Roasting-Assisted Beneficiation of Magnetite–Apatite Ores: Phase Transformations, Phosphorus Partition, And Selective Recovery

Magnetite–apatite ores constitute important resources of both iron and phosphorus but remain challenging to beneficiate because phosphorus-bearing phases commonly occur as finely disseminated apatite, interstitial aggregates, hydrothermal overgrowths, and complex grain-boundary intergrowths within iron oxide matrices. Roasting-assisted beneficiation has emerged as a promising strategy for modifying iron mineralogy, enhancing magnetic susceptibility, improving mineral liberation, and controlling phosphorus distribution. However, existing studies remain dispersed across the following routes: oxidizing roasting, magnetization roasting, selective reduction, additive-assisted roasting, flotation, leaching, dry beneficiation, and smelting. This critical review examines the interactions among ore texture, oxygen potential, roasting temperature, residence time, degree of reduction, phosphorus migration, and beneficiation performance. Particular attention is given to moderate-temperature reduction (approximately 650–800 °C), which frequently provides a more favorable balance between iron recovery and phosphorus rejection than highly reducing metallization-oriented conditions. Thermodynamic and kinetic aspects of the hematite–magnetite–wüstite–metallic iron transformation are discussed together with phosphorus redistribution mechanisms, including apatite preservation, interfacial diffusion, secondary phosphate formation, metallic iron contamination, slag partitioning, and leaching behavior. Comparative analysis indicates that maximum metallization does not necessarily yield optimal beneficiation outcomes, as excessive reduction often promotes the incorporation of phosphorus into metallic iron. Current industrial implementation remains limited by thermal heterogeneity, atmosphere control, energy consumption, and insufficient pilot-scale validation. Future advances require integrated thermodynamic–microstructural modeling, predictive approaches to phosphorus partitioning, and energy-efficient roasting flowsheets that simultaneously enhance iron recovery and phosphorus management.