The separation of manganese from sulfate solutions containing 14.59 g/L Mn2+, 1.89 g/L Mg2+ and 1.54 g/L Ca2+ was preformed successfully by carbonate precipitation. The results of thermodynamic analysis and tests indi...The separation of manganese from sulfate solutions containing 14.59 g/L Mn2+, 1.89 g/L Mg2+ and 1.54 g/L Ca2+ was preformed successfully by carbonate precipitation. The results of thermodynamic analysis and tests indicate that carbonate precipitation holds better selectivity for manganese over magnesium than hydroxide precipitation and the feeding method is the most critical factor for minimizing the co-precipitation of calcium and magnesium. Furthermore, with adding MnSO4 solution to NH4HCO3 solution, the effects of the initial NH4HCO3 concentration, NH4HCO3 amount, solution pH value, reaction temperature and time on carbonate precipitation were evaluated and the optimum precipitation conditions were obtained. Under the optimum conditions, the precipitation rates of Mn2+, Ca2+ and Mg2+ are 99.75%, 5.62% and 1.43%, respectively. Moreover, the prepared manganese carbonate was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The results demonstrate that the product can be indexed to the rhombohedral structure of MnCO3.展开更多
In order to develop a low-cost approach for separating macro amounts of Mo and W, the effects of parameters on the separation using FeSO4 as precipitation reagent were studied. The results show that the optimum reacti...In order to develop a low-cost approach for separating macro amounts of Mo and W, the effects of parameters on the separation using FeSO4 as precipitation reagent were studied. The results show that the optimum reaction temperature is 10 °C, and the separation factor does not further improve after a reaction time of 7 h. Moreover, slow dropping speed of the precipitation reagent is beneficial for improving the separation efficiency. When the H＋/W molar ratio is below 1/1, the addition of acid to a neutral solution is favorable to the separation. For the solution with an ammonium concentration below 3 mol/L, the separation factor is high due to the high W-precipitation rate. Furthermore, the method is also effective when it is applied to industrial solution containing some other impurities. All these indicate the ferrous salts have great potential for removing W from Mo on a commercial scale.展开更多
The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology ...The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology and constitution of Ir film were examined by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. It is found that the reduction mechanism of Ir（III） is a three-electron step and electro reaction is a reversible diffusion controlled process; the diffusion coefficients of Ir（III） at 1083, 1113, 1143 and 1183 K are 1.56×10-4, 2.23×10-4, 2.77×10-4 and 4.40×10-4 cm2/s, respectively, while the activation energy of the electrode reaction is 102.95 kJ/mol. The compacted Ir film reveals that the applied potential greatly affects the deposition of Ir, the thickness of Ir film deposited at the potential of reduction peak is the highest, the temperature of the molten salt also exerts an influence on deposition, the film formed at a lower temperature is thinner, but more micropores would occur on film when the temperature went too high.展开更多
The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and el...The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.展开更多
As-Sb alloy was electrodeposited from high arsenic-containing solutions. The influences of current density, Sb（3＋） concentration, reaction temperature and HCl concentration on the electrolyte composition, cell volt...As-Sb alloy was electrodeposited from high arsenic-containing solutions. The influences of current density, Sb（3＋） concentration, reaction temperature and HCl concentration on the electrolyte composition, cell voltage and current efficiency were investigated. The surface morphology, composition and structure of the deposits were analyzed by scanning electron microscopy（SEM）, inductively coupled plasma mass spectrometry（ICP-MS） and X-ray diffraction（XRD）, respectively. The results show that the prepared As-Sb alloy shows an amorphous structure under all conditions. Under the optimized condition, i.e., 10 g/L As（3＋）, 2 g/L Sb（3＋）, 4 mol/L HCl, current density of 4 mA/cm2 and temperature of 20 °C, desired As-Sb alloy with a composition of 70.26% As and 29.74% Sb（mass fraction） is obtained. What is more, the current efficiency is as high as 94.74% and high arsenic removal rate is achieved under this condition.展开更多
By using cyclic and linear sweep voltammetry,the electrochemical deposition behaviors of Mg^2＋ and B^3＋ in fluorides molten salts of KF-MgF2 and KF-KBF4 at 880℃ were investigated,respectively.The results show that ...By using cyclic and linear sweep voltammetry,the electrochemical deposition behaviors of Mg^2＋ and B^3＋ in fluorides molten salts of KF-MgF2 and KF-KBF4 at 880℃ were investigated,respectively.The results show that the electrochemical reduction of Mg^2＋ is a one-step reaction as Mg^2＋＋2e-→Mg in KF-1%MgF2 molten salt,and the electrochemical reduction of B^3＋ is also a one-step reaction as B^3＋＋3e-→B in KF-KBF4 （1%,2% KBF4） molten salts.Both the cathodic reduction reactions of Mg^2＋ and B^3＋ are controlled by diffusion process.The diffusion coefficients of Mg^2＋ in KF-MgF2 molten salts and B^3＋ in KF-KBF4 molten salts are 6.8×10^-7 cm^2/s and 7.85×10^-7 cm^2/s,respectively.Moreover,the electrochemical synthesis of MgB2 by co-deposition of Mg and B was carried out in the KF-MgF2-KBF4 （molar ratio of 6：1：2） molten salt at 750℃.The X-ray diffraction analysis indicates that MgB2 can be deposited on graphite cathode in the KF-MgF2-KBF4 molten salt at 750℃.展开更多
基金Project(51374249)supported by the National Natural Science Foundation of China
文摘The separation of manganese from sulfate solutions containing 14.59 g/L Mn2+, 1.89 g/L Mg2+ and 1.54 g/L Ca2+ was preformed successfully by carbonate precipitation. The results of thermodynamic analysis and tests indicate that carbonate precipitation holds better selectivity for manganese over magnesium than hydroxide precipitation and the feeding method is the most critical factor for minimizing the co-precipitation of calcium and magnesium. Furthermore, with adding MnSO4 solution to NH4HCO3 solution, the effects of the initial NH4HCO3 concentration, NH4HCO3 amount, solution pH value, reaction temperature and time on carbonate precipitation were evaluated and the optimum precipitation conditions were obtained. Under the optimum conditions, the precipitation rates of Mn2+, Ca2+ and Mg2+ are 99.75%, 5.62% and 1.43%, respectively. Moreover, the prepared manganese carbonate was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The results demonstrate that the product can be indexed to the rhombohedral structure of MnCO3.
基金Project (2007AA06Z129) supported by the National High-tech Research and Development Program of China
文摘In order to develop a low-cost approach for separating macro amounts of Mo and W, the effects of parameters on the separation using FeSO4 as precipitation reagent were studied. The results show that the optimum reaction temperature is 10 °C, and the separation factor does not further improve after a reaction time of 7 h. Moreover, slow dropping speed of the precipitation reagent is beneficial for improving the separation efficiency. When the H＋/W molar ratio is below 1/1, the addition of acid to a neutral solution is favorable to the separation. For the solution with an ammonium concentration below 3 mol/L, the separation factor is high due to the high W-precipitation rate. Furthermore, the method is also effective when it is applied to industrial solution containing some other impurities. All these indicate the ferrous salts have great potential for removing W from Mo on a commercial scale.
文摘The reduction mechanism of Ir in the NaCl-KCl-IrCl3 molten salt was investigated by cyclic voltammetry and chronopotentiometry, and Ir film was deposited effectively on platinum in potentiostatic mode. The morphology and constitution of Ir film were examined by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD）. It is found that the reduction mechanism of Ir（III） is a three-electron step and electro reaction is a reversible diffusion controlled process; the diffusion coefficients of Ir（III） at 1083, 1113, 1143 and 1183 K are 1.56×10-4, 2.23×10-4, 2.77×10-4 and 4.40×10-4 cm2/s, respectively, while the activation energy of the electrode reaction is 102.95 kJ/mol. The compacted Ir film reveals that the applied potential greatly affects the deposition of Ir, the thickness of Ir film deposited at the potential of reduction peak is the highest, the temperature of the molten salt also exerts an influence on deposition, the film formed at a lower temperature is thinner, but more micropores would occur on film when the temperature went too high.
基金Project(20871101)supported by the National Natural Science Foundation of ChinaProject(2009WK2007)supported by Key Project of Science and Technology Department of Hunan Province,ChinaProject(CX2009B133)supported by Colleges and Universities in Hunan Province Plans to Graduate Research and Innovation,China
文摘The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.
基金Project(51374185) supported by the National Natural Science Foundation of China
文摘As-Sb alloy was electrodeposited from high arsenic-containing solutions. The influences of current density, Sb（3＋） concentration, reaction temperature and HCl concentration on the electrolyte composition, cell voltage and current efficiency were investigated. The surface morphology, composition and structure of the deposits were analyzed by scanning electron microscopy（SEM）, inductively coupled plasma mass spectrometry（ICP-MS） and X-ray diffraction（XRD）, respectively. The results show that the prepared As-Sb alloy shows an amorphous structure under all conditions. Under the optimized condition, i.e., 10 g/L As（3＋）, 2 g/L Sb（3＋）, 4 mol/L HCl, current density of 4 mA/cm2 and temperature of 20 °C, desired As-Sb alloy with a composition of 70.26% As and 29.74% Sb（mass fraction） is obtained. What is more, the current efficiency is as high as 94.74% and high arsenic removal rate is achieved under this condition.
基金Project(50804010) supported by the National Natural Science Foundation of ChinaProject(2007CB210305) supported by the National Basic Research Program of China
文摘By using cyclic and linear sweep voltammetry,the electrochemical deposition behaviors of Mg^2＋ and B^3＋ in fluorides molten salts of KF-MgF2 and KF-KBF4 at 880℃ were investigated,respectively.The results show that the electrochemical reduction of Mg^2＋ is a one-step reaction as Mg^2＋＋2e-→Mg in KF-1%MgF2 molten salt,and the electrochemical reduction of B^3＋ is also a one-step reaction as B^3＋＋3e-→B in KF-KBF4 （1%,2% KBF4） molten salts.Both the cathodic reduction reactions of Mg^2＋ and B^3＋ are controlled by diffusion process.The diffusion coefficients of Mg^2＋ in KF-MgF2 molten salts and B^3＋ in KF-KBF4 molten salts are 6.8×10^-7 cm^2/s and 7.85×10^-7 cm^2/s,respectively.Moreover,the electrochemical synthesis of MgB2 by co-deposition of Mg and B was carried out in the KF-MgF2-KBF4 （molar ratio of 6：1：2） molten salt at 750℃.The X-ray diffraction analysis indicates that MgB2 can be deposited on graphite cathode in the KF-MgF2-KBF4 molten salt at 750℃.
