天然气脱汞吸附剂的制备及其性能评价

天然气中含汞会对天然气的开发及使用带来危害，实验采用固定床吸附法脱除天然气中的汞。实验以Al₂O₃和活性炭复合颗粒为载体，通过浸渍法负载S、CuS和CuS _x 多组分活性物，制备了天然气脱汞吸附剂，考察了制备工艺条件的影响。采用X射线衍射检测（XRD）与扫描电镜（SEM）对活性物负载情况进行了表征。结果表明，在载体上成功负载了CuS和S，其中CuS质量分数为12.80%，总S质量分数为8.32%。以含汞空气模拟含汞天然气，考察了进气口汞含量、停留时间对脱汞吸附剂脱汞效果的影响。结果表明，脱汞剂处理汞含量为300μg/m³的天然气，停留时间为1s时，出口汞含量为24.99μg/m³，已达到工业天然气要求。当停留时间为2s、进气口汞含量达到600μg/m³时，经脱汞剂脱汞后，出口汞含量为18.92μg/m³，达到小于28μg/m³要求。脱汞吸附剂的汞容量达到6.36%。     

TiAl ALLOYS PREPARED BY THERMAL EXTRUSION OF ELEMENTAL POWDER MIXTURES

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Gold leaching with elemental sulfur in alkaline solutions under oxygen pressure

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｙａｎｉｄａｔｉｏｎｐｒｏｃｅｓｓ ,ｃｈａｒａｃｔｅｒｉｚｅｄｂｙｅｆｆｅｃｔｉｖｅｎｅｓｓａｎｄｌｏｗｏｐｅｒａｔｉｎｇｃｏｓｔ,ａｓａｃｏｎｖｅｎｔｉｏｎａｌｔｅｃｈｎｏｌｏｇｙｆｏｒｇｏｌｄｅｘｔｒａｃｔｉｏｎｆｒｏｍｏｒｅｓ ,ｈａｓｂｅｅｎｕｓｅｄｉｎｉｎｄｕｓｔｒｙｆｏｒｏｖｅｒ 10 0ｙｅａｒｓ .Ｈｏｗｅｖｅｒｔｈｅｃｙａｎｉｄｅｉｓａｈｉｇｈｌｙｔｏｘｉｃｃｈｅｍｉｃａｌ,ａｎｄｃｏｍｍｅｒｃｉａｌｃｙａｎｉｄａｔｉｏｎｐｒｏｃｅｓｓｉｓｌｉｍｉｔｅｄｉｎｔ…     

Electrochemical studies of octadecanethiol and octanethiol films on variable surface area mercury sessile drops

Octadecanethiol (ODT) and octanethiol (OT) films at the mercury-electrolyte interface are examined using cyclic voltammetry and differential capacitance measurements at a single frequency. A mercury flow-system is used to alter the volume, and therefore, the surface area and surface pressure of the mercury electrode. Manipulation of the mercury electrode's volume enables the introduction and removal of defects in the insulating thiol films. OT and ODT film behavior are contrasted under conditions of expansion and contraction. ODT forms extremely impermeable layers that allow 1000 time less redox probe current than seen on uncoated drops. Expansion of the mercury electrode to increase the electrode surface area produces defects and pinholes in the thiol film. These defects are almost completely removed when the drop is compressed back to its initial surface area. OT also forms insulating films on mercury sessile drops, however these films contain more defects than ODT films. While expansion of an OT-coated mercury drop increases redox probe current, recompression of the drop does not return the film to its initial condition. Pinholes and defects in the OT and ODT films can also be produced by cycling to negative potentials, which produce abrupt stripping peaks.     

白鹤滩大坝混凝土干燥养护强度与微观结构北大核心CSCD

白鹤滩大坝的建设使用了低热水泥混凝土,为了解它在干燥养护下的特性,本研究探讨了低热水泥混凝土干燥养护下的抗压强度与劈裂抗拉强度发展规律,并通过扫描电镜和压汞法分析微观形貌与孔结构。结果表明:相比标准养护,在干燥养护下低热水泥混凝土28 d抗压强度损失33.3%,劈裂抗拉强度损失31.6%,且水化产物较少、混凝土孔隙率和孔体积会明显增大、孔隙总面积减小,孔径分布以100~1000 nm的大孔为主。本研究表明干燥养护不利于低热水泥混凝土微观结构与强度发展,可为大坝混凝土的养护与强度提供依据。     

Assessment of fish mercury levels in the upper St. Lawrence River,Canada

The stretch of the St. Lawrence River near Cornwall, Ontario, Canada, between the Moses–Saunders power dam to the eastern outlet of Lake St. Francis in Québec, is currently listed as an Area of Concern (AOC), and has restrictive fish consumption advisories in place, largely due to high mercury levels. This study examined long-term temporal trends of mercury concentrations in northern pike, smallmouth bass, walleye and yellow perch from the St. Lawrence River, including the Cornwall AOC. In addition, differences in fish mercury concentrations among river sections were compared for each species using historical (1975–1979) and recent (2000–2011) data. Statistically significant declines in mercury concentrations were observed in all river sections for yellow perch (~ 40%), as well as in northern pike and walleye in at least one river section. For the river section encompassing the AOC, recent mercury concentrations are 33–59% lower than historical mercury concentrations for all four species. Further, a comparison of recent mercury concentrations between the AOC river section and other Ontario lakes/rivers suggests that AOC mercury values are within the 75th percentile of values for other Ontario water bodies in three of the four species considered. However, current fish mercury values for the AOC river section remain higher than one or more upstream river sections. These results indicate that recovery is still ongoing in this AOC.     

Influence of cement type on transport properties and chemical degradation: Application to nuclear waste storage

The geological repository of nuclear waste in concrete containers is a possible storage method explored by ANDRA (Agence Nationale pour la gestion des Déchets RadioActifs). The concrete must display a high confinement capacity for long periods, characterized by low transport properties and by the acido-basic buffer of hydrated cement. During service life, these properties can be endangered by chemical attack of underground water. The cement type has an important influence on the concrete's performances. Then, it is essential to establish appropriate mixtures with accurate components. In this work an ordinary Portland cement and a fly ash and blast furnace slag blended cement are compared. To determine confinement capacities, transfer properties and mortars microstructure were investigated. To predict the long term behaviour, an ammonium nitrate test has been developed to enhance decalcification and to accelerate hydrolysis of cementitious materials. Measurement of degraded depth with time regarding calcium content was carried out. Impact of decalcification on transport properties was evaluated. Fly ash and blast furnace slag provide better properties for native mortars, and more particularly diffusion properties, but not as much as necessary to limit leaching in degraded material by chemical attack.     

A Novel Instrument for the Measurement of the Thermal Conductivity of Molten Metals. Part II: Measurements

New measurements of the thermal conductivity of molten mercury, gallium, tin, and indium are reported up to 750 K. The measurements are performed in a novel transient hot-wire instrument described elsewhere. The present experimental technique overcomes problems of convection, and it is shown that it operates in an absolute way in accord with a theoretical model. The uncertainty of the thermal conductivity results is estimated to be ± 2%, which is superior to that achieved in most earlier work. The low uncertainty of the present experimental results has allowed us to test the only significant theory for the thermal conductivity of molten metals, which relates this property to the electrical conductivity. The pattern of results among the four metals indicates that further theoretical developments would be warranted.     

1-吡啶-3-[4-(苯基偶氮)苯基]-三氮烯与汞的显色反应及其应用

在Triton X-100存在下的pH 10的Na2B4O7-NaOH缓冲介质中,研究了1-吡淀-3-[4-(苯基偶氮)苯基]-三氮烯(PYPAPT)与汞离子(Hg2 )的显色反应,建立了微量汞的测定方法。Hg2 与PYPAPT形成1∶2的红色络合物,络合物最大吸收波长位于518 nm,表观摩尔吸光系数为1.42×105L.mol-1.cm-1,Hg2 质量浓度在0~0.64 mg/L范围内符合比尔定律。方法用于铅锌矿样中微量汞的测定,RSD小于2.6%,测定结果与AAS法相符。