Hydrocarbons In Aqueous Solutions Research Articles

“In situ” visualization of phase states and transformations of hydrocarbons in water-oil mixtures at high and ultrahigh temperatures and pressures

Numerous geological and geological–geochemical studies have shown that water, in particular, heated and overheated aqueous solutions, plays an active role in the formation and migration of hydrocarbons in the Earth’s interior [3, 5, 6]. At the same time, the behav� ior of hydrocarbons in aqueous solutions, their phase states, and transformations, especially under high and ultrahigh temperature–pressure conditions, have not yet been established conclusively and require special experiments. Research based on visualization of pro� cesses in fluid inclusions in synthetic minerals that were formed simultaneously with realization of aque� ous–hydrocarbon interaction are the most promising in this respect. The study of these inclusions by opti� cal, fluorescent, and luminescent microscopy, local IR spectroscopy, and microthermometry makes it possible not only to determine the composition and aggregate state of the parental medium, but also to observe in situ the behavior and transformations of

Reaction orders of radiation-induced dechlorinations of some aliphatic chlorinated hydrocarbons in aqueous solutions

Previously obtained data regarding radiation-induced dechlorination of some aliphatic chlorinated hydrocarbons tetrachloroethene (PCE), trichloroethene (TCE), chloroform (CHCl 3) and tetrachloromethane (CCl 4) in aqueous solutions were used for determination of formal reaction order of dechlorination. The influence of various factors on this process was investigated. It was found that the formal reaction order changes in the course of reaction and may depend on the initial concentration of chlorinated hydrocarbons.

Effects of fulvic acid concentration and origin on photodegradation of polycyclic aromatic hydrocarbons in aqueous solution: Importance of active oxygen

With an Xe arc lamp house as simulated sunlight, the influences of fulvic acid (FA) concentration and origins on photodegradation of acenaphthene, fluorine, phenanthrene, fluoranthene and pyrene in aqueous solution have been studied. Similar effects of FAs, collected from five places around China, on polycyclic aromatic hydrocarbon (PAH) photodegradation have been observed. Active oxygen was of significance in PAH photodegradation with the presence of FAs. For systems with 1.25 mg L −1 FAs, the contributions of OH to PAH photodegradation rates were from 33% to 69%. FAs had two opposite effects, i.e., stimulating the generation of active oxygen and advancing PAH photodegradation; competing with PAHs for energy and photons and restraining PAH photodegradation. Generally, photodegradation rates of the 5 PAHs decreased with the increase of FAs concentration; except fluoranthene and pyrene were advanced in solutions with low FA concentration. The influences of FA concentration on PAH photodegradation were more significant than FA origin.

Hydrocarbon sensing. Part 1: Some important aspects about sensitivity of a polymer-coated quartz crystal microbalance in the aqueous phase

This report addresses the response of a polymer-based quartz crystal microbalance (QCM) sensor for hydrocarbons in aqueous solutions. The sensor was fabricated by spin coating polystyrene onto a quartz crystal and its analytical properties were investigated under various conditions. It was shown that the sensor responds linearly to toluene and the sensitivity depends on the polymer coating thickness. Studies also revealed that polymer treatment and conditioning play a significant role on sensor sensitivity. The sensor sensitivity was measured as a function of water soaking time and it was found that treating the polystyrene membrane in water for extended periods has a profound influence on the frequency shift arising from hydrocarbon interaction. Atomic force microscopy (AFM) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used to characterize the polystyrene film before and after water exposure. AFM detected changes in the polystyrene surface roughness, whereas ATR-FTIR revealed an increase in the amount of water absorbed in the polymer film with soaking period. It was shown that the protocols employed during sensor fabrication and operation play an important role on sensitivity. The report also highlights some of the problems in performing QCM measurements of hydrocarbons in aqueous electrolytes and suggests ways of minimizing them.

Kinetics and mechanism of the reactions of C6H12, C5H10 and C6D12 cycloalkanes with peroxynitrous acid in aqueous solution and the gas phase

The c-C6H12/c-C6D12 kinetic isotope effect (KIE), the k6/k5 rate constant ratio (c-C6H12/c-C5H10), and the temperature dependence of these ratios in the gas-phase reactions of cycloalkanes with peroxynitrous acid and OH radicals are identical. The same result was obtained for the reactions in aqueous solution. These data are in accord with the conclusion that OH· radicals formed in the homolysis of the HO-ONO bond are the active species in the reactions of HOONO with hydrocarbons in aqueous solution and in the gas phase.

Cloud Point Extraction of Polycyclic Aromatic Hydrocarbons in Aqueous Solution with Silicone Surfactants

Abstract Cloud point extraction (CPE) processes with two silicone surfactants, Dow Corning DC-190 and DC-193, were studied as preconcentration and treatment for the water polluted by three trace polycyclic aromatic hydrocarbons (PAHs): anthracene, phenanthrene and pyrene. For all cases, the volumes of surfactant-rich phase obtained by two silicone surfactants were very small, i.e. a lower water content in the surfactant-rich phase was obtained. For example, less than 3% of the initial solution was obtained in a 1% (by mass) surfactant solution, which was much smaller than that of TX-114 in the same surfactant concentration. And TX-114 is known as a high compact surfactant-rich phase among most nonionic surfactants, thus the comparison showed that an excellent enrichment was ensured in the analysis application by the CPE process with the silicone surfactants, and the lower water content obtained in the surfactant-rich phase is also important in the large scale water treatment. The influences of additives and phase separation methodology on the recovery of PAHs were discussed. Comparing with DC-193. DC-190 has a lower cloud point and a higher recovery (near 100%) of all the three PAHs in same surfactant concentration, which was required for application as a preconcentration process prior to HPLC system. However the DC-190 solution is hard to be phase separated only by heating, whereas DC-193 has a relative higher phase separating speed by heating, but a high cloud point (around 360K) limits its application. Due to the phase separation by heating is the only method of CPE suitable to the large scale water treatment, the mixtures of two silicone surfactants solutions were investigated in this study. A solution containing 1% of mixed DC-190 and DC-193 (in the ratio of 90:10) removed anthracene, phenanthrene and pyrene near 100% with a relative low cloud point and quick phase separating speed.

Pervaporation properties of crosslinked poly(dimethylsiloxane) membranes for the removal of hydrocarbons from water

AbstractThe pervaporation (PV) performance of crosslinked poly(dimethylsiloxane) dimethylmethacrylate (PDMSDMMA) membranes for an aqueous solution of various hydrocarbons was studied using sorption–diffusion theory. Three chlorinated hydrocarbons (chloroform, trichloroethylene, and tetrachloromethane) and three aromatic hydrocarbons (benzene, chlorobenzene, and toluene) were used as the permeants. When aqueous solutions of 0.05 wt % hydrocarbon were permeated through the crosslinked PDMSDMMA membranes, they showed high hydrocarbon/water selectivity and permeability during PV. The hydrocarbon/water selectivity of the crosslinked PDMSDMMA membranes was significantly dependent upon the permeants; in particular, chloroform removed the hydrocarbons most efficiently in this study. The results of the temperature dependence of the PV performance and hydrocarbon absorption into the membrane revealed that the difference in hydrocarbon/water selectivity for various aqueous solutions of hydrocarbons during PV depended significantly on the molar volume and diameter of the hydrocarbons. The permeation and removal mechanism of hydrocarbons from water through crosslinked PDMSDMMA membranes can be explained by a qualitative model based on the diffusion jump model. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2079–2090, 2006

Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation

Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation

Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation

The effect of various operating conditions (initial concentration, liquid phase temperature, applied power, ultrasound frequency) and of the presence of matrix components (1-butanol, NaCl and FeSO 4) on the sonochemical degradation of naphthalene, acenaphthylene and phenanthrene in water has been studied. A horn-type sonicator was used to deliver the ultrasound energy, while immersion sampling solid-phase microextraction (SPME) coupled with GC–MS was employed to follow concentration–time profiles of the chosen PAHs. At the operating conditions in question (initial concentrations of 150, 300 and 450 μg/l, temperatures of 20 and 40 °C, applied power of 45, 75 and 150 W and ultrasound frequencies of 24 and 80 kHz), all PAHs were susceptible to sonochemical treatment and, in most cases, complete degradation could be achieved in up to 120 min of treatment. Conversion was found to decrease with increasing initial concentration and temperature and decreasing power and frequency as well as in the presence of an excess of dissolved salts. Addition of 1-butanol, a known hydroxyl radical scavenger, substantially suppressed degradation throughout the course of the reaction, thus highlighting the role of oxidation reactions in PAHs degradation. In contrast, addition of Fe 2+ ions at a low concentration enhanced degradation through a Fenton-like reaction.

Kinetic analysis of the photodegradation of polycyclic aromatic hydrocarbons in aqueous solution

The mechanisms by which polycyclic aromatic hydrocarbons (PAHs) photodegrade in dilute (≤25 nM) aqueous solutions under varying O2 concentrations were examined. Employing previously measured photodegradation quantum yields (acquired in the absence and presence of electron donors to the PAH cation radicals, P+), excited singlet state (1P*) lifetimes, 1P*/O2 quenching rate constants and other parameters from the literature, a kinetic model was developed to analyze the fraction of PAH photodegradation that proceeds via the 1P* or excited triplet state (3P*), as well as to determine the relative contribution of electron transfer to O2 versus the direct reaction with O2 from each state. The analysis supports the following conclusions: 1) 1P* is more reactive with O2 than 3P*; 2) reaction via 1P* proceeds predominantly through electron transfer to produce the P+ intermediate, whereas reaction via 3P* proceeds primarily through direct reaction with O2 within the collision complex, consistent with the thermodynamic driving forces for electron transfer from these states; 3) although 3P* is involved significantly in the degradation of many PAHs, such as anthracene, 9-methylanthracene, acenaphthene, and perylene, it is not involved in the degradation of others such as pyrene and benzo[a]pyrene. Under aerobic conditions, photodegradation is likely to be controlled largely by 1P* lifetime and reactivity.

Laser based spectroscopic and kinetic investigations of reactions of the Cl atom with oxygenated hydrocarbons in aqueous solution

A time-resolved laser photolysis broadband diode array experiment has been used to measure the absorption spectrum of the chlorine atom in aqueous solution formed after excimer laser photolysis of chloroacetone and hypochlorous acid at λ = 248 nm. Laser photolysis-long path laser absorption at λ = 325 nm (He/Cd) was then applied to determine the rate coefficients for the reactions of the chlorine atom at T = 298 K with methanol, k1 = (1.0 ± 0.1)·109 M−1 s−1; ethanol, k2 = (2.2 ± 0.3)·109 M−1 s−1; 1-propanol, k3 = (2.2 ± 0.4)·109 M−1 s−1; 2-propanol, k4 = (3.2 ± 0.7)·109 M−1 s−1; tert-butanol, k5 = (1.5 ± 0.1)·109 M−1 s−1; diethyl ether, k6 = (1.3 ± 0.1)·109 M−1 s−1; methyl-tert-butyl ether, k7 = (1.3 ± 0.1)·109 M−1 s−1; tetrahydrofuran, k8 = (2.6 ± 0.4)·109 M−1 s−1; acetone, k9 = (7.8 ± 0.7)·107 M−1 s−1; formic acid, k10 = (2.8 ± 0.3)·109 M−1 s−1; acetic acid, k11 = (1.0 ± 0.2)·108 M−1 s−1; 2-butanol, k12 = (5.0 ± 0.6)·109 M−1 s−1; 2-butanone, k13 = (2.4 ± 0.3)·108 M−1 s−1; hydrated formaldehyde, k14 = (1.4 ± 0.3)·109 M−1 s−1; propionic acid, k15 = (1.2 ± 0.3)·109 M−1 s−1; isobutyric acid, k16 = (1.7 ± 0.3)·109 M−1 s−1; trichloromethane, k17 = (2.3 ± 0.5)·108 M−1 s−1 and dichloromethane, k18 = (9.3 ± 0.3)·106 M−1 s−1. A correlation between the rate constants at T = 298 K for all oxygenated hydrocarbons and the bond dissociation energy of the weakest C–H bond oflog kH/l mol−1 s−1 = (29 ± 9) − (5 ± 2)·10−2 BDE/kJ mol−1(n = 18, r = 0.88) is derived. From temperature dependent measurements (temperature range from 288 to 328 K) the following Arrhenius expressions were derived:k1 (Cl + CH3OH) = (7.9 ± 0.3)·1014 exp[−(4.1 ± 0.7)·103 K/T] l mol−1 s−1Ea = 34 ± 6 kJ mol−1k2 (Cl + CH3CH2OH) = (4.6 ± 0.4)·1012 exp[−(2.7 ± 0.9)·103 K/T] l mol−1 s−1Ea = 19 ± 7 kJ mol−1k3 (Cl + CH3CH2CH2OH) = (5.0 ± 0.4)·1012 exp[−(2.3 ± 0.8)·103 K/T] l mol−1 s−1Ea = 19 ± 7 kJ mol−1k4 (Cl + CH3CH(OH) CH3) = (2.8 ± 0.3)·1013 exp[−(3.3 ± 1.2)·103 K/T] l mol−1 s−1Ea = 23 ± 8 kJ mol−1k10 (Cl + HCOOH) = (8.9 ± 1.4)·1012 exp[−(2.8 ± 1.1)·103 K/T] l mol−1 s−1Ea = 20 ± 6 kJ mol−1k11 (Cl + CH3COOH) = (1.3 ± 0.1)·1015 exp[−(4.9 ± 1.4)·103 K/T] l mol−1 s−1Ea = 41 ± 11 kJ mol−1k14 (Cl + HCHO) = (4.7 ± 0.3)·1013 exp[−(3.9 ± 0.9)·103 K/T] l mol−1 s−1Ea = 26 ± 6 kJ mol−1k15 (Cl + CH3CH2COOH) = (6.4 ± 0.6)·1016 exp[−(9.8 ± 2.2)·103 K/T] l mol−1 s−1Ea = 44 ± 10 kJ mol−1k16 (Cl + CH3CH(CH3) COOH) = (5.7 ± 0.3)·1013 exp[−(3.8 ± 0.6)·103 K/T] l mol−1 s−1Ea = 26 ± 4 kJ mol−1A regression for the measured activation energies as a function of the bond dissociation energies (BDE) of the weakest C–H bond yields Ea = (0.8 ± 0.3) BDE/kJ mol−1 − (300 ± 100). The effects of ionic strength (Ieff) on the reactions of chlorine atom with methanol and hydrated formaldehyde were also investigated. A decrease of the rate constant with increasing Ieff was found. All the errors stated throughout this work are statistical errors for a confidence interval of 95%.

New 224 nm Hollow Cathode Laser-UV Raman Spectrometer

We have developed an optimized high-throughput UV Raman spectrometer that utilizes a simple, inexpensive new 224.3 nm hollow cathode laser. This quasi-continuous wave (CW) 224.3 nm laser can be used to detect sub-ppm concentrations of aromatic and polycyclic aromatic hydrocarbons in aqueous solutions. This excitation is also useful for studying aromatic amino acids in proteins. We demonstrate the utility of this spectrometer to study the environments of tyr and trp in horse heart myoglobin.

超音波による有機塩素化合物の分解

四塩化炭素, クロロベンゼン類, クロロフェノール類, クロロアセトアルデヒド類などの有機塩素化合物水溶液の超音波照射による分解を検討した。いずれの化合物も短時間の照射で, 80%以上の分解が起った。主な分解生成物は一酸化炭素, 二酸化炭素および塩化物イオンであった。アルゴン雰囲気下で分解が促進され, 分解の速さは化合物の揮発性および水中の溶解度などの物性によって異なり, 疎水性と蒸気圧の大きい化合物は分解し易く, 親水性の化合物は分解し難くかった。分解反応はこれら揮発性および水中の溶解度にとって, それぞれキャビテーションバブル内あるいは界面領域での燃焼反応と熱分解およびOHラジカルによる反応といくつかの経路よって分解すると考えられた。

A laser flash photolysis kinetic study of reactions of the Cl2? radical anion with oxygenated hydrocarbons in aqueous solution

A laser photolysis–long path laser absorption (LP-LPLA) experiment has been used to determine the rate constants for H-atom abstraction reactions of the dichloride radical anion (Cl2−) in aqueous solution. From direct measurements of the decay of Cl2− in the presence of different reactants at pH = 4 and I = 0.1 M the following rate constants at T = 298 K were derived: methanol, (5.1 ± 0.3)·104 M−1 s−1; ethanol, (1.2 ± 0.2)·105 M−1 s−1; 1-propanol, (1.01 ± 0.07)·105 M−1 s−1; 2-propanol, (1.9 ± 0.3)·105 M−1 s−1; tert.-butanol, (2.6 ± 0.5)·104 M−1 s−1; formaldehyde, (3.6 ± 0.5)·104 M−1 s−1; diethylether, (4.0 ± 0.2)·105 M−1 s−1; methyl-tert.-butylether, (7 ± 1)·104 M−1 s−1; tetrahydrofuran, (4.8 ± 0.6)·105 M−1 s−1; acetone, (1.41 ± 0.09)·103 M−1 s−1. For the reactions of Cl2− with formic acid and acetic acid rate constants of (8.0 ± 1.4)·104 M−1 s−1 (pH = 0, I = 1.1 M and T = 298 K) and (1.5 ± 0.8) · 103 M−1 s−1 (pH = 0.42, I = 0.48 M and T = 298 K), respectively, were derived. A correlation between the rate constants at T = 298 K for all oxygenated hydrocarbons and the bond dissociation energy (BDE) of the weakest C-H-bond of log k2nd = (32.9 ± 8.9) − (0.073 ± 0.022)·BDE/kJ mol−1 is derived. From temperature-dependent measurements the following Arrhenius expressions were derived: k (Cl2− + HCOOH) = (2.00 ± 0.05)·1010·exp(−(4500 ± 200) K/T) M−1 s−1, Ea = (37 ± 2) kJ mol−1 k (Cl2− + CH3COOH) = (2.7 ± 0.5)·1010·exp(−(4900 ± 1300) K/T) M−1 s−1, Ea = (41 ± 11) kJ mol−1 k (Cl2− + CH3OH) = (5.1 ± 0.9)·1012·exp(−(5500 ± 1500) K/T) M−1 s−1, Ea = (46 ± 13) kJ mol−1 k (Cl2− + CH2(OH)2) = (7.9 ± 0.7)·1010·exp(−(4400 ± 700) K/T) M−1 s−1, Ea = (36 ± 5) kJ mol−1 Finally, in measurements at different ionic strengths (I) a decrease of the rate constant with increasing I has been observed in the reactions of Cl2− with methanol and hydrated formaldehyde. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 169–181, 1999

Optimisation of an integrated optical evanescent wave absorbance sensor for the determination of chlorinated hydrocarbons in water.

The suitability of an integrated optical chemical sensor for the determination of highly volatile chlorinated hydrocarbons in aqueous solutions has been proven. The analytes are detected by NIR absorption spectrometry in the evanescent field of an integrated optical strip waveguide generated in a BGG31 (Schott, Germany) glass substrate, which is coated with a hydrophobic polymer superstrate as sensing layer. It has been shown that the sensitivity increases when the refractive index of the superstrate is increased from 1.333 up to 1.46. Different UV-cured polysiloxanes with low cross sensitivity to water have been prepared. Due to the good light transmission properties of the IO-sensors prepared by this method, quantitative measurements have been performed with the model system trichloroethene (TCE) in water. A detection limit of 22 ppm has been found and the sensor response times (t(90)-value) are between five and fourteen minutes for a coating thickness of around 30 microm. The sensor response is totally reversible. The analyte desorbes in air within 2 min. The enrichment of trichloroethene in the polysiloxane coating can be described by film diffusion through the aqueous boundary layer as rate determining step.

Improved analysis of polycyclic aromatic hydrocarbons in aqueous solutions by gas chromatography

The analysis of organics in aqueous solutions by gas chromatography needs sample pretreatment in order to avoid contact of water with the stationary phase of the column. A new method based on dehydration by boron trifluoride and its use for the analysis of polycyclic aromatic hydrocarbons in microemulsions is described.

Inclusion complexation of volatile chlorinated hydrocarbons in aqueous solutions of branched cyclodextrins

The inclusion complexation of five volatile chlorinated hydrocarbons, i.e., chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, and monochlorobenzene, with branched cyclodextrins (CDs) such as monoglucosyl-α-CD and monomaltosyl-β-CD in aqueous solutions was examined. Their inclusion complexes were found to be very water soluble and the solubilities of the chlorinated hydrocarbons in aqueous solutions increased almost linearly or gradually with increasing concentration of the branched CDs. The amounts of the chlorinated hydrocarbons included in the branched CDs were well related to their molecular size and shape. In addition, the viability of application to pollution prevention is discussed.

ChemInform Abstract: Decomposition of Chlorinated Hydrocarbons in Aqueous Solutions by Ultrasonic Irradiation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Decomposition of Chlorinated Hydrocarbons in Aqueous Solutions by Ultrasonic Irradiation

Abstract Trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, chloroform and carbon tetrachloride in dilute aqueous solutions were rapidly decomposed to chloride anions, hydrogen, carbon monoxide and carbon dioxide by ultrasonic irradiation.

Reductive dechlorination of chlorinated hydrocarbons in aqueous solutions containing ferrous and sulfide ions

The transformation of volatile chlorinated hydrocarbons in aqueous phase containing free ferrous and sulfide ions with and without light irradiation were investigated to evaluate the effect of these reducing ions on the dechlorination of chlorinated hydrocarbons. In the presence of the ferrous ion alone, 84% of the original carbon tetrachloride (CT) was transformed to chloroform within 33 days, and a removal efficiency of 99% was reached when the solution was irradiated by visible light. However, carbon tetrachloride did not appear to be reactive in other media containing sulfide and/or bound ferrous ions. 1,1,1-trichloroethane and tetrachloroethylene were less susceptible than carbon tetrachloride to the reductive dechlorination. No transformation was observed for these two compounds in different types of media in 33 days. Oxidationreduction potential (ORP) measurements showed that carbon tetrachloride could be depleted only when ORP of the environment was below 360 mV (relative to standard hydrogen electrode). This study indicates that free ferrous ion is an active reducing agent for the dechlorination of CT, but has little effect on the transformation of 1,1,1-trichloroethane and tetrachloroethylene, whereas, free sulfide and bound ferrous ions do not appear to have the capability of dechlorination for these heavily chlorinated hydrocarbons.