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1.
The potential for using Fenton's reagent (H 2O 2 + Fe 2+) as an advanced oxidation pretreatment process to enhance microbial transformation of two model polycyclic aromatic hydrocarbons,
anthracene and benzo[a]pyrene, in an aqueous system was evaluated. Fenton's reagent at a concentration of 0.5% H 2O 2 and 10 mM Fe 2+ (molar ratio, 15:1) was most effective in transforming anthracene at pH 4. Application of non-ionic surfactants during Fenton's
pre-treatment was found to be more effective in the transformation of both anthracene and benzo[a]pyrene. The extent of removal
of substrates by a combined Fenton's–biotreatment was 2–4 times higher than with Fenton's treatment or biotreatment alone.
In a chemical–biological treatment train, 48 h of Fenton's pre-treatment in the presence of a non-ionic surfactant, followed
by 7 days of biological treatment resulted in 80–85% removal of PAHs (100 ppm).
Electronic Publication 相似文献
2.
This study describes the removal of polycyclic aromatic hydrocarbons (PAHs) from creosote oil contaminated soil by modified
Fenton’s reaction in laboratory-scale column experiments and subsequent aerobic biodegradation of PAHs by indigenous bacteria
during incubation of the soil. The effect of hydrogen peroxide addition for 4 and 10 days and saturation of soil with H 2O 2 on was studied. In both experiments the H 2O 2 dosage was 0.4 g H 2O 2/g soil. In completely H 2O 2−saturated soil the removal of PAHs (44% within 4 days) by modified Fenton reaction was uniform over the entire soil column.
In non-uniformly saturated soil, PAH removal was higher in completely saturated soil (52% in 10 days) compared to partially
saturated soil, with only 25% in 10 days. The effect of the modified Fenton’s reaction on the microbial activity in the soil
was assessed based on toxicity tests towards Vibrio fischeri, enumeration of viable and dead cells, microbial extracellular enzyme activity, and oxygen consumption and carbon dioxide
production during soil incubation. During the laboratory-scale column experiments, the toxicity of column leachate towards
Vibrio fischeri increased as a result of the modified Fenton’s reaction. The activities of the microbial extracellular enzymes acetate- and
acidic phosphomono-esterase were lower in the incubated modified Fenton’s treated soil compared to extracellular enzyme activities
in untreated soil. Abundance of viable cells was lower in incubated modified Fenton treated soil than in untreated soil. Incubation
of soil in serum bottles at 20 °C resulted in consumption of oxygen and formation of carbon dioxide, indicating aerobic biodegradation
of organic compounds. In untreated soil 20–30% of the PAHs were biodegraded during 2 months of incubation. Incubation of chemically
treated soil slightly increased PAH-removal compared to PAH-removal in untreated soil. 相似文献
3.
The effect of modified Fenton oxidation using synthesized hematite nanoparticles and sodium pyrophosphate as a chelating agent was investigated for the pretreatment of pyrene-contaminated soil in a sequence with bioremediation. Synthesized hematite nanoparticles comprised hematite according to X-ray diffraction (XRD) analysis, with particle sizes ranging between 28 and 55 nm. Three pyrene-degrading bacteria, Bacillus cereus, Acidovorax wohlfahrtii, and Bacillus thuringiensis, were isolated from hydrocarbon-contaminated soil and used as inoculums for the bioremediation. A sequence of modified Fenton oxidation-bioremediation using a synthesized hematite nanoparticles dosage of 30 mM and H 2O 2 concentration of 300 mM significantly enhanced the pyrene removal rate to 96%, 87%, and 82% compared to 88%, 59%, and 37%, which were obtained during the bioremediation alone for synthetically fresh, aged, and naturally contaminated soil with initial pH 7, respectively. The results of kinetic studies indicated that modified Fenton oxidation of pyrene-contaminated soil was best fitted with a pseudo-first order kinetic model. Consequently, a sequence of modified Fenton-bioremediation can effectively remediate polycyclic aromatic hydrocarbon-contaminated sites in a shorter reaction time than bioremediation alone. 相似文献
4.
The effectiveness of the metal oxide nanoparticles viz. CuO and Fe 2O 3 as antibacterial agents against multidrug resistant biofilm forming bacteria was evaluated. CuO nanoparticles were also experimented for antibiofilm and time kill assay. The CuO displayed maximum antibacterial activity with zone of inhibition of (22 ± 1) mm against methicillin resistant Staphylococcus aureus (MRSA) followed by Escherichia coli (18 ± 1) mm. The Fe 2O 3 showed the zone of inhibition against MRSA of (14 ± 1) mm followed by E. coli (12 ± 1) mm. CuO proved to be more toxic than Fe 2O 3 nanoparticles showing significantly high antibacterial activity and found to possess dose dependent antibiofilm properties. 相似文献
5.
The effect of lactic acid (lactate) on Fenton based hydroxyl radical ( ·OH) production was studied by spin trapping, ESR, and fluorescence methods using DMPO and coumarin-3-carboxylic acid (3-CCA) as the ·OH traps respectively. The ·OH adduct formation was inhibited by lactate up to 0.4mM (lactate/iron stoichiometry = 2) in both experiments, but markedly enhanced with increasing concentrations of lactate above this critical concentration. When the H 2O 2 dependence was examined, the DMPO-OH signal was increased linearly with H 2O 2 concentration up to 1 mM and then saturated in the absence of lactate. In the presence of lactate, however, the DMPO-OH signal was increased further with higher H 2O 2 concentration than 1 mM, and the saturation level was also increased dependent on lactate concentration. Spectroscopic studies revealed that lactate forms a stable colored complex with Fe 3+ at lactate/Fe 3+ stoichiometry of 2, and the complex formation was strictly related to the DMPO-OH formation. The complex formation did not promote the H 2O 2 mediated Fe 3+ reduction. When the Fe 3+-lactate (1:2) complex was reacted with H 2O 2, the initial rate of hydroxylated 3-CCA formation was linearly increased with H 2O 2 concentrations. All the data obtained in the present experiments suggested that the Fe 3+-lactate (1:2) complex formed in the Fenton reaction system reacts directly with H 2O 2 to produce additional ·OH in the Fenton reaction by other mechanisms than lactate or lactate/Fe 3+ mediated promotion of Fe 3+/Fe 2+ redox cycling. 相似文献
6.
A novel amperometric biosensor for xanthine was developed based on covalent immobilization of crude xanthine oxidase (XOD) extracted from bovine milk onto a hybrid nanocomposite film via glutaraldehyde. Toward the preparation of the film, a stable colloids solution of core–shell Fe 3O 4/polyaniline nanoparticles (PANI/Fe 3O 4 NPs) was dispersed in solution containing chitosan (CHT) and H 2PtCl 6 and electrodeposited over the surface of a carbon paste electrode (CPE) in one step. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrophotometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used for characterization of the electrode surface. The developed biosensor (XOD/CHT/Pt NPs/PANI/Fe 3O 4/CPE) was employed for determination of xanthine based on amperometric detection of hydrogen peroxide (H 2O 2) reduction at –0.35 V (vs. Ag/AgCl). The biosensor exhibited a fast response time to xanthine within 8 s and a linear working concentration range from 0.2 to 36.0 μM ( R2 = 0.997) with a detection limit of 0.1 μM (signal/noise [S/N] = 3). The sensitivity of the biosensor was 13.58 μA μM −1 cm −2. The apparent Michaelis–Menten ( Km) value for xanthine was found to be 4.7 μM. The fabricated biosensor was successfully applied for measurement of fish and chicken meat freshness, which was in agreement with the standard method at the 95% confidence level. 相似文献
7.
The scope of this study is to achieve carrier-bound immobilization of catalase onto magnetic particles (Fe 3O 4 and Fe 2O 3NiO 2 · H 2O) to specify the optimum conditions of immobilization. Removal of H 2O 2 and the properties of immobilized sets were also investigated. To that end, adsorption and then cross-linking methods onto magnetic particles were performed. The optimum immobilization conditions were found for catalase: immobilization time (15 min for Fe 3O 4; 10 min for Fe 2O 3NiO 2 · H 2O), the initial enzyme concentration (1 mg/mL), amount of magnetic particles (25 mg), and glutaraldehyde concentration (3%). The activity reaction conditions (optimum temperature, optimum pH, pH stability, thermal stability, operational stability, and reusability) were characterized. Also kinetic parameters were calculated by Lineweaver–Burk plots. The optimum pH values were found to be 7.0, 7.0, and 8.0 for free enzyme, Fe 3O 4-immobilized catalases, and Fe 2O 3NiO 2 · H 2O-immobilized catalases, respectively. All immobilized catalase systems displayed the optimum temperature between 25 and 35°C. Reusability studies showed that Fe 3O 4-immobilized catalase can be used 11 times with 50% loss in original activity, while Fe 2O 3NiO 2 · H 2O-immobilized catalase lost 67% of activity after the same number of uses. Furthermore, immobilized catalase systems exhibited improved thermal and pH stability. The results transparently indicate that it is possible to have binding between enzyme and magnetic nanoparticles. 相似文献
8.
Dissolved Fe(II) and humic acid (HA) were pre-impregnated into contaminated soil to catalyze hydrogen peroxide to remove crude oil (CO). The effects of parameters such as initial Fe(II), HA and H 2O 2 concentrations on the oxidation of total petroleum hydrocarbon (TPH) were investigated using response surface methodology based on Box–Behnken design. The rate of hydrogen peroxide decomposition is decreased by pre-impregnating with dissolved Fe(II) + HA compared with only pre-impregnated Fe(II) and modified Fenton (MF). Oxygen evolution is the predominant route of hydrogen peroxide decomposition at natural pH. Unlike O 2 evolution, the kinetics of hydroxyl radical (OH ?) production are clearly uncoupled from H 2O 2 decay in these systems. The steady-state hydroxyl radical production rate is higher in the systems with pre-impregnated dissolved Fe(II) and HA, and more significance is the decrease in detectable TPH (70.84% removal efficiency) when soil is pre-impregnated with dissolved 25 mM Fe(II) + 0.7 mg/mL HA, and with the application of 700 mM H 2O 2, possibly due to hydrogen peroxide catalyzed by the iron of this complex (CO-HA–Fe(II)) producing hydroxyl radical in close proximity to the CO. Meanwhile, the removal efficiency of C 21–C 30 is up to 65.69%, which is 2.6 times higher than that of the MF (25.52%). 相似文献
9.
In situ cell separation and immobilization of bacterial cells for biodesulfurization were developed by using superparamagnetic Fe 3O 4 nanoparticles (NPs). The Fe 3O 4 NPs were synthesized by coprecipitation followed by modification with ammonium oleate. The surface-modified NPs were monodispersed and the particle size was about 13 nm with 50.8 emu/g saturation magnetization. After adding the magnetic fluids to the culture broth, Rhodococcus erythropolis LSSE8-1 cells were immobilized by adsorption and then separated with an externally magnetic field. The maximum amount of cell mass adsorbed was about 530 g dry cell weight/g particles to LSSE8-1 cells. Analysis showed that the nanoparticles were strongly absorbed to the surface and coated the cells. Compared to free cells, the coated cells not only had the same desulfurizing activity but could also be easily separated from fermentation broth by magnetic force. Based on the adsorption isotherms and Zeta potential analysis, it was believed that oleate-modified Fe 3O 4 NPs adsorbed bacterial cells mainly because of the nano-size effect and hydrophobic interaction. 相似文献
10.
The white rot fungus, Pleurotus ostreatus, metabolized four soil adsorbed polycyclic aromatic hydrocarbons: 50% of pyrene (0.1 mg g –1 dry soil), 68% of anthracene and 63% of phenanthrene were mineralized after 21 d. Biodegradation was increased to 75%, 80% and 75%, respectively of the initial concentration when 0.15% Tween 40 was added. Biodegradation of pyrene in the presence of surfactant and H 2O 2 (1.0 mM) was 90%. Benz[a]pyrene was also oxidized by Pleurotus ostreatus but it is not mineralized. 相似文献
11.
Objective Thialkalivibrio versutus D301 cells were immobilized on Fe3O4 nanoparticles (NPs) synthesized by an improved chemical coprecipitation method and modified with 3-aminopropyltriethoxysilane (APTES), then the immobilized cells were used in sulfur oxidation.ResultsThe prepared Fe3O4–APTES NPs had a narrow size distribution (10 ± 2 nm) and were superparamagnetic, with a saturation magnetization of 60.69 emu/g. Immobilized cells had a saturation magnetization of 34.95 emu/g and retained superparamagnetism. The optimum conditions for cell immobilization were obtained at pH 9.5 and 1 M Na+. The immobilization capacity of Fe3O4–APTES NPs was 7.15 g DCW/g-NPs that was 2.3-fold higher than that of Fe3O4 NPs. The desulfurization efficiency of the immobilized cells was close to 100%, having the same sulfur oxidation capacity as free cells. Further, the immobilized cells could be reused at least eight times, retaining more than 85% of their desulfurization efficiency.ConclusionImmobilization of cells with the modified magnetic NPs efficiently increased cell controllability, have no effect on their desulfurization activity and could be effectively used in large-scale industrial applications. 相似文献
12.
With the ongoing commercialization of nanotechnology products, the increasing use of engineered nanoparticles (NPs) could lead potentially to environmental risks. This study investigated the dynamic influences of three iron-based NPs (Fe 0, Fe 3O 4, and Fe 2O 3) applied into a red soil (RS) and a Wushan soil (WS) with different application rates (2 to 6 g kg ?1) on soil physicochemical properties such as pH, dissolved organic carbon (DOC), available ammonium nitrogen (NH 4 +-N), available phosphorus (AP), and enzymatic activities. The results showed that the addition of Fe 0 NPs increased DOC and available NH 4 +-N, but significantly decreased AP, while Fe 3O 4 and Fe 2O 3 NPs slightly reduced soil pH in both soils and significantly declined available NH 4 +-N in the WS and AP in the RS. No significant difference was observed between the effects of Fe 3O 4 and Fe 2O 3 NPs on soil properties except AP in the RS. All iron-based NPs decreased the activities of urease and acid phosphatase in both soils. The effects on soil physicochemical properties, especially available NH 4 +-N and AP induced by iron-based NPs, varied greatly with soil types. These results implied that cautions should be paid for the environmental application of iron-based NPs, especially iron oxide NPs in soils. 相似文献
13.
Soil from a pulse cultivated farmers land of Odisha, India, have been subjected to incubation studies for 40 consecutive days, to establish the impact of various nitrogenous fertilizers and water filled pore space (WFPS) on green house gas emission (N 2O & CH 4). C 2H 2 inhibition technique was followed to have a comprehensive understanding about the individual contribution of nitrifiers and denitrifiers towards the emission of N 2O. Nevertheless, low concentration of C 2H 2 (5 ml: flow rate 0.1 kg/cm 2) is hypothesized to partially impede the metabolic pathways of denitrifying bacterial population, thus reducing the overall N 2O emission rate. Different soil parameters of the experimental soil such as moisture, total organic carbon, ammonium content and nitrate–nitrogen contents were measured at regular intervals. Application of external N-sources under different WFPS conditions revealed the diverse role played by the indigenous soil microorganism towards green house gas emission. Isolation of heterotrophic microorganisms ( Pseudomonas) from the soil samples, further supported the fact that denitrification might be prevailing during specific conditions thus contributing to N 2O emission. Statistical analysis showed that WFPS was the most influential parameter affecting N 2O formation in soil in absence of an inhibitor like C 2H 2. 相似文献
14.
The generation and depletion of dissolved inorganic carbon (DIC) in a close-environment ureolytic biocalcification process by Bacillus pasteurii was evaluated. Three experimental sets, each containing 50 mM urea, were amended with either 50 mM Ca 2+ before incubation (set–I) or 100 mM Ca 2+ after 24-h incubation (set-II) or no Ca 2+ addition (urea control). Extent of ureolysis was maximum in urea control set (88%), followed by set–II (66.4%) and set–I (35.2%). Out of total DIC generated from microbial metabolism and ureolysis in set–I (277.6 mg/l) and set–II (464.9 mg/l), only about 54.1 mg/l and 180.1 mg/l was precipitated as CaCO3, whereas 189.3 mg/l and 231.3 mg/l DIC escaped into headspace, respectively. Increased time separation between ureolysis and calcification steps in set–II and higher dosage of Ca2+ resulted in synergistic improvement in DIC capture. In a reusability test, the spent supernatant from set–II could precipitate additional amount CaCO3from CO2saturated water,which was twice as much as that of the fresh media control. 相似文献
15.
Biosurfactants are considered to facilitate PAHs dissolution in soil slurries for bioremediation applications. In this work, the carbon and nitrogen sources, pH, C/N ratio, and salinity, were considered for optimization of biosurfactant production by Pseudomonas aeruginosa SP4 isolate to enhance pyrene removal from the contaminated soil. Analysis of ANOVA indicated that the carbon source was the most effective factor, followed by pH, nitrogen source, C/N ratio, and salinity. Taguchi experimental design proposed the optimum operating conditions of olive oil, NH 4NO 3, C/N ratio of 5, salinity of 0.5%, and pH 7. Applying the conditions determined by Taguchi design led to a production yield of 452 mg L ?1 (13% improvement) at the optimum conditions. The main characteristics of produced biosurfactant included the critical micelle concentration (CMC) of 60 mg L ?1 and liquid medium surface tension of 29.5 mN m ?1. Produced biosurfactant was used for bioremediation of soil artificially contaminated with 500 mg kg ?1 of pyrene. Following the addition of 250 mg L ?1 biosurfactant, the pyrene removal of 84.6% was obtained compared to 59.8% for control sample without any surfactant. 相似文献
16.
In many legume nodules, the H 2 produced as a byproduct of N 2 fixation diffuses out of the nodule and is consumed by the soil. To study the fate of this H 2 in soil, a H 2 treatment system was developed that provided a 300 cm 3 sample of a soil:silica sand (2:1) mixture with a H 2 exposure rate (147 nmol H 2 cm –3hr –1) similar to that calculated exist in soils located within 1–4 cm of nodules (30–254 nmol H 2 cm –3hr –1). After 3 weeks of H 2 pretreatment, the treated soils had a K m and V max for H 2 uptake (1028 ppm and 836 nmol cm –3 hr –1, respectively) much greater than that of control, air-treated soil (40.2 ppm and 4.35 nmol cm –3 hr –1, respectively). In the H 2 treated soils, O 2, CO 2 and H 2 exchange rates were measured simultaneously in the presence of various pH 2. With increasing pH 2, a 5-fold increase was observed in O 2 uptake, and CO 2 evolution declined such that net CO 2 fixation was observed in treatments of 680 ppm H 2 or more. At the H 2 exposure rate used to pretreat the soil, 60% of the electrons from H 2 were passed to O 2, and 40% were used to support CO 2 fixation. The effect of H 2 on the energy and C metabolism of soil may account for the well-known effect of legumes in promoting soil C deposition. 相似文献
17.
Summary Ethylene (C 2H 4) accumulation in flooded soil was related to oxygen (O 2), redox potential (Eh), and flooding rate. The water status response of tobacco ( Nicotiana, tabacum L.) to these conditions was evaluated from stem diameter, relative water content, leaf water potential, and C 2H 4 content of leaf tissue. Treatments were: flooded with either 0,5, or 15 cm of water per day for 6 days. By the third day, O 2 in the soil decreased to less than 9% in treatments flooded with 5 or 15 cm of water. When O 2 in the soil air was less than 9% and redox potential (Eh) was less than +150 mv, most of the soil air samples contained some C 2H 4 and 16% contained more than 6 ppm. Very little C 2H 4 was present in soil air when O 2 exceeded 9%. Tobacco leaf C 2H 4 peaked 3 days after flooding and then declined to the preflooding level a day later, one day ahead of the rapid increase in soil C 2H 4. Wilting developed progressively beginning with the rise of C 2H 4 in the soil; leaf water potential, stem diameter, and relative leaf water content all were decreased. Soil-and plant-produced C 2H 4 are suggested as factors in reducing root permeability and increasing resistance to water uptake by tobacco.Contribution of the USDA-SEA/AR, in cooperation with the South Carolina Experiment Station. 相似文献
18.
The presence of 2 mM bicarbonate in the incubation medium induced stomatal closure in abaxial epidermis of Arabidopsis. Exposure to 2 mM bicarbonate elevated the levels of H 2O 2 in guard cells within 5 min, as indicated by the fluorescent probe, dichlorofluorescein diacetate (H 2DCF-DA). Bicarbonate-induced stomatal closure as well as H 2O 2 production were restricted by exogenous catalase or diphenylene iodonium (DPI, an inhibitor of NAD(P)H oxidase). The reduced
sensitivity of stomata to bicarbonate and H 2O 2 production in homozygous atrbohD/F double mutant of Arabidopsis confirmed that NADP(H) oxidase is involved during bicarbonate induced ROS production in guard cells. The production of H 2O 2 was quicker and greater with ABA than that with bicarbonate. Such pattern of H 2O 2 production may be one of the reasons for ABA being more effective than bicarbonate, in promoting stomatal closure. Our results
demonstrate that H 2O 2 is an essential secondary messenger during bicarbonate induced stomatal closure in Arabidopsis. 相似文献
19.
During two intensive field campaigns in summer and autumn 2004 nitrogen (N 2O, NO/NO 2) and carbon (CO 2, CH 4) trace gas exchange between soil and the atmosphere was measured in a sessile oak ( Quercus petraea (Matt.) Liebl.) forest in Hungary. The climate can be described as continental temperate. Fluxes were measured with a fully automatic measuring system allowing for high temporal resolution. Mean N 2O emission rates were 1.5 μg N m −2 h −1 in summer and 3.4 μg N m −2 h −1 in autumn, respectively. Also mean NO emission rates were higher in autumn (8.4 μg N m −2 h −1) as compared to summer (6.0 μg N m −2 h −1). However, as NO 2 deposition rates continuously exceeded NO emission rates (−9.7 μg N m −2 h −1 in summer and −18.3 μg N m −2 h −1 in autumn), the forest soil always acted as a net NO
x
sink. The mean value of CO 2 fluxes showed only little seasonal differences between summer (81.1 mg C m −2 h −1) and autumn (74.2 mg C m −2 h −1) measurements, likewise CH 4uptake (summer: −52.6 μg C m −2 h −1; autumn: −56.5 μg C m −2 h −1). In addition, the microbial soil processes net/gross N mineralization, net/gross nitrification and heterotrophic soil respiration as well as inorganic soil nitrogen concentrations and N 2O/CH 4 soil air concentrations in different soil depths were determined. The respiratory quotient (ΔCO 2 resp ΔO 2 resp−1) for the uppermost mineral soil, which is needed for the calculation of gross nitrification via the Barometric Process Separation (BaPS) technique, was 0.8978 ± 0.008. The mean value of gross nitrification rates showed only little seasonal differences between summer (0.99 μg N kg −1 SDW d −1) and autumn measurements (0.89 μg N kg −1 SDW d −1). Gross rates of N mineralization were highest in the organic layer (20.1–137.9 μg N kg −1 SDW d −1) and significantly lower in the uppermost mineral layer (1.3–2.9 μg N kg −1 SDW d −1). Only for the organic layer seasonality in gross N mineralization rates could be demonstrated, with highest mean values in autumn, most likely caused by fresh litter decomposition. Gross mineralization rates of the organic layer were positively correlated with N 2O emissions and negatively correlated with CH 4 uptake, whereas soil CO 2 emissions were positively correlated with heterotrophic respiration in the uppermost mineral soil layer. The most important abiotic factor influencing C and N trace gas fluxes was soil moisture, while the influence of soil temperature on trace gas exchange rates was high only in autumn. 相似文献
20.
Red lead (Pb 3O 4) has been extensively used in the past in anti-corrosion paints for the protection of steel constructions such as electricity pylons or bridges. Until recently, little has been known about the behavior of these Pb compounds in soils. Therefore, three pylon soils and six red lead anti-corrosion paints were characterized in terms of solubility, Pb mineral composition, extractability, sorption and desorption, and the chemical speciation of Pb in soil extracts. The pylon soils were characterized by moderate total Pb concentrations (≈700 mg kg ?1), while NH 4NO 3 extractable Pb was exceptionally high (up to 15% of total Pb). In soil extracts, the free Pb 2+ fraction ranged from 33 to 81% of total soluble Pb. The equilibrium concentration of Pb derived from Pb 3O 4 in ultra-pure water reached 68.5 mg L ?1. This high solubility explains the observed high extractability in soils and contradicts earlier reports of much lower water solubilities of the compound. 相似文献
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