铝酸亚铁非等温氧化动力学及机理研究

铝酸亚铁的氧化分解对其后续拜耳法提取氧化铝具有重要意义。对铝酸亚铁的非等温氧化动力学进行研究,并借助XRD和XPS分析其氧化分解机理。结果表明:铝酸亚铁在650～900 K和900～1100 K氧化时分别受化学反应控制和内扩散控制,反应活化能分别为59.36 kJ/mol和20.69 kJ/mol。铝酸亚铁首先氧化分解为磁铁矿和γ-氧化铝,温度升高促使磁铁矿进一步氧化为γ-氧化铁并最终转变为稳定的α-氧化铁,而γ-氧化铝则转变为α-氧化铝。铝酸亚铁中的铁氧化物优先于氧化铝往颗粒表面迁移,从而对颗粒内部铝酸亚铁的氧化分解起到阻碍作用。该研究为降温过程中同步实现铝酸亚铁的氧化分解奠定理论基础。 

Study on Kinetics and Mechanism of Non-isothermal Oxidation of Hercynite

The decomposition of hercynite through oxidation roasting is significant for the subsequent alumina extraction by Bayer process. In this work, the non-isothermal oxidation kinetics of hercynite was studied and the oxidation mechanism was investigated through the analysis methods of X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that hercynite oxidation at 650～900 K and 900～1100 K was respectively controlled by chemical reaction and internal diffusion, and the corresponding reaction activation energies were 59.36 kJ/mol and 20.69 kJ/mol. Hercynite was firstly oxidized into Fe₃O₄ and γ-Al₂O₃, elevated temperature promoted the oxidation of Fe₃O₄ into γ-Fe₂O₃ and further into α-Fe₂O₃, meanwhile γ-Al₂O₃ was transformed into α-Al₂O₃. The migration of iron oxides to particle surface was prior to that of alumina in hercynite, thereby hindering the oxidation of particle interior. This study lays the foundation for the simultaneous oxidation of hercynite during cooling process.