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Enhancing mixing of particles by baffles in a rotating drum mixer

颗粒学报（英文版） 2011年第3期9卷 270-278页

作者： Maoqiang Jiang Yongzhi Zhao Gesi Liu Jinyang Zheng State Key Laboratory of Chemical Engineering Institute of Chemical Process Equipment Department of Chemical and Biochemical Engineering Zhejiang University Hangzhou 310027China

Baffles with shape of “-” (single baffle), “+” (cross-baffles with four arms) and (baffles with 6 arms)are used to enhance the mixing of particles in a rotating drum mixer. A micro-dynamics study of mixing and segregation of a bi-disperse system of two particle sizes in the rotating drum with these three kinds of baffles is carried out using the discrete element method (DEM). The effect of the baffles on mixing, and the mechanisms of mixing enhancement by the baffles are discussed and analyzed. Simulation results show that in an unbaffled drum mixer, particle convection, particle diffusion, and size segregation of bidisperse particles, all play important roles in the mixing process; whereas size segregation will be largely restrained when the drum mixer has a baffle, regardless of its shape, and the degree of mixing is higher than that in an unbaffled drum mixer. The different mixing characteristics for “-” shaped baffle, “+” baffle,and baffle are revealed by the simulation results. For “+” or “*” style baffles, there is an optimal size of baffles for the mixing of particles, and the optimal mixing efficiency is higher than that for “-” baffle.

关键词： Particle mixing Size segregation Baffle Drum mixer Discrete element method (DEM)

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Preparation of basic magnesium carbonate and its thermal decomposition kinetics in air

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Journal of Central South University 2011年第6期18卷 1865-1870页

作者：刘欣伟冯雅丽李浩然 Civil and Environmental Engineering School University of Science and Technology Beijing National Key State Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences

The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry （TG-DTG）. The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO3·Mg（OH）2·4H2O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1-1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies （E） were calculated by Flyrm-Wall-Ozawa method. It is obtained from Coats-Redfem＇s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.

关键词： basic magnesium carbonate TG-DTG thermal decomposition kinetics mechanism function

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Facile preparation of robust microcapsules by manipulating metal-coordination interaction between biomineral layer and bioadhesive layer

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ACS Applied Materials and Interfaces 2011年第2期3卷 597-605页

作者： Zhang, Lei Shi, Jiafu Jiang, Zhongyi Jiang, Yanjun Meng, Ruijie Zhu, Yuanyuan Liang, Yanpeng Zheng, Yang Key Laboratory for Green Technology of Ministry of Education School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China National Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China Department of Bioengineering School of Chemical Engineering Hebei University of Technology Tianjin 300130 China

A novel approach combining biomimetic mineralization and bioadhesion is proposed to prepare robust and versatile organicinorganic hybrid microcapsules. More specifically, these microcapsules are fabricated by sequential deposition of inorganic layer and organic layer on the surface of CaCO3 microparticles, followed by the dissolution of CaCO3 microparticles using EDTA. During the preparation process, protamine induces the hydrolysis and condensation of titania or silica precursor to form the inorganic layer or the biomineral layer. The organic layer or bioadhesive layer was formed through the rapid, spontaneous oxidative polymerization of dopamine into polydopamine (PDA) on the surface of the biomineral layer. There exist multiple interactions between the inorganic layer and the organic layer. Thus, the as-prepared organic-inorganic hybrid microcapsules acquire much higher mechanical stability and surface reactivity than pure titania or pure silica microcapsules. Furthermore, protamine/titania/polydopamine hybrid microcapsules display superior mechanical stability to protamine/silica/polydopamine hybrid microcapsules because of the formation of Ti(IV)-catechol coordination complex between the biomineral layer and the bioadhesive layer. As an example of application, three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface of the hybrid microcapsules. The as-constructed multienzyme system displays higher catalytic activity and operational stability. Hopefully, the approach developed in this study will evolve as a generic platform for facile and controllable preparation of organic-inorganic hybrid materials with different compositions and shapes for a variety of applications in catalysis, sensor, drug/gene delivery. © 2011 American Chemical Society.

关键词： Calcium carbonate

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Enhancing mixing of particles by baffies in a rotating drum mixer

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Particuology 2011年第3期9卷 270-278页

Baffles with shape of ＂-＂（single baffle）, ＂＋＂（cross-baffles with four arms） and （baffles with 6 arms） are used to enhance the mixing of particles in a rotating drum mixer. A micro-dynamics study of mixing and segregation ofa bi-disperse system of two particle sizes in the rotating drum with these three kinds of baffles is carried out using the discrete element method （DEM）. The effect of the baffles on mixing, and the mechanisms of mixing enhancement by the baffles are discussed and analyzed. Simulation results show that in an unbaffled drum mixer, particle convection, particle diffusion, and size segregation of hi- disperse particles, all play important roles in the mixing process; whereas size segregation will be largely restrained when the drum mixer has a baffle, regardless of its shape, and the degree of mixing is higher than that in an unbaffled drum mixer. The different mixing characteristics for ＂-＂ shaped baffle, ＂＋＂ baffle, and baffle are revealed by the simulation results. For ＂＋＂ or style baffles, there is an optimal size of baffles for the mixing of particles, and the ootimal mixing efficiency is higher than that for ＂-＂ baffle.

关键词： Particle mixing Size segregation Baffle Drum mixer Discrete element method （DEM）

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Bioinspired preparation of polydopamine microcapsule for multienzyme system construction

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green Chemistry 2011年第2期13卷 300-306页

作者： Zhang, Lei Shi, Jiafu Jiang, Zhongyi Jiang, Yanjun Qiao, Shizhang Li, Jian Wang, Rui Meng, Ruijie Zhu, Yuanyuan Zheng, Yang Key Laboratory for Green Technology of Ministry of Education School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China National Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100190 China Department of Bioengineering School of Chemical Engineering Hebei University of Technology Tianjin 300130 China ARC Centre of Excellence for Functional Nanomaterials Australian Institute for Bioengineering and Nanotechnology The University of Queensland Qld 4072 Australia

Inspired by the structural organization of mitochondria and the bioadhesive principle, a simple and versatile approach to construct a multienzyme system is developed. More specifically, the multienzyme system is composed of a polydopamine (PDA) microcapsule scaffold and three spatially separated enzymes. The PDA microcapsules are prepared through the rapid, spontaneous self-polymerization of dopamine on the surface of CaCO₃ microparticle template, followed by dissolution of the template using EDTA. The wall thickness of the microcapsules can be tuned by the dopamine concentration in an aqueous solution. The three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface under extremely mild conditions. As an example, a multienzyme system, containing α-amylase, β-amylase and glucosidase, was constructed to convert starch into isomaltooligosaccharide, and the multienzyme system displays higher catalytic activity and enhanced operational stability. The method developed in this study will establish a powerful platform for the facile construction of multienzyme cascade systems. © 2011 The Royal Society of Chemistry.

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Microwave-assisted facile synthesis of palladium nanoparticles in HEPES solution and their size-dependent catalytic activities to Suzuki reaction

Microwave-assisted facile synthesis of palladium nanoparticl...

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作者： Zhang, Wei Wang, Qiao Qin, Fan Zhou, Huamin Lu, Zhong Chen, Rong Key Laboratory for Green Chemical Process of Ministry of Education School of Chemical Engineering and Pharmacy Wuhan Institute of Technology Wuhan 430073 China State Key Laboratory of Materials Processing and Die and Mould Technology Huazhong University of Science and Technology Wuhan 430074 China

Palladium nanoparticles (NPs) were successfully synthesized via a rapid and facile microwave route in HEPES (2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid) buffer solution. The shape- and size-controlled Pd nanoparticles could be obtained by one-step method without dependence of seed-mediated growth. The capping agent plays a key role in the formation of Pd NPs with different shape and size, which could be tuned by varying capping agents such as polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), sodium citrate (Na3(cit)) and potassium bromide (KBr). The size-dependent catalytic activities of the obtained Pd NPs for Suzuki coupling reaction were also investigated. It demonstrated that the catalytic activity of Pd NPs was enhanced regularly with the decrease of particle size. Pd NPs less than 10 nm exhibited better catalytic activities for Suzuki reaction than the commercial Pd/C catalyst. Pd/MWCNTs and Pd/SBA-15 nanocomposites were also prepared by a facile method and afforded good catalytic activity and reusability. This "green" synthetic protocol could be used as a general method for the rapid synthesis of transition metal nanoparticles. Copyright © 2011 American Scientific Publishers. All rights reserved.

关键词： Catalyst activity

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Leaching characteristics and recovery method of nickel from low-grade nickel-pyrrhotite

Beijing Keji Daxue Xuebao/Journal of University of Science a...

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Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing 2011年第9期33卷 1065-1070+1090页

作者： Qi, Feng-Jie Feng, Ya-Li Li, Hao-Ran Tian, Jing-Lei School of Civil and Environmental Engineering University of Science and Technology Beijing Beijing 100083 China State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Acad. of Sci. Beijing 100190 China

In order to leach and recover nickel from high-silicon low-grade nickel-pyrrhotite, some factors were determined, including roasting pretreatment control, sulfuric acid use ratio, inoculated Thiobacillus. ferrooxidans or uninoculated. Then sulfate-reducing bacteria (SRB) were immobilized by intact rice chaff in an up-flow anaerobic bed reactor. The leach liquor was treated by the reactor. It is shown that roasting results in the sintering of minerals and makes nickel wrapped, which is not conducive to the leaching of nickel. Thiobacillus ferrooxidans form a biofilm on the mineral surface, which plays a key role in the dissolution of minerals, and oxidizes Fe2+ to be Fe3+, which does a further dissolution of minerals. The leaching rate of nickel reaches to 92.16% and the concentration of Ni2+ is 973.22 mg·L-1. When the influent passes through the reactor at a speed of 2200 to 3600 mL·L-1·d-1, the recovery of Ni2+, which adsorbs on the rice chaff in the form of NiS, is above 98%, and 98% of magnesium exists in the solution in the form of ions. The NiO content increases from 1.69% of the crude ore to 11.84% of the rice chaff.

关键词： Sulfuric acid

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Impact of Hemicellulose on Cellulose Simultaneous Saccharification and Fermentation

Impact of Hemicellulose on Cellulose Simultaneous Saccharifi...

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2011 International Conference on Future Materials engineering and Industry Application(ICFMEIA 2011)

作者： X.Zhou H.Chen Z.Li School of Life Science Beijing Institute of Technology State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences

Hemicellulose is generally considered a negative factor for enzymatic cellulose hydrolysis, but it was proved to be a positive one for the enzymatic action of delignified pulp in this study. Alkaline wheat straw pulp(AWSP) with different hemicellulose proportion was obtained by treating AWSP with 1 M H2SO4 at 100℃ for different time. The soluble fractions of the hydrolyzed mixtures neutralized with Ca(OH)2 together with the insoluble fractions were used for simultaneous saccharification and fermentation(SSF). The ethanol yields reduced while the hemicellulose content of AWSP decreased. The crystallinity increasing after hemicelluloses removal suggested that amorphous hemicellulose interweaving with cellulose prevented cellulose fibers to aggregate compactly and improved the access of cellulases to cellulose. However, the yeast unfermented reducing sugar derived from hemicellulose was inhibitory to SSF.

关键词： Hemicellulose cellulose cellulase alkaline wheat straw pulp(AWSP) simultaneous saccharification and fermentation(SSF)

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Growth and Physiological Features of Cyanobacterium Anabaena sp. Strain PCC 7120 in a Glucose-Mixotrophic Culture

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Chinese Journal of Chemical engineering 2011年第1期19卷 108-115页

作者：喻国策施定基蔡昭铃丛威欧阳藩 Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China Research Center of Photosynthesis Institute of Botany Chinese Academy of Sciences Beijing 100093 China

Mixotrophic growth is one potential mode for mass culture of microalgae and cyanobacteria particularly suitable for the production of high value bioactive compounds and fine *** typical heterocystous cyanobacterium Anabaena *** 7120 was grown in the presence of exogenous glucose in *** improved the cell growth evidently,the maximal specific growth rate under mixotrophic condition（0.38 d 1）being 1.6-fold of that of photoautotrophic *** caused a variation in cellular pigment composition,increasing the content of chlorophyll a and decreasing the contents of carotenoid and phycobiliprotein relative to chlorophyll *** emission from photosystem II（PSII）relative to photosystem I was enhanced in mixotrophic cells,implying an increased energy distribution in ***（EC 2.7.1.2）activity was further induced in the presence of *** mixotrophic culture was scaled up in a 15 L airlift photobioreactor equipped with an inner and an outer light source.A modified Monod model incorporating the specific growth rate and the average light intensity in the reactor was developed to describe cell growth *** understanding of mixotrophic growth and relevant physiological features of Anabaena *** 7120 would be meaningful for cultivation and exploitation of this important cyanobacterial strain.

关键词： cyanobacteria Anabaena sp.PCC 7120 growth features mixotrophic culture photobioreactor

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The Behavior of Ionic Liquids under High Pressure: A Molecular Dynamics Simulation

The Behavior of Ionic Liquids under High Pressure: A Molecul...

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第二届全国离子液体与绿色过程学术会议

作者： Yuling Zhao Xiaomin Liu School of Chemistry and Environmental Science Key Laboratory of Green Chemical Media and ReactionsMinistry of Education Henan Normal University Xinxiang Henan 453007 China Beijing Key Laboratory of Ionic Liquids Clean Process State Key Laboratory of Multiphase Complex Systems Beijing Key Laboratory of Ionic Liquids Clean Process State Key Laboratory of Multiphase Complex SystemsInstitute of Process Engineering Chinese Academy of Science Beijing 100190 China

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