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1.
Fe 2O 3 and CeO 2 modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg 0) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe 2O 3 and CeO 2, reaction temperature, and individual flue gas components including O 2, NO, SO 2, and H 2O (g) on Hg 0 removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe 2O 3 and 3 % CeO 2 on Fe3Ce3/AC, the Hg 0 removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O 2 and NO exhibited a promotional effect on Hg 0 removal, H 2O (g) exerted a suppressive effect, and SO 2 showed an insignificant inhibition without O 2 to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg 0 removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg 0 oxidation. 相似文献
2.
More attention has been paid to the deterioration of water bodies polluted by drinking water treatment sludge (DWTS) in recent years. It is important to develop methods to effectively treat DWTS by avoiding secondary pollution. We report herein a novel investigation for recovery of Si and Fe from DWTS, which are used for the synthesis of two iron oxide@SiO 2 composites for adsorption of reactive red X-3B (RRX-3B) and NaNO 2. The results show that Fe 3+ (acid-leaching) and Si 4+ (basic-leaching) can be successfully recovered from roasted DWTS. Whether to dissolve Fe(OH) 3 precipitation is the key point for obtaining Fe 3O 4 or γ-Fe 2O 3 particles using the solvothermal method. The magnetic characteristics of Fe 3O 4@SiO 2 (390.0 m 2 g ?1) or Fe 2O 3@SiO 2 (220.9 m 2 g ?1) are slightly influenced by the coated porous SiO 2 layer. Peaks of Fe–O stretching vibration (580 cm ?1) and asymmetric Si–O–Si stretching vibrations (1080 cm ?1) of Fe 3O 4@SiO 2 indicate the successful coating of a thin silica layer (20–150 nm). The adsorption capacity of RRX-3B and NaNO 2 by Fe 3O 4@SiO 2 is better than that of Fe 2O 3@SiO 2, and both composites can be recycled through an external magnetic field. This method is an efficient and environmentally friendly method for recycling DWTS. 相似文献
3.
Introduction In the present work, we explored the kinetics of dichlorvos (2,2-dichlorvinyl dimethyl phosphate, DDVP) decay through UV-A
light-induced TiO 2 photocatalysis at pH 4 and 9, and the formation of degradation intermediates and final products under specific experimental
conditions. Experimental observations and theoretical considerations allowed us to suggest the degradation mechanism of DDVP
by the UV/TiO 2 process in aqueous solution. 相似文献
4.
The purpose of this work was to study the efficiency of different treatments, based on the combination of O 3, H 2O 2, and TiO 2, on fresh surface water samples fortified with wild strains of Escherichia coli. Moreover, an exhaustive assessment of the influence of the different agents involved in the treatment has been carried out by kinetic modeling of E. coli inactivation results. The treatments studied were (i) ozonation (O 3), (ii) the peroxone system (O 3/0.04 mM H 2O 2), (iii) catalytic ozonation (O 3/1 g/L TiO 2), and (iv) a combined treatment of O 3/1 g/L TiO 2/0.04 mM H 2O 2. It was observed that the peroxone system achieved the highest levels of inactivation of E. coli, around 6.80 log after 10 min of contact time. Catalytic ozonation also obtained high levels of inactivation in a short period of time, reaching 6.22 log in 10 min. Both treatments, the peroxone system (O 3/H 2O 2) and catalytic ozonation (O 3/TiO 2), produced a higher inactivation rate of E. coli than ozonation (4.97 log after 10 min). While the combination of ozone with hydrogen peroxide or titanium dioxide thus produces an increase in the inactivation yield of E. coli regarding ozonation, the O 3/TiO 2/H 2O 2 combination did not enhance the inactivation results. The fitting of experimental values to the corresponding equations through non-linear regression techniques was carried out with Microsoft® Excel GInaFiT software. The inactivation results of E. coli did not respond to linear functions, and it was necessary to use mathematical models able to describe certain deviations in the bacterial inactivation processes. In this case, the inactivation results fit with mathematical models based on the hypothesis that the bacteria population is divided into two different subgroups with different degrees of resistance to treatments, for instance biphasic and biphasic with shoulder models. 相似文献
5.
The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish ( Carassius auratus). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al 2O 3.L ?1, 10 μg ZnO.L ?1, 10 μg Al 2O 3.L ?1 plus 10 μg ZnO.L ?1, 100 μg Al 2O 3.L ?1, 100 μg ZnO.L ?1, and 100 μg Al 2O 3.L ?1 plus 100 μg ZnO.L ?1). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus. The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L ?1 of both single ZnO and Al 2O 3 NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L ?1 Al 2O 3 NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al 2O 3 (except for 10 μg Al 2O 3.L ?1), and after 14 days of exposure to ZnO (10 and 100 μg.L ?1) and Al 2O 3 (100 μg.L ?1) . The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus, but when combined, NPs seem to be slightly more toxic than when added alone. 相似文献
6.
Introduction The kinetics of the transformation of ammonia and acid gases into components of PM 2.5 has been examined. The interactions of existing aerosols and meteorology with the transformation mechanism have also been
investigated. The specific objective was to discern the kinetics for the gas-to-particle conversion processes where the reactions
of NH 3 with H 2SO 4, HNO 3, and HCl take place to form (NH 4) 2SO 4, NH 4NO 3, and NH 4Cl, respectively, in PM 2.5. 相似文献
7.
Reductive transformation of 2,4-dichlorophenoxyacetic acid (2,4-D) by nanoscale and microscale Fe 3O 4 was investigated and compared. Disappearance of the parent species and formation of reaction intermediates and products were kinetically analyzed. Results suggest that the transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), chlorophenol (2-CP, 4-CP) and phenol. About 65% of 2,4-D with initial concentration of 50 μ M was transformed within 48 h in the presence of 300 mg L ?1 nanoscale Fe 3O 4, and the reaction rates increased with increasing dosage of nanoscale Fe 3O 4. The decomposition of 2,4-D proceeded rapidly at optimum pH 3.0. Chloride was identified as a reduction product for 2,4-D in the magnetite–water system. Reductive transformation of 2,4-D by microscale Fe 3O 4 was slower than that by nanoscale Fe 3O 4. The reactions apparently followed pseudo-first-order kinetics with respect to the 2,4-D transformation. The degradation rate of 2,4-D decreased with the increase of initial 2,4-D concentration. In addition, anions had a significant adverse impact on the degradation efficiency of 2,4-D. 相似文献
8.
Purpose Denitrification is an important biochemical process in global nitrogen cycle, with a potent greenhouse gas product N 2O. Wastewater irrigation can result in the changes of soil properties and microbial communities of agricultural soils. The
purpose of this study was to examine how the soil denitrification genes responded to different irrigation regimes. 相似文献
9.
Although the nitrous oxide belongs among three of the most contributing greenhouse gases to global warming, it is quite neglected by photocatalytic society. The g-C 3N 4 and WO 3 composites were therefore tested for the photocatalytic decomposition of N 2O for the first time. The pure photocatalysts were prepared by simple calcination of precursors, and the composites were prepared by mixing of suspension of pure components in water followed by calcination. The structural (X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy), textural (N 2 physisorption), and optical properties (diffuse reflectance spectroscopy, photoluminescence spectroscopy, photoelectrochemical measurements) of all composites were correlated with photocatalytic activity. The experimental results and results from characterization techniques confirmed creation of Z-scheme in the WO 3/g-C 3N 4 composites, which was confirmed by hydroxyl radicals’ trapping measurements. The photocatalytic decomposition of N 2O was carried out in the presence of UVA light (peak intensity at 365 nm) and the 1:2 WO 3/g-C 3N 4 composite was the most active one, but the photocatalytic activity was just negligibly higher than that of pure WO 3. This is caused by relatively weak interaction between WO 3 and g-C 3N 4 which was revealed from XPS. 相似文献
10.
Background, aim and scope Photocatalytic oxidation using UV irradiation of TiO 2 has been studied extensively and has many potential industrial applications, including the degradation of recalcitrant contaminants
in water and wastewater treatment. A limiting factor in the oxidation process is the recombination of conduction band electrons
(e
−
cb) with electron holes (h vb+) on the irradiated TiO 2 surface; thus, in aqueous conditions, the presence of an effective electron scavenger will be beneficial to the efficiency
of the oxidation process. Ferrate (FeO 42−) has received much recent attention as a water treatment chemical since it behaves simultaneously as an oxidant and coagulant.
The combination of ferrate [Fe(VI)] with UV/TiO 2 photocatalysis offers an oxidation synergism arising from the Fe(VI) scavenging of e
−
cb and the corresponding beneficial formation of Fe(V) from the Fe(VI) reduction. This paper reviews recent studies concerning
the photocatalytic oxidation of problematic pollutants with and without ferrate. 相似文献
11.
A microscale zero-valent iron (mZVI)-based in situ reactive zone is a promising technology for contaminated groundwater remediation. Estimation of mZVI aging behavior after its injection into the subsurface is essential for efficiency and longevity assessments. In this study, batch tests were conducted to investigate the effect of initial pH on mZVI aging dynamics, as well as the formation and evolution of aging products over 112 days. Results indicated that mZVI aging accelerated with decreasing initial pH. Corrosion rates of mZVI particles under pH 6.0 and 7.5 were approximately two orders of magnitude higher than those observed at pH 9.0. The morphological, structural, and compositional evolution of mZVI particles in three systems (pH = 6.0, 7.5, and 9.0) were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In acidic and neutral solutions, a thick passivation layer with loosely and unevenly distributed aging precipitates was observed, and Fe 3O 4 was the final aging precipitate. Nevertheless, in alkaline solutions, minute aging precipitates were detected on the mZVI surface at 112 day. Characterization results suggested that mZVI was oxidized via the Fe 0–Fe(OH) 2–Fe 3O 4 route. These findings shed new light on mZVI aging mechanisms, particularly its physicochemical characteristics and the structural evolution of mZVI in field-scale groundwater remediation applications. 相似文献
12.
The catalysts such as Fe, Bi 2O 3, and Fe-doped Bi 2O 3 were synthesized for the sonophotocatalytic treatment of synthetic dye and real textile wastewater. The resultant catalysts were characterized for its size and uniform shape using x-ray diffractogram (XRD) and scanning electron microscopy (SEM) which signified the nanorod shape formed Bi 2O 3. The higher ultraviolet light absorbance capacity of the catalysts was also evident using diffuse reflectance spectroscopy (DRS). Initially, the effect of conventional parameters such as initial pH, gas bubbling (argon, oxygen, air and nitrogen) and oxidant addition (H 2O 2 and peroxymonosulfate) in the presence of sonolysis (22 and 37 kHz frequency) and photolysis (UV-C light) on 10 ppm Basic Brown 1 dye was studied. The results showed that highest decolorization of 62 % was attained for 3 g/L peroxymonosulfate under 37 kHz frequency sonolysis treatment. Secondly, with the catalyst study, highest of 46 % dye color removal was obtained with 4 g/L Fe under 37 kHz frequency sonolysis treatment. The sonophotocatalytic treatment of dye with Fe-doped Bi 2O 3 catalyst in combination with peroxymonosulfate showed highest color removal of 99 %. Finally, the sonophotocatalytic treatment of real textile wastewater in the presence of 3 g/L Fe-doped Bi 2O 3 and 6 g/L peroxymonosulfate reduced the total organic carbon (TOC) and chemical oxygen demand (COD) level to 77 and 91 %, respectively, in 180 min. The reported treatment process was found to treat the synthetic dye and real textile wastewater effectively. 相似文献
13.
Introduction The concentrations of trace metals, ionic species, and carbonaceous components in PM 10 (particulate matter with aerodynamic diameters smaller than 10 μm) were measured from samples collected near an industrial
complex, primarily composed of cement plants, in southeastern Spain, from September 2005 to August 2006. 相似文献
14.
Increased use of fullerols in various fields and expected increase of their environmental spread impose the necessity for testing fullerol nanoparticles (FNP) effects on microbiota. There is little information available on the interaction of mycotoxigenic fungi and FNP, despite FNP having a great potential of modifying mycotoxin production. Namely, FNP exhibit both ROS-quenching and ROS-producing properties, while oxidative stress stimulates mycotoxin synthesis in the fungi. In order to shed some light on the extent of interaction between FNP and mycotoxigenic fungi, the effects of fullerol C 60(OH) 24 nanoparticles (10, 100, 1000 ng/mL) on mycelial growth, aflatoxin production and oxidative stress modulation in an aflatoxigenic strain of Aspergillus flavus (NRRL 3251) during 168 h of incubation in a liquid culture medium were examined. FNP slightly reduced mycelial biomass weight, but significantly decreased aflatoxin concentration in media. Lipid peroxide content, superoxide dismutase, catalase and glutathione peroxidase activities suggest that FNP treatments hormetically reduced oxidative stress within fungal cells in turn suppressing aflatoxin production. These findings contribute to the assessment of environmental risk and application potential of fullerols. 相似文献
15.
Introduction Magnetic Fe 3O 4 nanoparticles were prepared by coprecipitation and then were coated with SiO 2 on the surface. Materials and methods Fe 3O 4@SiO 2 composite microspheres were modified by KH570. Using molecular imprinting technology, atrazine magnetic molecularly imprinted polymer was prepared by using atrazine as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linkers. The morphology, composition and magnetic properties of magnetic nanoparticles were characterized. The recognition selectivity of polymer was studied for template molecule and simulation by UV spectrophotometry. The adsorption properties and selectivity ability were analyzed by Scatchard analysis. Results Scatchard linear regression analysis indicated that there are two binding sites of the target molecules. The magnetic molecularly imprinted polymer has been applied to the analysis of atrazine in real samples. Conclusion The results show that: the recovery rates and the relative standard deviation were 94.0??98.7% and 2.1??4.0% in corn, the recovery rates and the relative standard deviation were 88.7??93.5% and 2.8??7.2% in water. 相似文献
16.
Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH 4) and nitrous oxide (N 2O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH 4 fluxes at the expense of increasing the N 2O fluxes. Furthermore, fertilization significantly decreased the CH 4 fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH 4 fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N 2O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH 4 emissions from the OF were 100 % lower, and N 2O emissions were 421 % higher than those from the PF. Although cumulative N 2O emissions were stimulated in the newly converted orchard, the strong reduction of CH 4 led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH 4 +-N) and nitrate (NO 3 ?-N) contents indicated a significant variation in soil properties and contributed to variations in soil CH 4 and N 2O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH 4 and N 2O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH 4 and N 2O emissions. 相似文献
17.
Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe 0, Fe/Ni, Fe 3O 4, Fe 3???x Ni x O 4). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (H 2O 2 or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (Fe 3O 4) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe 0 and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe 0 and Fe/Ni (18–19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250–500 and <500 μm), no PCB degradation was observed in the finest fraction (≤250 μm) having higher organic matter content. These findings may have important practical implications to promote successively reduction and oxidation reactions in soils and understand the impact of soil properties on remediation performance. 相似文献
18.
We demonstrated a method to form magnetic antimicrobial POHABA (poly-N,N′-[(4,5-dihydroxy-1,2-phenylene)bis(methylene)]bisacrylamide)-based core-shell nanostructure by free-radical polymerization of OHABA on the Fe3O4 core surface. The magnetic antimicrobial agent Fe3O4@POHABA can be used in domestic water treatment against bacterial pathogens. The thickness of POHABA shell could be controlled from 10.4 ± 1.2 to 56.3 ± 11.7 nm by the dosage of OHABA. The results of antimicrobial-activity test indicated that POHABA-based core-shell nanostructure had broad-spectrum inhibitory against Gram-negative, Gram-positive bacteria and fungi. The minimum inhibitory concentration (MIC) values of Fe3O4@POHABA nanostructure against Escherichia coli and Bacillus subtilis were both 0.4 mg/mL. Fe3O4@POHABA nanostructures responded to a permanent magnet and were easily recycled. Fe3O4@POHABA nanoparticles retained 100% antimicrobial efficiency for both Gram-negative and Gram-positive bacteria throughout eight recycle procedures. 相似文献
19.
Introduction It is predicted that demand for electricity in Islamic Republic of Iran will continue to increase dramatically in the future
due to the rapid pace of economic development leading to construction of new power plants. At the present time, most of electricity
is generated by burning fossil fuels which result in emission of great deal of pollutants and greenhouse gases (GHG) such
as SO 2, NO x, and CO 2. The power industry is the largest contributor to these emissions. Due to minimal emission of GHG by renewable and nuclear
power plants, they are most suitable replacements for the fossil-fueled power plants. However, the nuclear power plants are
more suitable than renewable power plants in providing baseload electricity. The Bushehr Nuclear Power Plant, the only nuclear
power plant of Iran, is expected to start operation in 2010. This paper attempts to interpret the role of Bushehr nuclear
power plant (BNPP) in CO 2 emission trend of power plant sector in Iran. 相似文献
20.
Considerable researches have documented the negative effects of ozone on woody species in North America and Europe; however, little is known about how woody tree species respond to elevated O 3 in subtropical China, and most of the previous studies were conducted using pot experiment. In the present study, Machilus ichangensis Rehd. et Wils ( M. ichangensis) and Taxus chinensis (Pilger) Rehd. ( T. chinensis), evergreen tree species in subtropical China, were exposed to non-filtered air (NF), 100 nmol mol ?1 O 3 (E1) and 150 nmol mol ?1 O 3 (E2), in open-top chambers under field conditions from 21st March to 2nd November 2015. In this study, O 3 fumigation significantly reduced net photosynthesis rate (Pn) in M. ichangensis in the three measurements and in T. chinensis in the last measurement. Also, non-stomatal factors should be primarily responsible for the decreased Pn. O 3 fumigation-induced increase in malondialdehyde, superoxide dismutase, and reduced ascorbic acid levels indicated that antioxidant defense mechanism had been stimulated to prevent O 3 stress and repair the oxidative damage. Yet, the increase of antioxidant ability was not enough to counteract the harm of O 3 fumigation. Because of the decrease in CO 2 assimilation, the growth of the two tree species was restrained ultimately. The sensitivity of the two tree species to O 3 can be determined: M. ichangensis > T. chinensis. It suggests a close link between the rising O 3 concentrations and the health risk of some tree species in subtropics in the near future. 相似文献
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