Thermally assisted magnetic separation and characterization studies of a low-grade hematite ore

Abstract

Alternative beneficiation strategies are now being adopted to upgrade the iron values in low-grade iron ores that do not respond to physical beneficiation owing to their complex texture and poor liberation pattern. Thermal treatment prior to beneficiation, in order to enhance the liberation and downstream beneficiation operation, is one such method. In this context, a low-grade hematite ore with 56.5% Fe has been subjected to heat treatment followed by grinding and wet high intensity magnetic separation (WHIMS). The magnetic separation results indicate that an enhancement in yield by around 15–20% by weight is possible when the ore is heat-treated at 500–800 °C. The sink and float studies indicate a negligible improvement in mineral liberation arising due to the thermal treatment while the Frantz isodynamic separation results suggest a remarkable increase in the mass magnetic susceptibility value from 14.4 × 10−9 to 30 × 10−9 SI units for the treatment at 500 °C. Detailed mineralogical characterization studies of the heat-treated samples using optical microscopy and Electron Probe Micro Analysis (EPMA) show the development of crystallinity as well as formation of both intergranular and transgranular cracks within the ore thereby facilitating the separation process.