Selective inhibitory effect on flotation caused by microwave irradiation on Myanmar black ore

In these days, base metal demand of the world are increasing, however, grade of ore has been decreased. Therefore, the mineral processing of low grade ore and refractory ore are required to be developed more and more. Microwave irradiation has attracted attention as a method to promote liberation of ores and bring selective reaction such as surface oxidation. This research is studied flotation behavior after microwave irradiation to black ore. It has been confirmed that pyrite (FeS₂) and galena (PbS) are selectively inhibited by irradiating microwave to the Myanmar black ore in bulk flotation. It is suggested that the two minerals were selectively oxidized by microwaves and inhibited in flotation process. It was confirmed that not pyrite but chalcopyrite and galena have high reactivity to microwaves and generate heat above 600 °C. Mineral specimens of pyrite and galena were irradiated with microwave in prescribed conditions, and the change of the surface morphology was confirmed by Xray diffraction (XRD), Xray Photoelectron Spectroscopy (XPS) and Xray absorption fine structure (XAFS) analysis. From the measurement results, the presence of lead sulfite (PbSO₄) was confirmed from the galena irradiated with microwave. Therefore, oxidation reaction occurred by irradiation with microwave, and galena changed to lead sulfite, so it was inhibited by flotation. On the other hand, oxidation was not confirmed in pyrite. It is suggested that it was oxidized by heat from the other high reactive minerals like chalcopyrite or galena.