Abstract: To address the challenges in recycling red mud, a massive hazardous solid waste from the alumina industry, this work proposes an innovative and clean hybrid process combining hydrogen reduction and electric arc smelting for the efficient recovery of iron. Using Bayer-process red mud as the raw material, the effects of reduction temperature (ranging from 500 to 1100℃) on the phase transformation of iron oxides and the metallization rate under a hydrogen atmosphere were systematically investigated. The reduction intermediates and final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and thermogravimetric-differential thermal analysis (TG-DSC). The results indicated that the hydrogen reduction of Fe2O3 in red mud followed a stepwise pathway: Fe2O3→Fe3O4→Fe. The reduction of Fe3O4 to metallic iron was identified as the dominant endothermic reaction, with its peak reaction rate occurring at approximately 760℃. Reduction temperature was found to be the key factor governing the metallization rate. After reduction at 1100℃ for 2 hours, the metallic iron content reached 42.9wt%, corresponding to a metallization rate of 91.5%. Microstructural observations revealed that metallic iron particles underwent significant sintering and coalescence at 1100℃. Surface and grain boundary diffusion led to the formation of a continuous and porous iron network, which represented a typical characteristic of solid-state sintering at the intermediate stage. This interconnected iron structure greatly shortened the diffusion distance required for the coalescence of iron droplets in the subsequent melting step. Electric arc smelting of the reduced product at 1800℃ successfully yielded a remelted iron product with a purity of up to 98.000wt%, demonstrating efficient iron-slag separation. This work provides a green and efficient technical route for large-scale iron recovery from red mud, with potential value for industrial solid waste recycling and low-carbon metallurgy.

Key words: red mud, hydrogen metallurgy, iron recovery, reduction mechanism, electric arc melting separation

摘要： 为实现赤泥中铁资源的高效清洁回收，针对氧化铝工业产生的大宗危险固体废弃物——赤泥所面临的资源化难题，本研究提出了一种“氢气还原-电弧熔分”相结合的新型处理工艺。以拜耳法赤泥为原料，系统研究了在氢气气氛下，还原温度(500~1100℃)对铁氧化物相变行为及金属化率的影响，并借助X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱分析(EDS)和热重-差热分析(TG-DSC)对还原产物进行表征。结果表明，赤泥中Fe2O3的氢气还原路径遵循Fe2O3→Fe3O4→Fe的逐步转化过程，其中Fe3O4还原为金属铁为主控吸热反应，其反应速率峰值出现在约760℃。还原温度是决定金属化率的关键因素，在1100℃下还原2 h后，金属铁含量达到42.9wt%，对应金属化率为91.5%。微观结构分析表明，在1100℃下金属铁颗粒经表面扩散与晶界扩散发生显著烧结，形成连续多孔的铁相网络，属于固态烧结中期的典型特征。该相互连接的铁结构极大缩短了后续熔分过程中铁液滴聚合所需的扩散距离。通过对还原产物在1800℃进行电弧熔分，成功实现了铁与渣的高效分离，并获得铁纯度高达98.000wt%的重熔铁产品。本研究为赤泥的大规模资源化利用及低碳冶金提供了一条绿色、高效的新途径。

关键词: 赤泥, 氢冶金, 铁回收, 还原机理, 电弧熔分