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1.
Potential particulate pollution derived from UV-induced degradation of
odorous dimethyl sulfide 总被引:1,自引:0,他引:1
UV-induced degradation of odorous dimethyl sulfide (DMS) was carried out in a static White cell chamber with UV irradiation. The
combination of in situ Fourier transform infrared (FT-IR) spectrometer, gas chromatograph-mass spectrometer (GC-MS), wide-range
particle spectrometer (WPS) technique, filter sampling and ion chromatographic (IC) analysis was used to monitor the gaseous and
potential particulate products. During 240 min of UV irradiation, the degradation e ciency of DMS attained 20.9%, and partially
oxidized sulfur-containing gaseous products, such as sulfur dioxide (SO2), carbonyl sulfide (OCS), dimethyl sulfoxide (DMSO),
dimethyl sulfone (DMSO2) and dimethyl disulfide (DMDS) were identified by in situ FT-IR and GC-MS analysis, respectively.
Accompanying with the oxidation of DMS, suspended particles were directly detected to be formed by WPS techniques. These
particles were measured mainly in the size range of accumulation mode, and increased their count median diameter throughout
the whole removal process. IC analysis of the filter samples revealed that methanesulfonic acid (MSA), sulfuric acid (H2SO4) and
other unidentified chemicals accounted for the major non-refractory compositions of these particles. Based on products analysis and
possible intermediates formed, the degradation pathways of DMS were proposed as the combination of the O(1D)- and the OH- initiated
oxidation mechanisms. A plausible formation mechanism of the suspended particles was also analyzed. It is concluded that UV-induced
degradation of odorous DMS is potentially a source of particulate pollutants in the atmosphere. 相似文献
2.
3.
The degradation of nonylphenol (NP) in aqueous solution with UV, H2O2/UV, and Fenton/photo-Fenton processes was studied. The efficacy of direct and hydrogen peroxide photolysis proved to be dependent on the pH value. The addition of H2O2 to UV treatment improved NP degradation. The application of UV photolysis and the H2O2/UV system at pH 7 resulted in low pseudo first-order rate constants at 10-4 sec-1. In the experiments at elevated pH values the pseudo-first order rate constants increased to 10-3 sec-1. The efficacy of the Fenton process was lower in comparison with UV and hydrogen peroxide photolysis. The addition of UV irradiation to the H2O2/Fe2+ system substantially improved NP degradation efficacy. In terms of performance, the photo-Fenton process was similar to the H2O2/UV process. The most favourable process for complete nonylphenol degradation considering both operational cost and treatment efficacy was H2O2/UV at pH 11 and 250 mol/L H2O2. 相似文献
4.
5.
Doping amine functional groups into SiO2/TiO2 films for enhancing the decomposition of formaldehyde has been investigated
using the modified sol-gel method to prepare organic-inorganic hybrid photocatalysts via the co-condensation reaction of
methyltrimethoxysilane (MTMOS) and amine functional groups. n-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS)
and 3-aminopropyl-trimethoxysilane (APTMS) were selected to study the e ect of amine functional groups on the enhancement of
formaldehyde adsorption and degradation under a UV irradiation process. Physicochemical properties of prepared photocatalysts were
characterized with nitrogen adsorption-desorption isotherms measurement, X-ray di raction (XRD) and Fourier transform infrared
(FT-IR) spectroscopy. The results indicated that the APTMS/SiO2/TiO2 film demonstrated a degradation e ciency of 79% superior
to those of SiO2/TiO2 and AEAPTMS/SiO2/TiO2 films due to the synergetic e ect of adsorption and photocatalytic properties. The
APTMS/SiO2/TiO2 film can be recycled with about 7% decreasing of degradation e ciency after seven cycles. 相似文献
6.
Fresh TiO2 was found to possess a strong germicidal activity even without UV irradiation. Live Yeast (Saccharomyces cerevisiae) cells in contact with fresh TiO2 were found deformed and dead after 15 min contact. The cause of germicidal activity was discussed from the observed cell deformation, lysis and increased absorption at 1680 cm-1 in FT-IR spectra of the affected cells, which proved the oxidizing effect of fresh TiO2 to cells. The deformation caused by the stretching of cell wall and pressure built-up inside the cell, led to cell burst and release of intracellular materials. The degree of cell deformation was found positively related with the wetting property of TiO2. Cells are negatively charged, for Gram-negative cell (thinner cell wall), a higher germicidal effect was observed than Gram-positive cells. The germicidal effect of TiO2 gradually decreases after exposure to air at room temperature, as the wetting property decreases. This kind of germicidal activity was more effective compared to other germicidal process such as UVA/TiO2 or Ag+. This shed light on designing new germicidal material either maintained by visible light irradiation, or by oxidation effect generated by reactive oxygen species. 相似文献
7.
紫外线分解腐植酸的研究 总被引:1,自引:0,他引:1
通过我们对紫外线照射前后腐植酸(HA)的理化性质进行了较系统的研究。发现光照可使部门HA分解,并使紫外、红外、核磁共振等光谱发生明显改变;短时间辐射(不超过20分钟)可催化自由基的产生;光照氯化后的HA溶液可使总有机物的组成发生明显变化。 相似文献
8.
Bromate ion formation in dark chlorination and ultraviolet/chlorination
processes for bromide-containing water 总被引:1,自引:0,他引:1
Bormate (BrO3^-) is a carcinogenic chemical produced in ozonation or chlorination of bromide-containing water. Although its formation in seawater with or without sunlight has been previously investigated, the formation of bromate in dilute solutions, particularly raw water for water treatment plant, is unknown. In this article, the results of bench scale tests to measure the formation rates of bromate formation in dilute solutions, including de-ionized water and raw water from Yangtze River, were presented in dark chlorination and ultraviolet (UV)/chlorination processes. And the effects of initial pH, initial concentration of NaOCl, and UV light intensity on bromate formation in UV/chlorination of the diluted solutions were investigated. Detectable bromate was formed in dark chlorination of the two water samples with a relatively slow production rate. Under routine disinfecting conditions, the amount of formed bromate is not likely to exceed the national standards (10 μg/L). UV irradiation enhanced the decay of free chlorine, and, simultaneously, 6.6%-32% of Br^- was oxidized to BrO3^-. And the formation of bromate exhibited three stages: rapid stage, slow stage and plateau. Under the experimental conditions (pH = 4.41-11.07, CCl2= 1.23-4.50 mg/L), low pH and high chlorine concentration favored the generation of bromate. High light intensity promoted the production rate of bromate, but decreased its total generation amount due to acceleration of chlorine decomposition. 相似文献
9.
The response of the antioxidant defense system of an intertidal macroalgae Corallina officinalis L. to different dosages of UV-B irradiation was investigated. Results showed that superoxide dimutase (SOD) and peroxidase (POX) increased and then maintained at a relatively stable level when subjected to UV-B irradiation. Catalase (CAT) activity under medium dosage of UV-B irradiation (Muv) and high dosage of UV-B irradiation (Huv) treatments were significantly decreased. Ascorbate peroxidase (APX) activity first remained unaltered and then increased in Huv treatment. In addition, the assay on isozymes was carried out using non-denaturing polyacrylamide gel electrophoresis (PAGE). The activities of some SOD isoforms were altered by UV-B. Two new bands (POX V and POX Ⅶ) appeared upon exposure to all three UV-B dosages. CAT Ⅲ activity was increased by low dosage of UV-B irradiation (Luv),whereas CAT Ⅲ and CAT Ⅳ disappeared when the alga was exposed to Muv and Huv. Two bands of APX (APX Ⅵ and APX Ⅶ)were increased and a new band (APX X) was observed under Huv exposure. H2O2 and thiobarbituric acid reacting substance (TBARS)increased under Muv and Huv treatments. Overall, UV-B protection mechanisms are partly inducible and to a certain extent sufficient to prevent the accumulation of damage in C officinalis. 相似文献
10.
以铜绿微囊藻为研究对象,考察了H2O2与UV工艺对铜绿微囊藻的灭活特点及光合活性的影响.结果表明,在0~2mmol.L-1H2O2投加范围内,随H2O2投加量的增大,对铜绿微囊藻的灭活效果不断提高,藻的光合活性不断下降;而投加量超过2 mmol.L-1后,灭活率并无明显提高;UV工艺对铜绿微囊藻有较好的灭活效果,在藻浓度为35×108个/L条件下,紫外线剂量达91.8 mJ.cm-2即可使藻停滞生长7 d以上;UV工艺对藻光合活性的降低效率高于H2O2工艺,且各活性参数随紫外线剂量的升高呈指数衰减;在达到较好的灭活效果时,UV工艺对藻液UV254升高的控制优于H2O2工艺. 相似文献