共查询到20条相似文献，搜索用时 62 毫秒
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采用化学氧化还原-中和-絮凝沉淀法处理电镀废水中铬,研究了还原pH值、絮凝pH值、絮凝剂的用量、沉降时间对处理效果的影响.还原六价铬的最佳pH在2.0～2.2之间时,絮凝最佳pH值为9时,加入PAM,絮凝时间为0.5小时絮凝效果最好,处理后的Cr浓度最小. 相似文献
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三价铬的毒性虽然小于六价铬,但在自然界的氧化条件下,还会引起第二次污染。目前,在环境分析方面,国内外文献报导的分析方法,都是采用间接方法。这种方法在三价铬含量高时,或者铁、矾、汞、锡等元素含量高时,直接影响三价铬的测定。 本文试图用纸上层析方法将三价铬固定到原点,剪下后用10％H_2SO_4溶解,用0.1％KM_nO_4氧化至六价铬,然后用二苯氨基脲显色。测定范围是0.5μg～100μg。它不仅克服间接法的上述缺点,而且具有简便、经济和准确度高等特点。分析方法如下: 相似文献
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为了遵守欧盟WEEE指令,文中采用SPE法,以经处理过的锯屑作为吸附剂富集电子电气产品中超痕量六价铬,研究了pH、吸附剂用量、Cr(Ⅵ)初始浓度、温度对吸附平衡的影响,得出了最优化富集条件和在此条件下动力学、熟力学特性.结果显示,通过调节pH值可使三价铬与六价铬发生吸附分离,六价铬在锯屑上吸附是单层、自发、吸热过程,活化能较小,说明吸附是需要消耗时间;其时间变化规律为:前50min内快速吸附(速率控制为主)后数小时慢吸附过程(扩散控制为主);通过富集,可使目标物浓度浓缩50～100倍,大大降低了痕量浓度检出限至μg·L-1,ng·L-1水平,为EE产品中有害物质污染控制提供了技术基础,也为更好地实现废旧电子电气产品中有用物质回收、再利用、再循环提供绿色指导方案. 相似文献
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硫酸亚铁除地下水中六价铬 总被引：2，自引：0，他引：2
王仲军 《唐山师范学院学报》2006,28(2):41-42
研究了受铬污染地下水的治理方法和技术,发现地下水中六价铬在中性条件下很低容易用亚铁除去。Fe(Ⅱ)/Cr(Ⅵ)摩尔比为3,六价铬去率达100%。反应速度快。可数分种内完成。Fe(Ⅱ)还原Cr(Ⅵ)可采用接触过滤,不需要反应池,投资少,运行费用低。 相似文献
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针对高中化学中二氧化硫水溶液中滴加氯化钡溶液是否有沉淀的知识点,设计了pH值对反应的影响的实验。结果表明:实验表明当pH≥10时,会有BaSO3沉淀。当沉淀中加入盐酸到溶液pH为4时,沉淀开始溶解,完全溶解时pH为1。充分说明通过调节SO2与BaCl2溶液的pH值可以控制是否有BaSO3沉淀生成。这种设计对于培养学生的严谨科学思维有着重要的意义。 相似文献
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为了遵守欧盟WEEE指令,文中采用SPE法,以经处理过的锯屑作为吸附剂富集电子电气产品中超痕量六价铬,研究了pH、吸附剂用量．Cr（Ⅵ）初始浓度、温度对吸附平衡的影响,得出了最优化富集条件和在此条件下动力学、热力学特性。结果显示,通过调节pH值可使三价铬与六价铬发生吸附分离,六价铬在锯屑上吸附是单层、自发、吸热过程,活化能较小,说明吸附是需要消耗时间;其时间变化规律为：前50min内快速吸附（速率控制为主）后数小时慢吸附过程（扩散控制为主）;通过富集,可使目标物浓度浓缩50～100倍,大大降低了痕量浓度检出限至μg·L^-1,ng·L^-1水平,为EE产品中有害物质污染控制提供了技术基础,也为更好地实现废旧电子电气产品中有用物质回收、再利用、再循环提供绿色指导方案。 相似文献
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华雪莹 《青苹果(高中版)》2010,(8):46-47
大家都知道．FeCl3溶液为棕黄色,当向FeCl3溶液中加入不同的试剂时,会产生各种不同的颜色变化,这是因为在FeCl3溶液中．由于三价铁离子具有强氧化性．可与多种物质发生氧化还原反应。又因其是一弱碱根,易发生沉淀反应和水解反应：还因其外围电子结构的特殊性． 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献
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正A One day a pig went to the stable(马棚)to see his good friend,an oldhorse,and was going to stay there forthenight.Night came and it was time forsleep.The pig went into the straw heap(稻草堆)and lay comfortably.A longtime passed,but the horse was stillstanding there and did not move.Thepig asked the horse why he did not go tosleep."Standing like this is the begin-ning ofsleeping,"answered the horse. 相似文献
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《今日中学生》2014,(9)
正1.Any fool can count the seeds in an apple.Only God can count all the apples in one seed.2.Happy families are all alike;every unhappy family is unhappy in its own way.3.Memories are the key not to the past,but to the future.4.Sometimes in the dark you see what you want to see.5.There is a great difference between 相似文献
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《重庆大学学报(英文版)》2014,(2)
正Scope and Policy The Journal of Chongqing University-English Edition(JCQU-E)is a peerreviewed journal publishing research articles in multiple disciplines of science and technology,covering civil and environmental engineering,chemical engineering,biotechnology,mechanical and electrical engineering,computer and data processing,mining,metallurgy,materials science,and interdisciplines thereof. 相似文献