Effect of microwave treatment on the flotation and magnetic separation properties of pyrite, chalcopyrite, galena and sphalerite

The effects of microwave treatment on the floatabilities and magnetic susceptibilities of some sulfide minerals, namely, pyrite, chalcopyrite, galena and sphalerite, were studied. Pure mineral samples were prepared in -425+212-μm, -212+106-μm and -106+38-μm size fractions. Microflotation and magnetic separation tests were curried out on the samples after microwave treatment at 600, 950 and 1,300 Watts for 5, 20, 60, 90, 120 and 240 seconds. The maximum temperature values of the samples were measured during the microwave treatment, and possible alterations on the mineral surfaces were determined by X-ray diffraction (XRD) analysis. The effects of microwave treatment are discussed based on the result of microflotation and magnetic separation tests. The results revealed that pyrite, chalcopyrite and galena were heated very quickly and that their surface temperatures reached -700 to 900°C while the temperature of sphalerite reached only ≈130°C. The float ability of pyrite, chalcopyrite and galena were decreased when microwave energy and the duration of treatment were increased, owing to oxidation of the mineral surfaces caused by relatively high temperature. As expected, there was no change in the float ability of sphalerite. The magnetic properties of pyrite and chalcopyrite were improved by the increase in microwave energy and the duration of treatment to such an extent that 90% of the feed separated as magnetic product. But no change was observed in the magnetic properties of galena and sphalerite.