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981.
有机粘土矿物对水中低浓度菲的吸附性能和机理 总被引:2,自引:0,他引:2
分别选用十六烷三甲基溴化铵(HDTMA-Br)、四甲基溴化铵(TMA-Br)、聚乙二醇(PEG)表面活性剂改性天然粘土矿物,研究其对水中低浓度多环芳烃类难降解有机物菲的吸附性能和机理,并讨论了有机粘土的用量对吸附菲的性能的影响,验证了有机粘土矿物吸附菲后的稳定性.3种有机粘土矿物对菲的吸附等温线均呈中凹型,表现为分配系数(Kp)逐渐增大,表明吸附是分配作用和溶剂化效应共同作用的结果.根据Kp及土样有机碳含量(foc)所得的经有机碳归一化的分配系数(Koc)基本为常数,远远高于天然土壤/沉积物的Koc.在相同实验条件下,3种有机粘土矿物中HDTMA改性粘土矿物对菲的吸附性能最强,PEG改性粘土矿物次之,TMA改性粘土矿物最差. 相似文献
982.
To understand the dechlorination ability of chlorobenzenes (CBs) and polychlorinated biphenyls (PCBs) by untamed microorganisms under anaerobic condition and to correlate gas chromatographic properties with the occurrence of reductive dechlorination, introduction of CBs and PCBs in the culture medium inoculated with microorganisms from sludge and sediment, respectively, were performed. Three kinds of culture media preparing from sludge, river water and a synthetic medium were used in the experiments. HCB was degraded to 1,3,5-trichlorobenzene (1,3,5-TCB) and 1,3-dichlorobenzene (1,3-DCB) in both sludge medium and synthetic medium with inoculated microorganisms. Three PCB congeners including 2,3,4-, 3,4,5- and 2,3,4,5-CBp (chlorinated biphenyl) were not found to be dechlorinated in the river water medium with inoculation culture but to be dechlorinated in the synthetic medium. MNDO methodology was used to compute theoretical dechlorination reaction heats and GC-ECD techniques were used to estimate chromatographic data of CB and PCB congeners. Both CB and PCB congeners showed that dechlorination by untamed microorganisms under anaerobic mixed cultures were more likely to occur when larger amounts of energy were released and greater deltaln RRT value between the parent congener and the daughter product was observed. Deltaln RRT provided a more precise information on the singularity of PCBs ortho-dechlorination in an aspect of thermodynamic favorable rule. 相似文献
983.
984.
Tsai CH Huang YJ Chen JC Liao WT Fang GC 《Journal of the Air & Waste Management Association (1995)》2003,53(10):1225-1232
The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH3SCH3, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS2) or sulfur dioxide (SO2). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O2)/DMS molar ratio slightly improved the removal efficiency. In an O2-free environment, DMS was converted primarily to CS2, methane (CH4), acetylene (C2H2), ethylene (C2H4), and hydrogen (H2), with traces of hydrogen sulfide (H2S), methyl mercaptan (CH3SH), and dimethyl disulfide. In an O2-containing environment, the species detected were SO2, CS2, carbonyl sulfide, carbon dioxide (CO2), CH4, C2H4, C2H2, H2, formaldehyde, and methanol. Differences in yield of products were functions of the amounts of added O2 and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes. 相似文献
985.
Photocatalytic oxidation of pesticides in aqueous media irradiated by UV light is a rapidly growing field of research. Therefore, the treatment technology for degradation of propoxur (an insecticide) using titanium dioxide coated on the supports such as activated carbon, zeolite, brick, quartz and glass beads, was performed in this research. Results show that GAC/TiO2 is the best complexing agent for oxidizing propoxur because of its adsorption properities. The others follow the sequence: plain TiO2 > glass beads > zeolite > brick > quartz. The degradation rate of propoxur with plain TiO2 is higher than that with TiO2/GAC complexing agent. But the mineralization rate of propoxur with plain TiO2 is lower than that with TiO2/GAC complexing agent. However, it can be concluded that using GAC as the support can improve the photocatalytic efficiency. 相似文献
986.
We developed a risk-based approach to assess how the valve closure behavior of Asiatic clam Corbicula fluminea responds to waterborne copper (Cu) and cadmium (Cd). We reanalyzed the valve closure response data from published literature to reconstruct the response time-dependent dose-response profiles based on an empirical three-parameter Hill equation model. We integrated probabilistic exposure profiles of measured environmental Cu and Cd concentrations in the western coastal areas of Taiwan with the reconstructed dose-response relationships at different integration times of response to quantitatively estimate the valve response risk. The risk assessment results implicate exposure to waterborne Cu and Cd may pose no significant risk to clam valve activity in the short-time response periods (e.g., <30 min), yet a relative high risk for valve closure response to waterborne Cu at response times greater than 120 min is alarming. We successfully linked reconstructed dose-response profiles and EC50-time relationships associated with the fitted daily valve opening/closing rhythm characterized by a three-parameter lognormal function to predict the time-varying bivalve closure rhythm response to waterborne metals. We parameterized the proposed predictive model that should encourage a risk-management framework for discussion of future design of biological monitoring systems. 相似文献
987.
A novel method for assaying and calculating the toxicity of water-insoluble pesticides to green algae has been put forward in this work. First, a solvent is selected for use in bioassays; there should be a detailed screening to identify a solvent with inherently low toxicity to the test organism. Second, the EC50 is determined for selected pesticides by measuring the toxicity of various concentrations of each of the selected pesticides in a fixed concentration of selected solvent. Third, concentrations of the selected solvent are varied and the EC50 of each pesticide tested is assayed at a fixed concentration. Fourth, several suitable groups of solvent concentrations are selected and the corresponding EC50 values of tested pesticides are considered to establish the linear regression equation. Letting the solvent concentration be zero, one calculates the corresponding EC50 value, which corresponds to the inherent toxicity of the tested pesticide. 相似文献
988.
报道了自制混凝剂产品处理废纸造纸废水的工程应用情况。经过 1年多的运行结果表明 ,当进水CODCr、悬浮物浓度分别为 972mg/L、82 5mg/L以及色度为 3 0 0倍时 ,采用该工艺处理后 ,CODCr去除率平均为 95 .7% ,SS去除率平均为 98.9% ,色度去除率平均为 99.3 % ,出水水质远低于国家一级排放标准 (GB3 5 44 - 92 ) ,并且工厂实践表明 ,对生产有显著的效益 ,从而证明该方法对于废纸造纸废水的处理是可行的。该处理工艺设备简单 ,系统运行稳定 ,操作方便 ,成本低 相似文献
989.
990.
Effect of photosensitizer diethylamine on the photodegradation of polychlorinated biphenyls 总被引:2,自引:0,他引:2
The objective of this study was to investigate the effect of diethylamine and xenon simulated sunlight on the photodegradation of two forms of PCBs including PCBs in transformer oil and PCB congener 138. The result of GC chromatograms illustrated the shifting pattern of higher chlorinated biphenyls in transformer oil degraded to lower chlorinated biphenyls with the extension of exposure time. The effect of diethylamine and xenon simulated sunlight was significant on the photodegradation of both PCBs in transformer oil and congener 138. The initial degradation rates of congener 138 (1.14 x 10(-9) to 4.47 x 10(-9) mol l(-1) h(-1)) were in direct proportion to the initial concentrations of congener 138 which confirmed the pseudo-first-order reaction of PCB photodegradation. The apparent quantum yields (phi) of congener 138 using diethylamine in xenon photoreactor were ranged between 2.08 x 10(-2) and 9.8 x 10(-4). PCB congeners 123, 97, 70, 67, 33, 29, 17, 12, and 9 were detected as the descendants of the photodegradation of congener 138 through dechlorination. The major pathway of congener 138 photodegradation in this study was via para-dechlorination. 相似文献