超细氧化铁粉低温还原热力学研究

研究低温还原超细氧化铁粉的还原热力学。用高能球磨法获得的超细氧化铁粉,在280～400℃的温度范围内用氢气还原。对还原后的粉末进行氧含量测定并计算氧化铁粉末的还原率,研究氧化铁粉粒度、还原温度和还原时间等参数对还原率的影响。从热力学的角度,计算不同温度下的反应自由能,分析和求证400℃以下低温氢气还原氧化铁的可行性。研究结果表明Fe2O3向Fe3O4还原反应的自由能在标准状态下为负值,因此还原反应有很大的自发驱动力,反应很容易进行;而Fe3O4向Fe的还原反应的自由能为正值,说明在标准状态下不能进行,要通过调节还原气体的分压比才能使还原反应进行,因此Fe3O4向Fe的还原反应是制约氧化铁粉还原的主要环节,它与非平衡状态下的温度、气体压力和反应物的状态存在紧密的联系。超细氧化铁粉处于非常高的能量状态,可以促使Fe3O4向Fe的还原反应在400℃以下的低还原温度下得以进行。

微纳米氧化铁粉低温还原特性的研究

研究了低温还原微纳米氧化铁粉的还原特性与机理。用高能球磨法获得的微纳米氧化铁粉在280～400℃内用氢气还原,并测定还原后粉末中氧、计算氧化铁粉末的还原率,通过扫描电子显微镜来观察还原铁粉的形貌;找出了氧化铁粒度、还原温度和还原时间等参数对氧化铁还原率、铁粉粒度和粒度分布、铁粉形貌等的影响。从动力学的角度,探讨了粉末细化对低温氢气还原氧化铁活化能的影响。研究结果指出,微纳米氧化铁粉的还原反应遵循吸附自动催化理论,反应动力学遵循界面化学反应理论,研究获得了反应所对应的反应机制函数和相应的动力学方程。

温度对氢气还原氧化铁影响及电化学性能研究

采用纯的氧化铁进行直接还原的实验研究,利用H2作为还原气体在高温管式炉中进行焙烧还原.结果表明,随着反应时间的增加,氧化铁块还原率相应的增大.反应温度的不同,氧化铁块还原速率及电导率也相应的不同.600~900℃下经过一定时间的氢还原,还原产物的还原速率随温度的增加而增加,均可达到95%以上.通过交流阻抗法对还原产物的电导率的测试,得到了还原产物的电导率随时间和还原度的变化曲线.随着温度及时间的不同,电导率也相应变化,电导率的不同,可间接反映还原过程中产生了导电性不同的物质.

通过热力学多因素耦合控制氧化铁碳热还原顺序

鉴于实现氧化铁按Fe2O3→Fe3O4→Fe顺序碳热还原的重要实际意义,提出了将碳储能、总压和惰气分压这几个热力学因素进行耦合的新思想,并导出了使这些热力学因素得以耦合的定量关系式。此外,从节能的角度出发,还研究了如何在使上述热力学因素满足耦合定量关系式的同时尽量降低碳储能。结果表明,在惰气分压(或总压)一定的前提下,通过在一定范围内调节总压(或惰气分压),可使所需碳储能得以降低,甚至可降至零。

一氧化碳还原氧化铁实验的一体化设计

在分析一氧化碳还原氧化铁反应原理的基础上,针对实验过程中存在的问题,将一氧化碳的制备、一氧化碳与氧化铁的反应、产物的检验和尾气的处理进行一体化设计,使多个反应置于同一个封闭体系中进行;同时改进热源装置,优化生成物--铁的检验方法,利用万用瓶并设置安全线排除爆炸风险等,大大提高了实验的成功率和安全性.

应用新技术研究“一氧化碳还原氧化铁”的产物

运用高校精密的检测仪器,从实践的角度,分别测定了用酒精灯、带网罩酒精灯和酒精喷灯加热下“CO还原Fe2O3”的固体产物成分及各成分的质量比.此研究过程,对培养学生的质疑精神和创新能力具有重要而深远的意义.

一氧化碳还原氧化铁实验的改进

针对教材中一氧化碳还原氧化铁实验的不足之处,利用W形管设计新的实验装置,提高了实验的成功率、安全性和可操作性。新装置不仅具有试剂耗量少、环保、一体化等优点,而且还可检验、收集尾气,以及改进了产物铁的检验方法。此外,W形管还可应用于初中其他系列经典实验的改进。

CO还原氧化铁实验装置的改进

针对教材实验存在的一些问题,组织学生兴趣小组进行一氧化碳还原氧化铁实验装置的改进探索,有助于学生加深了解一氧化碳的制取、验纯、干燥、收集及排出方法等知识。通过改进可以直观判断装置中的空气是否排尽,并对实验尾气进行检验和回收。改进后的实验药品用量少、效果好、安全性高,既环保又节能,并推广为学生分组实验。

一氧化碳与氧化铁反应装置的新设计

针对教材中一氧化碳与氧化铁反应实验装置的不足之处,在相关文献评析的基础上,利用W形管的特点,设计了一氧化碳与氧化铁反应的实验新装置。用新装置进行实验具有微型、环保、视觉效果好、有效控温、一体化及易推广等优点。另外,W形管还可延伸应用到初中化学的其他实验中。

鱼雷罐车中氧化铁供料速度和铁水温度对脱磷速率的影响

为了提高脱磷率，本文在实验室试验和工业生产试验中研究了氧化铁还原行为以及氧化铁供料速度和铁水温度对脱磷速率的影响，结果总结如下： （1）当氧化铁供料速度为400kg／min，石灰供料速度为一常数时，61％的氧化铁在瞬时反应区被还原，11％的氧化铁在顶渣有效反应区通过固定反应发生还原，剩余没有被还原的部分仍以氧化铁的形式残留在鱼雷罐车中的死区。 （2）瞬时反应区氧化铁还原速率取决于铁水温度和氧化铁供料速度，当铁水温度从1653减少至1563K时（△90℃），氧化铁还原速率减少了40％，当氧化铁供料速度从200kg／min增加到400kg／min时，还原速率减少了20％。 （3）氧化铁还原的表观活化能估计为132KJ／mol，略低于从温度和氧在FeO—CaO—SiO2渣系中扩散系数关系得到的表观活化能。 （4）在鱼雷罐车中开发了新的铁水脱磷数学模型，考虑了铁水温度和氧化铁供料速度对供氧速率的影响。该模型结论与从鱼雷罐车得到的实际数据相吻合。

超细氧化铁低温还原工艺研究

研究了超细氧化铁低温氢气还原制取超细铁粉的工艺。用高能球磨获得的不同粒度的氧化铁粉末在氢气气氛下进行低温还原,利用氮氧分析仪测定氧含量,计算氧化铁粉末的还原率,分析各因素对还原率的影响,并进行比较分析,得出最佳的还原工艺参数为：还原温度为700℃,还原时间为60 min,氧化铁粉末平均粒度为0.8μm,氢气流量为1.0 L/min。

低温还原制取超细铁粉的研究

探索了超细氧化铁粉低温还原制取超细铁粉的研究。采用高能球磨,制得不同粒度的超细氧化铁粉末,然后,分别在不同还原温度和还原时间下,进行氢气还原。对还原后的粉末进行氧含量的测定,并计算出氧化铁粉末的还原率,对还原铁粉进行粒度和粒度分布的分析,通过扫描电子显微镜,观察还原铁粉的形貌。找出超细氧化铁粉粒度、还原温度、还原时间等参数对氧化铁粉还原率、铁粉粒度、粒度分布和铁粉形貌等的影响。由于采用了高能球磨的方式破碎粉末,显著地增加了氧化铁粉末的比表面积、表面能及提高了粉末的活性。研究结果表明,较大地降低了还原温度,即使在280℃温度下,仍然可以被氢气还原。由于还原反应是在很低的温度下进行,粉末颗粒长大的动力被极大降低,所以能够制得超细铁粉。采用0.35μm氧化铁粉,在400℃的还原温度下,可以制取到粒度小于0.4μm的超细铁粉,并且还原率接近100%。

高炉炼铁实验的新设计

对教材中一氧化碳还原氧化铁的实验进行改进。利用定制的长柄U形管、气袋以及MCH陶瓷加热棒等仪器设计高炉炼铁的新实验装置。改进后的实验采用炭粉还原氧化铁,避免了一氧化碳的制备及尾气处理,使整个实验操作简便、高效、环保及安全。

Relationship and effect of redox potential,jarosites and extracellular polymeric substances in bioleaching chalcopyrite by acidithiobacillus ferrooxidans

The changes of pH,redox potential,concentrations of soluble iron ions and Cu^2＋ with the time of bioleaching chalcopyrite concentrates by acidithiobacillus ferrooxidans were investigated under the different conditions of initial total-iron amount as well as mole ratio of Fe（III） to Fe（II） in the solutions containing synthetic extracellular polymeric substances （EPS）.When the solution potential is lower than 650 mV （vs SHE）,the inhibition of jarosites to bioleaching chalcopyrite is not vital as EPS produced by bacteria can retard the contamination through flocculating jarosites even if concentration of Fe（III） ions is up to 20 g/L but increases with increasing the concentration of Fe（III） ions;jarosites formed by bio-oxidized Fe3＋ ions are more easy to adhere to outside surface of EPS space on chalcopyrite;the EPS layer with jarosites acts as a weak diffusion barrier to further rapidly create a high redox potential of more than 650 mV by bio-oxidizing Fe^2＋ ions inside and outside EPS space into Fe^3＋ ions,resulting in a rapid deterioration of ion diffusion performance of the EPS layer to inhibit bioleaching chalcopyrite severely and irreversibly.

Conversion of ferric oxide to magnetite by hydrothermal reduction in Bayer digestion process

Digesting aluminum-bearing minerals and converting ferric oxide to magnetite simultaneously in Bayer digestion process is crucially important to deal with high-iron diasporic bauxite economically for alumina production.The reaction behaviors of hydrothermal reduction of ferric oxide in alkali solution were studied by both thermodynamic calculation and experimental investigation.The thermodynamic calculation indicates that Fe3O4 can be formed by the conversion of Fe2O3 at proper redox potentials in alkaline solution.The experimental results show that the formation ratio of Fe3O4 either through the reaction of Fe and Fe2O3 or through the reaction of Fe and H2O in alkaline aqueous solution increases remarkably with raising the temperature and alkali concentration,suggesting that Fe（OH）3- and Fe（OH）4- form by dissolving Fe and Fe2O3,respectively,in alkaline aqueous solution and further react to form Fe3O4.Moreover,aluminate ions have little influence on the hydrothermal reduction of Fe2O3 in alkaline aqueous solution,and converting iron minerals to magnetite can be realized in the Bayer digestion process of diasporic bauxite.

Reaction behavior of ferric oxide in system Fe_2O_3-SiO_2-Al_2O_3 during reductive sintering process

Pure compounds and kaolin were employed to investigate the reaction behavior of ferric oxide in thetrinarysystem Fe2O3?SiO2?Al2O3 during reductive sintering process. The thermodynamic analyses and reductive sintering experimental results show that ferrous oxide generated from the reduction of ferric oxide by carbon can react with silicon dioxide and aluminum oxide to form ferrous silicate and hercynite at 1173 K, respectively. In the trinary system Fe2O3?SiO2?Al2O3, ferrous oxide obtained from ferric oxide reduction preferentially reacts with aluminum oxide to form hercynite, and the reaction of ferrous oxide with silicon dioxide occurs only when there is surplus ferrous oxide after the exhaustion of aluminum oxide. When sintering temperature rises to 1473 K, hercynite further reacts with silicon dioxide to form mullite and ferrous oxide. Results presented in this work may throw a new light upon the separation of alumina and silica present in Al/Fe-bearing materials with low mass ratio of alumina to silica in alumina production.

Effects of mechanical activation and oxidation-reduction on hydrochloric acid leaching of Panxi ilmenite concentration

The effects of oxidation-reduction treatment and mechanical activation on the hydrochloric acid leaching performance of Panxi ilmenite concentration were investigated.The results show that both of oxidation-reduction treatment and mechanical activation significantly accelerate the extraction of Fe,Ca and Mg from Panxi ilmenite concentration;however,the CaO and MgO contents of the calcined residues obtained from oxidized-reduced ilmenite concentration are higher than the standard values required by chlorination process.The Ca and Mg in oxidized-reduced ilmenite concentration can be leached much faster after mechanical activation,yielding a synthetic rutile which meets the requirements of chlorination process containing 90.50% TiO2 and 1.37% total iron as well as combined CaO and MgO of 1.00%.The optimum oxidation and reduction conditions are as follows：oxidization at 900 ℃ in the presence of oxygen for 15 min and reduction at 750 ℃ by hydrogen for 30 min.

Fe-Mn/Al_2O_3 catalysts for low temperature selective catalytic reduction of NO with NH_3

A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.

Fe^(3+)/Fe^(2+) redox electrolyte for high-performance polyaniline/SnO_2 supercapacitors

The Fe3＋/Fe2＋ redox electrolyte for use in polyaniline/tin oxide （PANI/SnO2）supercapacitors was reported. The influences of redox electrolyte based on different Fe3＋/Fe2＋ ion pair concentrations in 1 mol/LH2SO4 solution on the pseudocapacitive behaviors of PANI/SnO2 supercapacitor were investigated. The electrochemical properties of the supercapacitor were studied by cyclic voltammetry （CV）, galvanostatic charge discharge （GCD）, and electrochemical impedance spectroscopy （EIS） techniques. It is found that the performance of the supercapacitor is the best when the Fe3＋/Fe2＋ concentrationis 0.4 mol/L and its initial specific capacitance is 1172 F/g at an applied current density of 1 A/g. The long-term cycling experiment shows good stability with the retention of initial capacitance values of 88% after 2000 galvanostatic cycles. The experimental results testify that using Fe3＋/Fe2＋ redox electrolyte has a good prospect for improving the performances of energy-storage devices.

RGO/FeOOH凝胶制备及其对铀的吸附性

三维(3D)石墨烯复合纳米材料由于具有极佳的物理化学特性而被广泛研究。本文利用Fe(II)离子还原自组装制备3D还原氧化石墨烯与羟基氧化铁(RGO/FeOOH)复合材料,并将材料应用于铀的吸附研究。结果表明,复合材料吸附容量对pH具有很强的依赖性,且当pH为5.5时吸附容量可达115 mg·g-1;在溶液中加入NaClO4并未影响材料的吸附性;研究材料吸附铀(VI)的等温线,发现材料的吸附动力学符合双Langmuir模型曲线;通过离子选择性研究发现RGO/FeOOH复合材料对铀和铅具有较好的选择性。因此,可将此材料用于放射性废水中重金属离子的去除。