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1.
The synthesis of TiO 2 and Fe–TiO 2 by sol–gel method is demonstrated and characterized. The characterization of TiO 2 and Fe–TiO 2 is performed with instruments, including TGA/DTA, FTIR, UV–Vis, N 2 adsorption and SEM. Dichloromethane is used for the photocatalytic activity test. From the results of dichloromethane photocatalyitc degradation, the calcined temperature of TiO 2 and the presence of water vapor influence the photocatalytic activity. The optimum doping amount of iron ions is 0.005 mol%, and this can enhance the photocatalytic activity, while too great an amount will make the iron ions become recombination centers for the electron–hole pairs and reduce the photocatalytic activity. UV–Vis diffuse reflectance spectra of Fe–TiO 2 show an increase in absorbency in the visible light region with the increase in iron ions doping concentration The intermediate of dichloromethane photodegradation includes CHCl 3, CCl 4, CH 2Cl 2 and COCl 2. The presence of iron ions may reduce the adsorption of Cl element on the surface of the photocatalyst. 相似文献
2.
TiO 2 powder-containing paper composites, called TiO 2 paper, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO 2 paper has a porous structure originating from the layered pulp fiber network, with TiO 2 powders scattered on the fiber matrix. Under UV irradiation, the TiO 2 paper decomposed gaseous acetaldehyde more effectively than powdery TiO 2 and a pulp/TiO 2 mixture not in paper form. Scanning electron microscopy and mercury intrusion analysis revealed that the TiO 2 paper had characteristic unique voids ca. 10 μm in diameter, which might have contributed to the improved photocatalytic performance. TiO 2 paper composites having different void structures were prepared by using beaten pulp fibers with different degrees of freeness and/or ceramic fibers. The photodecomposition efficiency was affected by the void structure of the photocatalyst paper, and the initial degradation rate of acetaldehyde increased with an increase in the total pore volume of TiO 2 paper. The paper voids presumably provided suitable conditions for TiO 2 catalysis, resulting in higher photocatalytic performance by TiO 2 paper than by TiO 2 powder and a pulp/TiO 2 mixture not in paper form. 相似文献
3.
Fe-doped TiO 2 was prepared by the calcination of Fe xTiS 2 ( x = 0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectra. All the Fe-doped TiO 2 were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO 2 for the degradation of phenol was investigated by varying the iron content during UV (365 nm) and visible light (405 nm and 436 nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO 2 was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron–hole trap by the doped Fe 3+ and their charge recombination on the doped Fe 3+ level. The Fe-doped TiO 2 ( x = 0.005) was more active than P25 TiO 2 under solar light irradiation. The suspended Fe-doped TiO 2 spontaneously precipitated once the stirring of the reaction mixture was terminated. 相似文献
4.
The temporal variability and bioaccumulation dynamics of C 12–25 n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C 12–25 (165 ± 93, 70 ± 48 or 280 ± 134 μg g −1, dry, fresh and lipid weight, respectively) and UCM (931 ± 560, 399 ± 288 and 1567 ± 802 μg g −1) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001–2002 during the rainiest period over the last four decades (1750 vs. 1083 ± 4.6 mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C 15–17 and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001–2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4–6.4 dry weight or 0.07–0.94 lipid-organic carbon) plotted against Kow showed a parabolic pattern maximizing at n-C 14–18 and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log Kow: 7.2–9.9), intermediate-size C 14–18 n-alkanes and C 15–20 isoprenoids (MW: 198–282; length: 17.9 to 25.4 Å) with melting points ranging from −19.8 to 28 °C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C 25 to above 90% for n-C 14–15 and isoprenoids. 相似文献
5.
Lanthanum-doped anatase TiO 2 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 TiO 2 thin film. The photodecomposition of benzene on both types of TiO 2 films follows the first-order kinetics while the CO 2 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 TiO 2 thin film favors a cleavage of benzene ring. An optimal lanthanum amount with respect to photocatalytic activity was about 2.5 wt% (La 2O 3/TiO 2). 相似文献
6.
The plasma–chemical degradation of Forafac 1110, a perfluorinated non-ionic surfactant, in aqueous solutions was investigated using TiO 2 catalysts. The considered plasma was the gliding arc in humid air, which results from an electric discharge at atmospheric pressure and quasi-ambient temperature. Two titanium dioxide powders were used and their synergistic effects on the Forafac degradation were compared. The results were discussed through the evolution of the pH, the conductivity, the fluoride ions concentration released in solutions, the surfactant concentration remaining after treatment and the chemical oxygen demand (COD) measurement. The combination of the plasma–chemical treatment with heterogeneous catalysis through the use of TiO2 accelerated the Forafac degradation, since only 60 min was sufficient to remove 96% instead of 360 min needed in the absence of TiO2. The use of anatase and rutile under the trade-name of Rhodia TiO2 and Merck TiO2, respectively, led to different results, because Rhodia TiO2 has proven to be more efficient. It would seem that the crystalline phase as well as the crystallite size, explain the efficiency of anatase. The advantage of the plasma-catalysis is due to the fact that there is a significant production of the OH• radicals not only generated by the gliding arc discharge but also by TiO2. 相似文献
7.
Adsorption isotherms of Direct Red 80 (DR80) and Acid Blue 25 (AB25) on the egg shell membrane (ESM) were performed at 20 ± 1 °C. Physical characteristics of ESM such as surface area and presence of functional groups were verified. The Fourier transform infra-red (FTIR) spectra proved the presence of fuctional groups such as hydroxyl, amine and carbonyl groups in ESM. The surface area of ESM was found to be 2.2098 m 2/g. The effects of operational parameters such as initial dye concentration, pH 0, contact time, particle size and ESM doses were studied. The Langmuir, Freundlich, BET, Redlich-Peterson and Temkin adsorption models were applied to describe the equilibrium isotherms. The pseudo-first-order and pseudo-second-order kinetics models were examined to evaluate the kinetics data at different pH 0 values (2–12) and the rate constants were calculated. Maximum desorption of 81.8% was achieved for both dyes in aqueous solution at pH 0 12. Also scanning electron micrographs (SEM) of the treated and untreated adsorbent were performed. Results indicate that ESM could be employed as a natural and Eco-Friendly adsorbent material for the removal of trace organics in solutions. 相似文献
8.
The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO 2 suspension under UV illumination has been investigated using oxygen (O 2) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O 2 for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO 2–UV–O 2 system, while in contrast phthalic acid was found to be the main intermediate product in the TiO 2–UV–Fe(VI) system. These findings indicate that DMP degradation in the TiO 2–UV–O 2 and TiO 2–UV–Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO 2–UV–O 2 reaction system and an unknown radical species (most likely an iron–oxo species) is suspected to exist in the TiO 2–UV–Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO 2–UV–O 2 and TiO 2–UV–Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO 2–UV–O 2 reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO 2–UV–Fe(VI) reaction systems attack the alkyl chain of DMP. 相似文献
9.
An experiment was carried out to decompose chlorinated dioxins (PCDDs, PCDFs) Chlorobenzenes, NOx and odourous compounds (H 2S, CH 4S, C 2H 6S 2, C 8H 8, C 2H 6S, C 2H 4O, NH 3) 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 V 2O 5 and WO 3 on the basis of TiO 2 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
10.
This study examines the oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS 2, H 2S, DMDS, and CH 3SH) to a further oxidized form (e.g., SO 2, MSA, and H 2SO 4) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6° N, 127° E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H 2S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO 2 was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO 2 during the measurement period. The SO 2 production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NO x levels during the experimental conditions. 相似文献
11.
Biogeochemical distinction of methane emissions to the atmosphere may essentially rely on the surface area and morphometry of Amazon hydroreservoirs. Tucuruí (deep) and Samuel (shallow) reservoirs released in average 13.82 ± 22.94 and 71.19 ± 107.4 mg CH 4 m −2 d −1, respectively. δ 13C–CH 4 values from the sediments to the atmosphere indicate that the deep reservoir has extended methanotrophic layer, oxidizing large quantities of light isotope methane coming from the sediments, while sediment-generated methane can easily evade the shallow reservoir. 相似文献
12.
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 Fe 3+, H 2O 2 and TiO 2 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 Fe 2+–H 2O 2–UV Fe 2+–H 2O 2 > Fe 3+–H 2O 2–UV > Fe 3+–H 2O 2 > Fe 3+–TiO 2–UV > TiO 2–UV > Fe 3+–UV > TiO 2–visible light ( λ 450 nm) > H 2O 2–UV > Fe 2+–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity. 相似文献
13.
ZnO powders with different morphologies were synthesized by alkali precipitation, organo-zinc hydrolysis, and spray pyrolysis. Acetaldehyde decomposition was used as a probe reaction to evaluate the photocatalysis of these ZnO powders. We investigated the relationship between photocatalytic activity and crystallinity, surface area, or morphology. Results indicate that the photocatalytic activity of ZnO powder depends on crystallinity rather than surface area for the same original ZnO powders prepared by equal conditions other than the difference in calcination temperature. However, no direct relationship between photocatalytic activity and crystallinity or surface area was found for the differently original ZnO powders prepared by different methods, or the same method with different conditions. Instead, we find that the particle morphology significantly affects its photocatalysis. 相似文献
14.
The present work focuses on the fate of two cancerostatic platinum compounds (CPC), cisplatin and carboplatin, as well as of two inorganic platinum compounds, [PtCl 4] 2− and [PtCl 6] 2− in biological wastewater treatment. Laboratory experiments modelling adsorption of these compounds onto activated sludge showed promising specific adsorption coefficients KD and KOC and Freundlich adsorption isotherms. However, the adsorption properties of the investigated substances were differing significantly. Adsorption decreased following the order cisplatin > [PtCl 6] 2− > [PtCl 4] 2− > carboplatin. Log KD-values were ranging from 2.5 to 4.3 , log KOC from 3.0 to 4.7. A pilot membrane bioreactor system (MBR) was installed in a hospital in Vienna and fed with wastewater from the oncologic in-patient treatment ward to investigate CPC-adsorption in a sewage treatment plant. During three monitoring periods Pt-concentrations were measured in the influent (3–250 μg l−1 Pt) and the effluent (2–150 μg l−1 Pt) of the treatment plant using ICP-MS. The monitoring periods (duration 30 d) revealed elimination efficiencies between 51% and 63% based on averaged weekly input–output budgets. The derived log KD-values and log KOC-values ranged from 2.4 to 4.8 and from 2.8 to 5.3, respectively. Species analysis using HPLC-ICP-MS proofed that mainly carboplatin was present as intact drug in the influent and – due to low log KD – in the effluent of the MBR. 相似文献
15.
A simple, rapid and sensitive GC–MS method for the determination of dithiocarbamate fungicide propineb [polymeric zinc propylenebis (dithiocarbamate)] and an improved HPLC procedure for the simultaneous determination of its main metabolite, propylenethiourea, and ethylenethiourea, the main metabolite of all ethylenedithiocarbamates, in airborne samples are described. The method for the analysis of propineb involves the evolution of carbon disulfide (CS 2), under acidic conditions in the presence of stannous chloride, extraction of the generated CS 2 into a layer of isooctane which is then analyzed for CS 2 content by GC–MS in SIM mode. Under the optimum conditions, the retention time of CS 2 was 1.89 min and the total time of chromatographic analysis was 5 min. Recoveries from spiking glass microfibre filters (GF/A) and silica gel filters were 86 ± 7 ( n = 9) and 89 ± 4 ( n = 9), respectively. The limit of detection is 0.7 ng per filter, which is equivalent to about 0.8–1.0 ng m −3 in air. In parallel, an HPLC method with ultraviolet detection is presented for the simultaneous analysis of the metabolites. Separation of the two metabolites was attained in less than 5 min. Recoveries from spiking GF/A and silica gel filters for ethylenethiourea were 100 ± 1 ( n = 3) and 98 ± 2 ( n = 3), respectively, while for propylenethiourea were 102 ± 1 ( n = 3) and 98 ± 1 ( n = 3), respectively. The detection limits are about 36–43 and 40–49 ng m −3 in air for ethylenethiourea and propylenethiourea, respectively. All the analytes spiked in the filters are proven to be stable for more than one month, at −4 °C. 相似文献
16.
A modified domestic microwave oven was applied to heat a magnetite (Fe 3O 4) fixed-bed for continuous decomposition of volatile organic compounds (VOCs), such as acetone, n-hexane, and dichloromethane (DCM), in a simulated flue gas which contains VOCs equivalent to 2000 ppmv as DCM. Experimental results revealed that effect of the addition of water to the inlet stream on decomposition of DCM in the overall experiment was insignificant. Bulk temperature of the Fe 3O 4 fixed-bed was also found to reach 600 °C from an initial room temperature by 6.5 min under microwave radiation, even though the inlet gas was at a high gas hourly space velocity of 5240 h −1 and a high relative humidity of 75%. Moreover, the VOCs in the inlet stream could be decomposed completely over the Fe 3O 4 fixed-bed by microwave heating at a power level of 645 W at heating time of 10 min. The conversion of VOCs is stable when the Fe 3O 4 fixed-bed has been heated longer than 10 min with microwave radiation. The microwave-induced heating upon Fe 3O 4 fixed-bed processing appears to be not only an energy efficient technique for air pollutions treatment but also a promising technology for variety of VOCs in a flue gas from industrial factory being decomposed simultaneously and completely. 相似文献
17.
The electrochemical performance of pure Ti–Pt/β-PbO 2 electrodes, or doped with Fe and F (together or separately), in the oxidation of simulated wastewaters containing the Blue Reactive 19 dye (BR-19), using a filter-press reactor, was investigated and then compared with that of a boron-doped diamond electrode supported on a niobium substrate (Nb/BDD). The electrooxidation of the dye simulated wastewater (volume of 0.1 l, with a BR-19 initial concentration of 25 mg l −1) was carried out under the following conditions: current density of 50 mA cm −2, volume flow rate of 2.4 l h −1, temperature of 25 °C and electrode area of 5 cm 2. The performances of the electrodes in the dye decolorization were quite similar, achieving 100% decolorization, and in some cases 90% decolorization was achieved by applying only ca. 0.3 A h l −1 (8 min of electrolysis). The reduction of the simulated wastewater organic load, monitored by its total organic carbon content (TOC), was greater for the Ti–Pt/β-PbO 2–Fe,F electrode obtained from an electrodeposition bath containing 1 mM Fe 3+ and 30 mM F −. In this case, after 2 h of electrolysis the obtained TOC reduction was 95%, while for the pure β-PbO 2 and the Nb/BDD electrodes the reductions were 84% and 82%, respectively. 相似文献
18.
Cold season (winter and thaw) CH 4, CO 2 and N 2O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH 4 and CO 2 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 CH 4 fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N 2O sink in winter season in northeast China. During thaw, the CH 4 and CO 2 emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N 2O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange. 相似文献
19.
A novel paper-based material containing titanium dioxide (TiO 2) photocatalyst was successfully prepared by a papermaking technique with the internal addition of inorganic fibers on which TiO 2 particles were supported. Photodegradation performance of acetaldehyde gas, an indoor pollutant, and the durability of the TiO 2-containing papers were investigated under UV irradiation. Ceramic fiber suspension and polydiallyldimethylammonium chloride as a cationic flocculant were mixed, followed by the addition of TiO 2 suspension and anionic polyacrylamide. Subsequently, the inorganic mixture was poured into a pulp suspension, and TiO 2 handsheets then prepared by a papermaking method. The tensile strength of TiO 2-containing paper without a ceramic carrier decreased by more than 30% after 240-h UV irradiation (2 mW/cm 2), although the strength of the TiO 2 sheet with ceramic fibers remained reasonably stable. The efficiency of acetaldehyde decomposition by the TiO 2 paper containing an inorganic carrier was nearly equal to that of the carrier-free TiO 2 paper. Scanning electron microscopic observation suggested that most TiO 2 particles were predominantly supported on the inorganic fiber matrix, and were mostly out of contact with organic pulp fibers. The TiO 2 paper with an inorganic carrier demonstrated both excellent photocatalytic performance and durability, which before had been mutually incompatible for organic materials containing TiO 2 photocatalyst. The two-stage mixing procedure for TiO 2 sheet-making is promising for the simple manufacture of high performance paper with photocatalytic ability. 相似文献
20.
An investigation was conducted to estimate mercury emission to the atmosphere from different environmental surfaces and to assess its contribution to the local mercury budget in Chongqing, China. Mercury flux was measured using dynamic flux chamber (DFC) at six soil sites of three different areas (mercury polluted area, farmland and woodland) and four water surfaces from August 2003 to April 2004. The mercury emission fluxes were 3.5 ± 1.2–8.4 ± 2.5 ng m −2 h −1 for three shaded forest sites, 85.8 ± 32.4 ng m −2 h −1 for farming field, 12.3 ± 9.8–733.8 ± 255 ng m −2 h −1 for grassland sites, and 5.9 ± 12.6–618.6 ± 339 ng m −2 h −1 for water surfaces. Mercury exchange fluxes were generally higher from air/water surfaces than from air/soil surfaces. The mercury negative fluxes were found in tow soil sites at overcast days (mean = −6.4 ± 1.5 ng m −2 h −1). The diurnal and seasonal variations of mercury flux were observed in all sites. The mercury emission responded positively to the solar radiation, but negatively to the relative humidity. The mercury flux from air/soil surfaces was significantly correlated with soil temperature, which was well described by an Arrhenius-type expression with activation energy of 31.1 kcal mol −1. The annual mercury emission to the atmosphere from land surface is about 1.787 t of mercury in Chongqing. 相似文献
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