Upcycling Mill Scale: Ferrofluids Fabrication from Steelmaking Waste

초록

Mill scale, a primary byproduct of the steel industry, presents recycling challenges due to the inefficiencies and complexities of conventional methods of reducing mill scale, which demands a high energy input of around 850-1200 degrees C and additional reductants. This study introduces two feasible and cost-effective recycling approaches via hydrometallurgy and high-energy ball milling, which can respectively be considered as bottom-up and top-down. Despite the heterogeneous composition of mill scale, both approaches allow for efficient synthesis of magnetically-active magnetite nanoparticles. An array of techniques was used, including X-ray diffraction, electron microscopy, and atom probe tomography to reveal the evolution of the phase fractions. In combination with magnetic measurements, this study rationalizes and optimizes the ferromagnetic properties of the particles. Finally, the results demonstrate the upcycling of these wastes into stable ferrofluid. Both fabrication routes yield ferrofluids demonstrating distinct Rosensweig instability under an applied magnetic field flux of 1.45 T. This integrated upcycling strategy not only valorizes steelmaking waste but also enables scalable production of ferrofluids, expanding potential applications in magnetic technologies.

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