous solution. Performance indices including the moisture removal rate, dehumidification/regeneration efficiency, and volumetric mass transfer coefficient were analyzed in conjunction with the inlet parameters. Compared with the internally-cooled dehumidifiers made of metal materials described in the literature, the present analysis indicates that this plastic dehumidifier demonstrated comparable heat and mass transfer performance, providing a feasible approach for an internally-cooled process. In addition, with the help of the experimental results, a numerical model was built and validated for this internally-cooled dehumidifier using liquid desiccant.

CO2 Removal from Biogas Based on Hydrate Formation with Tetra-n-Butylammonium Bromide Solution in the Presence of 1-Butyl-3-Methylimidazolium Tetrafluoroborate

The separation of CO2 by clathrate hydrate formation was considered to be a promising and economically feasible technology compared with the traditional techniques. In this work, we investigated the effect of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) on the separation of CO2 from a 33 mol % CO2/67.0 mol % CH4 gas mixture based on hydrate formation in 0.05 mass fraction tetra-n-butylammonium bromide (TBAB) aqueous solution. The influence of both the [BMIm]BF4 concentration and the operating conditions on the gas separation by hydrate formation was studied. The results showed that the content of methane in the residual gas increased and the time required to reach balance was significantly shortened when the two additives were used in combination. The highest CH4 concentration in the residual gas phase was 84.0%, obtained in TBAB solution with 1200 ppm [BMIm]BF4 at 278 K and 3 MPa by one-stage hydrate separation. The maximum CO2 separation factor of 10.3 was obtained in TBAB solution with 120...

Surface and Micellar Properties of Ionic Liquid 1-Dodecyl-3-methylimidazolium Bromide in Aqueous Solution in the Absence and Presence of a Series of Organic Electrolytes

The surface and micellar properties (including critical micelle concentration (cmc), surface tension at the cmc (γcmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (∏cmc), the maximum surface excess concentration (Γmax), and minimum surface area per molecule (Amin) at the air–liquid interface) of 1-dodecyl-3-methylimidazolium bromide ([C12mim][Br]) ionic liquid in aqueous solutions were studied in the absence and presence of a series of organic electrolytes by surface tensiometry at 298.15 K and 308.15 K. The electrolytes studied include tetraalkylammonium halides, namely, (CH3)4NBr, (C2H5)4NBr, (C3H7)4NBr, (C4H9)4NBr, (CH3)4NCl, and (CH3)4NI. The results show that the surface tensions as well as the cmc values decrease in the presence of the added electrolytes. Therefore, the electrolytes 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 small effect on the salting-out strength. The ability of the anions and cations to promote the aggregation of [C12mim][Br] decreases in the order of I– > Br– > Cl–, and (C4H9)4N+ > (C3H7)4N+ > (C2H5)4N+ > (CH3)4N+, respectively.