Efficient Production of Ferrous Sulfate from Steel Mill Scale Waste

Waste utilized for material development is increasingly under scrutiny in the pursuit of sustainability. Particularly, steel mill scale, a solid waste generated in the metallurgical industry through the oxidation of steel dowels, is a focus of study. In this investigation, X-ray diffraction (XRD) analysis identified wustite, magnetite, and hematite as crystalline phases, while X-ray fluorescence analysis revealed that iron oxides comprised 97% of the weight, with approximately 67% being elemental iron. Due to this composition, mill scale served as a precursor for ferrous sulfate heptahydrate (FeSO·7HO) via a process involving sulfuric acid aqueous solution leaching, ethanol filtration, and a final crystallization step. A factorial experimental design was employed to optimize the production of FeSO·7HO, assessing the influence of each variable parameter (reagents) and their interactions. Finally, the potential of mill scale in the production of FeSO·7HO, process efficiency, and quality of the resulting material were evaluated. Compared to a sample of commercial FeSO·7HO, the obtained material exhibited higher peak intensity in XRD, increased purity (reaching 99.83%), and similar thermal behavior in both differential thermal analysis and thermogravimetry. The yield of the FeSO·7HO production process from mill scale exceeded 70%. Graphical Abstract: (Figure presented.).