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1.
Aqueous 4-nitrophenol solutions containing TiO2 or Al2O3 nanoparticles were irradiated with electron beam. 4-nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO2 or Al2O3 (2 g l−1) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO2 or Al2O3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO2 or Al2O3 during irradiation is just due to adsorption. 相似文献
2.
Effects of Fe2O3, organic matter and carbonate on photocatalytic degradation of lindane in the sediment from the Liao River,China 总被引:1,自引:0,他引:1
Fourteen sediment samples with different content of Fe2O3 were collected from the lower reaches of the Liao River in China. The photodegradation of lindane on the surfaces of these sediments was investigated to observe the effects of Fe2O3 and other photoinducable substances, such as TiO2 and organic substances, on photodegradation of lindane. A partial least-squares (PLS) analysis model was developed to find out the statistical relationship between the photodegradation and the contents of these photoinducable substances. It was concluded from the PLS analysis that inorganic carbon and organic carbon have negative effects, whereas Fe2O3 and TiO2 accelerate the photodegradation of lindane in the sediment samples when 365 nm UV light was used as light source. In all cases of the experiments, the photodegradation of lindane in the sediment samples were fitted for pseudo-first-order kinetics. 相似文献
3.
UV/TiO2/H2O2, UV/TiO2 and UV/H2O2 were compared as pre-treatment processes for the detoxification of mixtures of 4-chlorophenol (4CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP) and pentachlorophenol (PCP) prior to their biological treatment. When each chlorophenol was initially supplied at 50 mg l−1, UV/TiO2/H2O2 treatment supported the highest pollutant removal, COD removal, and dechlorination efficiencies followed by UV/TiO2 and UV/H2O2. The remaining toxicity to Lipedium sativum was similar after all pre-treatments. Chlorophenol photodegradation was always well described by a first order model kinetic (r2 > 0.94) and the shortest 4CP, DCP, TCP and PCP half-lives of 8.7, 7.1, 4.5 and 3.3 h, respectively, were achieved during UV/TiO2/H2O2 treatment. No pollutant removal was observed in the controls conducted with H2O2 or TiO2 only. Inoculation of all the photochemically pre-treated mixtures with activated sludge microflora was followed by complete removal of the remaining pollutants. Combined UV/TiO2/H2O2-biological supported the highest detoxification, dechlorination (99%) and COD removal (88%) efficiencies. Similar results were achieved when each chlorophenol was supplied at 100 mg l−1. COD and Cl mass balances indicated UV, UV/H2O2, and UV/TiO2 treatments lead to the formation of recalcitrant photoproducts, some of which were chlorinated. 相似文献
4.
A combined plasma photolysis (CPP) method for removal of CS2 from gas streams at atmospheric pressure 总被引:1,自引:0,他引:1
A combined plasma photolysis (CPP) reactor that utilizes a dielectric barrier discharge (DBD) plasma and 207 nm UV radiation from discharge-driven KrBr* excimers was designed and constructed. Gas streams containing CS2 were treated with stand-alone DBD and CPP at atmospheric pressure. In comparison to DBD, CPP greatly enhanced the removal efficiency at the same applied voltage, waste gas concentration and gas residence time. Thus the applied voltage could be reduced to a certain extent in the plasma processing of industrial wastes. Influences of the KrBr* radiation, inlet CS2 concentration and gas residence time on CS2 removal by CPP were also studied. In addition, the likely reaction mechanisms for the removal of CS2 by CPP are suggested based on the byproducts analysis. The enhanced removal efficiency and reaction mechanisms implied that the CPP process would probably be suitable for the removal of a large number of gaseous pollutants. 相似文献
5.
A new glass–ceramic was synthesized by crystal growth from a homogenous glass obtained by melting a mixture of fly ash collected from a power plant in Hebei province of China, titanium slag collected from a titanium factory in Sichuan province of China, and MgCO3 as an additive. According to the measurement results of differential thermal analysis, a thermal treatment of nucleating at 850 °C for 2 h and crystallizing at 985 °C for 1.5 h was used to obtain the crystallized glass. X-ray diffraction and scanning electron microscopy measurements showed that the main crystalline phase of this material was iron-ion substituted cordierite, (Mg,Fe)2Al4Si5O18, which is homogeneously dispersed within the parent glass matrix. The infrared radiance and thermal expansion coefficient of this material have been examined, and the results demonstrate that this glass–ceramic material has potential for application in a wide range of infrared heating and drying materials. 相似文献
6.
Comparative studies of the Fe3+/2+-UV, H2O2-UV, TiO2-UV/vis systems for the decolorization of a textile dye X-3B in water 总被引:4,自引:0,他引:4
Xu Y 《Chemosphere》2001,43(8):1103-1107
The degradation of a common textile dye, Reactive-brilliant red X-3B, by several advanced oxidation technologies was studied in an air-saturated aqueous solution. The dye was resistant to the UV illumination (wavelength λ 320 nm), but was decolorized when one of Fe3+, H2O2 and TiO2 components was present. The decolorization rate was observed to be quite different for each system, and the relative order evaluated under comparable conditions followed the order of Fe2+–H2O2–UV Fe2+–H2O2 > Fe3+–H2O2–UV > Fe3+–H2O2 > Fe3+–TiO2–UV > TiO2–UV > Fe3+–UV > TiO2–visible light (λ 450 nm) > H2O2–UV > Fe2+–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity. 相似文献
7.
An experiment was carried out to decompose chlorinated dioxins (PCDDs, PCDFs) Chlorobenzenes, NOx and odourous compounds (H2S, CH4S, C2H6S2, C8H8, C2H6S, C2H4O, NH3) simultaneously using a catalyst in the MSW incineration plant. The experiments were conducted at temperatures from 200°C to 400°C and from 3000h−1 to 6000h−1 at space velocity. A catalyst containing V2O5 and WO3 on the basis of TiO2 is used, an oxidizing catalyst of the honeycomb type. The average decomposition efficiencis were 95%, 98%, 92% for PCDDs(48CDDs), PCDFs(48CDFs) and Chlorobenzenes(36CLBs) at a reaction temperature of 350°C and a space velocity of 3000h−1, more than 90% for NOx at a reactiont temperature of 300°C and more than 80% for odourous compounds at the reaction temperature of 300°C and a space velocity of 6000h−1. All those compounds were decomposed successfully with increasing contact time and surface. The rate-determing step was the chemical reaction of catalyst surface. 相似文献
8.
Equilibrium sorption of phenanthrene by soil humic acids 总被引:1,自引:0,他引:1
This study investigated the effect of chemical heterogeneity of humic acids (HAs) on the equilibrium sorption of phenanthrene by HA extracts. Six HA samples were extracted from three different soils with 0.5 M NaOH and 0.1 M Na4P2O7 and were characterized with elemental analysis, infrared spectrometry, and solid-state 13C nuclear magnetic resonance (NMR) spectrometry. The equilibrium sorption measurements were carried out with a batch technique and using the six HA solids as the sorbents and phenanthrene as the sorbate. The measured sorption isotherm data were fitted to the Freundlich equation. The results showed that, for the same soil, (i) the total HA mass extracted with Na4P2O7 was 13.7–22.6% less than that extracted with NaOH, (ii) the Na4P2O7-extracted HA had higher O/C atomic ratio, greater content of polar organic carbons (POC), and lower aliphatic carbon content than the NaOH-extracted HA, and (iii) the Na4P2O7-extracted HA exhibited greater sorption isotherm linearity and but not dramatic difference in sorption capacities than the NaOH extracted HA. The differences in the HA properties resulting from the two different extraction methods may be because NaOH can hydrolyze insoluble HA fractions such as fatty acid like macromolecules bound on soils whereas Na4P2O7 could not. As a result, the HAs extracted with the two different methods had different polarity and functionality which affected their sorption property for phenanthrene. 相似文献
9.
The presence of disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water is of great concern due to their adverse effects on human health. Emerging regulation limiting the concentration of DBPs in drinking water has increased demands for technologies and processes which reduce the formation of DBPs in drinking water. In this study, UV-H2O2 based advance oxidation process (AOP) was used to treat raw surface water. Experiments were conducted using low pressure mercury vapor UV lamps in collimated beam and flow-through annular photoreactors. The effect of UV fluence (0–3500 mJ cm−2) and hydrogen peroxide concentration (0–23 mg l−1) in reducing the concentration of THMs and HAAs was examined. The UV-H2O2 AOP was then coupled with a downstream biological activated carbon (BAC) treatment to assess the synergetic benefits of combining the two treatments. It was observed that UV-H2O2 AOP was only effective at reducing DBPs at UV fluences of more than 1000 mJ cm−2and initial H2O2 concentrations of about or greater than 23 mg l−1. However, the combined AOP–BAC treatment showed significant reductions of 43%, 52%, and 59% relative to untreated raw water for DBPs, TOC, and UV254, respectively. 相似文献
10.
Pâivi Ruokojârvi Arja Asikainen Juhani Ruuskanen Kari Tuppurainen Christian Mueller Pia Kilpinen Niina Yli-Keturi 《Journal of the Air & Waste Management Association (1995)》2013,63(3):422-431
ABSTRACT Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from municipal waste incineration have been widely studied because of their extensive toxicity, and many efforts have been made to restrict their emissions. Although a number of chemical compounds have been shown in laboratory-scale tests to inhibit the formation of PCDD/Fs, few have been tested in pilot- or full-scale plants. This work evaluates the effect of urea as a PCDD/F inhibitor in a pilot-scale incinerator that uses refuse-derived fuel (RDF). The decomposition of urea under the test conditions was also studied using detailed kinetic modeling. An aqueous solution of urea was injected into the flue gas stream after the furnace at ~730 °C, with varied urea concentrations and flue gas residence times used between the furnace and the sampling point. The results demonstrate that urea can successfully inhibit PCDD/F formation in waste incineration if concentrations and injection points are properly adjusted. The kinetic model showed that urea can be rapidly decomposed under appropriate flue gas conditions, indicating that in addition to the urea molecule itself, decomposition products of urea can also be responsible for the reduction of PCDD/F production during incineration. 相似文献
11.
Cold season (winter and thaw) CH4, CO2 and N2O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH4 and CO2 fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m−2 h−1, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m−2 h−1, respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH4 fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N2O sink in winter season in northeast China. During thaw, the CH4 and CO2 emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N2O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange. 相似文献
12.
A fungal vapor-phase bioreactor for the removal of nitric oxide from waste gas streams. 总被引:5,自引:0,他引:5
J R Woertz K A Kinney P J Szaniszlo 《Journal of the Air & Waste Management Association (1995)》2001,51(6):895-902
Ground-level O3 formation is becoming a major concern in many cities due to recent tightening of O3 regulations. To control O3 formation, more efficient treatment processes for O3 precursors, such as NOx and volatile organic compounds (VOCs), are needed. One promising new technology for removing both NOx and VOCs from off-gas streams is biofiltration, a simple process whereby contaminated air is passed through a biologically active packed bed. In this study, a toluene-degrading fungal bioreactor was used to treat an aerobic gas stream contaminated with NO. The fungal bioreactor removed 93% of the inlet 250-ppmv NO at an empty bed contact time (EBCT) of 1 min when supplied with 90 g/m3/hr toluene. The presence of NH4+ concentrations greater than 0.4 mg NH3/g dry packing medium, however, resulted in poor NO removal. The bioreactor achieved a maximum toluene elimination capacity of 270 g/m3/hr and maintained greater than 95% toluene removal efficiencies over the 175-day study period. 相似文献
13.
14.
Evaluation of PCDD/F congener distributions in MWI flue gas treated with SCR catalysts 总被引:1,自引:0,他引:1
Partitioning of PCDD/F congeners between gaseous and particulate phases and removal efficiencies of the air pollution control devices (APCDs) for PCDD/Fs at an existing municipal waste incinerator (MWI) in Taiwan are evaluated via stack sampling and analysis. The MWI investigated is equipped with electrostatic precipitators (EP), wet scrubbers (WS) and selective catalytic reduction system (SCR) as APCDs. The average PCDD/F concentration of stack gas is 1.49 ng/N m3, and the International Toxic Equivalent Quantity (I-TEQ) is 0.043 ng-I-TEQ/N m3. The EP increases PCDD/F concentration by 174.0% while the average removal efficiency of WS + SCR system for PCDD/Fs reaches 99.1%. In addition, the PCDF removal efficiency achieved with WS + SCR system (97.1–99.8%) is higher than that for PCDDs (96.5–99.3%). The results obtained on gas/particulate partitioning in flue gas indicate that the particulate-phase PCDD/Fs accounted for 65% at the inlet of EP, 20% at the outlet of EP and 50% at the stack, respectively, of the total PCDD/F concentrations. This study also indicates that as the chlorination level of PCDD/F congeners increases, the percentage of PCDD/Fs existing in gas phase decreases in all flue gas samples. 相似文献
15.
Urea as a PCDD/F inhibitor in municipal waste incineration 总被引:2,自引:0,他引:2
Ruokojärvi P Asikainen A Ruuskanen J Tuppurainen K Mueller C Kilpinen P Yli-Keturi N 《Journal of the Air & Waste Management Association (1995)》2001,51(3):422-431
Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from municipal waste incineration have been widely studied because of their extensive toxicity, and many efforts have been made to restrict their emissions. Although a number of chemical compounds have been shown in laboratory-scale tests to inhibit the formation of PCDD/Fs, few have been tested in pilot- or full-scale plants. This work evaluates the effect of urea as a PCDD/F inhibitor in a pilot-scale incinerator that uses refuse-derived fuel (RDF). The decomposition of urea under the test conditions was also studied using detailed kinetic modeling. An aqueous solution of urea was injected into the flue gas stream after the furnace at approximately 730 degrees C, with varied urea concentrations and flue gas residence times used between the furnace and the sampling point. The results demonstrate that urea can successfully inhibit PCDD/F formation in waste incineration if concentrations and injection points are properly adjusted. The kinetic model showed that urea can be rapidly decomposed under appropriate flue gas conditions, indicating that in addition to the urea molecule itself, decomposition products of urea can also be responsible for the reduction of PCDD/F production during incineration. 相似文献
16.
Lanthanum-doped anatase TiO2 thin films on glass prepared via a sol–gel process have been shown to have much higher photocatalytic activity for the degradation of gaseous benzene than pure anatase TiO2 thin film. The photodecomposition of benzene on both types of TiO2 films follows the first-order kinetics while the CO2 and CO formation followed the zero-order kinetics. GC/MS identification of the intermediates produced during the photodegradation of benzene revealed that doping lanthanum into TiO2 thin film favors a cleavage of benzene ring. An optimal lanthanum amount with respect to photocatalytic activity was about 2.5 wt% (La2O3/TiO2). 相似文献
17.
The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO2 photocatalyst. Aqueous suspensions of the microorganisms (107–108 cfu ml−1) and POM (or TiO2) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO2-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H3PW12O40, H3PMo12O40, and H4SiW12O40) tested in this study, the inactivation of E. coli was fastest with H4SiW12O40 while that of B. subtilis was the most efficient with H3PW12O40. Although the biocidal action of TiO2 photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO2-PCI. While TiO2 caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO2-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology. 相似文献
18.
Comparative study of the oxidation of atrazine and acetone by H2O2/UV, Fe(III)/UV, Fe(iii)/H2O2/UV and Fe(II) or Fe(III)/H2O2 总被引:1,自引:0,他引:1
In this study, the rates of degradation of organic compounds by several AOPs (H2O2/UV, Fe(III)/UV, Fe(III)/H2O2/UV, Fe(II)/H2O2 and Fe(III)/H2O2) have been compared. Experiments were carried out at pH ≈ 3 (perchloric acid / sodium perchlorate solutions) and with UV reactors equipped with a low-pressure mercury vapour lamp (emission at 253.7 run). The data obtained with atrazine ([Atrazine]o = 100 μg/L) showed that the rate of degradation of atrazine in very dilute aqueous solution is much more rapid with Fe(III)/UV than with H2O2/UV. Photo-Fenton process (Fe(III)/H2O2/UV) was found to be more efficient than H2O2/UV and Fe(II)/H2O2 for the mineralization of acetone ([Acetone]o = 1 mM). 相似文献
19.
Biological elimination of H2S and NH3 from wastegases by biofilter packed with immobilized heterotrophic bacteria 总被引:10,自引:0,他引:10
Biotreatment of various ratios of H2S and NH3 gas mixtures was studied using the biofilters, packed with co-immobilized cells (Arthrobacter oxydans CH8 for NH3 and Pseudomonas putida CH11 for H2S). Extensive tests to determine removal characteristics, removal efficiency, removal kinetics, and pressure drops of the biofilters were performed. To estimate the largest allowable inlet concentration, a prediction model was also employed. Greater than 95% and 90% removal efficiencies were observed for NH3 and H2S, respectively, irrespective of the ratios of H2S and NH3 gas mixtures. The results showed that H2S removal of the biofilter was significantly affected by high inlet concentrations of H2S and NH3. As high H2S concentration was an inhibitory substrate for the growth of heterotrophic sulfur-oxidizing bacteria, the activity of H2S oxidation was thus inhibited. In the case of high NH3 concentration, the poor H2S removal efficiency might be attributed to the acidification of the biofilter. The phenomenon was caused by acidic metabolite accumulation of NH3. Through kinetic analysis, the presence of NH3 did not hinder the NH3 removal, but a high H2S concentration would result in low removal efficiency. Conversely, H2S of adequate concentrations would favor the removal of incoming NH3. The results also indicated that maximum inlet concentrations (model-estimated) agreed well with the experimental values for space velocities of 50–150 h−1. Hence, the results would be used as the guideline for the design and operation of biofilters. 相似文献
20.
Kinetics of nitromusk compounds degradation in water by ultraviolet radiation and hydrogen peroxide 总被引:2,自引:0,他引:2
The photodegradation of five representative nitromusk compounds in water has been performed in a stirred batch photoreactor with a UV low-pressure immersed mercury lamp, at constant temperature and different doses of hydrogen peroxide. The rate constants have been calculated on the basis of experimental data and a postulated first-order kinetic model. The rate constants, at 298 K and a dose of 1.1746 μmol l−1 H2O2 ranges from 0.3567 × 10−3 s−1 for musk tibetene, to 1.785 × 10−3 s−1 for musk ambrette. 相似文献