镍离子对分光光度法测定水样中COD的影响

通过测定Cr3+、Cr2O72-和Ni2+ 的吸收曲线及标准水样的COD,研究了Ni2+对分光光度法测定COD的影响.结果表明,当水样中Ni2+质量浓度＜100 mg/L时,对测定结果无明显影响;若水样中Ni2+质量浓度＞100 mg/L时,应将水样稀释后再进行测定.     

不同浓度范围废水COD检测条件探讨

针对一些废水在处理过程中COD范围差异大,COD测定准确度、精密度低的问题,考察了不同浓度范围影响COD测定的关键性因素,结果显示:在440、600 nm处,Cr(Ⅵ)浓度不适会引起COD测定准确度、精密度降低.采用c( 1/6 K2Cr2O7)为0.02、0.05、0.5 mol/L的重铬酸钾溶液,分别对COD为0～...     

对5B智能型快速测定仪的改造

COD测定方法最常见的是重铬酸钾法和高锰酸钾法。其优点:K2Cr2O7在加热回流条件下,对诸多有机化合物的氧化率达到95～100%,方法准确可靠,重现性好,适用范围广。缺点是分析时间长,能源浪费大,试剂中银盐、铬盐(Cr6+)、汞盐用量大,造成二次污染。5B型智能COD快速测定仪是应用催化快速法设计并制造的,简便、快速、试剂量少、能省电、抗氯干扰。但需要厂家提供的专用氧化剂与催化剂,精密度差。文章通过对5B型智能COD快速测定仪改造后利用密封消解法测定COD一次可以测定6个水样,速度快,试剂量少,准确度高,已成为我公司监测水中COD的主要手段。     

氧化还原滴定法简易快速测定化学需氧量

本文所介绍的K2Cr2O7法测化学需氧量(简称CODcr)的简易快速测定法，是用K2Cr2O7作标准溶液的氧化还原滴定法。实验的原理是：在水样中加入过量的K2Cr2O7标准溶液，在强酸性和加热煮沸下，回流10分钟，使Km与有机化合物和还原性物质充分作用反应为Cr2O7^2- 14H^ 6e←→2Cr^2 7H2O。当样品冷却至室温时，将其稀释。待其再度冷却后，其中过量的K2Cr2O7用还原剂硫酸亚铁铵[（NH4）2Fe(SO4)2]标准溶液滴定，试亚铁灵作指示剂，反应为Cr2O7^2- 6Fe^2 14H^ =2Cr^3 6Fe^3 7H2O。同时做空白实验，由水样及空白所消耗的硫酸亚铁铵的量，计算出化学需氧量。     

环境水样中的COD快速测定方法研究

提出了一种快速测定水体中COD的新方法，此方法的准确度和再现性与标准K2Cr2O7法一致，且不使用汞盐和硝酸银。     

过硫酸盐对COD测定的干扰及消除研究

待测水样中若残留过硫酸盐会对COD的测定产生干扰。考察了K2S2O8对COD测定的干扰情况,分析干扰原因,并提出相应的消除干扰措施。研究表明,残留的K2S2O8具有一定的还原性从而使COD测定值高于实际值,其浓度与COD之间呈现显著的线性关系,1 mg K2S2O8对COD变化值的贡献约为0.029 79 mg。在COD标准溶液体系中,ΔCOD1(COD测定值与原水实际COD的差值)和线性方程计算的ΔCOD2(K2S2O8对COD的贡献值)的差值为原水实际COD的0.88%~1.99%;在经生化处理后的垃圾渗滤液体系中,ΔCOD1与ΔCOD2的差值为原水实际COD的1.23%~7.18%。该线性方程较好地反映了实际水样的COD,借此可消除残留K2S2O8对COD测定的干扰。     

无汞、无银国标COD测定法的改进

改进了国标COD的测定方法。取水样10.00 mL,加人10.0 mL K2Cr2O7标准溶液、10.0 mL浓H2SO4、2.0mL浓H3PO4和0.1 g MnSO4,以代替Ag2SO4作催化剂和HgSO4作Cl-的掩蔽剂。试样用恒温电热干燥箱加热至190℃,维持18~42 min(视水样中污染物的含量及性质而定)。将实验得到的COD值与国标法测得的COD值相比较,准确度和精密度全都在允许范围内。筛选了对高、中、低浓度COD消解的最佳时间和温度,为COD无汞、无银快速测定提供了实验依据。     

马丁仪微量测定醋酸发酵液的酒精度

研究了一种能够微量测定醋酸发酵液中残留酒精度的方法.采用马丁仪蒸馏得到发酵液中酒精,添加K2Cr2O7将其快速氧化,以Na2S2O3滴定未反应的重铬酸钾,计算确定发酵液中微量残留酒精浓度.该方法所需样品量少、耗时短、精密度高,回收率为93.78%～97.66% ,变异系数为1.75%,可以即时反映醋酸发酵过程中酒精的利用状况.     

黑生料中Fe2O3的快速测定

黑生料中 Fe2O3的测定目前多数仍采用金属铝还原-重铬酸钾滴定法.此方法是先用浓 H3PO4溶样,加 KMnO4来破坏有机物,再用金属铝还原 Fe3+为 Fe2+,最后使用 K2Cr2O7标准滴定溶液来进行滴定.该法虽然快速简便,但存在以下问题:     

铬酸钾电解-结晶制备重铬酸钾的工艺

利用阳离子膜,以K2CrO4电解结晶制备K2Cr2O7,考察了电流密度、温度、阴极液KOH浓度、阳极液K2CrO4浓度等因素对转化率、电流效率和直流能耗的影响;研究了K2Cr2O7不同浓度、不同转化率下的结晶纯度和收率及搅拌速率、降温速率和晶种加入量等对晶体粒度分布和形貌的影响. 结果表明,最佳电解工艺条件为：电流密度0.2 A/cm2,电解温度80℃,阴极液KOH浓度50 g/L,阳极液K2CrO4浓度400 g/L. K2Cr2O7转化率大于90%时,结晶纯度不低于99.8%. 优化的结晶条件为：溶液初始K2Cr2O7浓度500 g/L,搅拌速率300 r/min,降温速率0.5℃/min,不添加晶种. 所得产品符合GB 28657-2012要求.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。