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排序方式: 共有327条查询结果,搜索用时 62 毫秒
11.
《Journal of Nuclear Science and Technology》2013,50(8):735-743
Solvent extraction is the major unit operation employed in spent nuclear fuel reprocessing. The operation yields three streams; fission product waste, uranium product and plutonium product. Ion exchange is primarily used in reprocessing as a tail-end method to concentrate and isolate the plutonium product stream. This review will describe the details of plutonium recovery and purification by both cation- and anion-exchange processing. A brief overview of miscellaneous uses of ion-exchange employed in reprocessing will also be given. 相似文献
12.
The synthesis of higher alcohols, obtained from CO hydrogenation over transition metals, is an alternative for the production of chemical commodities and less pollutant renewable fuels nowadays. In this work, the influence of different alkali metals (Li, Na, K, Cs) over the formation of active phases of supported catalysts, based on cobalt and copper, as well as the performance of these solids in the reaction of CO hydrogenation under a 50 bar pressure were studied. The solids were prepared by continuous coprecipitation of sodium carbonate with metal nitrate solutions (Al–Co, Al–Cu or Al–Co–Cu) promoted with the alkali metals with dry impregnation. Characterization studies by atomic absorption spectrophotometry, BET, XPS and also the results of catalytic tests show that physico-chemical properties of the obtained catalyst are similar to those of the industrial catalyst used as reference (I). 相似文献
13.
14.
Al-Mn-pillared montmoriUonite ( AMPM ) was prepared by using the artificial Na-montmoril-lonite from the Qingfengshan bentonite mine as starting materials mixed with Al-Mn pillaring solutions at different Al / Mn molar ratios ( R ). The basal spacing and specific surface area of the materials were increased significantly compared with untreated c/ays. When R=0.5, the d(001) value and specific surface area of pillared montmoril-lonite were 1.8987 nm and 146.01 m^2 g^-1, respectively. The thermal stability was determined using calcined tests,X-ray diffraction( XRD ) analysis, thermal gravimetry and differential thermal analysis( TG- DTA ). The formed at initial R = 0. 5 exhibited a high stability, the basal interlayer spacing was stabilized at 1. 7859 nm after calcined for 2 h at 300℃. The adsorption behavior of the materials wets studied by adsorption experi-ments. The results show the AMPM and calcined AI-Mn-pilloTed montmoriUonite (CAMPM) exhibit a strong ca-pacity of adsorbing the Zn ( Ⅱ ) in aqueous solution at pH 10.0. 相似文献
15.
Abstract The calcium (Ca), sodium (Na), and potassium (K) contents of blue gum, maritime pine, and cork increased after these lignocellulosics were stirred with the filtrate of a cement suspension or a solution of calcium hydroxide. The adsorbed cations could be released easily by treatment with an acidic solution. It is suggested that those raw materials, and lignocellulosics in general, act as cation exchange substrates when they are mixed with cement and water to make wood–cement composites. The implications that such phenomena may have on cement hardening reactions, and how they could hinder them are discussed. The possibility that the phenomenon is related to well‐known compatibility problems that many woods present when manufacturing wood–cement composites is discussed. 相似文献
16.
Jingyu Zhang Zhiping SongLizhi Zhan Jing TangHui Zhan Yunhong ZhouCaimao Zhan 《Journal of power sources》2009
Novel thioether compound poly(ethene-1,1,2,2-tetrathiol) was synthesized, characterized and tested as cathode active material. The polymer was synthesized by facile one-step procedure and its chemical structure was confirmed by FT-IR, FT-Raman, element analysis, and XPS spectral analysis. The polymer had good electrochemical activity as cathode material for rechargeable lithium battery. It showed stable discharge specific capacity about 300 mAh g−1 and discharge voltage above 2 V. The thioether bond was deduced as the functional group. It was proposed that thioether bonds were oxidized to form thioether cations with the help of ether solvent, which offered energy storage. 相似文献
17.
This study examined the spatiotemporal patterns of episodic acidification in 87 weakly buffered streams in Sweden at a monthly sampling frequency during a ten-year study period (1998-2007). Time series of pre-industrial pH (pH0) were reconstructed from the acidification model MetaMAGIC, and the acidification impact was defined by the difference between the pH0 and the contemporary pH (i.e., ΔpH = pH0 − pHt). Acidification episodes were defined as observations for which the pHt was at least 0.4 units lower than average, in combination with a ?pH at least 0.2 units higher than average. Thus, only occasions in which the stream water was both more acidic and more acidified than average were characterized as acidification episodes. For each observed episode, the primary cause was identified from one of the following five possible drivers: dilution, increase in sulfate, nitrate or organic acids, or sea salt deposition. In total, 258 episodes were observed during the study period. The study showed that streams that were acidified during baseflow (ΔpH > 0.4), but not chronically acidic (pH > 5.2), were subjected to regular episodic acidification. Dilution was the single most important cause and the main driver for 58% of the identified episodes. Increases in sulfate concentrations were also relatively common (26% of episodes), whereas increases in nitrate and organic acids as well as sea salt deposition were of minor importance. The total number of dilution-related acidification episodes within a year had a significant (p = 0.005) positive correlation (r = + 0.83) with the average annual precipitation. Occurrences of sulfate episodes were related to droughts during the preceding summers. While the number of streams that are susceptible to episodic acidification will decrease as a consequence of recovery from acidification, the hydrological and meteorological consequences of future climate change may make episodic acidification more common. 相似文献
18.
Polymeric compounds in activated sludge supernatant -- Characterisation and retention mechanisms at a full-scale municipal membrane bioreactor 总被引:3,自引:0,他引:3
Lyko S Al-Halbouni D Wintgens T Janot A Hollender J Dott W Melin T 《Water research》2007,41(17):3894-3902
In this study, for the first time a full-scale membrane bioreactor (MBR) was investigated with focus on organic compounds in activated sludge over a period of approximately 2 years. Soluble extracellular polymeric substances (EPS) in the sludge supernatant and permeate as well as bound EPS extracted from fouled membranes were determined photospectrometrically and revealed a typical composition of three main components in the order metals>humic acids>carbohydrates>proteins. Results showed an important influence on membrane fouling by soluble humic substances and carbohydrates in complexes with metal cations. It was found that Fe(2+) and Fe(3+) play a decisive role in natural organic matter (NOM) complexation and subsequent membrane blockage. The determination of molar mass distribution in supernatant and permeate by size exclusion chromatography (SEC) revealed a significant retention of macromolecular compounds by the porous membranes in the range of 10-50%. 相似文献
19.
《分离科学与技术》2012,47(4):495-504
The objective of this work was to correlate the separation process of the metallic cations (M(II)) by electropermutation (EP) of multications solution with the affinity of ion-exchange materials (IEMs). The obtained results show that the affinity order is similar for all tested IEMs and is as follows: Pb(II)>Cd(II)>Zn(II)>Mg(II). Furthermore, the order of the transfer flux (J) of metallic cations obtained with different tested cation-exchange membranes (CEMs) is identical to that encountered for the affinity order. Further analysis of the results demonstrated that the affinity of IEMs and the transfer flux change in reverse order of hydration ionic radius (r) of metallic cations: rMg(II)>rZn(II)≥rCd(II)>rPb(II). During the EP, the order of metallic cations transfer is as established previously when using different electro-regeneration cations (H+, Na+, NH4+) and different co-ions (NO3?, Cl?, SO42?). However, the extent of the transfer flux as a function of the nature of electro-regeneration cation follows the order: JM(II)(H+)>JM(II)(NH4+)>JM(II)(Na+). The removal rates of metallic cations vary in the range 89?99%. This work shows that the orders of the IEMs affinity and the transfer are mainly determined by the properties of metallic cations such as the hydration ionic radius. Nevertheless, the importance of the fixation and the transfer of metallic cations depend on the IEMs’ nature. 相似文献
20.
S. Rodríguez Mozaz A. García Sotro J. Garrido Segovia C. Ancín Azpilicueta 《Food research international (Ottawa, Ont.)》1999,32(10):244-689
Must has many metallic cations which greatly affect wine fermentation, stability and quality. In this study we investigated the influence of clarification of viura must by static sedimentation studying the concentration of four macroelements (potassium, calcium, magnesium and sodium) and of four oligoelements (iron, copper, zinc and manganese). This treatment eliminated potassium (11%), calcium (25%), and a greater proportion of iron (46%). The evolution of cations during fermentation was similar in the clarified sample and in the control. Both young and stablised wines had similar concentrations of these elements. 相似文献