Methyl Tert-butyl Ether In Water Research Articles

Microextraction flotamicroextraction flotation concentration and determination of chloroacetic acids in watertion concentration and determination of chloroacetic acids in water

The flotation-assisted liquid-liquid microextraction method of mono-, di -, and trichloroacetic acids (CAAs) has been developed. Methyl tert-butyl ether (MTBE) was used as an extractant. The emulsification was performed by the ultrasonic irradiation. The microextraction procedure was carried out in a 27 ml special tube. It was equipped with the capillaries for sampling the extract and an air outlet. A salting-out additive (Na2SO4) was used to reduce the solubility of MTBE in water and to increase the extraction efficiency of CAAs. The air passage through the emulsion of the extractant was carried out using the eight-channel capillary bubbler. The organic matrix replacement was applied for ion chromatographic determination of CAAs with the conductivity detection. Current study showed the advantages of the flotation-assisted demulsification over the centrifugal one. The concentration factors of chlorinated acetic acids were 2-3 times higher. The detection limits of CAAs in water were reduced to (5·10-4 - 4·10-3 mg/l). The extraction time was reduced by more than three times. The trueness of the determination of HUC impurities was confirmed by the addition method. The statistical insignificance of the systematic error in comparison with the random error was shown. The developed method of preconcentration in combination with ion chromatography made it possible to determine the concentrations of CAAs 40-1250 times lower than the normalized SanPiN and WHO. This allowed conducting a highly sensitive determination of CAAs in water long before the onset of the critical ecological state.

High Selective Composite Polyalkylmethylsiloxane Membranes for Pervaporative Removal of MTBE from Water: Effect of Polymer Side-chain.

For the first time, the effect of the side-chain in polyalkylmethylsiloxane towards pervaporative removal of methyl tert-butyl ether (MTBE) from water was studied. The noticeable enhancement of separation factor during the pervaporation of 1 wt.% MTBE solution in water through the dense film (40–50 µm) can be achieved by substitution of a methyl group (separation factor 111) for heptyl (161), octyl (169) or decyl (180) one in polyalkylmethylsiloxane. Composite membrane with the selective layer (~8 µm) made of polydecylmethylsiloxane (M10) on top of microfiltration support (MFFK membrane) demonstrated MTBE/water separation factor of 310, which was 72% greater than for the dense film (180). A high separation factor together with an overall flux of 0.82 kg·m−2·h−1 allowed this M10/MFFK composite membrane to outperform the commercial composite membranes. The analysis of the concentration polarization modulus and the boundary layer thickness revealed that the feed flow velocity should be gradually increased from 5 cm·s−1 for an initial solution (1 wt.% of MTBE in water) to 13 cm·s−1 for a depleted solution (0.2 wt.% of MTBE in water) to overcome the concentration polarization phenomena in case of composite membrane M10/MFFK (Texp = 50 °C).

An effective force field to reproduce the solubility of MTBE in water

In this work, a force field has been developed for methyl tert-butyl ether (MTBE) in the pure liquid by adjusting the intermolecular parameters to reproduce three target thermodynamic properties: the dielectric constant, the surface tension and the density of the liquid. In addition to these three properties, the new force field was able to reproduce the experimental values for the heat of vaporization, the vapor pressure, the self-diffusion and the viscosity, with relative errors smaller than 5%. Moreover, the target properties were also calculated as a function of temperature, in the 288.15 to 313.15 K range. A remarkable agreement with experimental data was found. Finally, by combining the NEWFFP force field for MTBE with the TIP4P/ε force field for water, the solubility of MTBE in water as a function of temperature was obtained. The results follow the experimental line with a deviation which is less than 7%. The decrease in the solubility with temperature is explained by the formation, at low temperature, of stable, short-lived MTBE-water clusters that are clearly identified. These clusters contain one, two and three MTBE molecules that form hydrogen bonds with water molecules. At temperatures above 298.15 K no clusters are found, in agreement with the experimentally observed negative slope of the solubility versus temperature behavior.

Rapid biodegradation of methyl tert-butyl ether (MTBE) by pure bacterial cultures

Two pure bacterial strains capable of rapid degrading methyl tert-butyl ether (MTBE) were isolated from an industrial wastewater treatment plant, identified and characterized. These strains are able to grow on MTBE as the sole carbon and energy sources and completely mineralize it to the biomass and carbon dioxide. The strains were identified as Bacillus cereus and Klebsiella terrigena. Both strains are able to grow in the presence of 48 gl -1 MTBE in water, which is almost the maximum concentration of MTBE in the water. They were able to completely degrade 10 gl -1 MTBE in less than a day. The specific degradation rate of MTBE at optimum conditions were 5.89 and 5.78 g(MTBE) g(cells) -1 h -1 for B. cereus and K. terrigena, respectively. The biomass yield was 0.085 and 0.076 gg -1 , respectively. The cultivations were carried out successfully at 25, 30 and 37 °C, while they showed the best performance at 37 °C. Neither of the strains was able to grow and degrade MTBE anaerobically.

Preparation and characterization of Pd doped ceria–ZnO nanocomposite catalyst for methyl tert-butyl ether (MTBE) photodegradation

A series of binary oxide catalysts (ceria–ZnO) were prepared and doped with different amounts of palladium in the range of 0.5%–1.5%. The prepared catalysts were characterized by SEM, TEM, XRD and XPS, as well as by N2 sorptiometry study. The XPS results confirmed the structure of the Pd CeO2−x-ZnO. The photocatalytic activity of these catalysts was evaluated for degradation of MTBE in water. These photocatalyst efficiently degrade a 100ppm aqueous solution of MTBE upon UV irradiation for 5h in the presence of 100mg of each of these photocatalysts. The removal of 99.6% of the MTBE was achieved with the ceria–ZnO catalyst doped with 1% Pd. In addition to the Pd loading, the N2 sorptiometry study introduced other factors that might affect the catalytic efficiency is the catalyst average pore sizes. The photoreaction was determined to be a first order reaction.

Molecular interaction, co-solubilization of organic pollutants and ecotoxicity of a potential carcinogenic fuel additive MTBE in water

We study the molecular properties and ecological consequences of a most common gasoline oxygenate, and widespread carcinogenic environmental threat, methyl tert-butyl ether (MTBE) upon inclusion in water. Our study shows the change of bulk properties like densities, viscosities and refractive indices of binary mixtures of water and MTBE at temperatures from 10°C to 50°C and over the entire composition range, under atmospheric pressure using densimetry, viscometry and refractive index measurement. The studies are clear indicative of the association of MTBE in the hydrogen bonding network and possible MTBE clustering in the aqueous solution. While, dynamic light scattering studies confirm the formation of micro-droplets (micelle-like) of MTBE in water, which still persist at 70°C (much above the boiling point of pure MTBE, 55.2°C), FTIR and Raman spectroscopies have distinctly unrevealed the molecular interaction of MTBE with water molecules. Co-solubilization of other potential hazardous organic matters (anthracene, naphthalene, benzo[α]pyrene and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM)) in the MTBE–water mixture has also been studied. Raman spectroscopic studies confirm the micelle-like cluster of MTBE to be a potential host of the organic pollutants in the aqueous environments. The picosecond-resolved spectroscopic studies also confirm localization of DCM in the ground state, in the MTBE cluster. Our studies also show the ecotoxic effect of MTBE in model eukaryotic microorganism yeast in aqueous environments.

Thermodynamic investigations of methyl tert-butyl ether and water mixtures

Interactions between methyl tert-butyl ether (MTBE) and water have been investigated by scanning calorimetry, isothermal titration calorimetry, densitometry, IR-spectroscopy, and gas chromatography. The solubilization of MTBE in water at 25 °C at infinite dilution has ΔH° = -17.0 ± 0.6 kJ mol(-1); ΔS° = -80 ± 2 J mol(-1) K(-1); ΔC(p) = +332 ± 15 J mol(-1) K(-1); ΔV° = -18 ± 2 cm(3) mol(-1). The signs of these thermodynamic functions are consistent with hydrophobic interactions. The occurrence of hydrophobic interaction is further substantiated as IR absorption spectra of MTBE-water mixtures show that MTBE strengthens the hydrogen bond network of water. Solubilization of MTBE in water is exothermic whereas solubilization of water in MTBE is endothermic with ΔH° = +5.3 ± 0.6 kJ mol(-1). The negative mixing volume is explained by a large negative contribution due to size differences between water and MTBE and by a positive contribution due to changes in the water structure around MTBE. Henry's law constants, K(H), were determined from vapor pressure measurements of mixtures equilibrated at different temperatures. A van't Hoff analysis of K(H) gave ΔH(H)° = 50 ± 1 kJ mol(-1) and ΔS(H)° = 166 ± 5 J mol(-1) K(-1) for the solution to gas transfer. MTBE is excluded from the ice phase water upon freezing MTBE-water mixtures.

Hydraulic performance of a proposed in situ photocatalytic reactor for degradation of MTBE in water

Methyl tert-butyl ether (MTBE) groundwater remediation projects often require a combination of technologies resulting in increasing the project costs. A cost-effective in situ photocatalytic reactor design, Honeycomb II, is proposed and tested for its efficiency in MTBE degradation at various flows. This study is an intermediate phase of the research in developing an in situ photocatalytic reactor for groundwater remediation. It examines the effect of the operating variables: air and water flow and double passages through Honeycomb II, on the MTBE removal. MTBE vaporisation is affected by not only temperature, Henry’s law constant and air flow to volume ratio but also reactor geometry. The column reactor achieved more than 84% MTBE removal after 8 h at flows equivalent to horizontal groundwater velocities slower than 21.2 cm d −1. Despite the contrasting properties between a photocatalytic indicator methylene blue and MTBE, the reactor efficiency in degrading both compounds showed similar responses towards flow (equivalent groundwater velocity and hydraulic residence time (HRT)). The critical HRT for both compounds was approximately 1 d, which corresponded to a velocity of 21.2 cm d −1. A double pass through both new and used catalysts achieved more than 95% MTBE removal after two passes in 48 h. It also verified that the removal efficiency can be estimated via the sequential order of the removal efficiency of one pass obtained in the laboratory. This study reinforces the potential of this reactor design for in situ groundwater remediation.

Optimization of dispersive liquid–liquid microextraction and improvement of detection limit of methyl tert-butyl ether in water with the aid of chemometrics

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry-selective ion monitoring (GC–MS-SIM) was applied to the determination of methyl tert-butyl ether (MTBE) in water samples. The effect of main parameters affecting the extraction efficiency was studied simultaneously. From selected parameters, volume of extraction solvent, volume of dispersive solvent, and salt concentration were optimized by means of experimental design. The statistical parameters of the derived model were R 2 = 0.9987 and F = 17.83. The optimal conditions were 42.0 μL for extraction solvent, 0.30 mL for disperser solvent and 5% (w/v) for sodium chloride. The calibration linear range was 0.001–370 μg L −1. The improved detection limit with the aid of chemometrics was 0.3 ng L −1. The relative standard deviation (RSD) with n = 9 for 0.1 mg L −1 MTBE in water with and without internal standard was 2.7% and 3.1%, respectively. Under the optimal conditions, the relative recoveries of spiked MTBE in different water samples were in the range of 100–105%.

Headspace-solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry for analysis methyl tert-butyl ether in water and gasoline

A simple and sensitive method for the determination of methyl tert-butyl ether (MTBE) in water using headspace-solid-phase microextraction (HS-SPME) at sub-ng mL −1 concentrations is described. The analysis was carried out using a cooled SPME fiber coated with a film of dodecylsulfate-doped polypyrrole coupled to ion mobility spectrometry equipped with corona discharge ionization. The headspace-solid-phase microextraction experimental procedures to extract MTBE in water samples were optimized with a dodecylsulfate-doped polypyrrole coated fiber at a 30 min extraction time, extraction temperature of 40 °C, sodium chloride concentration of 2.5 mol L −1 and desorption temperature of 140 °C. Two linear calibration curves respectively in the ranges of 2–17 ng mL −1 and 10–70 ng mL −1 with detection limits of 0.7 ng mL −1 and 4.9 ng mL −1 were obtained. Relative standard deviations for three replicates in water samples were <10%. The capability of dodecylsulfate-doped polypyrrole to extract MTBE has been compared with the results obtained based on the literature data for commercial fiber. The results shows that dodecylsulfate-doped polypyrrole, as a solid-phase microextraction fiber coating, is suitable for successful extraction of MTBE having detection limits comparable to what obtained with commercial fibers. Finally, the proposed method was applied to the analysis of MTBE in three ground water samples and regular unleaded gasoline from petrol station in Tehran central district, Iran.

What is the correct form of BET isotherm for modeling liquid phase adsorption?

In this work subtleties of application of BET isotherm for liquid phase adsorption is presented. It has been shown that direct use of the classical BET equation (which was developed for gas phase adsorption) to liquid phase adsorption leads to ambiguous and erroneous results. Some cases of misuse of BET equation for liquid phase adsorption have been revisited. By close examination of the development of the classical equation, the causes of misunderstandings were elucidated and the suitable form of the BET equation for liquid phase adsorption was developed. As case studies, the classical form of the BET equation along with the correct form of the equation for liquid phase have been applied for modeling liquid phase adsorption of methyl tert-butyl ether (MTBE) on perfluorooctyl alumina, phenol on activated carbon and pentachlorophenol on carbonized bark. It has been shown that direct application of the classical BET isotherm to liquid phase adsorption results in poor and erroneous estimation of the equation parameters. For example, in aqueous phase adsorption of MTBE on perfluorooctyl alumina, the monolayer adsorption capacity of the adsorbent was calculated as 9.7 mg/g instead of 3.3 mg/g or the saturation concentration of MTBE in water was calculated as 1212 mg/L instead of 42000 mg/L.

Fe-zeolites as catalysts for chemical oxidation of MTBE in water with H2O2

The heterogeneous catalytic wet oxidation of methyl tert-butyl ether (MTBE) with hydrogen peroxide, catalyzed by the iron-containing zeolites Fe-ZSM5 and Fe-Beta, was studied at ambient conditions and pH 7. The kinetics of MTBE degradation could be well-fitted to a pseudo-first-order model. Using Fe-ZSM5, the dependence of the reaction rate constant on hydrogen peroxide and catalyst concentration was determined. Furthermore, the formation and oxidation of tert-butyl alcohol and tert-butyl formate as intermediates of MTBE oxidation were studied. A comparison of the reaction rates of MTBE, trichloroethylene and diethyl ether in the Fe-ZSM5/H2O2 system revealed that adsorption plays a positive role for the degradation reaction.Comparing the two types of Fe-containing zeolites applied in this study, Fe-Beta showed a lower catalytic activity for H2O2 decomposition and also MTBE degradation. However, in terms of utilization of H2O2 for MTBE degradation Fe-Beta is advantageous over Fe-ZSM5. This could be explained by the stronger adsorptive enrichment of MTBE on the Fe-Beta zeolite. This study shows that Fe-containing zeolites are promising catalysts for oxidative degradation of MTBE by H2O2.

FTIR and Ab Initio Investigations of the MTBE−Water Complex

The infrared spectrum of methyl tert-butyl ether (MTBE) in liquid water has been studied using both FTIR absorption and FTIR-ATR spectroscopy in conjunction with ab initio calculations. Compared to the liquid MTBE IR spectrum, the C-O and C-C stretching vibrational frequencies of MTBE in water are found to shift to the red and blue by up to 26 and 9 cm (-1), respectively. Ab initio calculations suggest that these shifts are caused by complexation of the MTBE molecule with water molecules through hydrogen bonding. Our observation of the vibrational frequency shifts in the IR spectrum of MTBE in water provides the IR spectroscopic evidence of organics-water complexes in the diluted aqueous solution. The implication of the effect of the hydrogen bond in organics-water complexation on solvation and reactivity of the organic compound in aqueous chemical processes is discussed.

Radiation induced decomposition of methyl tert-butyl ether in water in presence of chloroform: Kinetic modelling

The destruction of methyl tert-butylether (MTBE) in water in the presence of chloroform has been studied using 60Co gamma irradiation. Distilled water solutions at three different concentrations of the individual solutes MTBE and CHCl 3 were irradiated for various times to provide dose destruction information. Then, the irradiation of a mixture of MTBE (at two different concentrations) and CHCl 3 (at one concentration) was conducted. A kinetic model was used incorporating recently determined bimolecular rate constants to describe the destruction of the MTBE and CHCl 3 individually and in mixtures. These studies were conducted in distilled water simplifying the radiation chemistry significantly. With the improvements in the modelling capability, we are closer to being able to use the model to study “real-world” mixtures in natural waters.

Determination of Trace of Methyl tert-Butyl Ether in Water Using Liquid Drop Headspace Sampling and GC

The possibility of applying headspace microextraction into a single drop of solvent for the determination of methyl tert -butyl ether in aqueous solutions has been demonstrated. A drop of benzyl alcohol is used for extraction. The analyte is extracted by suspending a 1.8 μL extracting drop directly from the tip of a microsyringe fixed above an extraction vial with a septum such that the needle passes through the septum and the needle tip is positioned above the surface of the solution. After the extraction is finished, the drop is retracted back into the needle and injected directly into a GC column. Optimization of experimental variables (time, temperature, stirring rate and ionic strength of the solution) with respect to the extraction efficiency was investigated. The calibration range for methyl tert-butyl ether was 0.01–10 ppm and the detection limit 7 ppb. The relative standard deviation for 0.1 ppm methyl tert -butyl ether in water was 5.5%.

Degradation of methyl tert-butyl ether in water: effects of the combined use of sonolysis and photocatalysis

The degradation of methyl tert-butyl ether (MTBE) in water was kinetically investigated in a O 2/Ar 80:20 atmosphere employing either sonolysis at 20 kHz, or photocatalysis on TiO 2 (with 315 nm < λ irr < 400 nm), or simultaneous sonolysis and photocatalysis (i.e. sonophotocatalysis), as degradation techniques. In all investigated conditions, MTBE concentration decreased according to a first order rate law; under ultrasound the degradation rate was stirring-dependent. The time profile of the reaction intermediates gave information on the reaction paths prevailing under the different experimental conditions. The energy consumption of the employed degradation techniques was also evaluated, which might be decisive for their practical application.

Application of GC-MS and GC-AED to the evaluation of by-products formed by solar photo-fenton degradation of Methyl tert-butyl ether in water

This study describes the application of solar photocatalysis by photo-Fenton reaction to the degradation of methyl tert-butyl ether (MTBE) in aqueous solutions at a pilot scale in a compound parabolic collector (CPC) reactor. The results show a rapid and complete oxidation of MTBE after only 35 min of treatment. However, 54% remains to be mineralized after that time, almost compleste mineralization (97%) being reached only after 155 min of treatment. This indicated the formation of a large quantity of transformation products (TPs) more resistant to degradation than the parent compound. Identification and quantification of six TPs (tert-butyl formate, tert-butyl alcohol, acetone, methyl acetate, isobutene and formaldehyde) were possible with the combined use of two complementary techniques: GC-MS and GC-AED, both coupled to a purge-and-trap system. Ionic chromatography (IC) was used for the identification of organic ions usually present in the last stages of the mineralization process. Only formate ions were detected and these may be considered as the last step in the oxidation process previous to total mineralization. A degradation pathway, fixing the most critical compounds in terms of kinetic degradation, was proposed.

Reevaluation of headspace solid-phase microextraction and gas chromatography–mass spectrometry for the determination of methyl tert-butyl ether in water samples

A headspace solid-phase microextraction (SPME) and gas chromatography–mass spectrometry (GC–MS) method has been reevaluated for the determination of methyl tert-butyl ether (MTBE) in water. Factors affecting method performance were examined. The internal standard, deuterated MTBE, is necessary because it allows normalization of the calibration since the deuterated MTBE and MTBE experience the same extraction efficiency. The method detection limit was 6.6 ng/l, with a linear range up to 160 μg/l. SPME extraction efficiency and detection sensitivity for MTBE decreased in the presence of gasoline matrix. However, reliable measurement of MTBE was possible in the background matrix concentration of 0.97 mg/l gasoline using deuterated internal standard. Reproducibility was 4.5% at the spiking level of 47 ng/l. The average recoveries of MTBE in spiked fountain water, tap water, and snow at 60 ng/l and in spiked rainwater at 580 ng/l ranged from 101 to 105%. The method was successfully applied to the analysis of trace levels of MTBE in various water samples, including rain and snow samples collected in Albany, NY, USA.

Interlaboratory comparison study for the determination of methyl tert-butyl ether in water.

This is the first publication which describes the evaluation of the analytical performance and state-of-the-art of the determination of methyl tert-butyl ether (MTBE) in water at ng L(-1) concentrations. An interlaboratory comparison study for the determination of MTBE in water was carried out. Twenty-eight laboratories from seven European countries participated in the study. Twenty of those finally transmitted results to the organiser. Italian spring water, containing no detectable amounts of MTBE was fortified to yield two samples with MTBE concentrations of 0.074 +/- 0.004 microg L(-1) and 0.256 +/- 0.010 microg L(-1). The laboratories applied their regular in-house methods to analyse the water samples. Static headspace, Purge & Trap, solid-phase microextraction (SPME) or direct aqueous injection were used as sample preparation techniques. Subsequent separation and detection of MTBE were performed by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/flame ionisation detection (GC/FID). After rejection of outliers, the overall arithmetic mean of laboratory results corresponded to recoveries of 78 +/- 20% (Sample A) and 88 +/- 20% (Sample B) of the reference concentrations. The between laboratory coefficients of variation (CV) were 32% and 31%, respectively. The organisation of the study and quality assurance measures at the organiser's laboratory are described. Moreover, the measurement results of the participants and the analytical methods used for the determination of MTBE are presented and the correlation between selected method parameters and data quality is discussed.

Photocatalytic degradation of aqueous methyl-tert-butyl-ether (MTBE) in a supported-catalyst reactor

Contamination of groundwater by methyl-tert-butyl ether (MTBE) poses increasing problems to water companies. Here we demonstrate the feasibility of using a cylindrical, supported-catalyst reactor for photocatalytic degradation of MTBE in water. It was shown that photocatalytic degradation of MTBE follows pseudo first-order kinetics. The maximum reaction rate constant observed was 0.47 hr−1. The reaction rate increases linearly with increasing light intensity. It was also found that the reaction rate is linearly proportional to the ratio of catalyst surface area to volume of reactor. Complete degradation of MTBE was reached with an excess supply of oxygen.