Upcycling Mill Scale and Aluminum Dross for Sustainable Materials Processing: Synthesis of Hercynite via Fe2O3-Al2O3-C Combustion

This study investigates the potential of utilizing industrial by-products—mill scale (MS) and aluminum dross (AD)—as sources of Fe2O3 and Al2O3, respectively, for hercynite (FeAl2O4) production. Through combustion of MS-AD-graphite systems at 1550 °C under air atmosphere, hercynite-based refractory materials were synthesized. Results confirm the viability of this upcycling approach for hercynite synthesis. During the formation of hercynite, the development of a dendritic structure can be observed, which subsequently fuses into a grain shape. XRD phase analysis using the Rietveld method revealed that the major components of the product with a C/O ratio of 1 were 85.11% FeAl2O4, 10.99% Al2O3, and 3.9% C. For the product with a C/O ratio of 2, the composition was 82.4% FeAl2O4, 13.0% Al2O3, and 4.6% C. The combustion of raw pellets with a C/O ratio of 1 at 1550 °C for 1 h in a normal air atmosphere is economically viable for producing hercynite, yielding 85.11 wt%. This approach presents a sustainable and eco-friendly alternative to using commercial raw materials, potentially eliminating the need for virgin alumina and iron ore. By repurposing waste materials from the steel and aluminum industries, this study contributes to the circular economy and aligns with the goal of zero waste.