Initial Methyl Tert-butyl Ether Concentration Research Articles

Photocatalytic Removal of Methyl Tert-Butyl Ether by C-N-TiO2 Nanoparticles from Aqueous Solution

BackgroundThe elimination of methyl tert-butyl ether (MTBE) from water resources remains a main environmental concern. In the present study, photo-assissted process for removal of MTBE was examined in the solutions containing C-N-TiO2 nanoparticles under UV irradiation in the batch mode.MethodsThe effects of operational factors such as pH, initial catalyst concentration, and initial MTBE concentration on MTBE removal was investigated.ResultsThe optimum degradation condition for MTBE was obtained at pH 7, catalyst load of 100 mg/L, air flow rate = 0.1 L/min and C0 = 5 mg/L with 73 percent degradation of MTBE at 60 min. In addition, Analytical profiles on MTBE removal were based on the first-order kinetics model. However, the removal rate decreased by increasing initial concentration of MTBE.ConclusionThe findings showed that UV/C-N-TiO2 system is an efficient method for MTBE degradation from aqueous solution.

Kinetic modeling of Methyl Tert-Butyl Ether (MTBE) removal by bacterial isolated from contaminated soils

ABSTRACT Methyl Tert-Butyl Ether(MTBE) is among oxygenised additives to gasoline, which has high solubility and leads to pollution of water resources. So far, the microbial species affecting the of high MTBEconcentrationsremoval have been less investigated. This study aimed to remove high concentrations of MTBEusing isolated bacteriafrom contaminatedsoil with petroleum compounds in southern regions of Iran and determine their kinetics. After isolating the bacteria and determining their growth in different concentrations, the effects of the following parameters on the removal percentage were examined: incubation time = 1–7 days, pH = 5.0–7.0, and 9.0, initial MTBE concentration = 1000–5000 mg/L, and C: N:P. Then, the four strains with high efficiency were selected, and their kinetic were analysed by zero-order, first-order, and second-order models. The results showed that the highest growth in MTBE concentration (50,000 mg/L) was observed for Acinetobacter sp, Bacillus sp, Ochrobactrum sp, and Sphingomonas sp. after four days. Then, Ochrobactrum sp.was used as a pure strain as well as a microbial consortium for the next steps, including the effects of nutrient ratio and initial MTBE concentration. In this study, the optimal conditions for incubation time and the initial MTBE concentration were 72 hours and 5000 mg/L, respectively. The kinetic modeling indicated that the second-order model (R2 = 0.95, Root Mean Squared Error = 0.012) and the Micheal-Menten model (R2 = 0.99) were the best modelfor MTBE biodegradation. Overall, the results indicated that pure Ochrobactrum sp. and a microbial consortium consisting of resistant bacteria at high MTBEconcentrations could remove MTBE> 90%.

Modeling the efficiency of TiO2 photocatalytic degradation of MTBE in contaminated water: a support vector regression approach

Methyl tert-Butyl Ether (MTBE) is one of the common environmental contaminants that pose severe risks to human health and the environment. Due to the detrimental effects of MTBE, many efforts have been devoted towards decontamination of wastewater containing MTBE. Most of the reports on the treatment of MTBE are experimental based, which requires studying the effect of several factors such as dosage of the photocatalyst, pH of the medium, the initial concentration of contaminant and the contact time on degradation efficiency in MTBE contaminated waters. Although, this approach is highly dependable and often leads to new insights. However, because the degradation efficiency is influenced by multiple factors, performing experiments to investigate the effect of these factors often increases the experimental burden, thus requiring more time and materials consumption to achieve desirable results. Herein, we propose a computational intelligent strategy to mitigate these challenges. In this contribution, the degradation efficiencies of MTBE in the presence of TiO2/UV were modeled under various experimental conditions using the support vector regression model. The model was built using experimental data comprising of inputs such as TiO2 dose, initial MTBE concentration, UV wavelength and contact time. Remarkably, the developed model exhibits significant accuracy as determined from the values of correlation coefficient (98.27%) and root means square error (5.53). In addition, it was determined that the achievable optimum conditions for degradation of 0.5–100 ppm MTBE-contaminated water were 2.4 g/L of TiO2 dose with UV radiation, a solution pH of 3 and treatment time of 2 h. This study will be useful in the experimental design of treatment for MTBE, consequently reducing the time spent on running experiments and at the same time ensuring efficient use of resources for treatment of MTBE contaminated water.

Adsorption of methyl tert-butyl ether (MTBE) onto ZSM-5 zeolite: Fixed-bed column tests, breakthrough curve modelling and regeneration

ZSM-5, as a hydrophobic zeolite, has a good adsorption capacity for methyl tert-butyl ether (MTBE) in batch adsorption studies. This study explores the applicability of ZSM-5 as a reactive material in permeable reactive barriers (PRBs) to decontaminate the MTBE-containing groundwater. A series of laboratory scale fixed-bed column tests were carried out to determine the breakthrough curves and evaluate the adsorption performance of ZSM-5 towards MTBE under different operational conditions, including bed length, flow rate, initial MTBE concentration and ZSM-5 dosage, and regeneration tests were carried out at 80, 150 and 300 °C for 24 h. Dose-Response model was found to best describe the breakthrough curves. MTBE was effectively removed by the fixed-bed column packed with a ZSM-5/sand mixture with an adsorption capacity of 31.85 mg g−1 at 6 cm bed length, 1 mL min−1 flow rate, 300 mg L−1 initial MTBE concentration and 5% ZSM-5 dosage. The maximum adsorption capacity increased with the increase of bed length and the decrease of flow rate and MTBE concentration. The estimated kinetic parameters can be used to predict the dynamic behaviour of column systems. In addition, regeneration study shows that the adsorption capacity of ZSM-5 remains satisfactory (>85%) after up to four regeneration cycles.

Treating MTBE-contaminated water using sewage sludge-derived activated carbon.

In this study, sewage sludge-derived activated carbon (SDAC) was synthesized, characterized, and tested for its potential as an adsorbent of methyl tert-butyl ether (MTBE). The SDAC was produced by activating the sludge with zinc chloride and subsequently subjected to various ranges of pyrolytic temperatures. It was then characterized using SEM/EDX, BET, and TGA. The SEM-EDX analyses showed that impurities like Fe, Al, Mg, Mn, Ca, and Na of the raw sludge were removed by the higher pyrolytic temperature and acid-washing procedures. TGA showed the thermal stability of the produced material. Results of the BET revealed a significant increase in surface area of the sludge from 1.5m2/g to 385m2/g after acid washing. The MTBE removal efficiency of 70% was achieved after 60min with 2g/L of SDAC at pH6, and initial MTBE concentration of 1ppm. The adsorption kinetics of SDAC fitted into pseudo-second-order reactions. This work demonstrated a beneficial use of a bio-waste material (sewage sludge) in water treatment technologies.

Kinetic and equilibrium modelling of MTBE (methyl tert-butyl ether) adsorption on ZSM-5 zeolite: Batch and column studies

The intensive use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in serious environmental problems due to its high solubility, volatility and recalcitrance. The feasibility of permeable reactive barriers (PRBs) with ZSM-5 type zeolite as a reactive medium was explored for MTBE contaminated groundwater remediation. Batch adsorption studies showed that the MTBE adsorption onto ZSM-5 follows the Langmuir model and obeys the pseudo-second-order model with an adsorption capacity of 53.55 mg g−1. The adsorption process reached equilibrium within 24 h, and MTBE was barely desorbed with initial MTBE concentration of 300 mg L−1. The mass transfer process is found to be primarily controlled by pore diffusion for MTBE concentrations from 100 to 600 mg L−1. pH has little effect on the maximum adsorption capacity in the pH range of 2–10, while the presence of nickel reduces the capacity with Ni concentrations of 2.5–25 mg L−1. In fixed-bed column tests, the Dose-Response model fits the breakthrough curve well, showing a saturation time of ∼320 min and a removal capacity of ∼18.71 mg g−1 under the conditions of this study. Therefore, ZSM-5 is an extremely effective adsorbent for MTBE removal and has a huge potential to be used as a reactive medium in PRBs.

Response surface analysis of photocatalytic degradation of methyl tert-butyl ether by core/shell Fe3O4/ZnO nanoparticles

The degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous solution of coated ZnO onto magnetite nanoparticale based on an advanced photocatalytic oxidation process. The photocatalysts were synthesized by coating of ZnO onto magnetite using precipitation method. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibration sample magnetometer (VSM). Besides, specific surface area was also determined by BET method. The four effective factors including pH of the reaction mixture, Fe3O4/ZnO magnetic nanoparticles concentration, initial MTBE concentration and molar ratio of [H2O2]/ [MTBE] were optimized using response surface modeling (RSM). Using the four-factor-three-level Box–Behnken design, 29 runs were designed considering the effective ranges of the influential factors. The optimized values for the operational parameters under the respective constraints were obtained at PH of 7.2, Fe3O4/ZnO concentration of 1.78 g/L, initial MTBE concentration of 89.14 mg/L and [H2O2]/ [MTBE] molar ratio of 2.33. Moreover, kinetics of MTBE degradation was determined under optimum condition. The study about core/shell magnetic nanoparticles (MNPs) recycling were also carried out and after about four times, the percentage of the photocatalytic degradation was about 70%.

Degradation of methyl tert-butyl ether (MTBE) in water by glow discharge plasma

This study evaluated the ability of the glow discharge plasma (GDP) technique to degrade methyl tert-butyl ether (MTBE) in an aqueous solution. The results showed that a large amount of hydrogen peroxide and highly active *OH free radicals were produced during the treatment. Various experimental parameters including discharge current, initial MTBE concentration and initial pH played significant roles on MTBE degradation. In addition, Fe2+ had a catalytic effect on the degradation of MTBE, which is potentially attributable to the reaction between Fe3+ and the hydrated electron. It was also confirmed that GDP was comparable to electrocatalytic oxidation and high-density plasma and more efficient than photocatalytic degradation techniques. These results suggest that GDP may become a competitive MTBE wastewater treatment technology.

Adsorption Studies for the Removal of Methyl tert-Butyl Ether on Various Commercially Available GACs from an Aqueous Medium

This study highlights the potential of four commercially available granular-activated carbons (GACs) to remove Methyl tert-butyl ether (MTBE) from an aqueous medium. Thermodynamics and kinetics parameters were elucidated. The FT-IR spectra showed decrease in peak intensity after the adsorption. The decline in the peak intensity revealed that the adsorption occurred on available active sites over the surface of the GACs. The adsorption on GACs was maximum in the pH range 7–8, with maximum adsorption capacity (47.82 mg/g, pH 8) observed with CGAC. The contact time studies showed optimum adsorption of MTBE on CGAC (67.05 mg/g) at 300 mg/L initial MTBE concentration. The applicability of the Freundlich model illustrates a multilayer adsorption process. The adsorption process is endothermic in nature. The kinetics studies showed that the adsorption follows the pseudo-second-order model on GACs and the intraparticle diffusion is the rate-controlling mechanism on CGAC.

Spatial Variation in MTBE Biodegradation Activity of Aquifer Solids Samples Collected in the Vicinity of a Flow‐Through Aerobic Biobarrier

The spatial variation in methyl tert‐butyl ether (MTBE) biodegradation activity of aquifer solids samples collected in the vicinity of a flow‐through aerobic biobarrier was assessed through use of standard laboratory microcosms. These were prepared by collecting soil cores at a range of locations and depths along different flow paths through the biobarrier. Sections of core samples were placed in sealed bottles with MTBE‐free groundwater from the site. The groundwater was filtered to remove microbes, and sparged with O2. The initial MTBE concentration in the microcosms was adjusted to about 1 mg/L. Biodegradation activity was characterized by the magnitude of MTBE concentration reductions occurred over 4 weeks relative to control microcosms. Sampling locations and depths were selected to allow investigation of relationships between MTBEdegrading activity and dissolved oxygen (DO) concentration, MTBE, soil type, and initial microbial conditions (biostimulated vs. bioaugmented). The results suggest a relatively wide‐spread presence of MTBE‐degrading microbial consortia, with varying levels of MTBE‐degrading activity. Significant changes in activity were observed over 0.3‐m vertical distances in the same location; for example, cores from the most upgradient sampling locations contained sections with no discernible MTBEbiodegradation over 4 weeks, as well as sections that achieved order‐of‐magnitude MTBE concentration reductions within 2 weeks. None of those cores, however, achieved MTBE biodegradation to nondetect levels (<0.005 mg/L), as was observed in some cores from downgradient locations. Cores from the bioaugmented regions had the highest frequency of MTBE biodegradation to nondetect levels among their sections suggesting a direct effect of the inoculum and its distribution when it was implanted. Most cores with no activity were associated with the upgradient, low‐DO, and high‐MTBE concentration field environments, but low‐DO field environments also yielded MTBE‐degrading samples. There were no other clear correlations between MTBE‐degrading activity in the microcosms and the local field environment conditions at the time of sampling.

Effect Factors on the Degradation of MTBE with Fenton Reagent

The fundamentals of the Fenton reagent-based degradation methyl tert-butyl ether (MTBE) in batch reactors under initially anaerobic conditions are discussed in this work, and the objective of the study was to elucidate the effect of the FR to MTBE molar ratio, pH, initial MTBE concentration, H 2 O 2 concentration and inorganic anions on MTBE decomposition. The results show that the added amount of FR proved to be an important controlling parameter of the overall MTBE degradation efficiency. Under the conditions investigated in the present study at pH 3.0 and equimolar ratio of Fe 2 + to H 2 O 2 , FR to MTBE molar ratio of 6:1 was the minimum required to achieve complete MTBE degradation. The MTBE decay curves at four different initial MTBE concentrations with a constant initial FR concentration, the decomposition ratio arrived by 90.8%, 82.3%, 71.6% and 41.8%, while the initial MTBE concentration at 10.0, 20.0, 40.0 and 60 mg/L, respectively. The amount of hydrogen peroxide has a positive influence on the degradation rate, at low peroxide levels, increasing the amount of hydrogen peroxide results in the generation of more hydroxyl radicals, and thereby enhances the decay rate of MTBE. Moreover, the Fenton reaction is extremely sensitive to the inorganic anions present in the solution. In the case of the PO 4 3 − ions, oxidation is clearly inhibited, but the addition of SO 4 2 − influences the reaction to a much smaller extent, the anions suppress the decomposition of MTBE in the following sequence: PO 4 3 − >HPO 4 2 − >H 2 PO 4 − >Cl − >SO 4 2 − .

The application of silicalite-1/fly ash cenosphere (S/FAC) zeolite composite for the adsorption of methyl tert-butyl ether (MTBE)

Silicalite-1/fly ash cenosphere (S/FAC) zeolite composite has been applied for batch adsorption of methyl tert-butyl ether (MTBE) from water systems. Here the key experimental conditions, including the ratio of initial MTBE concentration to the amount weight of S/FAC, adsorption time and temperature, have been discussed in detail. The results show that approximately 93–95% MTBE could be adsorbed with initial concentration of MTBE solution 1000 μg l −1. The column flow-through experiments also prove the high capacity of S/FAC composite for MTBE removal. The distinct advantages of S/FAC zeolite composite as adsorbent lie in (1) enhanced adsorption rate and capacity based on hierarchical micro and meso/macroporosity of S/FAC; (2) more easily operation and recycling process by assembly of nano-sized silicalite-1 zeolite on FAC support.

Effect of oxidant-to-substrate ratios on the degradation of MTBE with Fenton reagent

Prior studies have shown the effectiveness of Fenton reagent (FR) for degrading low concentrations (1.0–2.0 mg/L) of methyl tert-butyl ether (MTBE), similar to those found in contaminated groundwater. The present study investigates the effect of increasing FR doses on the extent of degradation and mineralization of a given initial MTBE concentration. The FR to MTBE molar ratio (FMMR) was the operating variable, and was investigated at values between 0.5:1 and 200:1. This approach provided sequential snapshots of the MTBE degradation process, which may help to improve the understanding of MTBE degradation with FR. The initial MTBE concentration (MTBE 0) was approximately 22.7 μM (∼2.0 mg/L), and FR was used in a 1:1 molar ratio of ferrous iron (Fe 2+) and hydrogen peroxide (H 2O 2). The concentrations of MTBE and the following main reaction byproducts: tert-butyl formate (TBF), tert-butyl alcohol (TBA), acetone and methyl acetate were determined from samples collected at specific intervals over a total reaction time of 1 h. Total organic carbon (TOC) was monitored to determine MTBE mineralization, and the total concentration of tert-butyl compounds (tBC) was monitored due to the suspected toxicity associated with this functional group. The results showed that the minimum FMMR necessary for achieving complete MTBE degradation was 20:1, but at that FMMR, TOC and tBC reduction were only 45.6% and 24.9%, respectively. Complete MTBE mineralization was not achieved in any case, even at FMMRs as high as 200:1, where only 63.3% of mineralization was observed (although tBC reduction reached 99.6%, since traces of TBA were still detected). These results confirm the relative inability of FR to achieve complete mineralization of a target substrate, even those that are highly reactive with the hydroxyl radical.

Photodegradation of methyl tert-butyl ether (MTBE) by UV/H 2O 2 and UV/TiO 2

Two UV-based advanced oxidation processes (AOPs), UV/H 2O 2 and UV/TiO 2, were tested in batch reactor systems to evaluate the removal efficiencies and optimal conditions for the photodegradation of methyl tert-butyl ether (MTBE). The optimal conditions at an initial MTBE concentration of 1 mM ([MTBE] 0 = 1 mM) were acidic and 15 mM H 2O 2 in UV/H 2O 2 system, and pH 3.0 and 2.0 g/l TiO 2 in UV/TiO 2 suspended slurries system under 254-nm UV irradiation. Under the optimal conditions, MTBE photodegradation during the initial period of 60 min in UV/H 2O 2 and UV/TiO 2 systems reached 98 and 80%, respectively. In both systems, MTBE photodegradation decreased with increasing [MTBE] 0. While MTBE photodegradation rates increased with increasing dosage of H 2O 2 (5–15 mM) and TiO 2 (0.5–3 g/l), further increase in the dosage of H 2O 2 (20 mM) or TiO 2 (4 g/l) adversely reduced the MTBE photodegradation. Pseudo first-order kinetics with regard to [MTBE] can be used to describe the MTBE photodegradation in both systems. The pseudo first-order rate constants linearly increased with the increase in the molar ratio of [H 2O 2] 0 to [MTBE] 0 in UV/H 2O 2 system and linearly increased with the decrease in [MTBE] 0 in UV/TiO 2 system.