Arsenic-contaminated red mud (As-RM) is a hazardous waste with limited recycling approaches. Generally, through reductive roasting and magnetic separation, RM could be transformed into Fe-rich concentrate for Fe resource recovery. However, due to the poor thermostabilization of As species, reductive roasting of As-RM would cause severe As volatilization pollution together with high As leaching risks from heated residue. Herein, a novel johnbaumite-based As thermostabilization strategy is developed for clean Fe resources recycling from As-RM. We found that in the presence of Ca(OH)₂, the As species in As-RM could be immobilized as thermostable and insoluble johnbaumite (Ca₅(AsO₄)₃OH) at 900 °C, effectively enhancing the As thermostability and insolubility. Introducing 1.5% Ca(OH)₂ into As-RM suppressed the As volatilization ratio from 60.3% to 15.7% during reductive roasting. Meanwhile, the As leaching concentration of the reduced residue was reduced to < 100 µg/L, thus satisfying the Japanese wastewater discharge standard. A concentrate with approximately 67.5% total iron grade was obtained from As-RM through this clean reductive roasting and magnetic separation. Overall, the approach introduced in this work effectively reduces the As diffusion pollution deriving from As-RM thermal reduction, which could contribute to hazardous As-RM reutilization, clean Fe resources recovery, and As pollution mitigation.

砷污染的赤泥 (As-RM) 是一种危险废物，回收方法有限。一般通过还原焙烧和磁选将RM转化为富铁精矿用于铁资源回收。然而，由于 As 物种的热稳定性差，As-RM 的还原焙烧会导致严重的 As 挥发污染以及加热残渣的高 As 浸出风险。在此，开发了一种新型的基于锌铝矿的 As 热稳定策略，用于从 As-RM 中回收清洁的 Fe 资源。_{我们发现在 Ca(OH) 2}的存在下，As-RM 中的 As 物种可以固定为热稳定且不溶的钙铝石 (Ca ₅ (AsO ₄ ) ₃OH) 在 900 °C，有效地提高了 As 的热稳定性和不溶性。在 As-RM 中引入 1.5% Ca(OH) ₂可将还原焙烧过程中的 As 挥发率从 60.3% 抑制到 15.7%。同时，还原渣的As浸出浓度降至<100 µg/L，满足日本废水排放标准。通过这种清洁的还原焙烧和磁选，从 As-RM 获得了总铁品位约为 67.5% 的精矿。总的来说，这项工作中引入的方法有效地减少了 As-RM 热还原产生的 As 扩散污染，这可能有助于危险的 As-RM 再利用、清洁铁资源回收和 As 污染缓解。