Key Laboratory for Metallurgy and Material Processing of Rare Metals

Changsha, China

Key Laboratory for Metallurgy and Material Processing of Rare Metals

Changsha, China
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Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Li J.,Central South University | Li J.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | And 5 more authors.
Hydrometallurgy | Year: 2011

A technology has been developed for extracting tungsten from scheelite concentrate with caustic soda by an autoclaving process. In this process, the effects of different variables on the digestion of scheelite, and on the evaporation of the crude sodium tungstate leach solution, has been investigated. The results showed that 98.8% W was leached in 2 h at 160 °C under the conditions of 2.2 stoichiometric ratio of NaOH and liquid /solid ratio 0.8:1 stirred at 400 rpm. After evaporation, about 90% sodium tungstate was crystallized, leaving impurities of PO4 2-, AsO 4 2- and SiO3 2- in the mother solution. The filtered mother solution contained about 93% of the unconsumed caustic soda which can be recycled for a new round of leaching. This technology has been successfully put into industrial practice and can treat almost any tungsten ore, including scheelite middling and wolframite-scheelite mixed concentrates. © 2011 Elsevier B.V. All rights reserved.


Chen X.,Central South University | Chen X.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Liu X.,Central South University | Liu X.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | And 4 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2016

Tungsten is hard to be separated effectively from molybdate solution due to their extremely similar chemical properties. In this research, a novel tungsten removal method was developed to remove tungsten from the molybdate solution using nascent MnO2. Through comparing different preparation method of nascent MnO2, in situ synthesized method was chosen as the optimal preparation route. And the effects of reaction temperature, Mn addition, pH value, reaction time and Mo/W mass ratio of solution on the tungsten removal were also investigated. The experimental results showed tungsten could be selectively removed quickly from molybdate solution. On the optimal reaction conditions of reaction temperature 25 °C, 50 times theoretical reagent amount of Mn addition, pH value 8.0–8.5 and reaction time 1.0 h, 95% of tungsten can be removed from the molybdate solution with different Mo/W mass ratio and the Mo loss can be controlled to only about 5%. The results showed that nascent MnO2 was a high-efficiency tungsten removal reagent from the molybdate solution. © 2016 Elsevier Ltd


Chen X.,Central South University | Liu X.,Central South University | Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Hao M.,Central South University
International Journal of Refractory Metals and Hard Materials | Year: 2015

The matte smelting method was developed to treat molybdenite using the white matte as the dissolvent. The key for achieving the process depended on whether or not molybdenite can form the molybdenum matte. The dissolving capacity of molybdenite in the white matte was evaluated in this study. The effects of the ratio of molybdenite and white matte and the melting temperature on the matte melting were investigated. In addition, given that white matte and molybdenite contained various kinds of impurities, the effects of the Fe content and the grade of matte on the solubility of molybdenite were also researched. The research results showed that with 0-20% MoS2 addition at 1250 °C, the MoS2 content within the matte increases with the MoS2 addition reaching a maximum content of 14.95%. A higher level of 20% of MoS2 addition resulted in a steep decline in the MoS2 content. The increase of Fe contents in the white matte will cause the reduction of the solubility of MoS2 in the matte. In addition, an excessive Cu content in the white matte reduced the dissolving capacity of molybdenite in the copper matte. As the copper content of white matte reached 20%, the dissolved Mo was only 9.33%. © 2015 Elsevier Ltd. All rights reserved.


Chen X.,Central South University | Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Hao M.,Central South University | Wang D.,Central South University
International Journal of Energy Research | Year: 2013

In order to prevent the inert alumina film from forming on the surface of Al metal particles, Li is added into Al to form Al-Li alloy. It can improve the reactivity of Al with water. The prepared Al-Li alloy can rapidly split water to produce hydrogen. With increasing Li content of alloy, the hydrogen generation rate is promoted. The ultimate hydrogen yields of samples can reach 100%. The effect of initial water temperature on the hydrogen generation has been investigated. Even in the water at 0°C, hydrogen can also be produced rapidly. Composition of solution has some effect on the hydrogen generation. Especially, Mg2+ or NO3 - has negative influence on the hydrogen generation and can reduce the ultimate hydrogen yield of alloy. Longer air exposure time will also decrease the ultimate hydrogen yield. After reaction, Al and Li enter into the residue in the form of LiAl2(OH)7·2H2O and LiAl2(OH)7·xH2O or Al(OH)3. After calcinations, these reaction by-products can be easily recycled by existing metallurgical process. © 2012 John Wiley & Sons, Ltd.


Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Chen X.,Central South University | Hao M.,Central South University
Energy | Year: 2011

A new hydrogen generation material, Al-Ca alloy, is prepared by ball milling method. Results show the prepared Al-Ca alloy can react with to produce hydrogen, but its hydrogen yield is lower. NaCl addition can further greatly improve hydrogen generation of Al-Ca alloys. The amount of NaCl addition and ball milling time depends on the Ca contents of alloys. As the Ca contents of alloy increase, the amount of NaCl addition or ball milling time may be reduced accordingly. Increasing Ca contents, NaCl addition or ball milling time is beneficial to improve the hydrogen generation rate. Al-Ca alloys can react with water to produce hydrogen at the temperature ranging from 10°C to 80°C, and simultaneously a great amount of heat is released. With the increase of air exposure time, the dense Al 2O 3 and CaO layer formed on the surface of alloy particles will reduce the oxidation reaction rate. Chloride ions and sulfate ions can greatly decrease the induction period of hydrogen generation reaction and obviously improve hydrogen generation rate. Ca 2+ ions and Mg 2+ ions can affect the production of hydrogen due to their strong affinity to OH -, especially Mg 2+ ions which greatly decrease the hydrogen yield to 20%. © 2011 Elsevier Ltd.


Chen X.,Central South University | Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Liu X.,Central South University | And 3 more authors.
Journal of Power Sources | Year: 2014

The addition of Li can prevent an inert alumina film from forming on the surface of Al alloy particles, allowing the rapid hydrogen generation of Al alloys to be achieved. However, because the Li content is less than 10%, the hydrogen generation rate and hydrogen yield of Al-Li alloys are significantly decreased. In this work, NaCl is introduced to prepare Al-Li alloys with low Li contents by ball milling. The research results show that by increasing the amount of NaCl added, the ball milling time and Li content can effectively improve the hydrogen generation of the alloys. Under optimal preparation conditions, the ultimate hydrogen yield of Al-Li alloys can reach 100%. The initial water temperature has almost no effect on the generation of hydrogen, even at 0 C. Ca2+ and Mg2+ can combine with OH- to form the insoluble compounds Ca(OH)2 and Mg(OH)2, which can prevent hydrogen generation. NO3 - reacts with Al to form ammonia and reduce the hydrogen yield of the alloys. Therefore, Al-Li alloys should be prevented from reacting with water containing Ca2+, Mg2+ and NO3 -. Al-Li alloys must be stored in isolation from air to maintain good hydrogen-generation performances. © 2013 Elsevier B.V. All rights reserved.


Chen X.,Central South University | Zhao Z.,Central South University | Zhao Z.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Hao M.,Central South University | Wang D.,Central South University
Journal of Power Sources | Year: 2013

Al, CaO and salt powder mixtures are used as the starting materials to prepare the Al-based materials by the mechanical ball-milling method for hydrogen generation. The effects of preparation and reaction parameters on the hydrogen generation are investigated in this paper. With increasing ball milling time, the Al crystallite size is reduced and the reaction activity of Al is improved. But the overlong ball milling time easily causes the oxidation of Al and decreases its hydrogen yield. CaO can provide OH- for the hydrogen generation reaction by hydrolysis. Increasing the NaCl addition can accelerate the activation of Al and promote its hydrogen generation. In the water containing chloride ions and sulfate ions, the hydrogen generation rate is obviously improved. But Mg2+ ions will reduce the hydrogen yield due to its strong affinity to OH-. The maximum hydrogen yield is gained in the water at 30 °C There are some CaO on the surface of Al particle in the Al-based materials, which can improve the air oxidation resistance in air. Storing the Al-based materials in air with relative humidity of 50% at 30 °C for 40 h, the hydrogen yield is still kept at 89%. © 2012 Elsevier B.V. All rights reserved.


Chen X.,Central South University | Chen X.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | Chen A.,Central South University | Chen A.,Key Laboratory for Metallurgy and Material Processing of Rare Metals | And 7 more authors.
Hydrometallurgy | Year: 2013

In this research, a novel reagent, nickel thiocarbonate (NiCS3), was synthesized to remove Cu from the nickel electrolysis anolyte. Through the experimental research, the effect of reagent amount of NiCS3, reaction temperature, pH value and reaction time on the copper removal was investigated. The experimental results showed that NiCS3 had high reaction activity, and Cu in the nickel electrolysis anolyte can be removed quickly. With the optimal reaction conditions of reagent amount of NiCS 3 1.4-1.6 times of theoretical amount, reaction temperature of ≥ 60 C, pH value of 4.0 and reaction time of 30 min, the Cu concentration was reduced to less than 3 mg/l in the nickel electrolysis anolyte and the mass ratio of Cu/Ni in the Cu-removal precipitates exceeded 15. The result can well satisfy the production requirement of qualified electrodeposited nickel. Therefore, NiCS3 can be used as the high-efficiency reagent to remove copper from the nickel electrolysis anolyte in the large-scale industrial production. © 2012 Elsevier B.V.

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