Benzene In Aqueous Solutions Research Articles

Partial molar volumes of organic solutes in water. X. Benzene and toluene at temperatures from (298 to 573) K and at pressures up to 30 MPa

Density data for dilute aqueous solutions of benzene and toluene are presented together with partial molar volumes at infinite dilution calculated from the experimental data. The measurements were performed at temperatures from (298.15 to 573.15) K and at pressures close to the saturated vapor pressure of water, at 30 MPa and at pressures between these limits. The data were obtained using a high-temperature high-pressure flow vibrating-tube densimeter.

Exhaustive radiolysis of 11 m M aqueous benzene solutions: effect of added oxygen

The gamma radiolysis of aqueous benzene solutions was studied under various conditions (oxygenated, aerated and anoxic) to ascertain the role that oxygen plays in the destruction of benzene. For the oxygenated and aerated systems, phenol and biphenyl were the major quantified products. For the anoxic system, phenol was the sole quantified product. Benzene was initially consumed with approximately the same yield in each of the three systems; G(–benzene) was 0.49 μmol J –1. Initial yields of phenol, G(phenol), were found to be 0.12, 0.060 and 0.030 μmol J –1 for the oxygenated, aerated and anoxic systems, respectively. Biphenyl was initially formed with G=0.028 and 0.019 μmol J –1 in the oxygenated and aerated systems, respectively. The percent conversion of benzene to CO 2 after an absorbed dose of 2500 kGy was 55.1%, 30.5% and 12.5%, respectively, for the oxygenated, aerated and anoxic systems. The last traces of benzene disappeared by a dose of ca. 60 kGy in all three systems. A mechanism was proposed for each system that depended upon the presence or absence of O 2. The total solution toxicity for each system was calculated by summing the individual toxicities of benzene and each quantified product. For the oxygenated and aerated systems, the total solution toxicity was found to go through a maximum at a dose of 22 kGy and then decrease to a value below that of the original solution. The total solution toxicity of the anoxic system was found to decrease from the onset of irradiation.

Removal of Benzene from an Aqueous Solution of Dilute Benzene by Various Cross-Linked Poly(dimethylsiloxane) Membranes during Pervaporation

This paper focuses on the effects of cross-linkers of the cross-linked poly(dimethylsiloxane) membranes derived from poly(dimethylsiloxane) dimethyl methacrylate macromonomer (PDMSDMMA), and divinyl compound, 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 membranes, they showed high benzene permselectivity. Both the permeability and benzene permselectivity of the membranes were enhanced with increasing divinyl compound content as the cross-linker and were significantly influenced by the kind of divinyl compound. PDMSDMMA membranes cross-linked with divinylsiloxane (DVS) showed very high membrane performance during pervaporation. The best normalized permeation rate, separation factor for benzene permselectivity, and pervaporation separation index of a PDMSDMMA−DVS membrane were 1.96 × 10-5 m kg/(m2 h), 2886, and 5657, respectively. These pervaporation characteristics are discussed from the viewpoint of the chemical and physical structure of the cross-linked PDMSDMMA membranes.

Combination of a Mid-infrared Hollow Waveguide Gas Sensor with a Supported Capillary Membrane Sampler for the Detection of Organic Compounds in Water

A Fourier transform infrared (FT-IR) spectroscopy based gas sensor for continuous analysis of liquid phase samples has been developed, coupling a short hollow waveguide (HWG) gas cell with a supported capillary membrane sampler (SCMS) probe. Passing an inert carrier gas through the thin-walled tubular silicon membrane enables the permeation of volatile organic compounds (VOCs) present in aqueous solution and facilitates their continuous and quantitative detection in the infrared hollow fiber by multiple internal reflection spectroscopy. The sensitivity of the sensor system has been determined at the ppb (μg/L) concentration level and the response time ranges from few minutes to 30 min, depending on the analyte and the permeation properties of the sampling membrane. The experimental set-up consists of Bruker Vector 22 FT-IR spectrometer with an externally aligned 50 cm long silica HWG coupled to the SCMS, which is immersed into a glass flask filled with analyte solution and kept under constant stirring. Aqueous solutions of benzene, toluene, xylene isomers and chloroform were qualitatively and quantitatively analyzed confirming the feasibility of this sensor approach for environmental analysis.

Experimental study into the Rayleigh–Taylor turbulent mixing zone heterogeneous structure

Experiments conducted on the SOM facility at the Russian Federal Nuclear Center–VNIITF, concerning the turbulent mixing induced by the Rayleigh–Taylor instability in a three-layer system of immiscible liquids are described. The fluids are contained in a small tank 6.4 cm × 5.4 cm × 12 cm, which is accelerated vertically downward by a gas gun. The mixing layer evolution was imaged by seeding one of the fluids with particles and using a bidirectional light sheet method (refractive index matching was used to minimize measurement errors). Experiments were performed for two different accelerations (g = 350 g0 and g = 100 g0, where g0 = 980 cm/s2, and the acceleration decreases with distance traveled), and with aqueous solutions of glycerin and benzene (with density ratio 1.6). The lower, middle, and upper layers were a sodium hyposulfite–glycerin solution, a water–glycerin solution, and benzene, respectively. The glycerin solution was seeded with particles. The principal objective of the experiments was to obtain the distribution of fluid particle sizes arising from the mixing of the immiscible fluids.

Effects of Morphology of Multicomponent Polymer Membranes Containing Calixarene on Permselective Removal of Benzene from a Dilute Aqueous Solution of Benzene

This paper focuses on the structural characteristics of membranes used in the removal of benzene from a dilute aqueous solution of benzene by pervaporation. Poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) and poly(methyl methacrylate)-block-poly(dimethylsiloxane) (PMMA-b-PDMS) membranes containing tert-butylcalix[4]arene (CA), (CA/PMMA-g-PDMS and CA/PMMA-b-PDMS) were studied. When an aqueous solution of 0.05 wt % benzene was permeated through CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes, these membranes showed strong benzene permselectivity. Both the permeability and the benzene permselectivity of CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes were enhanced by increasing the CA content, due to the affinity of the CA for benzene. The permeability and the benzene permselectivity of CA/PMMA-b-PDMS membranes were much greater than those of CA/PMMA-g-PDMS membranes. Transmission electron microscope (TEM) observations revealed that both the CA/PMMA-g-PDMS and CA/PMMA-b-PDMS membranes had a micr...

Inclusion behavior of water-soluble thiacalix- and calix[4]arenes towards substituted benzenes in aqueous solution.

Inclusion abilities of thiacalix- and calix[4]arenetetrasulfonate (3 and 4) towards mono-substituted benzenes were investigated in neutral aqueous solution. In general, the hosts regioselectively encapsulated the guests from the aromatic moiety except the complexation of toluene by 4, in which the guest penetrated from either the aromatic or the methyl group. Stabilities of the inclusion complexes increased with the electron-withdrawing ability of the substituent on the guest, suggesting pi-pi electronic interaction between the host and guest. In spite of the lower electron density of the aromatic ring, thiacalix[4]arene 3 showed higher inclusion ability than calix[4]arene 4, suggesting that the size rather than the electron density of the calix framework is a more important factor in determining the inclusion ability.

In-tube solid-phase microextraction sampler for long-term storage

Capillary extractors are proposed as samplers-preconcentrators to overcome losses of volatile organic compounds found using “classical” solid-phase microextraction fiber-holder samplers. A set of equal-size extractors was used to extract in-tube an aqueous solution of benzene, toluene, ethylbenzene and xylenes (BTEX) at 146 ppb. After storage for 6–30 days at 0–4 °C (or −15 °C) GC analyses were carried out to study BTEX recovery. Results demonstrated that sample preservation was very good: recovery was higher than 98% after 6 days, and more than 95% after 30 days. Capillary extractors, due to their high performance in preserving sample integrity, represent a real breakthrough for on-site sampling of volatile compounds by solid-phase pre-concentration techniques.

Surface Modification of Microphase-Separated Membranes by Fluorine-Containing Polymer Additive and Removal of Dilute Benzene in Water through These Membranes

Hydrophobically surface-modified membranes were prepared by adding a fluorine-containing graft copolymer into a microphase-separated membrane consisting of poly(dimethylsiloxane) (PDMS) and poly(methyl methacrylate) (PMMA). This study focuses on the effects of surface characteristics and microphase separation of the surface-modified membranes on their permselectivity for a dilute aqueous solution of benzene in pervaporation. Contact angle measurements and X-ray photoelectron spectroscopy revealed that the addition of a fluorine-containing copolymer produced a hydrophobic surface at the membrane air side due to its surface localization. It became apparent from transmission electron microscopy that adding a fluorine-containing copolymer of less than 1.2 wt % did not affect the morphology of the microphase-separated membrane, but adding the copolymer over 1.2 wt % resulted in a morphological change from a continuous PDMS phase to a discontinuous PDMS phase. The addition of a small amount of fluorine-containi...

Effects of the Addition of Calixarene to Microphase-Separated Membranes for the Removal of Volatile Organic Compounds from Dilute Aqueous Solutions

This paper describes the removal of benzene from an aqueous solution of dilute benzene using the poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) membranes containing tert-butyl...

Removal of dilute volatile organic compounds in water through graft copolymer membranes consisting of poly(alkylmethacrylate) and poly(dimethylsiloxane) by pervaporation and their membrane morphology

Removal of volatile organic compounds (VOCs) such as benzene and chloroform in aqueous benzene and chloroform solutions through the poly(methylmethacrylate)-poly(dimethylsiloxane) (PMMA- g-PDMS), poly(ethylmethacrylate)-PDMS (PEMA- g-PDMS), and poly( n-butylmethacrylate)-PDMS (PBMA- g-PDMS) graft copolymer membranes was investigated by pervaporation. When aqueous solutions of dilute VOCs were permeated through the PMMA- g-PDMS and PEMA- g-PDMS membranes, these membranes showed a benzene- and chloroform-permselectivity. Permeation and separation characteristics of the PMMA- g-PDMS and PEMA- g-PDMS membranes changed drastically at a DMS content of about 40 and 70 mol%, respectively. Permeation rate and VOC-permselectivity of the PBMA- g-PDMS membrane, however, increased gradually with increasing DMS content, unlike those of the PMMA- g-PDMS and PEMA- g-PDMS membranes. Furthermore, the transmission electron microscope observations revealed that the PMMA- g-PDMS and PEMA- g-PDMS membranes had microphase separations consisting of a PDMS phase and a poly(alkylmethacrylate) phase, but the PBMA- g-PDMS membrane was homogeneous. The permeability and permselectivity for aqueous VOCs solutions through their graft copolymer membranes in pervaporation are discussed in detail from the viewpoint of their membrane structure, and permselectivity was analyzed by the solution–diffusion theory.

Diffusion Coefficients of Aromatics in Aqueous Solution

Diffusion coefficients of the 12 aromatic compounds phenol, aniline, pyridine, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2-chlorophenol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-cresol, m-cresol, p-cresol, and 3,5-dihydroxytoluol (orcinol) have been measured in aqueous solution at (277.15, 298.15, and 323.15) K using the Taylor dispersion technique. In addition, aqueous solutions of caffeine, benzene, tetraethylammonium perchlorate, and tetramethylammonium perchlorate have been studied where reliable diffusion data are available in the literature in order to test the apparatus. The method provides data with an accuracy to within ±1.5%. In the range of concentrations studied (0.2 × 10-4 to 5.8 × 10-4 mol L-1) the diffusion coefficient depends on the concentration and values at infinite dilution can be obtained by extrapolation. A modified Wilke−Chang equation was found to correlate the data with respect to their dependence on temperature and molecular size of the aromatic compounds.

Calculation of the Potential of Mean Force for the Binding of Glucose to Benzene in Aqueous Solution

Molecular dynamics simulations employing umbrella sampling techniques have been used to calculate the potential of mean force (pmf) for the binding of a β-d-glucopyranose molecule to a benzene molecule in aqueous solution, as a model for the binding of sugar substrates to phenylalanine residues in proteins. The interaction of these two molecules was found to be strongly affected by hydration, as expected, with their nonpolar faces pairing by hydrophobic association to minimize the exposure of apolar groups to water. The pmf for the approach of these molecules is oscillatory in character, with two primary low-energy minima separated by a high free energy barrier, and with the net binding energy being approximately 1.1 kcal/mol and the intervening barrier being almost 2 kcal/mol. A third, weaker minimum was observed between 11 and 12 Å. The oscillatory nature of the pmf results from the successive removal of water layers between the two molecules as they approach one another.

Subcolloidal Fe/Ag Particles for Reductive Dehalogenation of Chlorinated Benzenes

Subcolloidal (<0.1 μm) iron−silver (1% Ag) particles were synthesized for the transformation of chlorinated benzenes in aqueous solution. Hexachlorobenzene (HCB) (4 mg/L) was dechlorinated to tetra...

Electrochemical oxidation of benzene at a glassy carbon electrode

Benzene oxidation in sulfuric acid at a glassy carbon electrode was investigated using voltammetric, chronoamperometric, and spectroscopic methods. The results are compared with those at a Pt electrode. Benzene was observed to be oxidized to benzoquinone presumably by active oxygen that was adsorbed on the GC electrode in the oxygen evolution region. It is concluded that oxidation at glassy carbon can produce benzoquinone or quinone-like compounds from an aqueous benzene solution. The applied potential for benzene oxidation should be less than 2.1 V vs RHE in order to prevent glassy carbon electrode damage by oxidation during long operation.

Role of Counterions in the Solubilization of Benzene by Cetyltrimethylammonium Aggregates. A Multinuclear NMR Investigation

This paper reports about the influence of counterions on the solubilization of benzene in aqueous solutions of cetyltrimethylammonium surfactants (CTAX, X = Br-, Cl-, NO3-, CH3SO3-, and (SO4)2-1/2, CTAB, CTAC, CTAN, CTAMs, and CTAS, respectively) investigated by 1H, 13C, and 14N NMR spectroscopy, at [CTAX] = 0.10 M. Benzene solubility and the size of the aggregates upon benzene addition depend strongly on the nature of counterion. Aqueous CTAC, CTAMs, and CTAS solutions reach benzene saturation up to [benzene]/[CTAX] ∼ 3 without showing any aggregate growth; on the other hand aqueous CTAB and CTAN solutions are able to solubilize a smaller amount of benzene up to [benzene]/[CTAX] ∼ 1 and the solute addition promotes a sphere to rod transition. 1H chemical shifts of the headgroup signals, namely, the trimethylammonium and four methylenes of the aliphatic chain, undergo a more relevant upfield shift upon benzene addition with respect to the hydrophobic chain signals. 1H NMR headgroup signals correlate to [benzene] through cubic equations, while the other signals do not show any simple correlation to [benzene]. A qualitative model in which benzene displaces water from the clefts which characterize the surface of the micellar aggregates is in agreement with all the experimental data.

Diffusion and adsorption of benzene in Regina clay

The diffusion and adsorption coefficients for benzene were measured for a glaciolacustrine clay using the single- and double-reservoir methods, batch tests, and organic carbon content correlations. Single- and double-reservoir diffusion test cells and experimental procedures were specifically developed for volatile organic chemicals. Analytical methods based on solvent extraction with gas chromatography - flame ionization detection and purge and trap gas chromatography - mass spectrometry were used for the analysis of aqueous benzene solutions in the 0.5 µg/L to 500 mg/L range. The measured effective diffusion coefficient was 0.01 m2/a (3.2 × 10-6 cm2/s), and adsorption coefficients ranged from 0.1 to 1.0 mL/g. The diffusion cell tests indicate relatively low levels of retardation for benzene as it moves in clay soils with low organic carbon content.Key words: adsorption, diffusion, benzene, Regina clay.

Transport of Organic Contaminants in Geomembranes under Stress

The transport properties of aqueous solutions of benzene, dichloromethane, and trichloroethylene through extended polyvinyl chloride and high-density polyethylene geomembranes are investigated. It is found that extension enhances the permeation rates of the penetrants through polyvinyl chloride geomembranes, and the opposite effect is found in the case of high-density polyethylene. This difference in response is attributed to the type of structural change, which occurred as a result of the extension. The diffusivities of a mixture of the three organic solvents through the geomembranes are also determined.

Porphyrins as probe molecules in the detection of gaseous pollutants: detection of benzene using cationic porphyrins in polymer films

Porphyrins, which interact with benzene in a sufficiently sensitive and selective manner, so as to be used as benzene probes in thin films, have been studied. Two different water-soluble porphyrins were compared: Tetramethylpyridinium (TMPyP), already described in literature, is known to interact with benzene in aqueous solutions and a new dicationic porphyrin 2,3,7,8,12,13,17,18-octamethyl-5,15-bis-[4-trimethyl ammonium-yl-phenyl)porphyrin dichloride (DTMABP) prepared by a synthesis described here. Initially interactions with benzene were calculated using a molecular modelisation program. The interactions with benzene were measured by visible spectroscopy in solution. We have subsequently developed films of polyvinylpyrrolidone and polymethyl methacrylate containing these two porphyrins and by exposing the films to benzene vapours, pure or diluted, we have been able to detect 45 ppm of benzene in 80 min. The response time was optimised, but the sensitivity was found comparable to other systems described in literature. We report here the results of this study.

Pulse Radiolysis Investigations on Acidic Aqueous Solutions of Benzene: Formation of Radical Cations

The transient optical absorption bands (λmax = 310, 350−500 nm, k = 5.6 × 109 dm3 mol-1 s-1) formed on pulse radiolysis of an acidic (HClO4 = 7.8 mol dm-3) aqueous solution of benzene are assigned to the solute radical cation formed on acid-catalyzed dehydration of the OH adduct. The solute radical cation is able to undergo an electron transfer reaction with Br- with a bimolecular rate constant of 8 × 109 dm3 mol-1 s-1. On the other hand, the OH adduct (λmax = 310 nm) was oxidized by Fe(CN)63- with a bimolecular rate constant of 6.6 × 107 dm3 mol-1 s-1. The radical cation of benzene is a strong one-electron oxidant with oxidation potential in the range 2.1−2.4 V vs NHE.