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1.
Micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate was tested for its ability to analyze mixtures containing three dioxin derivatives. Dioxin-containing samples, subjected to photocatalytic oxidation using TiO 2 and/or SnO 2 as the semiconductor catalyst were analyzed by MEKC to obtain the rate constant for each dioxin when it was degraded individually or in the presence of the other two dioxins. A significant degree of analyze competition was observed and the mixed catalyst offered important synergism. 相似文献
2.
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
3.
Excised soy-beanroots were exposed to an aqueous solution of five homologous chlorobenzenes in constant concentration. The results were in general agreement with water-lipid partitioning. The relationship between the bioconcentration factor and the octanol-water partition coëfficiënt (K OW) can be used to estimate bioconcentration. Effective equilibrium was reached within 2.5 hours for 1,2-di-, 1,3,5-tri- and 1,2,3,4-hexachlorobenzene and after a mean of 10.1 and 17.9 hours for penta- and hexachlorobenzene respectively. For 1,2-dichlorobenzene, 1,3,5-trichlorobenzene and 1,2,3,4-tetrachlorobenzene the elimination rate constant was > 4.1, and 0.46 and 0.30 hr −1 for penta- respectively hexachlorobenzene. In the range log K ow 4.56–5.77, k 2 was negatively correlated with log K OW but k 1 was not correlated with log K OW.. 相似文献
4.
Three types of surfactants and related reference compounds containing sulfonate (-SO 3Na), sulfate (-OSO 3Na) or thioether carboxylate (-S-Cn-COOK) group were photodecomposed in an aqueous heterogeneous dispersion system. The photomineralization to SO 42−ions was examined for the surfactants with different chemical structures. The photocatalytic activities of TiO 2 and ZnO were compared for the sulfonates of dodecylbenzene sulfonate (DBS) and polystyrene sulfonate (PSS), the sulfates of sodium dodecyl sulfate (SDS), and the potassium salts of S-dodecylthioglycol acid (TGA), S-dodecylthiopropionic acid (TPA) and S-dodecylthiomalic acid (TMA). ZnO catalyst exhibited higher activity in the formation of SO 42−ion than TiO 2 catalyst. 相似文献
6.
UV/TiO 2/H 2O 2, UV/TiO 2 and UV/H 2O 2 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/TiO 2/H 2O 2 treatment supported the highest pollutant removal, COD removal, and dechlorination efficiencies followed by UV/TiO 2 and UV/H 2O 2. 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/TiO 2/H 2O 2 treatment. No pollutant removal was observed in the controls conducted with H 2O 2 or TiO 2 only. Inoculation of all the photochemically pre-treated mixtures with activated sludge microflora was followed by complete removal of the remaining pollutants. Combined UV/TiO 2/H 2O 2-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/H 2O 2, and UV/TiO 2 treatments lead to the formation of recalcitrant photoproducts, some of which were chlorinated. 相似文献
7.
以废弃物沼渣和含铁剩余污泥为原料,采用一步热解法制备沼渣生物炭基Fenton催化剂(以下简称催化剂),构建了非均相Fenton反应体系处理含吡虫啉模拟废水,考察了H2 O2和催化剂用量对吡虫啉去除率的影响.结果表明,非均相Fenton反应体系中,H2 O2最佳投加量为0.50 g/L,催化剂最佳投加量为1.00 g/L... 相似文献
8.
A mathematical model describing the rate of carbon disulfide (CS 2) removal due to coupled reactions has been developed. Kinetic studies were carried out in a fixed bed reactor under atmospheric pressure and a range of temperatures (85–125 °C). The effects of flow rate, CS 2 inlet concentration, temperature and relative humidity were analyzed. A kinetic model based on axial dispersion, external and internal mass-transfer resistances, as well as effects of S deposition on the inner-face of the catalyst was in agreement with the CS 2 experimental breakthrough curves. The mathematical model can be used for process design and scale up of similar systems. 相似文献
9.
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
10.
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
11.
UV/Fenton, near-UV-visible/Fenton, dark Fenton, and H 2O 2/UV reactions have been used to treat simulated dyehouse effluents representing wastewater from the textile dyeing and rinsing process. Experiments were carried out in a lab - scale photochemical reactor using concentrations of 0.5–25 mM H 2O 2, 0.04-0.5 mM Fe 2+-ion and different dilutions of textile wastewater. To assess the extent of mineralization, decolourization kinetics and the effect of different fight sources on treatment efficiency, DOC, optical density at 254 nm and 600 nm wavelength and residual H 2O 2 concentrations were measured during the course of the advanced oxidation reactions. Comparative evaluation of the obtained results revealed that the decolourization rate increased with applied H 2O 2 and Fe 2+-ion dose as well as the strength of the synthetic textile wastewater. The best results were obtained by the near - UV/visible/Fenton process with a decolourization rate constant of 1.57 min −1, a UV 254nm reduction of 97% and a DOC removal of 41% at relatively low doses of the H 2O 2 oxidant and Fe 2+-ion catalyst within 60 min treatment time. 相似文献
12.
The present study performed a roadside data analysis to provide baseline data for exploring associations between environmental exposure to four gaseous pollutants and health effects on residents living near roadways. The yearly roadside concentrations of CO and SO 2 showed a well-defined decreasing trend, whereas those of NO 2 and O 3 exhibited the reverse trend. In most cases, the diurnal trends of the roadside concentrations were well-defined for all seasons, plus the daytime concentrations were higher than the nighttime concentrations. In contrast to the other target pollutants, the daytime O 3 concentrations observed at the roadside sites were lower than those observed at the residential site, likely due to high-levels of fresh NO from traffic emissions that rapidly react with O 3, thereby reducing the O 3 roadside level. The Sunday roadside concentrations of CO, NO 2, and SO 2 were similar to or somewhat lower than the weekday concentrations. Conversely, for O 3, the Sunday roadside concentrations were similar to or somewhat higher than the weekday concentrations. The higher O 3 concentrations on Sunday may be due to the reduced titration from a decrease in NO x emissions under VOC-limited conditions (low VOC/NO x conditions). The monthly averages of O 3 concentrations exhibited the reverse seasonal variation to the other target compounds, with peak O 3 concentrations between April and June, and the second peak between August and October. It is also suggested that for O 3, the 8-h standard is more stringent than the 1-h standard, while for NO 2 and SO 2, the 1-h standard is more stringent than the 24-h standard. The multiple regression equations obtained from the relationship between the concentrations and five meteorological parameters indicated that the number and type of meteorological variables in the equations varied according to the pollutant, monitoring station, or season. 相似文献
13.
Atmospheric NO 2 was taken up by samples of various soils and building stones. The NO 2 uptake rate constants were highest in soil samples taken during the summer months. However, the NO 2 uptake rate constants of the soils and building stones were not significantly correlated with any of the following variables: moisture, pH, ammonium, nitrite, or nitrate. NO 2 uptake by soil and stone was not abolished by autoclaving indicating a chemical uptake process. NO 2 uptake by acidic and air-dry soils and stones resulted in nearly stoichiometric reduction of NO 2 to NO. This reduction was enhanced by the addition of ferrous iron and was further enhanced by incubation under 1 ppmv SO 2. The results suggest that NO 2 reduction may be coupled to oxidation of ferrous to ferric iron which may be reduced again by atmospheric SO 2 thus regenerating the ferrous iron content of the soil or stone. Conversion of NO 2 to NO was not observed in neutral or/and moist soils and stones. NO 2 was also taken up by purified and sterilized quartz sand moistend with water. This uptake was enhanced by addition of humic material but not by addition of bacteria which both had been extracted from genuine soil. Under most conditions, only uptake but no release of NO 2 was observed. However, NO 2 was released in air-dry soils that were heated to 45–65°C, or in ammonium-fertilized soil or stone that was drying up at room temperature. Under the latter conditions mimicking field practice, the NO 2 release reached rates that were similar to the NO release rates. 相似文献
14.
The recognition of pharmaceuticals as significant environmental contaminants has only been a recent phenomenon. Therefore there is a paucity of data relating to the fate and effects of pharmaceuticals once they enter an aquatic receiving system. The amount of work that needs to be done in terms of risk assessment for pharmaceuticals required by regulatory agencies is substantial. This paper has determined the environmental partitioning coefficient ( Kd) of 13 diverse human pharmaceuticals in three model systems of differing combinations of solid phases and solutions. The Kd values were then compared with distribution values of the pharmaceuticals in the human body determined from pharmacological studies. This was done to assess the functional relationship between Kd and distribution values in the human body ( VD). Kd values ranged from 3 to 2450 L kg −1. Regression coefficients ranged from r2 = 0.62–0.72, indicating that VD values are a useful indicator for the Kd values of the tested pharmaceuticals within the batch sorption systems. The relationship between Kd and VD should therefore be further explored to determine whether this relationship can be applied to a broader range of pharmaceuticals in more diverse environmental systems. Exploiting available human pharmacological data in such a way would be of great benefit in prioritising human pharmaceuticals as environmental contaminants in the risk assessment process. 相似文献
15.
The sorption of the pyrethroid, esfenvalerate, to the dissolved and/or dispersed fraction of eight different natural humic compounds has been investigated. The dissolved organic matters (DOMs) included in this study originate from ground water, soil pore water, and surface waters. Sorption was modelled at DOM concentration levels where equilibrium partitioning of esfenvalerate between DOM and the aqueous bulk phase prevails. The inherent characteristics of the eight different humic materials, quantified in the preceding paper by Thomsen et al. (2002, this issue (PII: S0045-6535(02)00335-1)), have been used as explanatory variables for modelling this equilibrium partitioning. Using a reverse QSAR approach based on by projection-into-latent-structure regression (PLS-R) inherent sorbent properties determining for the sorption affinity of esfenvalerate to DOM were analysed. For all humic substances a decrease in the DOM-normalised equilibrium-partitioning coefficient, KDOM, with increasing concentration of DOM was observed. Significant variations in KDOM values, as function of the inherent characteristics of the individual humic substances, were found at DOM concentrations of 75 and 100 ppm, respectively. The latter is a strong indication of variations in sorption mechanisms of esfenvalerate to DOM of varying inherent properties. Groupings in the principal property space quantifying DOMs may indicate that separate models are needed for quantifying the equilibrium partitioning to different classes of DOM. 相似文献
16.
Aqueous 4-nitrophenol solutions containing TiO 2 or Al 2O 3 nanoparticles were irradiated with electron beam. 4-nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO 2 or Al 2O 3 (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), TiO 2 or Al 2O 3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO 2 or Al 2O 3 during irradiation is just due to adsorption. 相似文献
17.
The Ah or 2,3,7,8-TCDD receptor protein plays an important role in mediating the biologic, toxic and genotoxic effects of aryl and halogenated aryl hydrocarbons. An assessment of the physicochemical parameters which facilitate ligand: receptor interactions was determined by multiple parameter linear regression analysis of the relative receptor binding affinities of a series of 7-substituted-2,3-dichlorodibenzo-p-dixoins (Eq 1), 8-substituted-2,3-di (Eq. 2) and 2,3,4-trichlorodibenzofurans (Eq 3). The results demonstrate that substituent lipophilicity (π) and molecular volumes were (Eq.1) log (I/EC50) = 1.24 π + 6.10 (Eq.2) log (I/EC50) = 1.10 π + 5.19 (Eq.3) log (I/EC50) = 1.09 π + 5.77 the major determinant factors governing interactions between the rat hepatic cytosolic receptor protein and the diverse substituted ligands. It has been shown that there are marked differences in species sensitivity to 2,3,7,8-TCDD (i.e. guinea pig > rat maice > hamster) although hepatic receptor levels in these species are comparable. QSAR analysis of the receptor binding EC50 data for the 7-substituted-2,3-dichlorodibenzo-p-dioxins using rat (Eq. 1), mouse (Eq. 4), guinea pig (Eq. 5) and hamster (Eq. 6) hepatic cytosol demonstrated that there were significant differences in these equations. However it was also noted that (Eq.4) log (I/EC50) = 0.95 + 0.93 Es + 5.28 (Eq.5) log (I/EC50) = 0.94 + 0.579 σp + 6.13 (Eq.6) log (I/EC50) = 0.70 + 1.227 σp + 6.38 physicochemical factors which are important for ligand-receptor interactions were identical for the most sensitive (guinea pig) and least sensitive (hamster) species. These results indicate that events which follow the initial ligand-receptor interaction must be the major factors which determine species sensitivity to 2,3,7,8-TCDD. 相似文献
18.
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-H 2O 2 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-H 2O 2 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-H 2O 2 AOP was only effective at reducing DBPs at UV fluences of more than 1000 mJ cm −2and initial H 2O 2 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 UV 254, respectively. 相似文献
19.
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
20.
The data on dioxin and furan emissions revealed, based on individual analysis for 2,3,7,8-TCDD, TCDD, 2,3,7,8-TCDF and TCDF for the six test periods and the operation of the two RDF-fired boilers, that there is no apparent consistent relationship between the dioxin and furan emissions and the individual or combined (averaged) boiler steam flow, total flue gas flow, sidewall furnace temperature, furnace temperature at 2-second residence time, or total furnace residence time at this plant. Only RDF feeder balance begins to show a correlation. However, there was a difference between RDF-natural gas firing and RDF-only firing; the RDF-only firing had lower PCDD and PCDF emissions while consistently operating at lower excess air. The dioxin and furan emissions from this testing are comparable to the low end of the range of these emissions measured by the U.S. EPA at resource recovery plants in the past 4 years. This may be due in part to the calculated average furnace retention of 4 to 5 seconds during Tests #4–6, with average furnace temperatures at 2-second residence time from 1650°F to 1750°F. However, there was no correlation between dioxin and furan emissions in the stack and individual boiler operation, as judged by the average concentrations of O2, CO, CO2, 1-CO/CO2), NOx, HCl, SO2, or TSP, and furnace upset conditions versus normal operation as judged by instantaneous steam flow, sidewall furnace temperature, O2, CO, NOx, or SO2. 相似文献
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