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排序方式: 共有73条查询结果,搜索用时 62 毫秒
1.
P.D. Francis 《臭氧:科学与工程》1987,9(4):369-390
Organic contaminants dissolved in deionized pretreated and raw mains water were reacted with ultraviolet light and ozone. Ozone first was used for partial oxidation followed by ozone combined with ultraviolet radiation to produce total oxidation. The reduction of TOC level and direct oxidation of halogenated compounds were measured throughout the treatment process. The rate of TOC reduction was compared for ozone injected upstream and inside the reactor. 相似文献
2.
Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O3 at high pH, 03/H202, O3/UV and H2O2/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O3/UV process, the effect of the H202:03 ratio in the O3/H2O2 process, and the impact of the low extinction coefficient of H2O2 in the H202/UV process. 相似文献
3.
Freestanding and crack-free titania–silica aerogels with high titanium content (i.e., Ti/Si = 1) were successfully prepared by adjusting the hydrolysis of the two alkoxide precursors to a comparable rate during the sol–gel processing. Two titania–silica aerogels were prepared by ethanol and CO2 supercritical drying methods. Well-dispersed, nanometer-sized anatase crystal domains (ca. 10 nm) were crystallized by high temperature, ethanol supercritical drying. The crystalline domains were solidly anchored to the aerogel network by Ti–O–Si bonds. Titania–silica aerogels prepared by CO2 supercritical drying method were devoid of TiO2 crystals. A molecular-level mixing was achieved and anatase TiO2 was only crystallized with difficulty by high temperature calcination (1073 K). Both aerogels were mesoporous and displayed similar open pore structure that is readily accessible to reactant molecules. However, only the titania–silica aerogel with anatase TiO2 prepared by ethanol supercritical drying was active for the gas phase, photocatalytic oxidation of volatile organic compounds (i.e., isopropanol and trichloroethylene). Catalysts prepared from Degussa P25 TiO2 displayed lower activity under similar reaction conditions. 相似文献
4.
Activated carbon adsorption of trichloroethylene (TCE) vapor stripped from TCE-contaminated water 总被引:1,自引:0,他引:1
Ground water contaminated with trichloroethylene (TCE) used in electronic, electric, dry cleaning and the like industries is often treated by air-stripping. In this treatment process, TCE in its vapor form is stripped from ground water by air stream and sometimes emitted into the atmosphere without any additional treatments. Activated carbon adsorption is one of the practical and useful processes for recovering the TCE vapor from the exhaust air stream. However, adsorption of the TCE vapor from the stripping air stream onto activated carbons is not so simple as that from dry air, since in the exhaust air stream the TCE vapor coexists with water vapor with relatively high concentrations. The understanding of the adsorption characteristics of the TCE vapor to be adsorbed on activated carbon in the water vapor-coexisting system is essential for successfully designing and operating the TCE recovery process. In this work, the adsorption equilibrium relations of the TCE vapor adsorption on activated carbons were elucidated as a function of various relative humidity. Activated carbon fibers (ACFs) were used as model activated carbon. The adsorption equilibrium relations were studied by the column adsorption method. The adsorption isotherms of TCE vapor adsorbed on sample ACFs were successfully correlated by the Dubinin-Radushkevich equation for both cases with and without coexistent water vapor. No effects of coexistent water vapor were found on the limiting adsorption volume. However, the adsorption characteristic energy was significantly reduced by the coexistence of water vapor and its reduction was successfully correlated with the equilibrium amount of water vapor adsorbed under the dynamic condition. 相似文献
5.
T.L.R. Hewer S. Surez J.M. Coronado R. Portela P. Avila B. Sanchez 《Catalysis Today》2009,143(3-4):302
Hybrid photocatalysts based on an adsorbent SiMgOx and a photocatalyst TiO2 were developed in a plate shape. The ceramic surface was coated with TiO2 by the slip-casting technique. The effect of the support in the photocatalytic degradation of trichloroethylene (TCE) was analyzed by modifying TiO2 loading and the layer thickness. Photocatalysts were characterised by N2 adsorption–desorption, mercury intrusion porosimetry, SEM, UV–vis spectroscopy and XRD. A direct relationship between the TiO2 content and the photocatalytic activity was observed up to three layers of TiO2 (0.66 wt.%). Our results indicate that intermediate species generated on the TiO2 layer can migrate through relatively long distances to react with the OH− surface groups of the support. By increasing the TiO2 loading of the photocatalyst two effects were observed: trichloroethylene conversion is enhanced, while the efficiency of the oxidation process is decreased at expenses of increasing the selectivity to COCl2 and dichloroacetylchloride (DCAC). The results are discussed in terms of the layer thickness, TiO2 amount, TCE conversion and CO2, and COCl2 selectivity. 相似文献
6.
Takeuchi M Nanba K Iwamoto H Nirei H Kusuda T Kazaoka O Owaki M Furuya K 《Water research》2005,39(11):2438-2444
At a trichloroethylene (TCE)-contaminated site in Chikura, Chiba, Japan, TCE had spread over to the first and second aquifers over years. After 8 years of pumping and treatment, finally derivative of TCE, cis-dichloroethylene (c-DCE) remained only in the second aquifer. In this study, feasibility of a low cost in situ bioremediation utilizing groundwater of the third aquifer, which contained natural dissolved methane possibly derived from natural gas field nearby, to stimulate methane-oxidizing bacteria was examined. In vitro experiment showed that a mixture of the groundwater from the second and third aquifers stimulated a growth of methane oxidizing bacteria and enhanced c-DCE degradation. The groundwater of the third aquifer was introduced into the second aquifer in situ. The population of methanotrophs with high V(max) and K(m) for methane uptake increased, resulting in successful degradation of c-DCE at a monitoring well 2m downgradient of the injection well. 相似文献
7.
Semicontinuous microcosm study of aerobic cometabolism of trichloroethylene using toluene 总被引:1,自引:0,他引:1
A semicontinuous slurry-microcosm method was applied to mimic trichloroethylene (TCE) cometabolic biodegradation field results at the Que-Jen in-situ pilot study. The microcosm study confirmed the process of aerobic cometabolism of TCE using toluene as the primary substrate. Based on the nucleotide sequence of 16S rRNA genes, the toluene-oxidizing bacteria in microcosms were identified, i.e. Ralstonia sp. P-10 and Pseudomonasputida. The first-order constant of TCE-degradation rate was 0.5 day(-1) for both Ralstonia sp. P-10 and P.putida. The TCE cometabolic-biodegradation efficiency measured from the slurry microcosms was 46%, which appeared pessimistic compared to over 90% observed from the in-situ pilot study. The difference in the TCE cometabolic-biodegradation efficiency was likely due to the reactor configurations and the effective time duration of toluene presence in laboratory microcosms (1 days) versus in-situ pilot study (3 days). The results of microcosm experiments using different toluene-injection schedules supported the hypothesis. With a given amount of toluene injection, it is recommended to maximize the effective time duration of toluene presence in reactor design for TCE cometabolic degradation. 相似文献
8.
Electron beam irradiation of water is technically the easiest way to generate OH free radicals but the efficiency of the irradiation process as an advanced oxidation process (AOP) is deteriorated by reducing species formed simultaneously with the OH free radicals. Addition of ozone to the water before or during irradiation improves the efficiency by converting the reducing species into OH free radicals and turning the irradiation process into a full AOP. The main reaction pathways of the primary species formed by the action of ionizing radiation on water in a natural groundwater with and without the presence of ozone are reviewed. Based on these data an explanation of both the dose rate effect and the ozone effect is attempted. New data are presented which illustrate the effect of alkalinity on the way in which ozone is introduced into the water, and the impact of both water matrix and chemical structure of the pollutants to the efficacy of the ozone/electron beam process. 相似文献
9.
Kai Shen Mingxiang Jiang Xinwei Yang Weizhong Zhou Qiguang Dai Xingyi Wang Li Wang Yun Guo Yanglong Guo Wangcheng Zhan 《中国稀土学报(英文版)》2023,41(4):523-530
The cerium-based catalysts were investigated for the catalytic co mbustion of trichlo roethylene(TCE) and exhibit a surprising catalytic activity.MnOx was doped into CeO2 by a citric acid(CA) sol-gel method,and the effect of Mn content on the physicochemical properties and catalytic activities of MnOx-CeO2 mixed oxides was investigated systemically.The introduction of MnOx into CeO2 can evidently improve the catalytic activity and... 相似文献
10.
Two-phase bioreactors consisting of bacterial consortium in suspension and sorbents with immobilized biomass were used to treat waste air containing chlorinated ethenes, trichloroethylene (TCE) and tetrachloroethylene (PCE). Synthetic municipal sewage was used as the medium for bacterial growth. The system was operated with loadings in the range 1.48-4.76 gm(-3)h(-1) for TCE and 1.49-5.96 gm(-3)h(-1) for PCE. The efficiency of contaminant elimination was 55-86% in the bioreactor with wood chips and 33-89% in the bioreactor filled with zeolite. The best results were observed 1 week after the pollutant loading was increased. However, in these conditions, the stability of the process was not achieved. In the next 7 days the effectiveness of the system decreased. Contaminant removal efficiency, enzymatic activity and the biomass content were all diminished. The system was working without being supplied with additional hydrocarbons as the growth-supporting substrates. It is assumed that ammonia produced during the transformation of wastewater components induced enzymes for the cometabolic degradation of TCE and PCE. However, the evaluation of nitrogen compound transformations in the system is difficult due to the sorption on carriers and the combined processes of nitrification and the aerobic denitrification. An applied method of air treatment is advantageous from both economic and environmental point of views. 相似文献