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Influence of inherent iron and oxygen concentrations on selenite sorption process using bentonite

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Science China Chemistry 2017年第9期60卷 1258-1264页

作者： Jiangang He xueling Qiao Yanlin Shi Yao Li xiaoyu Yang Wanqiang Zhou Chunli Liu Beijing National Laboratory for Molecular Sciences Fundamental Science Laboratory on Radiochemistry&Radiation ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

The oxygen concentration and inherent Fe in bentonite have a significant influence on the Se(IV) sorption process. In this study, the sorption of selenite on natural bentonite was investigated using a batch experiment method, and the distribution coefficient (Kd) values were obtained in the pH range from 2.0 to 10.0 under oxic/anoxic conditions. The Kdvalues always reached a maximum value at a pH of 4 under oxic conditions and at a pH of 8 under anoxic conditions; meanwhile, the Kdvalue under anoxic conditions was larger than the value under oxic conditions, especially in regard to the maximum Kdvalues. The oxygen conditions have a significant influence on the ratio of redox-sensitive Fe2+/Fe3+, which was closely related to the difference in the Kdvalues under both oxic/anoxic conditions. Ferric selenite and green rust could be responsible for the maximum Kdvalues under oxic/anoxic conditions. In the leaching experiments, we found that the Fe2+in bentonite could replace Mg2+and Al3+in the octahedral sheet. Spectroscopy methods, such as Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (xRD) and x-ray absorption spectroscopy (xAS) were used to characterize the surface properties of the samples after reaction. Overall, this study shows that the addition of Fe2+-containing materials into backfill/buffer materials under anoxic condition could enhance the sorption of79Se(IV). © 2017, Science China Press and Springer-Verlag GmbH Germany.

关键词： Bentonite Oxygen Sorption Spectroscopic analysis x ray absorption spectroscopy x ray diffraction

Consolidation mechanism of gold concentrates containing sulfur and carbon during oxygen-enriched air roasting

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International Journal of Minerals,Metallurgy and Materials 2017年第4期24卷 386-392页

作者： Qian Li Fang-zhou Ji Bin xu Jian-jun Hu Yong-bin Yang Tao Jiang School of Minerals Processing and Bioengineering Central South University Changsha 410083 China

Consolidation in calcines is a common problem in the oxygen-enriched air roasting of refractory gold concentrates containing sulfur and carbon when the initial temperature is greater than 600°C. To determine the phases that caused consolidation, gold concentrates were roasted under different conditions and the calcines were mainly detected by x-ray diffraction (xRD). The possible underlying mechanism was then studied through comparisons of the xRD patterns of different calcines. The results indicated that the generation of calcium magnesium silicate, iron-doped calcium aluminosilicate, and calcium aluminate caused the consolidation. Furthermore, an enriched oxygen atmosphere accelerated the oxidation reaction and the emitted heat increased the local temperature in calcines. The local temperature was inferred to have increased to the generation temperature zone of the corresponding liquid phases. Oxidation of the pyrite and decomposition of the dolomite and muscovite mainly occurred at the initial stage of oxygen-enriched air roasting. Calcium was confirmed to be essential to the consolidation process. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

关键词： Calcination Calcium Consolidation Gold Mechanisms Mica Oxygen Silicates Sulfur x ray diffraction

Amine-functionalized low-cost industrial grade multi-walled carbon nanotubes for the capture of carbon dioxide

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Journal of Energy Chemistry 2014年第1期23卷 111-118页

作者： Qing Liu Yao Shi Shudong Zheng Liqi Ning Qing Ye Mengna Tao Yi He Key Laboratory of Biomass Chemical Engineering of Ministry of Education Department of Chemical and Biological Engineering Zhejiang University Department of Earth and Planetary Sciences Washington University in St. Louis Department of Life Sciences Shaoxing University Yuanpei College

Industrial grade multi-walled carbon nanotubes(IG-MWCNTs) are a low-cost substitute for commercially purified multi-walled carbon nanotubes(P-MWCNTs). In this work, IG-MWCNTs were functionalized with tetraethylenepentamine(TEPA) for CO2capture. The TEPA impregnated IG-MWCNTs were characterized with various experimental methods including N2adsorption/desorption isotherms, elemental analysis, x-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Both the adsorption isotherms of IGMWCNTs-n and the isosteric heats of different adsorption capacities were obtained from experiments. TEPA impregnated IG-MWCNTs were also shown to have high CO2adsorption capacity comparable to that of TEPA impregnated P-MWCNTs. The adsorption capacity of IG-MWCNTs based adsorbents was in the range of 2.145 to 3.088 mmol/g, depending on adsorption temperatures. Having the advantages of low-cost and high adsorption capacity, TEPA impregnated IG-MWCNTs seem to be a promising adsorbent for CO2capture from flue gas.

关键词： Adsorbents Adsorption Adsorption isotherms Carbon dioxide process Costs Fourier transform infrared spectroscopy Thermogravimetric analysis x ray diffraction

Highly efficient and stable electrooxidation of methanol and ethanol on 3D Pt catalyst by thermal decomposition of In2O3 nanoshells

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Journal of Energy Chemistry 2017年第1期26卷 193-199页

作者： Yuhang xie Hulin Zhang Guang Yao Saeed Ahmed Khan xiaojing Cui Min Gao Yuan Lin State Key Laboratory of Electronic Thin Film and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054SichuanChina Center for Information in Medicine University of Electronic Science and Technology of ChinaChengdu 610054SichuanChina The First Sub-Institute Nuclear Power Institute of ChinaChengdu 610041SichuanChina

In this paper In2O3nanoshells have been synthesized via a facile hydrothermal approach. The nanoshells can be completely cracked into pony-size nanocubes by annealing, which are then used as a support of Pt catalyst for methanol and ethanol electrocatalytic oxidation. The prepared In2O3and supported Pt catalysts (Pt/In2O3) were characterized by x-ray diffraction (xRD), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (xPS), field effect scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS) were carried out, indicating the excellent catalytic performance for alcohol electrooxidation can be achieved on Pt/In2O3nanocatalysts due to the multiple active sites, high conductivity and a mass of microchannels and micropores for reactant diffusions arising from 3D frame structures compared with that on the Pt/C catalysts. © 2016 Science Press

关键词： Alcohols Catalyst activity Catalysts Chronoamperometry Cyclic voltammetry Decomposition Electrocatalysis Electrochemical impedance spectroscopy Electron microscopy Electrooxidation Energy dispersive spectroscopy Ethanol High resolution transmission electron microscopy Methanol Nanoshells Nanostructured materials Nanostructures Platinum Scanning electron microscopy Transmission electron microscopy x ray diffraction x ray photoelectron spectroscopy x ray spectroscopy

Solvent-free synthesis of alumina supported cobalt catalysts for Fischer–Tropsch synthesis

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Journal of Energy Chemistry 2016年第6期25卷 1001-1007页

作者： Mengnan Lu Nouria Fatah Andrei Y.Khodkov Unité de Catalyse et de Chimie du Solide (UCCS) State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC) School of Environment POPs Research Center Tsinghua University Ecole Nationale Supérieure de Chimie de Lille

A novel mechano-synthesis method has been elaborated in this work for the design of efficient cobalt-based Fischer–Tropsch catalysts. The process aims to reduce the total number of steps involved in the synthesis of solid catalysts and thus to avoid relevant toxic solutions generated during the catalyst preparation. The mechano-synthesis of the Co/Al2O3catalyst was processed in a low-energy vibratory micro mill and high energy planetary ball mill. Porous spherical γ-aluminas (1860 µm and 71 µm mean particle diameter) were used in this work as host compounds. Co3O4(3 µm mean particle diameter) has provided guest particles for mechano-synthesis. The catalysts were characterized by textural (surface area, porosity and particle size) and structural analyses (x-ray diffraction, TPR, SEM-EDx and microprobe). The microprobe images show deposition of Co3O4on the surface of the alumina and indicated no Co3O4diffusion inside the alumina pores. SEM-EDx mapping illustrated that cobalt coating tended to occur on surface of rounded shape of cracked alumina fragments. After milling, the crystallite size of Co3O4decreased to 15 nm from 30 to 50 nm. The TPR profiles indicated very low concentrations of inactive cobalt aluminate mixed compounds which are usually produced during the catalyst preparation by impregnation. In Fischer–Tropsch synthesis, the catalysts prepared using mechano-synthesis methods showed catalytic performance comparable to the catalysts prepared by impregnation. © 2016 Science Press

关键词： Alumina Ball mills Catalysts Cobalt Crystallite size Impregnation Particle size Particle size analysis x ray diffraction

Preparation and catalytic activity of CO-resistant catalyst core-shell Au@Pt/C for methanol oxidation

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Rare Metals 2012年第5期31卷 451-456页

作者： FENG Rongjuan LI Min LIU Jiaxiang College of Materials Science and Engineering Laboratory of Electrochemical Process and Technology for Materials Beijing University of Chemical Technology Beijing 100029 China

Au@Pt core-shell nanoparticles were successfully synthesized by a successive reduction method and then assembled on Vulcan xC-72 carbon surface. Furthermore, its composition, morphology, structure, and activity towards methanol oxidation were characterized by UV-vis spectrometry, transmission electron microscopy (TEM), high-resolution TEM (HRTEM), x-ray diffraction (xRD), x-ray photoelectron spectroscopy (xPS), and cyclic voltammetry (CV). Results reveal that Au@Pt/C catalyst has better activity towards methanol oxidation than the pure platinum prepared under the same conditions. When the atomic ratio of Au to Pt in the prepared Au@Pt/C catalyst is 1:2, this catalyst exhibits best electrocatalytic activity towards methanol oxidation in acidic media, and the peak current density on this catalyst is ~2.0 times higher than that on Pt/C catalyst. The better catalytic activity of Au@Pt/C results from its better resistance to toxic CO than Pt/C because the CO oxidation on Au@Pt/C is 60 mV more negative than the case on Pt/C. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

关键词： Carbon Cobalt Cyclic voltammetry Electrocatalysts Gold Methanol Nanoparticles Oxidation Photoelectrons Platinum Platinum alloys Synthesis (chemical) Transmission electron microscopy x ray diffraction x ray photoelectron spectroscopy

Catalytic performances of Ni/mesoporous SiO_2 catalysts for dry reforming of methane to hydrogen

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Journal of Energy Chemistry 2016年第4期25卷 709-719页

作者： Fei Huang Rui Wang Chao Yang Hafedh Driss Wei Chu Hui Zhang College of Chemistry and Chemical Engineering Southwest Petroleum University Oil & Gas Field Applied Chemistry Key Laboratory of Sichuan Province Drilling & Production Engineering Technology Research Institute CNPC Chuanqing Drilling Engineering Co.Ltd. SABIC Chair in Catalysis King Abudulaziz University Department of Chemical Engineering Sichuan University

Several mesoporous silicas with different morphologies were controllably prepared by sol-gel method with adjustable ratio of dual template, and they were further impregnated with aqueous solution of nickel nitrate, followed by calcination in air. The synthesized silica supports and supported nickel samples were characterized using N2-adsorption/desorption, x-ray diffraction (xRD), H2temperature-programmed reduction (H2-TPR), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and thermo-gravimetric analysis (TGA-DTG) techniques. The Ni nanoparticles supported on shell-like silica are highly dispersed and yielded much narrower nickel particle-size than those on other mesoporous silica. The methane reforming with dioxide carbon reaction results showed that Ni nanoparticles supported on shell-like silica carrier exhibited the better catalytic performance and catalytic stability than those of nickel catalyst supported on other silica carrier. The thermo-gravimetric analysis on used nickel catalysts uncovered that catalyst deactivation depends on the type and nature of the coke deposited. The heterogeneous nature of the deposited coke was observed on nickel nanoparticles supported on spherical and peanut-like silica. Much narrower and lower TGA derivative peak was founded on Ni catalyst supported on the shell-like silica. © 2016 Science Press

关键词： Carbon Catalyst activity Catalyst deactivation Catalysts Catalytic reforming Coke Gravimetric analysis Hydrogen Methane Nanoparticles Nickel Particle size Scanning electron microscopy Silica Sol gel process Sol gels Solutions Thermogravimetric analysis Transmission electron microscopy x ray diffraction

V-doped MgAl_6O_(10):novel luminescence substrate for phosphor-free UV-white LEDs

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Chinese Optics Letters 2012年第2期10卷 65-67页

作者：许鹏夏长泰吴峰李星赛青林周国清徐晓东 Key Laboratory of Materials for High Power Laser Shanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

V-doped MgAl6O10 is grown by the conventional Czochralski method. The crystal structure and the cell parameters are analyzed through x-ray diffraction experiments. The absorption and emission spectra are investigated. Under pumping at 324 nm, the emission spectra of V-doped MgAl6O10 obtain two emission peaks at the wavelengths of 471 and 570 nm. Two emission bands of the spectra combine to produce a spectrum that is perceived as white by the naked eye. Therefore, V-doped MgAl6O10 single crystal can be applied as substrate for phosphor-free ultraviolet （UV）-white light-emitting diodes （LEDs）.

关键词： Emission spectroscopy Light emission Phosphors x ray diffraction

One-pot synthesis and optical properties of In- and Sn-doped ZnO nanoparticles

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International Journal of Minerals,Metallurgy and Materials 2017年第4期24卷 455-461页

作者： Li-ping Wang Fu Zhang Shuai Chen Zi-heng Bai Department of Materials Physics and Chemistry School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Colloidal indium-doped zinc oxide (IZO) and tin-doped zinc oxide (ZTO) nanoparticles were successfully prepared in organic solution, with metal acetylacetonate as the precursor and oleylamine as the solvent. The crystal and optical properties were characterized by x-ray diffraction, UV−visible spectrophotometry, and fluorescence spectroscopy, respectively; the surface and structure morphologies were observed by scanning electron microscopy and transmission electron microscopy. The xRD patterns of the IZO and ZTO nanoparticles all exhibited similar diffraction peaks consistent with the standard xRD pattern of ZnO, although the diffraction peaks of the IZO and ZTO nanoparticles were slightly shifted with increasing dopant concentration. With increasing dopant concentration, the fluorescent emission peaks of the IZO nanoparticles exhibited an obvious red shift because of the difference in atomic radii of indium and zinc, whereas those of the ZTO nanoparticles exhibited almost no shift because of the similarity in atomic radii of tin and zinc. Furthermore, the sizes of the IZO and ZTO nanoparticles distributed in the ranges 20–40 and 20–25 nm, respectively, which is attributed to the difference in ionic radii of indium and tin. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

关键词： Crystal structure Doping (additives) Electron microscopy Fluorescence Fluorescence spectroscopy High resolution transmission electron microscopy Indium Metal nanoparticles Nanoparticles Optical properties Scanning electron microscopy Semiconductor doping Tin Tin oxides Transmission electron microscopy x ray diffraction Zinc Zinc oxide