The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and sti...The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and stirring rate on the oxidation rate were investigated. The results show that Fe3O4 formation is composed of two-step reaction, the first step is the formation of Fe（OH）+2 by oxidation of Fe（OH）+ complex ions, the second step is the formation of magnetite by dehydration and deprotonation of Fe（OH）+ and Fe（OH）+2. The oxidation reaction is zero-order with respect to the concentration of Fe（Ⅱ） and around 0.5-order with respect to partial pressure of oxygen, and oxygen transfer process is rate-limiting step of oxidation reaction with apparent activation energy of 2.74 kJ·mol-1.展开更多
Alkali-leaching and acid-leaching were proposed for the dephosphorization of Changde iron ore, which contains an average of 1.12% for phosphorus content. Sodium hydroxide, sulfuriced, hydrochloric and nitric acids wer...Alkali-leaching and acid-leaching were proposed for the dephosphorization of Changde iron ore, which contains an average of 1.12% for phosphorus content. Sodium hydroxide, sulfuriced, hydrochloric and nitric acids were used for the preparation of leach solutions. The results show that phosphorus occurring as apatite phase could be removed by alkali-leaching, but those occurring in the iron phase could not. Sulfuric acid is the most effective among the three kinds of acid. 91.61% phosphorus removal was attained with 1% sulfuric acid after leaching for 20 rain at room temperature. Iron loss during acid-leaching can be negligible, which was less than 0.25%.The pH value of solution after leaching with1% sulfuric acid was about 0.86, which means acid would not be exhausted during the process and it could be recycled, and the recycle of sulfuric acid solution would make the dephosphorization process more economical.展开更多
The utilization of coal derived pyrite by electrolysis was studied. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe 3+ and SO 2- 4, and the no pollutant is drained off. In this paper, the in...The utilization of coal derived pyrite by electrolysis was studied. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe 3+ and SO 2- 4, and the no pollutant is drained off. In this paper, the influence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increases with the rise of potential, time, temperature, acidity and the concentration of additive agent, but decreases with the rise of concentration of pyrite. At the certain conditions (at the potential of 3 0 V, temperature of 298 K, time of 12 h, the concentration of MnSO 4 of 6%, concentration of pyrite of 4%, and concentration of acid of 10%), Cr is high to 93%. In the same time, the mechanism of electrolysis of pyrite was provided. The electrolysis of pyrite is actually the recycle of Mn ion between anodic surface and pyrite. At last, the production of FeSO 4·7H 2O through electrolysis of pyrite was introduced.展开更多
文摘The kinetics of Fe3O4 formation by air oxidation of slightly acidic suspension of Fe（OH）2 was studied. The effects of initial concentration of Fe（Ⅱ）, temperature, partial pressure of oxygen, air flow rate and stirring rate on the oxidation rate were investigated. The results show that Fe3O4 formation is composed of two-step reaction, the first step is the formation of Fe（OH）+2 by oxidation of Fe（OH）+ complex ions, the second step is the formation of magnetite by dehydration and deprotonation of Fe（OH）+ and Fe（OH）+2. The oxidation reaction is zero-order with respect to the concentration of Fe（Ⅱ） and around 0.5-order with respect to partial pressure of oxygen, and oxygen transfer process is rate-limiting step of oxidation reaction with apparent activation energy of 2.74 kJ·mol-1.
基金Project (50321402) supported by the National Natural Science Foundation of China project(2004CB619204) supported by Major State Basic Research Development Program of China
文摘Alkali-leaching and acid-leaching were proposed for the dephosphorization of Changde iron ore, which contains an average of 1.12% for phosphorus content. Sodium hydroxide, sulfuriced, hydrochloric and nitric acids were used for the preparation of leach solutions. The results show that phosphorus occurring as apatite phase could be removed by alkali-leaching, but those occurring in the iron phase could not. Sulfuric acid is the most effective among the three kinds of acid. 91.61% phosphorus removal was attained with 1% sulfuric acid after leaching for 20 rain at room temperature. Iron loss during acid-leaching can be negligible, which was less than 0.25%.The pH value of solution after leaching with1% sulfuric acid was about 0.86, which means acid would not be exhausted during the process and it could be recycled, and the recycle of sulfuric acid solution would make the dephosphorization process more economical.
文摘The utilization of coal derived pyrite by electrolysis was studied. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe 3+ and SO 2- 4, and the no pollutant is drained off. In this paper, the influence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increases with the rise of potential, time, temperature, acidity and the concentration of additive agent, but decreases with the rise of concentration of pyrite. At the certain conditions (at the potential of 3 0 V, temperature of 298 K, time of 12 h, the concentration of MnSO 4 of 6%, concentration of pyrite of 4%, and concentration of acid of 10%), Cr is high to 93%. In the same time, the mechanism of electrolysis of pyrite was provided. The electrolysis of pyrite is actually the recycle of Mn ion between anodic surface and pyrite. At last, the production of FeSO 4·7H 2O through electrolysis of pyrite was introduced.
