Jajarm's bauxite deposits are mainly diasporic, and they have a low mass ratio of Al2O3/SiO2. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis...Jajarm's bauxite deposits are mainly diasporic, and they have a low mass ratio of Al2O3/SiO2. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al2O3 and 13.35wt% SiO2, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000+710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350+710, -710+212, and -212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al2O3/SiO2 mass ratios of 5.03, 5.16, and 5.15 for the -3350+710, -710+212, and -212+ 125 μ m sizes, respectively.展开更多
The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force betwe...The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency.In this paper,based on the extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory,the van der Waals,electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first,and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration,mineral particle size,air bubble size,collector type(dodecylamine hydrochloride(DAH)and sodium oleate(NaOL))and concentration,and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles.The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution.The increase in electrolyte concentration reduced the interaction force or even changed the direction of the force under certain circumstances.The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinitebubble and diaspore-bubble respectively.Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values.The research results have theoretical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.展开更多
The floatation of the minerals diaspore and kaolinite was investigated using dodecylamine as the collector.Separating diaspore and kaolinite in a neutral pH pulp is difficult since they then have similar floatability....The floatation of the minerals diaspore and kaolinite was investigated using dodecylamine as the collector.Separating 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 problem.Diaspore sinking may be seen when the ratio of AlCl3 to Na2SiO3 is 3:1.We refer to this mixture as ATNO.The influence of Al/Si ratio in the feedstock and the grain size of fed minerals on separation was examined.An 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 4.96.However,the grain size of the diaspore greatly influences the concentrate grade.Finer grain size of the diaspore(<40 μm) in pulp makes the flotation separation less than ideal,no matter what the kaolinite grain size.展开更多
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 ...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.[展开更多
Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce effici...Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce efficiently serious scaling problem of bauxite slurry on indirect heating surface, which certainly happens in the single stream process and brings about great troubles to the indirect heating. As a result of a great number of experiments and the theoretical analysis, a new lime adding technology for the two-stream digestion process is developed in this paper that lime is added into spent liquor stream instead of bauxite slurry, which is more suitable to the two-stream process of diasporic bauxite. The influences of the new lime addition technology on preheating and digestion process were discussed. It was deduced that the new technology can be used efficiently in the two-stream process of non-diasporic bauxite.展开更多
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...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 ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis (EICA) of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.展开更多
The depiction of food and foodways abounds in Indian American writer Jhumpa Lahiri’s Pulitzer Prize winning debut Interpreter of Maladies,creating an enticing element to arrest readers’attention.In this collection o...The depiction of food and foodways abounds in Indian American writer Jhumpa Lahiri’s Pulitzer Prize winning debut Interpreter of Maladies,creating an enticing element to arrest readers’attention.In this collection of short stories,Lahiri uses food as a means to navigate alienation and affection,as a conduit to recapture and relive old memories,and as a vehicle to articulate cultural construction of a new identity.Her manoeuvre of culinary writing is so adept that each item of food constitutes a situation to signal deep-hidden meaning beneath its surface information.Thus food becomes signs or metaphors of overseas Indian diasporic experience.展开更多
In search of new mineral raw materials with industrial potential, we identified a deposit located in the southwest of Oujda (in the Northeastern Morocco). The physicochemical analyses indicate that the ore consists ma...In search of new mineral raw materials with industrial potential, we identified a deposit located in the southwest of Oujda (in the Northeastern Morocco). The physicochemical analyses indicate that the ore consists mainly of diaspore, topaz and quartz, and also secondary minerals. The presence of topaz in the ore is explained by hydrothermal action on the structure of diaspore. The investigation of structural transformations reveals complex reaction mechanisms that result in a mixture of corundum-mullite at 1200℃, which is of great industrial interest. Thus, the peculiarity of this ore is the presence of fluorine and secondary minerals.展开更多
The explosion of African literatures in 2021 is not a coincidence,but is dictated by the continent's decolonial,diasporic and hybrid cultural manifestations,its more than a hundred years of struggle for cross-regi...The explosion of African literatures in 2021 is not a coincidence,but is dictated by the continent's decolonial,diasporic and hybrid cultural manifestations,its more than a hundred years of struggle for cross-regional integration,its spirit of vigorous and persistent action,and the unique attraction of an Africanness that upholds its selfhood,bridges the gaps,and remembers its history but looks to the future.The diasporic characteristic of attending to,absorbing and squarely facing the tension of heterogeneous cultures means that indigenous African literatures contain a distinctive world consciousness and rational philosophy.They have given rise to diverse civilizations marked by dialogue,inclusiveness and the contemporary spirit of African nations,enabling African literatures to participate effectively in the dialogue of world literature and in new patterns of civilization,displaying as they do a strong vitality,creativity and influence in the positive-sum game with Western culture.This will provide positive encouragement to the mutual learning,integration,harmony,symbiosis andcoexistenceofcivilizations.展开更多
The aim of this work is to describe the possibilities of preparing a corundum coating onaluminum alloy through in-situ chemical reaction at a relative low temperature. The transformationconditions of diaspore (β-AI...The aim of this work is to describe the possibilities of preparing a corundum coating onaluminum alloy through in-situ chemical reaction at a relative low temperature. The transformationconditions of diaspore (β-AIOOH) to corundum (α-Al<sub>2</sub>O<sub>3</sub> ) are studied using X-ray diffraction analy-sis. Temperature and heating time are two main factors influencing the transformation. Suitableheating parameters can lower the transformation temperature. On this basis, a new process isdeveloped to produce corundum ceramic coating on an aluminum alloy substrate. The phasecomposition and microstructure of the coating are studied using X-ray diffraction analysis andScanning Electron Microscopy. Abrasion properties of the coating are evaluated by ring-block tri-botester. The results show that it is feasible to obtain ceramic coatings on aluminum alloy sub-strates by means of thermo-decomposition of diaspore.展开更多
This paper investigates the changes of phase and apparent morphology under the combined effects of an intense magnetic field and temperature field.The effect of different roasting conditions on the digestion performan...This paper investigates the changes of phase and apparent morphology under the combined effects of an intense magnetic field and temperature field.The effect of different roasting conditions on the digestion performance of roasted ore is also studied.The results indicate that roasting pretreatment under high magnetic fields can change the microstructure and digestion performance of bauxite.The Al phase changed faster of high iron bauxite than that of low iron bauxite.The digestion performance of low iron bauxite improved significantly through roasting pretreatment in intense magnetic field. But the digestion performance of bauxite get worse with the iron content in bauxite increase,because the high iron content of bauxite lead the shielding effect of magnetic field and make the crystal structure of bauxite stably,the surface area or low iron bauxite increased obviously during pretreatment.The optimal pretreatment condition of low iron bauxite is roasting temperature of 550℃,roasting time of 60min and magnetic field intensity of 6T,while for the high iron is roasting temperature of 500℃,roasting time of 60min and magnetic field intensity of 9T.展开更多
文摘Jajarm's bauxite deposits are mainly diasporic, and they have a low mass ratio of Al2O3/SiO2. It is necessary to increase the run-of-mine mass ratio before feeding the material to the Bayer process. Chemical analysis indicated that the low-grade bauxite sample from Jajarm contained 43.9wt% Al2O3 and 13.35wt% SiO2, resulting in a mass ratio of 3.29. According to mineralogical studies, the presence of aluminosilicate minerals such as kaolinite, illite, and quartz was the main reason for the decrease of the mass ratio. Microscopic observations revealed that, with the size reduction from -1000+710 to -38 μm, the liberation degree of diaspore increased from 10% to 60%, and that of aluminosilicates increased from 20% to 85%. Heavy liquids with the densities of 2.8, 3.0, 3.2, and 3.4 g/cm3 were used to evaluate the heavy media separation in three sizes, i.e., -3350+710, -710+212, and -212+125 μm. Laboratory studies confirm that the density of 3.2 g/cm3 can produce the concentrates (in sunk fractions) with recoveries of 89.09%, 91.24%, and 84.68% with the Al2O3/SiO2 mass ratios of 5.03, 5.16, and 5.15 for the -3350+710, -710+212, and -212+ 125 μ m sizes, respectively.
基金supported by the National Natural Science Foundation of China(No.51904240,51904239,52104268)the Natural Science Foundation of Shaanxi Province(No.2020JQ-752,2021JQ-571)+3 种基金the Postdoctoral Science Foundation of China(No.2019M653877XB)the Outstanding Youth Science Foundation of Xi’an University of Science and Technology(No.2019YQ3-08)the Huo Yingdong Education Foundation(No.171102)the 2019 Merit-based Science and Technology Project Foundation for Shannxi Overseas-educated Scholars(No.14).
文摘The flotation of diasporic bauxite is to separate diaspore(valuable mineral)from aluminosilicate minerals(gangue minerals,mainly including kaolinite,illite and pyrophyllite),and the microscopic interaction force between the two types of minerals and air bubbles determines the separation efficiency.In this paper,based on the extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory,the van der Waals,electrostatic and hydrophobic interaction between particles of the four minerals mentioned above and air bubbles in collectorless solution were calculated first,and then diaspore and kaolinite were taken as examples to analyze the influence of various factors such as electrolyte concentration,mineral particle size,air bubble size,collector type(dodecylamine hydrochloride(DAH)and sodium oleate(NaOL))and concentration,and pulp pH on the interactions between the particles of valuable mineral and gangue minerals and air bubbles.The results showed that the total extended DLVO interactions between the four minerals and air bubbles were repulsive in most cases in collectorless solution.The increase in electrolyte concentration reduced the interaction force or even changed the direction of the force under certain circumstances.The addition of DAH and NaOL can reduce the adhesion energy barrier of kaolinitebubble and diaspore-bubble respectively.Each type of minerals exhibited a specific interface interaction response with air bubbles in each collector with different pH values.The research results have theoretical guiding significance for the optimization and directional control of diasporic bauxite flotation conditions.
基金support for this study obtained from the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality (No.PHR 200906210)Funding Project for Base Construction of Scientific Research of Beijing Municipal Commission of Education (No.WYJD200902)Funding Project for Science and Technology Program of Beijing Municipal Commission of Education (No.KM 200810037001) is gratefully acknowledged
文摘The floatation of the minerals diaspore and kaolinite was investigated using dodecylamine as the collector.Separating 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 problem.Diaspore sinking may be seen when the ratio of AlCl3 to Na2SiO3 is 3:1.We refer to this mixture as ATNO.The influence of Al/Si ratio in the feedstock and the grain size of fed minerals on separation was examined.An 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 4.96.However,the grain size of the diaspore greatly influences the concentrate grade.Finer grain size of the diaspore(<40 μm) in pulp makes the flotation separation less than ideal,no matter what the kaolinite grain size.
文摘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.[
文摘Indirect heating and intensified digestion technology can be applied to reduce greatly the energy consumption in Bayer process of diasporic bauxite. A great advantage of two-stream process is to avoid or reduce efficiently serious scaling problem of bauxite slurry on indirect heating surface, which certainly happens in the single stream process and brings about great troubles to the indirect heating. As a result of a great number of experiments and the theoretical analysis, a new lime adding technology for the two-stream digestion process is developed in this paper that lime is added into spent liquor stream instead of bauxite slurry, which is more suitable to the two-stream process of diasporic bauxite. The influences of the new lime addition technology on preheating and digestion process were discussed. It was deduced that the new technology can be used efficiently in the two-stream process of non-diasporic bauxite.
基金supported by the International Science and Technology Cooperation Program of China (2010DFA92720-06)with partial support to RSN from the US National Science Foundation (1047575) and the Nevada Agricultural Experiment Station
文摘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 ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis (EICA) of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.
文摘The depiction of food and foodways abounds in Indian American writer Jhumpa Lahiri’s Pulitzer Prize winning debut Interpreter of Maladies,creating an enticing element to arrest readers’attention.In this collection of short stories,Lahiri uses food as a means to navigate alienation and affection,as a conduit to recapture and relive old memories,and as a vehicle to articulate cultural construction of a new identity.Her manoeuvre of culinary writing is so adept that each item of food constitutes a situation to signal deep-hidden meaning beneath its surface information.Thus food becomes signs or metaphors of overseas Indian diasporic experience.
文摘In search of new mineral raw materials with industrial potential, we identified a deposit located in the southwest of Oujda (in the Northeastern Morocco). The physicochemical analyses indicate that the ore consists mainly of diaspore, topaz and quartz, and also secondary minerals. The presence of topaz in the ore is explained by hydrothermal action on the structure of diaspore. The investigation of structural transformations reveals complex reaction mechanisms that result in a mixture of corundum-mullite at 1200℃, which is of great industrial interest. Thus, the peculiarity of this ore is the presence of fluorine and secondary minerals.
基金a phased achievement of the key project“History of African Literatures in English”(19ZDA296)sponsored by the National Social Science Fund of China.
文摘The explosion of African literatures in 2021 is not a coincidence,but is dictated by the continent's decolonial,diasporic and hybrid cultural manifestations,its more than a hundred years of struggle for cross-regional integration,its spirit of vigorous and persistent action,and the unique attraction of an Africanness that upholds its selfhood,bridges the gaps,and remembers its history but looks to the future.The diasporic characteristic of attending to,absorbing and squarely facing the tension of heterogeneous cultures means that indigenous African literatures contain a distinctive world consciousness and rational philosophy.They have given rise to diverse civilizations marked by dialogue,inclusiveness and the contemporary spirit of African nations,enabling African literatures to participate effectively in the dialogue of world literature and in new patterns of civilization,displaying as they do a strong vitality,creativity and influence in the positive-sum game with Western culture.This will provide positive encouragement to the mutual learning,integration,harmony,symbiosis andcoexistenceofcivilizations.
文摘The aim of this work is to describe the possibilities of preparing a corundum coating onaluminum alloy through in-situ chemical reaction at a relative low temperature. The transformationconditions of diaspore (β-AIOOH) to corundum (α-Al<sub>2</sub>O<sub>3</sub> ) are studied using X-ray diffraction analy-sis. Temperature and heating time are two main factors influencing the transformation. Suitableheating parameters can lower the transformation temperature. On this basis, a new process isdeveloped to produce corundum ceramic coating on an aluminum alloy substrate. The phasecomposition and microstructure of the coating are studied using X-ray diffraction analysis andScanning Electron Microscopy. Abrasion properties of the coating are evaluated by ring-block tri-botester. The results show that it is feasible to obtain ceramic coatings on aluminum alloy sub-strates by means of thermo-decomposition of diaspore.
基金Item Sponsored by the Natural Science Foundation of China(NO.51004033,No.50934005,No.50974035,No.51074047)National 863 plan(2010AA03A405,2012AA061403)+1 种基金Operation expenses for universities'basic scientific research(N100302005)The doctoral fund of EDU gov(20050145029)
文摘This paper investigates the changes of phase and apparent morphology under the combined effects of an intense magnetic field and temperature field.The effect of different roasting conditions on the digestion performance of roasted ore is also studied.The results indicate that roasting pretreatment under high magnetic fields can change the microstructure and digestion performance of bauxite.The Al phase changed faster of high iron bauxite than that of low iron bauxite.The digestion performance of low iron bauxite improved significantly through roasting pretreatment in intense magnetic field. But the digestion performance of bauxite get worse with the iron content in bauxite increase,because the high iron content of bauxite lead the shielding effect of magnetic field and make the crystal structure of bauxite stably,the surface area or low iron bauxite increased obviously during pretreatment.The optimal pretreatment condition of low iron bauxite is roasting temperature of 550℃,roasting time of 60min and magnetic field intensity of 6T,while for the high iron is roasting temperature of 500℃,roasting time of 60min and magnetic field intensity of 9T.