An alternative and clean utilisation of refractory high-phosphorus oolitic hematite: P for crop fertiliser and Fe for ferrite ceramic

Abstract

High-P oolitic hematite is recognised as one of the most refractory mineral resources because of the special oolitic structure. Conventional selective reduction roasting is characterised by high energy consumption and large greenhouse gas emissions. In this study, a clean utilisation of refractory high-P oolitic hematite via phase reconstruction was proposed to make the P for crop fertiliser and Fe for ferrite ceramic. Phase reconstruction indicated that the oolitic and finely disseminated structure was dramatically changed by the oxidisation roasting with Mn ore at 1100°C–1250 °C. After reconstruction, 85 wt%–90 wt% Fe and Mn were concentrated in the magnetic ferrite phase whilst 90 wt%–100 wt% P, K, Ca, Si, Mg, and Al impurities were enriched in the nonmagnetic P-bearing tailings. After separation, the separated Mn ferrite and P-bearing tailings after activation could be used as ingredients in ceramic and fertiliser production. The as-purified ferrite showed good electromagnetism performance whilst almost all nutrients in the P-bearing tailings were activated via high-temperature melting and water quenching and can thus be readily absorbed by the crop roots. Moreover, the phase reconstruction mechanism and feasible granular fertiliser preparation from P-bearing tailings were discussed. All elements in the high-P oolitic hematite were utilised without emission of greenhouse gases.