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diaspore characteristics and ecological adaptation of Bromus tectorum *** different distribution regions

Journal of Arid Land 2013年第3期5卷 310-323页

作者： YaoBin LIU YuanMing ZHANG Robert S NOWAK Liliya DIMEYEVA Key Laboratory of Biogeography and Bioresource in Arid Land Xinjiang Institute of Ecology and GeographyChinese Academy of Sciences Graduate University of Chinese Academy of Sciences Department of Natural Resources and Environmental Science University of Nevada-RenoRenoNevada 89557USA Institute of Botany and Phytointroduction Almaty 050040Kazakhstan

The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi-arid region of North America, the species of European annual grass Bromus tectorum L. is an outstanding example of these problems, which not only increase the fire density and change the fire regime, but replace native communities. Therefore, there are amount of researches on B. tectorum, including resource acquisition, water use efficiency and growth. Whereas the relevant research on the morphology of diaspore is scare. diaspores have a fundamental role in seed germination and seedling establishment. Besides, as an important link between different generations, diaspores have a vital significance on individual reproduction and population extension. Hence, dias- pores under selection for studying have an important implication. This study compares differences in seed mor- phology for Bromus tectorum collected from the United States, Kazakhstan, and Xinjiang of China. The following indices of B. tectorum diaspores were analyzed： size, thickness of covering layers, and micromorphological char- acteristics of the base, middle and transition area of diaspores as well as of the awn. Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy. Results showed that thick- ness of the lemma and the palea of diaspores from B. tectorum-infested grasslands in the United States were re- duced （P〈0.05）, likely because of environmental influences. This reduction facilitated the germination of diaspores and lowered the resistance of B. tectorum to adverse environmental conditions. The length of the awn also in- creased significantly （P〈0.05）, which helped in dispersal and anchoring of diaspores. Therefore, B. tectorum adapted ecologically to its new environment in the United States by strengthening its establishment a

关键词： Bromus tectorum diaspore micromorphology lemma Kazakhstan United States Xinjiang of China

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Effect of modified starches on depression of diaspore

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Transactions of Nonferrous Metals Society of China 2010年第8期20卷 1494-1499页

作者：李海普张莎莎蒋昊李彬 School of Chemistry and Chemical Engineering Central South University School of Minerals Processing and Bioengineering Central South University

Four modified starches with selected charge characteristics including cationic starch(CAS),carboxymethyl starch(CMS),amphoteric starch(AMS) and soluble starch(SS) were investigated as depressants for diaspore in reverse flotation test using cationic collector(dodecylamine).Adsorption examination,Zeta potential measurement and Fourier transform infrared(FTIR) spectroscopy were used to clarify the role of the surface charge characteristics of starches in determining the adsorption behavior and depression performance as well as the mineral-starch *** show that the positively charged starches(CAS and AMS) display higher adsorption amounts and also better depression performance compared with the non-ionic(SS) and anionic starch(CMS),benefiting from the favorable electrostatic attraction with diaspore and also electrostatic repulsion with *** spectroscopy proves the presence of hydrogen bonds and chemical complexation between mineral and starches in an integrated manner.

关键词： starch diaspore reverse flotation depressant

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Flotation techniques for separation of diaspore from bauxite using Gemini collector and starch depressant

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Transactions of Nonferrous Metals Society of China 2010年第3期20卷 495-501页

作者：夏柳荫钟宏刘广义 School of Chemistry and Chemical Engineering Central South University

The floatability of diaspore and three kinds of silicate minerals,including kaolinite,illite and pyrophyllite,by a cationic Gemini surfactant as collector and starch as depressant was investigated as function of reagents concentration and pulp *** studies of artificially mixed minerals and bauxite ore were also detailedly *** last,the pre-desliming reverse flotation separation process was *** can be concluded that the combinational use of a Gemini cationic collector and the starch depressant is *** concentrates with Al2O3 to SiO2 mass ratio of 9.66 and the recovery of Al2O3 of 71.73% are obtained from natural bauxite ore(A/S=5.70) at pH value of around 10.

关键词： diaspore bauxite reverse flotation Gemini surfactant

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Flotation of kaolinite and diaspore with hexadecyl dimethyl benzyl ammonium chloride

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Journal of Central South University of Technology 2008年第3期15卷 378-381页

作者：胡岳华欧阳魁曹学锋张丽敏 School of Resources Processing and Bioengineering Central South University

Tertiary amine was synthesized from fatty amine and formaldehyde. And then the synthesized tertiary amine was used to react with benzyl chloride to synthesize hexadecyl dimethyl benzyl ammonium chloride (1627) at ambient pressure. Using the synthesized 1627 as collector,the flotation properties of diaspore and kaolinite were investigated by single mineral and mixed mineral test. The flotation mechanism of diaspore,kaolinite and 1627 was discussed based on FTIR spectra. The results show that the mass ratio of aluminum to silicate achieves 15.02 and the recovery of alumina in concentrate is 43.07% using 1627 as a collector. The 1627 is found to be a more effective and a promising collector for reverse flotation to remove aluminum-silicate minerals from bauxite.

关键词： kaolinite diaspore hexadecyl dimethyl benzyl ammonium chloride dodecyl amine reverse floatation infra-red spectrum

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Adsorption of copper(Ⅱ) and chromium(Ⅵ) on diaspore

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Journal of Central South University of Technology 2008年第4期15卷 515-519页

作者：刘晓文王建绒胡岳华 School of Resources Processing and Bioengineering Central South University

The adsorption of Cu(Ⅱ)and Cr(Ⅵ)on diaspore was studied with the help of X-ray diffraction analysis,BET measurement,zeta potential measurement and atomic adsorption *** adsorption equilibrium almost reaches within 60 *** adsorption isotherms of Cu(Ⅱ)and Cr(Ⅵ)could be well described by the Langmuir *** adsorption capacities of Cu(Ⅱ)and Cr(Ⅵ)are 1.944 and 1.292 mg/g,*** adsorption percentage of Cr(Ⅱ)increases with the increment of solution pH,but the adsorption percentage of Cr(Ⅵ)*** could be explained by zeta potential theoretical and electrostatic attraction between metal ions and diaspore surface.

关键词： diaspore adsorption copper(Ⅱ ) chromium(Ⅵ) zeta potential

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Alteration of diaspore by thermal treatment

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Journal of Central South University of Technology 2004年第2期11卷 173-175页

作者：杨华明胡岳华杨武国敖伟琴邱冠周 School of Resources Processing and Bioengineering Central South University

diaspore （α-AlOOH） was heated at various temperatures from 300 to 1 000 ℃ for 2 h. The alteration of diaspore by thermal treatment was investigated by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. The mechanism of thermal decomposition of diaspore was discussed according to the Coats-Redfern （equation.） It is found that after thermal treatment at 500 ℃, diaspore is transformed entirely to corundum （（α-Al2O3）.） Combined with the mass loss ratio obtained from the thermogravimetric analysis data, the activation energies for the thermal treatment of diaspore are calculated as Ea=10.4 kJ/mol below 400 ℃ and Eb=47.5 kJ/mol above 400 ℃, respectively, which is directly related to the structural alteration of diaspore during the thermal treatment. The results indicate that the thermal decomposition of diaspore is conducted primarily by means of an interfacial reaction.

关键词： diaspore thermal treatment X-ray diffraction thermal analysis activation energy

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A novel depressor useful for flotation separation of diaspore and kaolinite

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Mining Science and Technology 2010年第2期20卷 292-295页

作者： GUO, Jian information school beijing wuzi universitybeijfing 101149china

The floatation of the minerals diaspore and kaolinite was investigated using dodecylamine as the *** diaspore and kaolinite in a neutral pH pulp is difficult since they then have similar floatability.A depressor consisting of an AlCl3/Na2SiO3 mixture is demonstrated to solve this *** sinking may be seen when the ratio of AlCl3 to Na2SiO3 is 3:*** refer to this mixture as *** influence of Al/Si ratio in the feedstock and the grain size of fed minerals on separation was *** Al/Si ratio in the concentrate greater than 11 may be obtained when the Al/Si ratio of the feed is between 2.53 and ***,the grain size of the diaspore greatly influences the concentrate *** grain size of the diaspore(<40 μm) in pulp makes the flotation separation less than ideal,no matter what the kaolinite grain size.

关键词： diaspore kaolinite dodecylamine ATNO depressor

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Interaction and flotation of diaspore with alkylamine hydrochlorides

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中国有色金属学会会刊：英文版 2001年第3期11卷 430-433页

作者：覃文庆胡岳华邱冠周蒋昊中南大学矿物工程系湖南长沙 410083

Electrokinetics and flotation of diaspore in solutions of different alkylamine hydrochlorides (with 12,14 and 16 carbon atoms) were studied. The point of zero charge (PZC) of diaspore was determined by measuring zeta potential (streaming potential method) as a function of pH. Dodecyl , tetradecyl and hexadecylamine hydrochloride ions seem to be strongly adsorbed on the interface because they make the zeta potential more positive as the concentration increases. The PZC of diaspore is determined at pH 5.7. Flotation of diaspore was studied and shown to be influenced by the chain length of collectors and both collector and hydrogen ion concentration. The optimal experimental flotation conditions as pH and concentrations agreed well with that predicted from solution chemistry calculations, and the floatability of diaspore is poor while the pH value of flotation system is too high or low. The results of calculation also predict a wide pH range of effective flotation with increasing collector concentration.[

关键词： flotation alkyl amine diaspore

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Flotation behavior of four dodecyl tertiary amines as collectors of diaspore and kaolinite

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Mining Science and Technology 2011年第2期21卷 249-253页

作者： Changmiao Liu Feng Ansheng Guo Zhenxu Cao Xuefeng Hu Yuehu Zhengzhou Institute of Multipurpose Utilization of Mineral Resources fAGS Zhengzhou 450006 China China National Engineering Research Center for Utilization of lndustrial Minerals Zhengzhou 450006 China School of Minerals Processing and Bio-engineering Central South University Changsha 410083 China

The flotation of diaspore and kaolinite by one of a series of tertiary amines（DRN,DEN,DPN and DBN） was *** tertiary amines show better floating recovery for kaolinite compared to *** maximum recovery D-value is 45%over a pH range from 3 to ***-IR spectra confirm the presence of hydroxyl groups on the surface of kaolinite and *** potential measurements show that the mineral surfaces are negatively charged over a wide pH *** of hydroxyl groups mainly accounts for the surface charging *** adsorption of tertiary amines onto the mineral surface is due mainly to electrostatic effects and the difference in electrostatic effect between a collector and the two minerals can explain the flotation *** electronic and steric effects from the substituent groups result in different collecting powers for the four tertiary amines.

关键词： Kaolinite diaspore Amines collectors Froth flotation

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Effect of metallic ions on dispersibility of fine diaspore

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Transactions of Nonferrous Metals Society of China 2011年第5期21卷 1166-1171页

作者：周瑜林胡岳华王毓华中南大学资源加工与生物工程学院长沙410083

Dispersion experiments were conducted to study the influence of metallic cations on the dispersibility of diaspore. The reaction mechanisms were investigated based on the analysis of zeta （ξ） potential and calculations of solution chemistry and DLVO theory. The results show that the valence of cations, instead of the cation type, plays an important role in the dispersibility of diaspore The impact of multivalent metallic cations is greater than that of monovalent cations. In the presence of Ca^2＋ and Mg^2＋, the dispersion of diaspore doesn＇t change in the range of pH value below 10. However, Ca^2＋ and Mg^2＋ may induce strong coagulation of particles when pH value is higher than 10. The adsorption of species of calcium and magnesium ions on diaspore can cause the compression of electric double layer, the decrease of the absolute value of zeta potential and the repulsion force between diaspore particles. The new IEP （isoelectric point） appeared at pH value of 11 may attribute to the adsorption of Mg（OH）2（s）.

关键词： diaspore metallic ions dispersibility zeta potential DLVO theory

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