Benzene In Aqueous Solutions Research Articles

Synthesis of Silica-Coated Uranium Oxide Nanoparticles by Surfactant-Templated Sol-Gel Process for Use as Catalysts

Uranium oxide (U3O8) nanoparticles were synthesized and coated in situ with porous, mesostructured silica using a modified sol-gel method for use as a catalyst. The catalytic property of coated U3O8 nanoparticles was evaluated by exposing them to an aqueous solution of benzene at 500 mg/l at room temperature. The presence of benzene was not detected by an ultraviolet (UV)-visible (UV-vis) spectrometer after 6 weeks of exposure to coated uranium oxide nanoparticles, indicating the particles’ potential as a catalyst. Based on the results of the benzene destruction, it may be suggested that the coated U3O8 nanoparticle-based catalyst has the potential to destroy hydrocarbons, aromatics, and various toxic substances such as perchlorates and 1,4-dioxane from groundwater. However, further experiments are necessary to explore the full potential of the catalyst. Pluronic-123, n-butanol, and 2-propanol were used as surfactant, cosurfactant, and continuous phase, respectively, for the synthesis of the U3O8 nanoparticles, which were formed through nucleation, growth, and subsequent aggregation in the solution phase. The nanoparticles were coated in situ using an aqueous solution of tetraethyl orthosilicate. The coated particles were characterized using transmission electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, nitrogen physisorption, X-ray diffraction, and diffuse reflectance UV-vis spectroscopy. These measurements revealed that U3O8 particles ranging from 4- to 10-nm were distributed exclusively inside the silica matrix.

Ice Growth from Supercooled Aqueous Solutions of Benzene, Naphthalene, and Phenanthrene

Classical molecular dynamics (MD) were performed to investigate the growth of ice from supercooled aqueous solutions of benzene, naphthalene, or phenanthrene. The main objective of this study is to explore the fate of those aromatic molecules after freezing of the supercooled aqueous solutions, i.e., if these molecules become trapped inside the ice lattice or if they are displaced to the QLL or to the interface with air. Ice growth from supercooled aqueous solutions of benzene, naphthalene, or phenanthrene result in the formation of quasi-liquid layers (QLLs) at the air/ice interface that are thicker than those observed when pure supercooled water freezes. Naphthalene and phenanthrene molecules in the supercooled aqueous solutions are displaced to the air/ice interface during the freezing process at both 270 and 260 K; no incorporation of these aromatics into the ice lattice is observed throughout the freezing process. Similar trends were observed during freezing of supercooled aqueous solutions of benzene at 270 K. In contrast, a fraction of the benzene molecules become trapped inside the ice lattice during the freezing process at 260 K, with the rest of the benzene molecules being displaced to the air/ice interface. These results suggest that the size of the aromatic molecule in the supercooled aqueous solution is an important parameter in determining whether these molecules become trapped inside the ice crystals. Finally, we also report potential of mean force (PMF) calculations aimed at studying the adsorption of gas-phase benzene and phenanthrene on atmospheric air/ice interfaces. Our PMF calculations indicate the presence of deep free energy minima for both benzene and phenanthrene at the air/ice interface, with these molecules adopting a flat orientation at the air/ice interface.

Solvation free energies and hydration structure of N-methyl-p-nitroaniline

Solvation Gibbs energies of N-methyl-p-nitroaniline (MNA) in water and 1-octanol are calculated using the expanded ensemble molecular dynamics method with a force field taken from the literature. The accuracy of the free energy calculations is verified with the experimental Gibbs free energy data and found to reproduce the experimental 1-octanol∕water partition coefficient to within ±0.1 in log unit. To investigate the hydration structure around N-methyl-p-nitroaniline, an independent NVT molecular dynamics simulation was performed at ambient conditions. The local organization of water molecules around the solute MNA molecule was investigated using the radial distribution function (RDF), the coordination number, and the extent of hydrogen bonding. The spatial distribution functions (SDFs) show that the water molecules are distributed above and below the nitrogen atoms parallel to the plane of aromatic ring for both the methylamino and nitro functional groups. It is found that these groups have a significant effect on the hydration of MNA with water molecules forming two weak hydrogen bonds with both the methylamino and nitro groups. The hydration structures around the functional groups in MNA in water are different from those that have been found for methylamine, nitrobenzene, and benzene in aqueous solutions, and these differences together with weak hydrogen bonds explain the lower solubility of MNA in water. The RDFs together with SDFs provide a tool for the understanding the hydration of MNA (and other molecules) and therefore their solubility.

The development of a revised version of multi-center molecular Ornstein–Zernike equation

Ornstein–Zernike (OZ)-type theory is a powerful tool to obtain 3-dimensional solvent distribution around solute molecule. Recently, we proposed multi-center molecular OZ method, which is suitable for parallel computing of 3D solvation structure. The distribution function in this method consists of two components, namely reference and residue parts. Several types of the function were examined as the reference part to investigate the numerical robustness of the method. As the benchmark, the method is applied to water, benzene in aqueous solution and single-walled carbon nanotube in chloroform solution. The results indicate that fully-parallelization is achieved by utilizing the newly proposed reference functions.

Chemical Dosimetry System for γ-Ray Irradiation Based on the Formation of Phenol from Aqueous Benzene Solutions

A chemical dosimetry system based on the radiochemical formation of phenol from aqueous benzene solutions was applied to measure the intensity of γ-ray irradiation. Using a simple and sensitive isocratic fluorometric HPLC system, radiochemically generated phenol was determined. The radiochemical formation of phenol was linear up to 100 Gy and the lower limit of detection calculated from the detection limits of phenol was estimated to be 7 mGy. The phenol formation rates were not affected by the oxygen saturation. The chemical dosimetry system investigated in this study was sensitive and was easier to use than traditional chemical dosimeters.

Effect of Temperature on BTEX Permeation Through HDPE and Fluorinated HDPE Geomembranes

ABSTRACT The diffusion characteristics of high density polyethylene (HDPE) geomembranes with respect to hydrocarbons are investigated at temperatures of 22±1°C and 6±1°C. Results are reported for an aqueous solution of benzene, toluene, ethylbenzene, and xylene (BTEX). The partitioning coefficient obtained from sorption/immersion test is shown to be effectively the same as that from desorption test. Both conventional untreated (HDPE) and fluorinated (f-HDPE) geomembranes are examined and it is shown that a fluorinated layer on the surface of an HDPE geomembrane increases its resistance to the permeation of BTEX penetrants by about a factor of 2.4 at 22°C and 1.8 at 6°C. An Arrhenius relationship is developed that could be used for estimating hydrocarbon permeation at different temperatures between 6°C and 22°C for both the HDPE and f-HDPE geomembranes examined.

Pervaporation Characteristics in Removal of Benzene from Water through Polystyrene-Poly (Dimethylsiloxane) IPN Membranes

This paper focuses on the effects of the PSt content of polystyrene (PSt)-poly (dimethylsiloxane) (PDMS) interpenetrateing network (IPN) polymer membranes, on the pervaporation (PV) characteristics during the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05wt% benzene was permeated through the PSt-PDMS IPN membranes, they showed high benzene/water selectivity. Both the permeability and the benzene/water selectivity of the membranes were enhanced with increasing PSt content in the PSt-PDMS IPN membrane. The physicochemical mechanism of permeation and separation through the PSt-PDMS IPN membranes during PV is also discussed. The best normalized permeation rate, separation factor for benzene selectivity, and PV separation index of the PSt-PDMS IPN membrane were 1.27 × 10-6 kgm (m2hr)-1, 3293, and 41821, respectively. These PV characteristics are discussed from the viewpoint of the chemical and physical structure of the PSt-PDMS IPN membranes.

Permeation of organic contaminants through PVC pipes

Permeation of benzene, toluene, and trichloroethylene (TCE) through polyvinyl chloride (PVC) pipes from vapor and aqueous phases was investigated using pipe‐bottle tests, gravimetric sorption tests, and microscopic visualization tests. Vapors of the three compounds at saturated vapor pressures were found to permeate 1‐in. PVC pipes within 30 days; saturated aqueous solutions of benzene and TCE also permeated 1‐in. PVC pipes but at breakthrough times ranging from 60 to 240 days, depending on mixing conditions. For PVC pipes exposed to organic vapors that were in equilibrium with ∤ 40% v/v benzene or toluene in National Institute of Standards and Technology reference fuel and to water containing ∤ 60% of the aqueous solubility of benzene and toluene, insignificant sorption and no moving front were detected. Test results suggest that PVC pipe materials are an effective barrier against the permeation of benzene, toluene, ethylbenzene, and xylenes in either gasoline vapors or gasoline‐contaminated groundwater at typical contaminated sites.

Study on Foaming Properties and Dynamic Surface Tension of Sodium Branched-alkyl Benzene Sulfonates

Foaming properties and the dynamic surface tension (DST) were carried out with aqueous solutions of sodium branched-alkyl benzene sulfonates to elucidate the relationship between foaming properties and surfactant structures. The parameters of the DST (t*, n, R 1/2 ) are correlated with the foaming ability for alkyl benzene sulfonates with benzene ring substituting at positions 2, 4, and 8 of hexadecane. The parameters of the DST (t*, n, R 1/2 ) are correlated with the foaming ability of the same surfactant solutions. The results indicated that the molecular diffusion in the solution, adsorption, and arrangement at the air/water interface were changed with different molecular structures: changing the substituted position of benzene ring from 2 to 8 of hexadecane, the value of t* and n decrease, and the value of R 1/2 increases, which lead to the high dynamic surface activity and high foam volume. The foam stability is correlated with the high surface dilational elasticity and the strength of surface monolayer: changing the substituted position of benzene ring from 2 to 8 of hexadecane, the branched-alkyl chain becomes more flexible, which is characterized by densely packed adsorbed molecules and high film elasticity of the adsorption film. Therefore, the foam stability increases.

Rapid hydrocarbon analysis using a miniature rectilinear ion trap mass spectrometer

A miniature ion trap mass analyzer was applied to the analysis of traces of hydrocarbons and simple heteroatomics in the vapor phase and in aqueous solution. Vapors of acetone, acetic acid, acetonitrile, benzene, butanethiol, carbon disulfide, hexane, dichloromethane, naphthalene, toluene and xylenes were detected and quantified using solid sorbent trapping and, in some cases, by passage through a membrane interface. Aqueous solutions of benzene, toluene, xylenes, hexane and a petroleum naphtha distillate were examined using the membrane interface. Sampling, detection and identification of all compounds was completed in times of less than one minute. The gas-phase samples of toluene and benzene were detected at 200 ppt (limit of detection, LOD) for toluene and 600 ppt for benzene. Identification of benzene and xylene in aqueous solutions was readily achieved with LODs of 200 and 400 ppb, respectively. Quantification over a linear dynamic range of two orders of magnitude for the aqueous samples and three orders of magnitude for the vapor-phase samples was demonstrated.

One-Step Hydroxylation of Benzene to Phenol Induced by Glow Discharge Plasma in an Aqueous Solution

Direct phenol synthesis from benzene in aqueous solution where water was used as the oxidant through glow discharge plasma (GDP) process was described for the first time. The effect of pH, ferrous and cupric ions on the phenol yield and selectivity was examined. Phenol yield of 8.3% and selectivity of 81% has been achieved.

Contaminant Detection, Identification, and Quantification Using a Microchip Laser Fluorescence Sensor

This paper describes a series of laboratory tests conducted to assess the performance of a novel fluorescence-based in situ sensor for environmental contaminants. The sensor, which can be deployed downhole in a monitoring well, or incorporated into the shaft of a cone penetrometer, is less than 4cm in diameter and uses a miniature microchip laser that produces ∼200ps pulses of ultraviolet radiation at a high repetition rate (∼10kHz) to excite fluorescence in a wide range of compounds. Results from laser induced fluorescence tests on single compound aqueous solutions of benzene, toluene, and o-xylene (BTX) demonstrate the sensor’s ability to perform contaminant analyses on compounds with fluorescence lifetimes on the order of 1ns. A linear relationship between contaminant concentration and fluorescence intensity was observed for concentrations over several orders of magnitude from the sensor’s detection limit (<1ppm for o-xylene) to solutions of pure BTX compounds at aqueous solubility. Owing to the microchip laser’s short pulse length, fluorescence lifetimes were obtained directly from measurements without the need for spectral deconvolution. Analysis of data from these tests highlights the importance of differentiating a sensor’s ability to detect, identify, and quantify compounds of interest—performance thresholds that ultimately define potential applications for the device.

Comparison of Energy Efficiency of Various Ultrasonic Devices in Aquasonochemical Reactions

AbstractFor economic reasons, reaction rate and energy efficiency of ultrasonic devices need to be higher. In this investigation, it was found that the 850 kHz ultrasonic device achieves a higher energy efficiency and a higher sonochemical reaction rate than the 24 or 30 kHz device during the oxidation of KI or the degradation of benzene in aqueous solutions. Moreover, lower power intensity or higher power density is generally favorable to the oxidation of KI. For benzene degradation, however, energy efficiency is enhanced with the increase in power intensity and density at lower input power and decreases with the increase in power intensity and density at higher input power. In addition, energy efficiency can also be diminished by changing fluid motion, for example, shortening the distance between the tip of the ultrasonic horn and the reactor bottom, and stirring during sonication.

Solubility data for benzene in aqueous solutions of methyldiethanolamine (MDEA) and of diglycolamine (DGA)

Specially designed equipment based on a static-analytic method with Rolsi™ pneumatic samplers for on line gas chromatograph analysis has been used for this work. Operating pressures and temperatures are between 0.3 and 10 MPa and between 293 and 393 K. Vapor pressures over liquid–liquid mixtures and benzene solubility data are reported herein for benzene with amine aqueous solutions (methyldiethanolamine (MDEA) and diglycolamine (DGA)). Modelling of solubility data is achieved using a simple model based on activity coefficients.

Effects of Fluorine-Containing Graft and Block Copolymer Additives on Removal Characteristics of Dilute Benzene in Water by Microphase-Separated Membranes Modified with These Additives

This paper focuses on the effects of the addition of fluorine-containing graft or block copolymer additives composed of 1H,1H,2H,2H-heptadecafluorodecyl acylate (perfluoroalkyl acylate, PFA) and poly(dimethylsiloxane) macromonomer (PDMS) or PDMS macro-azo-initiator to a microphase-separated membrane consisting of PDMS and poly(methyl methacrylate) (PMMA) on the benzene/water selectivity for an aqueous dilute benzene solution during pervaporation and the surface characteristics and structures of the surface-modified PMMA/PDMS membranes. The addition of the fluorine-containing copolymer additives, PFA-g-PDMS and PFA-b-PDMS, to a PMMA-g-PDMS membrane yielded hydrophobic surfaces at the air side of surface-modified membranes due to the localization of their additives on the air-side surface of these membranes. The addition of a small amount of the PFA-g-PDMS and PFA-b-PDMS enhanced both the benzene/water selectivity and the permeability for an aqueous dilute benzene solution during pervaporation because of the formation of their hydrophobic surfaces and the existence of the microphase-separated structures with a continuous PDMS phase in the inner of these membranes. When larger amounts of the PFA-g-PDMS and PFA-b-PDMS were added to a PMMA/PDMS, the latter additive could keep the microphase-separated structures with a continuous PDMS phase, but the former did not. The relationship between the permeation and separation characteristics for the removal of benzene from an aqueous benzene solution and the structures the PMMA-g-PDMS membranes surface-modified with PFA-g-PDMS and PFA-b-PDMS as fluorine-containing polymer additives is discussed in detail.

Mode-coupling study on the dynamics of hydrophobic hydration II: Aqueous solutions of benzene and rare gases

The dynamic properties of both the solute and solvent of the aqueous solution of benzene, xenon and neon are calculated by the mode-coupling theory for molecular liquids based on the interaction-site model. The B-coefficients of the reorientational relaxation and the translational diffusion of the solvent are evaluated from their dependence on the concentration of the solute, and the reorientational relaxation time of water within the hydration shell is estimated based on the two-state model. The reorientational relaxation times of water in the bulk and within the hydration shell, that of solute, and the translational diffusion coefficients of solute and solvent, are calculated at 0-30 degrees C. The temperature dependence of these dynamic properties is in qualitative agreement with that of NMR experiment reported by Nakahara et al. (M. Nakahara, C. Wakai, Y. Yoshimoto and N. Matubayasi, J. Phys. Chem., 1996, 100, 1345-1349, ref. 36), although the agreement of the absolute values is not so good. The B-coefficients of the reorientational relaxation times for benzene, xenon and neon solution are correlated with the hydration number and the partial molar volume of the solute. The proportionality with the latter is better than that with the former. These results support the mechanism that the retardation of the mobility of water is caused by the cavity formation of the solute, as previously suggested by us (T. Yamaguchi, T. Matsuoka and S. Koda, J. Chem. Phys., 2004, 120, 7590-7601, ref. 34), rather than the conventional one that the rigid hydration structure formed around the hydrophobic solute reduces the mobility of water.

Structural Design of P(BMA-co-VTES)/TEOS Hybrid Membranes for Removal of Benzene from Water by Pervaporation

Summary: The pervaporation performance of optimized poly(butylmetacrylate-co-vinyltriethoxysilane)/tetraethoxysilane (P(BMA-co-VTES)/TEOS) hybrid membranes for the removal of benzene from water was investigated. P(BMA-co-VTES)/TEOS hybrid membranes prepared by the sol–gel reaction were modified by annealing and trimethylsilylation to enhance the performance of these membranes. The annealing and trimethylmethoxysilane (TMS)-modifications of P(BMA-co-VTES)/TEOS hybrid membranes gave more hydrophobic membranes compared with untreated P(BMA-co-VTES)/TEOS hybrid membranes and, consequently, the amount of benzene sorbed in the modified P(BMA-co-VTES)/TEOS hybrid membranes increased significantly. When an aqueous solution of dilute benzene was permeated by pervaporation through the annealed and TMS-modified P(BMA-co-VTES)/TEOS hybrid membranes, the annealing treatment enhanced the benzene/water selectivity significantly. This result was attributed to a decrease in residual silanol groups in the annealed hybrid membranes and the formation of an optimum cross-linked structure of the annealed P(BMA-co-VTES)/TEOS hybrid membranes. Benzene concentration in the permeate for an aqueous solution of benzene through untreated (○) and annealed (•) P(BMA-co-VTES)/TEOS hybrid membranes during PV.

Organic‐Inorganic Hybrid Membranes for Removal of Benzene from an Aqueous Solution by Pervaporation

AbstractSummary: Preparation of organic‐inorganic hybrid membranes and their pervaporation permeation and separation characteristics for an aqueous solution of 0.05 wt.‐% benzene are described. In this study, we prepared organic‐inorganic hybrid membranes by the sol‐gel reaction of tetraethoxysilane (TEOS) as an inorganic component with poly(methyl methacrylate‐co‐vinyltriethoxysilane) (P(MMA‐co‐VTES)) and poly(butyl methacrylate‐co‐vinyltriethoxysilane) (P(BMA‐co‐VTES)) as organic components. When an aqueous solution of dilute benzene (0.05 wt.‐%) was permeated through the P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes, the benzene concentration in the permeate through all hybrid membranes was higher than that in the feed solution. This result demonstrates that these hybrid membranes are benzene selective for an aqueous solution containing dilute benzene. The benzene/water selectivity of the P(BMA‐co‐VTES)/TEOS hybrid membrane was about 20 times higher than that of the P(MMA‐co‐VTES)/TEOS hybrid membrane. Specifically, the P(BMA‐co‐VTES)/TEOS hybrid membrane with a TEOS content of 75 mol‐% showed the highest benzene/water selectivity. The benzene/water selectivity of the hybrid membranes depended significantly on the cross‐linked structures formed by the sol‐gel reaction of VTES and TEOS.Effects of the TEOS content on the sorption selectivity (○) and the diffusion selectivity (•) for an aqueous solution of 0.05 wt.‐% benzene through P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes at 40 °C.magnified imageEffects of the TEOS content on the sorption selectivity (○) and the diffusion selectivity (•) for an aqueous solution of 0.05 wt.‐% benzene through P(MMA‐co‐VTES)/TEOS and P(BMA‐co‐VTES)/TEOS hybrid membranes at 40 °C.

Cross-linked smart poly(dimethylsiloxane) membranes for removal of volatile organic compounds in water

This paper focuses on the effects of fluorine cross-linker of the cross-linked poly(dimethylsiloxane) membranes from polydimethylsiloxane dimethylmethacrylate macromonomer (PDMSDMMA) and divinyl perfluoro- n-hexane (DVF) on the pervaporation characteristics of the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05 wt% benzene was permeated through the cross-linked PDMSDMMA (PDMSDMMA–DVF) membranes, they showed a high benzene permselectivity and permeability of these membranes was enhanced with increasing DVF content significantly. The best normalized permeation rate, separation factor for benzene permselectivity, and pervaporation separation index (PSI) of a PDMSDMMA–DVF membrane were 1.72×10 −5 kg m/m 2 h, 4316, and 7423, respectively. The best normalized permeation rate of a PDMSDMMA–DVF membrane was approximately same as the PDMSDMMA membranes cross-linked with other divinyl compounds, but the separation factor and PSI of the former membrane were greater than those of the latter ones. These pervaporation characteristics are discussed from the viewpoint of chemical and physical structure of the cross-linked PDMSDMMA–DVF membranes in detail.

Electrochemical Amination of Benzene in Aqueous Solutions of Sulfuric Acid and an Organic Solvent

Electrolysis of the Ti(IV)–NH2OH–C6H6 system in 11 M H2SO4 reveals that out of four organic solvents—methanol, formic acid, acetonitrile, and acetic acid—only the last two meet conditions imposed on solvents to be used in indirect cathodic amination of aromatic compounds. They improve the aromatic substrate solubility in the catholyte and affect the process mechanism, determining, together with other factors, the substitution's rate and selectivity.