Comprehensive Characterization of Multiphase Components in Magnesium Slag by Silicothermic Process

This study investigates the chemical composition, particle size distribution, magnetic components, and alkaline sources of magnesium slag to enhance its utilization as a solid waste. Comprehensive characterization was achieved through multiple techniques, including graded sieving (16–150 mesh), magnetic separation, XRD, SEM/EDS, and EDTA titration, which systematically revealed the physicochemical properties of the slag. The sieving results indicate that β-Ca 2 SiO 4 is the dominant phase in the fraction larger than 1180 μm (11.55%), while γ-Ca 2 SiO 4 predominates in the fraction smaller than 180 μm (56.53%). The white particles in the magnesium slag originate from partially reacted dolime, whereas the black particles arise from incompletely reduced zones within the pellets. Magnetic separation analysis shows that coarse particles (> 1 mm) in the magnetic fraction mainly come from high-temperature oxidized spalls from the reduction reactor, while fine powders (< 200 μm) consist primarily of ferrosilicon (Fe x Si y ). Titration results demonstrate that the free calcium oxide (f-CaO) content accounts for 6.75 ± 0.1% by mass and serves as the primary contributor to the slag’s alkalinity. Through qualitative and quantitative analysis, this study elucidates the relationship between the physicochemical properties of magnesium slag and its resource utilization, providing key scientific evidence and practical guidance for high-value applications.