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铌、钽作为稀有贵金属,因其优良的物理性质和稳定的化学性质,在高精尖器械及军事装备领域被广泛应用。我国铌钽资源丰富,多为共伴生矿床,与多种金属矿物共存,具有较高的综合利用价值。针对铌钽精矿中铀、钍及稀土资源分离及回收问题,采用HF-H2SO4混酸法优先提取铌、钽,同时将铀、钍及稀土富集于渣中。本研究应用单因素试验法研究了铌、钽的浸出规律,并讨论了过程机理及其动力学。结果表明,使用高浓度HF,提高HF、H2SO4用量有利于铌、钽的浸出,减小矿石粒径、提高温度和延长浸出时间均能提高铌、钽浸出率。获得的最优浸出参数如下:HF浓度40wt%、HF用量1120 g/kg、H2SO4用量392 g/kg、平均粒径-25μm (75%)、浸出温度80℃、浸出时间4 h。此条件下铌浸出率大于98%,钽浸出率大于97%,铀、钍及稀土保留在渣中,渣中富集率达3.0~4.2。动力学研究表明,铌、钽的浸出过程符合收缩核模型,并属于混合控制类型,铌、钽的表观活化能分别为34.00和3... 相似文献
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研究了铬铁矿加压碱浸氧化反应的动力学过程,考察了铬铁矿粒度、搅拌、碱矿质量比和反应温度等对铬浸出率的影响.结果表明,反应温度250℃、碱浓度60%(ω)、氧分压3.2MPa、铬铁矿粒度小于50m、搅拌转速650r/min、碱矿质量比4.0:1、反应时间240min的条件下,铬铁矿中铬的浸出率达98%以上,且随铬铁矿粒径减小、搅拌转速增加、碱矿质量比增加和反应温度升高而提高.反应产物为MgFe2O4和Mg(OH)2,浸出时呈固态包裹在未反应颗粒外层.宏观动力学研究结果表明,铬铁矿加压碱浸氧化反应过程受反应物在固体产物层中的扩散控制,可用方程1-2/3X-(1-X)2/3=kt描述,该反应的表观活化能E=54.5kJ/mol,指前因子A=328.4min-1. 相似文献
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辽宁某钒钛磁铁矿精矿在初始硫酸浓度为2.5 mol/L、氢氟酸浓度为2.5 mol/L、浸出温度为90℃、液固比为5、浸出时间为2 h、搅拌速率控制在100~200 r/min的条件下,钒的浸出率高达95.68%。试验主要考查了温度与浸出动力学的关系,主要研究内容包括:温度对钒浸出率的影响,通过试验数据处理及拟合分析求出整个浸出反应的表观活化能E=45.20 kJ/mol和反应速率动力学方程1-(1-μ)^(1/3)=26.31 e^(-45200/RT),明确钒浸出过程中反应速率的控制步骤。最终建立了钒的浸出体系动力学模型,为直接酸浸提钒奠定了理论基础。 相似文献
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FeCl3-HCl-C2Cl4体系浸出硫化锌矿的动力学研究 总被引:2,自引:0,他引:2
针对FeCl3-HCl-C2Cl4体系浸出硫化锌精矿过程,建立了以固体产物层扩散控制和混合扩散控制浸出的核收缩动力学模型。动力学研究和浸出过程矿粒表面的SEM分析结果表明,在相同的搅拌强度下,FeCl3-HCl体系符合固体产物层扩散控制的核收缩过程,四氯乙烯能有效地溶解矿粒表面形成的固体硫层,提高固体产物层扩散控制的速度,并且随四氯乙烯加入量的增大;对于FeCl3-HCl-C2Cl4体系则由固体产物层扩散控制变为混合扩散控制的的核收缩过程,显著地提高了浸出速率。 相似文献
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《过程工程学报》2015,(6)
针对难溶性钾岩的利用问题,研究了富钾板岩-脱硫石膏-碳酸钙体系焙烧产物中钾盐的回收及其浸出动力学.结果表明,焙烧产物主要是Ca_2SiO_4,CaO,K_2SO_4,Ca_3Al_2O_6等,其中K_2SO_4可通过水浸分离提取,在液固比2 m L/g的条件下搅拌浸出,浸出平衡时的钾离子浓度为14.98 g/L,浸出液蒸干结晶物K_2SO_4含量为91.28%.提高温度(T)、增大搅拌速率(r)和减小焙烧产物粒度(d)可提高浸出速率,水浸出过程符合扩散控制的溶解过程模型,通过多元线性回归得到钾盐浸出动力学方程为dc/dt=(9.567′10~(-3)T-1.699′10~(-3)d+7.561′10~(-4)r-2.668)(0.0722-c). 相似文献
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It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples. 相似文献
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J. R. Aldrich S. P. Carroll W. R. Lusby M. J. Thompson J. P. Kochansky R. M. Waters 《Journal of chemical ecology》1990,16(1):199-210
Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA. 相似文献
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M. S. J. Simmonds W. M. Blaney F. Delle Monache M. Marquina Mac-Quhae G. B. Marini Bettolo 《Journal of chemical ecology》1985,11(12):1593-1599
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. 相似文献
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Cheng-Le Zhao Shane Porzio Alan Smith Haiyan Ge H. T. Davis L. E. Scriven 《Journal of Coatings Technology and Research》2006,3(2):109-115
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. 相似文献
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2008~2009年世界塑料工业进展 总被引:4,自引:1,他引:3
中蓝晨光化工研究院有限公司《塑料工业》编辑部 《塑料工业》2010,38(3)
收集了2008年7月~2009年6月世界塑料工业的相关资料,介绍了2008~2009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、环氧树脂、不饱和聚酯树脂)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。 相似文献
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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. 相似文献
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ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究 总被引:15,自引:0,他引:15
建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。 相似文献