Understanding the reactions taking place in the hematite-oxalic acid system is important in order to clean iron oxides from filters and to remove iron from mineral concentrates. Previous studies reported the formation of an unwanted solid phase during this process. The objective of the current work, therefore, was to visualize and rationalize the iron dissolution steps taking place in the hematite–oxalic acid reaction by combining density functional theory (DFT) calculations and experimental data. The results of DFT calculations indicated that a precipitate was formed in this reaction; XRD analysis of the solid phase after the dissolution experiment revealed the formation of humboldtine as the precipitate. The attachment of oxalate on the hematite surface and the reduction of Fe(III) to Fe(II) were key steps for humboldtine formation. Both simulations and the experimental results showed that greater oxalic acid concentrations yielded more precipitate, suggesting a simple and novel route to synthesize humboldtine, a material which is relevant to the demand for clean energy.

了解赤铁矿-草酸系统中发生的反应对于从过滤器中清除氧化铁和从矿物浓缩物中去除铁非常重要。先前的研究报告了在此过程中形成了不需要的固相。因此，当前工作的目标是通过结合密度泛函理论 (DFT) 计算和实验数据，使赤铁矿-草酸反应中发生的铁溶解步骤可视化和合理化。DFT计算结果表明该反应有沉淀生成；溶解实验后固相的XRD分析表明形成了作为沉淀物的洪堡汀。草酸盐在赤铁矿表面的附着和 Fe(III) 还原为 Fe(II) 是形成洪堡石的关键步骤。