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1.
Low‐Temperature CO Oxidation over a Ternary Oxide Catalyst with High Resistance to Hydrocarbon Inhibition
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Dr. Andrew J. Binder Dr. Todd J. Toops Dr. Raymond R. Unocic Dr. James E. Parks II Prof. Sheng Dai 《Angewandte Chemie (International ed. in English)》2015,54(45):13263-13267
Platinum group metal (PGM) catalysts are the current standard for control of pollutants in automotive exhaust streams. Aside from their high cost, PGM catalysts struggle with CO oxidation at low temperatures (<200 °C) due to inhibition by hydrocarbons in exhaust streams. Here we present a ternary mixed oxide catalyst composed of copper oxide, cobalt oxide, and ceria (dubbed CCC) that outperforms synthesized and commercial PGM catalysts for CO oxidation in simulated exhaust streams while showing no signs of inhibition by propene. Diffuse reflectance IR (DRIFTS) and light‐off data both indicate low interaction between propene and the CO oxidation active site on this catalyst, and a separation of adsorption sites is proposed as the cause of this inhibition resistance. This catalyst shows great potential as a low‐cost component for low temperature exhaust streams that are expected to be a characteristic of future automotive systems. 相似文献
2.
O. P. Bansal 《Journal of Chemical Sciences》1983,92(6):589-596
Ion exchange equilibria of bivalent transition metal ions have been studied at 20, 30 and 45°C on illite surface. The exchange
isotherms and free energy changes indicate a higher preference of the illite surface for the metal ions. Cd2+ and Mn2+ ions were preferred throughout the entire range while reversal of behaviour occurred during Cu2+, Zn2+ and Co2+ ions exchange on the illite surface. Enthalpy changes suggested a stronger preference of transition metal ions for the illite
surface. Entropy changes indicated an increase in the order of system. The surface phase coefficients of the cations showed
that with increasing metal ion saturationf
m continuously increases whilef
Na decreases. The excess thermodynamic functions snowed that the exchange reactions were non-ideal. 相似文献
3.
The removal of heavy metal cations by natural zeolites 总被引:4,自引:0,他引:4
In this study, the adsorption behavior of natural (clinoptilolite) zeolites with respect to Co2+, Cu2+, Zn2+, and Mn2+ has been studied in order to consider its application to purity metal finishing wastewaters. The batch method has been employed, using metal concentrations in solution ranging from 100 to 400 mg/l. The percentage adsorption and distribution coefficients (Kd) were determined for the adsorption system as a function of sorbate concentration. In the ion exchange evaluation part of the study, it is determined that in every concentration range, adsorption ratios of clinoptilolite metal cations match to Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich (DKR) adsorption isotherm data, adding to that every cation exchange capacity metals has been calculated. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the selectivity sequence can be given as Co2+ > Cu2+ > Zn2+ > Mn2+. These results show that natural zeolites hold great potential to remove cationic heavy metal species from industrial wastewater. 相似文献
4.
Removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions by adsorption onto natural bentonite 总被引:1,自引:0,他引:1
In this study, the removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions using the adsorption process onto natural
bentonite has been investigated as a function of initial metal concentration, pH and temperature. In order to find out the
effect of temperature on adsorption, the experiments were conducted at 20, 50, 75 and 90 °C. For all the metal cations studied,
the maximum adsorption was observed at 20 °C. The batch method has been employed using initial metal concentrations in solution
ranging from 15 to 70 mg L−1 at pH 3.0, 5.0, 7.0 and 9.0. A flame atomic absorption spectrometer was used for measuring the heavy metal concentrations
before and after adsorption. The percentage adsorption and distribution coefficients (K
d) were determined for the adsorption system as a function of adsorbate concentration. In the ion exchange evaluation part
of the study, it is determined that in every concentration range, adsorption ratios of bentonitic clay-heavy metal cations
match to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data, adding to that every cation
exchange capacity of metals has been calculated. It is shown that the bentonite is sensitive to pH changes, so that the amounts
of heavy metal cations adsorbed increase as pH increase in adsorbent-adsorbate system. It is evident that the adsorption phenomena
depend on the surface charge density of adsorbent and hydrated ion diameter depending upon the solution pH. According to the
adsorption equilibrium studies, the selectivity order can be given as Zn2+>Cu2+>Co2+. These results show that bentonitic clay hold great potential to remove the relevant heavy metal cations from industrial
wastewater. Also, from the results of the thermodynamic analysis, standard free energy ΔG
0, standard enthalpy ΔH
0 and standard entropy ΔS
0 of the adsorption process were calculated. 相似文献
5.
Sorption properties of olive husk were investigated under equilibrium (batch tests) and dynamic (column tests) conditions
in order to assess the possibility of using such a waste material for removing heavy metals from aqueous streams. Husk samples
were contacted, at 25°C, with aqueous solutions of nitric salts of Pb, Cd, Cu, and Zn. Sorption isotherms obtained from equilibrium
data were fitted and interpreted by the Freundlich model. Metals-saturated husk samples resulting from column tests were air-dried
and incinerated to simulate combustion in order to assess the fate of sorbed metals. The results demonstrated that, under
both equilibrium and dynamic conditions, metal sorption capacity of the husk was in the sequence Pb>Cd>Cu>Zn. For all the
metals, calculated Freundlich constants decreased by increasing initial metal concentration or decreasing solution pH. In
dynamic tests, a significant reduction of sorption capacity was recorded (except for copper) when a metal was fed simultaneously
to the others: Pb (77%); Cd (93%); Zn (68%). Combustion tests carried out on metals-saturated husk samples showed that the
average losses of lead and cadmium, as volatile species, were always three to four times greater than the losses of copper
and zinc, in both single-metal- and multimetal-saturated samples. 相似文献
6.
《Journal of membrane science》1986,26(3):303-312
This is the third paper in which we describe the transport of uranium ions through liquid membranes. The subject of this paper is the use of liquid membranes to separate uranium from other metals that are present in hydrometallurgical leach solutions derived from uranium ores. It is demonstrated that liquid membranes can cleanly separate uranium from vanadium. The separation of uranium and molybdenum is also investigated. Although this separation is not as clean as that of uranium and vanadium, the results indicate that further refinement of operating conditions of the liquid membrane could lead to substantial improvement. Based on the potential of the membranes to separate the various metal ions, several process schemes are suggested that could be used to recover uranium from hydrometallurgical leach solutions 相似文献
7.
8.
J. L. Gascón M. Rodríguez J. A. Suárez Del Rey 《Journal of Radioanalytical and Nuclear Chemistry》1996,207(1):63-69
The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates. 相似文献
9.
10.
The use of a closed-loop on-line enrichment procedure in combination with an ICP plasma emission spectrometer has been developed for the analysis of trace metal ions, such as Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The procedure utilizes a preconcentration column filled with an anion exchange resin and 8-hydroxy-7-iodoquinoline-5-sulphonic acid is added to the sample prior to preconcentration. Details on the optimization of pretreatment and instrumental conditions are described. Results obtained for the analysis of river water and antarctic seawater are reported.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria 相似文献
11.
The fate of main heavy metals in municipal sewage sludge (As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, and Zn) was investigated using
a fluidized-bed reactor. The behaviour of metals in the incinerator was explored by comparing metal contents in the two main
ash streams: bottom (in-bed) ash and ash separated by a cyclone (cyclone-catch ash). All metals showed enrichment in the cyclone
ash. The ash originating from sewage sludge is thermally quite stable consisting of quartz, hematite, spar(s), mica(s), apatite,
and anhydrite. It does not soften nor becomes sticky and does not tend to agglomerate at temperatures up to 950°C. 相似文献
12.
13.
Waseem Ahmad Shikha Sharma 《International journal of environmental analytical chemistry》2013,93(15):1604-1614
ABSTRACTContamination of groundwater by heavy metal is one of the most emerging and serious environmental problems. There are so many methods which are available to overcome these problems. Among various available methods, hybrid organic–inorganic ion exchange resin has become more popular due to certain advantages over other available conventional methods; hence, in the present proposed work, we synthesised a hybrid organic–inorganic composite material polyacrylamide zirconium (IV) iodosulphosalicylate by using the sol-gel technique. Synthesised resin was characterised by various methods like Infrared spectroscopy and Thermogravimetric analysis-Differential thermal analysis. Various samples of this ion exchange resin are prepared by changing the condition of synthesis, i.e. concentration of acrylamide to rationalise the ion exchange capacity of the synthesise hybrid organic–inorganic ion exchange resins. A mixture of 0.1 M potassium iodate, 0.1 M sulphosalicylic acid and 0.1 M acrylamide was added dropwise to 0.4 M zirconium oxychloride accompanied by constant stirring for 8 h using magnetic stirrer at 70°C to yield polyacrylamide zirconium (IV) iodosulphosalicylate with maximum ion exchange capacity. Ion exchange capacity of synthesised resin was determined by column method and the maximum ion exchange capacity was found for Pb(II). Determination of kd values shows that the resin was highly selective for Pb (II).The selectivity for Pb was also evaluated by using certain binary mixture separation such as Ni (II)-Pb(II), Cu(II)-Pb(II), Cd(II)-Pb(II), Sr(II)-Pb(II), Ba(II)-Pb(II),Zn(II)-Pb(II) and Mg(II)-Pb(II). 相似文献
14.
In the developing countries where the cost is often a decisive factor, extensive studies were undertaken to test the most
effective factors on the preparation, optimization and validation of the magnetic particles (or, more accurately, magnetizable
particles) for removal of heavy metals from wastewaters. The objective of the proposed work was focused to provide promising
solid-phase materials, which, are relatively in expensive and combine high surface capacity with fast efficient treatment.
Four various metal oxides including hydrous ferric oxide (HFO), hydrous stannic oxide (HSO) and mixed ferric/stannic oxide
(HMO), were prepared by precipitation with ammonia from metal chloride solutions. Two mixed oxides were prepared with different
Sn/Fe ratios of 50% and 20%. Optimal conditions for the activation of these particles and the subsequent mixing of various
metals oxides are tested together with the utility of the method to get a new composite material with developed chemical characteristics
over their individual metal oxides. Factors affecting the sorption behavior of the prepared samples in basic and acid media
were elucidated. The magnetic treatment procedure using the mixed oxide (50%) enables the equilibration step to be carried
out rapidly mainly due to ferric oxide during the magnetization process and efficiently due to high capacity of the stannic
oxide. A key factor in achieving very high uptake percentage is the reduction of non-specific binding of various heavy metals
to the solid phase support. This is usually achieved by increasing the ion exchange capability, in addition to their adsorption
process. 相似文献
15.
J. Liang J. J. Schoenau 《International journal of environmental analytical chemistry》2013,93(2-4):265-275
Abstract Ion exchange resins in contact with soil can act as a sink for metal cations, thereby simulate the action of plant roots. Ion exchange resins in membrane form offer additional advantages in ease of use and handling. A procedure was developed to assess the bioavailability of four heavy metals Cd, Cr, Ni and Pb via direct in soil burial. A growth chamber experiment with three representative crops (oats, radish and lettuce) was set up to determine the phytotoxic levels of the four heavy metals. The critical levels varied widely from crop to crop, and soil to soil. Lettuce was most sensitive to high concentration of metals. The toxic effects are more pronounced on sandier textured soils. 相似文献
16.
S. S. Rayalu A. K. Bansiwal S. U. Meshram Nitin Labhsetwar Sukumar Devotta 《Catalysis Surveys from Asia》2006,10(2):74-88
Fly ash is combustion residue from burning of pulverised coal in electric utility generating stations. The annual production of fly ash in India is around 100 MTPA and is responsible for several environmental hazards, which is quite well documented. There are stringent norms for its land disposal and hence utilisation of fly ash is imperative. Fly ash has more than 85% of SiO2 and Al2O3 content and is therefore a tailor made raw material for production of zeolite. An innovative process has been developed for synthesis of zeolites using fly ash as a substitute for conventional raw materials viz. sodium silicate and aluminate. The process consists of three major steps viz. fusion of caustic soda and fly ash for optimal extraction of silicate and aluminate, aging step which provides time for formation of nuclei and hydrothermal crystallization resulting in activation of nuclei into well defined crystals. Low temperature operation, simplicity of process and optimal recycling of unused reactants and process water are special features of these processes. Zeolites have high internal and external surface areas and also exhibit high exchange capacities, which makes them versatile materials for targeting wide range of pollutants, ranging from cationic to anionic and hydrophilic to hydrophobic molecules. The major uses of zeolites are in adsorption, ion exchange and as catalysts. The use of zeolites in environmental remediation is restricted due to procurement problem and prohibitive cost, which can be overcome by using low cost fly ash based zeolites (FAZs). The synthesis of FAZ-A and FAZ-Y and their modifications either by transition metal incorporation or by surfactant treatment for various environmental applications in air, water and soil remediation are addressed in this review. 相似文献
17.
Imaging the Atomic Position of Light Cations in a Porous Network and the Europium(III) Ion Exchange Capability by Aberration‐Corrected Electron Microscopy
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Dr. Alvaro Mayoral Reece M. Hall Roksana Jackowska Dr. Jennifer E. Readman 《Angewandte Chemie (International ed. in English)》2016,55(52):16127-16131
In the present work, ETS‐10 microporous titanosilicate has been synthesized and its structure characterized by means of powder XRD and aberration corrected scanning transmission electron microscopy (Cs‐corrected STEM). For the first time, sodium ions have been imaged sitting inside the 7‐membered rings. The ion‐exchange capability has been tested by the inclusion of rare earth metals (Eu, Tb and Gd) to produce a luminescent material which has been studied by atomic‐resolution Cs‐corrected STEM. The data produced has allowed unambiguous imaging of light atoms in a microporous framework as well as determining the cationic metal positions for the first time, providing evidence of the importance of advanced electron microscopy methods for the study of the local environment of metals within zeolitic supports providing unique information of both systems (guest and support) at the same time. 相似文献
18.
《Comptes Rendus Chimie》2015,18(12):1370-1384
Coordination clusters of 3d metals continue to attract the intense interest of the scientists from the synthetic inorganic chemistry, bioinorganic chemistry and molecular magnetism communities. We review here the synthetic strategies employed in a continuous effort to obtain new and potentially magnetically interesting dinuclear molecules based on iron, manganese, chromium, and cobalt metal ions. The reported systems are pure homometallic 3d materials. We have focused on describing aspects of the synthesis, the crystal structures and the magnetic behaviour of these coordination compounds with low nuclearity. A deep solid-state and magnetic characterization of these systems has allowed us to gain evidence regarding the role played by weak exchange interactions and geometrical factors on the slow dynamics of the magnetization. In addition, the analysis through ab initio calculations has provided a valuable insight into the influence of organic periphery, bridging ligands, and remote substituents on the exchange coupling constant (J). In the case of a dinuclear complex based on manganese, the largest ferromagnetic interaction between two MnIII has been observed (J = 19.7 cm−1). 相似文献
19.
Pore‐Environment Engineering with Multiple Metal Sites in Rare‐Earth Porphyrinic Metal–Organic Frameworks
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Liangliang Zhang Shuai Yuan Liang Feng Bingbing Guo Jun‐Sheng Qin Ben Xu Christina Lollar Prof. Dr. Daofeng Sun Prof. Dr. Hong‐Cai Zhou 《Angewandte Chemie (International ed. in English)》2018,57(18):5095-5099
Multi‐component metal–organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative catalysis, and biomimetics. A series of multi‐component MOFs, namely PCN‐900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare‐earth hexanuclear clusters (RE6) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm2 g?1) and unlimited tunability by modification of metal nodes and/or linker components. Post‐synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis. 相似文献
20.
Dmitry Kirsanov Alisa Rudnitskaya Andrey Legin Vasily Babain 《Journal of Radioanalytical and Nuclear Chemistry》2017,312(3):461-470
Chemometrics can be very useful for the classical field of UV–Vis determination of metals in aqueous solutions. A conventional approach consisting of using selective bands in a univariate mode is often not applicable to the real-world samples from e.g. hydrometallurgical processes, because of overlapping signals, light scattering on foreign particles, gas bubble formation, etc. And this is where chemometrics can do a good job. This paper overviews certain contributions to the field of multivariate data processing of UV–Vis spectra for seemingly simple case of metal detection in aqueous solutions. Special attention is given to applications in nuclear technology field. 相似文献