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The floatability of seven plastics (POM, PVC, PET, PMMA, PC, PS and ABS) in the presence of methyl cellulose (MC) and separation of plastics mixtures were investigated in this paper. It was found that the seven plastics can be separated into three groups by using the wetting agent MC. Group one includes POM and PVC. They are depressed at very low MC concentrations. Group two, including PET, PMMA and PC, has an intermediate floatability. Group three (ABS and PS) has a high floatability. They are almost not depressed within the given MC concentration range. In order to understand the mechanism of selective flotation of plastics and the chemical conditioning process, surface chemical factors, such as wettability of plastics and surface tension of flotation medium, and gravity factors, such as particle density and shape, were studied. It was found that the depressing effect of MC on plastics is ascribed mainly to its adsorption on the plastics surfaces. The MC molecules absorbed on plastics expose some of their polar groups oriented towards the aqueous phase, hence making the plastics surfaces hydrophilic. In addition, flotation selectivity for the plastics is dominated not only by wettability of plastics, but also by particle size, density and shape. 相似文献
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采用缺氧反硝化一接触氧化系统处理难以生物降解的PVA退浆废水,设计规模为3000m^3/d,处理后CODcr,BOD5,SS和色度的去除率分别达到96.3%,94.8%,90.2%,85.0%,出水各项指标均达到GB 4287—92表(3)中的Ⅰ级排放标准。 相似文献
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Horst Rakel Simon Gerrard Graham Piggott Gordon Crick 《Journal of Safety Research》1998,29(4):235-247
This study reports on the development of an evaluation methodology for assessing quantitatively and qualitatively the effectiveness of seminar and mass-mailing contact techniques. These techniques are used to augment traditional health and safety inspections at commercial and industrial premises in the United Kingdom. One of the major findings is that specific aims and objectives for the intervention should be developed prior to the communication exercise. This is crucial for any subsequent measurement of effectiveness, as the intended effect needs to be considered before the communication exercise takes place. Developing more systematic approaches to evaluation is an important step in helping to learn from previous experiences, that is, to build upon the foundations of good practice and avoid repeating mistakes. In time the results of systematic evaluations can be used to inform future policy making, which may help to create more effective risk reduction strategies. 相似文献
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The cuticular surface of sexually mature females of the German cockroach contains a sex pheromone that, upon contact with the male's antennae, elicits a characteristic species-specific courtship behavior. This female-specific pheromone is a blend of several long-chain methyl ketones, alcohols and aldehydes, all derived from prominent cuticular hydrocarbons found in all life stages of this cockroach. We found that contact with the antennae of 5 out of 20 assayed cockroach species elicited courtship behavior in German cockroach males. The heterospecific courtship-eliciting compounds were isolated by behaviorally guided fractionation of the active crude extracts and compared to the native sex pheromone components. We identified two active compounds from the cuticular extract of the Oriental cockroach, Blatta orientalis -- 11-methylheptacosan-2-one and 27-oxo-11-methylheptacosan-2-one; the former compound was confirmed by synthesis and proved to independently stimulate courtship in German cockroach males. These compounds share common features with, but are distinct from, any of the known contact sex pheromone components. This suggests that sex pheromone reception in the male German cockroach is unusually promiscuous, accepting a wide range of compounds that share certain features with its native pheromone, thus resulting in a broad spectrum of behavioral response to other species. We propose that several characteristics of their mating system -- chiefly, absence of closely related species in the anthropogenic environment, resulting in relaxation of selection on sexual communication, and a highly male-biased operational sex ratio -- have driven males to respond with extremely low thresholds to a wide spectrum of related compounds. 相似文献
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以津武玻璃纤维有限公司玻璃纤维废水处理工程为例,介绍压滤-水解酸化-接触氧化-过滤组合工艺的工程应用,总结并分析了工程设计及运行经验。设计处理流量50 m3/d,进水CODCr,BOD5,SS质量浓度分别为7 200,874,1 562mg/L;运行结果表明:该组合工艺对CODCr,BOD5,SS的去除率达97.9%,92.0%和91.5%以上,出水各项水质指标均达到GB 8978—1996《污水综合排放标准》中的二级排放标准。处理费用仅为1.31元/m3,处理系统运行稳定,耐冲击能力强。 相似文献