Hydrogen-based phase transformation and separation of high iron and low manganese ores

Ferromanganese ore is an important raw material for the beneficiation and smelting of manganese and iron. The efficient separation of manganese and iron is challenging due to the isomorphism and dispersion of fine particles. The process of hydrogen-based mineral phase transformation and magnetic separation was developed, and the effects of roasting temperature, roasting time, reduction gas concentration, and total gas flow on the separation of ferromanganese and the rate of conversion of divalent manganese were investigated. Iron concentrate with 55.24% iron grade and 91.07% recovery and manganese concentrate with 34.80% manganese grade, 77.11% recovery, and 88.79% conversion of Mn²⁺ were obtained under the roasting temperature of 660 ℃, roasting duration of 30 min, volume ratio of carbon monoxide to hydrogen of 1∶3, reduction gas volume fraction of 60%, total gas flow rate of 500 mL·min^–1, and magnetic field intensity of 8.51 × 10⁴ A·m^–1. Chemical composition analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope-energy dispersion spectra (SEM-EDS) analysis confirmed the effective separation of manganese and iron minerals. The raw ore was mainly composed of limonite, pyrolusite, and quartz. Most weakly magnetic iron ores were transformed into strong magnetic iron minerals after suspension magnetization roasting, whereas pyrolusite was transformed into manganosite after reduction roasting. The primary iron mineral in the iron concentrate was magnetite, containing a small amount of metallic iron. The main manganese mineral in manganese concentrate was manganosite, and the gangue mineral was quartz. Due to the remarkable differences in the magnetic properties of the iron and manganese minerals, efficient separation was achieved through magnetic means. The content of divalent manganese in the manganese concentrate was increased considerably by controlling the process conditions during the hydrogen-based mineral phase transformation, enabling the manganese mineral to be extracted easily by leaching. Thus, the goal of full component utilization of the raw ore and tailless beneficiation was achieved. This novel approach for the clean and efficient utilization of high iron and low manganese ores holds promise for the conversion and synchronous separation of the iron and manganese minerals, achieving the goal of “source reduction, efficient conversion, and precise recovery,” and achieving excellent economic and social benefits.